Mounting and Commissioning
3.3 Commissioning
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
442
Shut down the generator. Remove short-circuit bridge.
The measured displacement voltage has to be extrapolated to the nominal excitation current to make sure that
the function does not pick up erroneously on external short-circuits. The function is then set to at least twice
the fault value at nominal excitation.
If the field forcing current is known, the fault voltage has to be extrapolated to this value. The protection is then
set to 1.5 times the fault value.
To find out how sensitive the protection is, determine the content of the protected phase winding at no-load
excitation. For this purpose, insert a single-phase short-circuit between a conductor and the starpoint.
DANGER!
Primary measurements may only be carried out with the generator at standstill on disconnected and earthed
equipment of the power system.
Adjust the excitation to „manual“ mode.
Run up the generator, but not higher than the excitation at which the above calculated unbalanced load (for
single-pole fault) is not exceeded. Read the measured displacement voltage out of the operational measured
values.
Shut down the generator. Remove short-circuit bridge.
Extrapolate the measured voltage to the value at no-load excitation. The percentage of the protected winding
area can be derived from this value.
We assume that the Uwin voltage increases linearly with the number of short-circuited turns. Actually, the
voltage increase of an interturn fault with only a few turns is rather high, i.e. the protection is more sensitive
than calculated. To simplify matters, the linear approach was used.
After the test is completed, activate the interturn fault protection by setting address 5501 to INTERTURN PROT
= ON.
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