Settings For Two Step Residual Overvoltage Protection - ABB Relion REC670 Applications Manual

Section 8
Voltage protection
IEC07000189 V1 EN-US
Figure 80: Earth fault in Direct earthed system
8.3.3.6

Settings for Two step residual overvoltage protection

Operation : Off or On
UBase (given in GlobalBaseSel ) is used as voltage reference for the voltage. 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). The 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
UN=U0 (single input). The Setting chapter in the application manual explains how the
analog input needs to be set. ROV2PTOV will measure the residual voltage corresponding
nominal phase-to-earth voltage for a high impedance earthed system. The measurement
will be based on the neutral voltage displacement.
The below described setting parameters are identical for the two steps (
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,
Inverse curve C or Prog. inv. curve . The choice is highly dependent of the protection
or
application.
Un> : Set operate overvoltage operation value for step n , given as % of residual voltage
corresponding to
184
UBase =Uph-ph.
UBase :
Definite time or Inverse curve A or Inverse curve B
1MRK 511 358-UEN A
M13853-21 v12
n = step 1 and 2).
Application manual