Abb Power Td & Company

Westinghouse Electric Corporation

James P Garitty

Shan C Sun

Redjem Bouhenguel

Thomas M Yocom

John S Wargo

A system and method for automatically testing the operation of a protective relay system is disclosed. The system and method provide for continuous testing to ensure proper operation of the protective relay system while the relay remains in service and without interrupting the normal operation of the relay. This testing is performed by storing reference data corresponding to test signals, generating test signals, sampling a specific test signal, processing that test signal through the relay and comparing the processed test signal with the corresponding reference data. Upon detection of an error in the relay, the system and method further provide for isolation of the relay from the electric power system and automatic testing of individual electrical components within the protective relay system to determine the identity of the malfunctioning component. The method of determining the malfunctioning component requires: selecting a component for testing, generating a test signal, providing the test signal as an input to the selected component, processing the test signal through the selected component and the subsequent component in the protective relay system and comparing the processed test signal with corresponding reference data. Finally, the system and method further provide for automatic correction of the malfunctioning component, if possible.

Methods and systems for automatic testing of a relay

Events at spaced locations, such as contact activity in the protective relays of an electric power distribution network, are time stamped using a single remote clock by a system which includes one or more slave stations monitoring the events. Each slave station initiates a count of locally generated clocking pulses of fixed duration upon detection of the first event monitored by it. Identification of the first event is stored in a first slot in memory. Additional memory slots each store the identification of a subsequent event and the count at the occurrence of that subsequent event. Upon command from a remote master station, the current count is stored in the first slot and the contents of the first slot and of the additional slots are transmitted over a communications network to the master station. The master station calculates the absolute time of each event using its master clock, the transmitted counts, the fixed duration of the clocking pulses, and the transmission time required to transmit the data from the particular slave station to the master station. The master station then sends a clear command to reset the count and clear the memory slots. If the number of events detected by a slave station before a clear command is received exceeds the number of memory slots available, the information on the first event stored in the first slot is retained, and the additional slots retain data on as many of the most recent events as there are additional slots.

System for time stamping events using a remote master clock

Monitoring and control of analog electromechanical protective relays and digital mcroprocessor based relays is integrated through a system including slave stations which record and time tag contact activity at each of the analog relays. The slave stations continuously retain digital samples of a predetermined number of the most recent cycles of the currents and voltages at the analog relays and when a trip occurs store the retained samples as pre-fault values together with a preset number of post-fault samples. A master station communicates with the slave stations monitoring the analog relays and with the digital relays through a two way communications network. The master station repetitively polls the slave stations and digital relays for contact activity. Detailed data such as the time tags and pre-fault and post-fault currents and voltages are then requested from those stations reporting contact activity. Either the slave stations or master station calculate fault location and type from the fault voltages and currents, an periodically calculate routine metering parameter such as watts and VARs.

Electric power system with remote monitoring and control of protective

Apparatus for performing selective-pole trip determination is included in each protective relay of a current only monitoring protective relay system for protecting an electrical transmission segment of a power system network against faults. Current signals from the phases of the transmission segment are provided to a sequence network of the apparatus for conversion into positive and negative sequence component signals for each phase. A zero sequence component signal is also derived. A logic circuit is provided for each of the phases of the transmission segment and is governed by the corresponding sequence component signals and phase shifted variations thereof to detect a single-pole fault exclusively in the corresponding phase and generate a signal in response to the detection. An internal trip detection enables each phase logic circuit to generate its corresponding trip signal. Each protective relay further includes multi-phase trip logic circuitry governed by the positive, negative and zero sequence component signals and phase shifted variations thereof to generate phase-to-phase and phase-to-phase-to-ground fault signals.

Protective relay system for performing selective-pole trip determination

A new protective relay for determining the occurrence of a single-phase-to-ground fault and tripping the appropriate circuit breaker. At local and remote terminals of a protected line segment, three signals representative of an electrical parameter on each phase conductor are input to a local and remote protective relay. In both the local and remote protective relays, the three electrical parameter signals are manipulated to produce two evaluation signals. The two local evaluation signals produced in the local protective relay are transmitted to the remote protective relay, and the two remote evaluation signals produced in the remote protective relay are transmitted to the local protective relay. In the local protective relay the two local evaluation signals are manipulated to produce a third local evaluation signal, and the two remote evaluation signals are manipulated to produce a third remote evaluation signal. The six evaluation signals are vectorially-compared to determine on which phase the fault has occurred. Only the circuit interrupter associated with the faulted phase conductor is tripped. If a fault involves two or more phase conductors, all three circuit interrupters are tripped. Similar signal processing occurs in the remote protective relay.

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Coral Springs, FL, United States of America

James P Garitty