Method for judging breaking of PT (potential transformer) in fast switch

Abstract

The invention discloses a method for judging breaking of a PT (potential transformer), which is characterized in that three criterions are set, and once any of the criterions is satisfied, the PT is judged to be broken. The three criterions are specifically as follows: when an absolute value of a voltage difference between the maximal voltage phase and the minimal voltage phase in a three-phase bus voltage is more than 30V, the PT is judged to be broken; when both the maximal voltage phase and the minimal voltage phase in the three-phase bus voltage are less than 10V, an operating or standby inlet wire switch is located at an on position while a standby or operating switch is located at an off position, if the working or standby inlet wire voltage is more than 80V, the PT is judged to be broken; when both the maximal voltage phase and the minimal voltage phase in the three-phase bus voltage are less than 10V, the operating or standby inlet wire switch is located at the on position while the standby or operating switch is located at the off position, if both inlet wires are provided with CTs (current transformers) and a working or standby inlet wire current is more than 0.05A, the PT is judged to be broken. According to the method disclosed by the invention, the position of the inlet wire switches and a bus current are considered, therefore, breaking of the PT of the bus can be judged accurately, the logic is simple and effective, and the criterions are more comprehensive and more accurate.

Description

technical field [0001] The invention relates to a fast-cut PT disconnection judgment method, which belongs to the technical field of power system protection. Background technique [0002] The backup power fast switching device is switched by comparing the relative angle of the bus voltage and the backup incoming line voltage. Accurately judging whether the busbar PT (potential transformer) is disconnected is very important for switching. At present, the judgment of PT disconnection is judged by subtracting the absolute value of the sum of the other two phases from the largest one of the three phases. If the absolute value is less than 20V, and the voltage of the largest phase of the three phases is greater than 80V, then It is judged that the PT is disconnected. [0003] The existing PT disconnection judgment method only processes the measured value of the PT on the bus, and does not fully consider the measured value of the PT at the working incoming line and the standby i...

AI Technical Summary

Problems solved by technology

[0003] The existing PT disconnection judgment method only processes the measured value of the PT on the bus, and does not fully consider the measured value of the PT at the working incoming line and the standby incoming line, the switch position of the two incoming lines, and the bus current. In some special cases, it is impossible to accurately distinguish whether it is a PT disconnection or a bus fault

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