Setting Guidelines - ABB REC670 Applications Manual

Section 15
Scheme communication
15.3.3
478
This logic enables fast fault clearing during certain conditions, but naturally, it can not
fully replace a teleprotection scheme.
The logic can be controlled either by the autorecloser (zone extension) or by the loss-
of-load current (loss-of-load acceleration).
The loss-of-load acceleration gives selected overreach zone permission to operate
instantaneously after check of the different current criteria. It can not operate for three-
phase faults.

Setting guidelines

The parameters for the local acceleration logic functions are set via the local HMI or
PCM600.
Set ZoneExtension to Enabled when the first trip from selected overreaching zone shall
be instantaneous and the definitive trip after autoreclosure a normal time-delayed trip.
Set LossOfLoad to Enabled when the acceleration shall be controlled by loss-of-load in
healthy phase(s).
LoadCurr must be set below the current that will flow on the healthy phase when one
or two of the other phases are faulty and the breaker has opened at remote end (three-
phase). Calculate the setting according to equation 127.
×
0.5 I
Load
min
=
LoadCurr
I
Base
EQUATION1320 V1 EN-US
where:
ILoadmin is the minimum load current on the line during normal operation conditions.
The timer tLoadOn is used to increase the security of the loss-of-load function for
example to avoid unwanted release due to transient inrush current when energizing the
line power transformer. The loss-of-load function will be released after the timer
tLoadOn has elapsed at the same time as the load current in all three phases are above
the setting LoadCurr. In normal acceleration applications there is no need for delaying
the release, so set the tLoadOn to zero.
The drop-out timer tLoadOff is used to determine the window for the current release
conditions for Loss-of-load. The timer is by default set to 300ms, which is judged to be
enough to secure the current release.
1MRK 511 401-UUS A
M13854-4 v3
(Equation 127)
Bay control REC670 2.2 ANSI
Application manual