The autoreclose logic can be set to block the SEF trip after a prescribed number of shots (set in AUTORECLOSE
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.
SEF ANY START LOGIC
Figure 59: SEF Any Start Logic
EPATR B CURVE
The EPATR B curve is commonly used for time-delayed Sensitive Earth Fault protection in certain markets. This
curve 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:
ISEF = 0.5A to 6.0A
ISEF = 6.0A to 200A
ISEF above 200A
where TMS (time multiplier setting) is 0.025 - 1.2 in steps of 0.025.
Primary Current Range Based on 100A:1A CT Ratio
Chapter 6 - Current Protection Functions
t = 432 x TMS/ISEF 0.655 secs
t = 800 x TMS/ISEF secs
t = 4 x TMS secs
Start ISEF >