Low fault current isolator system

摘要

A low fault current isolation arrangement senses a loss of voltage and automatically isolates and de-energizes a down live primary wire if overcurrent protection devices have not cleared the high impedance fault in an electric power distribution network. Incorporating an operator selectable time delay response, the low fault current isolation arrangement permits overcurrent protection devices to attempt to detect and shut down the affected conductor, and then isolates and shuts down the low current fault if the overcurrent devices are not successful. The isolation arrangement continuously monitors AC voltage as remotely provided by smart meters even after a fault location is de-energized, and serves as a back up, and not as a replacement, for existing overcurrent protection schemes. A host computer operates in conjunction with plural smart meters each coupled to an associated customer distribution transformer in conjunction with the fault isolator to detect and shut down high impedance faults.

主权项

1. For use in an electric power distribution network having an overcurrent protection arrangement and including a main feeder line and a branch tap coupled to said main feeder line, and having plural distribution transformers each coupled to a respective customer for providing electric power to the customers, a system for detecting and isolating a low current high impedance fault in said branch tap comprising:
a two-way communications network including a cell tower for receiving and transmitting two-way RF communications signals; plural smart meters each coupled to a source side and to a load side of a respective distribution transformer for monitoring the voltage across the distribution transformer, and including a father smart meter in direct two-way communication with each of the remaining smart meters in said at least one branch tap; a server/sorter in communication with said cell tower for processing and routing the two-way RF communications signals; a host computer in communication with said server/sorter for receiving and processing communications from said father smart meter representing the voltage across each of said distribution transformers; and a fault isolator disposed in the branch tap between the main feeder line and said distribution transformers and in communication with said host computer, wherein said fault isolator is responsive to a shut down signal received from said host computer when a secondary voltage across at least one of said distribution transformers meets a predetermined voltage level and the secondary voltage across at least one of said distribution transformers is less than a predetermined voltage level indicating a low current high impedance fault whereupon said host computer provides a trip signal to said fault isolator for isolating the high impedance, low current fault without shutting down unaffected portions of the electric power distribution network.