ABB Relion 670 Series Applications Manual page 231

1MRK 511 401-UUS F
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V %
ANSIEQUATION2290 V1 EN-US
The setting depends on the required sensitivity of the protection and the type of system
grounding. In non-effectively grounded systems, the residual voltage cannot be higher than three
times the rated phase-to-ground voltage, which should correspond to 100%.
In effectively grounded systems, this value depends on the ratio Z0/Z1. The required setting to
detect high resistive ground faults must be based on network calculations.
tn : time delay of step n , given in s. The setting is highly dependent on the protection application.
In many applications, the protection function has the task to prevent damage to the protected
object. The speed might be important, for 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
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.
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 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
In the voltage interval
CrvSatn /100). If the programmable curve is used this parameter must be calculated so that:
· (1.0 +
CrvSatn
×
B
100
EQUATION1448 V1 EN-US
HystAbsn: Absolute hysteresis for step n , set in % of VBase . The setting of this parameter is highly
dependent of the application. The hysteresis is used to avoid oscillations of the PICKUP 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
the set pickup value. Otherwise there is a risk that step n will not reset properly.
Bay control REC670
Application manual
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×
VBase kV 3
Pickup> up to Pickup> · (1.0 + CrvSatn /100) the used voltage will be: Pickup>
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C 0
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t1Min longer than the operation time for other
CrvSatn is set to compensate for this phenomenon.
HystABSn is somewhat smaller than
Section 9
Voltage protection
(Equation 99)
(Equation 100)
225