Designation of electrical circuits in diagrams
The designation of chain sections serves for their identification and may also reflect their functional purpose in electric circuit diagram... The requirements for marking schemes of schematic electrical circuits are determined by GOST 2.709-89.
According to this standard, all sections of electrical circuits separated by contacts of devices, relay coils, devices, machines, resistors and other elements must have a different designation.
Sections of circuits passing through detachable, collapsible or integral contact connections must have the same designations. If necessary, the standard allows sections of circuits passing through detachable contact connections to be assigned different designations.
In order to be able to distinguish sections of chains connected, for example, to different units, it is allowed to add sequential numbers and other designations accepted for units in the designation of chains, separating them with a dash.
Arabic numerals and uppercase letters of the Latin alphabet are used to designate sections of schematic electrical circuit diagrams. Numbers and letters included in the designation must be of the same font size.
The sequence of designations should be from the input of the power source to the consumer, and branched circuit sections are labeled from top to bottom in a left-to-right direction. The fulfillment of this requirement is clearly visible from the figures. In the process of marking chains, it is allowed to leave spare numbers.
Designation of electrical circuits in diagrams
When developing electrical circuits, the following order should be observed for designating individual sections of circuits:
1) AC circuits are labeled: L1, L2, L3 ... with the addition of consecutive numbers. For example, sections of the circuit of the first phase L1: L11, L12, etc.; sections of the circuit of the second phase L2: L21, L22, etc.; sections of the circuit of the third phase L3: L31, L32, etc.
It is allowed, if this does not cause a wrong connection, to designate the phases of alternating current circuits with the letters A, B, C.
3) control chain, protection, signaling, automation, measurements are indicated by consecutive numbers in the product or installation.
It is allowed in single-phase (phase — zero, phase — phase) AC circuits to designate sections of circuits with even and odd numbers.
As a rule, designations are placed on schematic electrical diagrams: with a horizontal arrangement of circuits — above the wire section, with a vertical arrangement of circuits — to the right of the wire section. In technically justified cases, it is allowed to place designations below the circuit image.
Instead of groups of numbers, the functional affiliation of the schemes of the schematic diagram can also be expressed with generally accepted letters.