Insulation fault detection circuit for ungrounded DC power supply systems

Abstract

This paper proposes a novel online insulation fault detection circuit to overcome the shortcomings of ungrounded DC power supply system for being unable to provide high sensitivity leakage current detection. In this paper, the capacitor group is used to connect with positive and negative bus and ground the intermediate point of the capacitor group, and that each branch loop is installed with a leakage current detection device. When insulation fault occur in the system, the capacitor is able to provide a leakage current return path and discharge through the stored energy in the capacitor. This will allow the Hall effect current sensor to detect the difference of positive and negative bus current, and deliver warning signal or control the breaker to cut off the power supply. The experiment result demonstrates that this novel method is able to detect 1mA/50kΩ insulation fault to achieve the high sensitivity detection goal.

Study on the Charge Transfer Criterion for the Pole-to-Ground Fault in DC Distribution Networks

“…Q being negative suggests that the charges flow out of generalized node l 2 . Substitute the values of line length, unit capacitance and voltage parameters into (15), Q ≈ −0.03. Fig.…”

“…Some research revolving around the protection principles and methods of the pole-to-ground fault in a DC distribution network has been carried out and preliminary results have been achieved. Considering the fault current is too small, a method to identify the pole-to-ground fault by detecting the steady-state leakage current, which will not be affected by the capacitance-to-ground is proposed in [15], but it requires high precision for the detecting equipment. A method of detecting and identifying the pole-to-ground fault by injecting an alternating current into the line when a fault occurs is proposed in [16].…”

Method and device for detection of insulation breakdown on hull in power circuits of locomotives

“…Самый традиционный метод определения аварийного состояния изоляции, получивший наибольшее распространение вследствие своей простоты, основан на измерении напряжения в любой точке плюсовых или минусовых цепей высокого напряжения относительно корпуса [3,4]. Однако такой метод позволяет установить факт наличия аварии, но не обнаружить, в каком из устройств схемы она произошла [5][6][7][8]. Предложен метод, повышающий эффективность существующего путем сокращения времени выявления и позволяющий вместе с обнаружением наличия пробоя также установить, какой именно тяговый электродвигатель является аварийным.…”

Insulation Monitoring Method for DC Systems with Ground Capacitance in Electric Vehicles

“…Various insulation-monitoring devices and embedded circuits have been designed and installed in DC charging piles, battery packs, high-voltage distribution boxes, and other equipment or embedded in the battery management system of EVs. DC-IM methods include balanced electric bridge [9], unbalanced electric bridge [10][11][12][13][14], high-voltage injection [15], differential amplification [16], and low-frequency small-signal injection [17,18]. The unbalanced electric bridge method can synchronously monitor positive and negative insulation resistances, has a low cost, and is easy to realize; thus, it has been widely used in EVs and charging piles.…”