| Intelligent High-voltage Switch Cabinets compose a significant part of Smart PowerGrid as they often assume as the controlling and protecting devices in electrical powersupply system. The traditional switch cabinets have disadvantages in their too much simplefunction, people-acted inspection and maintaining cost. They are especially lag behind incurrent measuring because the Traditional Current Transformer has low measuringaccuracy and narrow frequency band. Therefore, a new online monitoring system isrequired to meet the demands of modern Smart Power Grid. The research and developmentof this online monitoring system will serve as an important exploration in this field.Primarily, a theoretical research has been conducted in current measuring forIntelligent High-voltage Switch Cabinets’ application, so as a creative measuring methodbased on magnetic sensors array has been proposed. A parallel array topology wasdesigned and the related mathematic model was obtained. Through the results ofexperiments, two conclusions can be obtained.(1)The measuring accuracy reached0.1F.Sin amplitude and0.2‰in phase, and this method boasts excellent performance inrepeatability(2) The optimizing topology for sensor array is a_A=50mm，a_B=40mm，a_C=30mm, b=150mm.Secondly, the online monitoring system has been realized, which including thefollowing contents.(1)In regard of the overall structure, the monitoring system employed anobject-oriented distributed monitoring structure so as to obtain higher performance inreal-timing and reliability.(2)In regard of hardware design, a double CPU structure based on Double Port RAMhas been proposed, and correspondingly, the hardware system was been divided into theAnalog Input Processing Module, the Monitoring and Protecting Singlechip Module, theMain Controlling Singlechip Module and the Power Supply Module. Each one was in charge of several independent functions, and the whole cost is very low.(3) The research in measuring and protecting algorithm found that the half-periodintegration is productive. The algorithm of electrical parameters on central monitoringstation which based on FFT has been introduced.(4)In regard of software design, Designing details in self-examination, dataacquirement and HMI was given, as well as the process and command word of handshakeprotocol. On the other hand, the software development for central monitoring stationinvolved the definition of wave file and the development of wave displaying module. Theonline monitoring system above is easy to realize and characterized by good property inreal-timing and reliability. It can provide a high sampling speed by10kS/s and could reacha less than10ms protecting speed when there is a system failure while costs several dozensof RMB.At the end, the anti-interference design was conducted actual use. By analyzing thesource of electromagnetic interference and their emitting and coupling characteristics, asimulation on distributing style of electromagnetic field in current bus room was conductedby ANSYS. Correspondingly, several methods in decreasing these magnetic interferenceswere proposed in the following fields: interference screening, distribution of weak signalcable, as well as several measures in hardware and software designing.The final debugging results show that the monitor system has a0.2F.S accuracy incurrent measurement and0.35%in measurement repeatability. |
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