Method and protection device for monitoring circuit breaker in an electrical power supply network

Patent metadata

Field	Value
Publication number	US-10777992-B2
Application number	US-201615353868-A
Country	US
Kind code	B2
Filing date	Nov 17, 2016
Priority date	Nov 17, 2015
Publication date	Sep 15, 2020
Grant date	Sep 15, 2020

Abstract

A method monitors a circuit breaker in an electrical power supply network, in which one section of the electrical power supply network is monitored in respect of the occurrence of a fault. Upon detection of a fault in the monitored section, a trigger signal is output to a circuit breaker bordering the section, and a switch-fault signal indicating a fault upon opening the circuit breaker is generated if a continuous current flow through the circuit breaker is detected after the trigger signal is output. In order to provide for a preferably rapid and reliable detection of a continuous current flow or an interruption of the current flow during the monitoring of a circuit breaker, it is provided that a curve shape of the time curve of the instantaneous current flowing through the circuit breaker is investigated in order to detect a continuous current flow.

First claim

The invention claimed is:

1. A protective device for monitoring a circuit breaker in an electrical power supply network, comprising:
a control device configured to:
generate a switch-fault signal indicating a fault upon an opening of the circuit breaker if a continuous current flow through the circuit breaker is detected after a trigger signal for the circuit breaker is output;
design the control device to investigate a curve shape of a time curve of an instantaneous current flowing through the contacts of the circuit breaker in respect of a presence of at least one criterion characterizing the curve shape, namely investigating a periodicity of a progression as the criterion, in order to detect the continuous current flow;
deduce on a basis of the criterion, the continuous current flow or an interrupted current flow;
deduce a continuity of a current flow through the circuit breaker when the periodicity of the progression is detected;
investigate a decay behavior of the progression as one further criterion, in an absence of the periodicity of the progression, by:
investigating a mean value of the progression of the instantaneous current through the contacts of the circuit breaker and a gradient of the progression of the instantaneous current in order to detect the decay behavior; and
deducing, in a case of a positive mean value and a negative gradient or a negative mean value and a positive gradient, a presence of the decay behavior; and

deduce an interruption of the current flow through the circuit breaker when the decay behavior of the progression is detected; and

investigate the progression within a predefined time window, and a length of the predefined time window is adaptively determined.

2. A method for monitoring a circuit breaker in an electrical power supply network, which comprises the steps of:
monitoring one section of the electrical power supply network for an occurrence of a fault;
outputting, upon detection of the fault in a monitored section, a trigger signal to the circuit breaker bordering the monitored section;
generating a switch-fault signal indicating the fault upon an opening of the circuit breaker if a continuous current flow through the circuit breaker is detected after the trigger signal is output;
investigating a curve shape of a time curve of an instantaneous current flowing through the contacts of the circuit breaker in respect of a presence of at least one criterion characterizing the curve shape, namely investigating a periodicity of a progression as the criterion, to detect the continuous current flow;
deducing on a basis of the criterion, the continuous current flow or an interrupted current flow;
deducing a continuity of a current flow through the circuit breaker when the periodicity of the progression is detected;
investigating a decay behavior of the progression as one further criterion, in an absence of the periodicity of the progression, the investigating step includes the sub-steps of;
investigating a mean value of the progression of the instantaneous current through the contacts of the circuit breaker and a gradient of the progression of the instantaneous current in order to detect the decay behavior; and
deducing, in a case of a positive mean value and a negative gradient or a negative mean value and a positive gradient, a presence of the decay behavior; and

deducing an interruption of the current flow through the circuit breaker when the decay behavior of the progression is detected; and
investigating the progression within a predefined time window, and a length of the predefined time window is adaptively determined.

3. The method according to claim 2 , which further comprises investigating the periodicity of the progression on a basis of at least one of local extremes or inflection points which occur.

4. The method according to claim 2 , which further comprises:
investigating an amplitude of the progression as one further criterion; and
deducing an interruption of the current flow through the circuit breaker when the amplitude of the progression falls below an amplitude threshold value.

5. The method according to claim 4 , which further comprises determining the amplitude as a peak-to-peak amplitude of the progression.

6. The method according to claim 4 , which further comprises deducing an interruption of the current flow in a case of the amplitude of the progression, which lies below the amplitude threshold value, when the periodicity of the progression has been detected.

7. The method according to claim 2 , wherein:
in order to adaptively determine the length of the predefine time window, an investigation is initially started with a minimum length of the predefined time window; and
the length of the predefined time window is increased for as long as an interruption of the current flow is detected during a learning phase immediately following a point in time at which a shutoff signal is output, a duration of the learning phase is determined depending on a reaction time of the circuit breaker.

8. The method according to claim 2 , which further comprises:
carrying out an investigation of the curve shape of the progression repeatedly during an investigation period; and
generating the switch-fault signal when the continuous current flow is determined at an end of the investigation period.

9. The method according to claim 8 , wherein a selection of criteria to be considered for the investigation of the progression depends on whether an interruption of the current flow has already been detected in a previous run of the investigation.

10. The method according to claim 2 , wherein if the switch-fault signal is present:
outputting a new trigger signal to the circuit breaker; and/or
outputting an auxiliary trigger signal to at least one further circuit breaker installed upstream from the circuit breaker.

Assignees

• Siemens Ag

Inventors

• Blumschein Joerg
• Neugebauer Olaf
• Yelgin Yilmaz

Classifications

• G01R31/3333 Primary

  Apparatus, systems or circuits therefor · CPC title

• G01R31/50

  Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections (testing of sparking plugs H01T13/58) · CPC title

• H02H7/26 Primary

  Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured (locating faults in cables G01R31/08) · CPC title

• H01H9/54

  Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere · CPC title

• H01H33/59

  Circuit arrangements not adapted to a particular application of the switch and not otherwise provided for, e.g. for ensuring operation of the switch at a predetermined point in the AC cycle · CPC title