1. The document provides instructions for testing the settings of a SPAD 3G1 J6 differential protection relay using an MP3000 relay tester. The relay detects current differences in the generator stator winding. 2. The test involves injecting differential currents into the relay and measuring the trip time. Both the basic and bias settings will be tested by incrementally increasing the differential current and observing the relay's response. 3. Parameters such as the differential and restrain currents, test duration, and interval times are configured in the MPWIN software to automatically test the relay's operation and record the results.

1. Procedure for testing of SPAD 3G1 J6
(Differential protection relay)
The protection relay used to detect the current differences / faults of generator stator
winding by measuring difference of currents entering and leaving at its either ends. The
currents are being sensed by 2 current transformers installed at each phase winding.
 Before the generator stator winding 
 And at the MV cubicle 
Both are rated at 1000/1/1 A and having accuracy class 5P20 10 VA
Relay Terminal configuration:
For testing each phase of differential relay following connections must be done.
1. Remove the current inputs from protection relay terminals A1 and B1 and A5
and B5. A1 & B1 terminals will be connected to separate current outputs from
tester and A5, B5 connected to the neutral point of tester.
2. All other phases will be tested in same manner refer drawing (manual
J342). (Phase 2: A2& B2, phase 3:A3 & B3 ; (their respective neutrals will be
connected to each other and neutral from tester, for phase 2; A6 & B6, and
for phase 3; A7 & B7)
3. From tester, current outputs I1, I2 and N will be used accordingly.
There are two settings made in differential relay,
Basic setting “p“(%)
Bias setting “s” (%)
Basic differential; (p) = 10 %
The basic setting defines that the range of differential current for which the relay operates
without any biasness, i.e. from zero to 0.5 *In (nominal current of CT), the differential relay
operates for the same amount of current which, it is being measuring as difference. The
nominal CT output current is 1 A, therefore the basic setting of current is 10%*1= 0.1 A. The
currents corresponding to the 0.1 A in actual to = 0.1 *1000 =100 A, Means minimum 100A
differential current is required for tripping the circuit breaker.
Bias degree; (s) = 5%
For BIAS setting, using formula

2. This current value is the minimum value at output of current transformer which is required for
the operation of relay after the fault current value raises above the 0.5 A range
The currents corresponding to the 0.2 A in actual equals to 0.2*1000 = 200 A
Testing of SPAD 3G1J6 on MP3000 relay tester.
1. The functionality of settings made in differential relay will be tested by injecting
the corresponding differential currents and trip time
is measured.
2. Select the Differential relay module (in more
option) of MPWIN software to test SPAD 3G1J6.
3. The output terminals A4 and A8 are connected to
binary input no#1 of relay tester and checked for
contact change at each time relay gives trip signal.
4. We will be checking one by one each phase differential current setting
For testing the basic setting of relay:
Enter the following parameters in each window
1. The differential current of 0.1 A is to be detected by relay, in this regard , the restrain
current (Ir) is started from 0 and increased in increments of 0.05 A up to 0.8 A.
2. The differential current also started from zero and in increments of 0.05 Amp, and it
rose up to 0.3 Amp.

3. 3. The relay should detect the difference of 0.1 Amp when the I1 input (Ir) raises equals to or
above 0.4 Amperes; both current inputs are allowed to increase up till the relay senses the
current difference of 0.1 Amps.
The second window is filled as follows: where we made the settings of output current
4. either DC or AC
5. Reset time for contacts once tripping occurred.
6. Total duration of test, this can be conveniently set to less than 30 seconds also, as
differential relay trip time itself in milliseconds.
7. And interval time between two successive increments of currents.
The third window parameters will be filled as follows, here the curve characteristics of the
differential relay could be defined and checked with respect to the actual curve of
differential relay.

4. Press the play button and record the test results as displayed by the software. The tripping
values recorded by software will be at every step current values regardless of the tripping
being detected or not, here all the test point will be checked automatically giving complete
relay behavior
For testing the bias setting of relay
1. The currents are fed as above mentioned settings:
2. The currents Ir starts with 0.7 Amps, while Id starts with 0.1 Amps value, keeping an
initial current difference of 0.6 Amps.
3. The current Ir and Id both increases and reach 0.9 and 0.3 Amp respectively. After this
point the difference increases up to 0.3 Ampere , as Ir increases further above 0.9 A and Id
remains constant the difference will be increased further now, when the current

5. differential of 0.2 A is created (above 0.5 Amp or total current differential of 0.7
Amp). The relay should trip at this point.
The parameter tab parameters are entered as follows:
The coefficient tab parameters are entered as follows:
4. Press the play button and record the test results as displayed by the software. The tripping
values recorded by software will be at every step current values regardless of the tripping
being detected or not, here all the test point will be checked automatically giving complete
relay behavior
5. After the test has been completed normalized all the connections properly.