Protection techniques for an electric power system

• US 9,000,611 B2
• Filed: 04/20/2009
• Issued: 04/07/2015
• Est. Priority Date: 05/07/2007
• Status: Active Grant

• Current Assignee: Cummins Power Generation IP, Inc.
• Original Assignee: Cummins Power Generation IP, Inc.
• Inventors: Lorenz, Rick A., Schelkopf, J. Bruce
• Primary Examiner(s): Fleming, Fritz M
• Application Number:
  US12/386,566
• Publication Number:
  US 20100010684A1
• Time in Patent Office: 2,178 Days
• Field of Search: 307 64- 66, 307/125, 307/131, 307/326, 307/153, 361/20, 361/21
• US Class Current: 307/64
• CPC Class Codes: H02H 7/06 for dynamo-electric generators; for synchronous capacitors
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems

Abstract

One embodiment of the present application is directed to a protection technique for an electric power generation system. In one or more implementations, an electric power generator, generator control circuitry, electrical output sensors to provide one or more corresponding signals, electrical switching equipment to selectively couple the generator to an electrical load, and electric power feeder or branch circuit conductors, to route electric power from the generator to the switching equipment, are provided. The control circuitry is responsive to the sensor signals to determine if a shutdown condition exists as a function of a protection profile determined for the system. This profile may account for damage thresholds of the generator, the feeder or branch circuit conductors, the electrical switching equipment for each of a number of different combinations of level and duration of electrical output as represented by the sensor signals.

Claims

1. A method, comprising:

operating an electrical power system including a generator and a transfer switch with a first input coupled to the generator by conductors, and a second input coupled to a power source, wherein the conductors comprise one of feeder conductors and branch circuit conductors;

providing electrical power to an electrical load from the generator through the transfer switch;

monitoring an electrical output of the generator during the providing of the electrical power to the electrical load; and

determining a shutdown condition in relation to a protection profile comprising a plurality of electrical output values each corresponding to one of a plurality of duration values, the protection profile representing a damage threshold for a plurality of power components.

2. The method of claim 1, wherein the protection profile further comprises a function relating a range of the electrical output values to a corresponding range of the duration values.

3. The method of claim 2, further comprising halting operation of the generator in response to the shutdown condition.

4. The method of claim 3, which includes maintaining electrical continuity of the conductors, to the generator and to the transfer switch during the halting of the generator.

5. The method of claim 2, wherein the electrical output values comprise electrical current values provided by the generator, wherein the protection profile is representative of an overcurrent protection curve, and wherein the power source is a utility power source.

6. The method of claim 1, wherein the plurality of power components comprises at least two electrical components selected from the electrical components consisting of the generator, the conductors, the transfer switch, utilization equipment, and the electrical load.

7. The method of claim 6, further comprising providing the electrical power with a neutral conductor, wherein monitoring of the electrical output further includes sensing a neutral electrical current through the neutral conductor and a ground electrical current through to an electrical ground of the generator, and the method further comprising providing for a halting operation of the generator in response to the shutdown condition.

8. The method of claim 7, further comprising stopping operation of the generator if at least one of the neutral electrical current and the ground electrical current exceeds a predetermined threshold.

9. The method of claim 6, further including configuring the transfer switch to route electricity from the power source to the electrical load in response to the shutdown condition.

10. The method of claim 9, further comprising halting operation of the generator in response to the shutdown condition.

11. The method of claim 2, further comprising providing a protective device between the generator and the transfer switch and changing a state of the protective device to provide an electrical discontinuity between the generator and the transfer switch in response to the shutdown condition.

12. The method of claim 2, wherein the generator is one of a plurality of generators structured to operate in parallel to provide electricity to the transfer switch, wherein each of the multiple generators is selectively coupled to a common power bus by a circuit switch device.

13. The method of claim 12, wherein the power source provides power independent of the plurality of generators.

14. A method, comprising:

operating an electrical power system including a power generation subsystem comprising a generator and generator control circuitry, and a transfer switch with a first input coupled to the generator by conductors, and a second input electrically coupled to a power source, wherein the conductors comprise one of feeder conductors and branch circuit conductors;

supplying electrical power from the generator to the transfer switch;

monitoring an electrical output of the generator during the supplying of the electrical power;

determining a shutdown condition with the generator control circuitry; and

ceasing operation of the generator in response to the shutdown condition while maintaining electrical continuity between the generator and the transfer switch.

15. The method of claim 14, wherein electrical output includes electrical current, and wherein determining the shutdown condition includes comparing the electrical current to a predetermined protection profile for the electrical power system, the predetermined protection profile comprising a plurality of electrical output values each corresponding to one of a plurality of duration values, the predetermined protection profile representing a damage threshold for a power component comprising at least one component selected from the components consisting of the generator, the conductors, and the transfer switch.

16. The method of claim 15, wherein the plurality of electrical output values comprise a plurality of overcurrent levels and the plurality of duration values comprises a plurality of overcurrent durations.

17. The method of claim 14, wherein the determining of the shutdown condition includes detecting at least one condition selected from the conditions consisting of:

a ground fault, an overvoltage condition, and an undervoltage condition.

18. The method of claim 14, further comprising providing the electrical power with a neutral conductor, wherein monitoring of the electrical output further includes sensing a neutral electrical current through the neutral conductor and a ground electrical current through to an electrical ground of the generator.

19. The method of claim 18, further comprising stopping operation of the generator if at least one of the neutral electrical current and the ground electrical current exceeds a predetermined threshold.

