ABB REC670 Applications Manual page 259

1MRK 511 401-UUS A
Bay control REC670 2.2 ANSI
Application manual
ROV2PTOV (59N) will measure the residual voltage corresponding to the nominal
phase-to-ground voltage for a high-impedance grounded system. The measurement will
be based on the neutral voltage displacement.
The setting parameters described below are identical for the two steps (n = step 1 and
2). Therefore the setting parameters are described only once.
OperationStepn: This is to enable/disable operation of step n.
Characteristicn: Selected inverse time characteristic for step n. This parameter gives
the type of time delay to be used. The setting can be, Definite time or Inverse curve A
or Inverse curve B or Inverse curve C or Prog. inv. curve. The choice is highly
dependent of the protection application.
Pickupn: Set operate overvoltage operation value for step n, given as % of residual
voltage corresponding to VBase:
( ) ( )
> ×
V % VBase kV
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 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.
3
Section 9
Voltage protection
(Equation 94)
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