ABB RELION RET670, Applications Manual

Page: 639 / 1016

10.5.2 Application
SEMOD153893-5 v3
The Voltage differential protection VDCPTOV (60) functions can be used in some
different applications.
• Voltage unbalance protection for capacitor banks. The voltage on the bus is
supervised with the voltage in the capacitor bank, phase- by phase. Difference
indicates a fault, either short-circuited or open element in the capacitor bank. It is
mainly used on elements with external fuses but can also be used on elements with
internal fuses instead of a current unbalance protection measuring the current
between the neutrals of two half’s of the capacitor bank. The function requires
voltage transformers in all phases of the capacitor bank. Figure
299 shows some
different alternative connections of this function.
Vd>L1
Ph B Ph C
V1
V2
Vd>A
Ph B Ph C
V1 V2
Ph C
Ph B
en06000390_ansi.vsd
Single grounded wye
Double wye
ANSI06000390 V1 EN-US
Figure 299: Connection of voltage differential protection VDCPTOV (60) function to
detect unbalance in capacitor banks (one phase only is shown)
VDCPTOV (60) function has a block input (BLOCK) where a fuse failure supervision
(or MCB tripped) can be connected to prevent problems if one fuse in the capacitor
bank voltage transformer set has opened and not the other (capacitor voltage is
connected to input V2). It will also ensure that a fuse failure alarm is given instead of a
Undervoltage or Differential voltage alarm and/or tripping.
1MRK 504 163-UUS A
Section 10
Voltage protection
Transformer protection RET670 2.2 ANSI 633
Application manual