Electric and Magnetic Field Calculator
This calculation tool is intended to assist with the derivation of electric and magnetic fields associated with overhead and underground transmission lines.
The tool provides the user with the field resulting from balanced three-phase circuits, where the phase conductors are defined by their coordinate positions.
Input Parameters
The calculation methodology for electric field does not explicitly include the influence of overhead shielding wires as these generally have a negligible effect at ground level. Moreover, the calculations also assume that the power frequency voltages are balanced and that the conductors are parallel to the ground. In all cases, the coordinates should refer to the centre of the conductor or conductor bundle, which is generally applied using the mid-span clearances. If more than one conductor is used in each phase, the diameter of the conductor bundle must also be specified. This is the effective diameter of the circle which intersects with the centre of each conductor.
The magnetic field calculations assume there is no zero sequence current flowing in the line, the phase currents are balanced and there are no harmonics. Circulating currents in the earthing systems are also not included in this calculation, which means that that values at easement boundaries may be slightly underestimated for overhead lines. These errors may often be compensated by using minimum mid-span clearances for overhead lines as the mid-span magnetic field is a function of the conductor clearances along the line and the use of mid-span coordinates is more conservative than the use of finite methods. Single core underground cables should be modelled by entering the coordinates for the centre of the cables. The backfill is assumed to have a magnetic permeability of unity, which may be slightly affected by large quantities of steel reinforcing. In all cases, the coordinates should refer to the centre of the conductor or conductor bundle, while all phase currents are assumed to flow in the same direction and to be in phase.
Circuit 1:
Circuit 2:
Terms of Use
This package is intended to provide assistance with common transmission line calculations. By using this tool you acknowledge that you understand how the calculations are derived and the potential limitations of the calculation methodology. In performing this calculation you are agreeing not to hold WeatheRate (or any of its associates) responsible for any liability, loss or harm associated with the use of these calculated variables.
Calculation Results
References
[1] EPRI, “Transmission Line Reference Book 345kV and Above” revised 2nd edition, EL-2500 1987, pp329-419[2] AS 1531—1991, Conductors—Bare overhead—Aluminium and aluminium alloy
[3] AS 1746—1991, Conductors—Bare overhead— Hard-drawn copper
[4] AS 3607—1989, Conductors—Bare overhead,aluminium and aluminium alloy—Steel reinforced