Lightning Protection

Lighting mast or lighting rod is designed to protect a structure by providing a direct path to ground.

A surge arrestor is designed to protect electrical equipment by limiting the amount of current that can pass through it.

Dear Sir,

Thank you for your answer.

Regards,

T.Kailash Kumar

Hello kailasamvv

ozzb has answered your first question.

Transmission Line Lightning Protection - General:

The transmission line towers would normally be higher than a substation structure, unless you have a multi-storey structure at your substation.

Earth Mats are essential in all substation areas, along with driven earth electrodes (unless in a dry sandy desert site).

It is likewise normal to run catenary (aerial earth conductors) for at least 1kM out from all substation structures. Those earth wires to be properly electrically to each supporting transmission tower, and bonded back to the substation earth system.

It is important to have the catenary earth conductors above the power conductor lines, at a sufficient distance and position that a lightning strike will not hit the power conductors.

In some cases it is thus an advantage to have two catenary earth conductors, one each side of the transmission tower as they protect the power lines below in a better manner.

In lightning-prone areas it is often necessary to have catenary earthing along the full distance of the transmission line.

Without specifics, (and you could not presently give tower pictures in a Post because of a CR4 Server graphics upload problem), specifics would include:

1. Location
2. Country
3. Site soil type and resistivity
   
4. Number of Lightning Days
5. Expected Voltage + Current of a local lightning strike
6. Other - Advise please.

Structure Lightning Protection - General:

At the Substation, it is normal to have vertical electrodes bonded to the structure, and projecting up from the highest points of the structure, with the location and number of those electrodes to be sufficient that if a lightning strike arrived, it would always be a vertical earthed electrode which would be struck, rather than any electrical equipment.

In some older outdoor substation structures, air-break isolator switches are often at a very high point in the structure, and in those cases small structure extension towers are installed, with electrodes at the tapered peak of those extension towers.

The extension towers are normally 600mm square approximately until the extension tower changes shape at the tapered peak, and in some cases project upwards from the general structure 2 to 6 metres, with the electrode some 2 to 3 metres projecting upwards from the top of the extension tower.

The substation normally has a Lightning Counter - which registers a strike on the structure or connected catenary earth conductors, and the gathering of that information (Lightning Days, number per Day/Month/Year, Amperage of each strike) gives the Engineering Staff good statistics for future substation design.

Kind Regards....

Hello Mr.SPARK,

Excellent Answer. Thank you. Actually, In India, from my knowledge, 400 KV Lines are protected by ground wires which run above the power coductors. But in my area, 220 Kv lines don't have any ground wires. Also, in my 220 KV substation, the lightning mast tower is more height than the 220 KV transmission line tower. Is it good? Kindly clarify.

Thank You.

Regards,

T.Kailash Kumar