Operation Principle - ABB REL650 series Technical Manual

Section 10
Secondary system supervision
10.2.7
10.2.7.1
336

Operation principle

Zero and negative sequence detection
The zero and negative sequence function continuously measures the currents and voltages
in all three phases and calculates: (see figure 158)
• the zero-sequence voltage 3V
• the zero-sequence current 3I
• the negative sequence current 3I
• the negative sequence voltage 3V
The measured signals are compared with their respective set values 3V0PU and 3I0PU,
3V2PU and 3I2PU.
The function enable the internal signal FuseFailDetZeroSeq if the measured zero-
sequence voltage is higher than the set value 3V0PU and the measured zero-sequence
current is below the set value 3I0PU.
The function enable the internal signal FuseFailDetNegSeq if the measured negative
sequence voltage is higher than the set value 3V2PU and the measured negative sequence
current is below the set value 3I2PU.
A drop off delay of 100 ms for the measured zero-sequence and negative sequence current
will prevent a false fuse failure detection at un-equal breaker opening at the two line ends.
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1MRK 506 335-UUS A
Technical manual