Generator loss-of-field protection

Patent metadata

Field	Value
Publication number	US-11196369-B2
Application number	US-201916425763-A
Country	US
Kind code	B2
Filing date	May 29, 2019
Priority date	Aug 31, 2018
Publication date	Dec 7, 2021
Grant date	Dec 7, 2021

Abstract

Protection devices prevent damage to synchronous generators during loss-of-field events. In various embodiments, a first protective element is associated with a first protection zone to protect a generator from a loss-of-field event at full load. A second protective element is associated with a second protection zone to prevent thermal overload during underexcited operation of the generator and to protect from loss-of-filed at light load. A third protective element associated with a third protection zone limits operation of the generator within the generator's specific steady-state stability limits. A fourth protective element is associated with a fourth protection zone to provide an alarm prior to operation of the second protective element. In various embodiments, characteristics and limits of each of the protective elements are defined in the same plane (specifically, the P-Q plane) to simplify settings and allow for visualization of the element characteristics and the generator capability curve at one or more temperatures or cooling capacities.

First claim

What is claimed is:

1. A system to provide loss-of-field protection for a synchronous generator, comprising:
an intelligent electronic device (IED) with a processor and instructions stored on a computer-readable medium that, when executed by the processor, cause the system to:
adjust loss-of-field protection settings associated with a first zone of protection in a P-Q plane to prevent damage to the generator from a loss-of-field event at full load by implementing a first protective action within a number of cycles between approximately 3 and 15 cycles;
adjust loss-of-field protection settings associated with a second zone of protection in the P-Q plane to prevent damage to the generator for a loss-of-field event at a light load;
adjust steady-state stability limit protection settings associated with a third zone of protection in the P-Q plane to limit operation of the generator to within a steady-state stability limit of the generator; and
adjust alarm settings associated with a fourth zone of protection in the P-Q plane to provide an alarm prior to a protective action relating to a loss-of-field event at the light load.

2. The system of claim 1 , wherein the instructions, when executed by the processor, are further configured to adjust protection settings in the P-Q plane to trigger thermal overload during underexcited operation of the generator.

3. The system of claim 1 , wherein the instructions, when executed by the processor, are further configured to limit operation of the generator within a stator end-core heating limit.

4. The system of claim 1 , wherein the instructions, when executed by the processor, are configured to:
adjust the steady-state stability limit protection settings to implement a second protective action within a number of seconds between approximately 1 and 60 seconds.

5. The system of claim 4 , wherein the instructions, when executed by the processor, are further configured to adjust undervoltage protection settings to detect undervoltage, and
wherein the steady-state stability limit protection settings are configured to implement the second protective action within an accelerated number of cycles between approximately 15 and 30 cycles when an undervoltage is identified.

6. The system of claim 5 , wherein an undervoltage is identified when a terminal voltage of the generator is measured to be less than a percentage of nominal voltage between approximately 80% and 87%.

7. The system of claim 1 , wherein the steady-state stability limit is calculated as a function of the system impedance, X S , and the generator impedance, X d .

8. The system of claim 1 , further comprising a thermal adjustment subsystem to modify operational limits based on a thermal characteristic.

9. The system of claim 8 , wherein the thermal adjustment subsystem is configured to modify the operational limits based on at least one of:
(i) an analog measurement of a real time temperature, and
(ii) a digital input indicating an available cooling capacity of the generator.

10. The system of claim 1 , wherein the instructions, when executed by the processor, are configured to adjust the loss-of-field protection settings proportionally with respect to a terminal voltage (V T ) of the generator raised to the power of k, (V T k ), where k is an integer.

11. The system of claim 1 , further comprising a tripping device to disconnect the generator from a load when operation of the generator exceeds the steady-state stability limit.

12. The system of claim 11 , wherein the tripping device is configured to disconnect the generator when at least one of two conditions is satisfied, including:
(i) an automatic voltage regulator indicates operation in manual mode, and
(ii) a terminal voltage, V T , of the generator drops below 80% of a nominal operational voltage.

13. The system of claim 11 , wherein the tripping device is configured to disconnect the generator when both of two conditions are satisfied, including:
(i) an automatic voltage regulator indicates operation in manual mode, and
(ii) a terminal voltage, V T , of the generator drops below 80% of a nominal operational voltage.

14. The system of claim 1 , wherein each of the first, second, third, and fourth zones of protection and a generator capability curve of the generator are displayed as part of a graphical user interface in the P-Q plane to simplify system configuration.

15. The system of claim 1 , further comprising a controller and memory to coordinate and supervise the first, second, third, and fourth protective elements.

16. A protective device to provide loss-of-field protection for a synchronous generator, comprising:
a processor;
a non-transitory computer-readable medium with instructions stored thereon that, when executed by the processor, cause the protective device to:
adjust loss-of-field protection settings associated with a first zone of protection in a P-Q plane to disconnect the generator in response to a loss-of-field event at full load within a number of cycles between approximately 3 and 15 cycles;
adjust steady-state stability limit protection settings associated with a second zone of protection in the P-Q plane to limit operation of the generator to within a steady-state stability limit of the generator; and
adjust underexcitation protection settings associated with a third zone of protection in the P-Q plane to limit operation of the generator within a stator end-core heating limit during underexcited operation of the generator.

17. The protective device of claim 16 , wherein the instructions, when executed by the processor, are further configured to:
adjust loss-of-field protection settings associated with a fourth zone of protection in the P-Q plane to prevent damage to the generator for a loss-of-field event at a light load.

18. The protective device of claim 17 , wherein the instructions, when executed by the processor, are further configured to:
adjust alarm settings associated with a fourth zone of protection in the P-Q plane to provide an alarm prior to a protective action relating to the loss-of-field event at the light load.

19. The protective device of claim 16 , further comprising a tripping device to disconnect the generator from a load in response to operation of the generator exceeding the steady-state stability limit.

Assignees

• Schweitzer Engineering Lab Inc

Inventors

• Alla Matchyaraju
• Guzman-Casillas Armando
• Finney Dale S
• Fischer Normann

Classifications

• H02P29/02

  Providing protection against overload without automatic interruption of supply (protection against faults of stepper motors H02P8/36) · CPC title

• H02P9/12

  for demagnetising; for reducing effects of remanence; for preventing pole reversal · CPC title

• H02H7/065

  against excitation faults · CPC title

• G01R31/343

  in operation · CPC title

• H02P29/40

  Regulating or controlling the amount of current drawn or delivered by the motor for controlling the mechanical load · CPC title