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 controls for a power transmission and distribution system comprising:
providing flexible alternating current transmission systems (FACTS) devices, each without fault current protection;
providing fault current protection modules as modules not containing a FACTS device;
providing a plurality of FACTS devices on a power transmission line; and
coupling a fault current module to the transmission line so that the fault current module is coupled in parallel with all FACTS devices in the plurality of FACTS devices;
wherein the FACTS devices are connected in parallel, or some of the FACTS devices are connected in series and some of the FACTS devices are connected in parallel.
2. The method of claim 1 wherein the FACTS devices comprise at least one static synchronous series compensator.
3. The method of claim 1 wherein the FACTS devices comprise at least one thyristor controlled series compensator.
4. The method of claim 1 wherein the FACTS devices and the fault current protection module are hung on the transmission line.
5. The method of claim 1 wherein the fault current protection module is separately supported.
6. The method of claim 1 wherein the FACTS devices and the fault current protection module are located in a substation.
7. The method of claim 1 wherein the fault current protection module includes a bypass breaker for short circuits and ground fault conditions.
8. The method of claim 7 wherein the fault current protection module further includes a metal oxide varistor for short duration faults, surges, and transient events.
9. The method of claim 1 wherein the fault current protection module further includes a recloser switch for reset when the faults are removed.
10. The method of claim 9 wherein the recloser switch also functionally isolates a respective group of FACTS devices by removing transmission line current from the respective group of FACTS devices.
11. The method of claim 1 wherein the transmission line includes a first breaker between a first bus and the FACTS devices, and a second breaker between the FACTS devices and a second bus on the transmission line to isolate the transmission line section between the first and second breakers from the rest of the transmission system.
12. A method of providing distributed controls for a power transmission and distribution system comprising:
providing flexible alternating current transmission systems (FACTS) devices, each without fault current protection;
providing fault current protection modules as modules not containing a FACTS device;
providing a plurality of FACTS devices on a power transmission line; and
coupling a fault current module to the transmission line so that the fault current module is coupled in parallel with all FACTS devices in the plurality of FACTS devices;
wherein the transmission line includes a first breaker between a first bus and the FACTS devices, and a second breaker between the FACTS devices and a second bus on the transmission line to isolate the transmission line section between the first and second breakers from the rest of the transmission system;
wherein the transmission line further includes additional breakers connected to ground to discharge the FACTS devices and adjoining section of the transmission line when the transmission line section is disconnected from the transmission system by the first and second breakers.
13. A system for providing distributed controls for a power transmission and distribution system comprising;
a plurality of flexible alternating current transmission systems (FACTS) devices, each without fault current protection, that are enabled as FACTS modules for distribution over the power transmission and distribution system;
at least a fault current protection module that is not part of a FACTS module;
wherein the FACTS modules are coupled to a transmission line of the power transmission and distribution system as at least a group of FACTS modules; and
the at least a fault current protection module is connected in parallel across each of the at least a group of FACTS modules to provide fault current protection;
wherein the at least a group of FACTS modules are enabled as a parallel connected group of FACTS modules coupled to the transmission line, or the at least a group of FACTS modules are enabled as a plurality of serial strings of FACTS modules connected in parallel coupled to the transmission line.
14. The system of claim 13 , wherein each of the at least a group of FACTS modules having the at least a fault current protection module connected in parallel are coupled to the power transmission line by a first bus having a first circuit breaker at one end and a second bus having a second circuit breaker at the other end;
wherein the circuit breakers are enabled to isolate a segment of the transmission line between the first circuit breaker and the second circuit breaker from the transmission system.