# IEC 60375-2018 pdf free download

**IEC 60375**-2018 pdf free download.Conventions concerning electric circuits.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

lEG 60617, Graphical symbols for diagrams I

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

ISO and lEG maintain terminological databases for use in standardization at the following addresses:

• lEG Electropedia: available at http://www.electropedia.org/

• ISO Online browsing platform: available at http://www.iso.org/obp

3.1 orientation

<of a curve> property of a curve described by the position vector r(u) which is associated with increasing or decreasing values of the parameter u

(SOURCE: IEC 60050-102:2007, 102-04-19]

3.2 orientation

<of a surface> for a surface having a tangent plane at any point, property determined by the choice, continuously from point to point, of one of the two normal unit vectors at each point

(SOURCE: lEG 60050-102:2007, 102-04-36. modified — Note ito entry omitted.]

3.3 electric charge

additive scalar quantity. associated with elementary particles and with macroscopic matter that characterizes their electromagnetic interactions

4 Orientation of geometrical objects

4.1 Orientation of a curve

An arbitrary orientation can be assigned to every curve. That orientation is usually indicated by an arrow. It applies to curves from a point “a” to another point “b” (see Figure 1a) and also to closed curves (see Figure 1b).

4.2 Orientation of a surface

The parts of surfaces generally considered in mathematical physics have two sides. One can give them an arbitrary orientation. That orientation is usually indicated by an arrow. This

applies to surfaces limited by a curve and also to closed surfaces. In the case of closed surfaces, the direction is normally taken as being away from the enclosed three-dimensional domain (see Figure 2).

The orientation of the surface delimited by a closed curve is generally related to the orientation of the curve such that, at any point of the curve, the vector line element defining the orientation of the curve, the unit vector normal to the surface defining its orientation, and the unit vector normal to these two vectors and oriented towards the exterior of the curve, form a right-handed trihedron.

4.3 Arrows perpendicular to the plane of the figure

It is evident that one cannot read the direction of arrows that are perpendicular to the plane of the figure. For that reason, two additional symbols have to be defined. An arrow directed away from the observer is represented by a small circle with a cross ® (U+2A02). An arrow directed to the observer is represented by a small circle with a dot 0 (U+2A00).

5 Conventions concerning currents

5.1 Physical direction of current

The net flow of electric charge through a surface is referred to as electric current. By convention, the physical direction of the current i is defined as the direction corresponding to the movement of positive charge. If the quasi-infinitesimal charge dq passes through a predetermined surface, for example the cross-section of a conductor, during the duration di the electric current is

NOTE The direction of electric Current in metallic conductors corresponds to the opposite direction of the net flow of free carriers of negative electric charge transferred from one terminal to another terminal.

5.2 Reference direction of current

The reference direction for the current in a branch or in a mesh is a direction fixed arbitrarily along the branch or around the mesh. A current is taken positively or negatively in equations according to whether its physical direction corresponds or not to the reference direction.

5.3 Indication of the reference direction for currents

5.3.1 Indication of the reference direction for currents for a branch

In a diagram, the orientation of a branch is indicated by an arrow. This arrow can be placed on the curve (see Figures 3a and 3b), or near the curve that represents the conductor of the branch (see Figure 3c) or near the branch (see Fi9ure 3d).IEC 60375 pdf free download.