Abb Power Td & Company

Thomas M Yocom

James P Garitty

A system and method for controlling time-critical functions by dynamically adjusting the interrupt frequency of a microprocessor. Interrupts are generated at a predetermined frequency. Time-critical functions are then performed in response to the interrupts. The interval is adjusted based on timing data from a substantially accurate source. Where the interval is measured in terms of clock pulses, a non-integer number of pulses per interval is attained by varying the number of pulses per interval so that the average over a number of intervals is equal to the non-integer number of pulses per interval. The interval is further adjusted using a selected damping coefficient to eliminate an underdamped condition.

Real-life timer interval adjustment

A microcomputer repetitively samples a signal representative of the instantaneous state of an electrical contact and initiates a count in response to the first sample which indicates a contact state different from a stored status of the contact. The microprocessor counts up for samples indicating an active state of the contact and down for inactive samples. If the count increases to a predetermined count representing a certain net count of active samples when the stored status is inactive, the stored status is changed to active. Similarly, the stored status is changed from active to inactive if the count decreases to a predetermined count representing a certain net count of inactive samples. The time of the first sample which indicates a contact state different from the stored status of the contact is stored as a temporary time. If the stored contact status is changed, the stored temporary time is saved as the valid time of the change in status. The microcomputer maintains lists of contacts having an active status and those having an inactive status and keeps track of a separate sample count for each contact monitored.

System for monitoring electrical contact activity

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.

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N. Lauderdale, FL, United States of America

Thomas M Yocom