Scaled output
value 1
-10
7
...10
7
0.00001 0
To where measured milliamp signal should be scaled at point 1.
Input value 2
0...4000
0.00001 1
Measured milliamp input value at curve point 2.
Scaled output
value 1
-10
7
...10
7
0.00001 0
To where measured milliamp signal should be scaled at point 2.
Add curvepoint
3...20
0:Not used
1:Used
n/a
0:Not
used
Instead of using linear curve between two points, create your own
curve with up to 20 curve points.
5.6. Monitoring functions
5.6.1. Current transformer supervision (CTS)
Current transformer supervision (CTS) function is meant to be used for monitoring the CTs, 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 are over the Iset Lowlimit setting
At least one of the three phase currents are 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 I2/I1 ratio setting
Calculated (IL1+IL2+IL3+I0) 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 from each of the two output signal. Time stamp
resolution is 1ms. Function provides also cumulative counters for CTS alarm and BLOCKED events.
Simpli ed function block diagram of CTS functionIn is presented in the following gure .
AQ-F255
Instruction manual
Version: 2.00
265
© Arcteq Relays Ltd
