Operation time can be either definite time or inverse time, selected with setting
Operating curve type = “Definite time”, “Inverse time EN50522” or “Inverse time
IEEE80”.
When
Operating curve type = “Definite time” is selected, then
• Operate time is according to definite time (DT) operation.
•
START
and
ST_EF
outputs are activated when estimated touch voltage
(considering the effect of settings
Reduction factor and Enable harmonics)
exceeds setting
Touch Vol 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
Touch Vol Str Val
according to required protection sensitivity.
•
OPERATE
and
OP_EF
outputs are activated after
Operation timer has elapsed,
defined with setting
DT stage Op time.
• 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outputs are reset immediately i.e. reset delay time is no
longer valid.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, in case 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, thus definite operation is ineffective
during re-striking/intermittent earth faults. 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, Maximum earthing Ris, Touch Vol Str
Val, DT stage Op time, Reset delay time.
• Note that setting
CB Delay Comp (circuit breaker delay compensation) is not
applicable in definite time operation.
Consider next the following example:
Example 4. Setting
Touch Vol Str Val = 40 V and DT stage Op time = 400 ms.
IFPTOC starts when estimated touch voltage exceeds 40 V and operates after 400
ms, if start conditions are met. Maximum earthing resistance value encountered
in the protected feeder is set to be 10 ohms (setting
Maximum earthing Ris) and
Reduction factor = 1. For illustrating possible operating speed requirements of
protection, limits of touch and earth potential rise durations defined in standard
EN50522 are shown for reference.
Protection functions
1MRS759142 F
612
REX640
Technical Manual