case study - line capacitors - msedcl

7/29/2019 Case Study - Line Capacitors - MSEDCL

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Content Page Nos

1. Introduction 3

2. Scheme 5

3. Implementations 6

4. Results 7

5. Cost Benefit Analysis 8

6. Lessons Learnt and Conclusions 97. Guidelines for Repeatability in other Distribution Areas 9

- Benefits

- Challenges

- Key Pitfalls/precautions


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1. INTRODUCTION

Reactive power compensation is defined as the management of reactive power toimprove the performance of alternating-current (ac) power systems. In general, theproblem of reactive power compensation is related to load and voltage support. In loadsupport the objectives are to increase the value of the system power factor, to balancethe real power drawn from the ac supply, to enhance voltage regulation, and toeliminate current harmonic components produced by large and fluctuating nonlinearindustrial loads. Voltage support is generally required to reduce voltage fluctuation at agiven terminal of a transmission line. Reactive power compensation in transmissionsystems also improves the stability of the ac system by increasing the maximum activepower that can be transmitted.

In electric power distribution system, most of the electrical equipments connectedrelease certain amount of reactive power in the network. Thus the electricallines/feeders carry active power as well considerable amount of reactive power. Unliketrue power, reactive power is not useful power because it is stored in the circuit itself.

In electric power distribution, shunt capacitors are used for power factor correction.Such capacitors often come as three capacitors connected as a three phase load.Usually, the values of these capacitors are given not in farads but rather as a reactivepower in volt-amperes reactive (VAr). The purpose is to counteract inductive loadingfrom devices like electric motors and transmission lines to make the load appear to bemostly resistive. The advantages of installation of these capacitors are as below:

Reactive component of the network is reduced and so also the total current in thesystem

I2R power losses are reduced in the system because of reduction in current

Voltage level at the load end is increased

KVA loading on the source generators as also the transformers and lines uptothe capacitors reduces giving capacity relief. A high power factor can help inutilizing the full capacity of your electrical system

When reactive power is provided only by power plants, each system components (i.e.,

generators, transformers, transmission lines and distribution feeders, switch-gear, andprotective equipments) has to be increased in size accordingly. Capacitors can mitigatethese conditions by decreasing the reactive power demand all the way back to thegenerators. Line currents are reduced from capacitors locations all the way back to thegeneration equipment. As a result, losses and loadings are reduced in distributionsfeeders, substation transformers, and transmission lines. Depending upon theuncorrected power factor of the system, the installation of shunt capacitors can increasegenerator and substation capability of additional load at least 30 percent, and canincrease individual circuit capability, from the voltage regulation point of view,approximately 30 to 100 percent. Furthermore, the current reduction in transformer anddistribution equipment and lines reduces the load on these kilovolt ampere-limitedapparatus. In general, the economic benefits force capacitor banks to be installed on the


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primary distribution network rather than on the secondary. The methods used by the

utilities to determine the economic benefits derived from the installation of capacitorsvary from company to company, but the determination of the total installed cost of akilovar of shunt capacitors is easy and straightforward. In general, the economic benefitsthat can be derived from capacitor installation can be summarized as:

Benefits due to released generation capacityBenefits due to released transmission capacityBenefits due to released distribution substation capacityBenefits due to reduced voltage drops (voltage improvement)Benefits due to released feeder capacityBenefits due to reduced energy losses


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2. SCHEME

At the time of preparation of DPR of DRUM Project for MSEDCLs Aurangabad Urban DivisionNo.I, there were 41 Nos. of 11 KV Feeders catering the load of the area. Out of them, sample 6nos of feeders listed below from different localities were chosen for installation of switchedCapacitor Banks of 0.6 MVAR capacity. They are tabulated below

Sr.No Name of 11 KVFeeder

Name of S/S from whichemanating

Remarks

1 Aurangpura 33/11 KV Power House Mainly catering residential,commercial, industrial and

street lighting loads inurban area

2 Cantonment 33/11 KV Chhawani Mainly catering residential,commercial, industrial andstreet lighting loads inurban area

3 Residential 132/11 KV Waluj Mainly catering residential,commercial, industrial andstreet lighting loads inurban area

4 Town-8 132/11 KV Harsool Catering residential,commercial, industrial,street lighting loads andagricultural pumping load.

