Gould Inc.

Brown Boveri Electric Inc.

James P DeLacy

Robert H Lechner

A reclosing system for d-c feeder circuit breakers used on transit systems is disclosed. Circuit breaker closure is prevented when the feeder circuit voltage is in a predetermined voltage range and when the feeder circuit impedance is less than a given value, which is less than the impedance which would be presented by a parked train in a deenergized portion of the transit rails. A Wheatstone bridge is inserted into the circuit during the load impedance measurement. The Wheatstone bridge circuit is compensated for positive or negative rail return voltage. The automatic reclosing scheme is locked out after two closures of the circuit breaker followed by automatic tripping within six minutes, or by twelve load impedance measurements, which are performed within three minutes and which all fail to lead to a circuit breaker closure.

Voltage sensing and load measuring automatic reclosing system for d-c

A reclosing system for d-c feeder breakers in transit systems employing cars using a chopper type of regulated power is disclosed. The circuit includes voltage-sensing and load-measuring circuits which determine that there is no short circuit on the respective feeder line before the circuit breaker can be closed. The system operates in two sequential modes. The first is a voltage-sensing mode which, upon sensing a voltage on the feeder circuit greater than some given magnitude, will cause the closing of the feeder breaker. If this voltage is not sensed during the voltage-sensing mode, the circuit automatically goes into a load-measuring mode wherein a current is injected into the feeder circuit and the voltage drop caused by the injected current is monitored. If a sufficiently high voltage is produced, which indicates that the feeder circuit is free of a fault, the feeder breaker is closed.

Voltage sensing and load measuring automatic reclosing system for D-C

A transfer trip circuit has a first station which contains a circuit breaker and a source of control current in which the control current is increased from a first value to a second value in response to the operation of the circuit breaker. A second station is connected to the first station by a pair of pilot wires which carry the control current. The second station contains a circuit breaker which is to be operated in response to the operation of the circuit breaker in the first station, and also contains two relay coils which carry the control current produced in the first station. The first relay coil operates an annunciator when the control current is below its first value to indicate a fault in the pilot wires. The second relay coil operates the trip circuit of the circuit breaker in the second station when the control current in said pilot wires is increased to said second value.

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Havertown, PA, United States of America

James P DeLacy