2. 2
CONTENT
• Introduction
• Background
• Problem Statement
• Solution
• Specifications
• Scope of work
• Simulations & Results
• Costing
• Return on investment
• Conclusion
• Recommendations
Kruger Greyvenstein
3. 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. 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
7. 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
10. 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
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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
Requirements for PF
correction
11. 11
Solution
• Static VAr Compensators
• Capacitor bank inside the substation
• Pole mounted Shunt Capacitor banks
Kruger Greyvenstein
12. 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
15. 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. 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. 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
19. 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. 20
Simulations & Results
Toitskraal 11kV feeder Load Profile:
High Loading Scenario: S = 4500 KVA
Low Loading Scenario: S = 600 KVA
Kruger Greyvenstein
21. 21
Simulations & Results
Toitskraal 11kV feeder Load Profile:
High Loading Scenario: S = 2600 KVA
Low Loading Scenario: S = 300 KVA
Kruger Greyvenstein
22. 22
Simulations & Results
Voltage Profiles:
Peak Loading:
Existing Voltage Profile: New Voltage Profile:
Kruger Greyvenstein
Distance (km)Distance (km) Distance (km)Distance (km)
1.051.05
0.950.95
1.051.05
0.950.95
23. 23
Simulations & Results
Effect of switched Cap bank:
Just before switching: Just after switching:
Max voltage rise = 1.66 %
Kruger Greyvenstein
Voltage rise ≤ 5 % ???Voltage rise ≤ 5 % ???
24. 24
Simulations & Results
Worst case voltage rise:
Load = 0.2 MVA with the fixed capacitor bank in service
Kruger Greyvenstein
1.051.05
0.950.95
25. 25
Simulations & Results
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. 26
Simulations & Results
Effect of capacitor banks on Load Profile:
Saving of 700kVA at peak load.
Kruger Greyvenstein
Min LoadMin Load
Max LoadMax Load
Switched Cap
bank switches in
Switched Cap
bank switches in
29. 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
32. 32
Return on investment:
Total annual project saving:
•The total project cost can be worked back in 4.65 months.
Kruger Greyvenstein
33. 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. 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
42. 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. 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. 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. 45
Simulations & Results
Voltage Profiles:
High Loading:
Existing Voltage Profile: New Voltage Profile:
Kruger Greyvenstein
1.051.05
0.950.95 0.950.95
1.051.05
Editor's Notes
All the many circles are an indication of the many center pivot irrigation systems each containing many motors/pumps.
Al die tegniese besluite: wat/waar/hoe instaleer
Al die tegniese besluite: wat/waar/hoe instaleer
Al die tegniese besluite: wat/waar/hoe instaleer
Al die tegniese besluite: wat/waar/hoe instaleer
If the load would drop to 0.2 MVA, which is highly unlikely but possible, the voltage profile will look like this. Still within the limits. There won’t be a rapid voltage change because at this stage only the fixed cap bank will be in service and it is permanently in service. There won’t be any switching.
The graph illustrates what influence the cap bank will have on the load when the load grows from it’s lowest value all the way to it’s peak value. The fixed cap bank will permanently be in service; that is why the new load is lower since the start. When the switched cap bank switches in later the load drops even further.
