Method and apparatus for the measurement of a resistance of a switching contact of an electrical circuit breaker

Abstract

An apparatus and method for the measurement of a resistance of a switching contact of an electrical circuit breaker. A first resistance value across the circuit breaker is determined while the circuit breaker is grounded at both sides and the switching contact is closed. Further, a second resistance value across the circuit breaker is determined while the circuit breaker is grounded at both sides and the switching contact is open. The resistance of the closed switching contact is then determined based on the first resistance value and the second resistance value.

What is claimed is: 
     
         1 . A method for the measurement of a resistance of a switching contact of an electrical circuit breaker, comprising the steps:
 determining a first resistance value across the circuit breaker while the circuit breaker is grounded at both sides and the switching contact is closed;   determining a second resistance value across the circuit breaker while the circuit breaker is grounded at both sides and the switching contact is open; and   determining the resistance of the closed switching contact on the basis of the first resistance value and the second resistance value.   
     
     
         2 . The method according to  claim 1 , wherein the determining of the first and second resistance values respectively comprises:
 impressing a direct current in the circuit breaker which is grounded at both sides; and   measuring a voltage across the circuit breaker.   
     
     
         3 . The method according to  claim 1 , wherein the circuit breaker comprises a three-phase switch, each phase being assigned to a switching contact. 
     
     
         4 . The method according to  claim 1 , wherein the method is simultaneously carried out for a plurality of switching contacts of the circuit breaker. 
     
     
         5 . The method according to  claim 1 , wherein the circuit breaker comprises one of an ultra-high voltage switch, a high voltage switch, and a medium voltage switch. 
     
     
         6 . An apparatus for the measurement of a resistance of a switching contact of an electrical circuit breaker, comprising:
 a control unit for controlling the electrical circuit breaker to selectively open or close the switching contact of the circuit breaker; and   a resistance measurement device which is configured to be coupled to the control unit and which is configured to determine a first resistance value across the circuit breaker while the circuit breaker is grounded at both sides and the switching contact is closed, determine a second resistance value across the circuit breaker while the circuit breaker is grounded at both sides and the switching contact is open, and determine the resistance of the closed switching contact on the basis of the first resistance value and the second resistance value.   
     
     
         7 . The apparatus according to  claim 6 , wherein the apparatus is configured to carry out the method according to any one of  claims 1 - 5 . 
     
     
         8 . A test environment for the measurement of a resistance of a switching contact of an electrical circuit breaker, comprising:
 the circuit breaker,   a first grounding device which is configured to be coupled with the circuit breaker for grounding a first side of the circuit breaker;   a second grounding device which is configured to be coupled with the circuit breaker for grounding a second side of the circuit breaker; and   a resistance measurement device which is configured to be coupled with the circuit breaker and which is configured to determine a first resistance value across the circuit breaker while the circuit breaker is grounded at both sides and the switching contact is closed, determine a second resistance value across the circuit breaker while the circuit breaker is grounded at both sides and the switching contact is open, and determine the resistance of the closed switching contact on the basis of the first resistance value and the second resistance value.   
     
     
         9 . The test environment according to  claim 8 , further comprising the apparatus according to  claim 6 . 
     
     
         10 . A method for the measurement of resistances of switching contacts arranged in a series connection of an electrical circuit breaker, comprising the steps:
 feeding a first measurement current in a first direction through a first switching contact of the switching contacts arranged in the series connection;   feeding a second measurement current in a second direction through a second switching contact of the switching contacts arranged in the series connection, the first direction and the second direction being opposite to one another with respect to the series connection of the switching contacts, and the first measurement current and the second measurement current being fed while the series connection is grounded at both sides; and   determining a resistance value of the first switching contact on the basis of the first measurement current while the first switching contact and the second switching contact are closed.   
     
     
         11 . The method according to  claim 10 , further comprising the step:
 determining a resistance value of the second switching contact based on the second measurement current while the first switching contact and the second switching contact are closed.   
     
     
         12 . The method according to  claim 11 , wherein the switching contacts of the circuit breaker are closed while the determining of the resistance values of the first and second switching contacts. 
     
     
         13 . The method according to  claim 11 , wherein the determining of the resistance values of the first and second switching contacts comprises:
 measuring a first voltage across the first switching contact; and   measuring a second voltage across the second switching contact.   
     
     
         14 . The method according to  claim 10 , wherein the first and second measurement currents are fed while the circuit breaker is grounded at both sides. 
     
     
         15 . The method according to  claim 10 , wherein the first measurement current and the second measurement current are adjusted such that a voltage drop across the first switching contact equals a voltage drop across the second switching contact. 
     
     
         16 . The method according to  claim 10 , wherein in the series connection the first switching contact is arranged adjacent to the second switching contact. 
     
     
         17 . The method according to  claim 10 , wherein the circuit breaker comprises a plurality of pairs of switching contacts, each of the pairs of switching contacts comprising a first switching contact and an adjacent second switching contact, and wherein the method is simultaneously carried out on several of the pairs of adjacent switching contacts of the circuit breaker. 
     
     
         18 . The method according to  claim 10 , wherein the circuit breaker comprises one of an ultra-high voltage switch, a high voltage switch, and a medium voltage switch. 
     
     
         19 . An apparatus for the measurement of resistances of switching contacts arranged in a series connection of an electrical circuit breaker, comprising:
 a first device for feeding a first measurement current in a first direction through a first switching contact of the switching contacts arranged in the series connection;   a second device for feeding a second measurement current in a second direction through a second switching contact of the switching contacts arranged in the series connection, the first direction and the second direction being opposite to one another with respect to the series connection of the switching contacts, and the first measurement current and the second measurement current being fed while the series connection is grounded at both sides; and   a processing unit which is coupled to the first device and the second device and which is configured to determine a resistance value of the first switching contact on the basis of the first measurement current while the first switching contact and the second switching contact are closed.   
     
     
         20 . The apparatus according to  claim 19 , wherein a first switch is connected in parallel with the first switching contact and a second switch is connected in parallel with the second switching contact. 
     
     
         21 . The apparatus according to  claim 19 , wherein a first grounding device is connected with the first switching contact and a second grounding device is connected with the second switching contact. 
     
     
         22 . The apparatus according to  claim 21 , wherein a third grounding device is connected with a point between the first switching contact and the second switching contact. 
     
     
         23 . The apparatus according to  claim 19 , wherein the apparatus is configured to carry out a method comprising the steps of:
 feeding the first measurement current in the first direction through the first switching contact of the switching contacts arranged in the series connection;   feeding the second measurement current in the second direction through the second switching contact of the switching contacts arranged in the series connection, the first direction and the second direction being opposite to one another with respect to the series connection of the switching contacts, and the first measurement current and the second measurement current being fed while the series connection is grounded at both sides; and   determining the resistance value of the first switching contact on the basis of the first measurement current while the first switching contact and the second switching contact are closed.