ABB RELION RER670, Applications Manual

Page: 208 / 506

9.3.3.1 High impedance earthed systems
M13853-18 v10
In high impedance earthed systems, an earth fault on one phase will cause a voltage
collapse in that phase. However, the other healthy phase voltage will raise to full
phase-to-phase voltage value. The residual voltage sum 2U
0
will raise to the same
phase-to-phase value during earth fault.
9.3.3.2 Solidly earthed systems
GUID-EA622F55-7978-4D1C-9AF7-2BAB5628070A v8
In solidly 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 2U
0
will have the same value as the remaining phase-to-
earth voltage.
9.3.3.3 Settings for two step residual overvoltage protection
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Parameters for ROV2PTOV application function are set via the local HMI or
Protection and Control Manager PCM600.
Common base IED values for primary current ( IBase ), primary voltage ( UBase )
and primary power ( SBase ) are set in the global base values for settings function
GBASVAL.
GlobalBaseSel : This is used to select GBASVAL function for reference of base
values.
Operation : This is used for residual overvoltage protection Off / On .
UBase (given in GlobalBaseSel ) is used as voltage reference for the set pickup
values. UBase shall be set equal to rated phase-to-phase voltage. Note that the set
value for UBase will be multiplied by factor 0.5 within the ROV2PTOV function.
The voltage can be fed to the IED in different ways:
1. The IED is fed from two VTs connected phase-to-ground, where the residual
voltage 2U
0
is calculated internally within the protection.
2. 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
0
(single input). Section Analog inputs in the
Application manual explains how the analog input needs to be set.
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.
Un> : Set operate overvoltage operation value for step n , given as % of residual
voltage corresponding to UBase :
(%) ( ) / 2 Un UBase kV
 
IECEQUATION050 V2 EN-US
(Equation 66)
Section 9
1MRK 506 375-UEN A
Voltage protection
202 Railway application RER670 2.2 IEC
Application manual