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ABSTRACT

The classical voltmeter-ammeter-wattmeter method, usingtraditional instruments and instrument transformers, is reviewedand its shortcomings outlined. This is followed by an outline of anelectronic metering system capable of accurately measuring thecharacteristics and power loss of power transformers over a widerange of current and voltage. Appended to the paper aredescriptions and specifications for a polyphase metering systemoperating over the range of 0-2,500 amperes and 0-138 kV.

INTRODUCTION

The method of power transformer characteristics and loss

measurement to be described here is conventional and should bewell known and understood. It is the classical voltmeter-ammeter- wattmeter method. The methodology for the test equipment,however, is very up to date and capable of high accuracy over awide range of voltage, current, power factor and frequency.

THE REQUIREMENTS

The requirements of the TLMS is to accurately measure thecharacteristics of power and distribution transformers, primarily itsimpedance and power loss. Such characterisitics are measuredduring the final testing of the transformer and consist of short circuittests to determine the impedance and 'copper losses', and opencircuit tests to determine the 'iron losses'. The test sample may be asingle-phase transformer, or a three-phase transformer connected'star' or 'delta' requiring the appropriate connections.

It is interesting to note that international or nation specificationsdealing with transformers do not specify the measurementaccuracy for such tests, but some do specify the connections thatmust be used. Thus for example, the three-wattmeter method ofpower measurement is specified for a three-phase test sample,regardless if the sample is 'star' or 'delta' connected. Themeasurements system must be also capable of accuratelymeasuring power at low power factors, as some of themeasurements may involve power factors as low as 1%, or evenlower.

As such a system must be periodically calibrated, it should offer

features that will allow such calibrations to be carried outconveniently and with ease. One such calibration method orsystem is described in the NBS Technical Note 1204, "Calibrationof Test Systems for Measuring Power Losses of Transformers". Thissystem outlines recognised procedures and equipment that can beeffectively used to calibrate transformer loss measuring systems.

THE CHOICE OF METHOD.

The test methods available for transformer loss measuring systems(TLMS) are limited. One of these is the voltmeter-ammeter- wattmeter method, the other is the bridge method. For typicalpower transformers that involve power factors in the range of0.3 . . . 0.1 for core loss, and 0.1 . . . 0.01 for copper loss, the VAWwould be the choice. The bridge method would be the choice for

measuring very low loss transformers or shunt reactors. Suchspecimen may have power factors as low as 0.3% and theirmeasurements require special considerations.

THE VOLTMETER - AMMETER - WATTMETER METHOD

This method is probably the oldest and most widely used methodused to measure the characteristics of electrical equipmentincluding transformers. Two possible connections for the methodare shown in Figure 1 and Figure 2.

Figure 1. Voltmeter-Ammeter-Wattmeter Connection.

Figure 2. Voltmeter-Ammeter-Wattmeter Alternate

Connection.

When used on equipment with linear characteristics, and whentesting with a sinusoidal source of low impedance, only thevoltage, current, and power need be measured. As this conditioncan not be met under normal operating conditions, the test methodtypically must consists of measuring at least four quantities. Theseare the rms voltage, the flux voltage, the rms current and power.Additional quantities of interest are peak voltage and peak current.Both, rms and flux voltages are measured so that the magnitude ofharmonic distortion in the test voltage can be appreciated andapplicable corrections made. Knowledge of the peak current andflux voltage during open circuit tests allows the manufacturer to

determine the exact operating point of the core material.Traditionally, the rms voltage and current was measured using eithera dynamometer or a moving iron instrument with their characteristicsquare-law scales. The flux voltage is measured with a moving-coil-permanent magnet movement associated with a rectifying circuit.The wattmeter for power measurement typically used adynamometer movement. The peak values were traditionally notmeasured due to the lack of peak responding instruments.

The limitations or drawbacks of the voltmeter-ammeter-wattmetermethod using traditional instruments are many. These included inthe dynamic limitations of the ammeters and voltmeters, due totheir square-law scale. This necessitates the use of many ratios ofinstrument voltage and instrument current transformers. It would

not be uncommon to have available more than ten different ratioson the current transformers, and ten different voltage transformersto cover current up to 5000 amperes and voltage up to 120 kV. Its

by Oleh W. Iwanusiw, P. Eng.Consultant, ELTEL Industries, Bengaluru

THE MEASUREMENT OF TRANSFORMER

CHARACTERISTICS AND POWER LOSS

JANUARY-FEBRUARY 2011ITMA JOURNAL


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operation was cumbersome - as it necessitated a shut-down of thetest circuit and only then changes of ratios could be made on multi-ratio transformers. Often one instrument transformer would needto be replaced by another.

The measurement of transformer core loss presented fewlimitations. The power factor of this test circuit being in the range of0.3 to 0.1 allowed the use of conventional, unity power factor, orthe low power factor (10 - 20%) wattmeter. The most seriouslimitations of this test circuit was the availability of a wattmeter witha multiplicity of current and voltage ranges that could be changedunder load.

The measurement of copper losses, on the other hand, presentedmany problems. This would be especially true when testing largepower transformers where the test circuit power factor may havebeen 0.01 or even lower. This would result in an indication of only afew divisions even on most sensitive (low power factor)instruments.

To be accurate, the test results had to be corrected for the errors ofthe instruments and instrument transformers. The voltmeters andammeters were corrected for the scale errors of the instruments as

well as for the ratio errors (RE) of their associated instrumenttransformer. The correction of the wattmeter was much morecomplex and needed to be corrected for:

* scale error of wattmeter,

* phase error of wattmeter,

* ratio error of current transformer,

* phase error of current transformer,

* ratio error of voltage transformer,

* phase error of voltage transformer.

The corrections due to the phase angle errors (PE) are moreimportant than those due to the ratio errors at the low power factortypically encountered here. To complicate the situation the ratio

and phase errors of the instrument transformers are load current ortest voltage sensitive, and have to be accurately determined fromtables or graphs. The correction could be relatively large ifinstrument transformers of commercial, instead of precision,accuracy class were used in the measurement. Even if instrumentcurrent transformers of 0.1 Class were used, the total phase anglecorrection could have been as much as 15 minutes. This couldresult in an error of up to 45% of measured power at 0.01 powerfactor. One can see that the scale errors of a 0.2% accuracy classwattmeter are rather small when compared to the possible phaseangle errors of instrument transformers in low power factor circuits.

To be able to make accurate power measurement at low powerfactors one must have available accurate and clibrated instrumentsand instrument transformers. A phase angle uncertainty of only 1minute on the CT, PT and wattmeter may result in a total error of upto 9% when measuring power at, a power factor of 0.01.

In addition to the errors of the instruments and instrumenttransformers, one must examine and correct for the power losses inthe measuring circuit and measuring equipment. This can bereadily seen from Figure 1, where the power reading should becorrected for the I2R losses in the current transformer and thecurrent circuit of the instruments. The losses measured in Figure 2should be corrected for the V2/R losses in the voltage circuit of theinstruments. These corrections, although appear small and trivial,can amount to a percent or two in very low power factor testcircuits.

The circuit shown in Figure 2 is usually preferred because thevoltage measurement can be performed directly at the terminals ofthe test specimen eliminating all lead-drop corrections from the

measurement. The lead-drop errors are usually larger than thelosses in the voltage or current transformers discussed above.

In summary, one must conclude that accurate measurement oflosses using conventional instruments and instrument transformersrequire numerous corrections. Many of these corrections arevoltage, current, and burden sensitive and therefore vary from set-up to set-up. Needless to say, the instruments and the instrumenttransformers need to be calibrated on all ranges and possibleburdens so that extensive tables of corrections can be prepared.

THE MODERN VOLTMETER-AMMETER-WATTMETER METHOD.

With the advent of solid state and digital technologies and ajudicious choice of current and voltage sensors, it is possible toimprove the voltmeter-ammeter-wattmeter method substantially.By using digital electronics rather than electro-mechanical meters,and coupling these to voltage and current sensors - rather thantransformers, the operating range, the accuracy and linearity of themetering system can be improved. As modern electronics allowsvirtual open-circuit operation of voltage and current sensors, suchsensors remain linear over a wide range.

Instead of electrodynamometer instruments, the signals fromcurrent and voltage sensors are digitized and processes in acomputer to provide the required readings. There are no moreindividual instruments for each measured quantity, all of thequantities are computed and displayed on an appropriate screenfor the operator to see. As the analog-to-digital technologies arewell advanced and so are the programs that compute "rms" and"average" ("flux voltage") values, what becomes important is theproper sensing of the voltage and current parameters. For thisreason, the remainder of this paper will discuss the sensing of thevoltage and current, rather than converting the signals into a readingof voltage, current and power.

SELECTION OF SENSORS.

Practical voltage sensors include:* Magnetic voltage transformer,

* Capacitive voltage transformer,

* Resistive divider,

* Capacitive voltage divider,

* Amplifier aided capacitive divider.

Figure 3. Amplifier Aided Voltage Divider.

