Table of Contents
Which curve IDMT relay follows?
The ‘EI’ type IDMT relay curve operates at very fast at high short-circuit currents and very slow at low short-circuit currents. This type of IDMT curve is most suited for coordination with fuses.
What is the IDMT relay?
IDMT relay is inverse definite minimum time relay. It is one in which Time of operation is inversely proportional to magnitude of fault current near pickup value and becomes substantially constant slightly above the pickup value of the Relay.
Why IDMT relays are widely used for overcurrent protection?
Inverse Definite Minimum Time (IDMT) Overcurrent Relays : The relay exhibits an inverse relation between operating time and fault current near pick-up value and becomes almost constant just above the pick-up value. IDMT relays are widely used for the protection of distribution lines or distribution feeders.
Which expression correctly represents the IDMT relay characteristics?
SOLUTION. Inverse Definite Minimum Time Overcurrent (IDMT) Relay: This type of relay gives an inverse time current characteristic at lower values of fault current and definite time characteristic at higher values of the fault current.
What is Idmt and DT?
Generally, the over current relays are differentiating with their time of operation. The most commonly used over current relays are IDMT (Inverse definite mean time) over current relays, DT (definite time) over current relays and Instantaneous time over current relays. They are designed to sense the over-current.
How does IDMT relay protect the system from over current?
Inverse Definite Minimum Time Relay The IDMT relay uses the electromagnetic core because it can easily saturate for the current having larger magnitude than pick up current. The relay is used for the protection of the distribution line.
What is the inverse time over current (TOC/IDMT) relay trip time calculator?
The Inverse Time Over Current (TOC/IDMT) relay trip time calculator calculates the protection trip time according to IEC 60255 and IEEE C37.112-1996 protection curves. Trip curve. Select from the standard set of IEC and IEEE curves. Relay pickup current (A). The electrical current pickup set point Is in the relay.
What is an IDMT curve?
Inverse Definite Minimum Time (IDMT)curves are used in both mechanical and electronic protection devices. These curves define the amount of time which should pass at a given current, before initiating an action, usually the tripping of a circuit breaker.
What is the standard for IDMT over current protection relay?
STANDARD IDMT OVERCURRENT PROTECTION RELAYS The current/time-tripping characteristics of IDMT protection relays may need to be changed according to the functioning time needed and the characteristics of other relay protection elements used in the electrical network0.10 For these needs, IEC 60255 determined the number of standard characteristics.
What is the working principle of 1mixed IDMT relay?
1Mixed IDMT and high set instantaneous Instantaneously overcurrent relay operates when the current exceeds its Pickup value. The operation of this relay is based on the current magnitude and it is without any time delay.