Hitachi Relion 670 Series Applications Manual page 164

Section 9
Voltage protection
and operation for phase-to-phase voltage over:
Vpickup
EQUATION1992-ANSI V1 EN-US
The below described setting parameters are identical for the two steps (n = 1 or 2). Therefore the setting
parameters are described only once.
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. Therefore a tuning parameter CrvSatn is set
to compensate for this phenomenon. In the voltage interval Pickup> up to Pickup> · (1.0 + CrvSatn/100)
the used voltage will be: Pickup> · (1.0 + CrvSatn/100). If the programmable curve is used, this
parameter must be calculated so that:
CrvSatn
×
B
100
EQUATION1448 V1 EN-US
158
> ×
(%) VBase(kV)
- >
C 0
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1MRK511407-UUS Rev. N
(Equation 85)
(Equation 86)
Phasor measurement unit RES670
Application manual