TD_MRN3-3_08.06_GB
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To prevent a possible false tripping the vector surge
measuring can be blocked at a set low input voltage
(refer to 5.4.10). The undervoltage lockout acts faster
then the vector surge measurement.
Vector surge tripping is blocked by a phase loss so
that a VT fault (e.g. faulty VTs fuse) does not cause
false tripping.
When switching on the aux. voltage or measuring
voltage , the vector surge supervision is blocked for 5
s (refer to chapter 4.8).
Note:
In order to avoid any adverse interference voltage ef-
fects, for instance from contactors or relays, which may
cause overfunctions,
MRN3-3
should be connected
separately to the busbar.
4.7 Measuring principle of vector
surge
supervision
When a synchronous generator is loaded, a rotor dis-
placement angle is build between the terminal voltage
(mains voltage) U1 and the synchronous internal volt-
age (Up). Therefore a voltage difference
∆
U is built
between Up and U1 (Fig. 4.4).
~
~
∆
U = I
1
jX
d
I
2
I
1
U
P
U
1
Mains
Z
Figure 4.4: Equivalent circuit at synchronous generator in parallel
with
the
mains
Figure 4.5: Voltage vectors at mains parallel operation
The rotor displacement angle
ϑ
between stator and
rotor is depending on the mechanical moving torque
of the generator shaft. The mechanical shaft power is
balanced with the electrical fed mains power, and
therefore the synchronous speed is maintained con-
stant (Fig. 4.5).