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This article introduces high-precision digital potentiometer, optical isolation and self-balancing bridge.The optical isolation between high and low pressure not only can achieve a complete electrical isolation,but also improve the anti-interference for the system. | Journal of Automation and Control Engineering, Vol. 1, No. 1, March 2013 Study on the Automatic Positioning for Cable Insulation Failure Based on Digital Bridge Method Wu Zhu, Hua-Fu Zhang, Wei-Ya Ma, and Yuan Gui Shanghai University of Electric Power Abstract—To against the problem of the difficult for indentifying the reflected wave of traveling wave and the need of plentiful practical experience and operation skills, this article focuses on designing and developing a digital cable insulation automatic fault locator. The instruments which can locate the fault without the data of length of the cable is based on the principle of HV bridge method and consist of bridge use for measuring cable length and bridge use for locating cable insulation fault. It can automatically improve voltage output of the high-voltage power through constant current detection circuit. To make sure the abilities of high accuracy,stability and fast for this instrument, This article introduces high-precision digital potentiometer, optical isolation and self-balancing bridge.The optical isolation between high and low pressure not only can achieve a complete electrical isolation,but also improve the anti-interference for the system. needs the cable length of the data with larger transition resistance will affect its accuracy. This study improves from the traditional bridge method such as improve bridge voltage, use multi-tap, high-precision digital potentiometer for self-balancing bridge, it will greatly reduce time for location. II. The overall scheme of the locator system is shown as below, the whole system is composed of high and low voltage bridge structure, low voltage bridge is used for measuring cable length, while high voltage cable is for insulation fault location which needs the length of cable data, through the reed switch to switch the high and low electric bridge. The system mainly includes a high voltage DC source module, a constant current control circuit, bridge zero .
