Table of Contents
Advertisement
3 Mounting and Commissioning
For protection zone Z the following applies:
Example:
Machine voltage at pickup 0.1 x U
With Directional De-
The earth fault directional determination requires a check of the current and voltage
termination
connections for correctness 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 fac-
tory). 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 transform-
ers (as viewed from the machine).
DANGER!
Warning of hazardous voltages on equipment components, e.g. due to capacitative
coupling with other components!
Nonobservance of the following measure will result in fatality, severe personal injury
or substantial material damage.
Primary steps may be undertaken only on machine standstill.
Before carrying out primary steps on components they must be earthed.
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 negligible 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
If loading equipment is not available and if an earth fault test with the network is not
with Toroidal CTs
possible, then the following test can be performed with secondary measures, however
without Loading
with the symmetrical primary load current:
Resistor
With current supplied from a toroidal residual current transformer, a voltage transform-
er (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
282
Measured value
Setting value
Protected zone
N
U
E
U0>
Z
= 10 V
= 10 V
= 90 %
7UM61 Manual
C53000-G1176-C127-3
Advertisement
Table of Contents
