ABB RELION REX640 - Page 601

Figure 342: Permissible time-touch voltage characteristics given in standard EN
50522
• Time margin for practical circuit-breaker operate time can be applied with
setting CB delay Comp . Default time margin is 0 ms.
• START and ST_EF outputs are activated when estimated effective earth-fault
current magnitude (considering the effect of settings
Reduction factor and
Enable harmonics ) exceeds setting EF current Str Val and earth fault is detected,
and earth-fault current estimate is validated. Note that Ena RF Compensation =
“Enable” does not affect this start condition.
• OPERATE and OP_EF outputs are activated according to the operate time - touch
voltage and earth potential rise requirements defined in standard EN 50522. i.e.
operate time is inversely proportional to the estimated fault current.
• Reset timer is started if any of the above conditions for START is not anymore
valid. START and ST_EF outputs stay activated until the reset timer expires
(setting Reset delay time ). After OPERATE output activation, START, ST_EF,
OPERATE and OP_EF outputs are reset immediately i.e. reset delay time is no
longer valid. During re-striking/intermittent earth faults, the very high current
transient may result to very fast operation times. In case longer operation time
during re-striking/intermittent earth faults is preferred and operation should
be based preferably on counted number of transients, then setting Reset delay
time should be set to low value, say 20-40 ms. Dedicated intermittent earth-fault
protection functionality based on counted number of transients is described in
Chapter 4.2.10.5.6 Intermittent earth-fault protection .
• Applicable settings are: Reduction factor, EF current Str Val, CB delay Comp, UTp
multiplier, Maximum earthing Ris, IDMT stage Min Op Tm, IDMT stage Max Op
Tm, Reset delay time .
It is important to note, that:
1MRS759142 F
Protection functions
REX640
Technical Manual
601