Method for detecting an open-phase condition of a transformer

Patent metadata

Field	Value
Publication number	US-10931094-B2
Application number	US-201916727227-A
Country	US
Kind code	B2
Filing date	Dec 26, 2019
Priority date	Feb 21, 2014
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A method for detecting an open-phase condition of a transformer having a grounded-wye high voltage side connection including monitoring current flowing in a neutral connection on the high voltage side of the transformer in real time by voltage relaying and current relaying to identify an open phase condition signature in a signal capable of characterizing change of current magnitude. A current signal may be injected onto the neutral terminal and the zero-sequence mode of the transformer monitored to detect an open-phase condition indicated by an increase in network impedance and decrease or elimination of the injection current.

First claim

We claim:

1. A method for detecting an open-phase condition of a transformer in a low load or no-load condition and having a grounded-wye high voltage side connection comprising monitoring current flowing in a neutral connection on the high voltage side of the transformer by voltage relaying or current relaying to identify an open phase condition signature in a signal capable of characterizing change of current magnitude, wherein the transformer is a wye-delta transformer, a wye-wye three-legged core transformer, a wye-wye three-legged core with buried delta transformer, or a wye-wye shell core with buried delta transformer, including monitoring transformer network zero-sequence impedance, and wherein the open-phase signature comprises an increase in impedance from hundreds or thousands of Ohms to Mega-Ohms.

2. The method according to claim 1 , wherein the monitoring is in real time.

3. The method according to claim 1 , including voltage monitoring and/or current monitoring on a transformer neutral terminal.

4. The method according to claim 1 , wherein the transformer is a station auxiliary transformer.

5. The method according to claim 1 , wherein the transformer is a startup transformer.

6. A method for detecting an open-phase condition of a transformer in a low load or no-load condition and having a grounded-wye high voltage side connection comprising monitoring current flowing in a neutral connection on the high voltage side of the transformer by voltage relaying or current relaying to identify an open phase condition signature in a signal capable of characterizing change of current magnitude, including monitoring transformer network zero-sequence impedance, and wherein the open-phase signature comprises an increase in impedance from hundreds or thousands of Ohms to Mega-Ohms.

7. The method according to claim 6 , wherein the monitoring is in real time.

8. The method according to claim 6 , including voltage monitoring and/or current monitoring on a transformer neutral terminal.

9. The method according to claim 6 , wherein the transformer is a station auxiliary transformer.

10. The method according to claim 6 , wherein the transformer is a startup transformer.

11. A method for detecting an open-phase condition of a transformer in a low load or no-load condition and having a grounded-wye high voltage side connection, comprising injecting a signal onto a neutral connection of the transformer, and, monitoring current flowing in a neutral connection on the high voltage side of the transformer to identify an open-phase condition signature in a signal capable of characterizing change of current magnitude, wherein when the injected signal or neutral current frequency is 60 Hz, the open phase condition signature comprises at least one of a decrease in a 180 Hz component of the neutral current, an increase in a 60 Hz component of the neutral current, or an increase in a 300 Hz component of the neutral current.

12. A method for detecting an open-phase condition of a transformer in a low load or no-load condition and having a grounded-wye high voltage side connection, comprising injecting a signal onto a neutral connection of the transformer, and, monitoring current flowing in a neutral connection on the high voltage side of the transformer to identify an open-phase condition signature in a signal capable of characterizing change of current magnitude, wherein the open-phase condition is detected by a change in power frequency current level in the neutral connection.

13. A method for detecting an open-phase condition of a transformer in a low load or no-load condition and having a grounded-wye high voltage side connection, comprising injecting a signal onto a neutral connection of the transformer, and, monitoring current flowing in a neutral connection on the high voltage side of the transformer to identify an open-phase condition signature in a signal capable of characterizing change of current magnitude, wherein the open-phase condition is detected by a change in a level of at least one harmonic of power frequency current in the neutral connection.

14. The method of claim 13 , wherein the change in the level of at least one harmonic is detected in a third and/or a fifth harmonic of the power frequency current, wherein said at least one harmonic is detected by Fast Fourier Transform.

Assignees

• Uab Res Found

Inventors

• Arritt Robert F
• Dugan Roger C
• Johnson Wayne E
• Franklin Gregory A

Classifications

• 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

• G01R31/08

  Locating faults in cables, transmission lines, or networks · CPC title

• H02H5/10 Primary

  responsive to mechanical injury, e.g. rupture of line, breakage of earth connection · CPC title

• H02H3/162

  for AC systems · CPC title

• H02H3/165 Primary

  for three-phase systems · CPC title