The maximum prospective short circuit current is the maximum electrical current which can flow in a particular electrical system under short circuit conditions. It is determined by the voltage and impedance of the supply system. It is of the order of a few thousand amperes for a standard domestic mains electrical installation in the UK, but may be as low as a few milliamperes in a SELV (Safety Extra Low Voltage or, occasionally, Separated Extra Low Voltage) system or as high as hundreds of thousands of amps in large industrial power systems. In electricity, current refers to electric current, which is the flow of electric charge. ... For alternate meanings see Short circuit (disambiguation) A short circuit (sometimes known as simply a short) is a fault whereby electricity moves through a circuit in an unintended path, usually due to a connection forming where none was expected. ... This article may be too technical for most readers to understand. ... In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ... An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. ... The ampere (symbol: A) is the SI base unit of electric current equal to one coulomb per second. ... Type F Mains power plug & socket The term mains usually refers to the general purpose AC electrical power supply (as in Ive connected the appliance to the mains). The term is not usually used in the US and Canada, where it is known as household, or domestic power. ... The use of extra low voltage (ELV) in an electrical circuit is one of several means to provide protection against electrical shock. ...

It is of particular interest when designing an electrical installation because fuses and circuit breakers must be capable of safely breaking the flow of current in the event of a short circuit. When a large electrical current is interrupted an arc may form and if the breaking capacity of a fuse or circuit breaker is exceeded then it may not be able to extinguish this arc meaning that the flow of current will continue, possibly resulting in a fire or explosion. 200 A Industrial fuse. ... A circuit breaker is an automatically-operated electrical switch which is designed to protect an electrical circuit from damage caused by overload or short circuit. ... The term Arc is derived from the Latin word arcus meaning bow. Look up arc in Wiktionary, the free dictionary. ... It has been suggested that flame be merged into this article or section. ...

In domestical power installations in European countries (230V AC 50 HZ single phase power) the short circuit current available on the electrical outlets needs to be taken into account when designing electrical power wiring. The short circuit current should not be too high or too low. The effect of too high short circuit current is discussed on the previous chapter. The short circuit current should be of the order of around 200A or higher for normal 10A or 16A outlet to guarantee that the normal wire protecting fuse or breaker will quickly disconnect the supply in case of short circuit. Quick disconnecting is needed, because in live-ground short circuit the grounding potential on the power outlet can rise during short circuit to a dangerous voltage, which needs to be shut down quickly for safety. If the short circuit current is lower than, special precautions needs to be taken to make sure that the system is safe; those usually include using a residual current device for extra protection. The short circuit current available on the electrical outlets is often measured with a suitable instrument when examining electrical installations to make sure that the short circuit current is within reasonable limits. Having a high enough short circuit current on the outlet will also tell that the resistance from the electrical panel to the outlet is reasonably low, so there will not be too high voltage losses on the wires when outlets are loaded normally.