The autoreclose logic can be set to block the SEF trip after a prescribed number of shots (set in AUT
ORECLOSE
column). This is achieved using the AR Blk Main Prot setting. This can also be blocked by the relevant timer block
signal ISEF>(n)TimerBlk DDB signal.
SEF protection can follow the same IDMT characteristics as described in the Overcurrent Protection Principles
section. Please refer to this section for details of IDMT characteristics.
11.3 SEF ANY START LOGIC
1
V02006
ISEF>1 Start
ISEF>2 Start
ISEF>3 Start
ISEF>4 Start
Start ISEF >
Figure 59: SEF Any Start Logic
11.4 EPATR B CURVE
The EPATR B curve is commonly used for time-delayed Sensitive Earth Fault protection in certain markets. This
curv
e is only available in the Sensitive Earth Fault protection stages 1 and 2. It is based on primary current settings,
employing a SEF CT ratio of 100:1 A.
The EPATR_B curve has 3 separate segments defined in terms of the primary current. It is defined as follows:
Segment Primary Current Range Based on 100A:1A CT Ratio Current/Time Characteristic
1 ISEF = 0.5A to 6.0A t = 432 x TMS/ISEF 0.655 secs
2 ISEF = 6.0A to 200A t = 800 x TMS/ISEF secs
3 ISEF above 200A t = 4 x TMS secs
where TMS (time multiplier setting) is 0.025 - 1.2 in steps of 0.025.
P14x Chapter 6 - Current Protection Functions
P14xEd1-TM-EN-1 131
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