Corrective device protection
A control system for an electrical power system includes an electrical corrective device, a voltage measuring device coupled to each phase of the electric power system, a current measuring device connected between each phase of the electric power system and the electrical corrective device, and a protective device connected to outputs of the voltage measuring device and the current measuring device. The protective device includes a controller configured to detect an imbalance using the measured voltages and currents output from the voltage measuring device and the current measuring device without using or independently of other recent voltage or current measurements for other points in the electrical corrective device and independently of a neutral-ground measurement at the electrical corrective device.
1. A method comprising:
measuring a voltage of each phase of a multi-phase electric power system;
measuring a current between each phase of the multi-phase electric power system and an electrical corrective device; and
determining whether an imbalance exists in the electrical corrective device using the measured voltage and the measured current, the determination being independent of a voltage across a component included in the electrical corrective device and independent of a neutral-ground measurement at the electrical corrective device.
2. The method of claim 1 , wherein the electrical corrective device includes a reactor bank.
3. The method of claim 1 , wherein the electrical corrective device includes a capacitor bank.
4. The method of claim 1 , wherein determining whether an imbalance exists comprises determining a negative-sequence current using the measured values and comparing the negative-sequence current with a predetermined negative-sequence current calculated for an undamaged electrical corrective device.
5. The method of claim 1 , wherein the electrical corrective device is shunt connected.
6. The method of claim 5 , wherein the electrical corrective device is ungrounded.
7. The method of claim 6 , wherein the electrical corrective device includes a bank of elements that are arranged in a wye configuration.
8. The method of claim 1 , wherein the electrical corrective device is ungrounded.
9. The method of claim 1 , wherein the electrical corrective device is grounded.
10. The method of claim 1 , wherein an imbalance exists in the electrical corrective device, and further comprising activating a switching device configured to isolate the electrical corrective device from the electric power system.
11. The method of claim 1 , wherein determining whether an imbalance exists includes compensating for errors in the measured voltage and measured current due to ambient temperature changes.
12. The method of claim 1 , wherein an imbalance exists in the electrical corrective device, and further comprising determining in which phase the imbalance occurs.
13. The method of claim 1 , wherein the electrical corrective device is connected to a multi-phase high-voltage bus of the electric power system, the electrical corrective device includes multiple interconnected individual capacitive or reactive components, and determining whether an imbalance exists is independent of a voltage across one or more of the interconnected components included in the electrical corrective device.