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The function registers its operation into the last twelve (12) time-stamped registers; this information is
available for all provided instances separately. The register of the function records the ON event
process data for START, TRIP or BLOCKED. The table below presents the structure of the function's
register content.
Table. 5.3.6 - 94. Register content.
Register
Description
Event
Event name
Date and time
dd.mm.yyyy hh:mm:ss.mss
I
0
pre-triggering current
Start/Trip -20ms current
I
0
fault current
Start/Trip current
Fault capacitive I
0
Start/Trip capacitive current
Fault resistive I
0
Start/Trip resistive current
Fault U
0
(%)
Start/Trip voltage (percentage of nominal)
Fault U
0
(V)
Start/Trip voltage (in Volts)
I
0
fault angle
0...360°
Trip time remaining
0 ms...1800s
Used SG
Setting group 1...8 active
Network GND
Unearthed, Petersen coil earthed, Earthed network
I
0
pre-fault current
Start -200ms current
5.3.7 Intermittent earth fault protection (I0int>; 67NT)
The intermittent earth fault is a transient type of single-phase-to-earth fault where the actual fault
phenomenon lasts for about a few hundred microseconds. The intermittent earth fault is commonly
seen in Petersen coil grounded (compensated) medium voltage networks. The intermittent earth fault is
commonly thought only as a cable network problem but it can also occur in overhead line networks.
The key point for this type of fault appearance is the compensation of earth fault currents with a
Petersen coil.
This phenomenon is becoming more frequent as more utilities networks are replacing overhead lines
with cables dug into the ground. This development in distribution networks is very understandable
as overhead lines are more vulnerable to possible seasonal storm damages. Also, the annual
maintenance costs as well as the annual power-down time are both significantly lower with
underground cable networks than with overhead line networks. However, the problem at hand is
caused by the increasing amount of cabling in the network which in turn causes dramatic increases
in the capacitive earth fault currents in the distribution networks. When the capacitive earth fault
current increases in the network, it becomes necessary to detect the earth fault current with a
Petersen coil.
A
AQ
Q-C255
-C255
Instruction manual
Version: 2.06
© Arcteq Relays Ltd
IM00035
111