Figure. 5.4.12 - 75. Earth fault in isolated network.
Figure. 5.4.12 - 76. Close-distance short-circuit between phases 1 and 3.
The monitored voltage magnitudes are equal to RMS values. The blocking signal and the setting group
selection control the operating characteristics of the function during normal operation, i.e. the user or
user-defined logic can change function parameters while the function is running.
The neutral overvoltage function uses a total of eight (8) separate setting groups which can be
selected from one common source.
The function can operate on instant or time-delayed mode. In the time-delayed mode the operation can
be selected for definite time (DT) or for inverse definite minimum time (IDMT); the IDMT operation
supports both IEC and ANSI standard time delays as well as custom parameters.
The operational logic consists of the following:
• input magnitude selection
• input magnitude processing
• threshold comparator
• block signal check
• time delay characteristics
• output processing.
The inputs for the function are the following:
• operating mode selections
• setting parameters
• digital inputs and logic signals
• measured and pre-processed voltage magnitudes.
A
AQ
Q-M257
-M257
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
IM00021
149
Summary of Contents for AQ-M257
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