View source for Location of protective devices

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A protective device is, in general, required at the origin of each circuit}}

== General rule  ==
(see {{FigRef|G7a}})

A protective device is necessary at the origin of each circuit where a reduction of permissible maximum current level occurs.

== Possible alternative locations in certain circumstances ==

(see {{FigRef|G7b}})

The protective device may be placed part way along the circuit: 
*If AB is not in proximity to combustible material, and 
*If no socket-outlets or branch connections are taken from AB

Three cases may be useful in practice: 
*Consider case (1) in the diagram
** AB ≤ 3 metres, and
** AB has been installed to reduce to a practical minimum the risk of a short-circuit (wires in heavy steel conduit for example) 
*Consider case (2)
**The upstream device P1 protects the length AB against short-circuits in accordance with the [[Calculation of minimum levels of short-circuit current ]]
*Consider case (3)
**The overload device (S) is located adjacent to the load. This arrangement is convenient for motor circuits. The device (S) constitutes the control (start/stop) and overload protection of the motor while (SC) is: either a circuit-breaker (designed for motor protection) or fuses type aM
**The short-circuit protection (SC) located at the origin of the circuit conforms with the principles of [[Calculation of minimum levels of short-circuit current ]].

== Circuits with no protection  ==
(see {{FigRef|G7c}})

Either 
*The protective device P1 is calibrated to protect the cable S2 against overloads and short-circuits
Or 
*Where the breaking of a circuit constitutes a risk, e.g.
** Excitation circuits of rotating machines 
** circuits of large lifting electromagnets 
** the secondary circuits of current transformers 

No circuit interruption can be tolerated, and the protection of the cabling is of secondary importance. 

{{Gallery|G7|Location of protective devices||
|DB422286a.svg|a|
|DB422286b_EN.svg|b|
|DB422286c_EN.svg|c|}}