SynC · Topic
Circuit Breakers
These are the standards in SynC Standards that cover Circuit Breakers. Each one is a complete, plain-language specification: the scope it applies to, the requirements that govern it, and a structured equipment datasheet listing the values a project has to decide, with the standards each is verified against. All of it is written and maintained by SynC, free to read without an account, and published under CC BY 4.0.
A standard usually carries several topics, so most of the entries below also appear under neighbouring subjects. The topics each one carries are listed on its own page.
Standards
- Low Voltage Switchboards
Dead-front, floor-standing distribution switchboards rated 1000 V and below, listed to UL 891 and built to NEMA PB 2, in which molded-case or insulated-case circuit breakers, fusible switches, or bolted-pressure switches are group-mounted or individually mounted on a common bus, whether installed as service equipment or downstream of a transformer, switchgear, or another switchboard. Covers the ratings, the interrupting rating basis, the main and feeder devices and their trip units, the bus, the structure and enclosure, arc-flash mitigation, the service entrance, surge protection, metering and communications provisions built into the assembly, identification, factory and field testing, installation, warranty, and spares, for three-phase and single-phase AC systems in indoor and outdoor locations.
- Low Voltage Switchgear
Metal-enclosed low-voltage power circuit breaker switchgear rated 1000 V and below, listed to UL 1558 and built to IEEE C37.20.1, in which drawout low-voltage power circuit breakers built to IEEE C37.13 are individually mounted in grounded metal compartments on a common bus, whether installed as service equipment, as the secondary of a transformer, or downstream of other distribution equipment. Covers the ratings and the short-time basis, the breakers and their drawout mechanisms, operation, trip units, and accessories, ground-fault protection, arc energy reduction, control power and control wiring, the protective relays, instrument transformers, metering, surge protection, and communications provisions built into the assembly, the bus, the structure and enclosure, compartmentalization and arc-resistant construction, identification, factory and field testing, installation, warranty, spares, and breaker handling equipment, for three-phase and single-phase AC systems in indoor and outdoor locations, including walk-in and non-walk-in outdoor housings.
- Medium Voltage Switchgear
Metal-clad medium-voltage switchgear rated above 1 kV through 38 kV using drawout vacuum or SF6 circuit breakers, built to IEEE C37.20.2 and the ANSI/IEEE C37.04 / C37.06 / C37.09 series, for utility-customer substations, large commercial campuses, healthcare and higher-education central plants, data centers, and industrial facilities. Covers 5 kV, 15 kV, 27 kV, and 38 kV voltage classes, indoor and outdoor walk-in (protected aisle) configurations, arc-resistant ratings per IEEE C37.20.7, multifunction microprocessor protective relays, and optional IEC 61850 station bus communications.
- Protective Device Coordination Study
The time-current coordination study for a project's electrical power distribution system, from the utility's protective device at the point of delivery through every overcurrent protective device within the extent the datasheet selects, on AC systems rated 1000 V and below through 38 kV with utility, generator, inverter-based, and paralleled sources. Covers who performs the study and when it is delivered, the degree of coordination applied to normal distribution and the circuits on which NFPA 70 620.62, 645.27, 700.32, 701.32, 708.54, and 517.31(G) require selective coordination, the coordination time intervals and band separations, the curves of the utility device, transformers, motors, conductors, generators, and inverter-based sources that bound every setting, the coordination of ground-fault protection including the two levels NFPA 70 517.17 requires, the recommended setting of every trip unit, relay, fuse, and overload relay, the trade-off between selectivity and incident energy, the coordination deficiencies and who accepts them, the settings record handed to the field, the report, and the events that call for a re-study.