The magnetic and capacitive voltage transformers were very quicklyeliminated as neither of tem is capable of providing the linearityover the operating range. Similarly the resistive divider was rejectedbecause of the heating of the high-voltage, high resistanceelements. What remained, was the capacitive divider - either direct,or in an amplifier aided inverting configuration. The amplifier aidedconfiguration was selected as it requires considerably lessshielding and guarding than does a plain divider and is shown inFigure 3. The actual construction of the high-voltage capacitor is

most important in order to maintain linearity and stability. Aconcentric "tube-in-a-tube" was selected as it is similar to theconstruction of "Standard HV capacitors" that have been found to



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exhibit the required characteristics of stability with respect totemperature, linearity with respect to voltage and suitability of high-voltage operation. It must be pointed out that when the capacitivedivider is used in Figure 2, it does not add to the losses beingmeasured by the wattmeter.

Practical current sensors include:

* Shunts,

* Current transformers,* Compensated current transformers,

* Inductive current sensors.

As there are practical difficulties in using shunts at high voltage, theiruse was eliminated. Current transformers are the most acceptablesensors for current and can be designed to meet very stringentaccuracy and load requirements. Even the best of these, however,are limited in their dynamic range to about 100 to 1, which is notsufficient of this application. The compensated currenttransformers, however, do offer improved linearity and accuracy.The type of compensation used, makes them more suitable for oneor another applications. Some of the more suitable configurations

include:* two stage design,

* zero flux design,

* amplifier compensated design.

The two stage CT design of Brooks and Holts /1./ is the oldest, butfor some reason not used by the industry very often. This two stageCT is capable of extremely high accuracy and very wide dynamicrange. In addition, the error curves of the two stage CT are very flatand change very little with the load current. The CT is illustrated inFigure 4.

Figure 4. Two-Stage Current Transformer According to

Brooks & Holts.

The operation of the two-stage current transformer can beexplained as follows. The transformer is wound in such a way that

the difference in ampere-turns between primary (H1 - H2) and thesecondary (X1 - X2) is applied to core B and this results in a currentin the tertiary winding (T1 - T2). When properly burdened, andassuming and error of 0.1%, the secondary current will be 99.9% ofideal. If the tertiary winding also operates with an error of 0.1%, andsupplies 99.9% of the remainder, the overall accuracy of thetransformer will be in the vicinity of 0.0001%, or one part permillion. The above operation is maintained provided that thewindings are burdened individually - as shown in Figure 4. Suchindividual burdening and current summation is easy to accomplishin electronic circuits.

METERING CONNECTIONS.

The loads that need be considered are:

* two-wire, single-phase,

* three-wire, three-phase,

* four-wire, three-pahse.

According to standards, two element metering is not allowed on

three-phase, three-wire, circuits. This means that only single-phasemetering is used, thus for three-phase circuits one must use threesingle-phase circuits, regardless if the load is Delta or Wyeconnected. The reason two-element metering is not allowed isbecause the power reading in such a connection comprises of thedifference of two large readings. Any small scaling errors betweenthe two elements leads to large errors in the overall measurement.

The example below indicates the problem of two-elementmeteringat low power factors:Line current 1000 amperes.Line-line voltage 14,400 volts.Power factor 0.01

True power 250 kW.Wattmeter #1 +7,325 kW.Wattmeter #2 -7,075 kW.

Difference 250 kW.

It can be readily seen that even an error of only 1% in eitherwattmeter will cause an error of approximately 30% in total powerdetermination.

THE MODERN METERING SYSTEM.

The modern, or up-to-date metering system avoids all ofthe problems associated with systems using CTs, VTsand conventional instruments. The majorimprovements are as follows:

* linear voltage and current sensors re quiring nocorrections over the designed range of voltage andcurrent.

* automatic or manual current and voltage rangesswitching.

* accurate power measurement with full-scale valuesat power factors as low as 0.01.

* digital presentation of readings.

* frequent updating of all readings.

* provision for obtaining all three-phase readingssimultaneously.

* provisions for viewing and saving the readings aswell as waveforms,

Typical specifications for such a system would be:

Voltage : 0 - 138 kV, operating seamlessly over therange of 200 volts to 138 kV.

Current : 0- 2,500 A, operating seamlessly over therange of 0.5 to 2,560 amperes.

Power : Accuracy 0.3% at 1.0 PF, 0.6% at 0.1 PF,3% at 0.01 PF.

REFERENCES

1. H.B. Brooks and F.C. Holtz "The Two-stage CurrentTransformer". AIEE Transactions, Vol. 41, June 1922,

p. 382.



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New Role of Transformer Magnetics in FACTS TechnologyR Saha* and Bhim Singh**

*Central Electricity Authority, Sewa Bhawan, R K Puram, New Delhi 110 066,[email protected]

**Electrical Engineering Deptt., Indian Institute of Technology Delhi, Hauz Khas,New Delhi 110 016, [email protected].

Abstract- A Transformer is one of the vital components in ACtransmission, sub-transmission and distribution systems and itsversatile role has been widely acknowledged in the power system.Out of the various types of transformers, most common are powertransformers (viz. generator transformer, interconnectingtransformer), distribution transformers and instrument transformers(viz. current transformer, potential transformer). The corefunctionality of such transformers is either to step up voltage or tostep down voltage to a desired level. The power transformer alsohas a provision of voltage control mechanism in transmission systemthrough on-load/off load tap changing arrangement. To increaseloading capacity of the transmission line on the basis of power

angle regulation, typical phase shifting transformer (PST) is alsoemployed in series with the transmission line. With the advent offlexible alternating current transmission system (FACTS)technology/controller, especially solid-state power electronicsbased voltage source converter (VSC) technology, versatility oftransformer applications has increased manifold. In high powerrating VSC based FACTS controllers such as static synchronouscompensator (STATCOM), unified power flow controller (UPFC)etc., the transformer magnetics is one of the key component and it isextensively used to electro-magnetically sum up the AC outputvoltages of multiple VSCs, to eliminate certain voltage and currentharmonics originated from solid-state switching converters, toemploy as an harmonic neutralizer evolved through phase shiftingmethodology and to step-up of converter circuit voltage to

transmission level. In this paper, new roles of the transformermagnetics and its significant utilities are illustrated in FACTScontrollers (e.g. STATCOM).

1. INTRODUCTION

In power electronics based Flexible Alternating Current System(FACTS) controllers[1-11] such as Static Synchronous Compensator(STATCOM), Unified Power Flow Controller (UPFC) and ConvertibleStatic Compensator (CSC) being widely used in EHVACtransmission system, the switching controllable gate-turn-off (GTO)thyristors based voltage source converter (VSC) topologies withenergy support from DC capacitor (C) are extensively employed tohave smooth and rapid control of system dynamics under steadystate and dynamic system conditions. The inherent attribute of suchVSC operated at fundamental frequency switching modulation is tohave 6-pulse AC voltage output i.e. equal step-sized staircasewaveform with 60deg displacement between the steps in a cycle.This elementary 6-pulse VSC is the backbone of a FACTS controller.The AC output voltage contains harmonics in the order of 6N1,where N=1,2,3, which is exceedingly high and much beyondpermissible standard limits [12]. In practice, many VSC units areconnected to obtain high pulse-order AC output voltage (e.g.multi-pulse configuration) so that harmonics pollution is minimizedimproving operational performance of the FACTS controllers to anacceptable level and harmonics level is limited to the order of6PN1, where P is the number of VSCs.

Out of the few FACTS controllers, STATCOM is one of the state-of-the-art dynamic shunt controllers being extensively used in

transmission system to rapidly control voltage in transmissionsystem, load power factor correction, power oscillation damping,

increase loadability of transmission line, etc. through controllablegeneration or absorption of reactive power. Fig.1 depicts the layoutof a GTO-VSC based

STATCOM device, and Fig. 2 illustrates an AC output voltagewaveform from an elementary 6-pulse VSC.

Fig.1. STATCOM Configuration.

Fig. 2. Output AC phase voltage of an elementary 6-pulse VSC

operated with FFS modulation.

The major components of STATCOM are VSCs (usually gate-turn-offbased voltage source converters i.e. GTO-VSCs), transformermagnetics, DC capacitor (C) as energy storage device, controllers,etc. A controllable three-phase harmonic optimized voltagewaveform close to sinusoidal form (V ) is obtained at the point ofccommon coupling (PCC) by summing up of the AC output voltagesof VSC bridges electromagnetically and it is regulated by DCcapacitor(C) voltage (Vdc), which is indirectly controlled by phaseangle difference across the leakage reactance of the transformer

circuit relative to the system voltage (V ).When V > V , thes c sSTATCOM is considered to be operating in a capacitive mode and



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when V


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Fig. 5. Inter-facing Magnetics of Stage-I and Stage-II and

STATCOM terminal voltage (staircase waveform).

While designing the above magnetics configuration, U#1transformer is modeled with multi-winding configuration which isshown in Fig.6. The winding configuration of the PSTs and its phasordiagram are shown in Figs.7-9 respectively.

Fig. 6. Y/D-Y Transformer (U#1).

Fig. 7. Zig-zag 15 lead PST(U#2). Fig. 8. Zig-zag 15 lag

PST (U#3).


Fig. 9. Phasor diagram of zig-zag 15 lag PST and 15 lead

PSTs .

