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OPERATE and OP_EF outputs are reset immediately i.e. reset delay time is no
longer valid.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
To Next Page
Loading...
