The MIB, a member of the M II family of economical and highly functional digital protection relays, is a microprocessor based relay that provides three phase high impedance differential protection for Substation Bus-bars of any voltage level.

Use the MIB also to protect electrical machines like transformers, generators or motors against restricted earth faults.

Basic protection functions features include a high impedance differential protection unit with a tripping time of 1 1/2 cycles. Stability against external faults is guaranteed thanks to the use of a stabilizing resistor. The unit includes a set of MOVs (Metal Oxide Varistors) provided to clamp the secondary peak voltage below 2kV during fault conditions.

The relay includes open CT detection which provides an alarm when it detects sustained current unbalance conditions, issuing a warning signal and blocking the operation of the unit.