The combination of interrupter switches for switching and fuses for protection eliminates the need for expensive circuit-breaker gear (metal-clad switchgear), particularly on cable distribution systems where the rare and permanent nature of the faults makes the automatic reclosing feature of circuit-breakers an unnecessary extravagance. Unlike circuit-breaker gear, Custom Metal-Enclosed Switchgear is virtually maintenance free. The interrupter switches never need adjusting, setting, or dielectric testing. Only an occasional inspection and exercising is required. And the maintenance-proof fuses, unlike relays, never need setting or testing. With metal-enclosed switchgear, there are no batteries requiring special facilities and monitoring. The simplicity of metal-enclosed switchgear, its exceptional dependability, its low first cost, and its minimal maintenance cost make it the best choice for your system.

Custom Metal-Enclosed Switchgear is ideal for:

• Complex automatic source-transfer schemes, with three or more incoming power sources; multiple split-bus sections; or ring-bus arrangements.
• Applications with hot-sequence metering.
• Applications with special installation requirements, such as transformer primary unit substations, and those requiring special-purpose components such as grounding switches, control power transformers, metering panels, or capacitors for power-factor correction.
• Applications requiring unusual switchgear layouts, such as “U-shaped” configurations.

Custom Metal-Enclosed Switchgear features:

• Rugged 11-gauge steel enclosures.
• 600- and 1200-ampere load switches with duty-cycle fault-closing ratings.
• One-cycle minimum total clearing of fault currents with S&C SM and SML Power Fuses.
• Choice of unique response curves with S&C Fault Fiter® Electronic Power Fuses.
• Sophisticated, pre-engineered automatic source-transfer controls.
• Three-phase load protection. S&C open-phase detection relays and overcurrent relays isolate three-phase loads from single-phasing and other open-phase conditions.
• Single-phase load protection. Fuses, unlike circuit breakers, selectively isolate only faulted phases of feeders serving single-phase loads.
• Low purchase cost compared to metal-clad gear.
• Light weight. Easier to handle than metal-clad gear.

60-Hz Ratings ♠

♠ The ratings shown here are for individual bays. The rating for the entire assembly is the same as the lowest rated bay.

♥ Rating based on 4.16 kV refill. Rating is 27 000 for a 7.2 kV refill.

♦ The Max rating is reduced to 27 kV if using fuse types SM-4Z, SM-20, or SM-5S.

♣ Rating is 12 500 on solidly grounded circuit with single-conductor concentric neutral cable or bus connection to transformer.

NA  Not applicable.

Arc-Resistant Metal-Enclosed Switchgear is readily configured in circuit arrangements that make power system planning and design easy. The basic arrangements shown here are often combined to handle even the most complex distribution system needs. Other circuit designs are possible to fit specific needs.

Switches and Fuses

• Mini-Rupter® Switch — rated through 600 amperes continuous and interrupting.
• Alduti-Rupter® Switch — rated through 1200 amperes continuous and interrupting are also available.
• Type SM-40 Power Fuse — rated 400 amperes max continuous. Other SM Power Fuses are available in ratings from 200 through 720 amperes max continuous. Fuses are offered in a wide variety of time-current characteristics for optimal coordination and maximum protection. Time-current characteristics are precise and permanently accurate.
• Fault Fiter® Electronic Power Fuses — rated through 600 amperes max continuous. They have exceptional TCC versatility and higher continuous current ratings than previously available in fuses.

Switch Operators and Controls

• Type MS Switch Operators provide high-speed automatic trip-open operation of Mini-Rupter® Switches . . . interrupting time is 4 cycles. Type MS operators are available in a choice of manual or automatic trip-closed operation.
• Micro-AT® Source-Transfer Control minimizes interruptions resulting from the loss of one source . . . transfer is achieved in as little as 20 to 25 cycles. Available with a wide choice of options.
• Type ZSD Overcurrent Relays, applied on individual load feeders, protect three-phase loads from single-phasing caused by blown fuses. Superior to ordinary overcurrent relays, it can distinguish between fault current and transformer magnetizing inrush current.

Also available:

• AS-30 Switch Operators for Alduti-Rupter switches.
• Open-Phase Detectors – Type SPD for protection of three-phase load circuits from open phase conditions.

Combines the rugged features of Custom Metal-Enclosed Switchgear with additional measures needed to withstand the effects of internal arcing faults.

The enhanced design has successfully passed the rigorous certification testing required by Canadian Standard EEMAC G14.1. This standard addresses the effects of internal arcing fault conditions, including overpressure acting on covers, doors, and inspection windows. It also covers the thermal effects of the arc and verification that the arc does not burn through external walls of the enclosure.

Available in ratings 4.16 kV through 34.5 kV, this switchgear is built for long life and ease of operation.

Ratings of Currently Available Arc-Resistant Switchgear Bays

See Photo Sheet 620-700 for more information.