Breaker failure protection using reverse active power and negative reactive power element

Patent metadata

Field	Value
Publication number	US-11368113-B2
Application number	US-201916717438-A
Country	US
Kind code	B2
Filing date	Dec 17, 2019
Priority date	Dec 17, 2019
Publication date	Jun 21, 2022
Grant date	Jun 21, 2022

Abstract

A generator system includes a generator including terminals, a generator circuit breaker coupled to the terminals and that couples and decouples the generator from a power grid, multiple sensors, and a controller that operates the generator system. The controller determines whether an active power is less than a reverse active power threshold and whether one or more turbine valves are closed, and determines that a breaker failure has occurred based on the active power being less than the reverse active power threshold and the one or more turbine valves being closed. If the active power remains less than the reverse active power and the turbine valves remain closed after a threshold time period after the trip command, and if a reactive power is less than a reverse reactive power threshold, then a breaker failure has occurred. In response, the controller may transmit another trip command to the generator circuit breaker to initiate the breaker failure protection.

First claim

What is claimed is:

1. A generator system, comprising:
a generator comprising terminals;
a generator circuit breaker coupled to the terminals and configured to selectively couple and decouple the generator from a power grid;
a plurality of sensors; and
a controller configured to receive a plurality of signals from the sensors, wherein the plurality of signals indicate a reverse active power in watts, an active power in watts, or a combination thereof, wherein the controller is configured to operate the generator system, including by:
determining whether the active power is less than a reverse active power threshold;
determining whether one or more turbine valves of the generator are closed;
determining that a breaker failure has occurred based at least in part on the active power being less than the reverse active power threshold wattage and the one or more turbine valves being closed; and
transmitting a trip command to the generator circuit breaker and a field circuit breaker in response to determining that the breaker failure has occurred, wherein the field circuit breaker is disposed between the generator circuit breaker and before a load that is powered by the generator.

2. The generator system of claim 1 , wherein the active power and a reactive power are measured based on a sensor current generated by a current transformer, wherein the sensor current is proportional to current flowing through the current transformer.

3. The generator system of claim 1 , wherein the breaker failure indicates that the generator circuit breaker is closed after an initial trip command has failed to open the generator circuit breaker.

4. The generator system of claim 3 , wherein the trip command to the generator circuit breaker and the field circuit breaker are transmitted simultaneously.

5. The generator system of claim 1 , wherein the controller is configured to:
determine whether the breaker failure continues for a threshold time; and
transmit the trip command to the generator circuit breaker and field circuit breaker in response to the breaker failure continuing for the threshold time.

6. The generator system of claim 5 , wherein the threshold time is based on a timer set to 1 second.

7. The generator system of claim 1 , wherein the plurality of sensors are configured to measure power of the generator at a terminal side of the generator.

8. The generator system of claim 1 , wherein the controller is configured to:
determine whether the active power is less than 0 W;
in response to the one or more turbine valves being closed and the active power being less than 0 W, determine whether a reactive power (Q G ) is less than a reverse reactive power threshold,

Q
G

<

[

C
*

V
t
2

X
d

]

,

where C is a coefficient, V t 2 is a terminal voltage for the generator, and X d is a direct axis synchronous reactance; and
transmit the trip command to the generator circuit breaker in response to the active power being less than the reverse active power threshold, the one or more turbine valves being closed, the active power being less than 0 W, and the reactive power being less than the reverse reactive power threshold.

9. The generator system of claim 8 , wherein the trip command comprises a backup trip command used after a previous trip command has failed to trip the generator circuit breaker, wherein the previous trip command failing to trip the generator circuit breaker results in the breaker failure.

10. The generator system of claim 1 , wherein the controller is configured to:
determine whether an active power is less than 0 W;
in response to the one or more turbine valves being closed and the active power being less than 0 W, determine whether a reactive power (Q G ) is less than a reverse reactive power threshold,

Q
G

<

[

C
*

V
t
2

X
d

]

,

where C is a coefficient, V t 2 is a terminal voltage for the generator, and X d is a direct axis synchronous reactance; and
transmit the trip command to the generator circuit breaker in response to the active power being less than the reverse active power threshold wattage, the active power being less than 0 W, the one or more turbine valves being closed, and the reactive power being less than the reverse reactive power threshold.

11. The generator system of claim 10 , wherein the trip command is transmitted from the controller in response to a low current used to detect the breaker failure, wherein the low current comprises a current less than 10% of a rated current of a current transformer.

12. The generator system of claim 11 , wherein the low current continues to power the generator prior to the controller transmitting the trip command.

13. A method for operating a generator in a generator system, the method comprising:
determining whether an active power in watts associated with the generator is less than a reverse active power threshold wattage associated with the generator;
determining whether one or more turbine valves of the generator are closed;
determining that a breaker failure has occurred based at least in part on the active power being less than the reverse active power threshold wattage and the one or more turbine valves being closed;
determining whether the breaker failure continues for a threshold time; and
transmitting a trip command to a generator circuit breaker and a field circuit breaker simultaneously in response to determining that the breaker failure has continued for the threshold time.

14. The method of claim 13 , the method comprising:
determining whether the active power is less than 0 W;
in response to the one or more turbine valves being closed and the active power being less than 0 W, determining whether a reactive power (Q G ) is less than a reverse reactive power threshold,

Q
G

<

[

C
*

V
t
2

X
d

Assignees

• Schweitzer Engineering Lab Inc

Inventors

• Alla Matchyaraju

Classifications

• H02H7/06 Primary

  for dynamo-electric generators; for synchronous capacitors · CPC title

• H02P9/006 Primary

  Means for protecting the generator by using control (control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10) · CPC title

• H02H3/04

  with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned {(watching of pilot wires H02H1/0084; protection of protective arrangements H02H7/008; indication of the state of electronic switches H03K17/18)} · CPC title

• H02P9/02

  Details {of the control} · CPC title