System for improving lightning immunity for a solid state power controller
A solid state power controller (SSPC) for an electrical power distribution system (EPDS), the SSPC may include a solid state switching device (SSSD) configured to interrupt current in a feeder line of the EPDS and a processing engine. A clamping device may be interposed between the feeder line and an electrical ground of the EPDS, An opto-coupler may be interposed between the processing engine and the clamping device. The opto-coupler may coupled to the clamping device to provide a lightning-detected signal to the processing engine only when a voltage drop develops across the clamping device. The processing engine may be constrained from commanding an alteration of state of the SSSD upon receiving the lightning-detected signal.
1. A solid state power controller (SSPC) for an electrical power distribution system (EPDS), the SSPC comprising:
a solid state switching device (SSSD) configured to interrupt current in a feeder line of the EPDS;
a processing engine;
a clamping device interposed between the feeder line and an electrical ground of the EPDS; and
an opto-coupler interposed between the processing engine and the clamping device,
wherein the opto-coupler is coupled to the clamping device to provide a lightning-detected signal to the processing engine only when a voltage drop develops across the clamping device,
wherein the processing engine is constrained from commanding an alteration of state of the SSSD upon receiving the lightning-detected signal.
2. The SSPC of claim 1 further comprising
a short circuit detection unit coupled to the processing engine, the short circuit detection unit configured to provide a short circuit trip signal to the processing engine in the event of a current surge through the feeder line in excess of a predetermined magnitude and duration; and
wherein the processing engine is configured to provide a command to the SSSD to alter the state of the SSSD to an OFF state upon receiving the short circuit trip signal and upon also not receiving the lightning-detected signal within a predetermined duration after receiving the short circuit signal.
3. The SSPC of claim 2 wherein the predetermined duration is less than about 100 nanoseconds (ns).
4. The SSPC of claim 3 further comprising:
an arc fault detection algorithm within the processing engine and configured to provide an arc fault signal to the processing engine in the event of a variation in current through the feeder line, the variation being consistent with arc fault characteristics,
wherein the processing engine is configured to provide a command to the SSSD to alter the state of the SSSD to an OFF state upon receiving the arc fault signal and upon also not receiving the lightning-detected signal within the predetermined duration after receiving the arc fault signal.
5. The SSPC of claim 1 :
wherein the clamping device is coupled with a second clamping device;
wherein the second clamping device is interposed between the clamping device and the electrical ground; and
wherein the clamping device and the second clamping device in combination have a total breakdown voltage that is greater than a maximum normal operational line voltage including normal transients of the EPDS.
6. The SSPC of claim 5 wherein the clamping device is a low voltage clamping device with a breakdown voltage rating of about 9 volts to about 12 volts.
7. The SSPC of claim 1 wherein the opto-coupler is coupled to the clamping device so that light-emitting diodes (LED) of the opto-coupler are connected in parallel with the low voltage clamping device.
8. The SSPC of claim 7 wherein the low voltage clamping device and the second clamping device are transient voltage suppressors (TVS).
9. The SSPC of claim 7 wherein the opto-coupler has a rise time rating between about 10 nanoseconds (ns) to about 100 ns.
10. A lightning detection system for a solid state power controller (SSPC) of an electrical power distribution system (EPDS) comprising:
a lightning-protection clamping device interposed between a feeder line of the EPDS and an electrical ground of the EPDS;
a sensor clamping device connected in series with the lightning-protection clamping device and interposed between the feeder line and the lightning-protection clamping device; and
an opto-coupler connected in parallel with the sensor clamping device between an input side and an output side of the sensor clamping device,
wherein the lightning-protection clamping device has a first breakdown voltage rating,
wherein the sensor clamping device has a second breakdown voltage rating lower than the first breakdown voltage rating.
11. The lightning detection system of claim 10 wherein the opto-coupler has a rise time rating between about 10 nanoseconds (ns) to about 100 ns.
12. The lightning detection system of claim 10 wherein the sensor clamping device has a breakdown voltage rating of about 9 Volts to about 12 volts.
13. The lightning detection system of claim 10 wherein the lightning-protection clamping device and the sensor clamping device in combination have a total breakdown voltage rating that is greater than a maximum normal operational line voltage including normal transients of the EPDS.
14. The lightning detection system of claim 10 further comprising a resistor connected in parallel with the sensor clamping device between the input side and the output side of the sensor clamping device, the resistor being interposed between the sensor clamping device and the opto-coupler.
15. The lightning detection system of claim 14 wherein the resistance value of the resistor is small enough so that current passing through the opto-coupler is insufficient to produce an output from the opto-coupler when the current passing through the resistor is produced by noise and not by a lightning-induced surge.
16. The lightning detection system of claim 10 wherein the sensor clamping device and the lightning-protection clamping device are transient voltage suppressors (TVS).
17. A method for avoiding a lightning-induced nuisance trip in a solid state power controller (SSPC) of an electrical power distribution system (EPDS) comprising the steps of:
producing light with a portion of a current surge arising from a lightning strike;
detecting presence of the produced light to produce a lightning-detected signal; and
utilizing the lightning-detected signal to constrain the SSPC from tripping when a short circuit signal or arc fault signal develops in the SSPC within a predetermined time period before the production of the lightning-detected signal.
18. The method of claim 17 :
wherein the lightning-detected signal is generated within a time period no greater than about 100 nanoseconds (ns) after the lightning strike; and
wherein the predetermined time period is no greater than 100 ns.
19. The method of claim 17 further comprising the step of limiting the line voltage of the EPDS during lightning strikes to a voltage that is no greater than the maximum voltage rating of any circuit component or load connected to the EPDS.
20. The method of claim 19 wherein the step of producing light occurs at a voltage that is between about 9 V and about 12 V.