Method and apparatus for determining the wear on a contact element

Patent metadata

Field	Value
Publication number	US-9406451-B2
Application number	US-201213480927-A
Country	US
Kind code	B2
Filing date	May 25, 2012
Priority date	Nov 25, 2009
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

A method for determining the wear on a contact element of an electrical switch, for example, of a switching installation for high or medium voltage, includes recording electrical values which represent an electrical variable, which is relevant to an arc occurring at the switch during a switching operation, as a function of time, and calculating a wear value, which represents the wear on the contact element, from a plurality of wear contribution values. The wear contribution values are calculated from a plurality of subsets of the recorded electrical values using a plurality of wear contribution calculation rules, with the result that each of the wear contribution values is calculated from a respective one of the subsets of values according to a respective one of the wear contribution calculation rules. At least two of the wear contribution calculation rules differ from one another.

First claim

What is claimed is:

1. A method for determining the wear on a contact element of an electrical switch, the method comprising:
recording electrical values (I(t), U(t)) which represent an electrical variable, which is relevant to an arc occurring at the switch during a switching operation, as a function of time; and
calculating a wear value (d), which represents the wear on the contact element, from a plurality of wear contribution values,
wherein the wear contribution values are calculated from a plurality of subsets (I(t i ); I([t i ;t′ i ])) of the recorded electrical values using a plurality of wear contribution calculation rules (f i ), such that each of the wear contribution values is calculated from a respective one of the subsets of values (I(t i ); I([t i ;t′ i ])) according to a respective one of the wear contribution calculation rules (f i ),
wherein at least two of the wear contribution calculation rules (f i ) differ from one another, and
wherein the method comprises:
calculating, based on the calculated wear value, a percentage wear of the contact element of the electrical switch, as a proportion of a maximum wear value that the calculated wear value constitutes;
determining whether the calculated percentage wear is greater than a predefined warning threshold value; and
outputting a command to block operation of the electrical switch when the calculated percentage wear is determined to be greater than the predefined warning threshold value.

2. The method as claimed in claim 1 , wherein the calculating of the wear value (d) comprises:
determining a transition time (t i , t′ i ) which is characteristic of a change in the wear contribution calculation rule,
wherein the at least one transition time represents a respective transition between different phases of an arc occurring during the switching operation.

3. The method as claimed in claim 2 , wherein the calculating of the wear value (d) comprises:
defining at least one of the subsets of values (I(t i ); I([t i ; t′ i ])) taking into account the at least one transition time (t i , t i ) which has been determined.

4. The method as claimed in claim 3 , wherein the subsets of values (I([t i ;t′ i ])) comprise electrical values associated with a respective interval of time ([t i ;t′ i ]),
wherein the method comprises:
for each of the intervals of time, stipulating the start (t i ), the end (t′ i ) or the start and the end of the respective interval of time ([t i ;t′ i ]) by means of at least one respective limit time (t i , t′ i ), and
wherein the at least one limit time is the at least one transition time.

5. The method as claimed in claim 3 , wherein the at least one transition time includes a first transition time (t 1 ) and a second transition time (t 2 ), and
wherein the plurality of subsets of values comprise at least a first, a second and a third subset of values (I([t 0 ;t 1 ]); I([t 1 ;t 2 ]), I([t 2 ;t 3 ])).

6. The method as claimed in claim 2 , wherein the subsets of values (I([t i ;t′ i ])) comprise electrical values associated with a respective interval of time ([t i ;t′ i ]),
wherein the method comprises:
for each of the intervals of time, stipulating the start (t i ), the end (t′ i ) or the start and the end of the respective interval of time ([t i ;t′ i ])by means of at least one respective limit time (t i , t i ), and
wherein the at least one limit time is the at least one transition time.

7. The method as claimed in claim 2 , wherein the at least one transition time includes a first transition time (t i ) and a second transition time (t 2 ), and
wherein the plurality of subsets of values comprise at least a first, a second and a third subset of values (I([t 0 ;t 1 ]); I([t 1 ;t 2 ]), I([t 2 ;t 3 ])).

8. The method as claimed in claim 1 , wherein the calculating of the wear value (d) comprises:
determining at least one limit time (t i , t′ i ),
wherein the at least one limit time is the at least one transition time, and
wherein the at least one limit time is determined taking into account at least one respective value selected from a first list including:
a current value;
a voltage value;
a value of an electric or magnetic field;
a noise component or frequency component of a current value;
a noise component or frequency component of a voltage value;
a noise component or frequency component of an electric or magnetic field;
a brightness value of an arc;
a position value which describes a position of the contact surface and/or a distance between two contact surfaces;
a previous wear value;
a previous total wear value;
a period of time elapsed since the occurrence of an event;
a period of time elapsed since an earlier limit time.

9. The method as claimed in claim 8 , wherein the event is selected from a list including:
a. the start of an arc;
b. a transition from a stationary arc state to a wandering arc state;
c. a transition from a diffuse arc to a constricted arc;
d. the end of an arc;
e. a separation of a contact element from a further contact element of the switch;
f. a removal of the contact element from a further contact element of the switch by a distance which exceeds a predefined distance threshold value;
g. an issue or evaluation of a switching command;
h. an overshooting or undershooting of a predetermined threshold value by a recorded value.

10. The method as claimed in claim 1 , wherein the switch is a vacuum switch.

11. The method as claimed in claim 10 , wherein the switch is comprised in a switching installation for a high or medium voltage.

12. The method as claimed in claim 1 , wherein the calculating of the wear value (d) comprises:
determining at least one limit time (t i , t′ i ),
wherein the at least one limit time is the at least one transition time, and
wherein the at least one limit time is determined taking into account at least one respective event selected from a first list including:
a. the start of an arc;
b. a transition from a stationary arc state to a wandering arc state;
c. a transition from a diffuse arc to a constricted arc;
d. the end of an arc;
e. a separation of a contact element from a further contact element of the switch;
f. a removal of the contact element from a further contact element of the switch by a distance which exceeds a predefined distance threshold value;
g. an issue or evaluation of a switching command;
h. an overshooting or undershooting of a predetermined threshold value by a recorded value, wherein the recorded value is selected from at least one value in a second list including:
a current value;
a voltage value;
a value of an electric or magnetic field;
a noise component or frequency component of a current value;
a noise component or frequency component of a voltage value;
a noise component or frequency component of an electric or magnetic field;
a brightness value of an arc;
a position value which describes a position of the contact surface and/or a distance between two contact surfaces;
a previous wear value or previous total wear value;
a period of time elapsed since the occurrence of any further event identified in the first list; and
a period of time elapsed since an earlier limit time.

13. The method as claimed in claim 1 , wherein the subsets of values (I(t i ); I([t i ;t′ i ])) are determined as the electrical values associated with a respective interval of time ([t i t′ i]), and
wherein the calculation of the wear value (d) includes forming a sum or an integral of the wear contribution values.

14. The method as claimed in claim 1 , wherein the calculating of the wear value (d) compris

Assignees

• Schrag Daniel
• Hencken Kai
• Smajic Eldin
• Abb Research Ltd

Inventors

• Schrag Daniel
• Hencken Kai
• Smajic Eldin

Classifications

• H01H33/6643

  having disc-shaped contacts subdivided in petal-like segments, e.g. by helical grooves · CPC title

• H01H1/0015 Primary

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

• H01H2001/0031

  by analysing radiation emitted by arc or trace material · CPC title