ABB RELION REX640 Technical Manual page 612

Protection functions
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
• 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
exceeds setting
current estimate is validated. Note that
not affect this start condition. It is important to set setting
according to required protection sensitivity.
• OPERATE and OP_EF outputs are activated after
defined with setting
• 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OPERATE and OP_EF outputs are reset immediately i.e. reset delay time is no
longer valid.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
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:
Val, DT stage Op time, Reset delay time .
• Note that setting
applicable in definite time operation.
Consider next the following example:
Example 4. Setting
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
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.
612
Operating curve type = "Definite time" is selected, then
Touch Vol Str Val and earth fault is detected and earth-fault
DT stage Op time .
Reduction factor, Maximum earthing Ris, Touch Vol Str
CB Delay Comp (circuit breaker delay compensation) is not
Touch Vol Str Val = 40 V and DT stage Op time = 400 ms.
Reduction factor and Enable harmonics )
Ena RF Compensation = "Enable" does
Operation timer has elapsed,
.
Maximum earthing Ris ) and
1MRS759142 F
Touch Vol Str Val
Reset delay time
REX640
Technical Manual