Arc flash detection apparatus and electrical system including the same

Abstract

An electrical system includes first, second and third busses; a first interrupter electrically connected between the first and second busses; at least one of a shorting apparatus operatively associated with the first or second bus, and the first interrupter comprising a trip coil; a current sensor to sense a fault current flowing in the first bus and responsively output a first signal; a number of light sensors to sense an arc flash operatively associated with a number of the first, second or third busses and responsively output a second signal; a second interrupter electrically connected between the second and third power busses and output a third signal; and a circuit to invert the third signal to provide a fourth signal, and to operate the at least one of the shorting apparatus and the trip coil responsive to an AND of the first, second and fourth signals.

What is claimed is: 
     
         1 . A method of selectively operating or not operating a shorting device in an electrical system, the method comprising:
 receiving at least one of: a first logical signal indicative of an arcing event in or related to the electrical system or a second logical signal indicative of operation of a circuit interrupter from a closed position toward an open position; and   selectively operating or not operating the shorting device dependent on at least one of the first or second logical signals.   
     
     
         2 . The method of  claim 1 , wherein the shorting device is operated if the first logical signal is received without having first received the second logical signal. 
     
     
         3 . The method of  claim 1 , wherein the shorting device is not operated if the second logical signal is received before the first logical signal. 
     
     
         4 . The method of  claim 1 , further comprising:
 receiving a third logical signal indicative of the presence of a fault current of at least a predetermined magnitude flowing in a power bus of the electrical system, wherein the step of selectively operating or not operating the shorting device is dependent further on the third logical signal.   
     
     
         5 . The method of  claim 4 , wherein the shorting device is operated if, after receiving the first logical signal, the second logical signal is received without having first received the third logical signal. 
     
     
         6 . The method of  claim 1 , wherein the electrical system includes a number of light sensors and wherein the first logical signal originates from the number of light sensors. 
     
     
         7 . The method of  claim 1 , wherein the electrical system includes an upstream protective device, wherein the step of selectively operating or not operating the shorting device includes selectively operating or not operating the upstream protective device dependent on at least one of the first and second logical signals. 
     
     
         8 . A circuit for use in an electrical system having at least one of a shorting device or a first circuit interrupter and having a second circuit interrupter, the circuit being configured to at least:
 receive a logical signal indicative of an arcing event related to the electrical system;   receive another logical signal indicative of operation of the second circuit interrupter; and   selectively operate or not operate the at least one of a shorting device or a first circuit interrupter dependent on at least one of the logical signals.   
     
     
         9 . The circuit of  claim 8 , wherein the circuit is configured to operate the at least one of a shorting device or the first circuit interrupter if the circuit receives the logical signal indicative of an arcing event without having first received the logical signal indicative of operation of the second circuit interrupter. 
     
     
         10 . The circuit of  claim 8 , wherein the circuit is configured to not operate the at least one of a shorting device or a first circuit interrupter if the circuit receives the logical signal indicative of operation of the second circuit interrupter before receiving the logical signal indicative of an arcing event. 
     
     
         11 . The circuit of  claim 8 , wherein the circuit is further structured to receive a logical signal indicative of the presence of a fault current in a power bus of the electrical system, and wherein the circuit is further configured to selectively operate or not operate the at least one of a shorting device or a first circuit interrupter dependent further on the logical signal indicative of the presence of a fault current. 
     
     
         12 . The circuit of  claim 11 , wherein the logical signal indicative of a fault current comprises a first logical signal, wherein the logical signal indicative of an arcing event comprises a second logical signal, wherein the logical signal indicative of operation of the second circuit interrupter comprises a third logical signal, wherein the circuit is configured to operate the at least one of a shorting device or a first circuit interrupter if, after the circuit receives the first logical signal, the circuit receives the second logical signal without having first received the third logical signal. 
     
     
         13 . The circuit of  claim 12 , wherein the circuit is configured to not operate the at least one of a shorting device or a first circuit interrupter if, after the circuit receives the first logical signal, the circuit receives the third logical signal before receiving the second logical signal. 
     
     
         14 . An electrical system comprising:
 a circuit as recited in  claim 8 ;   a first power bus;   a second power bus;   at least one of: the shorting device operatively associated with the first power bus or second power bus, or the first circuit interrupter associated with the first power bus or the second power bus;   a number of light sensors structured to sense an arc flash associated with the electrical system and responsively output the logical signal indicative of an arcing event related to the electrical system to the circuit; and   a second circuit interrupter electrically connected between the first power bus and the second power bus, the second circuit interrupter being structured to move from a closed position to an open position responsive to detecting an overcurrent condition and responsively output the logical signal indicative of operation of the second circuit interrupter to the circuit.   
     
     
         15 . The electrical system of  claim 14 , wherein the circuit is configured to operate the at least one of a shorting device or a first circuit interrupter if the circuit receives the logical signal indicative of an arcing event without having first received the logical signal indicative of operation of the second circuit interrupter. 
     
     
         16 . The electrical system of  claim 14 , wherein the circuit is configured to not operate the at least one of a shorting device or the first circuit interrupter if the circuit receives the logical signal indicative of operation of the second circuit interrupter before receiving the logical signal indicative of an arcing event. 
     
     
         17 . The electrical system of  claim 14 , further comprising a current sensor structured to sense a fault current of at least a predetermined magnitude flowing in the first power bus and responsively output a logical signal indicative of the presence of the fault current to the circuit, and wherein the circuit is further configured to selectively operate or not operate the at least one of a shorting device or a first circuit interrupter dependent further on the presence of the logical signal indicative of the presence of the fault current. 
     
     
         18 . The electrical system of  claim 17 , wherein the logical signal indicative of a fault current comprises a first logical signal, wherein the logical signal indicative of an arcing event comprises a second logical signal, wherein the logical signal indicative of operation of the second circuit interrupter comprises a third logical signal, and wherein the circuit is configured to operate the at least one of a shorting device or a first circuit interrupter if, after the circuit receives the first logical signal, the circuit receives the second logical signal without having first received the third logical signal. 
     
     
         19 . The electrical system of  claim 18 , wherein the circuit is configured to not operate the at least one of a shorting device or a first circuit interrupter if, after the circuit receives the first logical signal, the circuit receives the third logical signal before receiving the second logical signal. 
     
     
         20 . The electrical system of  claim 14 , wherein the second circuit interrupter comprises one of:
 a protective relay,   an auxiliary contact, or   a trip shaft, and wherein the logical signal indicative of operation of the second circuit interrupter originates from one of:   the protective relay,   the auxiliary contact, or   a device monitoring the trip shaft.