Lightning Protection Calculator
This calculator determines the area protected by lightning protection equipment using the Rolling Sphere Method. The results show either the maximum distance for the lightning masts to be placed apart or the furthest distance for the equipment to be placed from the masts.
This is a simple calculator which uses empirical equations to solve for six (6) independent shielding cases which can be used in combination. For an automated and accurate approach you should use the Lightning Protection Module of SafeGrid Earthing Software.
1. Standalone Mast:
In this case, the equipment is being protected by one mast. The inputs are the height of the mast (H) and the height of the equipment to be protected (Y). The outputs are the maximum distance (Lmax) for the equipment to be placed in order to always be protected.
2. Two Lightning Masts:
In this case, the inputs are the heights of the masts (H & h), the height of equipment to be protected (Y) and the distance between the masts (L).
The calculator outputs the maximum possible distance between the masts (Lmax) so that the height Y can be the maximum height for the equipment to be protected anywhere between the masts (Ymax). If the user does not specify the distance, the calculator takes Lmax as the distance between the masts.
However, if Y is greater than Ymax and lower than both masts, the calculator displays Lmax, Ymax, the maximum distance for the equipment to be protected from the higher mast (L1) and the maximum distance for the equipment to be protected from the lower mast (L2).
If Y is greater than the lower mast, Lmax is not applicable, and a distance input field is mandatory. The calculator in this case outputs Ymax and L1.
Other outputs are:
LextH: the external protected area of the higher mast.
Lexth: the external protected area of the lower mast.
X: the minimum width of the protected area.
3. Mast and fence:
In this case, the user needs to input the heights of the mast and the fence (H & f), the height of equipment to be protected (Y) and the distance between the masts (L).
The calculator outputs the maximum possible distance between the masts (Lmax) so that the height Y can be the maximum height for the equipment to be protected anywhere between the mast and the fence (Ymax). If the user does not specify the distance, the calculator takes Lmax as the distance between the mast and the fence.
If Y is greater than the fence, Lmax would not be applicable, and a distance input field will be mandatory. The calculator in this case outputs Ymax and L.
4. Gantry Conductors:
The height of equipment (i.e. phase conductors) must not be higher than Ymax to be fully protected. The gantry posts are at the same height. The inputs are the gantry posts height (H) and the height of equipment to be protected (Y). If the distance between gantry posts (L) is specified, the calculator outputs Ymax and Lmax. If the distance between masts is not specified, the distance between the masts (Lmax) will be so that Y will be the required Ymax.
5. 3-Masts & 4-Masts:
The aim of these cases is to find the diameter (L) of the circumscribing circle of the three or four masts within which the equipment will be protected. The masts are all of the same height. The inputs are the height of the masts and the equipment height. The outputs are the diameter of the circle(L), (Lext) the external protected area and (X) the minimum width of the protected area.
Related Resources:
Earth Grid Conductor Size Calculator
This calculator determines the minimum earth grid conductor size based on the short-time temperature rise limit and is based on equation 37 (section 11.3.1) from IEEE Guide for Safety in AC Substation Grounding (IEEE Std. 80-2013).
Earthing Grid Resistance IEEE Std. 80 Calculator
This calculator produces the grid resistance within a substation based on several parameters such as total buried length of conductors, area occupied by ground grid and the depth of the grid.
Lightning Protection Software
Automatic lightning protection system design using the rolling sphere method.
As used by:
