ABB RELION REX640, Техническое руководство, Страница: 607 / 1960

Figure 346: Permissible time-touch voltage characteristics given in standard
IEEE80 (metal-to-metal contact)
• This operation mode can be also used when maximum allowed earth potential
rise vs. operation speed follows a relationship such as 750 V/√
t[sec].
• Time margin for practical circuit-breaker operate time can be applied with
setting
CB delay Comp. Default setting 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. It is important to set setting
EF
current Str Val according to required protection sensitivity.
•
OPERATE
and
OP_EF
-outputs are activated so that the operate time is according
to the touch voltage requirements defined in standard IEEE80. 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outputs are reset immediately i.e. reset delay time is no
longer valid.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 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, IEEE
multiplier, Maximum earthing Ris, IDMT stage Min Op Tm, IDMT stage Max Op
Tm, Reset delay time.
According to the standard IEEE80, the values of the permissible touch voltage
U
Tp
as a function of the fault duration
t
f
are defined as follows:
For body weight of 50kg:
(Equation 122)
1MRS759142 F Protection functions
REX640
Technical Manual
607