ABB REC670 Applications Manual page 448

Section 14
Control
442
The second use is to detect a jammed tap changer. If the timer tTCTimeout times out
before the TCINPROG signal is set back to zero, the output signal TCERRAL is set
high and TR1ATCC (90) or TR8ATCC (90) function is blocked.
The third use is to check the proper operation of the tap changer mechanism. As soon
as the input signal TCINPROG is set back to zero TCMYLTC (84) or TCLYLTC (84)
function expects to read a new and correct value for the tap position. If this does not
happen the output signal CMDERRAL is set high and TR1ATCC (90) or TR8ATCC
(90) function is blocked. The fixed extension (g) 2 sec. of TCINPROG, is made to
prevent a situation where this could happen despite no real malfunction.
In figure 180, it can be noted that the fixed extension (c) 4 sec. of tPulseDur, is made
to prevent a situation with TCINPROG set high without the simultaneous presence of
an VRAISE or VLOWER command. If this would happen, TCMYLTC (84) or
TCLYLTC (84) would see this as a spontaneous TCINPROG signal without an
accompanying VRAISE or VLOWER command, and this would then lead to the
output signal TCERRAL being set high and TR1ATCC (90) or TR8ATCC (90)
function being blocked. Effectively this is then also a supervision of a run-away tap
situation.
Hunting detection
Hunting detection is provided in order to generate an alarm when the voltage control
gives an abnormal number of commands or abnormal sequence of commands within a
pre-defined period of time.
There are three hunting functions:
1. The Automatic voltage control for tap changer function, TR1ATCC (90) for single
control and TR8ATCC (90) for parallel control will activate the output signal
DAYHUNT when the number of tap changer operations exceed the number given
by the setting DayHuntDetect during the last 24 hours (sliding window). Active as
well in manual as in automatic mode.
2. TR1ATCC (90) or TR8ATCC (90) function will activate the output signal
HOURHUNT when the number of tap changer operations exceed the number
given by the setting HourHuntDetect during the last hour (sliding window). Active
as well in manual as in automatic mode.
3. TR1ATCC (90) or TR8ATCC (90) function will activate the output signal
HUNTING when the total number of contradictory tap changer operations
(RAISE, LOWER, RAISE, LOWER, and so on) exceeds the pre-set value given
by the setting NoOpWindow within the time sliding window specified via the
setting parameter tWindowHunt. Only active in automatic mode.
Hunting can be the result of a narrow deadband setting or some other abnormalities in
the control system.
1MRK 511 401-UUS A
SEMOD159053-361 v4
Bay control REC670 2.2 ANSI
Application manual