ABB RELION RET670, Applications Manual

Page: 630 / 1016

10.3.3.5 Direct grounded system
GUID-EA622F55-7978-4D1C-9AF7-2BAB5628070A v8
In direct grounded systems, an ground fault on one phase is indicated by voltage
collapse in that phase. The other healthy phase will still have normal phase-to-ground
voltage. The residual sum will have the same value as the remaining phase-to-ground
voltage, which is shown in Figure
296 .
V
_A
V_B
V_
C
V
_A
F
IL
1
F
V_B
V
_C
3V
0
ANSI07000189-1-en.vsd
ANSI07000189 V1 EN-US
Figure 296: Ground fault in Direct grounded system
10.3.3.6 Settings for two step residual overvoltage protection
M13853-21 v13
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
0
(single input). Section Analog inputs in the Application
manual explains how the analog input needs to be set.
Section 10
1MRK 504 163-UUS A
Voltage protection
624 Transformer protection RET670 2.2 ANSI
Application manual