To avoid spurious operation of any other protection elements all protection elements except the
thermal protection should be disabled for the duration of the thermal element tests. This is done in the
relay’s CONFIGURATION column. Make a note of which elements need to be re-enabled after testing.
2.1.12.1 Connect the Test Circuit
To determine which output relay has been selected to operate when a thermal trip occurs by viewing
the IO CONFIGURATION menu settings or by extracting IO Mask file from the relay using P50 Agile
configurator.
If the Thermal Trip (THOL Trip)/General Trip is not mapped directly to an output relay, then the THOL
Trip/General Trip function can be easily assigned to any of the output relays (RL1..RL6) by making
desired configuration in IO CONFIGURATION menu or by making appropriate changes to the IO Mask
file. Similar procedure can be followed to assign Thermal Alarm (THOL Alm) directly to any output
relay for testing.
The associated terminal numbers can be found from the external connection diagrams in the Wiring
Diagram chapter.
Connect the output relay so that its operation trips the test set and stops the timer. Connect the
current output of the test set to the A phase current transformer input of the relay (terminals B2 – B1 (1
A), B3– B1 (5 A).
Ensure the timer starts when the current is applied to the relay.
Note: If the timer does not start when the current is applied, the connections may be incorrect for the
direction of operation set. Try again with the current connections reversed.
2.1.12.2 Perform the Test
Ensure the timer on the test set is reset.
Ensure that the thermal state is reset (see in cell [MEASUREMENTS 2, Thermal State]. If not, this
reset can be done through the cell [RECORD CONTROL, Thermal Reset] by selecting YES.
Check the position of the interrupting device by viewing the status of the two opto-inputs (52a and 52b
status inputs) used to indicate the device position. The 52a input must be energised to simulate the
closed position of the interrupting device to enable the thermal protection heating time constants. The
cooling time constant is used when the interrupting device is open.
Apply a current of twice the setting [in cell [CONFIGURATION, IFL] to the relay and make a note of
the time, when the timer stops. If you have to repeat the test, make sure you disable Thermal Lockout.
Also make sure you disable the inhibit during start setting Inh Trip Dur St. Most portable secondary
injection test sets have limited current output capability. Therefore, it is suggested you change IFL to 1
A (after the as found value is recorded) and use 1A phase current input terminals. To save time during
testing, set all the thermal time constants to 5 minutes.
Ensure that the thermal state is reset to 0 (see cell [MEASUREMENTS 2, Thermal State]. If not, the
thermal state can be reset through the cell [RECORD CONTROL, Thermal Reset] by selecting YES.
When the tests are complete, go to the CONFIGURATION column and restore all previously disabled
protection elements to their original settings.
2.1.12.3 Verify the Operating Time
This test is done by a single-phase injection on the A phase current input. This means the relay sees
equal current magnitudes for both positive and negative phase sequence quantities. On injection of a
single phase current value equal to I
inject, the relay sees current magnitudes of Iinject/3 for both the
positive and negative phase sequence quantities and I
inject for Irms. The equivalent thermal current
value I
eq calculated by the relay is given by following :
The equivalent motor heating current is calculated by:
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