Lightning mast - design - 230 kv Substation

As per IEC 62305, the coverage of the lightning protection air termination system is dependent on the LPL (Lightning Protection Level). Also the IEC standard follows the concept of rolling sphere method for determining the coverage area. In case of LPL I the radius of the sphere is 20m, for LPL II it is 30m, for LPL III it is 45m and for LPL IV it is 60m.

The Minimum peak cureent of the lightning stroke defined by IEC for various levels is LPL I : 3kA; LPL II : 5kA; LPL III : 10kA and LPL IV : 16kA.

You need to know the LPL level to be considered for the location where the outdoor substation (switchyard) is proposed and use the required number of air termination units with corresponding sphere radius to cover the entire air.

Guest,

The LP Levels are decided based on the observed maximum and minimum values of lightning stroke currents. Note that the values of maximum current (First Short Storke) for various levels are LPL I : 200kA; LPL II : 150kA; LPL III : 100kA; LPL IV : 100kA. The values for minimum peak currents were indicated in previous post.

The mximum values are used to design the lightning protection components i.e. cross section of conductors, thickness of metal sheets, current capabilities of surge protection devices and separation distance to avoid sparking.

The minimum values are for deciding the radius of rolling sphere and hence the coverage area.

The LPL for a particular location is decided based on observed lightning currents over a period of time. This darta is mostly available from the meterological department.

Please note that the LP level has nothing to do with the voltage level of the installation.

Angle of protection depends on the Height of the mast(Hm) and Height of the highest structure(Hs) to be protected. For Hs>2/3 Hm the angle of protection is 30deg and for Hs<2/3 Hm the angle of protection is 45deg. Generally for a 220kV substation the max height of structure to be protected is around 17m. Considering this height to be protected, the angle of protection can be taken as 45Deg. Rough guess for number of LMs should be 8- 10 masts. For exact calculation you may refer "High Voltage Engineering" be Dr D V Razevig.

Lightning is a competitive event, so it's not a simple case of launching the highest possible means of collection. Given the right conditions lightning can still attach itself to a piece of eqpmnt under the 'mast' if you're not careful.

What part of the world is the sub located? This will have a bearing on lightning intensity and frequency, as well as the relevant 'local' standards that need to be considered.

As Current Maarey suggests the IEC does go into a bit of detail but not specifically for substation applications. If the sub is being designed/installed by ABB or Areva, they have their own specs on this.

Distances from ground plane to busbars, and from busbars to the 'mast/s' are important, you may not need to go as high as 50m, which may simplify things for you.

Let us know where the sub is (which country) and we'll go from there.

static wires can greatly decrease the number of masts.