20. The method of claim 14, further including configuring the transfer switch to route electricity from the power source to the electrical load in response to the shutdown condition.

21. An apparatus, comprising:

an electric power generation system including;

a generator;

generator control circuitry;

at least one electric output sensor each structured to provide a sensor signal to the generator control circuitry representative of an electric output of the generator;

electrical switching equipment structured to selectively couple the generator to an electrical load;

electric power conductors electrically coupling the generator to the electrical switching equipment, wherein the conductors comprise one of feeder conductors and branch circuit conductors; and

the generator control circuitry structured to;

interpret an overcurrent protection profile, the overcurrent protection profile comprising a range of overcurrent level values corresponding to a range of overcurrent duration values for each of a plurality of power components, the power components comprising the generator, the conductors, and the electrical switching equipment; and

determine if a shutdown condition exists in response to at least one provided sensor signal and the overcurrent protection profile.

22. The apparatus of claim 21, wherein the generator control circuitry is further structured to generate an output signal in response to the shutdown condition, and wherein the generator is structured to halt operation in response to the output signal.

23. The apparatus of claim 22, further comprising an internal combustion engine mechanically coupled to the generator to provide rotary power thereto.

24. The apparatus of claim 23, wherein the generator control circuitry includes means for regulating generator operation that is responsive to rotational speed of the engine.

25. The apparatus of claim 21, wherein the generator is one of multiple generators coupled in parallel and each connected to a common power bus by a circuit switch and the electrical switching equipment is a transfer switch structured to select between the generator and another power source.

26. The apparatus of claim 21, wherein the electrical switching equipment includes a circuit switch.

27. The apparatus of claim 21, further comprising means for protecting the electric power generation system in response to one or more of a ground fault, an overvoltage condition, and an undervoltage condition.

28. The apparatus of claim 21, wherein the generator is coupled to a neutral conductor and further includes a first current sensor to detect electrical current flow through the neutral conductor and a second current sensor to detect electrical ground current.

29. The apparatus of claim 21, wherein the electrical switching equipment includes a transfer switch structured to route electricity from a utility power source to the electrical load in response to the shutdown condition.

30. A control system operative with an electrical power system including a generator, generator control circuitry, at least one electric output sensor each structured to provide a sensor signal to the generator control circuitry representative of an electric output of the generator, electrical switching equipment structured to selectively couple the generator to an electrical load, and electric power conductors comprising one of feeder conductors and branch circuit conductors, electrically coupling the generator to the electrical switching equipment, the electrical power system comprising a centralized processing unit (CPU), an instantiable computer program product for protecting the electric power system, and a computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions including a first executable portion having instructions being capable of:

instructing operation of the electrical power system, controlling supply of electrical power to an electrical load from the generator through the electrical switching equipment, monitoring electrical output of the generator during supply of the electrical power to the electrical load, and determining a shutdown condition in relation to a predetermined protection profile for each one of the generator, the electrical switching equipment, and the electrical power conductors.

31. The system of claim 30, wherein the instructions are further capable of:

instructing control circuitry in response to a sensitivity value and at least one provided sensor signal to determine if a shutdown condition exists as a function of the predetermined protection profile.

32. The system of claim 31, wherein the instructions are further capable of:

instructing a halting of generator operation in response to the shutdown condition.

33. The system of claim 32, wherein the generator operation is halted if at least one of a neutral electrical current, a ground electrical current, and a predicted profile value exceeds a predetermined threshold in relation to the sensitivity value.

34. The system of claim 33, wherein the instructions are further capable of:

instructing the electrical switching equipment to route electricity from a utility power source to the electrical load in response to the shutdown condition.

35. The system of claim 34, wherein the electrical switching equipment is a transfer switch.

36. The system of claim 35, wherein the at least one protection profile is available from at least one of the sources consisting of a look up table, a data storage device, a remote database, a network source, and an interne source.

37. The system of claim 36, wherein the electrical switching equipment is a transfer switch.

38. The system of claim 37, wherein a protective device is provided between the generator and the transfer switch and further comprising changing state of the protective device to provide an electrical discontinuity between the generator and the transfer switch in response to the shutdown condition.

39. The system of claim 38, wherein the computer-readable program code portions are executed remotely from at least one of the electrical power system and via a wireless network.

40. The system of claim 38, wherein the instructions are further capable of:

reporting a shutdown condition to a predetermined device in networked communication.

41. The system of claim 31, wherein the protection profile is determined as representing a damage threshold for the generator, the conductors, and the electrical switching equipment at each of a number of different combinations of an electrical output value and a corresponding duration value for the electrical power system and to be at least one protection profile selected from the protection profiles consisting of:

an overcurrent protection profile, a modified overcurrent protection profile, a customized protection profile and one or more accessible protection profiles available for access;

wherein the overcurrent protection profile is representative of an overcurrent damage threshold of the generator, the conductors, and the electrical switching equipment for each of a number of different combinations of overcurrent level and overcurrent duration;

the modified overcurrent protection profile is representative of an approximated overcurrent damage threshold of the generator, the conductors, and the electrical switching equipment for each of a number of different combinations of overcurrent level and overcurrent duration;

the customized overcurrent protection profile is representative of a calculated overcurrent damage threshold of the generator, the conductors, and the electrical switching equipment for each of a number of different combinations of overcurrent level and overcurrent duration; and

the one or more accessible protection profiles is representative of a predetermined damage threshold of the generator for current, the feeder conductors, and the electrical switching equipment for each of a number of different combinations of a level of current in relation to a predetermined duration of time.