Application - ABB REC670 Applications Manual

Section 8
Current protection
8.15.2
228

Application

Shunt capacitor banks (SCBs) are somewhat specific and different from other power
system elements. These specific features of SCB are briefly summarized in this section.
A capacitor unit is the building block used for SCB construction. The capacitor unit is
made up of individual capacitor elements, arranged in parallel or series connections.
Capacitor elements normally consist of aluminum foil, paper, or film-insulated cells
immersed in a biodegradable insulating fluid and are sealed in a metallic container. The
internal discharge resistor is also integrated within the capacitor unit in order to reduce
trapped residual voltage after disconnection of the SCB from the power system. Units
are available in a variety of voltage ratings (240V to 25kV) and sizes (2.5kVAr to
about 1000kVAr). Capacitor unit can be designed with one or two bushings.
The high-voltage SCB is normally constructed using individual capacitor units
connected in series and/or parallel to obtain the required voltage and MVAr rating.
Typically the neighboring capacitor units are mounted in racks. Each rack must be
insulated from the other by insulators because the can casing within each rack are at a
certain potential. Refer figure 92 for an example:
1MRK 511 401-UUS A
GUID-5EC8BAEC-9118-49EC-970C-43D6C416640A v1
GUID-BACAE67B-E64B-4963-B323-ECB0B69031B9 v2
Bay control REC670 2.2 ANSI
Application manual