针对油田电网呈树型分布的特点,运用模拟电路故障诊断理论,研究了利用外加音频信号源的端口比值分支定位法及侧距算法,实现对油田电网短路故障的自动诊断.该诊断系统中的结合设备将诊断系统与高压电力线隔离,并将测试信号有效地耦合到电力线上.通过端口电压幅度及相位测量实现对油田电网短路故障的自动在线监测,一旦发现线路发生短路故障,可以快速地进行故障分支定位,并计算出故障点的距离. Aiming at the characteristics of oil field power grid being distributed in tree shape, this paper studies the method of port ratio branch localization and side distance algorithm based on analog circuit fault diagnosis theory to realize the automatic diagnosis of short circuit fault in oilfield power grid. Combined with the equipment, the diagnostic system is isolated from the high voltage power line, and the test signal is effectively coupled to the power line.Automatic on-line monitoring of short-circuit fault in the oilfield power grid can be realized by port voltage amplitude and phase measurement. Fault branch positioning, and calculate the distance of the fault point.