ABB Relion 670 Series Applications Manual page 234

Section 8
Voltage protection
VBase (given in GlobalBaseSel) is used as voltage reference for the set pickup values. The voltage can
be fed to the IED in different ways:
1. The IED is fed from a normal voltage transformer group where the residual voltage is calculated
internally from the phase-to-ground voltages within the protection. The setting of the analogue input
is given as VBase=Vph-ph.
2. The IED is fed from a broken delta connection normal voltage transformer group. In an open delta
connection the protection is fed by the voltage 3V0 (single input). Section Analog inputs 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=V
(single input). Section Analog inputs in the Application manual explains how the analog input needs
to be set.
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 %
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.
228
( )
×
VBase kV 3
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1MRK 505 370-UUS Rev. K
0
(Equation 77)
Busbar protection REB670
Application manual