ABB RET650 Applications Manual page 161

1MRK 504 169-UEN A
Transformer protection RET650 2.2 IEC
Application manual
example, in the case of the protection of a transformer that might be overexcited.
The time delay must be co-ordinated with other automated actions in the system.
tResetn: Reset time for step n if definite time delay is used, given in s. The default
value is 25 ms.
tnMin: Minimum operation time for inverse time characteristic for step n, given in
s. For very high voltages the overvoltage function, using inverse time
characteristic, can give very short operation time. This might lead to unselective
trip. By setting t1Min longer than the operation time for other protections such
unselective tripping can be avoided.
ResetTypeCrvn: Set reset type curve for step n. This parameter can be set:
Instantaneous,Frozen time,Linearly decreased. The default setting is
Instantaneous.
tIResetn: Reset time for step n if inverse time delay is used, given in s. The default
value is 25 ms.
kn: Time multiplier for inverse time characteristic. This parameter is used for co-
ordination between different inverse time delayed undervoltage protections.
ACrvn, BCrvn, CCrvn, DCrvn, PCrvn: Parameters for step n, to set to create
programmable undervoltage inverse time characteristic. Description of this can be
found in the technical reference manual.
CrvSatn: Set tuning parameter for step n. When the denominator in the expression
of the programmable curve is equal to zero, the time delay will be infinite. There
will be an undesired discontinuity. Therefore, a tuning parameter CrvSatn is set to
compensate for this phenomenon. In the voltage interval U> up to U> · (1.0 +
CrvSatn/100) the used voltage will be: U> · (1.0 + CrvSatn/100). If the
programmable curve is used this parameter must be calculated so that:
CrvSatn
× - >
B C 0
100
EQUATION1448 V1 EN-US
HystAbsn: Absolute hysteresis for step n, set in % of UBase. The setting of this
parameter is highly dependent of the application. The hysteresis is used to avoid
oscillations of the START output signal. This signal resets when the measured
voltage drops below the setting level and leaves the hysteresis area. Make sure that
the set value for parameter HystABSn is somewhat smaller than the set pickup
value. Otherwise there is a risk that step n will not reset properly.
Section 8
Voltage protection
(Equation 39)
155