The outputs of the function are the START and ALARM ACT signals for the phase current ("THDPH")
and the residual currents ("THDI01" and "THDI02") as well as BLOCKED signals. The function uses a
total of eight (8) separate setting groups which can be selected from one common source.
The operational logic consists of the following:
• input magnitude processing
• threshold comparator
• block signal chec
• time delay characteristics
• output processing.
The inputs of the function are the following:
• setting parameters
• digital inputs and logic signals
• measured and pre-processed current magnitudes
The function's outputs are START and ALARM ACT signals can be used for direct I/O controlling and
user logic programming. The function generates general time-stamped ON/OFF events to the common
event buffer from each of the output signals. The time stamp resolution is 1 ms. The function also
provides a resettable cumulative counter for the START, ALARM and BLOCKED events.
The following figure presents a simplified function block diagram of the total harmonic distortion
monitor function.
Figure. 5.5.5 - 92. Simplified function block diagram of the total harmonic distortion monitor function.
Measured input
The function block uses analog current measurement values. The function always uses FFT
measurement of the whole harmonic specter of 32 components from each measured current channel.
From these measurements the function calculates either the amplitude ratio or the power ratio. A -20
ms averaged value of the selected magnitude is used for pre-fault data registering.
Table. 5.5.5 - 121. Measurement inputs of the total harmonic distortion monitor function.
Signal
Description
Time base
IL1FFT
FFT measurement of phase L1 (A) current
5ms
IL2FFT
FFT measurement of phase L2 (B) current
5ms
A
AQ
Q-S255
-S255
Instruction manual
Version: 2.06
© Arcteq Relays Ltd
IM00025
175
Содержание AQ-S255
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