Siemens SIPROTEC 7UM62 - Page 432

Mounting and Commissioning
3.3 Commissioning
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
432
Figure 3-35 Displacement voltage during earth faults
Checking for Generator Earth Fault
Switch rotor earth fault protection S/E/F PROT. (address 5001) to Block relay. If the sensitive earth fault
detection is used for stator earth fault protection, switch it to Block relay also under address 5101 as well.
With the primary equipment disconnected and earthed, insert a single-pole earth fault bridge in the generator
terminal circuit.
DANGER!
Primary measurements may only be carried out with the generator at stand–still on disconnected and grounded
equipment of the power system.
Start generator and slowly excite to about 20 % U
N
.
Read out U
E
from the operational measured values and check for plausibility.
If the plant has more voltage transformers with broken delta windings, the voltage U
E
must be measured on
them as well.
For protection zone Z the following applies:
Example:
Machine voltage at pick-up 0.1 x U
sec N
When reading the fault log buffer „U Earth Lx“ „Lx“ indicates the faulted phase provided voltages are con-
nected to the voltage protection inputs of the device.
Shut down generator. Remove earth fault bridge.
Measured value U
G
= 10 V
Setting value U0> = 10 V
Protection range L = 90 %