For medium and high voltage circuit breakers used in switchgear or substations and generating stations, relatively few standard frame sizes are generally manufactured. These circuit breakers are usually controlled by separate protective relay systems, offering adjustable tripping current and time settings as well as allowing for more complex protection schemes. Thermal magnetic circuit breakers, which are the type found in most distribution boards in Europe and countries with a similar wiring arrangements, incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-current conditions. The thermal portion of the circuit breaker provides a time response feature, that trips the circuit breaker sooner for larger over currents but allows smaller overloads to persist for a longer time. This allows short current spikes such as are produced when a motor or other non-resistive load is switched on. With very large over-currents during a short circuit, the magnetic element trips the circuit breaker with no intentional additional delay. [7] Magnetic-hydraulic [ edit ]

Circuit breakers are also rated by the maximum fault current that they can interrupt; this allows use of more economical devices on systems unlikely to develop the high short-circuit current found on, for example, a large commercial building distribution system. Miniature circuit breakers used to protect control circuits or small appliances may not have sufficient interrupting capacity to use at a panel board; these circuit breakers are called "supplemental circuit protectors" to distinguish them from distribution-type circuit breakers. Switzerland: ABB breaks new ground with environment friendly high-voltage circuit breaker". Archived from the original on 24 December 2019 . Retrieved 7 June 2013.Gas (usually sulfur hexafluoride) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the sulfur hexafluoride (SF 6) to quench the stretched arc.

Many classifications of circuit breakers can be made, based on their features such as voltage class, construction type, interrupting type, and structural features. Air circuit breakers—Rated current up to 6,300 A and higher for generator circuit breakers. Trip characteristics are often fully adjustable including configurable trip thresholds and delays. Usually electronically controlled, though some models are microprocessor controlled via an integral electronic trip unit. Often used for main power distribution in large industrial plant, where the breakers are arranged in draw-out enclosures for ease of maintenance.

kV Disconnecting Circuit Breaker with FOCS: Small, smart and flexible, p.1". Archived from the original on 11 May 2020 . Retrieved 3 July 2013.