Apparatuses and methods for passive fault monitoring of current sensing devices in protective circuit interrupters

Patent metadata

Field	Value
Publication number	US-11408940-B2
Application number	US-202016797152-A
Country	US
Kind code	B2
Filing date	Feb 21, 2020
Priority date	Nov 26, 2014
Publication date	Aug 9, 2022
Grant date	Aug 9, 2022

Abstract

Passive monitoring the integrity of current sensing devices and associated circuitry in GFCI and AFCI protective devices is provided. A protection circuit interrupter employs a capacitively coupled noise signal obtained by an arrangement of one or both of the line side arms relative to a Rogowski coil. The noise signal is monitored while the line and load sides of a protective circuit interrupter are disconnected, and the connection of the line and load sides disabled if the noise signal fails to correlate sufficiently to a reference noise cycle. When the line and load sides are connected, the RMS value of the observed current signal is monitored such that the line and load sides are disconnected if the observed current signal fails to meet an RMS threshold. The observed current signal is compensated by subtracting the reference noise cycle prior to monitoring for the fault condition applicable to the protective device.

First claim

What is claimed is:

1. A method of monitoring components in a protection device interrupter comprising:
capacitively coupling at least one of a line hot arm and a line neutral arm in the protection device interrupter to a current sensing coil;
monitoring the coil and analog components of the protection device interrupter while the line hot arm and a line neutral arm are disconnected, respectively, from a load hot arm and a load neutral of the protection device interrupter by using a noise signal created by the capacitively coupling when the line hot arm and a line neutral arm are disconnected, respectively, from a load hot arm and a load neutral of the protection device interrupter.

2. The method of claim 1 , wherein the analog components comprise at least one of analog signal conditioning circuitry and an analog to digital input of a digital processor in the protection device interrupter.

3. The method of claim 1 , further comprising:
analyzing the noise signal created by the capacitively coupling when the line hot arm and a line neutral arm are disconnected, respectively, from the load hot arm and the load neutral of the protection device interrupter to determine reference noise data; and
disabling connection of the line hot arm and the line neutral arm to, respectively, the load hot arm and the load neutral when the noise signal meets a first designated criterion with respect to the reference noise data.

4. The method of claim 3 , further comprising:
analyzing a current signal from the coil when the line hot arm and the line neutral arm are connected, respectively, to the load hot arm and the load neutral; and
disconnecting line hot arm and the line neutral arm, respectively, from the load hot arm and the load neutral when the current signal satisfies a second designated criterion with respect to the reference noise data.

5. The method of claim 1 , wherein the other one of the line hot arm and the line neutral arm is disposed relative to the coil to create current flow in the same direction through each of the line hot arm and the line neutral arm and reinforce the observed current signal.

6. The method of claim 3 , further comprising:
averaging cycles of the noise signal while the line hot arm and the line neutral arm, respectively, are disconnected from the load hot arm and the load neutral to determine a reference noise cycle and a threshold represented by a root mean square value of the reference noise cycle;
wherein the monitoring comprises correlating the noise signal with the reference noise cycle, the first designated criterion corresponds to a selected threshold of correlation, and the disabling is performed when the correlating results in correlation below the selected threshold.

7. The method of claim 6 , wherein the selected threshold of correlation is 0.976.

8. The method of claim 1 , wherein the coil is a Rogowski coil.

9. The method of claim 4 , further comprising:
averaging cycles of the noise signal while the line hot arm and the line neutral arm, respectively, are disconnected from the load hot arm and the load neutral to determine a reference noise cycle and a threshold represented by a root mean square value of the reference noise cycle;
wherein the second designated criterion corresponds to the threshold, and the disconnecting comprises disconnecting the line hot arm and the line neutral arm, respectively, from the load hot arm and the load neutral when the current signal is less than the threshold or greater than the threshold by a selected amount.

10. A protection device interrupter comprising:
a line hot arm and a line neutral arm connected to a load hot arm and a load neutral arm, respectively, via a switching device;
a current sensing coil, at least one of the line hot arm and the line neutral arm are capacitively coupled to the current sensing coil;
a processor; and
analog components for conditioning a signal representing current sensed by the coil for processing by the processor, the analog components comprising at least one of analog signal conditioning circuitry, an analog to digital converter, and an analog to digital input of the processor;
wherein the processor is configured to monitor the current sensing coil and the analog components while the line hot arm and a line neutral arm are disconnected, respectively, from the load hot arm and the load neutral using a noise signal created by the capacitively coupling when the line hot arm and a line neutral arm are disconnected, respectively, from a load hot arm and a load neutral.

11. The protection device interrupter of claim 10 , wherein the current sensing coil is a Rogowski coil.

12. The protection device interrupter of claim 10 , wherein the other one of the line hot arm and the line neutral arm is disposed relative to the coil to create current flow in the same direction through each of the line hot arm and the line neutral arm and reinforce the observed current signal.

13. The protection device interrupter of claim 10 , wherein the processor is further configured to:
analyze the noise signal created by the capacitively coupling when the line hot arm and a line neutral arm are disconnected, respectively, from a load hot arm and a load neutral to determine reference noise data; and
disable connection of the line hot arm and the line neutral arm to, respectively, the load hot arm and the load neutral when the noise signal meets a first designated criterion with respect to the reference noise data.

14. The protection device interrupter of claim 13 , wherein the processor is further configured to:
average cycles of the noise signal while the line hot arm and the line neutral arm, respectively, are disconnected from the load hot arm and the load neutral to determine a reference noise cycle and a threshold represented by a root mean square value of the reference noise cycle;
wherein the processor monitors the current sensing coil and the analog components while the line hot arm and a line neutral arm are disconnected by correlating the noise signal with the reference noise cycle, the first designated criterion corresponding to a selected threshold of correlation; and
wherein the processor disables connection of the line hot arm and the line neutral arm to, respectively, the load hot arm and the load neutral when the correlating results in correlation below the selected threshold.

15. The method of claim 14 , wherein the selected threshold of correlation is 0.976.

16. The protection device interrupter of claim 10 , wherein the processor is further configured to:
analyze the noise signal created by the capacitively coupling when the line hot arm and a line neutral arm are disconnected, respectively, from the load hot arm and the load neutral of the protection device interrupter to determine reference noise data; and
analyze a current signal from the coil when the line hot arm and the line neutral arm are connected, respectively, to the load hot arm and the load neutral, and
operate the switching device to disconnect the line hot arm and the line neutral arm, respectively, from the load hot arm and the load neutral when the current signal satisfies a second designated criterion with respect to the reference noise data.

17. The protection device interrupter of claim 16 , wherein the processor is further configured to:
average cycles of the noise signal while the line hot arm and the line neutral arm, respectively, are disconnected from the load hot arm and the load neutral to determine a reference noise cycle and a threshold represented by a root mean square value of the ref

Assignees

• Hubbell Inc

Inventors

• Miller Gary Michael
• Miller Iii William Vernon
• Chen Edward Shi

Classifications

• H02H3/331

  responsive to earthing of the neutral conductor (H02H3/338 takes precedence) · CPC title

• H02H1/0015

  Using arc detectors · CPC title

• G01R31/3277 Primary

  of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches · CPC title

• H02H3/28

  involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus {(for transformers H02H7/045)} · CPC title

• H02H3/16

  responsive to fault current to earth, frame or mass (with balanced or differential arrangement H02H3/26 {; monitoring earth connection H02H5/105}) · CPC title