Abstract: A zone selective interlock module is interposed between a pair of upstream and downstream static trip circuit breakers for controlling the short-time and ground fault zone selective interlock functions of the breakers. When a signal is received from a downstream static trip breaker, the module transmits a low-level interlock signal to a static trip breaker upstream. The interlock signal, in turn, activates the programmer circuit of the upstream breaker causing a shift in the upstream programmer time delay characteristics. The module also provides an energy storage feature to ensure the integrity of the interlock function in the event that the control power is lost upon the occurrence of a fault.

Abstract: In a relay tester, analog signals to be supplied to a relay under test are processed with digital circuits so that the concerned frequency, phase, voltage and current are set and adjusted with high frequency.

Abstract: In a method of and apparatus for synthetic testing of a multi-break circuit breaker having a metallic tank and a series connection of interrupter units, and a non-grounded and a grounded lead conductors connected to the first and the second ends of the series connection, a short-circuit current is made to flow through the series connection, the circuit breaker is then operated, and upon completion of the interruption of the current, a first transient recovery voltage is supplied to the non-grounded lead conductor and is applied, in effect, across a first one of the interrupter units at the second end or across a train of interrupter units including said first one of the interrupter unit, and, simultaneously, a second transient recovery voltage is supplied to the tank, the first and the second transient recovery voltages having the same polarity and the second transient recovery voltage having substantially the same magnitude as the whole transient recovery voltage to be applied across all the interrupter unit

Abstract: Abnormal conditions of a tank type gas circuit breaker are detected by driving a movable contact with a drive force and at a speed respectively lower than normal drive force and speed. Measuring units are mounted on various portions of a casing of the circuit breaker without disassembling the same and measured data are displayed for comparison.

Abstract: A circuit interrupter includes a microprocessor based trip unit having a plurality of output control lines and a power supply for providing operating power to said trip unit. Interlock means are provided to maintain the output control lines in a predetermined inactive status for a predetermined time period following energization of the power supply to allow time for operating power to rise to a level sufficient to enable the microcomputer to assert positive control over the status of the control lines. An automatic reset circuit is provided to reset the microcomputer program counter to an initialization routine unless a pulse pattern produced by proper execution of the microcomputer instructions is received by the automatic reset circuitry.

Abstract: In a metal-clad, compressed gas-insulated high-voltage switching installation, installation parts can be cut off by a circuitbreaker and connected to the grounded casing by means of a grounding switch, insulated measuring electrodes connectable to the testing terminal of a capacitive voltage divider and to a display device being provided in the casing adjacent to the grounding switch, for observation of the conductor voltage.To obtain a simple test setup in a three-phase clad installation, two pin-type measuring electrodes are arranged respectively centrally between pairs of the three conductors in such a way that their rounded end protrudes into the interior of the casing.

Abstract: A circuit interrupter includes a microcomputer-based trip unit, and a display and control panel comprising a numeric display device and a plurality of legends associated with light-emitting diodes. The trip unit presents a sequential display of numeric values of associated circuit electrical parameters and time-current trip characteristic setting values, with the currently visible numeric quantity being identified by an energized light emitting diode and associated legend. The control panel also includes a test switch for initiating a test operation and a potentiometer for selecting a desired simulated fault current value for the test operation. The test capability is provided simultaneously with normal circuit breaker operation which maintains full protection of the associated circuit. A short-delay feature is provided having a selectable i.sup.2 t characteristic with adjustment of both pick-up and time parameters.

Abstract: A test circuit for testing the circuit making or circuit breaking capability of a high voltage apparatus includes a high current source in a high current circuit and a high voltage source in a high voltage circuit. The apparatus to be tested is disposed in the high voltage circuit, and a switch with an explosive actuator is provided in the high current circuit to connect the apparatus thereto during testing. The explosive actuator is connected with a voltage source in the high voltage circuit for ignition thereof by the preignition of the tested apparatus.

Abstract: A test set designed to energize an oil filled circuit recloser with a reasonably constant current to simulate fault conditions for the purpose of verifying the recloser operation as specified by manufacturer's performance curves is disclosed. The test set of this invention is a self-contained unit comprising a selectable tapped auto-transformer, a variable vernier auto-transformer, a selectable power resistance bank, an output transformer, a control package and a monitor package.

Abstract: A portable calibrator for d.c. circuit breakers is provided which produces a low voltage, short duration current test pulse of a current level sufficient to trip the breaker under test. The current pulse is produced by a high power, high frequency d.c. to d.c. converter which is controlled by lower power signals. A static switch controlled by the converter output provides current protection for the converter. A feedback loop including a current transformer connected in an output transformer circuit provides control of the test pulse. A non-inductive shunt connected in a negative test lead monitors the test pulse during the period of application thereof, the shunt being connected to a sample and hold read-out circuit which includes metering for indicating the peak current value. A timer interlocked with the metering ensures that sufficient time is provided for the operator to read current value.