Electric Power Distribution Handbook, T. A. Short

7. Capacitor Application

Questions

  1. Substation capacitor banks: (mark all that apply)

    1. Are cheaper than the equivalent amount of capacitor banks installed on a feeder
    2. Reduce feeder losses
    3. Help reduce feeder voltage drop

  2. A capacitor will raise the voltage upstream of the bank.

    1. True
    2. False

  3. Reactive power is due largely to which of the following:

    1. Motors
    2. Electronic loads
    3. Transformers
    4. Cables

  4. If a feeder has 1000 kvar of load, what would be the optimal size of each cap bank if two capacitors are applied at optimal locations?

    1. 200 kvar
    2. 333 kvar
    3. 400 kvar
    4. 667 kvar
    5. 1000 kvar

  5. Voltage drop due to a large resistive heating load can be reduced by switching in a capacitor bank.

    1. True
    2. False

  6. Line losses due to a large resistive heating load can be reduced by adding a capacitor bank.

    1. True
    2. False

  7. Is an 80 K fuse link an acceptable application on 900-kvar bank on a 12.5-kV system.

    1. Yes
    2. No

  8. Which options can minimize the likelihood of nuisance fuse operations on capacitor cutouts? Mark all that apply.

    1. Tighten fuseholder caps
    2. Use conductive grease
    3. Replace the fuse liner when needed
    4. Do not fuse too tightly

Problems

  1. What is the voltage rise after adding a 3-phase, 3-Mvar capacitor bank (12.5 kV, 3-phase short circuit at the point = 2 kA, X/R=4)?

  2. Consider a 12.5-kV express circuit that is four miles long with 350-kcmil AAC construction with Z1 = 0.0557 + j 0.1242 ohms/kfeet. Find the amount of capacitance in kvar needed to have zero voltage drop.

  3. For a 1200-kvar capacitor bank on a 12.5-kV distribution circuit, calculate the I2t for peak outrush into a nearby fault where the resistance between the capacitor and the fault is 0.02 ohms. Find Vpu needed to for the I2t to exceed that necessary to blow a 30T fuse.

Projects

  1. Using the IEEE 8500-node test case in OpenDSS, find the losses for each of the following cases. Solve the system at peak load.

    • Base case.
    • Remove all capacitors.
    • Add 1200-kvar fixed capacitors based on the 1/2-kvar method.
    • Add 600-kvar fixed capacitors based on the 1/2-kvar method.


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To the extent possible under law, Tom Short has waived all copyright and related or neighboring rights to these study questions. This work is published from the United States. Please use this material however you want.