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Section 10
Voltage protection
10.3.3.7
452
Settings for two step residual overvoltage protection
Operation: Disabled or Enabled
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
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
%
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.
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
(single input). Section Analog inputs in the Application
0
3
1MRK 502 071-UUS A
M13853-21 v13
(Equation 240)
Application manual
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