5 Golwadi 33/11 KV Railway Station Catering residential,commercial, industrial,street lighting loads andagricultural pumping load

6 Kanchanwadi 33/11 KV Railway Station Catering residential,commercial, industrial,street lighting loads and

agricultural pumping load

In order to reduce the line losses and to improve the line efficiency, installation of switchedcapacitor banks of 0.6 MVAR capacity on the above feeders is envisaged in the DPR of DRUMProject. This exercise is on sample basis. Switched capacitors are proposed since the loads onthese feeders vary during the period of 24 hours daily.

The equipment consists of a set of 3 capacitor units each of 0.2 MVAR capacity connected toeach phase. A vacuum contactor switch of 11 KV, 400 Amp rating suitable for 50 Amp ofcapacitive current is provided for on-load switching on and off the capacitor. The control is based


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on self powered controller placed in the switch, which offers excellent performance under differentvoltage and current levels.

3. IMPLEMENTATION

The work of installation of the capacitor banks on above mentioned six 11 KV feeders was carriedout by M/s L & T Ltd. through turnkey contract at a total cost of Rs 18.997 Lakhs as against theDPR estimated cost of Rs 15.445 Lakhs.

The 11 KV capacitor bank along with automatic power factor control switch is mounted on doublepole structure as can be seen in the picture given below:


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4. RESULTS

The data of all 6 feeders on which the capacitor banks were installed is as below:

SrNo

Particulars ResidentialFeeder

CantonmentFeeder

Town-8Feeder

GolwadiFeeder

KanchanwadiFeeder

AurangpuraFeeder

Remarks

1 Line currentwithoutcapacitorbank

150 Amps 130 Amps 100Amps

60Amps

60 Amps 105 Amps

2 Line currentwith capacitor

bank


48Amps

46 Amps 89 Amps

3 Reduction incurrent


12Amps

14 Amps 16 Amps

4 Percentagereduction incurrent

11.33% 14.61% 18.00% 20.00% 23.33% 15.24%

5 Power Factorwithoutcapacitorbank

0.85 0.87 0.83 0.83 0.80 0.85

6 Power Factorwith capacitorbank

0.95 0.95 0.93 0.94 0.92 0.95

7 Percentageimprovementin P.F.

11.76% 9.20% 12.05% 13.25% 15.00% 11.76%

It can be seen from the above that reduction in current is about 11-15 percent in feeders cateringto purely urban localities and 18-23 percent in feeders catering to urban-cum-rural localities.


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5. COST BENEFIT ANALYSIS

The monetary benefit derived from installation of the capacitors can be calculated by evaluating

total reduction in energy losses i.e. energy saved. The benefits available in the distriburionsystem is only considered as the transmission network is not owned by Mahadiscom. Thecalculations are tabulated below:

SlNo

Particulars ResidentialFeeder

CantonmentFeeder

Town-8Feeder

GolwadiFeeder

KanchanwadiFeeder

AurangpuraFeeder

1 Line current withoutcapacitor bank in Amps

150 130 100 60 60 105

2 Line current with

capacitor bank in Amps

133 111 82 48 46 89

3 Current Reduction inAmps

17 19 18 12 14 16

4 P.F. Without capacitorbank

0.85 0.87 0.83 0.83 0.80 0.85

5 P.F. With capacitorbank

0.95 0.95 0.93 0.94 0.92 0.95

6 Demand withoutcapacitor bank in KVA

2858 2477 1905 1143 1143 2000

7 Demand with capacitorbank in KVA

2534 2115 1562 914 876 1696

8 Reduction in KVADemand

324 362 343 229 267 304

9 % Reduction in Demand 11.34 14.61 18.00 20.03 23.36 15.20

10 Type of Line conductor ACSRWeasel

ACSR Mink ACSRMink

ACSRWeasel

ACSRWeasel

ACSRWeasel

11 Length of Line in KMs 6.0 3.0 4.5 4.0 7.0 4.3

12 Energy loss reductionon 11 KV side per dayin KWH

631.13 150.34 161.34 113.34 227.12 291.82

13 Saving per day takingaverage Powerpurchase rate as Rs.2.30

1451.59 345.78 371.07 260.69 522.38 671.19


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case study - line capacitors - msedcl

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