2.2. Harmonics Reduction Principle

While two identical 6-pulse GTO-VSC bridges are connected inparallel across the DC capacitor and operated with displacementangle of 30 (lagging) with AC output terminals of two converters

connected to Y-winding (secondary) and D -winding (secondary)of the Y-D/Y intermediate transformer. The secondary winding turnsof the D-winding (secondary) is made 3 times the Y-winding(secondary) to maintain equal AC line voltage on the converter side.By Fourier series expansion, the synthesized AC output voltages(phase-A) of the converters (Fig.5), V (t) and V (t) become,y d

(1)

(2)

where, V is the DC capacitor(C) voltage and is the line frequency.dc

On adding V (t) and V (t), the resultant 12-pulse voltage phasor Vd y(t) is,

(3)

where, V ,V and V are amplitudes (pu) of fundamental, 11th and1 11 1313th harmonic voltage respectively.

It is observed from (3) that 5th, 7th, 17th, 19th.... voltage harmonicsare attenuated and the AC output voltage waveforms V(t) contains11th, 13th,. harmonics. Turn ratios of the intermediate transformer

(U#1) is determined to obtain its phase to phase output voltageequal to half of the line voltage.

2.2.1. 11th and 13th Harmonics Neutralization

Two voltage signals are generated from the output voltage signal of

the intermediate transformer(U#1) with phase shift of 15 lead, and

-15 lag by employing two zig-zag phase shifting transformers, U#2

and U#3 respectively. These signals in combination of the voltageoutput voltage signals of U#1 transformer are electromagnetically

added at PCC and the resultant voltage phasor V(t) in pu PCCpubecomes:


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V(t) =pu

(4)

where,

V= normalized amplitude of output phase voltage of transformer,IU#1.

V = normalized amplitude of output phase voltage (s) of 15 PSTsx(U#2 andU#3).

V= amplitude of line phase voltage in pu (=1pu).

The turn ratios of the two PSTs are determined to obtain its primary

side voltage (Vx) equal to quarter of the transmission system

voltage (V) and the desired phase shifts of 15 lead, and -15 lag byzig-zag winding connection, and turn ratio of the intermediate

transformer (U#1), is determined to obtain output voltage (V1)

equal to half of the transmission system voltage (V). With this, the

predominant 11th and 13th voltage harmonics are neutralized and

the expression of the resultant phasor voltage signal (in pu) at PCC

becomes,

(5)

The 5th, 7th, 11th, 13th, 17th, .. voltage harmonics are neutralized in

the STATCOM terminal voltage.2.3 Magnetics of 24-Pulse STATCOM

The magnetics configuration [10] of a 24-pulse (4x6-pulse), 2-level

GTO-VSC based STATCOM having two VSC-pairs operated with

FFS modulation with triggering angles of (37.5, 7.5) and (22.5, -

7.5) is shown in Fig. 10. The magnetics envisaged for the STATCOM

performs multi tasks viz. electromagnetically summing-up of AC

voltage output of the four VSC bridges, harmonics attenuation

and stepping-up of synthesized AC voltage of the converters to the

transmission voltage at PCC. Two multi-winding transformers of

Y/DY configurations (as shown in Fig. 6) are used of which primaries

(Y) are connected in series on the line side and 30 phase

shifting secondary sides (D-Y) to be connected to the VSC-pair

(37.5, 7.5) and VSC-pair (22.5, -7.5). The turn ratio of the

secondary windings (D-Y) is made 3 to maintain equal output

voltage across the terminals of both the transformers and the

voltages of the primary sides being connected in series are

summed-up electro-magnetically to obtain a staircase waveform of

equal step-size (15) at the STATCOM AC terminals, which contains

a 24-pulse voltage waveform (Fig. 11) close to sinusoidal nature

with 24N1 order of voltage harmonics. Thus, with single stage

magnetics employing only two three-phase transformers, areasonably good operational performance of such a STATCOM can

be obtained.

Fig. 10. Inter-facing magnetics of 4x6-pulse STATCOM.

Fig. 11. 4x6-pulse STATCOM terminal voltage.

2.4. Magnetics of 48-Pulse STATCOM

An harmonic neutralized and close to sinusoidal AC output voltagewaveform is obtained at PCC by adding electro-magnetically the

square wave voltage output waveforms of 4-pairs of GTO-VSC

bridges operated at fundamental frequency switching at phase

displacement angles of (11.25, 161.25), (3.75, 176.25),

(18.75, 191.25) and (33.75, 206.25). The waveform contains

harmonics of the order of 48N1, where N=1, 2, 3, 4,etc. Fig. 12

illustrates the magnetics employed in 48-pulse GTO-VSC based

STATCOM, which has resulted in an harmonics neutralized voltage

waveform at PCC. The magnetics envisaged for such a 48-pulse

STATCOM performs multi-tasks viz. summing-up of AC voltage

output of the four VSC bridges electromagnetically, harmonics

attenuation and stepping-up of synthesized AC voltage of theconverters to the system voltage at PCC. The four decoupled AC

output voltages from VSC bridges are coupled with the

transmission system through magnetics which is designed with a set

of four transformers that include three numbers zig-zag PSTs with

phase shifts of 15, +15 and +30 and a normal transformer. The

phase-displaced AC voltage signal from each terminal of the four

VSC pairs i.e. 6-terminals for a pair of VSC, feed the opposite ends

of the open-wye secondary terminals of transformers U#1, U#2, U#3

and U#4. The primaries of the transformers (U#1,2,3 and 4) are

connected in series to electro-magnetically add the outputs from

the four pairs of VSC bridges. Thus, a composite multi-pulse voltage waveform of 48-steps with a displacement angle of 7.5 is

achieved at the PCC. The resulting AC voltage waveform contains

48N1 harmonics i.e. 47th, 49th, etc.


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2.5. Design Parameters of Magnetics for 12-Pulse, 24-Pulse

and 48-Pulse STATCOMs

From design consideration, the synthesized AC terminal voltage ofthe converter circuit in high power rating GTO-VSC basedSTATCOM (of the order of 80MVA or above) is generally of the orderof 5kV to 25kV. The design parameters of magnetics configurationsfor the multi-pulse (viz. 12-pulse, 24-pulse and 48-pulse) 2-level

100MVAr GTO-VSC based STATCOMs together with theSTATCOM system parameters are given at Appendix A, B and Crespectively.

3. CONCLUSIONS

The transformer equipment has been inherently one of the majorcomponents in the state-of-the-art high power rating solid-stateFACTS controllers being extensively used in transmission system.With the advent of controllable solid-state voltage source convertertechnology, which is the backbone of FACTS technology, versatileapplications of transformer magnetics have been realized. Out ofthe few FACTS controllers, the GTO-VSC based static synchronouscompensator (STATCOM) is widely used as a dynamic shuntcompensator in high voltage transmission system. The role of

magnetics in developing multi-pulse STATCOM has been realizedto be multifold. For cost effective solution, it has been the researchtrend to optimize root components of such controllers. In thisdirection, some topologies of transformer magnetics have beenfocused for low to high pulse order STATCOMs.

Appendix-A

Magnetics for GTO-VSC based 12-pulse, 2-level, 100MVArSTATCOM:

(i) Converter Type-VSC; Thyristors GTO; No. of pulses 12;Nominal AC voltage 5.1kV; Nominal DC link voltage - 8.3kV;GTO fixed resistance - 0.01W; GTO triggering control-fundamental frequency (50Hz) switching; DC Capacitor -20000F.

(ii) Magnetics (Base-100MVA)

Stage-I

3-phase 3-winding Transformer (U#1)Rating: 100MVA, 50Hz, 5.1/66kV, 12.8% (X)Vector group: Y/.-Y



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Stage-II PST (U #2):

3-phase 3-winding zigzag connected (+)15 PSTRating: 25MVA, 50Hz, 66/33kV, 10. 8% (X)Vector group: zigzag or interconnected-star/open-Y

PST(U #3):

3-phase 3-winding zigzag connected (-)15 PST

Rating: 25MVA, 50Hz, 66/33kV, 10.8% (X)Vector group: zigzag connected-star/open-Y

Appendix-B

Magnetics for GTO-VSC based 2-level, 24-pulse, + 100MVArSTATCOM:

(i) Converter Type-VSC; Thyristors GTO; No. of pulses 24;Nominal AC voltage 5.1kV; Nominal DC link voltage - 8.3kV;GTO fixed resistance - 0.01W; GTO triggering control atfundamental frequency (50Hz); DC Capacitor (C) - 15000F.

(ii) Three-phase three-winding Transformer- 2 Nos. Rating: 50MVA, 66/5.1/5.1 kV, 50Hz, 8% (X) Vector group: Y/(D-Y)(single phase 3-winding transformer units used-6 Nos.)

Appendix-C

Magnetics for GTO-VSC based 48-pulse, 2-level, 100MVArSTATCOM:

(iii) GTO-VSC converters-8 Nos.; No. of pulses 48; Nominal ACvoltage 5.1kV; Nominal DC link voltage-8.3kV; GTO fixedresistance - 0.01W; GTO triggering control at fundamentalfrequency (50Hz); DC Capacitor (C) - 4000F.

