ABB REB670 Applications Manual page 249

1MRK 505 337-UUS -
Application manual
Setting chapter in the application manual explains how the analog input needs to be
set.
3. The IED is fed from a single voltage transformer connected to the neutral point of a
power transformer in the power system. In this connection the protection is fed by the
voltage VN=V0 (single input). The Setting chapter in the application manual explains
how the analog input needs to be set. ROV2PTOV (59N) will measure the residual
voltage corresponding nominal phase-to-ground voltage for a high impedance
grounded system. The measurement will be based on the neutral voltage
displacement.
The below described setting parameters are identical for the two steps (n = step 1 and 2).
Therefore the setting parameters are described only once.
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
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, 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.
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.
3
Section 8
Voltage protection
(Equation 78)
243