Table of Contents
Advertisement
Functions
2.2 Voltage Protection 27, 59
For both under-voltage elements 27-1 PICKUP and 27-2 PICKUP the dropout ratio (= V
parameterized.
A parameter is set to specify, whether the measured values of all phases or only phases with the lowest value
for monitoring are being used.
The undervoltage protection works in an additional frequency range. This ensures that the protective function
is preserved even when it is applied e.g. as motor protection in context with decelerating motors. However,
the r.m.s. value of the positive-sequence voltage component is considered too small when severe frequency
deviations exist. This function therefore exhibits an overfunction.
Figure 2-3
shows a typical voltage profile during a fault for source side connection of the voltage trans-
formers. After the voltage has decreased below the pickup setting, tripping is initiated after time delay 27-1
DELAY. As long as the voltage remains below the drop out setting, reclosing is blocked. Only after the fault
has been cleared, i.e. when the voltage increases above the drop out level, the element drops out and allows
reclosing of the circuit breaker.
[stoerfallverlauf-speiseseitig-20100525, 1, en_US]
Figure 2-3
The following Figure shows the logic diagram of the undervoltage protection function.
40
Typical fault profile for supply-side connection of the voltage transformers
/V
dropout
pickup
SIPROTEC 4, 7RW80, Manual
C53000-G1140-C233-4, Edition 07.2018
) can be
Advertisement
Table of Contents
