ABB RELION REX640 Technical Manual page 547

1MRS759142 C
REX640
Technical Manual
supervision, and which is further defined with setting Operating quantity
(available options are "Adaptive", "Amplitude" and "Resistive").
The START output is activated once Start delay time has elapsed. OPERATE output is
activated once Operate delay time has elapsed and the above three conditions are
valid. Reset timer is started if any of the above three conditions is not valid. If the fault
is transient and self-extinguishes, START output stays activated until the reset timer
expires (setting Reset delay time). After OPERATE output activation, START and
OPERATE outputs are reset immediately if any of the above three conditions is not
valid. The start duration value START_DUR, available in the Monitored data view,
indicates the percentage ratio of the start time and the set operating time.
If detection of temporary earth faults is not desired, the activation of
START output can be delayed with setting Start delay time. The same
setting can also be used to avoid restarting of the function during long-
lasting post-fault oscillations if the time constant of post-fault
oscillations is very long (network losses and damping is low).
To keep the operate timer activated between current spikes during
intermittent or restriking earth faults, Reset delay time should be set
above the maximum expected time interval between fault spikes
(obtained at full resonance condition). The recommended value is at
least 300 ms.
Section 4
Protection functions
541