Design Of GIS Operating Mechanism Motor Protection Unit

The operating mechanism stored energy motor of GIS switch is one of the keyequipments of the intelligence high voltage switch. Because of the protection unit working inenvironment with strong electromagnetic interference, the problem of electromagneticinterference must be processed, thus the unit can operate safely and reliably. The solutions forthe GIS operating mechanism stored energy motor protection unit is designed and put intopractice. The new ideas and methods which have some theoretical significance and importantpractical value are put forward in the paper about how the protection unit operating stably andreliably in complex environment of electromagnetic interference.At beginning of this paper, the measures of anti-interference based on the analysis ofsystem interference are proposed from the hardware and software. LPC2138is selected asCPU of the protection unit, the hardware schematic design and the drawing of PCB flowchart are completed, and the software design of motor protection device is completed basedon μC/OS-II embedded operating system, and the unit is verified and tested at last.The hardware circuit of motor protection unit is constituted by six parts such as powersupply, the minimum system of CPU, data acquisition circuit，signal processing and A/Dconversion circuit, the output circuit and communication interface circuit. A large number ofanti-interference means as well as X and Y-type capacitors and surge absorber are used in thecircuit to maximize reduce the common mode interference and differential mode interferenceof system in design. The independent power supply for multiple devices in protection deviceis designed to achieve power isolation and reduce the ripple interference of power system.The Hall transformer is used to collect signal, it can achieve the isolation of high voltageelectrical and low voltage electrical. The output circuit is achieved based on micro-relay, therelay driver circuit using the measures of series the photoelectric coupler and NAND gate toisolate signal and prevent unit malfunction. The two-way asynchronous communication serialports are designed in the unit: one is used to test and download program for the phase of unitcommissioning, and the other is used to communicate with the host computer in live.In the software, the data acquisition and algorithm, motor overload, locked rotor, shortcircuit, starting timeout and output mission are analyzed and designed in the paper. TheFourier algorithm is used to discrete the data and the root mean square multi-point algorithmis used to achieve a smoothing filter. In-Application Programming (IAP) is designed toachieve system configuration, and the fault recording software is designed to record motorfailure data for motor overhaul or analysis at last.The testing results show that: the function and performance features of motor protectionunit meet the requirements of technical standards. The motor protection unit has achieved the expected target.