Methods for detecting an open current transformer

Patent metadata

Field	Value
Publication number	US-9568535-B2
Application number	US-201214354936-A
Country	US
Kind code	B2
Filing date	Oct 31, 2012
Priority date	Nov 4, 2011
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

A method for detecting an open current transformer in an electrical power system includes measuring for a voltage value on a secondary side of a current transformer. The method continues with observing the voltage value for a predetermined waveform and initiating corrective action in the electrical power system upon detection of the predetermined waveform.

First claim

What is claimed is:

1. A method for detecting an open current transformer in an electrical power system, comprising:
measuring for a voltage on a secondary side of a current transformer;
observing said voltage for a predetermined waveform;
detecting a signature of said predetermined waveform in said observed voltage, said signature of said predetermined waveform showing a decaying harmonic waveform; and
initiating corrective action in the electrical power system upon detecting said signature of said predetermined waveform in said observed voltage.

2. The method according to claim 1 , further comprising:
observing whether said decaying harmonic waveform of said signature includes third and fifth harmonics before initiating corrective action.

3. The method according to claim 1 , further comprising:
initiating corrective action only if said decaying harmonic waveform is detected and no current is detected in said secondary side of said current transformer.

4. The method according to claim 1 , further comprising:
measuring for said voltage between at least one leg of said current transformer and ground.

5. The method according to claim 2 , further comprising:
applying a Fast Fourier Transform analysis to said observed voltage to generate a waveform for comparison to said predetermined waveform.

6. The method according to claim 5 , further comprising:
initiating corrective action upon first detection of a fundamental, third and fifth harmonic of said observed voltage.

Assignees

• Abb Research Ltd
• Abb Research Ltd

Inventors

• Ball Roy

Classifications

• G01R31/62

  Testing of transformers · CPC title

• H02H3/52 Primary

  responsive to the appearance of harmonics · CPC title

• H02H3/044

  Checking correct functioning of protective arrangements, e.g. by simulating a fault (for differential current circuit breakers H02H3/335) · CPC title

• H02H7/042

  for current transformers · CPC title

• G01R15/18

  using inductive devices, e.g. transformers · CPC title