A high-transformation-ratio ct polarity calibration method under load

Abstract

A high-transformation-ratio CT polarity verification method with load. The technical key of this method is: use the test bench to output a large current, flow in through the A-phase of the primary equipment, and pass through the A-phase of the bus-connection CT of the local substation and the CT-phase respectively. Phase A, phase A of line L, phase A of line CT of the opposite substation, phase B of the three-phase connection end of the switch in the mother ground of the substation returns, and passes through phase B of line CT of the opposite substation, phase B of line L, and the local side The B phase of the line CT and the B phase of the bus tie CT flow back to the K2 end of the test bench, so that the current forms a complete loop. By calculating the vector sum of the secondary current flowing through the bus tie CT and the LMCT of substation M, the polarity is correct; by calculating the vector sum of the secondary current flowing through the LMCT of substation M and the LNCT of substation N, the polarity is correct. The method can avoid wrong connection of the polarity of the bus differential protection in the new substation, improve the operation reliability of the bus differential protection in the substation, and ensure the stable operation of the power system.

Description

technical field [0001] The invention relates to a high transformation ratio CT polarity load verification method, belonging to the field of power system comprehensive automation equipment inspection. Background technique [0002] CT (Current Transformer) is a major equipment used in substations and transmission and distribution lines. It mainly converts the current on the primary side of the system into secondary current according to a certain ratio. Widely used in technical fields such as power system monitoring, protection, fault recording and fault location, it is an important equipment for current measurement, system control, and especially relay protection devices in power systems. Before CT is put into operation, it is generally necessary to verify its polarity, especially for bus differential protection circuits and longitudinal differential protection circuits that have high requirements for them. As the capacity of my country's power system continues to increase, t...

AI Technical Summary

Problems solved by technology

However, at the voltage level above 220kV, for the transformation ratio of 3000 / 1, it is difficult to organize the load, and it is still difficult to meet the requirements of the load calibration in reality.

If the load is small, the secondary value of CT will be very small, which cannot be distinguished from the zero drift of the protection device, which will affect the judgment of the personnel, or cause misjudgment. When the line is running later, if there is a fault, it will cause Misoperation of bus differential protection or longitudinal differential protection will expand the scope of power outages and bring great unsafe hidden dangers to the safety of the power grid

In addition, changing the operation mode of multiple substations will cause a lot of waste of manpower and material resources, and there are many dangerous points in the switching process, causing unnecessary safety hazards

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