Schweitzer Engineering Laboratories, Inc.

Schweitzer Engineering Labs, Inc.

Hector J Altuve-Ferrer

Armando Guzman-Casillas

Jeffrey B Roberts

Gabriel Benmouyal

Daqing Hou

Stanley E Zocholl

Demetrios A Tziouvaras

Ralph W Folkers

An apparatus and method provide protection for a synchronous generator in a power system. The method includes deriving a plurality of generator safe operating boundary data expressions from power system data and/or user-defined inputs. The power system data may include a plurality of generator data supplied by a manufacturer of the generator and/or power system parameters such as power system equivalent impedance. Each generator safe operating boundary data expression may relate to a generator capability curve, a steady-state stability limit curve, a minimum excitation limiter curve, an over excitation limiter curve, or an user-defined curve. The method also includes calculating an active power value sum and a reactive power value sum based on generator three-phase currents and voltages, comparing these sums to at least one of the plurality of generator safe operating boundary data expressions, and to provide protection and/or alarming functions for the generator based on this comparison.

Apparatus and method for providing protection for a synchronous electrical generator in a power system

A system for detecting ground faults in a compensated electric power distribution network includes the determination of zero sequence voltage (V ) and zero sequence current (I ) on a power line and calculating the zero sequence conductance (G ) therefrom. The operation of the conductance calculation circuit occurs only under selected power line conditions involving minimum values of zero sequence voltage, zero sequence current and positive sequence voltage, to ensure the accuracy of a fault direction determination. The conductance values are processed on an adaptive basis in which the difference between the most recent conductance value and a conductance value from a selected previous point in time is determined and then compared against threshold values to make forward and reverse fault declarations.

Sensitive ground fault detection system for use in compensated electric power distribution networks

In a power line current differential protection system, all three phase current values (I , I and I ) are obtained from both the local end and the remote end of a power transmission line. The magnitude of the ratio of the remote current values to the local current values are calculated. Also, the angle difference between the local and the remote current values for each phase are calculated. Comparison elements then compare the ratio and angle values against preselected values which establish a restrain region in the current ratio plane. Current values which result in the ratio being within the region do not result in a tripping signal for the circuit breaker on the power transmission line, while current values which result in a ratio outside of the region result in a tripping of the circuit breaker. Similar circuitry is used for negative sequence current quantities, with the negative sequence preselected values being set substantially lower to produce a more sensitive response to possible faults in the line.

Line differential protection system for a power transmission line

Current transformer (CT) secondary currents for the windings of a power transformer are used to produce a differential current. An operating current value is obtained from the differential current value. A restraining current value is obtained from processed winding current values. Second and fourth harmonic values of the differential current are obtained and are summed with a restraining current quantity which is a result of the restraining current multiplied by a slope characteristic factor. If the operating current value is greater than the sum of the restraining current quantity and the second and fourth harmonic values, an output signal is produced which may be used as a trip signal unless it is blocked by selected blocking signals generated by another portion of the system.

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Monterrey, Mexico

Hector J Altuve-Ferrer