ABB REG670 Applications Manual page 585

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
In figure 292, 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 URAISE or ULOWER command. If this would happen, TCMYLTC or TCLYLTC
would see this as a spontaneous TCINPROG signal without an accompanying
URAISE or ULOWER command, and this would then lead to the output signal
TCERRAL being set high and TR1ATCC or TR8ATCC 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 for single
control and TR8ATCC 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 or TR8ATCC 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 or TR8ATCC 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.
Wearing of the tap changer contacts
Two counters, ContactLife and NoOfOperations are available within the Tap changer
control and supervision function, 6 binary inputs TCMYLTC or 32 binary inputs
TCLYLTC. They can be used as a guide for maintenance of the tap changer
mechanism. The ContactLife counter represents the remaining number of operations
(decremental counter) at rated load.
=
ContactLife ContactLife
n+1
EQUATION1873 V2 EN
where n is the number of operations and α is an adjustable setting parameter,
CLFactor, with default value is set to 2. With this default setting an operation at rated
load (current measured on HV-side) decrements the ContactLife counter with 1.
a
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I
load
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÷
ç ÷
n
I
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rated
Section 15
Control
(Equation 276)
579