What is time setting in relay?
What is time setting in relay?
The adjustment of traveling distance of an electromechanical relay is commonly known as time setting. This adjustment is commonly known as time setting multiplier of relay. The time setting dial is calibrated from 0 to 1 in steps of 0.05 sec.
How is definite minimum time achieved in an IDMT relay?
Inverse Definite Minimum Time (IDMT) Relays: This is achieved by using a core of the electromagnet which gets saturated for currents slightly greater than the pick-up current.
How do you calculate relay time?
Operating Time of Relay for Extreme Inverse Curve (t) =80/ ((PSM)2 -1). Operating Time of Relay for Long Time Inverse Curve (t) =120 / ((PSM) -1). Operating Time of Relay for Normal Inverse Curve (t) =0.14 / ((PSM) 0.02 -1). Operating Time of Previous upstream Relay = Actual operating Time of Relay+ Total Grading Time.
What is the time current characteristics of IDMT relays?
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.
Where is the plug setting on a relay?
Plug setting multiplier is nothing but a ratio between the actual fault current in the relay operating coil to pick up current (the relay current setting). In other words, the ratio between the CT (current transformer) secondary current to relay operating current is called plug setting multiplier (PSM).
Why PSM is used in relay?
This ratio abs(I / Iref) is called the Plug Setting Multiplier (PSM). The value of PSM indicates the severity of the fault as seen by the relay. Trip the device, if PSM is above the threshold.
Why IDMT relays are better?
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. The inverse characteristic of the relay is more than the IDMT.
What is meant by relay setting?
Relay settings means actual value of the energizing or characteristic quantity at which the relay is designed to operate under given conditions.
What is TSM in relay?
Time Setting Multiplier (TSM): The arrangement provided for setting the operating time of protective relay from zero sec to maximum permissible time for a specified current setting is known as time setting multiplier. It is the ratio of fault current in relay coil to pick-up current.
What are the applications of over current relay?
Application: Definite time over current relay is used as:
- Back up protection of distance relay of transmission line with time delay.
- Back up protection to differential relay of power transformer with time delay.
- Main protection to outgoing feeders and bus couplers with adjustable time delay setting.
What are the application of IDMT relay?
Inverse Time Overcurrent Relays (IDMT Relay) In this type of relays, operating time is inversely changed with current. So, high current will operate overcurrent relay faster than lower ones. There are standard inverse, very inverse and extremely inverse types.
How is the operating time of an IDMT relay determined?
The relay operating time is inversely proportional to the magnitude of the fault current. For low amount of fault current relay takes more time to operate, for higher current the relay trips fastly. The relay operates according to its characteristics curve. The IDMT relay should be coordinated with other feeder’s definite time relays.
What is the inverse mean time of IDMT?
IDMT: Inverse definite Mean Time The relay operating time is inversely proportional to the magnitude of the fault current. For low amount of fault current relay takes more time to operate, for higher current the relay trips fastly. The relay operates according to its characteristics curve.
What are the IEC based IDMT settings of phase over?
It is seen by adjusting the position of a plug in a plug bridge. Example: For a 100/5A CT, if the relay is set to operate at 5A, the plug setting will be: P.S (%) = (Relay current setting)/5A = 5A/5A = 100%. Likewise, for the relay to operate at 2.5A, P.S (%) = 2.5A/5A = 50%. 2) Time Multiplier Settings (TMS)
How is the trip time of a relay calculated?
It means that the trip time is inversely proportional to the fault current. The trip time is calculated from the following parameters: Trip curve. Select from the standard set of IEC and IEEE curves. Realy pickup current (A). The electrical current trip setpoint on the relay. Fault current (A). The expected short circuit fault current.