MainsPro, SW version 1.4, ©ComAp – January 2013
MainsPro Application Guide
In case of mains failure or auto reclosing the generator suddenly feeds a very high consumer load.
The rotor displacement angle is decreased repeatedly and the voltage vector g changes its direction
to g’.
As shown in the timing diagram the voltage jumps to another value and the phase position changes.
This procedure is called phase or vector surge. MainsPro continuously measures the cycles, starting
each zero up ward slope. The time cycle is internally compared to the reference time. In case of vector
surge the zero up ward is delayed and the device trips instantaneously. The trip angle and
consequently the sensitivity of the vector surge detection is adjustable by the setpoint LOM: Vs lim.
Proper setting of Vector shift limit has to be examined at the field tests, especially at very low setting of
the protection limit (under 3°). Vector shift is very fast method and may be sensitive to disturbances,
naturally present in the electricity grid.
Note:
Due to high sensitivity, Vector shift protection is not evaluated in the transient states, e.g. when Alt
settings functionality is turned on or off, fault reset is performed or Vector shift limit is being set.
Functionality is blocked in the sine wave period, when such an event occurs.
M ain s
U e U g Z
l1 l2U
G en e ra tor M ain s /Lo a d
U
e
U
g
In p ara lle l w ith th e m a in s
M ain s
U e U´g Z
l´1U´
G en e ra to r
L o a d
U
e
U
g
U´
g
A t m a in s fa ilu re
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