Ice NP900 Series, Инструкция по применению

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Application Guide - NP900 Series 461 (504
)
A996A
3.7 M
ONITORING FUNCTIONS
3.7.1 C
URRENT TRANSFORMER SUPERVISION
(CTS)
Current transformer supervision (CTS) function is meant to be used for monitoring the
CT:s, wirings in between of the IED and IED CT inputs in case of malfunction or wire
breaks. Open CT circuit can generate dangerously high voltages into the CT secondary
side as well as cause not intended activation of current balance monitoring functions.
CTS function constantly monitors phase current instant values as well as key calculated
magnitudes of the phase currents. Also residual current circuit can be monitored if the
residual current is measured from dedicated residual current CT. Residual circuit
monitoring can be enabled or disabled by user selection.
Blocking signal and setting group selection controls the operating characteristics of the
function during normal operation.
Outputs of the function are CTS alarm and Blocked signals. Setting parameters are static
inputs for the function which are changed only by user input in the setup phase of the
function. CTS function utilizes total of eight separate setting groups which can be selected
from one common source. Also the operating mode of the CTS can be changed by setting
group selection.
The operational logic consists of input magnitude processing, threshold comparator, block
signal check, time delay characteristics and output processing.
For the CTS function alarm activation following conditions has to be met simultaneously:
- None of the three phase currents is over the set
Iset Highlimit
setting
- At least one of the three phase currents is over the
Iset Lowlimit
setting
- At least one of the three phase currents is under the Iset Lowlimit setting
- Three phase current calculated Min/Max ratio is under the
Iset ratio
setting
- Negative sequence / Positive sequence ratio is over the
I1/I2 ratio
setting
- Calculated
(IL1
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+ IL2
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+ IL3
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+ I0
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)
difference is over the
Isum difference
setting (optional)
- Above mentioned condition is met until the set TCTS time
Inputs for the function are setting parameters and measured and pre-processed current
magnitudes. Function output signals can be used for direct IO controlling and also for user
logic programming. The function registers its operation into 12 last time-stamped registers
and also generates general time stamped ON/OFF events to the common event buffer