Incoming Section | Metal Enclosed Capacitor Options for Industrial Market|
There are several different approaches and customer options for incoming sections, some of these are as follows.
•Bottom entrance with bus connections only. Typically this arrangement will have the bus bar vertically mounted and perpendicular to earth. A two-hole NEMA pad is used for 600-amp bus and a four-hole NEMA pad is used for 1200 amp bus. If not specified, the termination height will be approximately 16" from the bottom of the enclosure. Refer to Note 1 below.
•Incoming disconnect switch. This switch is a three-phase disconnect type switch. Even if the switch has load break capability it should
not be used to energize nor to de-energize the capacitor bank. Normally, a front operator is used. Side operated switches are available. Front operated switches are generally for industrial customers, or where public does not have access to the capacitor bank. Side operated switches are more difficult to make tamper resistant and there are times when this handle will need to be placed behind a pad lockable door. Refer to Note 2 below.
•Group fused incoming switch. This is sometimes used when up stream protection is not used. The problem with this device is that it only protects the bus-work in the enclosure. Individual capacitor fuses should be used to protect the faulted capacitor. The individual capacitor fuse should be properly co-coordinated with the group fuse and with the capacitor tank rupture curve. Sometimes, when only three capacitors are used in the bank, group fuses are used to protect from tank rupture. Refer to Note 3 below.
•Lightning arrester on the incoming. Distribution type surge arresters are most common. Intermediate and station type arresters are available. Refer to Note 3 below. Control power transformer (CPT), if required, will be placed in the section.
•Top entry can also be supplied in place of bottom entrance. Top entry into the enclosure can be supplied with roof bushings or with conduit connections. With a disconnect switch, additional bus-work will be required.
•NEC section 420-24 (b) (1)&(2) requires isolating means. This can be in the capacitor bank, in upstream switchgear, or drawout circuit breakers. They should also be interlocked so the isolation switch does not break the capacitor load.
•If fuse cutouts (or similar) are used and they cannot be interlocked, refer to NEC section 490-22. A prominent sign is to be displayed stating not to open this device under load.
•The best placement for main fuses, arresters, or other main bank protection would be at the "Point of Common Connection (PCC)." This will allow protection for the whole line from the PCC to the capacitor bank.