Design Of An Intelligent Integration Testing System For Ring Main Unit

With the improvement of intelligent level of the electrical power system, ring main unit has been widely used in power distribution system. In order to ensure the stability of power system operation, the requirement for the safety and reliability of ring main unit is continuously rising, so strict delivery test should be done by the manufacturers. At present, the test methods adopted by the relevant manufacturers are as follows:testing step-by-step by separate power supplies, reading and recording the results manually, which is fussy. To improve the quality and efficiency of ring main unit delivery test, an intelligent integration testing system was designed according to the test function and production practice.The testing system integrates the traditional measuring equipment into test stand based on the data communication. Considering the system requirements, the selection and configuration of the equipment are performed. The variable operating voltage for ring main unit was generated by voltage regulator. The current of phase-to-phase protection function testing was supplied by voltage regulator and current transformer. Program-controlled AC current source was used for the test of the zero-sequence current protection function. Switching the test phase was achieved via three contactors. The circuit of monitor and control is consist of data acquisition card AC6621and signal conditioning circuit, which can realize the modulation of the output voltage, control the operations of the contactors and measure voltage and current signals.A visual operating interface was designed with Visual Basic6.0. Through the flexible use of VB controls, such as MSFlexGrid, WinSock and MSComm, the functions of user interface, data management, data collection, data communication and control were realized. The protocol101and protocol104are followed by the communication between computer and the intelligent monitor terminals of ring main unit, which can transmit and receive the "three remote" messages simultaneously during the testing process. The testing system can control the test process and record the testing results automatically, and it can analyze the results, generates a test report at last.The designed system can perform intelligent test on "three remote" function, phase-to-phase protection function, zero-sequence protection function, and instantaneous trip protection function of ring main unit. A large number of experiments indicate that the test system can operate normally. Compared with traditional test method, it has the advantages of less failure rate, convenient usage, high detection accuracy and simple human-machine interface, which can meet the design specifications and requirements. The system has been put into actual use and works well currently.