Fault detection method and apparatus

A method of detecting first and second types of operation of an upstream protective device in an electrical circuit comprising:

• detecting the occurrence of a predetermined overcurrent condition and an end of the predetermined overcurrent condition;
• determining after the end of the predetermined overcurrent condition a loss of a predetermined circuit parameter for a first predetermined time duration to establish the first type of operation of the protective device;
• and
• thereafter continuing to monitor a continued loss of the predetermined circuit parameter for a second predetermined time duration to establish the second type of operation of the protective device, the predetermined overcurrent condition comprising the occurrence of an overcurrent level greater than a predetermined level for a third predetermined time duration.

A method for detecting downstream protective device operation in an electrical circuit via the circuit conditions at a particular location of the circuit comprising

• detecting a first predetermined overcurrent condition;
• detecting a second condition including a loss of voltage and/or current after an end of said first predetermined overcurrent condition;
• detecting in response to said second condition a third predetermined overcurrent condition;
• and
• detecting after the end of said third predetermined overcurrent condition an presence of a predetermined voltage condition.

An arrangement for detecting upstream protective device operations in an electrical circuit via the circuit conditions at a particular location of the circuit comprising:

• decision means responsive to predetermined circuit conditions at the particular location for providing at least first and second representations corresponding to a detection of respective first and second different types of operations of upstream protective devices, said first representation corresponding to a fault downstream of the particular location that causes operation of an upstream protective device that temporarily opens the circuit for a time interval that exceeds a first time duration, said second representation corresponding to a fault downstream of the particular location that causes operation of an upstream protective device that opens the circuit for a time interval that exceeds a second time duration greater than said first time duration, said decision means comprising first means for determining an occurrence of said first type of operation based on an occurrence of a predetermined overcurrent condition followed by a loss of a predetermined circuit parameter for said first time duration, said decision means further comprising second means for determining an occurrence of said second type of operation on the basis of a predetermined overcurrent condition followed by a loss of a predetermined circuit parameter for said second time duration, said decision means further comprising third means responsive to a return of said predetermined circuit parameter during the timing of either said first or second time duration for a third predetermined time duration for returning said decision means to a predetermined initial monitoring state, said third predetermined time duration being different for the return of said predetermined circuit parameter during each of said first and second time durations.

An arrangement for detecting upstream protective device operations in an electrical circuit via the circuit condition at a particular location of the circuit comprising:

• decision means responsive to predetermined circuit conditions at the particular location for providing at least first and second representations corresponding to a detection of respective first and second different types of operations of upstream protective devices, said first representation corresponding to a fault downstream of the particular location that causes operation of an upstream protective device that temporarily opens the circuit for a time interval that exceeds a first time duration, said second representation corresponding to a fault downstream of the particular location that causes operation of an upstream protective device that opens the circuit for a time interval that exceeds a second time duration greater than said first time duration, said decision means comprising first means for determining an occurrence of said first type of operation based on an occurrence of a predetermined overcurrent condition followed by a loss of a predetermined circuit parameter for said first time duration, said decision means further comprising second means for determining an occurrence of said second type of operation on the basis of a predetermined overcurrent condition followed by a loss of a predetermined circuit parameter for said second time duration, the electrical circuit further including a plurality of phases, said decision means comprising means responsive to each phase for individually providing said first and second representations, the electrical circuit further including a neutral, said decision means comprising means responsive to the neutral for providing said first and second representations.

A method of detecting first and second types of operation of an upstream protective device in an electrical circuit comprising:

• detecting the occurrence of a predetermined overcurrent condition and an end of the predetermined overcurrent condition;
• determining after the end of the predetermined overcurrent condition a loss of a predetermined circuit parameter for a first predetermined time duration to establish the first type of operation of the protective device;
• thereafter continuing to monitor a continued loss of the predetermined circuit parameter for a second predetermined time duration to establish the second type of operation of the protective device;
• and
• providing second data when said second type of operation has been established, and providing first data when said first type of operation has been established provided that said second type of operation has not been established.

A method of detecting first and second types of operation of an upstream protective device in an electrical circuit comprising:

• detecting the occurrence of a predetermined overcurrent condition and an end of the predetermined overcurrent condition;
• determining after the end of the predetermined overcurrent condition a loss of a predetermined circuit parameter for a first predetermined time duration to establish the first type of operation of the protective device;
• thereafter continuing to monitor a continued loss of the predetermined circuit parameter for a second predetermined time duration to establish the second type of operation of the protective device;
• and
• thereafter detecting a predetermined overcurrent for a third predetermined time duration and a presence of voltage after an end of the predetermined overcurrent to establish a downstream device operation.

A method of detecting first and second types of operation of an upstream protective device in an electrical circuit comprising:

• detecting the occurrence of a predetermined overcurrent condition and an end of the predetermined overcurrent condition;
• determining after the end of the predetermined overcurrent condition a loss of a predetermined circuit parameter for a first predetermined time duration to establish the first type of operation of the protective device;
• and
• thereafter continuing to monitor a continued loss of the predetermined circuit parameter for a second predetermined time duration to establish the second type of operation of the protective device, said first type of operation being a temporary opening of the circuit by a protective device and said second type of operation being a permanent opening of the circuit.

A method of detecting first and second types of operation of an upstream protective device in an electrical circuit comprising:

• detecting the occurrence of a predetermined overcurrent condition and an end of the predetermined overcurrent condition;
• determining after the end of the predetermined overcurrent condition a loss of a predetermined circuit parameter for a first predetermined time duration to establish the first type of operation of the protective device;
• and
• thereafter continuing to monitor a continued loss of the predetermined circuit parameter for a second predetermined time duration to establish the second type of operation of the protective device, said second predetermined time duration being greater than the maximum temporary open time of an upstream protective device.

A method of detecting first and second types of operation of an upstream protective device in an electrical circuit comprising:

• detecting the occurrence of a predetermined overcurrent condition and an end of the predetermined overcurrent condition;
• determining in response to the detecting of the end of the predetermined overcurrent condition a continuous absence of a predetermined circuit parameter throughout a first predetermined time duration to establish the first type of operation of the protective device;
• and
• thereafter continuing to monitor a continued absence of the predetermined circuit parameter throughout a second predetermined time duration to establish the second type of operation of the protective device.