Research On Monitoring Terminal Of Current Transformer

The electromagnetic current transformer as a power system for the primary side current system of transmission components, is widely used for on a measured the flow of electric current measurement and relay protection device, its main function is the high current through the primary winding of the power system by the principle of electromagnetic induction into small current of the secondary winding loop, provided to the measurement instrument or the relay protection devices of relay to reflect the normal operation of the power system state information or reflect power system fault conditions. With the construction of digital substation, electronic current transformers appear gradually, but it is only part of the application, electromagnetic current transformers are still in the power system in a large number of use. Electromagnetic current transformer whether the normal operation of the system parameters and the failure of relay protection action or not have a very big impact, so the need to monitor the operation of electromagnetic current transformer. Factors affecting the normal work of the electromagnetic current transformers including core reminisce, saturation of magnetic circuit, open circuit secondary circuit, secondary cable wear and reverse polarity, we developed a can of current transformer monitoring terminal, to achieve the operation state of the current transformer monitoring, timely understanding of the current transformer may appear abnormal situation.The main work of this paper includes the current transformer monitoring system in the algorithm and logic method, as well as the design of the hardware and software of the monitoring terminal. Which by the algorithm and logic discrimination method is designed and realized on the sensor monitoring, including on the secondary circuit disconnection fault, current transformer saturation discriminant analysis, current transformer secondary cable wear discriminant, calculated reminisce, current transformer and cable polarity discrimination. The development of the hardware part includes the design of the communication board, CPU board, HMI and so on. Software development is mainly the monitoring algorithm and logic method into computer language, which distinguish the polarity two times wiring of current transformer is mainly used for debugging of new substation, depending on the symmetry and the differential current transformer of each side of the current size of the discriminant; current transformer saturation before 5ms linear transfer time travel, fast calculation of flow and braking current using short data window algorithm for identification of current transformer saturation; using cable wear, discrimination difference three-phase current transformer two current phase angle and amplitude; through the solution of the differential equation calculated two current transformer is near zero, The core flux current transformer in value.