IDMT Relay [Inverse Definite Minimum Time relay]

An IDMT (Inverse Definite Minimum Time) relay is a protection relay that trips a breaker when it detects overcurrent or earth fault. The higher the fault current, the faster it trips, but never faster than a set minimum time. This lets relays at different levels of the system work together so only the faulty section is disconnected.

Where it is used

• 11 kV HT panels with VCBs
• Transformer primary and secondary protection
• LT panel incomers with ACBs
• Generator and feeder protection

How to choose

• Functions: overcurrent, earth fault, or both.
• CT secondary: 1 A or 5 A to match the current transformers.
• Curve types (normal, very and extremely inverse) and setting ranges.
• Auxiliary supply available in the panel.
• Coordination with the utility and downstream breakers.

Why buy from Unique Quality Engineering

Since 2012 we have supplied genuine components from ABB, Schneider Electric, Siemens, Mitsubishi and Fuji Electric to panel builders, factories and contractors across Bangladesh. Our engineers help you choose the right rating and model, and we use the same parts in the panels we build ourselves.

Frequently asked questions

Why is it called inverse time?

Because the trip time is inversely related to the current: a large fault trips quickly, a small overload trips slowly.

Who sets the IDMT relay?

Settings should come from a coordination study that matches the utility, transformer and LT panel protection. Our engineers can help during commissioning.

Can an IDMT relay work with an ACB?

Yes, through CTs and the shunt trip of the breaker. Many ACBs also have built-in electronic protection.

Need a price for IDMT relays? Request a quotation with the rating and quantity, or call or WhatsApp +8801992-389515.