Mounting and Commissioning
3.3 Commissioning
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
439
Caution!
Possible starpoint earthing at transformer with simultaneous earthing on high voltage side during test!
Nonobservance of the following procedures can result in minor injury or material damage.
The starpoints of the unit transformer must be disconnected from earth during this test!
Start up the generator and slowly excite it to 30 % of rated machine voltage (max. 60 %).
The 100 % and 90 % stator earth fault protection does not pick up.
The checks to be performed for the 90% stator earth fault protection are described under margin title „Check
in Case of Network Earth Fault“ in the previous section.
For the 100-% stator earth fault protection, read out the operational measured value I SEF. This value is ex-
trapolated to approx. 1.3 times the rated machine voltage. The current thus extrapolated should not exceed half
the pickup value SEF I>> (address 5306) in order to achieve the desired safety margin of the current stage
of the 100% stator earth fault protection.
Shut down and de-excite the generator. Remove earth fault bridge.
If the starpoint of the high-voltage side of the unit transformer is to be earthed during normal operation,
now reestablish starpoint earthing.
If the 20 Hz generator is to be fed by the voltage transformers of the machine terminals, this or a different type
of supply connection (e.g. DC voltage supply from a battery) must permanently be established.
If no more special tests are to be made, activate the 100% stator earth fault protection: set address 5301 100%
SEF-PROT. to ON.
3.3.18 Checking the Sensitive Earth Fault Protection as Rotor Earth Fault Protection
If the sensitive earth fault protection is used for rotor earth fault protection, it must first be set to O/C PROT.
IEE Block relay at addresse 5101.
Caution!
A rotor circuit not isolated from earth can result in a double earth fault in conjunction with an earth resistor in-
serted for checking purposes!
Nonobservance of the following procedures can result in material damage to the machine.
Make sure that the checked rotor circuit is completely isolated from the earth, to avoid that the earthing resistor
interposed for test purposes causes a double earth fault!
An earth fault is simulated via a resistor which is roughly equivalent to the desired trip resistance. In generators
with rotating rectifier excitation, the resistor is placed between the two measurement slip rings; in generators
with excitation via slip rings between one slip ring and earth.
Start up generator and excite it to rated voltage. If applicable, place measurement brushes into operation. It is
irrelevant in this context whether the sensitive earth fault protection picks up or not. The earth current I
EE
that
is flowing now can be read out on the device under the operational measured values.
Check that this measured earth fault current is roughly equal to the pickup value 5102 for sensitive earth fault
detection that has been set in address IEE>. However, it must not be set to less than double the value of the
spill current that has been determined for healthy insulation.
For generators with excitation via slip rings, the test can be repeated for the other slip ring.
Shut down generator. Remove earth fault resistor.
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