ABB Relion 650 Series Applications Manual page 110

Section 8
Voltage protection
Pickupn : Set overvoltage operate value for step n ( n =step 1 and 2), given as % of residual voltage
corresponding to global set parameter
( )
>
V %
ANSIEQUATION2290 V1 EN-US
The setting is dependent of the required sensitivity of the protection and the system grounding. In
non-effectively grounded systems the residual voltage can be maximum the rated phase-to-
ground voltage, which should correspond to 100%.
In effectively grounded systems this value is dependent of 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 ( n =step 1 and 2), given in s. The setting is highly dependent of the
protection application. In many applications, the protection function has the task 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.
t1Min : Minimum operate time for inverse time characteristic for step 1, 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.
TD1 : Time multiplier for inverse time characteristic. This parameter is used for co-ordination
between different inverse time delayed undervoltage protections.
104
( )
×
VBase kV 3
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VBase :
t1Min longer than the operation time for other
1MRK 505 287-UUS B
(Equation 22)
Busbar protection REB650
Application manual