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SUBSTATION CAPACITORS IN REDUCING POWER LOSSES


What is the difference between substation capacitor and line capacitors?

If capacitors are installed primarily to reduce or eliminate bulk power charges for kVAR or for other reasons associated with wholesale purchased power such as contractual requirements, they can be installed in substations to supplement distribution line installations. Installed equipment cost for substation capacitors may be less than that for the same amount of line kVAR because the substation units can package many kVAR in a single installation and can be switched with a single three-phase switching device and control unit. However, the distributor does not get the benefit of reduced distribution line losses by installing capacitors at substations, so such installations should be made only after the maximum practical amount of line capacitors has been installed.

                      “Substation capacitors: To supplement, not replace distribution line capacitors.”

Problems can develop from the switching of substation capacitors if engineering and operations planning is inadequate. One possible problem is the production of a noticeable voltage spike when a large block of substation capacitors is switched at one time.

Another possible problem with substation capacitors is the disruption of capacitor switching control settings when one transformer is taken out of service in a two-transformer substation. The change in source impedance can cause a voltage-controlled capacitor switch with a narrow band width to switch on and off rapidly. Capacitor switching equipment has been known to fail violently under this condition. Avoidance of capacitor switching solely on voltage will eliminate this problem. If voltage controlled capacitors are used in two-transformer substations, the switching control should be placed on manual during maintenance work when one transformer is taken out of service.

                                                 Technical Requirements Of Capacitor Bank
                                                Data To Be Submitted With Request for Quote

1. Bank voltage ________kV

2. Frequency _________HZ

3. Bank Capacitance: ________Initial ________Future

4. Bank KV-BIL: ________

 5. Connection _____Grounded _____Ungrounded Wye

6. Capacitor mounting _____Horizontal _____Vertical

7. Fusing _____Expulsion _____Current limiting

8. Bushing creepage: _____10" _____18" _____22" _____26"

9. Elevating structure: _____Ht. in inches

10. Temp Range: _____Min _____Max

11. Unbalanced scheme to be supplied with tender: ___Yes ___No

12. Describe any unusual service conditions.


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