(i) Magnetics

Transformer (U # 1):3-phase 3-winding zigzag connected (-) 15 PSTRating: 25MVA, 50Hz, 33 kV/10.2kV, 8% (X)Vector group: Y/zigzag-Y

Transformer (U # 2):3-phase 2-winding normal step-up TransformerRating: 25MVA, 50Hz, 33kV/10.2kV, 8% (X)Vector group: Y/Y

Transformer (U # 3):3-phase 3-winding zigzag connected (+) 15 PSTRating: 25MVA, 50Hz, 33 kV/10.2kV, 8% (X)Vector group: Y/zigzag-Y

Transformer (U # 4):3-phase 3-winding (+) 30 PSTRating: 25MVA,50Hz, 10.2/(33/3) kV, 8% (X)Vector group: zigzag or interconnected-star/Y

4. REFERENCE

[1] N. G. Hingorani and Laszlo Gyugyi, Understanding FACTS,IEEE Power Engineering Society, IEEE Press, New York, 1999.

[2] A. T. Johns, A Ter-Gazarian and D. F. Warne, Flexible ACtransmission systems (FACTS), IEE Power and Energy series30, the Institute of Electrical Engineers, London, UK, 1999.

[3] K. R. Padiyar, FACTS Controllers in Power Transmission and

Distribution, New Age International (P) Limited Publishers,India, 2007.

[4] K.K. Sen and M. L. Sen, Introducing the family of SenTransformers: A set of power flow controlling transformers,IEEE Transactions Power Delivery, Vol. 18, , pp. 149 157,Jan 2003.

[5] Shosuke Mori, Katsuhiko Matsuno, Taizo Hasegawa, ShuichiOhuichi, Masatoshi Takeda, Makoto Seto, Shotaro Murakami,and Fuijio Ishiguro, Development of a Large Static VARGenerator using self-commutated inverters for improvingpower system, IEEE Trans. Power Systems, Vol. 8, No.1, pp.371-377, February 1993.

[6] C. Schauder, M Gernhardt, E. Stacey, T. Lemak, L. Gyugyi,T.W.Cease and A. Edris, Development of a 100 MVAr StaticCondenser for Voltage control of transmission systems, IEEETrans. Power Delivery, Vol. 10, No.3, pp. 1486 1496, July1995.

[7] K. K. Sen, Statcom - Static Synchronous Compensator:Theory, Modeling, and Applications, IEEE PES WM 1999, Vol.2, pp. 1177 1183.

[8] C. Schauder, L. Gyugyi, E. Stacey, M. Lund., L. Kovalsky, A. Keri,A. Mehraban, and A. Edris, AEP UPFC project: installation,commissioning and operation of the 160 MVA STATCOM(Phase I), IEEE Trans. Power Delivery, Vol. 13 4, pp. 1530

1535, Oct. 1998.

[9] Bhim Singh, and R. Saha Modeling of Harmonic Neutralized12-Pulse Static Compensator (STATCOM), Proc. of 2006 IEEEPower India Conference, India, Apr. 8-10, 2006.

[10] Bhim Singh, and R. Saha,A New 24-Pulse STATCOM for Voltage Regulation, Proc. of 2006 IEEE InternationalConference on Power Electronics, Drives and Energy Systems,PEDES 2006, India, Dec. 12-15, 2006.

[11] R. Saha, Analysis Design and Control of Static SynchronousCompensator, Ph.D. Dissertation, Dept. Elect. Eng., IndianInstitute of Technology Delhi, 2007.

[12] IEEE Std 519-1992, IEEE Recommended Practices andRequirements for Harmonic Control in Electric Power Systems.

[Views expressed are of the Author & not of ITMA]



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ABSTRACT

Transformer is considered as the heart of electric powertransmission and distribution system. Uninterrupted andeconomical power supply calls for reliable operation oftransformer. It is highly essential to assess the quality of transformerduring procurement and also to maintain the transformers while inservice. Preventive maintenance of transformer through dissolvedgas analysis are discussed in this paper with case studies of CPRIexperience.

1. Introduction

Power transformers constitute one of the largest investments in autilitys system. Transformer condition assessment and managementis a high priority. Transformers are operating beyond their designlife and with higher average loads than ever before. Transformerfailure rates both catastrophic and non catastrophic continue toincrease. Funding the cost to replace enough power transformers isnot an alternative for most utilities. This situation demands the bestasset management and condition assessment. Dissolved gasanalysis (DGA) of transformer insulating oil is considered the singlebest indicator of a transformers overall condition is practiceduniversally today.

The use of appropriate DGA diagnostic methods can improveservice reliability, avoidance of transformer failure and deferredcapital expenditure for new transformer assets. Information fromthe analysis of the gasses dissolved in insulating oils is valuable in apreventative maintenance program.

Power transformers are an asset class constitutes one of the largestinvestments in utilities, therefore it is of vital importance to monitorcondition, assessment and management is a high priority to assessoperating condition of such expensive equipment. Technology ofoil filled transformers remained invariable for years, the transformeroil and cellulose paper are being used as insulating materials toprovide the required dielectric strength and cooling of internalconductors during transformer operation.

The insulating oil under normal operating conditions will generallyretain its electrical and chemical stability. Incipient conditions -

electrical or thermal - can progress undetected. In the transformer,insulating oil is prone to undergo changes in its chemical anddielectric properties due to oxidation reaction, these reactions areaccelerated by copper, aluminum and along with electrical &thermal stresses.

All the transformers generate gases during operation; the type andconcentration of each gas and the rate of generation can help toknow whether the transformer is operating properly ormalfunctions. When energy is discharged in the transformer, such asarcing or corona, a chemical reaction can take place that breaksdown the oil molecules of gas and cause the oil to decompose,resulting in the low molecular weight gases to dissolve into the oil.To determine the type of fault in the transformer by Dissolved gas

analysis of insulating oils for reliable information on the condition oftransformers and to implement the necessary maintenance plans toprolong their lifespan.

1.1. Back ground / Limitations

Dissolved Gas Analysis has been accepted as the industry standardfor determination of incipient faults in the transformer. Many labshave begun offering this service and it is good for the industry, butthe results of these labs and reliability to perform this analysis areimportant. Provided the methods are followed properly, i.e.sampling of oil, extract the gases within the sample and gases aredetected using a gas chromatography (GC) with columns toseparate the gases and exit to flow into two or three detectors,which have ability to quantify the gases. Many errors may occur inextraction of gases and the calibration of GC is important with validcalibration standard; the results will be repeatable if the carrier gas

flows and detector sensitivity remain constant. When allprecautions are taken then results obtained from this service shouldgive the engineer the information needed to make an informaldecision on the operating status of a transformer.

2. Transformer Assessment

The transformer assessment will make easy to understand type ofmaintenance required and future maintenance requirement.Transformer condition monitoring depends on proper diagnosticsand accurate interpretation & analysis will provide realistic decisionfor economical operation and cost effective maintenancestrategies. The overall assessment can reduce minimum risk ofsudden failure and environmental risk, thus condition monitoringcan provide information on developing problems, internal

condition of transformer and early warning for abnormality, whichcan avert any catastrophic failure due to incipient faults.

The data of dissolved gas analysis in transformer oil gives valuableinformation in preventive maintenance program. The advantages offault gas analyses can provide the following information:

New transformer status after heat run test

Detection of faults during warranty period

Check on maintenance & improper use of transformer

Advance warning on developing faults

Status of repaired unit and failure analysis

Convenient schedule of repairs

Monitoring of transformer under overload

2.1. Power Transformer Failures and Problems

Transformer failure can occur as a result of different causes andconditions

any forced outage due to transformer damage in service likewinding damage, tap changer failure.

trouble that requires removal of the transformer for return torepair facility or which requires extensive field repair.

Failures are usually triggered by severe conditions such as lighteningstrikes, switching transients, short circuits. When the transformer isnew, it has sufficient electrical and mechanical strength towithstand unusual system conditions. As transformers age, theirinsulation strength can degrade to the point they cannot withstand

system events such as short circuit falls or transient over voltage.

To prevent these failures and to maintain transformers in goodoperating condition is a very important issue for utilities. There is atrend in the industry to move from traditional time based

CONDITION MONITORING OF TRANSFORMERSBY DISSOLVED GAS ANALYSIS

D. Ravindra, Scientific Officer and G. Kishore Kumar, Engineering OfficerCENTRAL POWER RESEARCH INSTITUTE, BANGALORE.



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maintenance program to condition based maintenance. Thesechanges occur at a time when the average age of the transformers inservice is increasing and approaching the end of normal design life.Change to condition based maintenance has resulted in thereduction or even elimination of routine time based maintenance.There is an increasing need for better non-instructive diagnostic andmonitoring tools to assess the internal condition of the transformers.

A scientific life assessment of transformer is an important tool

towards higher reliability of the system and asset management. Bydetermining the critical components responsible for failure, thetechnical assessment can reduce by implementing the correctoperational and maintenance strategies. The critical componentsviz. core, windings, insulation oil, bushing and on-load tap changerare the main active parts of the transformer. The monitoring andassessment of such components is vital to achieve better reliabilityof the system. The types of failures which may occur within thetransformer and the main causes are:

* Electrical failure of the internal insulation caused by:

Abnormally high operating temperatures (can be the result offires, oil leakage or failure of the oil cooling system); when oil-filled electrical equipment is subjected to thermal orelectrical stresses, faults may occur, usually in the form of hotspots, partial discharges and ultimately arcing.

