Electric Circuit of an Electrical Installation


The term ‘electric circuit of an electrical installation’ is officially defined within the IEC 60050-826-2022 as:

arrangement of devices or media through which electric current is intended to flow.

IEC 60050-826-2022

In another part of the International Electrotechnical Dictionary (in IEC 60050-466) defines the term “circuit of an overhead line”:

a conductor or system of conductors through which an electric current is intended to flow.

IEC 60050-466:1990/AMD3:2021

In IEC 60050-601 the term “circuit in electric power systems” is defined as follows:

electric line, or part of it, which can be taken out of service, automatically or manually, by circuit breakers or switches, independently of the other portions of the line.

IEC 60050-601:1985/AMD2:2020

IEC 60050-151 defined the term “electrical circuit” as follows:

arrangement of devices, media, or both, forming one or more conductive paths and where these devices and media can have capacitive coupling and inductive coupling. NOTE – The term “electric circuit” is defined as a mathematical model in IEC 60050-131.

IEC 60050-151:2001/AMD5:2021

The British Standard BS 7671 defined the term “circuit” as follows:

An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

BS 7671:2018+A2:2022


The definitions of “electric circuit” in IEC 60050-131, IEC 60050-151, IEC 60050-411 and IEC 60050-702 are strongly theoretical in that they were originally developed for use in electrical circuit theory as well as for electrical and magnetic devices. However, they successfully reflect the main purpose of an electric circuit – to form a path for the flow of electric current from conductive parts or a conductive media.

For international regulatory documentation covering low-voltage electrical installations, it is advisable to define the term “electrical circuit” in such a way that it generalizes all types of electrical circuits used in low-voltage electrical installations. The definitions given in IEC 60050-601 and BS 7671 are deficient. They refer only to circuits that are protected against short circuits and overloads by overcurrent protection devices. However, there may be electrical circuits in the electrical installations of buildings that must not be protected against overcurrents.

Moreover, in the electrical installations of buildings and buildings there are electrical circuits formed by protective conductors and bonding conductors connected to earthing arrangements or isolated from earth. No switching devices of any kind may be used in these electrical circuits.

Therefore, when defining an electrical circuit, firstly, we should say that it is a collection of electrical equipment connected to each other. Secondly, it is necessary to reflect the fact that the connected electrical equipment forms a conductive path for the flow of electric current.


Any electrical installation of a building consists of several parts, which include interconnected electrical equipment grouped together to perform specific functions. The term “electrical circuit” is used in international standards as well as in some national regulations to identify these parts of the electrical installation of a building, which can function independently of each other.

At the electrical circuit level, overcurrent protection is usually provided in the electrical installation of a building, as well as protection against electric shock, e.g. through a protection measure such as an automatic disconnection of the power supply.

The characteristics of electrical equipment combined in an electrical circuit must be consistent with each other. For example, the rated current of an electric stove must not exceed the allowable continuous current-carrying capacity of the cable supplying it. The rated current of the circuit breaker or fuse protecting this cable from overcurrent may not be greater than its continuous current-carrying capacity and less than the rated current of the electric stove.


The following electrical circuits are usually formed in the electrical installations of residential buildings:

  • Lighting circuits, consisting of light fixtures, cables and wires, protective devices, and other electrical equipment;
  • socket-outlet circuits consisting of plugs, cables and wires, protective devices, and other electrical equipment;
  • circuits of electric stoves, washing machines, air conditioners, electric boilers, electric pumps, heating cables, etc.
Final electric circuits
Example circuit diagram with electrical circuits

According to their purpose and function, all electrical circuits in the electrical installation of a building are divided into two groups: electrical distribution circuits and final electrical circuits.

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