Modular FACTS devices with external fault current protection
Flexible AC transmission system (FACTS) enabling distributed controls is a requirement for power transmission and distribution, to improve line balancing and distribution efficiency. These FACTS devices are electronic circuits that vary in the type of services they provide. All FACTS devices have internal circuitry to handle fault currents. Most of these circuits are unique in design for each manufacturer, which make these FACTS devices non-modular, non-interchangeable, expensive and heavy. One of the most versatile FACTS device is the static synchronous series compensator (SSSC), which is used to inject impedance into the transmission lines to change the power flow characteristics. The addition of integrated fault current handling circuitry makes the SSSC and similar FACTS devices unwieldy, heavy, and not a viable solution for distributed control. What is disclosed are modifications to FACTS devices that move the fault current protection external to the FACTS device and make them modular and re-usable.
1. A method of providing distributed control and fault current protection for a power transmission and distribution system comprising a plurality of high-voltage (HV) transmission lines, the method comprising:
providing a plurality of impedance injection modules distributed over and coupled to each HV transmission line, each impedance injection module comprising one or more interconnected flexible alternating current transmission systems (FACTS) devices without fault current protection built-in, each impedance injection module configured to inject impedance into the HV transmission line;
providing a plurality of external fault current protection modules, each of the external fault current protection modules connected in parallel with one or more impedance injection modules; and
providing a plurality of communication modules, each communication module enables an impedance injection module to communicate with one or more external fault current protection modules to handle at least a duration fault, a surge or a transient.
2. The method of claim 1 , wherein the one or more interconnected FACTS devices of the impedance injection module inject the impedance into the HV transmission line, the injected impedance being an inductive or a capacitive impedance.
3. The method of claim 2 , wherein the one or more interconnected FACTS devices comprise a plurality of static synchronous series compensators (SSSCs).
4. The method of claim 2 , wherein the one or more interconnected FACTS devices comprise a plurality of thyristor controlled series compensator (TCSCs).
5. The method of claim 3 , wherein one or more of the SSSCs are implemented as part of the impedance injection module for generation and injection of the inductive or capacitive impedance into a segment of the HV transmission line.
6. The method of claim 4 , wherein one or more of the TCSCs are implemented as part of the impedance injection module for generation and injection of the inductive or capacitive impedance into a segment of the HV transmission line.
7. The method of claim 1 wherein the one or more interconnected FACTS devices are coupled to the HV transmission line using a transformer.
8. The method of claim 1 wherein the one or more interconnected FACTS devices of the impedance injection module are connected to the HV transmission line directly without fault current protection.
9. The method of claim 1 wherein the external fault current protection modules are distributed over the HV transmission line and supported by the HV transmission line.
10. The method of claim 1 , wherein each external fault current protection module is supported by a separate support structure.
11. The method of claim 1 , wherein the one or more impedance injection modules and the parallel connected external fault current protection module are located at a substation.
12. A system for providing fault current protection for a power transmission and distribution system having a plurality of high-voltage (HV) transmission lines, the system for providing fault current protection comprising:
the plurality of interconnected flexible alternating current transmission systems (FACTS) devices configured as a plurality of impedance injection modules distributed over the HV transmission lines, the impedance injection modules being without fault current protection, each impedance injection module being coupled to an HV transmission line;
a plurality of external fault current protection modules; and
a plurality of communication modules;
each communication module enables an impedance injection module to communicate with an external fault current protection module;
each external fault current protection module being connected in parallel across one or more impedance injection modules to provide a coordinated fault current protection to one or more interconnected FACTS devices.
13. The system of claim 12 , wherein each impedance injection module is coupled to an HV transmission line by a first bus having a first circuit breaker at one end and a second bus having a second circuit breaker at another end;
wherein the first and second circuit breakers are enabled to isolate a segment of the HV transmission line between the first circuit breaker and the second circuit breaker.
14. The system of claim 12 , wherein the plurality of interconnected FACTS devices comprise one or more static synchronous series compensators (SSSCs).
15. The system of claim 12 , wherein the plurality of interconnected FACTS devices comprise one or more thyristor controlled series compensator (TCSCs).
16. The system of claim 12 , wherein the one or more impedance injection modules and the parallel connected external fault current protection module are distributed over an HV transmission line and are supported by the HV transmission line.
17. The system of claim 12 , wherein the one or more impedance injection modules and the parallel connected external fault current protection module are distributed over an HV transmission line, with the HV transmission line supporting the one or more impedance injection modules and a separate support structure supporting the external fault current protection module.
18. The system of claim 12 , wherein each impedance injection module is connected to an HV transmission line using a transformer having a winding in series with the HV transmission line.
19. The system of claim 12 , wherein the impedance injection modules are connected directly in series with the HV transmission lines without fault current protection.
20. The system of claim 12 , wherein the external fault current protection modules enable standardization of the impedance injection modules in performance and power flow control without fault current protection.
21. The system of claim 12 , wherein the external fault current protection module connected in parallel with the one or more impedance injection modules enable use of a standardized external fault current protection module on the HV transmission lines.
22. The system of claim 12 , wherein each external fault current protection module comprises a plurality of fault current protection devices.
23. The system of claim 12 , wherein each external fault current protection module comprises:
a recloser switch for reset,
a plurality of fault current protection devices selected from a group comprising a metal oxide varistor (MOV) to handle some duration faults, surges and transients,
a triggered gap in series with a current limiting inductor to handle other duration faults, and
a bypass switch for short circuit conditions and ground shorts.
24. The system of claim 12 , wherein each external fault current protection module comprises:
a recloser switch for reset,
a metal oxide varistor (MOV) for some duration faults, surges and transients,
a triggered gap in series with a current limiting inductor for other duration faults, and
a bypass switch for short circuits and ground faults.
25. The system of claim 22 , wherein the fault current protection devices comprise:
a metal oxide varistor (MOV) for some duration faults, surges and transients,
a triggered gap in series with a current limiting inductor for other duration faults, and
a bypass switch for short circuits and ground faults.