Oil contamination;

Internal joints becoming loose, causing spot heating;

Voltage spikes caused by external faults or lightning;

The physical failure of the cellulose due to combinations ofageing, sudden movement of the coils as a result of externalfaults and vibration of the coils caused by gradual reductionsin clamping forces. The weakest link of any transformerinsulation system is the cellulose. In the majority of cases, thefailure of a transformer is related to an insulation breakdown,and the reason for the failure is usually mechanical underthe stress of physical forces, the insulation gives way

Presence of moisture

* Failure of Tap Changer

This is the only moving part in the transformer and is subjectedto continuous stress.

* Failure of external insulators

* Failure of external terminals due to damage or looseconnections;

* Explosion of the tank, usually caused by an internal electricalshort circuit vaporising some oil and therefore increasing thepressure in the tank; and

* Incorrect electrical phase connections to the outside system.

2.2. Analysis of Fault Gases

Faults in power transformers may occur due to electrical andthermal stresses. These faults can be differentiated form their

energy, localization and occurrence period. Along with a fault,there is increase in oil temperature and generation of certainoxidation products and soluble gases. These gases are consideredas fault indicators and can be generated in certain patterns andamounts depending on the characteristics of the fault. Low energyfaults leads to formation of hydrogen and saturated hydrocarbon C1to C , and high energy faults tend to generate unsaturated2hydrocarbonsC containing double or triple bonds.2+n

The generated gases in transformer are dissolved in the insulatingoil, in the blanket above the oil, or in the gas collecting devices. Thedetection of an abnormal condition requires an evaluation of theamount of combustible gas present and rate generationcontinuously. The source of the gases and composition indicatemalfunction and leads to failure if not corrected. The detection andmeasurement of gases have been established, the analysis of these

gases and interpretation of their significance is an art subject tovariability. The presence of gases and quantity are dependent onvariables such as temperature of the fault, solubility and degree of

saturation of various gases in oil, the kind of material in contact withthe fault.

Hence, qualitative and quantitative determination of dissolvedgases in transformer oil may be of great importance in order toassess fault condition and further operating reliability of powertransformers.

2.3. Methods of Fault Gas Detection

Three methods will be discussed and their advantages anddisadvantages will be compared. The first method and probablythe most widely used technique at the present time is the one thatdetermines the total combustible gases ( TCG ) that are present inthe gas above the oil. The major advantage of the TCG methodcompared to the others that will be covered is that it is fast andapplicable to use in the field. In fact it can be used to continuouslymonitor a unit. However, there are a number of disadvantages to theTCG method. Although it detects the combustible fault gases(hydrogen, carbon monoxide, methane, ethane, ethylene, andacetylene), it does not detect the noncombustible ones (carbondioxide, nitrogen, and oxygen). This method is only applicable tothose units that have a gas blanket and not to the completely oil-filled units of the conservator type. Since most faults occur underthe surface of the oil, the gases must first saturate the oil and diffuseto the surface before accumulating in the gas blanket above the oil.These processes take time, which delays the early detection of thefault. The major disadvantage of the TCG method is that it gives onlya single value for the percentage of combustible gases but does notidentify which gases are actually present. It is this latter informationthat is most useful in determining the type of fault that has occurred.

The second method for the detection of fault gases is the gasblanket analysis in which a sample of the gas in the space above theoil is analyzed for its composition. This method detects all of theindividual components; however, it is also not applicable to the oil-filled conservator type units and it also suffers from thedisadvantage that the gases must first diffuse into the gas blanket. Inaddition, this method is not at present best done in the field. Aproperly equipped laboratory is preferred for the requiredseparation, identification, and quantitative determination of these

gases at the part per million levels.The third and most informative method for the detection of faultgases is the DGA technique. In this method a sample of the oil istaken from the unit and the dissolved gases are extracted. Then theextracted gases are separated, identified, and quantitativelydetermined. At present this entire technique is best done in thelaboratory since it requires precision operations. Since this methoduses an oil sample it is applicable to all type of units and like the gasblanket method it detects all the individual components. The mainadvantage of the DGA technique is that it detects the gases in the oilphase giving the earliest possible detection of an incipient fault.This This advantage alone outweighs any disadvantages of thistechnique.

3. Case Studies of Transformers :

Case - 1 : GT Transformer, 325 MVA

19/11/07 4/12/07 10/3/08 25/4/08

Total Gas Content TGC 93760 64460 93760 79110

Methane CH4 1441 1819 2891 5313

Ethane C2H6 472 805 2098 4012

Ethylene C2H4 1253 2101 5006 9085

Acetylene C2H2 1 0 8 13

Hydrogen H2 364 483 1336 335

Oxygen O2 14409 7519 13595 11147

Nitrogen N2 56977 36779 49420 40505

Carbon monoxide CO 3391 156 0 0

Carbon dioxide CO2 4581 5299 5050 1202

Total combustible TCG 3531 5208 11339 18758gases



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3.2. Results of Investigation :

CPRI Recommendation :

DGA indicates high concentration of acetylene gas due toarcing fault

Abnormal increase in acetylene gas concentration due toarcing fault viz. arc with power follow through or persistentsparking. Recommended for immediate internal inspection of

the transformer.

3.2.2. Findings :

DGA test of ICT - B phase had shown increasing trend of acetylenegas indicating possibility of arcing fault. Internal inspection of ICT-Bphase revealed arcing had taken place between the tap changersupport plate i.e, L plate and OLTC drum. After removing tapchanger support it was found that the press board insulationprovided between tap changer support and aluminum ring wasburnt and its burnt insulation was found deposited in the bottom ofthe tank



CPRI Recommendation : DGA indicates thermal fault of mediumo otemperature of 300 C to 700 C.

3.1.2. Findings : Conductor overheating at L.V. Bushing.

Case - 2 : I C T - 1, B Phase, 167 MVA

14/6/07 26/7/07 20/8/07

Total Gas Content TGC 105480 99620 99620

Methane CH4 43 106 154

Ethane C2H6 5 14 29

Ethylene C2H4 69 224 320

Acetylene C2H2 671 2652 4063

Hydrogen H2 72 776 1442

Oxygen O2 26586 22044 27980

Nitrogen N2 59911 58225 47203

Carbon monoxide CO 0 0 0Carbon dioxide CO2 650 735 676

Total combustible gases TCG 860 3772 6008


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Case - 3 : G T Transformer, 33 MVA


CPRI Recommendation: DGA indicates thermal fault of hightemperature.

Recommended for immediate internal inspection of thetransformer.

3.3.1. Findings :

The internal investigation reveals over heated joints

Latest techniques of DGA

The DGA technique is an important tool for monitoring andtroubleshooting. There are new Gas Chromatograph (GC)techniques available. The Transformer Oil Gas Analyzer (TOGA) GCuses a dual port valve and gas extraction loop configuration forextracting and injecting dissolved gases. In this technique thetransformer oil is pumped through the permeation tube, thedissolved gases therein selectively permeate through the heated

o(70 C) membrane into the surrounding extraction chamber andinjecting dissolved gases from the extraction chamber onto theMolecular Sieve 13X column, then on to the Silica Gel column.

There is a Stripping Method accepted by ASTM and this methodavoids the use of the high vacuum degassing apparatus andMercury. Samples of oil are injected directly into the instrumentwhere a flow of nitrogen gas is allowed to bubble through the oil.The nitrogen forces the other gases to come out of solution wherethey are allowed to flow into a gas chromatograph. This appears tobe a much easier method to follow but there are problems with thismethod as well; one being the extraction efficiency, another being

that the instrumentation is much more complicated.The Shake Test method is a new method that has not yet beenaccepted by ASTM, but the principles are similar to Headspace. Oilsamples are obtained using a Shake Test syringe. The oil sample islarger than the other methods but the equipment needed toperform the analysis is much simpler to operate. The Shake Testsyringe is a 100cc syringe. To extract the gases, the technician mixesthe oil in the syringe with a fixed quantity of CO2 free air. This takesapproximately one minute. Then the syringe is attached to aportable GC where the analysis of the gases is done.

4. Conclusion

The results from a dissolved gas analysis are important to takedecisions about transformer. We can derive reliable information on

the physical condition of the asset by reviewing historical trendsand then applying internationally-accepted protocols to assess theratios of the fault gases detected. This identifies faults caused byoverheating, sparking and corona, enabling to initiate plannedinspections and tests instead of emergency action. DGA is awindow into the internal working of critical electrical equipmentand when carried out regularly, is the most valuable weapon in assetmanagement arsenal. In conclusion, dissolved gas analysis hascome a long way over the years. To ensure the consistency of theresults; methods and procedures must be followed. If the resultsare unreliable; costly and incorrect decisions will be made.

The most widely used test to diagnose the condition oftransformers is DGA of transformer oil. The ultimate goal of

transformer monitoring and diagnostic techniques is to anticipatethe transformer failure, so that appropriate action can be takenbefore forced outage occurs. The organizational culture of a powerutility significantly imparts on the operational practices in the use ofcondition based maintenance.

5. Acknowledgements

The authors are grateful to the management of CPRI for accordingkind permission to present this paper.

6. References

1) Power Transformer Condition Monitoring and Assessment forStrategic Benefits, Md. Arshad and Syed. M. Islam, Curtin

University of Technology, Australia.2) Dissolved Fault Gas Analysis Data A practical approach to

interpretation of Results Dr. J. E. Morgan and W. Morse,Morgan Shaffer Corpn.

3) Improvement of Interpretation of Dissolved Gas Analysis forPower Transformers, Jackelyn Aragon-Patil, Markus Fischer andStefan Tenbohilen, Ins. of Power Transmission and HighVoltage Technology, Germany.

