Protective Elements
Working Principle f< and f>
(Please refer to the block diagram on next page.)
The frequency element supervises the three voltages (depending on if the voltage transformers are wired in Star or
Delta connection »
VL12«, »VL23« und »VL31« oder »VL1«, »VL2« und »VL3«). If all of the three phase voltages
are e.g. below 15% Vn, the frequency calculation is blocked (settable via parameter »
V Block f«). According to the
frequency supervision mode set in the Device Planning (f< or f>), the evaluated phase voltages are compared to the
set pickup threshold for over- or under-frequency.
If in any of the phases, the frequency exceeds or falls below the
set pickup threshold and if there are no blocking commands for the frequency element, an alarm is issued
instantaneously and the tripping delay timer is started. When the frequency still exceeds or is below the set pickup
threshold after the tripping delay timer has elapsed, a tripping command will be issued.
402
MRU4
DOK-HB-MRU4-2E
Содержание High PROTEC MRU4
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