| 1 | Applicable IEC standard | IEC 60947-2 covers circuit-breakers within the scope of low-voltage switchgear and controlgear. | IEC 62271-100 covers alternating-current circuit-breakers within the scope of high-voltage switchgear and controlgear. | Check the exact standard edition and product certification stated in the technical documentation. |
| 2 | Voltage range context | Low-voltage systems commonly operate at rated voltages up to 1,000 V AC or 1,500 V DC, subject to the applicable product standard and device rating. | IEC 62271 equipment is for systems above 1 kV; IEC 62271-100 addresses AC circuit-breakers. | Confirm rated voltage, system voltage, insulation level, and whether the application is AC or DC. |
| 3 | Typical installation | Distribution boards, motor control centres, and low-voltage switchboards. | Substations, transmission networks, and high-voltage switchgear assemblies. | Assess enclosure, mounting, indoor or outdoor service, and the installation environment. |
| 4 | Current rating | Rated current is selected for the protected circuit and the breaker’s declared operating conditions. | Rated normal current is selected for the power-system load and equipment design. | Compare the declared rating with load, conductor, busbar, and temperature-rise requirements. |
| 5 | Fault interruption | Breaking-capacity ratings indicate the fault-current level the breaker can interrupt under specified conditions. | Rated short-circuit breaking current and related performance ratings are important for network fault duties. | Verify the prospective fault current at the installation point and the applicable test ratings. |
| 6 | Short-time withstand | Coordination may require the breaker to withstand fault current for a specified short duration. | Short-time withstand current and duration are key parameters for switchgear and protection coordination. | Check withstand ratings against the protection clearing time and system study. |
| 7 | Operating mechanism | Manual, motor-operated, or stored-energy mechanisms may be available depending on breaker design. | Operating mechanisms are designed to perform switching operations at the rated conditions of the equipment. | Review operating duty, control supply, mechanical endurance, and maintenance requirements. |
| 8 | Protection and control | Electronic or thermal-magnetic trip units can provide overcurrent protection, depending on the product. | Protection and control functions are commonly coordinated with external relays and substation control systems. | Confirm protection settings, trip interfaces, communications, and compatibility with the protection scheme. |
| 9 | Environmental conditions | Ambient temperature, enclosure, altitude, and pollution conditions may affect ratings and selection. | Outdoor exposure, temperature, altitude, seismic conditions, and site pollution may affect equipment selection. | Check declared service conditions and any required derating or special design provisions. |
| 10 | Evidence for comparison | Useful evidence includes datasheets, type-test information, trip-unit details, and installation instructions. | Useful evidence includes rated-performance data, type-test documentation, operating-duty information, and maintenance instructions. | Compare verified technical documentation rather than relying on a manufacturer ranking alone. |