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(I.D.M.T.) RELAYThe over load inverse time relay is shown in fig 26. It consists of an upper electromagnet that has been provided with two windings one primary and the other secondary. Primary is connected to a current transformer in the line which is under protection and is provided with eight tappings. These tappings are connected to a plug setting bridge by which the number of turns to be used can be adjusted in order to have the desired current setting. The second winding called secondary is energized by the induction effect and is wound over the central limb of the upper magnet as well as it is spread over the two limbs of the lower magnet. By this method, the leakage flux from the upper magnet entering the disc have been displaced in phase from the flux entering the disc from the lower magnet. The deflecting torque is produced on the disc in the fashion as already explained. The spindle of the disc carries a moving contact which bridges two fixed contacts after the disc has rotated through a certain angle which has been set before. Any setting for this angle is possible varying from 0 to 360°. The variation of this angle imparts to the relay, various time settings.
The speed of rotation of the disc is dependent upon the torque which in turn is dependent on the current setting, when the load current increases from this setting it will increase the speed of rotation of the disc resulting into decrease of operation time. Thus the time current characteristics of the relay observe inverse-Square law. The definite minimum time characteristics of the relay are obtained by the use of a saturated upper magnet. This ensures that there is no further increase in f1ux when the current has reached a certain value and any further increase of current will not affect the relay operation. This results in a flattened current time characteristic and the relay obtains its name as Inverse definiteminimum time lag (I.D.M.T.) relay
The current time characteristics of the relay have been illustrated in Fig. 27. It represents the time required to close the trip contacts for different values of over current. Its horizontal scale is marked in terms of current-setting multipliers i.e. number of times the relay current is in excess of current setting
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What is an Inverse Time Device?
an inverse time protective device is a protective relay with definite minimum operating current and definite minimum operating time for a given current. the device will ensure that increasing current in a fault, that the operating time will be decreased. Preventing an overload.
What is the inverse time of the thermal overload?
what is the inverse time of the theraml overload?
How does time inverse over current relay work?
Over Current (Inverse Time) Over current relay function monitors the general balanced overloading and has current/time settings. This is determined by the overall protective discrimination scheme. There advantage over definite time relays is that they can have much shorter tripping times can be obtained without any risk to the protection selection process. These are classified in accordance with there characteristic curves, this indicates the speed of the operation. Based on this they are defined as being inverse, very inverse or extremely inverse. The typical settings for these relays are 0.7-2In (normal or rated generator current) in 1-10 second. Inducing a calibrated test current through the normal load current tests this relay.
What is the inverse of resistance?
The inverse of resistance is conductance.
The length of time between a point in one cycle and the same point in the next cycle of an ac wave is the?
this is called time period of the wave. it is also the inverse of frequency of wave.
What is IDMT stand for?
Inverse Definite Minimum Time
What is an Inverse Time Device?
an inverse time protective device is a protective relay with definite minimum operating current and definite minimum operating time for a given current. the device will ensure that increasing current in a fault, that the operating time will be decreased. Preventing an overload.
What is meant by IDMTL type relay?
Inverse definite minimum time lag relay
What is idmt relay?
Inverse Definite Minimum Time Lag = IDMT relay It's a electromagnetic type rotating disk relay. Tripping time of relay decreases with increasing fault current. see http://myweb.tiscali.co.uk/robert.booth/uni/docs/Power%20Supply%20Assignment%203.pdf
What is the difference between idmt and dmt?
idmt means inverse definite minimum time. so in this type of relay as the value of operand that is current increase time taken by the relay to operate decrease. higher the current lower is the time taken by the relay to operate. AND dmt definite minimum time (DMT) relay take its minimum time to operate regardless of the value of the current. The definite mean time lag in disc type EM relays is inverse to current as the disc is faster at higher current and hence the less time.Definite mean time lag is possible in static relays by setting the time lag.
What is high set and low set current setting?
The low-set stage is a current with a definite time or inverse-time operation. The high-set stage has a definite time characteristic only without the inverse-time operation.
What is dmt and idmt relay?
DMT relay stands for definitive mean time, and IDMT stands for inverse definitive mean time. In IDMT relay, there is a minimum time delay with magnitude.
What is the inverse time of the thermal overload?
what is the inverse time of the theraml overload?
What is IDMT What is the principle?
IDMT stands for Inverse Definite Minimum Time. It is a protection relay characteristic commonly used in power systems to provide protection against overcurrent conditions. The principle of IDMT is that the tripping time of the relay is inversely proportional to the magnitude of the current, such that higher overcurrents result in faster tripping times to quickly isolate the fault and prevent damage to the system.
What is the inverse of period?
The inverse of period is frequency. Period refers to the time it takes to complete one cycle of a repeating event, while frequency represents the number of cycles that occur in a unit of time.
What is a sentence with the word definite?
I will have a definite answer in about ten minutes. You must give me a definite time to meet you.
How does time inverse over current relay work?
Over Current (Inverse Time) Over current relay function monitors the general balanced overloading and has current/time settings. This is determined by the overall protective discrimination scheme. There advantage over definite time relays is that they can have much shorter tripping times can be obtained without any risk to the protection selection process. These are classified in accordance with there characteristic curves, this indicates the speed of the operation. Based on this they are defined as being inverse, very inverse or extremely inverse. The typical settings for these relays are 0.7-2In (normal or rated generator current) in 1-10 second. Inducing a calibrated test current through the normal load current tests this relay.
