Method to detect signal corruption from conductive dust in a circuit breaker

Patent metadata

Field	Value
Publication number	US-12130312-B2
Application number	US-202217965558-A
Country	US
Kind code	B2
Filing date	Oct 13, 2022
Priority date	Oct 13, 2022
Publication date	Oct 29, 2024
Grant date	Oct 29, 2024

Abstract

Systems and methods are provided for monitoring the effects of conductive dust deposits that compromise the ability of a trip unit to accurately detect AC current in a circuit interrupter. When a Rogowski coil is used as a current sensor in the circuit interrupter and the trip unit processes the output of the Rogowski coil using a printed circuit board assembly (PCBA) processing circuit, the DC component of the processing circuit output signal can be analyzed to determine whether any conductive dust has formed unintended electrical pathways on the PCBA and compromised the ability of the PCBA to accurately measure AC current in the circuit interrupter. It can be determined that such unintended electrical pathways have formed when the DC component of the processing circuit output either exceeds a predetermined threshold or has increased by a significant amount after opening of the separable contacts.

First claim

What is claimed is:

1. A detection system for determining whether the AC current sensing ability of a trip unit has been compromised, the detection system comprising:
a sensor output processing circuit configured to receive and process sensed output from a current sensor of the circuit interrupter, and to output a processed output signal representative of the current flowing through the circuit interrupter; and
a controller configured to receive the processed output signal and to analyze the processed output signal,
wherein the controller is configured to isolate a DC component of the processed output signal from an AC component of the processed output signal,
wherein the controller is configured to compare the DC component of the processed output signal to a predetermined acceptable DC component threshold, and to determine whether the DC component of the processed output signal reflects an unacceptable increase from a previously detected DC component of a next-most recently previously analyzed processed output signal, and
wherein the controller is configured to issue an alarm if the controller determines that the DC component of the processed output signal either: exceeds the predetermined acceptable DC component threshold or reflects the unacceptable increase.

2. The detection system of claim 1 ,
wherein the current sensor is a Rogowski coil with output terminals, and the sensed output from the current sensor is a non-integrated voltage signal across the output terminals of the Rogowski coil that is proportional to a rate of change of the current flowing through the circuit interrupter.

3. The detection system of claim 2 ,
wherein either the sensor processing circuit comprises circuitry configured to integrate the non-integrated voltage signal, or the controller is configured to digitally integrate the processed output signal.

4. The detection system of claim 2 ,
wherein the sensor output processing circuit comprises a resistor, a capacitor, and an operational amplifier, the operational amplifier comprising a non-inverting input terminal and an inverting input terminal,
wherein the Rogowski coil output terminals are connected in series between the operational amplifier non-inverting input terminal and ground reference voltage, and
wherein the resistor and the capacitor are connected in series across the Rogowski coil output terminals, such that voltage across the capacitor is input to the operational amplifier non-inverting input terminal.

5. The detection system of claim 4 ,
wherein the resistor and the capacitor form an AC integrator.

6. The detection system of claim 4 ,
wherein the resistor and the capacitor form a filter, and
wherein the controller is configured to digitally integrate an output signal of the operational amplifier.

7. A method of determining whether the AC current sensing ability of a circuit interrupter has been compromised, the method comprising:
receiving an output of a current sensor as an input to a sensor output processing circuit, the current sensor being configured to sense AC current through the circuit interrupter;
processing the current sensor output with the sensor output processing circuit to produce a processed output signal representative of current flowing through the circuit interrupter;
isolating, with a controller configured to receive the processed output signal, a DC component of the processed output signal;
comparing, with the controller, the DC component of the processed output signal to a predetermined acceptable DC component threshold and to previously detected DC component levels with the controller; and
issuing an alarm with the controller if the controller determines that the DC component of the processed output signal either exceeds the predetermined acceptable DC component threshold or reflects an unacceptable increase from the previously detected DC component levels.

8. The method of claim 7 ,
wherein the current sensor is a Rogowski coil with output terminals, and the current sensor output is a non-integrated voltage signal across the output terminals of the Rogowski coil that is proportional to a rate of change of the current flowing through the circuit interrupter.

9. The method of claim 8 , further comprising:
integrating the non-integrated voltage signal either with the sensor output processing circuit or with the controller.

10. The method of claim 8 ,
wherein the sensor output processing circuit comprises a resistor, a capacitor, and an operational amplifier, the operational amplifier comprising a non-inverting input terminal and an inverting input terminal,
wherein the Rogowski coil output terminals are connected in series between the operational amplifier non-inverting input terminal and ground reference voltage, and
wherein the resistor and the capacitor are connected in series across the Rogowski coil output terminals, such that voltage across the capacitor is input to the operational amplifier non-inverting input terminal.

11. The method of claim 10 , further comprising:
integrating the non-integrated voltage signal with the resistor and the capacitor.

12. The method of claim 10 , further comprising:
filtering the non-integrated voltage signal with a filter comprising the resistor and the capacitor, and
digitally integrating an output signal of the operational amplifier with the controller.

13. A circuit interrupter structured to be electrically connected between a power source and a load, the circuit interrupter comprising:
a pair of separable contacts comprising a stationary contact and a movable contact disposed between the power source and the load;
a Rogowski coil configured to sense current flowing between the power source and the load, the Rogowski coil comprising output terminals; and
an electronic trip unit, the electronic trip unit comprising:
a printed circuit board assembly, PCBA, comprising a sensor output processing circuit; and
a controller,

wherein the sensor output processing circuit is configured to receive and process a signal output by the Rogowski coil output terminals, and to output a processed output signal representative of the current flowing through the circuit interrupter,
wherein the controller is configured to receive and analyze the processed output signal,
wherein the controller is configured to isolate a DC component of the processed output signal from an AC component of the processed output signal,
wherein the controller is configured to compare the DC component of the processed output signal to a predetermined acceptable DC component threshold, and to determine whether the DC component of the processed output signal reflects an unacceptable increase from a previously detected DC component of a next-most recently previously analyzed processed output signal, and
wherein the controller is configured to issue an alarm if the controller determines that the DC component of the processed output signal either: exceeds the predetermined acceptable DC component threshold or reflects the unacceptable increase.

14. The circuit interrupter of claim 13 ,
wherein the signal output by the Rogowski coil output terminals is a non-integrated voltage signal that is proportional to a rate of change of the current flowing through the circuit interrupter,
wherein either the sensor output processing circuit comprises circuitry configured to integrate the non-integrated voltage signal, or the controller is configured to digitally integrate the processed output signal.

15. The circuit interrupter of claim 13 ,
wherein the sensor output processing circuit comprises a resistor, a capacito

Assignees

• Eaton Intelligent Power Ltd

Inventors

• Miller Theodore J
• Wise James I
• Rohn David

Classifications

• G08B21/185

  Electrical failure alarms · CPC title

• G01R15/181 Primary

  using coils without a magnetic core, e.g. Rogowski coils · CPC title

• G01R31/3275

  Fault detection or status indication · CPC title

• G01R19/16571 Primary

  comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current (G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533, G01R19/1659 take precedence; measuring currents by using elements sensitive to the magnetic field generated G01R15/14; measuring earth resistance G01R27/18; testing for leakage or short circuits in electrical apparatus G01R31/52) · CPC title