ABB Relion 670 Series Applications Manual page 254

Section 10
Unbalance protection
10.3 Phase voltage differential based capacitor bank
unbalanced protection, SCPDPTOV
10.3.1 Identification
Function description
Phase voltage differential
based capacitor bank
unbalanced protection
10.3.2 Application
Shunt capacitor banks can be used in both transmission and distribution networks, for
example by supporting reactive power flow, reducing line losses and improving the system
voltage profile. A high-voltage SCB is normally constructed using individual capacitor units
connected in series or in parallel to obtain the required voltage and MVAr rating.
A capacitor unit is the basic building block of the capacitor bank as shown in
unit is built by arranging a group of individual capacitor elements in series and parallel to each
other. These elements are connected to fuses and the element groups are shunted by an
internal discharging device (resistor). The capacitor bank units for high voltage application
incorporate different designs that include internal/external fused and fuse-less
configurations. The capacitor bank can be connected in either star single/double WYE or in H-
bridge and delta connections based on the reactive power requirement. The details of
capacitor bank type and connections are referred as per
Guide for the Protection of Shunt Capacitor Banks .
The capacitor units are designed based on the following specifications:
• Rated reactive power of the bank
• Rated voltage
• Rated frequency
The general faults in a shunt capacitor bank are open-circuit or short-circuit of capacitor
elements in a C
change the voltage distribution among the capacitor elements. The voltage distribution
among the capacitor elements should be equal because the rate of internal insulation
degradation is a highly non-linear function of the element voltage. The insulation degrades
rapidly with voltages greater than 110%.
248
IEC 61850
identification
SCPDPTOV
or C based on whether it is a fused or fuse-less SCB. These faults
unit group
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IEC 60617 identification ANSI/IEEE C37.2 device number
Ud>
IEEE Standard C37.99-2000, IEEE
1MRK 511 401-UEN Rev. K
GUID-662626C7-409B-4CE2-9DF0-A47A3A2FC5DF v1
GUID-9E095985-CC54-4BDE-8108-B10BBB5EE3EE v1
87V
GUID-63D381C5-9579-44C0-918A-7B26B7785C9A v1
Figure 118. This
Bay control REC670
Application manual