WebNIR

Definition of the structure of conductor systems

Number of systems

Type of voltage Three-phase alternating Single-phase alternating Continue

Position of the calculation points along the ground plane

Initial distance m

Step m

Number of points

Altitude above ground m

Terrain slope °

Elaborate Reset JSON

Defining structures

The tool allows you to define up to 10 conductor systems, i.e. overhead power lines, each consisting of 1 to 30 straight, horizontal, parallel to each other and to the ground and undefined conductors.

The voltage frequency must be the same in all conductors. The user must indicate whether this is Three-phase AC, Single-phase AC or Continuous. In any case, the voltage value associated with each conductor must be referred to earth; if the nominal voltage between 2 phases is known, it must be divided by sqrt(3), an operation that is performed automatically by selecting Three-phase alternating and using a predefined support type present in the archive (see below).

As an example, the voltages referred to the ground for typical values are:

• 76.210 kV for voltage between conductors equal to 132 kV
• 86.603 kV for voltage between conductors equal to 150 kV
• 127.017 kV for voltage between conductors equal to 220 kV
• 219.393 kV for voltage between conductors equal to 380 kV

If the user selects Single-phase alternating voltage or Continue, using the predefined pylon types the field relating to the voltage value must be populated manually.

To place the conductors in the space, the relative structure must be positioned absolutely. To this end, it is necessary to specify:

• the altitude above the ground of the lowest conductor;
• the distance (measured along the ground, which may be inclined) of the foot of the perpendicular conducted for the origin of the internal reference system of the structure, from the origin of the absolute reference system (placed at ground level).

The following images show the absolute reference systems (in black) and the structures (in blue) in the cases of flat and inclined ground (click to enlarge):

Definition of conductors

Each conductor system is characterized by a structure that documents its geometric characteristics, with reference to the calculation plane (the vertical plane, orthogonal to the direction of the conductors, on which the points are located where the electric field will be calculated). We will call traces the points where the conductors intersect the calculation plane. The structure must be designed with its own internal orthogonal Cartesian reference system having:

• origin at a conventional point of the calculation plane, located vertically at the level of the track of the lowest conductor and horizontally along the axis of the support;
• horizontal X-axis directed towards the right;
• vertical Y-axis directed upwards.

The following images show the internal reference system (in blue) for an asymmetrical pylon with three conductors and a symmetrical one with six (click to enlarge):

In addition to the altitude above the ground of the lowest conductor and the horizontal positioning, in the case of multiple subconductors it is necessary to indicate whether the geometric parameter reported for each conductor indicates the radius of the circumference around which the subconductors are arranged, or the distance between two of them.

For three voltage values ​​(132 kV, 220 kV and 380 kV) the user can optionally select one of two predefined structures (single and double triplet respectively), chosen as the most impactful in their category from the point of view of the dispersed magnetic field. Alternatively, you can define your own custom structure, specifying the number of conductors and, for each of them:

• the coordinates of the suspension points, expressed in the internal reference system of the structure;
• the type of conductor (phase or guard wire);
• the voltage referred to earth;
• the phase;
• the radius;
• the number of subconductors;
• the radius of the circumference containing the subconductors, or the distance between two of them.

The data relating to a structure can be replicated in another, specifying the progressive number in the wording Replicate these parameters to structure n. ... and pressing the button with the green arrow.

Definition of the calculation points and the field value

Finally, the parameters needed to perform the calculation of the electric field along a segment lying on the calculation plane and parallel to the ground (hereinafter calculation segment) must be specified:

• slope of the ground
• initial distance (distance, measured along the ground, of the foot of the perpendicular drawn for the initial point of the calculation segment, from the origin - necessarily placed at ground level - of the absolute reference system)
• number of points into which to divide the calculation segment
• advancement step along the calculation segment
• constant height of the calculation segment on the ground

The results are shown in a graph; some summary data are summarized in tabular form.