On-load calibration method for polarity of high-transformation-ratio current transformer (CT)

Abstract

An on-load calibration method for the polarity of a high-transformation-ratio current transformer (CT) is technically characterized in that a test bed outputs large currents, the currents flow into a transformer substation through the A phase of primary equipment, return through the A phase of a bus tie CT of the transformer substation on the side, the A phase of the CT, the A phase of a circuit L, the A phase of a circuit CT of a transformer substation on the opposite side and the B phase of the three-phase connection end of a mother grounding disconnecting link of the transformer station, and flow back to the K2 end of the test bed through the B phase of the circuit CT of the transformer substation on the opposite side, the B phase of the circuit L, the B phase of the circuit CT on the side and the B phase of the bus tie CT, and therefore the currents form a complete loop. The correctness of the polarity is judged by calculating the sum of secondary current vectors of the bus tie CT and the LMCT of an M transformer station and calculating the sum of secondary current vectors of the LMCT of the M transformer station and the LNCT of an N transformer station. According to the method, wrong connection of the busbar differential protection polarity of a newly-built transformer station can be avoided, the reliably of busbar differential protection operation in the transformer station can be improved, and stable operation of an electric system can be guaranteed.

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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