In this article we will learn about overcurrent relay types.
We will also know that what is working of overcurrent relay and overcurrent
relay type. Here we now discus about the overcurrent relay types and working.
Overcurrent Relay types and working
Relay is sensing equipment which senses abnormal voltage and
current conditions in power system and sends signals to circuit breaker to
remove faulty part from rest of power system.
First line of defense is provided by the primary relaying
equipment and second line of defense is provided by the backup relaying
equipment. Backup protection operates when primary protection has failed.
Overcurrent Relay types
The operating time of all over current relays tends to
become asymptotic to a definite minimum value with increase in the value of
current. This is inherent in electromagnetic relays due to saturation of the
magnetic circuit. These are following types of over current relay.
Instantaneous Over current Relay
In this relay, time of operation of relay does not depend on
the value of actuating quantity once it is more than pick up value. This is
property of electromagnetic attraction types of relay. Time of operation
usually .1s. It is one of the overcurrent relay types.
Inverse Time current Relay
In this relay, there is an inverse relationship between
actuating quantity and time of operation of the relay. All electromagnetic
induction types of relay are inverse time current relays to some or large extent.
It depends on how core iron gets saturated. If it saturates early, it becomes
definite time current relay. It is main overcurrent relay types.
Inverse Definite Minimum time current Relay
In this relay time of operation of the relay is inversely
proportional to current near pick up value and for values little after that. If
current increases more, then that time of operation becomes constant.
Very inverse Relay
In this type of relay, core does not saturate early, and
then inverse relationship can be introduced air gap in core. So, time current characteristics
are inverse for larger values of current and then become definite time curve.
Extremely Inverse Relay
In this relay, saturation occurs at much later stage and
current time curve is inverse for larger value of current curve.
Differential Relay
The principle of operation depends on a simple circulating current
principle, where the difference of the currents of the two CT s flow through
the relay under normal conditions or even under faults outside the protected
section.
Protective Relay
Protective Relay and systems detect abnormal condition like
fault in electrical circuit and operate automatic switch gear to isolate faulty
equipment’s from the system as quickly as possible.
Protective relay functions are association with the switch
gear to avert the consequences or faults. The switch gear must be capable of
interrupting both normal currents as well as fault currents. The protective
relay on the other hand must be able to recognize an abnormal condition in the
power system and take suitable steps to ensure its removal with least possible disturbance
to normal operation. It is also overcurrent relay types.
Hence it is the overcurrent relay typesif you will find any
incorrect above please comment below in comment box.
For knowing more about overcurrent relay types you must watch
this video.