What are Insulation Monitoring Devices?
Insulation monitoring devices (IMD), or insulation monitors, are safety components detect insulation faults within ungrounded (unearthed) power grid systems between an active phase conductor and earth. The insulation monitor continuously monitors the insulation resistance performance in the power grid and activate the insulation monitor's alarm function (sound or light) when the insulation resistance falls below the set value.
At present, the measurement principle of insulation monitoring device is divided into two main technical routes, namely current injection method and balanced bridge method. However, due to the reasons of stable performance and accurate measurement, the development of insulation monitoring devices is mainly based on current injection.
The current injection method is divided into AC injection and DC injection. Due to the characteristics of DC itself, the DC injection method cannot be accurately measured in AC/DC hybrid power grids and DC power grids. It can only be used for pure AC power grid systems or offline insulation monitoring of power grids. for example, Sikcon's SKIM500, SKIM24-3C and high voltage motor offline insulation monitor are products designed using the DC injection method.
Since there is no requirement for the measurement power grid, the advantages of the AC injection method are highlighted. The AC injection method can be used not only for pure AC grids and DC grids, but also for AC/DC hybrid grids, for example, Sikcon's SKIM200, SKIM400, SKIM600 series use low-frequency AC injection, while SKIM800 uses AC pulse square wave injection.
Insulation monitoring devices should be used in some important areas, such as hospitals, railways, ports, to ensure that these institutions can continue to operate, IMD enables signalling system engineers to detect insulation failures early. This prevents potential electrical shocks, fires, or damage to lineside equipment, supports signalling system uptime, and avoids disruption to public services.
Some heavy industry fields, such as mining, chemical industry, steel mills, oil production plants, power plants, etc., have a large number of motors and complex power grids, which are the places where production accidents are most likely to occur. Insulation monitors can effectively monitor insulation faults in motors or power grid systems in the above industries.
In some emerging industries, such as electric vehicles, energy storage, and battery management, it is necessary to ensure people's safety in daily life and prevent insulation failure and other leakage risks. Therefore, it is necessary to consider the configuration of insulation monitors or leakage relays for the above equipment, Sikcon's SKIM1500EV is a dedicated insulation monitor designed for insulation monitoring needs of DC systems such as charging stations, energy storage and battery management, using the low-frequency AC injection principle.
