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Motor Protection

This document provides procedures for testing motor protection relays, including: 1) Load jam protection testing which applies current gradually to relays until trip and checks trip time. 2) Thermal overload protection testing which applies current above threshold until thermal time elapses and checks trip time. 3) Starting supervision testing which applies current after starting supervision time elapses and checks trip time.

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2K views2 pages

Motor Protection

This document provides procedures for testing motor protection relays, including: 1) Load jam protection testing which applies current gradually to relays until trip and checks trip time. 2) Thermal overload protection testing which applies current above threshold until thermal time elapses and checks trip time. 3) Starting supervision testing which applies current after starting supervision time elapses and checks trip time.

Uploaded by

samlash
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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MOTOR PROTECTION RELAY TESTING

RC-IN EM DG S 1
PROCEDURE

Load Jam protection:

It is like an over current , apply all the three phase current to relays with below setting value and
increase gradually until rely gets trip.

Load jam protection will be enabled after blocking time has elapsed due to motor staring.

Apply the current with two times of setting value to the relay to check trip time across the respective
binary output contacts.

Phase Pickup Check Trip Time Check


Set Actual Injected Calculated Actual
I Pickup (A) I Pickup (A) Current (A) Trip Time (Sec) Trip Time (Sec)
R
Y
B

Thermal Over load Protection-49


Relay Opt. Time (t) = T * ln ( K2 - I ) /(K2 –1) )

Where T=Thermal time constant value in seconds


K= Ratio of Ieq/I theta
I eq = equivalent thermal current Value
I theta= thermal over load current threshold
I = Initial Thermal state of the motor

Now I eq 2= (I +ve) 2 + Ke ( I -ve)2

Where Ke can be set from 0 to 10

Apply all three phase current to relay with above the setting value until the thermal time has elapsed.

Then check the trip time across to the respective relay binary output.

Injected Calculated Actual


Stages Percentage% phase
Current Trip Time (Sec) Trip Time (Sec)
49-1 90 R-Y-B
49-2 100 R-Y-B

Starting Supervision.
MOTOR PROTECTION RELAY TESTING
RC-IN EM DG S 1
PROCEDURE

Motor starting is detected when a settable current threshold I MOTOR START is exceeded. Calculation of the
tripping time is then initiated. It should be noted that this timer starts every time the motor is started.

It will be operated after elapsed the starting supervision time.

Apply current above the setting value to relay & check trip time across the respective binary output.

Injected Pickup Current Calculated Actual


Phase
Current(A) (A) Trip Time (Sec) Trip Time (Sec)
R 3
Y 3
B 3

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