Power Factor correction of Toitskraal 11kV feeder

Power Factor Correction

of

Toitskraal 11kV feeder

Kruger Greyvenstein

Project initiator: Sydney Mamosadi

1 July 2014

2

CONTENT

• Introduction

• Background

• Problem Statement

• Solution

• Specifications

• Scope of work

• Simulations & Results

• Costing

• Return on investment

• Conclusion

• Recommendations

Kruger Greyvenstein

3

Introduction

• Some lines on our Distribution Networks have bad power factors, meaning they have a lot of inductive loads and therefore consumes a lot of reactive energy.

• The reactive energy must be supplied from the source (which in Dx case is Tx) and be transmitted through our network. The effect of the reactive energy on our networks are:

• Higher line loading (Higher reactive currents)

• Increased voltage drop across lines.

• More technical losses

• Shorten lifetime of apparatus such as TRF’s

• The idea is to minimize the reactive power as much as possible

Kruger Greyvenstein

4

Background

Project: Power factor correction of the 11kV Toitskraal feeder:

Substation Background:

•Toitskraal 22/11kV substation.

•It is equipped with 3 × 5MVA 22/11kV TRF’s

•3 × 22kV incoming feeders: Marble Hall 1, Marble Hall 2 and Valschfontein

•2 × 11kV outgoing feeders: Toitskraal & Elandsdrift

Kruger Greyvenstein

5

Background:

Kruger Greyvenstein

Toitskraal sub

6

Background:

Kruger Greyvenstein

7

Problem Statement:

11kV Toitskraal feeder:

•The Feeder have an peak load power factor of 0.78 (lagging)

•The backbone close to the substation is overloaded at certain points during peak loading

•The line is feeding an agricultural area

•Loads mostly consists of pumps and center pivot irrigation systems

• Motors used in those implements are one of the main reasons for high reactive energy consumption.

Kruger Greyvenstein

8

Problem Statement:

Kruger Greyvenstein

Toitskraal

9

Problem Statement:

Phasor Diagram:

Kruger Greyvenstein

38°

PF = 0.78

10

Problem Statement:

PF correction requirements:

•MV 90 data. Period: (01/03/2013 – 01/03/2014):

According to the standard: Network Planning Guideline for Shunt Capacitors, power factor correction is necessary if:

•PF < 0.85

•Qmax ≥ 300 kVAr

•Qmin ≥ 150 kVAr

Kruger Greyvenstein

P (KW) Q (KVAr) S (KVA)

max 3670 2600 4500

min 750 300 900

average 1368.949 1038.212 1757.675

Requirements for PF correction

11

Solution

• Static VAr Compensators

• Capacitor bank inside the substation

• Pole mounted Shunt Capacitor banks

Kruger Greyvenstein

12

Solution

Best option:

Is to install Pole mounted Shunt Capacitor banks on the feeder for power factor correction.

Advantages:

•Reduce voltage drop on the feeder

•Pole mounted Capacitors supply reactive energy close to the load.

•Reduce the KVAr as well as the KVA from the source

•Reduce loading on lines, and transformers

•Reduce losses on MV network as well as HV network

•In a substation with multiple MV feeders, if one pole mounted cap bank fail, the effect is minimal. If there is one cap bank on the busbar of a substation and it fails, then everything is lost.

Kruger Greyvenstein

13

Cap bank

Kruger Greyvenstein

Source(Sub)

14

Solution

MV Pole mounted switched shunt capacitor bank

Kruger Greyvenstein

15

Specifications

1) Capacitor bank Type:

Two types:

1. Fixed Capacitor banks

2. Switched Capacitor banks

A Combination of the two types will be used:

• A Fixed shunt Capacitor bank for compensation of the low loading period.

• A Switched shunt Capacitor bank can switch in at a certain level to help compensate for the High Loading period.

Kruger Greyvenstein

16

Specifications

2) Capacitor bank sizes:

Low Loading compensation:

•Use 1 × 500 kVAr, fixed capacitor bank for low load compensation.

Peak load compensation:

•Use 1 × 750 kVAr, switched capacitor bank for Peak load compensation.

