Electrical Protection Relays
Types and their functions.
1 - Electrical Protection Relay:
2 - Types of Protection Relay:
Electrical protection relay has two type protecton as HT panel protection and LT panel protection.
- HT panel protection relay.
- LT panel protection relay.
3 - HT Panel Protection relay:
HT panel is used for distribution of 11 KV / 33 KV power supply.The HT power supply is received from GO switch and distributed to the transformer.HT panel has two types supply section one is receiving or incomer section and 2nd is distribution or feeder section. so we can categories it two types incomer safety and outgoing safety. READ MORE
1 - Over Current Relay:
Over current relay is an element of relay which is operated after crossing preset limit value of current and time then it provides tripping signal to the circuit breaker tripping coil. It is really current monitoring relay which is behave as per current condition.
Over current relay protects the electrical system like as transmission lines, transformers, generators from short
circuit, overload, ground fault etc.
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2 - Earth Fault Relay:
Restricted earth fault relay is used for protection of an earth fault for the restricted zone as per your requirement but mainly is used for ground fault in transformer HT side.
It is a very highly sensitive relay as 2-8% and another differential relay works as sensing 20-40%. It works as fast due to the simple measuring process with the help of one winding. It protects a zone between two measuring points.
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3 - Master Trip Relay:
Master relay is not a monitoring relay. It is used as isolation of protection relay and breaker trip coil. it is used in
HT panel for the safety of the protection relay. It is received multiple commands from the protection relay and then a single command is received by the breaker trip coil from the master trip coil.
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4 - Trip Circuit Supervision Relay:
The trip circuit supervision relay is a monitoring relay and it is known as numerical name 96 S. it is used for continuous monitoring of breaker trip circuit healthy or not healthy in HT panel in any premised or substation. If the trip circuit will not ok then it will provide an alarm for avoiding any fault.
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5 - Types of Over Current Relay:
Over current relay protects the electrical system like as transmission lines, transformers, generators from short circuit,
overload, ground fault etc.
If the fault current value is extra high then it will trip instantaneous or quick. So, this type over current relay can be categorized in different types as per fault current value. Let’s discuss about categories of over current relay.
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6 - HT Protection Relay Testing:
Now a days the digital protection relay mostly are using. If we want to check health performance then we will have to test of relay. First relay performance test is carried out after commissioning after that relay testing is carried out as base of annually time schedule.
Pre set value or protection relays are verified or tested through test equipment. a all protection relays are
also carried out maintenance activity. All connections are checked and clean properly.
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7 - LT Protection Relay Testing:
Now a days the digital protection relay mostly are using. If we want to check health performance then we will have to test of relay. First relay performance test is carried out after commissioning after that relay testing is carried out as base of annually time schedule.
Pre set value or protection relays are verified or tested through test equipment. a all protection relays are
also carried out maintenance activity. All connections are checked and clean properly.
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4 - LT Panel Protection relay.:
1 - Over voltage relay:
Over voltage relay is an electrical protection device which is used for prevention of exceeding system
voltage and operated after crossing pre set value of voltage and time then a tripping signal is provided to
the circuit breaker tripping coil. It is used in transformer outgoing isolation panel or LT panel or
feeder panel for controlling over voltage.
Over voltage relay continue monitors the default voltage level
of system. If the voltage level is exceed pre set voltage limit then system will be tripped.
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2 - Under voltage relay:
Under voltage relay is an electrical protection device which is used for prevention of decreasing system
voltage and operated after crossing pre set value of voltage and time then a tripping signal is provided to the circuit breaker
tripping coil. It is used in transformer outgoing isolation panel or LT panel or feeder panel for controlling under voltage.
Under voltage relay continue monitors the default voltage level of system. If the voltage level is decreased pre set voltage limit then system will be tripped.
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3 - Deferential Relay:
Differential relay is a protection device which is used for special selected zone. According principle of DR if a fault is occurred in a selected zone than input and output supply will be different then relay will provide a tripping signal to the breaker and system will safe. So it is called as differential relay.
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4 - Reverse Power Relay:
Reverse power relay is an electronic, microprocessors based protection device which is used for monitoring and stopping the power supply flowing grid side to the DG side. If accidentally leakage current is received by generator then it can start to running as motor. This situation may be very dangerous for generator set.
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5 - Power Factor Control Relay:
APFC relay is used for monitoring the system power factor and also controlling the capacitor for connecting and disconnecting to the busbar. When the power factor is monitored in low below pre set value as 9.9 then a signal is provided to the capacitor contactor coil for capacitor connect into busbar. After maintaining the power factor the outgoing signal is disconnected.
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