Protection method for protecting a generator or power station unit and protective device for carrying out such a method

Patent metadata

Field	Value
Publication number	US-10439386-B2
Application number	US-201715678526-A
Country	US
Kind code	B2
Filing date	Aug 16, 2017
Priority date	Aug 16, 2016
Publication date	Oct 8, 2019
Grant date	Oct 8, 2019

Abstract

A method protects an electrical generator or power station unit connected to a power distribution network or to a power transmission line. A short circuit near the generator in the power distribution network or on the power transmission line is detected, and a short-circuit detection signal is generated, when a set of predetermined trigger conditions is satisfied. The electrical generator is disconnected from the network or line if, after generation of the short-circuit detection signal, the trigger conditions are satisfied at the instant when a predetermined delay time elapses, and have remained satisfied until the predetermined delay time elapses. The delay time is a variable duration which is reestablished regularly or irregularly before it elapses, as a function of the operating profile after the short-circuit occurrence, and the generator is disconnected if the trigger conditions are satisfied at the instant when the delay time elapses.

First claim

The invention claimed is:

1. A protection method for protecting an electrical generator or power station unit connected to a power distribution network or to a power transmission line, which comprises the steps of:
detecting a short circuit near the electrical generator or power station unit in the power distribution network or on the power transmission line;
generating a short-circuit detection signal when a set of predetermined trigger conditions is satisfied;
disconnecting the electrical generator or power station unit from the power distribution network or the power transmission line if, after generation of the short-circuit detection signal, the set of predetermined trigger conditions are satisfied at an instant when a predetermined delay time elapses, the predetermined delay time being a variable duration which is reestablished before it elapses, in dependence on an operating profile after a short-circuit occurrence.

2. The method according to claim 1 , which further comprises:
starting a timer when the short-circuit detection signal occurs, either immediately after an occurrence of the short-circuit detection signal or at a predetermined instant thereafter; and
disconnecting the electrical generator from the power distribution network or the power transmission line if a time indication output by the timer corresponds to or exceeds the respectively currently established delay time and the set of predetermined trigger conditions are satisfied at this instant.

3. The method according to claim 1 , which further comprises establishing the predetermined delay time in dependence on a respective power difference between power before detection of the short circuit and the power at a respective current instant.

4. The method according to claim 1 , which further comprises establishing the predetermined delay time by applying or reading out a predetermined formula, a predetermined characteristic or a predetermined table which establishes a relationship between a difference value indicating a respective power difference or active power difference and the predetermined delay time corresponding thereto.

5. The method according to claim 1 , which further comprises:
starting the timer upon an occurrence of the short-circuit detection signal, and a stopping and/or a resetting of the timer is suppressed when, at a predetermined subsequent instant after generation of the short-circuit detection signal:
the short-circuit detection signal is still present at the predetermined subsequent instant;
an active power has in a meantime dropped by more than a predetermined extent; and

otherwise the timer is stopped and/or reset.

6. The method according to claim 1 , which further comprises:
starting the timer with a delay, specifically at a predetermined subsequent instant after generation of the short-circuit detection signal, when:
the short-circuit detection signal is still present at the predetermined subsequent instant;
an active power has in a meantime dropped by more than a predetermined extent; and

otherwise the timer is not started.

7. The method according to claim 1 , wherein the set of the predetermined trigger conditions contains at least one of following trigger conditions:
a trigger condition that a positive-sequence voltage falls below a minimum predetermined positive-sequence voltage value;
a trigger condition that phase currents, or at least one thereof, respectively exceed a predetermined maximum phase current value;
a trigger condition that an active power falls below a predetermined minimum active power value;
a trigger condition that the active power has reached or exceeded a predetermined active-power setpoint value at a previous instant before an occurrence of at least one of the other trigger conditions; and
a trigger condition that phase-to-phase voltages fall below a minimum voltage value.

8. The method according to claim 1 , which further comprises establishing the predetermined delay time in dependence on a respective power difference between power before generation of the short-circuit detection signal and the power at a respective current instant.

9. The method according to claim 1 , which further comprises establishing the predetermined delay time in dependence on a respective active power difference between an active power before generation of the short-circuit detection signal and the active power at a respective current instant.

10. The method according to claim 5 , wherein the stopping and/or the resetting of the timer is suppressed when at the predetermined subsequent instant after generation of the short-circuit detection signal the active power has dropped by more than a derivative value indicating a mathematical time derivative of the active power in dependence on time that has fallen below a predetermined negative threshold value.

11. The method according to claim 6 , wherein starting the timer with the delay, specifically at the predetermined subsequent instant after generation of the short-circuit detection signal, when the active power has dropped by more than the predetermined extent, namely a derivative value indicating a mathematical time derivative of the active power in dependence on time that has fallen below a predetermined negative threshold value.

12. The method according to claim 1 , wherein the set of predetermined trigger conditions are satisfied when the set of predetermined trigger conditions have remained satisfied continuously during a duration of the predetermined delay time.

13. A protection method for protecting an electrical generator or power station unit connected to a power distribution network or to a power transmission line, which comprises the steps of:
detecting a short circuit near the electrical generator or power station unit in the power distribution network or on the power transmission line;
generating a short-circuit detection signal when a set of predetermined trigger conditions is satisfied;
disconnecting the electrical generator or power station unit from the power distribution network or the power transmission line if, after generation of the short-circuit detection signal, the set of predetermined trigger conditions are satisfied at an instant when a predetermined delay time elapses, the predetermined delay time being a variable duration which is reestablished before it elapses, in dependence on an operating profile after a short-circuit occurrence; and
establishing the predetermined delay time in dependence on a respective active power difference between an active power before detection of the short circuit and the active power at a respective current instant.

14. A protective device for protecting an electrical generator or power station unit connected to a power distribution network or to a power transmission line, the protective device comprising:
a short-circuit detection module for detecting a short circuit in the power distribution network or on the power transmission line and generates a short-circuit detection signal when a set of predetermined trigger conditions is satisfied;
a breaking module configured to disconnect the electrical generator or power station unit from the power distribution network or the power transmission line, or generate a breaking signal which initiates a disconnection, if, after generation of the short-circuit detection signal, the set of predetermined trigger conditions are satisfied at an instant when a predetermined delay time elapses;
a delay time determination module configured to reestablish the predetermined delay time as a variable duration before it elapses, in dependence on an operating profile after the short-cir

Assignees

• Siemens Ag

Inventors

• Herrmann Hans-Joachim
• Trunk Kai
• Eisenburger Edmund

Classifications

• H02J13/36

  specially adapted for protection systems · CPC title

• H02J13/13 Primary

  characterised by the transmission of data to equipment in the power network · CPC title

• Y04S40/12

  characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment · CPC title

• H02P9/006

  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

• H02H3/006

  Calibration or setting of parameters · CPC title