ABB Relion 670 Series Applications Manual page 227

1MRK 511 401-UEN Rev. K
9.3.3.5 Direct earthed system
In direct earthed systems, an earth fault on one phase is indicated by voltage collapse in that
phase. The other healthy phase will still have normal phase-to-earth voltage. The residual sum
will have the same value as the remaining phase-to-earth voltage, which is shown in Figure 102.
IEC07000189 V2 EN-US
Figure 102: Earth fault in Direct earthed system
9.3.3.6 Settings for two step residual overvoltage protection
Operation : Off or On
UBase (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-earth voltages within the protection. The setting
of the analog input is given as
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 3U0 (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
UN=U
analog input needs to be set.
ROV2PTOV will measure the residual voltage corresponding to the nominal phase-to-earth
voltage for a high-impedance earthed system. The measurement will be based on the neutral
voltage displacement.
The setting parameters described below are identical for the two steps (
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,
Bay control REC670
Application manual
(single input). Section
0
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IEC07000189-2-en.vsd
UBase =Uph-ph.
Analog inputs in the Application manual explains how the
Definite time or Inverse curve A or Inverse curve B
Section 9
Voltage protection
GUID-EA622F55-7978-4D1C-9AF7-2BAB5628070A v8
M13853-21 v14
n = step 1 and 2).
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