4) IEEE and IEC Codes to interpret Incipient Faults in Transformer using gas in oil analysis by R.R. Rogers CEGB TransmissionDivision, Guilford, England, Circa 1995.

5) Trusting the Results of Dissolved Gas Analysis by WilliamMorse, Electricity Today Magazine Article, 2006.

6) Dissolved Gas Analysis of Transformer Oils: Effects of electricarc by Suwarno, 6th WSEAS International Conference onPower Systems, Lisbon, Portugal, 2006.


[Views expressed are of the Author & not of ITMA]


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Q1. How much can energy efficient measures help in reducing

the countrys carbon emissions?

The National Mission on Enhanced Energy Efficiency (NMEEE),which is part of the National Climate Change Action Programme, islooking at a series of measures which would together lead to areduction of about 98 million tonnes of CO2 every year by 2015.This would be done through the introduction of PAT which wouldnot only reduce the emissions but also has the potential to augmentthe cumulative installed capacity by adding 19 GW at the end of2014-15. Indias total emissions are a little over a billion tonnes. Weare looking to reduce those by at least 10 percent through theactions taken under the NMEEE.

However, we are not concentrating on reducing emissions only, asour goal is to enhance energy efficiency, increase energy security,and ensure that more people have access to energy in order tomake the industry become more competitive. The reduction ofcarbon emissions, thus, is a co-benefit of all these steps. Therefore,we are undertaking the four actions specified in the NMEEE: The firstaction is to design and implement the Perform, Achieve and Trade(PAT) mechanism, which would enable the trading of certifiedenergy savings; the second is to use the future energy savings tofinance the demand- management programmes; the thirdendeavour is to transform the market through promoting promptdevelopment and introduction of the more energy-efficientappliances; and, the fourth is to shape the finan cial and fiscalpolicies to accelerate the movement towards energy efficiency.These are the four building blocks of the NMEEE.

Q2. How would energy efficiency help India remain

competitive within the domestic market and in the

international market?

Since energy prices in India are very high, the manufacturers haveto be energy efficient; otherwise they will not be able to compete.This is the reason that every new and large industry that has been setup in India in the last 10 years is among the most energy and costefficient in the world.

We have a relatively free market. So if anybody has to manufacturecement or steel, or anything else, in India, they have to do it at aglobally competitive cost. Moreover, since energy prices in India

are very high, the manufacturers have to be energy efficient;otherwise they will not be able to compete. This is the reason thatevery new and large industry that has been set up in India in the last10 years is among the most energy and cost efficient in the world.Today we have the worlds most efficient cement, fertiliser and steelplants. However, we still have the older and smaller plants, whichare much less efficient. They use twice or thrice the energy used bythe new plants to produce each tonne of cement or steel or anyother product they make. Therefore, the challenge is to remove thisine fficiency. The trend is in the right direction, but it requiresacceleration.

Q3. Why is there a difference between the Restructuring

Projects and the Standard Energy Efficiency Projects?

Should the multipurpose restructuring projects, which arecommon in industrial renovation, also be included in energy

efficiency financing schemes? If yes, how should it be done?

The heat rate must be reduced at any power station that isrenovated and modernised. The minimum aim should be to reachthe original design heat rate or even reduce it further. Now, whydoesnt that happen? Well, it doesnt happen for a variety ofreasons. One reason is that till recently, there was no incentive fordoing so. Another reason is that very often there are no spare partsor more efficient condensers available for the older plants, whichare mostly based on Russian or Czech designs. For the financiallystruggling companies, funding becomes a problem. However,investing in improving plant load factor and reducing energyconsumption results in higher revenues and margins, which help acompany repay its loans quicker. The banks or the Power FinanceCorporation (PFC) have no problem lending for plant renovation

and modernisation, but the inherent financial health of theborrowing company has to be acceptable to them. This is thereason why NTPCs plants are efficient.

Investments in improving plant load factor and reducing energyconsumption results in higher revenues and margins. It helps acompany repay its loans quicker. The banks or the Power FinanceCorporation (PFC) have no problem lending for plant renovationand modernization, but the inherent financial health of theborrowing company has to be acceptable to them. This is thereason why NTPCs plants are efficient.

Another helpful step in this direction has been taken by the stateelectricity regulatory commissions. They have started setting targetsfor heat rate improvement while allowing the cost of the additionalinvestment required for it. Therefore, realistically speaking, there isno reason why the developers should not be able to do so. Thereasoning is simpleif they do it, they will make more profit; and ifthey dont, they will pay a very heavy penalty, as envisaged in theEnergy Conservation Act. There would be no incentive provided tothermal power plants, as they do not fall in the renewable category.In the case of renewable energy plants, there is an incurred net coston which the government provides incentives; whereas, in the caseof thermal power plants, the cost factor is replaced by net profi tswhen you make the plant more efficient, so there is no case ofproviding incentives.

Q4. Are there any regulations regarding heat rate reductions?

Under the Perform, Achieve and Trade system, we have specifiedthe heat rate reduction targets to be achieved by the industrial units.This system would be implemented through the regulatorycommissions - the Central Electricity Regulatory Commission for thecentral plants and the State Electricity Regulatory Commissions forthe state plants.

Q5. How would the Perform, Achieve and Trade mechanism

help the economy become more energy efficient?

The challenge lies in increasing the efficiency of all the plants. ThePAT mandates a specific target for reduction in the specific energyconsumption of each plant in a sector. The more efficient a plant,the lower are its targets and the less efficient the plant, the higher thetargets.

In any sector, you will come across some plants which are moreefficient and some which are not so efficient. The challenge lies in

DR. AJAY MATHUR, DIRECTOR GENERAL,BUREAU OF ENERGY EFFICIENCY IN CONVERSATION

WITH INFRALINEENERGY ON INDIAS ECONOMY ANDCLIMATE CHANGE MITIGATION EFFORTS A



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increasing the efficiency of all the plants. The PAT mandates aspecific target for reduction in the specific energy consumption ofeach plant in a sector. The more efficient a plant, the lower are itstargets and the less efficient the plant, the higher the targets. If acompany manages to do more than its targets, it receives additionaltradable energy saving certificates. It can sell these certificates toother companies which are unable to meet their targets or findmeeting those targets extremely expensive. This mechanism would

help the nation to achieve the desired energy savings. It also mattersthat it is achieved in the most cost effective manner. We areproposing that these certificates be traded through powerexchanges so that their price is discovered through trading.

Q6. If the price of the energy saving certificates is discovered

through trading, it may happen that the discovered price may

not be attractive enough for the stakeholders. How do you

propose to rationalise it?

The baseline is that everybody has to reduce the emissions bycertain numbers. If they are able to find energy saving certificates ata price which is lower than what it would cost them to improve theirown energy efficiency, they will buy the certificates. Otherwise,they will have to invest in their plants, or pay penalties. The problem

with creating a new market is that you have no idea of the prices,whether it is for certificates, derivatives, or anything else. A markettakes time to develop. Generally speaking, there is always anoverhead and that occurs because of the varied kinds of marketplayers. There are some who are risk averse and some who are risktakers. So, you have a spread and whenever you have a spread, themarket will find its optimal allocation.

The baseline is that everybody has to reduce the emissions bycertain numbers. If they are able to find energy saving certificates ata price which is lower than what it would cost them to improve theirown energy efficiency, they will buy the certificates. Otherwise,they will have to invest in their plants, or pay penalties. The problemwith creating a new market is that you have no idea of the prices

Q7. How much time would the market need to reach areasonable level of maturity?

We are setting the first compliance period three years from theintroduction date of the PAT. That would be followed by anotherthree-year cycle and another set of targets, and so on and so forth.My feeling is that the maturity will be achieved sometime after thefirst compliance period and before the completion of the secondcompliance period. Nowhere in the world have the marketsmatured within the first compliance period. During the first cycle,people experiment. Some people trade more, some less and somejust wait and watch till the market deepen and the price informationbecomes more transparent. After that stage, people start adjustingtheir own investment schedule to get the best prices. All this takes

time. Still, my feeling is that in the first compliance period, peoplewill overachieve. So, probably we might allow people to bank thecertificates for trading in the second period.

Q8. Would short-term trading of these certificates be

promoted? Would it be appropriate to emulate countries such

as France, Germany and the UK, where they issue certificates

and trade it on short-term basis and reap the benefits?

I cannot speak for the people who take short-term gains. However,there will be such people in the market and you need such peopleto give depth and liquidity to the market. However, it is also true thata market cannot be designed on the basis of the profitability ofinvestments made for short-term gains. At the end of the day, this isa compliance market. For a three-year period, the designated

consumers have to show that they have either done what they weresupposed to do or they have acquired certificates, or a mix of both.The certificates handed in for compliance are retired. A certificate

could be traded many times between the time of its issuance andthe time of its submission for compliance - between the compliantcompanies or between the market intermediaries. It is hard todetermine wheth er they would make money on these transactions.

Q9. Bolivias leadership termed the Cancun climate summit as

Ecocide by rich nations? Do you believe there is any

substance in their claim? How would the Cancun deliberations

affect the electricity market in India?

