BUS FAULT PROTECTION UNIT FOR AN ELECTRICAL POWER SYSTEM

摘要

22 In a three phase bus protection unit for monitoring fault conditions of an electrical power bus and actuating breakers to disconnect the associated power supply and feeder lines from the bus, there is provided for each line a current sensor responsive to the three phase currents passing through the respective breake r and the unit includes a plurality of current input terminals and a voltage input terminal for receiving the voltage output of a voltage sensor on the bus. A processor element in the unit generates digital data indicative of the instantaneous values of th e voltage and of the currents and effects pre-determined algorithmic calculations on t he digital values of the voltage and the currents to determine a presence of a fault condition in the current through any one of the breakers. In addition a processor element acts to sum the digital values of the currents to determine that sum of currents flowing into the bus and the sum of currents flowing. In the event that the sum differs from zero, a trip output generator trips all the circuit breakers associated with bus a nd records data relating to said current values. The unit is arranged such that it can be configured in a first configuration in which each of the three phases of eac h of up to six of the current sensors is connectedto the respective current terminals and the three phases are summed independently and a second configuration in which on ly one of the phases from each up to eighteen of the current sensors is connect ed to the respective current terminals and said only one of the phases is summed.< /SDOAB>