A protection method and system for exciting winding interphase short circuit faults of an alternating current excitation synchronous motor

Abstract

The invention provides a protection method and system for exciting winding interphase short circuit faults of an alternating current excitation synchronous motor. The method comprises the steps of: firstly collecting three-phase exciting winding currents of a motor; calculating an absolute value of current instantaneous values and a current effective value according to the collected currents; during decision making for over-current protection, setting an over-current instantaneous value criterion as the main criterion and an over-current effective value criterion as an auxiliary criterion; performing accumulative counting on moments which meet the current instantaneous value out-of-limit criterion or which do not meet the current instantaneous value out-of-limit criterion but meet the current effective value out-of-limit criterion by using a time delay counter; performing progressive subtraction on moments which do not meet the current instantaneous value out-of-limit criterion and thecurrent effective value out-of-limit criterion; further determining the over-current protection start, operation and start return time according to values of the time delay counter. The method combines the rapidness of the instantaneous value criterion and the reliability of the effective value criterion and can rapidly reflect exciting winding interphase short circuit faults of an alternating current excitation synchronous motor.

Description

technical field [0001] The invention relates to a relay protection technology for the fault of the excitation winding of an AC excitation synchronous motor, in particular to a protection method and system for a phase-to-phase short circuit fault of the excitation winding of an AC excitation synchronous motor. Background technique [0002] In an AC excited synchronous motor, the voltage and current in the excitation winding are AC components with frequency changes, and the current and voltage phases are different between different phases, so phase-to-phase short-circuit faults may occur. When a phase-to-phase short circuit occurs, a relatively large current will pass through the faulty phase of the excitation winding. The large current will generate high temperature inside the unit and cause damage to the unit. Therefore, it is necessary to increase overcurrent protection for the phase-to-phase fault of the excitation winding. [0003] For traditional overcurrent protection, ...

AI Technical Summary

Problems solved by technology

For example, in pumped storage units with AC excitation, the generally required excitation frequency varies within the range of -0.1fN to 0.1fN (fN is the rated frequency), and the minimum operating frequency can reach 0.1Hz. If the traditional overcurrent protection method is adopted , the calculation of the fault component alone takes 10 seconds, which greatly reduces the reaction speed of the relay protection equipment to the short-circuit fault

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