The Bolivian statements are rhetoric. They cannot be answered. Asfar as Cancun is concerned, I dont know how it will affect the Indianelectricity market. The summit has created a framework for a rangeof instruments for climate mitigation and adaptation under whichpeople would pledge voluntary actions. There will be anadaptation mechanism and an action committee which wouldpromote adaptation. Thus, it has created a structure, and over thenext one year, the operational details of this structure would befilled in. It creates a necessary framework for the necessary actions. Also, since people are pledging the emission reduction targetsthemselves, the chances are that these targets will be achieved, which, in turn, increases global confidence in climate changemitigation and adaptation agreemen ts. Therefore, it could, if

managed well at a multi-lateral level, lead to a virtuous cycle of thenations increasing commitments rather than diluting the oldcommitments, as is happening right now.

As far as India is concerned, post-Copenhagen we said that we willtry to reduce the carbon intensity of our economy by 20 to 25 percent by 2020 as compared to 2005. So, it implies that there has tobe greater energy efficiency and a greater amount of renewablepower in the grid in the year 2020 compared to 2005. Therefore, theinvestment in these kinds of technologies would have to beincreased, and it is increasing. Though, I cannot say if the increasewhich has happened till now or is happening now is adequate.Nonetheless, policy signals are making these kinds of investments ahigh priority.

Q10. As you said, it will be a combination of energy efficiencyand renewable power to achieve reduction in carbon intensity

of the economy by 2020. What new steps are you taking, and

what old steps are you accelerating, to achieve the energy

efficiency targets by 2020?

There is a long-standing programme to promote large hydro powerprojects and now the commitment to reduce emission intensity ofthe economy places a greater emphasis on accelerating thatprogramme. Also, the Electricity Act, 2003 provides that apercentage of electricity in each state should come from renewablesources, as set by the state regulators. This programme is already ineffect and would be further accelerated. We are already expectedto introduce renewable energy certificates, which would probably

accelerate the process even more. Through the PAT programme, weare seeking reduction in the heat rates and increase in energyefficiency in the existing power stations. As far as new investmentsin the power sector are concerned, we are increasingly movingtowards super critical technology in or der to increase theefficiency. Thus, it is the sum of all of these things which would leadto the carbon emission per unit of electricity to be lowered.

Q11. Supercritical technology is only for those power plants

which have a unit size of over 660 MW. What about those

plants that have small unit size of 150 MW or there about?

We are hoping that in the next few years, we would come to aposition where we would have a grid that is surplus in electricity, sothat the need for capacity addition through captive plants would

decline. Generally speaking, I see these small plants contributing avery small part, about 4-5 per cent, of the capacity addition. Thosereally wouldnt matter.



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Q12. Do you think that the LED lighting in India could become

economic viable soon?

First we transform the street lighting market and then move on toanother user sector where these will make a difference. In thismanner, we go on increasing the market volumes and bringingdown the prices so that these becomes cost effective muchsooner than these would have without such promotion.

Though it is a fact that the LEDs are more efficient than theCFLs, yet today their prices are much more than those of theCFLs. If a CFL costs about Rs 100, its LED equivalent costsanything between INR 600 and INR 700. Thus, the key issue isto bring the prices of the LED lighting down. When, the CFLswere introduced in India 25 years ago, they used to cost INR600-800. It has taken so many years to bring their price downto a level where people can afford those. Now, we want toaccelerate this process for the LEDs and, therefore, we havestarted looking at those applications where the LEDs areviable; for example, street lights. We are putting up demos invarious cities so that the municipalities and people can see forthemselves the amount of light produced by the LEDs, the costinvolved and the benefits and decide whether they could orderthe LED street lights instead of the high pressure sodium bulbsor the tube lights. So, first we transform the street lightingmarket and then move on to another user sector where these

will make a difference. In this manner, we go on increasing the

market volumes and bringing down the prices so that thesebecomes cost effective much sooner than these would havewithout such promotion.

Q13. The government has done a great job with BachatLamp Yojana. How is it going to be taken forward?

Bachat Lamp Yojana is now registered as a programme ofactivities and now the challenge is to complete a large numberof sub projects, which are known as CPAs, so that they cover aslarge a part of the county as soon as possible. In the last few

months, we have got enough projects to cover the entire Kerala.Today, every household in Kerala has CFLs, which have beenprovided as part of the Bachat Lamp Yojana. This programmeis in process in the Punjab and in the next couple of months, it would be completed there too. We will soon start it inKarnataka. Our goal is that in about a year and a half, a vastnumber of the households in the country would have movedfrom bulbs to the CFLs because of the Bachat Lamp Yojana.

Today, every household in Kerala has CFLs, which have beenprovided as part of the Bachat Lamp Yojana. This programmeis in process in the Punjab and in the next couple of months, it would be completed there too. We will soon start it inKarnataka. Our goal is that in about a year and a half, a vastnumber of the households in the country would have movedfrom bulbs to the CFLs because of the Bachat Lamp Yojana.


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Power Sector NewsGUJARATS MEGA POWER PROJECT SITES AT JAMNAGAR ANDJUNAGARH- FACE ENVIRONMENTAL HURDLES

Gujarat may have to be content with just one 4,000mw ultra mega

power project as the two other sites offered by the state forbuilding such projects have not been found feasible by the powerministry due to environmental reasons. The state had identified twosites- one near Junagarh and another near Jamnagarfor settingUMPPs of 4,000 mw capacity each.

Junagarh is not possible, as it is near the Gir Forest area, and as far asJamnagar is concerned, it is near the limestone mines andpermission from the Gujarat State Mining Corp would be required.

At present, the countrys largest private power producer, TataPower, is executing the 4,000 (800X5) mw UMPP at Mundra in thestate. The first 800 mw unit of this coastal projects is expected to be

thcompleted during the current 11 Plan period (2007-12).

Power Finance Corporation (PFC), the nodal agency for these kind

of projects, has already awarded four projects to the successfulbidders. Reliance Power bagged three of the allotted four projectsat Sasan (Madhya Pradesh), Krishnapatnam (Andhra Pradesh) andTilaiya (Jharkhand) while the Tatas won the Mundra Project.

The government, which plans to add 1,00,000mw of electricity inththe upcoming 12 Plan period (2012-17), is relying on the

contribution from these UMPPs. These projects are likely to becommissioned over a period of 4-5 years from now.

The invitation of preliminary bids for the two proposed projects atBedabahal (Orissa) and Sarguja (Chhattisgarh) are stuck because oflack of environment clearance for the coal blocks allotted to theprojects. Therefore, the Power Ministry would not finalise any othersite in any other part of the country without obtaining the mandatoryapprovals from the respective authorities.

CABINET NOD FOR PFC EPO

The Power Ministry would send a note to the Cabinet next week toreceive approval for raising about Rs. 7,000 crore through follow-onpublic offer of the state-run lending agency Power FinanceCorporation, which is likely to come during the first quarter of thenext financial year. The amount to be raised through the offer shallbe decided by an empowered group of ministers (EGOM) . Theoffer comprises 5% disinvestment of the governments share in PFCand raising of 15% fresh equity by the company. The marketcapitalization of PFC currently stands at Rs. 30.071 crore. Thegovernment currently holds 89.78% stake in the public sectorcompany. It had divested10% stake through an initial publicoffering (IPO) in 2007. After the proposed disinvestment, its stakemight go down to about 85%.

R-POWER PORJECT GETS NOD FOR CARBON CREDITS

Reliance Powers Rs.16,000-crore ultra mega power project at Sasanhas qualified for carbon credits, which will help it earn over Rs 2,000crore, or 40% of its equity in the next decade. The 4,000 MW coalfired Sasan power project using super critical technology has beenregistered with clean development mechanism executive board ofUnited Nations Framework Convention on Climate change. Thisallows the project to earn certified emission reduction credits, eachequivalent to one tone of carbon dioxide

Under clean development mechanism, less polluting projects indeveloping countries can earn certified emission reduction credits.Project developers can sell these credits to industrialized countriesto meet part of their emission reduction targets under Kyoto

Protocol.Sasan in the worlds largest power generation plant ever registeredwith the clean development mechanism executive board under

Clean Development Mechanism framework since its inception. Theproject will generate approximate 22.5 million carbon emissionreduction credits.

HYDEL POWER PLANTS CONSIDERED FOR REPRIEVEProposal is under consideration with the power ministry for a five- year exemption from tariff-based bidding regime for hydelprojects, while all coal-and gas fired projects move to the newregime from this year. The Central Electricity Authority has backedthe proposal. But some officials are opposing any reprieve onground that promoters were making substantial upfront premiumsto state governments for getting such projects.

The difference came to light at a recent meeting called by theministry to hear out private promoters of hydel projects. The CEAsaid the Central and State regulatory commissions should set thetariff for electricity from hydel projects on a cost-plus basis.

In a tariff-based bidding regime, projects are awarded to

promoters quoting the lowest electricity cost. This is believed tobring down project costs. In cost plus scenario, promoters areassured of a fixed return on their investments. This is, however,believed to protect inefficiency.

The CEA and promoters argue about the high degree ofuncertainties in comparison to thermal plants in hydel projects.Moving equipment and machinery poses a problem because oftheir locations in inaccessible terrain.

SOLAR POWER PROJECT LICENCES FOR SALE AT PREMIUM

The government had allotted 80 projects, ranging from 100 kilowatts to 2 MW, in 2010 under the Jawaharlal Nehru Solar Mission. Ithad offered to buy back solar power produced from these projectsat a generous Rs 18 per unit. There is no bar on transferring licensesunder the scheme.

