ABB REC670 Applications Manual page 254

Section 9
Voltage protection
248
Characteristicn: This parameter gives the type of time delay to be used. The setting
can be Definite time, Inverse Curve A, Inverse Curve B, Inverse Curve C or I/Prog. inv.
curve. The choice is highly dependent of the protection application.
OpModen: This parameter describes how many of the three measured voltages that
should be above the set level to give operation. The setting can be 1 out of 3, 2 out of 3,
3 out of 3. In most applications it is sufficient that one phase voltage is high to give
operation. If the function shall be insensitive for single phase-to-ground faults 1 out of
3 can be chosen, because the voltage will normally rise in the non-faulted phases at
single phase-to-ground faults. In subtransmission and transmission networks the UV
function is mainly a system supervision function and 3 out of 3 is selected.
Pickupn: Set pickup overvoltage operation value for step n, given as % of VBase. The
setting is highly dependent of the protection application. Here it is essential to consider
the maximum voltage at non-faulted situations. Normally this voltage is less than 110%
of nominal voltage.
tn: time delay of step n, given in s. The setting is highly dependent of the protection
application. In many applications the protection function is used to prevent damages to
the protected object. The speed might be important for example in case of protection of
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: This parameter for inverse time characteristic 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.
TDn: 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 to set to create programmable under
voltage inverse time characteristic. Description of this can be found in the technical
reference manual.
CrvSatn: When the denominator in the expression of the programmable curve is equal
to zero the time delay will be infinity. There will be an undesired discontinuity.
1MRK 511 401-UUS A
Bay control REC670 2.2 ANSI
Application manual