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What is synchronising relay? How to test a synchronising relay using relay test kit ?

Updated: Apr 11, 2021

Protective relay is a device which maintains the power system equipments and gives an output under an abnormal condition to ensure protection of the system. ... During testing, protective relay is made to undergo simulated field conditions to check its performance.

In below article we will be discussion the testing of Synchronising Relay - MX3EGIA using K68i .

Equipments Required:

1. Synchronizer Relay

2. Relay Test Kit K68i

3. Single‐phase 220V,15A AC Power Supply*

4. Potential Earth Conductor.

*No Welding load shall be connected from the same circuit.

Testing Steps:

Step 1: Connect the power supply to the Relay Test Kit K68i.

Please ensure proper Earthing of Relay Test Kit by the Green color of Earthing

Indicator on the bottom right side of the main display. If the color of the earthing

indicator is Red then user has to ensure the integrity of power supply earthing.

Step 2: Make proper connections of MX3EG1A Relay and Relay Test Kit K68i as

per shown diagram below:

Step 3: Switch ON the Relay test kit K68i using “Power on Switch” button and go

to “AC Test Module”. Select any two Voltage Sources among Ua, Ub, Uc.

Step 4: Consider one voltage source as a Generator Voltage Signal and other as a

Bus Voltage Signal. Then vary parameters (Magnitude, Frequency & Phase)

according to the requirement.

# For Instance, we need to compare the Bar Frequency(fb) with Rated

Frequency(fn). Then Select the “Frequency” as a function. If fn=50Hz

and fb=52Hz, then take the Ua as a Rated frequency signal and Ub as

a Bar frequency signal.

# Point to be Noted: At a time, one Voltage signal must remain

constant in terms of parameters (Voltage, frequency, phase) .

Here, we take Ua as constant signal as it is a rated frequency signal and Ub

as a variable signal. By Variable, we mean that the signal is being ramped.

Step 5: For ramping a signal, Tick the check box ✔ front of the Ua, Ub.

# Ramping can be done by both: Manual as well as Auto Mode. The

mode is selected by clicking the Auto/Manual tab key from the front

panel of Relay Test Kit K68i.

# For Manual Mode: Set Step Size(Hz) and Deglitch Time(ms)

# For Auto Mode: Set Step(s) , Mode and Deglitch Time(ms)

Step 6: Press “Run” after setting all values. Synchronizer relay will actuate as per

the set parameters and accordingly gives a binary output to the Relay Test Kit


This binary output cable from Synchronizer relay is being connected to

the binary input ports of Relay Test Kit K68i. The binary output

command can be seen via LEDs on the Relay Test Kit Display.

Results can be seen in terms of tripping time on the Test kit display

under Result Index. The report is shown on the display of Relay Test Kit

K68i. The reports can be saved by pressing “Save” tab key on the front display

of Relay Test Kit K68i and same can be downloaded via USB/VGA

Port(on the top of Relay Test Kit K68i) for documentation and data

analysis. You can save data up to 1GB.

Step 7: For testing the variations of other remaining parameters of Synchronizer

Relay, please follow the above‐mentioned steps.

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