Kruger Greyvenstein

17

Specifications

3) Capacitor bank location:

•A shunt capacitor bank must be installed as close as possible to the load for max effectiveness.

•On an MV feeder with a lot of loads (evenly distributed) the placement can be as follow:

• Qfixed – Approximately half way down the feeder

• Qswitched – Approximately 2/3 down the feeder

•The capacitor banks are placed such to have the best possible effect on the voltage profile.

Kruger Greyvenstein

18

Specifications

Kruger Greyvenstein

Capacitor Bank -

1 (Fixed)

3 (switched)

19

Scope of Work

• Install 1 × 500 KVAr, 11kV Pole mounted fixed shunt capacitor bank on pole number TOT44

• Install 1 × 750 KVAr, 11kV Pole mounted switched shunt capacitor bank on pole number TOT54/21

• Install pole mounted capacitor banks on existing pole structures

• Connect capacitor banks in parallel with overhead lines

Kruger Greyvenstein

20

Simulations & Results

Toitskraal 11kV feeder Load Profile:

High Loading Scenario: S = 4500 KVA

Low Loading Scenario: S = 600 KVA

Kruger Greyvenstein

21


Toitskraal 11kV feeder Load Profile:

High Loading Scenario: S = 2600 KVA

Low Loading Scenario: S = 300 KVA

Kruger Greyvenstein

22


Voltage Profiles:

Peak Loading:

Existing Voltage Profile: New Voltage Profile:

Kruger Greyvenstein

Distance (km) Distance (km)

1.05

0.95

1.05

0.95

23


Effect of switched Cap bank:

Just before switching: Just after switching:

Max voltage rise = 1.66 %

Kruger Greyvenstein

Voltage rise ≤ 5 % ???

24


Worst case voltage rise:

Load = 0.2 MVA with the fixed capacitor bank in service

Kruger Greyvenstein

1.05

0.95

25


Line Loadings: (Peak load)

Existing: After cap bank installation:

Kruger Greyvenstein

Line Loadings Total Apparent Power

% MVA

110.2685 4.500961

99.67498 4.066381

61.28087 1.773238

58.49818 1.691852

56.07303 2.280289

55.5811 2.240934

55.57835 2.255222

54.83763 2.172903

54.8356 2.179777

41.62442 1.688606

31.73271 1.286541

31.24099 1.26635

27.50092 1.108903

Line Loading Total Apparent Power

% MVA

93.10929 3.800553

82.91329 3.38289

61.23579 1.773208

58.4551 1.691823

43.14478 1.755841

42.73481 1.729538

42.73446 1.736708

42.12045 1.685888

42.12024 1.689293

41.59377 1.688581

31.70923 1.286519

31.21788 1.266329

27.48053 1.108891

26


Effect of capacitor banks on Load Profile:

Saving of 700kVA at peak load.

Kruger Greyvenstein

Min Load

Max Load

Switched Cap bank switches in

27


Technical losses:

High Loading:

Kruger Greyvenstein

Total technical losses saved =

26.42kW

Before After: Saved:Total Losses (kW) Losses (total) (kW) Losses (kW)

0.78677 0.47264 0.31413 26.4 kW0.29626 0.17797 0.1182910.2697 6.10054 4.16916

39.27777 23.62674 15.65103 1030.831 0.51671 0.31429 76.6

1.79652 1.10541 0.691113.89029 2.32922 1.561073.92558 2.35474 1.570847.60112 4.55907 3.042051.09612 0.67443 0.421690.62016 0.61774 0.002420.37412 0.44714 -0.073027.45818 8.90733 -1.44915

1.1766 1.50331 -0.326715.44805 5.42675 0.02130.47577 0.47391 0.001862.18447 2.1759 0.008570.33384 0.33253 0.001311.61049 1.60416 0.006330.25054 0.24956 0.00098

0 0.02758 -0.027580 0.02666 -0.026660 0.02654 -0.02654

2.83566 1.84561 0.990050.09286 0.07835 0.014510.12125 0.10229 0.018960.09257 0.08147 0.01110.28011 0.27112 0.008990.24497 0.26479 -0.019820.17485 0.32183 -0.146980.15182 0.18643 -0.034611.09164 1.43769 -0.346050.11045 0.17007 -0.05962

