Electrical protection system
Protection systems for electrical systems such as substation power dividers are described. The protection systems may be designed and used to detect and clear faults that may occur within the substation power dividers. For example, a first Rogowski coil may be used to detect current along a primary conductor, and output a corresponding current signal to a multi-function, differential relay having multiple voltage and current inputs. Similarly, additional Rogowski coils may be used at each of a plurality of secondary feeders, where power from the primary feeder may be distributed to the secondary feeders using a connection bus. By comparing the signals from the first Rogowski coil and the additional Rogowski coils, the differential relay may determine whether a fault exists at some point along the conductor(s) and between the first Rogowski coils and the additional Rogowski coils, including whether a fault is associated with the connection bus. Further, the relay may then, in response to the fault, trip a circuit breaker or other network protection device, so that the fault may be corrected.
1. An electrical protection system comprising:
a first Rogowski coil associated with a primary feeder of an electrical system and operable to sense a primary current in the primary feeder;
a first protection device operable to receive a first current signal from the first Rogowski coil;
secondary Rogowski coils, each associated with a corresponding secondary feeder of the electrical system and operable to sense a corresponding secondary current in the secondary feeder;
secondary protection devices, each operable to receive a secondary current signals from an associated secondary Rogowski coil; and
a communication link operable to transmit the first current signal and the secondary current signals between the first protection device and the secondary protection devices.
2. The system of claim 1 wherein the first protection device and the secondary protection devices include differential relays.
3. The system of claim 1 wherein the first protection device is operable to determine that a fault associated with the electrical system exists based on the first current signal and the secondary current signals.
4. The system of claim 1 further comprising a connection bus connecting the primary feeder to each of the secondary feeders.
5. The system of claim 4 wherein the first protection device is operable to determine that a fault associated with the connection bus exists based on the first current signal and the secondary current signals.
6. The system of claim 4 wherein the communication link includes peer-to-peer connections between the first protection device and the secondary protection devices.
7. The system of claim 4 wherein the communications link includes connections from the first protection device and the secondary protection devices to a centralized computing resource.
8. The system of claim 1 wherein each of the secondary protection devices provides overcurrent protection to its respective secondary feeder based on its respective secondary current signal.
9. The system of claim 8 wherein a first one of the secondary protection devices is associated with a first one of the secondary feeders and is connected to a second one of the secondary Rogowski coils that is associated with a second one of the secondary feeders to thereby provide back-up protection to the second one of the secondary feeders.
10. The system of claim 1 further comprising:
a second Rogowski coil associated with the primary feeder and operable to sense a second primary current in the primary feeder; and
a second protection device operable to receive a second current signal from the second Rogowski coil,
wherein the first protection device determines an existence of a fault associated with the primary feeder based on the first current signal and the second current signal.
11. The system of claim 1 wherein, by using the communications link, a first one of the first protection device and the secondary protection devices acts as a backup to a second one of the first protection device and the secondary protection devices upon determining that the second one of the first protection device and the secondary protection devices is inoperable.
12. The system of claim 1 further comprising:
a first analog-to-digital converter connected to the first Rogowski coil and operable to output the first current signal as a first digital output; and
secondary analog-to-digital converters, connected to respective ones of the secondary Rogowski coils and operable to output the secondary current signals as secondary digital outputs.
13. The system of claim 12 wherein:
the communications link includes a centralized computer resource operable to input the first digital output and the secondary digital outputs, and
the first protection device and the secondary protection devices receive the first digital output and the secondary digital outputs from the centralized computer resource.
14. A method of protecting an electrical system, the method comprising:
measuring a primary current in a primary feeder of an electrical system using a first Rogowski coil;
receiving at a first protection device, a first current signal generated by the first Rogowski coil;
measuring secondary currents in secondary feeders using corresponding secondary Rogowski coils;
receiving secondary current signals that are generated by the secondary Rogowski coils at corresponding secondary protection devices; and
transmitting the first current signal and the secondary current signals between the first protection device and the secondary protection devices using a communications link.
15. The method of claim 14 wherein the first protection device and the secondary protection devices include differential relays.
16. The method of claim 14 further comprising determining, at the first protection device, that a fault associated with the electrical system exists based on the first current signal and the secondary current signals.
17. The method of claim 14 further comprising determining, at the first protection device, that a fault associated with a connection bus exists, based on the first current signal and the secondary current signals, wherein the connection bus connects the primary feeder to each of the secondary feeders.
18. The method of claim 14 wherein transmitting the first current signal and the secondary current signals comprises using peer-to-peer connections between the first protection device and the secondary protection devices.
19. The method of claim 14 wherein transmitting the first current signal and the secondary current signals comprises transmitting the first current signal and the secondary current signals between the first protection device and the secondary protection devices through a centralized computing resource.
20. The method of claim 14 further comprising having each of the secondary protection devices provide overcurrent protection to its respective secondary feeder based on its respective secondary current signal.
21. The method of claim 20 further comprising:
associating a first one of the secondary protection devices with a first one of the secondary feeders, and
connecting the first one of the secondary protection devices to a second one of the secondary Rogowski coils that is associated with a second one of the secondary feeders to thereby provide back-up protection to the second one of the secondary feeders.
22. The method of claim 14 further comprising:
measuring a second primary current in the primary feeder using a second Rogowski coil;
inputting a second current signal generated by the second Rogowski coil into a second protection device; and
determining, using the first protection device, that a fault associated with the primary feeder exists based on the first current signal and the second current signal.
23. The method of claim 14 further comprising:
outputting the first current signal as a first digital output from a first analog-to-digital converter connected to the first Rogowski coil; and
outputting the secondary current signals as secondary digital outputs from secondary analog-to-digital converters connected to respective ones of the secondary Rogowski coils.
24. The method of claim 23 further comprising inputting the first digital output and the secondary digital outputs at a centralized computer resource associated with the communications links, wherein the first protection device and the secondary protection device input the first digital output and the secondary digital outputs through the centralized computer resource.