Mounting and Commissioning
3.3 Commissioning
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
435
Example:
Machine voltage at pick-up 0.1 x U
N
With Direction Determination
The earth fault directional determination requires a check of the current and voltage connections for correct-
ness and correct polarity. The machine is excited to a voltage that corresponds to a displacement voltage above
the pickup value. If the polarity is correct, the trip indication „S/E/F TRIP“ is output (LED 6 when delivered
from factory).
A cross check is then performed. After the generator has been de-excited and shut down, the earth fault bridge
is installed on the other side of the current transformers (as viewed from the machine).
DANGER!
Primary measurements may only be carried out with the generator at stand–still on disconnected and grounded
equipment of the power system.
After restarting and exciting the generator above the pickup value of the displacement voltage, „U0> picked
up“ picks up (LED 2 for group indication of a device pickup when delivered from factory), however the „3I0>
picked up“ indication does not appear and tripping does not occur. The measured value IEE should be neg-
ligible and on no account at nominal excitation should it be larger then half the setting value 3I0>.
Shut down and de-excite the generator. Remove earth fault bridge.
Directional Check with Toroidal CTs without Loading Resistor
If loading equipment is not available and if an earth fault test with the network is not possible, then the following
test can be performed with secondary measures, however with the symmetrical primary load current:
With current supplied from a toroidal residual current transformer, a voltage transformer (e.g. L1) is by-passed
which simulates the formation of a displacement voltage (see the following Figure). From the same phase, a
test current is fed via an impedance Z through the toroidal transformer. The connection and direction of the
current conductor through the toroidal transformer is to be closely checked. If the current is too small for the
relay to pickup, then its effect can be increased by looping the conductor several times through the toroidal
transformer.
For Z, either a resistor (30 to 500 Ω) or a capacitor (10 to 100 µF) connected in series with an inrush-current-
limiting resistor (approximately 50 to 100 Ω) is used. With correct connections, the described circuit results in
indications „U0> picked up“, „3I0> picked up“ and finally „S/E/F TRIP“ (LED 6).
Measured value U
G
= 10 V
Setting value U0> = 10 V
Protection range L = 90 %