Total Losses saved =

Losses Before =Losses After =

28

Costing:

Kruger Greyvenstein

Microsoft Excel 97-2003 Worksheet

29

Return on investment:

• Because there is a return on the investment, the Total costing of the project can be worked backed in time because of the saving:

• 700 kVA will be saved during peak loading

• The reduced load will free up capacity for additional customers on the feeder

• Extend the lifetime of apparatus for ex. TRF’s

• The technical losses will be reduced with 26.4 kW during peak loading

• The customer will still pay exactly the same; the saving will be only on ESKOM’s side.

Kruger Greyvenstein

30


Annual Technical losses saving:

Kruger Greyvenstein

31


Annual Reactive Energy saving:

Kruger Greyvenstein

C:\Users\GreyveJK\Documents\1) Work\1) EI

32


Total annual project saving:

•The total project cost can be worked back in 4.65 months.

Kruger Greyvenstein

33

Conclusion

• Power factor correction of this feeder results in a better optimized network

• The installation of Shunt Capacitor Banks on this MV feeder have multiple advantages on the network

• It can serve as a perfect temporary solution for the overloading and under voltages, but must be used as a permanent solution for bad power factors

• A whole lot of money can be saved by implementing this project (± 3 Million per year) after the project cost is worked back

• If power factor correction can be done for all our MV feeders ESKOM can save a lot of money

Kruger Greyvenstein

34

Recommendations

• As Harmonics on the network presents significant risk to capacitors, an independent Harmonic recording is essential before the capacitor banks be installed.

• Before implementing this project do power factor correction of the Toitskraal – Elandsdrift 11kV feeder as well. Otherwise the capacitor banks on the Toitskraal feeder will supply the Elandsdrift feeder as well which means that the desired effect on the Toitskraal fdr won’t take place.

Kruger Greyvenstein

Thank you

36

Cap bank

Kruger Greyvenstein

Source(Sub)

37


Fault levels:

Kruger Greyvenstein

Single Phase: 3 - Phase:

11kV 22kV 11kV 22kV

Min 3.25 2.447 5.04 7.67

Max 3.258 2.46 5.06 7.87

38


Toitskraal 11kV fdr Load Profile:

Kruger Greyvenstein

39


Load Profile:

Kruger Greyvenstein

40

Introduction

Kruger Greyvenstein

41

Specifications

High Loading compensation:

•Use 1 × 750 KVAr, switched capacitor banks for high load compensation, at two different locations on the feeder.

Kruger Greyvenstein

42

Scope of work

1) Capacitor bank Type:• Fixed shunt Capacitor bank (Pole Mounted):

• Switched shunt Capacitor bank:

1) Fixed Capacitor bank (Pole Mounted):

Kruger Greyvenstein

Advantages Disadvantages

• Space efficient (pole mounted)

• Not expensive

• Easy installation (single pole structure)

• Low installation cost (single pole structure)

• Low maintenance

• Can’t switch in and out automatically

• May result in overcompensation during low loading periods resulting in over voltages and increased system losses

43

Scope of work

2) Switching Capacitor bank (Pole mounted):

Kruger Greyvenstein

Advantages Disadvantages• Sufficient compensation during high

loading periods

• Reduce compensation during low loading periods to prevent overcompensation.

• Automatically switch capacitors in and out to maintain PF limits

• Space efficient (pole mounted)

• Low installation cost (single pole structure)

• Low maintenance

• More expensive

• More complicated installation

44

Scope of work

Conclusion:

A Combination of the two can be used:

•A Fixed Capacitor bank for compensation of the low loading period.

•A Switched Capacitor bank can switch in at a certain level to help compensate for the High Loading period.

All formulas is according to the standard: Network Planning Guidelines for shunt capacitors

Kruger Greyvenstein

45


Voltage Profiles:

High Loading:

Existing Voltage Profile: New Voltage Profile:

Kruger Greyvenstein

1.05

0.95 0.95

1.05

Power Factor correction of Toitskraal 11kV feeder

Documents

Transcript of Power Factor correction of Toitskraal 11kV feeder