In case “Forced CT f tracking” is on, while voltages are gone, the frequency from selected current
based reference channel 3 (current from IL3) is used for current sampling. This eliminates possible
measurement error in xed frequency mode.
Figure. 5.4.22. - 109. Frequency reference channels.
An example, 500A of current measured on primary side, while xed frequency is set to 50Hz: In case
the frequency would drop to 46Hz, the actual current measurement would be 460A. An error of 40A
would be measured in the system.
Events
The VMEM function generates events from the status changes of various activities. To main event
buffer is possible to select status “On” or “Off” messages.
Table. 5.4.22. - 173. Event codes of the VMEM function.
Event Number
Event channel
Event block name
Event Code
Description
12160
190
M1VT1
0
Voltage memory enabled
12161
190
M1VT1
1
Voltage memory disabled
12162
190
M1VT1
2
Voltage low detected On
12163
190
M1VT1
3
Voltage low detected Off
12164
190
M1VT1
4
Current high detected On
12165
190
M1VT1
5
Current high detected Off
12166
190
M1VT1
6
Frequency tracked from CT On
12167
190
M1VT1
7
Frequency tracked from CT Off
12168
190
M1VT1
8
Using Voltage memory On
12169
190
M1VT1
9
Using Voltage memory Off
12170
190
M1VT1
10
Voltage memory blocked On
12171
190
M1VT1
11
Voltage memory blocked Off
5.4.23. Arc fault protection IArc>/I0Arc>(50Arc/50NArc)
Arc faults occur because of insulation failure, incorrect operation of the protected device, corrosion,
overvoltage, dirt, moisture, incorrect wiring or even because of aging caused by electric load. To
minimize the effects of an arc fault it’s important to detect the arc as fast as possible. Using arc sensors
to detect arc faults is much faster than merely measuring currents and voltages. In busbar protection
using just the normal protection IEDs could be too slow to disconnect arcs under safe time. For
example, when setting up overcurrent protection relay controlling the feeder breakers operation time
could be necessary to delay for hundreds of milliseconds after sensing the fault to achieve selectivity.
This delay can be avoided by using arc protection. To extent the speed of arc protection operation arc
protection card has high speed output as well to give tripping signal faster.
AQ-F255
Instruction manual
Version: 2.00
185
© Arcteq Relays Ltd