System and method for monitoring contact life of a circuit interrupter

Patent metadata

Field	Value
Publication number	US-10332698-B2
Application number	US-201615386953-A
Country	US
Kind code	B2
Filing date	Dec 21, 2016
Priority date	Dec 21, 2016
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

An electronic trip unit for a circuit interrupter includes a line side voltage sensing module for measuring first voltages on a line side of separable contacts, a load side voltage sensing module for measuring second voltages on a load side of the separable contacts, a current sensor, and a main controller. The main controller is further structured and configured to: (i) for each of a plurality of arc interruption events in the circuit interrupter, determine a mass loss due to contact erosion during the arc interruption event based on one or more of the first voltages, the second voltages and the current measured by the current sensor, (ii) determine a total mass loss based on each determined mass loss due to contact erosion, and (iii) monitor a remaining life of the separable contacts based on the determined total mass loss due to contact erosion.

First claim

What is claimed is:

1. An electronic trip unit for a circuit interrupter, the circuit interrupter having a set of separable contacts, the electronic trip unit comprising:
a line side voltage sensing module structured to measure first voltages on a line side of the separable contacts;
a load side voltage sensing module structured to measure second voltages on a load side of the separable contacts;
a current sensor structured to measure a current flowing through a line to which the separable contacts are coupled; and
a main controller structured and configured to receive first voltage information based on measurements made by the line side voltage sensing module, second voltage information based on measurements made by the load side voltage sensing module, and current information based on measurements made by the current sensor, wherein the main controller is further structured and configured to: (i) for each of a plurality of arc interruption events in the circuit interrupter, calculate an amount of mass lost by the separable contacts due to contact erosion during the arc interruption event based on one or more of the first voltage information, the second voltage information and the current information, (ii) determine a total mass loss due to contact erosion as a sum of each calculated amount of mass lost by the separable contacts due to contact erosion, and (iii) monitor a remaining life of the separable contacts based on the determined total mass loss due to contact erosion.

2. The electronic trip unit according to claim 1 , wherein the main controller is structured and configured to, for each of the plurality of arc interruption events, determine the amount of mass lost by the separable contacts due to contact erosion during the arc interruption event by determining total arc energy for the arc interruption event based on the first voltage information, the second voltage information and the current information and by calculating the amount of mass lost by the separable contacts due to contact erosion during the arc interruption event based on the determined total arc energy.

3. The electronic trip unit according to claim 2 , wherein total arc energy for the arc interruption event is determined based on the following expression:
W=∫ 0 t VIdt (Joule),

where W is the total arc energy for the arc interruption event, t is an arcing time for the arc interruption event, V is arc voltage determined from the first voltage information and the second voltage information, and I is arc current determined from the current information.

4. The electronic trip unit according to claim 3 , wherein the amount of mass lost by the separable contacts due to contact erosion during the arc interruption event is calculated based on the following equation:

Δ
⁢

⁢
m

=

K
×

ϕ
⁡

(

mg
Joule

)

×

W
⁡

(
Joule
)

,

where Δm is the amount of mass lost by the separable contacts due to contact erosion during the arc interruption event, ϕ is a mass loss per Joule for a material used in the separable contacts, and K is a coefficient that reflects a time duration during which an arc stays on the separable contacts.

5. The electronic trip unit according to claim 1 , wherein the main controller is structured and configured to, for each of the plurality of arc interruption events, determine the amount of mass lost by the separable contacts due to contact erosion during the arc interruption event by determining total electrical charges for the arc interruption event based on the current information and by calculating the mass loss due to contact erosion during the arc interruption event based on the determined total electrical charges.

6. The electronic trip unit according to claim 5 , wherein total electrical charges for the arc interruption event is determined based on the following expression:
Q=∫ 0 t Idt (Coulomb),

where Q is the total electrical charges and t is an arcing time of the arc interruption event.

7. The electronic trip unit according to claim 6 , wherein the amount of mass lost by the separable contacts due to contact erosion during the arc interruption event is calculated based on the following equation:

Δ
⁢

⁢
m

=

K
×

δ
⁡

(

mg
Coulomb

)

×

Q
⁡

(
Coulomb
)

,

where Δm is the amount of mass lost by the separable contacts due to contact erosion during the arc interruption event, δ is a mass loss per Coulomb of electrical charge for a material used in the separable contacts, and K is a coefficient that reflects a time duration during which an arc stays on the separable contacts.

8. The electronic trip unit according to claim 1 , wherein the remaining life of the separable contacts is monitored based on the determined total mass loss due to contact erosion as subtracted from an original contact mass for the circuit interrupter.

9. The electronic trip unit according to claim 1 , wherein the main controller is structured and configured to make a determination regarding the remaining life of the separable contacts based on the determined total mass loss due to contact erosion, and cause an output regarding contact life status for the circuit interrupter to be generated based on at least the determination regarding the remaining life of the separable contacts.

10. The electronic trip unit according to claim 9 , wherein the main controller is structured and configured to make the determination regarding the remaining life of the separable contacts by comparing the determined total mass loss due to contact erosion to one or more threshold values.

11. A method of monitoring a set of separable contacts of a circuit interrupter, comprising:
measuring first voltages on a line side of the separable contacts;
measuring second voltages on a load side of the separable contacts;
measuring a current flowing through a line to which the separable contacts are coupled;
receiving first voltage information based on the measured first vo

Assignees

• Eaton Corp
• Eaton Intelligent Power Ltd

Inventors

• Zhou Xin
• Gao Zhi
• Lagree James L
• Mueller Robert W

Classifications

• G01R31/3277

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

• H01H71/04

  Means for indicating condition of the switching device {(by means of an auxiliary contact H01H71/46)} · CPC title

• H01H1/0015 Primary

  Means for testing or for inspecting contacts, e.g. wear indicator (measuring circuits G01R31/3274) · CPC title

• H01H9/54 Primary

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

• H01H2071/044

  Monitoring, detection or measuring systems to establish the end of life of the switching device, can also contain other on-line monitoring systems, e.g. for detecting mechanical failures · CPC title