ABB RELION 670 Series Technical Manual page 882

Section 14
Control
DB1, transformers with positive voltage deviation, V
the calculated no-load voltage for T3, although above DB1, would not be considered in this case.
Thus in the example above, the calculated no-load voltage for T3, although above DB1, would not
be considered for tapping in this case.
It is possible to avoid simultaneous tapping, and to distribute tapping actions evenly among the
parallel transformers in a busbar group. This is a selected by a setting parameter, and the
algorithm in the TR8ATCC (90) function will then select the transformer with the greatest voltage
deviation V
greatest value of V
delay t2, and so on. This is made possible as the calculation of I
measured values are exchanged on the horizontal communication (every 300 ms). If two
transformers have equal magnitude of V
one is going to tap first.
Logic diagrams
AUTO
V
L
V1 INNER DB
V2 INNER DB
V1 DB
V2 DB
V
B
V MAX
FSD
ANSI06000509 V1 EN-US
Figure 465: Simplified logic for automatic control in single mode operation
876
to tap first that is, after time delay t1. Thereafter, the transformer with the then
di
amongst the remaining transformers in the group will tap after a further time
di
a
a<b
<
b
a
a>b
>
b
a
a<b
<
b
a
a>b
>
b
a
a>b
>
b
, are disregarded. Thus in the example above,
di
, then there is a predetermined order governing which
di
AND
AND
OR
OR
AND
1MRK 502 066-UUS B
is updated every time the
cc
AND
VRAISE
OR
VLOWER
AND
en06000509_ansi.vsd
Technical manual
SEMOD158887-166 v1