The device monitors the insulation between common earth and return conductors in DC Railway Systems.
The device measures the voltage between a structure / building and a reference electrode connected with earth. For initialization the IMD learns the condition “return currents flow through the surrounding mass of earth” by way of a short-circuited surge arrestor. In this state the voltage increases significantly between the earth and the construction because part of the return current flows through the earth. This state is then recognized again when construction and earth are short-circuited. In this way any change caused by unintended grounding is detected reliably.
For further information please download our data sheet: