An Insulation Monitoring Device (IMD) is a requirement within IT power systems according to BS7671:2018. However, insulation fault location (EDS) is only a recommendation and is often overlooked during system design. EDS is the money saver… Here’s why!
What is EDS and how does it work?
EDS is used in combination with an IMD for the localisation of insulation faults in unearthed power supplies (IT systems). An EDS system comprises of an insulation fault evaluator connected to a current transformer (CT) located around the desired cables/equipment to be monitored.
How it works:
An insulation fault is detected by the IMD, which communicates with the EDS to switch to find a fault
The IMD sends a pre-determined test current pulse via the live conductors across the power system
The test current signal is detected by the measuring current transformers on the circuit and evaluated by the EDS insulation fault evaluators
The fault location is determined by the EDS communicating which CT has detected the lowest insulation fault value (Rf)
Fault information is communicated locally via the device, Modbus, e-mail, SMS or any other communication method