Several companies that secured solar power projects from thegovernment are selling their licenses at a premium to bigger firms.

We have come across innumerable instances where companiesthat have been allotted solar power projects by the Centre nowwant to sell them off to other established players, said S P GonChoudhury, special secretary (power), West Bengal.

The tariff offered by the Centre makes it attractive even if thelicences are bought at a premium of Rs1-3 crore per MW. Officialssaid some potential buyers are already negotiating deals offering upto Rs 3 crore per MW.

With assured sales at attractive rates and money to be made fromcarbon credits, the established players in the solar energy domain

can afford to pay the premium. Some big companies are alsoseeking licenses to expand their operations.

Large firms that have bagged 2 MW- sized projects would want tohave around 10 MW to be a bigger player in this sphere, said anofficial at the ministry of renewable energy requesting anonymity.It is possible that these firms may be scouting for non-seriousplayers.

Another way of looking at these developments is a possibleconsolidation in market. It is possible that bigger companieswould buy out the smaller players. This would lead to market beingleft with 6-8 major developers, the official added.

Analysts say, with tariff for such power plants fixed at Rs 18 per unitby the Centre, a Rs 2-3 crore per MW of extra expenditure on solar

generation units would still be profitable for large players.The cost of setting up 1 MW of solar generation will be between Rs9-12 crore, said Samir Kanabar, Director infrastructure practice at



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Ernst &Young. The cost of generation of 1 unit of solar powervaries between Rs 15 and Rs 16. However, if the cost of setting up1 MW increases even by Rs 3 crore, and the tariff received is Rs 18per unit, the project still remains profitable.

Established players would also earn additional revenue fromcarbon credits, get tax holidays and avail accelerateddepreciation on equipment.

250 MW FIRST UNIT OF 1,000 MW JP POWER PROJECT IN

HIMACHAL PRADDESH IS SIX MONTHS, AHEAD OFSCHEDULE.

The first unit of the Rs 7,000-crore karcham-Wang-too hydroproject, the biggest hydropower plant to be commissioned inthe current five year plan, will start generating 250 mw ofelectricity by March 2011, and the other three would startfunctioning by June 2011, Suren Jain, Managing Director of thecompany said, Early commissioning of the project would helpthe company make use of the summer and monsoon period,when higher flow of water boosts hydroelectric generation. This will be the third hydroelectric project of Jai Prakash PowerVentures, part of the Jaypee Group. It had earlier built 300 MWBaspa project in Himachal Pradesh and 400 MW Vishnuprayagproject in Uttarakhand. Jai Prakash Power Ventures has tied up

with Power Trading Corporation of India to sell 80% of theelectricity produced at the Karcham-Wangtoo project. Theproject would generate 3.5 million carbon credits every year.

Company is getting a 25% return on equity on a sustainable basis.After having establish a presence in the hydropower sector thecompany has initiated its entry into thermal power generation,power transmission and also forayed into wind power.

The company plans to spend about Rs 45,000 crore by 2015 on various power projects including hydro power and thermalpower generation. The company had adequate funds for itsongoing projects this year but it may raise up to Rs 2,500 croreafter March 2012 for its expansion plans. The company aims toproduce 13,720MW of electricity by 2019 through a mix of hydroand thermal projects.

It plans to set up four thermal plans, two each in Uttar Pradesh andMadhya Pradesh by 2015. These plants together will generate 6,120 mw of power using super-critical technology.

REFUND OF SERVICE TAX TO EXPORTERS

New scheme to refund service tax to exporters is in the works asthe government seeks to neutralize all input taxes to enhancecompetitiveness of the country is export sector.

The finance ministry has set up an expert panel to work out themodalities of the scheme.

Refund of service tax has been a big irritant for exporters,

The new scheme is likely to be on the lines of the duty drawbackscheme under which exporters are reimbursed taxes paid oninputs at a fixed rate decided by an expert panel every yeardepending on changes in the tax rates.

An announcement could be made in the forthcoming budget onFebruary 28.

A task force appointed by the department of commerce alsomonetized transaction costs worth $12-15 billion, which was 7-10% of exports valued at $ 160-165 billion.

The total merchandise exports from India stood at $178.66 billionin 2009-10 and the government proposes to raise it to $200billion in the current fiscal.

Exporters in south East Asia and China face transactioncosts as low as 33.5% making their goods more competitive indeveloped markets compared with Indian exports.

Currently, the finance ministry refunds tax paid on 17 servicesconsumed in exports and two services are exempted. Serviceseligible for tax refund included banking and other financial services,port services, transport of goods by road and railways, generalinsurance, technical testing and analysis, storage and warehousingbusiness exhibition services and specialized cleaning services.Service tax on transport of goods by road and commission paid toforeign agents is exempted for exporters.

But experts say there is always a delay in getting refunds.The procedure is cumbersome and causes delay in the grant of therefund, said Anita Rastogi, Associate Director at PWC.

Though the finance ministry has made several attempts to simplifyprocedures related with refund of service tax paid on input servicesused in exports, administrative costs are high with tens of croreslocked in refunds.

For small exporters compliance costs is sometimes higher than therefund itself and there is huge pendency making matters worse.The idea now is not only to ensure that exporters cash does not staylocked with the government for an indefinite period, but also tosave them the hassle of going through paperwork every time theywant to claim an exemption.

Venugopal Calls for Minimising Transmission Losses 23-Feb-2011

Shri K.C.Venugopal, Minister of State for Power, has stressed on theneed for improving the performance in the power transmissionsector by minimizing the AT&C losses. During his meeting with Mr.Park Young-June, Vice Minister of Knowledge Economy, Republicof Korea who called on him here today , the Minister congratulatedthe Korean technocrats for achieving the minimized AT&C loss of4%, and expressed interest in knowledge sharing between the twocountries.

The Korean Minister has expressed Koreas interest in extendingtechnical support for improvement of energy efficiency systems inthe country. He also expressed interest in participating in the

Nuclear Power Development & augmenting non-conventionalenergy.

Nearly 90000 Villages & 1.5 Crore BPL Households ElectrifiedBenefiting 7 Crore poor people:

Shri Sushilkumar Shinde, Union Minister of Power has stressed theneed for ensuring that growing energy needs of the people are metby augmenting supply of green and clean energy in commerciallyviable and environmentally sustainable manner. Releasing a bookletHalf a decade of powering progress - the achievements of Ministryof Power during the past 5 years, here today, the Minister informedthat during the period from January, 2006 to January, 2011, theadditional capacity of over 50,000MW has been added which ismore than the capacity added in the previous decade. TheGovernment has also succeeded in fulfilling the dream of having,

One Nation One Grid, he added. To ensure that benefits of theincreased availability of electricity in rural areas, the implementationof Rajiv Gandhi Grameen Vidyutikaran Yojana has ensured that nearly90,000 villages and over 1.4 crore BPL households have beenelectrified benefiting over 7 crore poor people. Shri P. Uma Shankar,Secretary [Power], CMD [NTPC] and senior officials from the Ministryand various PSUs were also present on the occasion.

Addressing on the occasion, Shri P. Uma Shankar, Secretary [Power]stated that the power sector in the country is growing at anunprecedented pace as can be gauged from the fact that the year2009-10 saw a record addition in capacity of 9,585 MW for the firsttime ever in the history of the Indian power sector. The next 10months from April 2010 to January 2011, overshot that record byadding 10,210 MW, the highest capacity addition in a single year inthe last 60 years.

Implementation of the Availability Based Tariff [ABT] and itssubsequent tightening, particularly in May 2010, helped improve



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the quality of bulk power supply and reduced grid failures. Furthergiven its current depth, the national grid is no longer affected byminor system shocks. To improve the quality of power at thedistribution end, state utilities are being asked to install automaticpower factor correcting devices/ switched capacitors andpromote the use of Static VAR compensators and dynamic voltageregulators at customer installations to improve power quality, Shri P.Uma Shankar informed.

Earlier, the NTPC Ltd. presented an interim dividend of Rs.3.00 perequity share being 30% of the paid-up equity share capital of theCompany amounting to Rs.2,473.64 crore for the Financial Year2010-11. A cheque amounting to Rs.2,090.21 crore was presentedby Shri Arup Roy Choudhury, CMD [NTPC] to Shri SushilkumarShinde, Union Minister of Power in the presence of Shri P. UmaShankar, Secretary [Power] . This is the 18th consecutive year thatNTPC has paid dividend.

India Poised for Record Capacity Addtion of 15000 MW thisYear : Shinde-

Shri SushilKumar Shinde, Union Minister of Power has stated that thepower sector in the country is poised for record capacity additionof 1500MW duing the present financial year.Inaugurating theInternational O&M Event Indian Power Stations - 2011 to

commemorate the commencement of power generation fromNTPCs first unit at Singrauli [Uttar Pradesh] on same day in 1982 heretoday, he congratulated NTPC for its achievements. Shri Shinde saidthat after nearly thirty years of humble beginning, NTPC has a totalinstalled capacity of over 33000 MW and plans to be a 75000MWcompany by 2017. Shri K. C. Venugopal , Minister of State for powersituation in the country by supply of reliable and quality power to

jour janu feb 11

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