Wiring Diagram on Lightning Protection System for Primary Service

[EEAOC]

I am looking for wiring diagram as from a lightning protection system designer's view point that starts from lightning terminal on the roof then go through the lightning arrester, connects to the primary of the service transformer then to the system or building ground. The transformer can be either pole mounted or on the ground.

I am trying to resolve an issue that has to do with lightning damaging on transformer that is either pole mounted or on the ground. There was a case that the pole mounted transformer was moved from the pole to under ground, still there was some surge seen by the transformer and the lightning arrester was opened.

In order to analyze this, I need to see the entire wiring from point A to point B. This is something I could not find by searching the web

Thank you in advance.

 

[jghrist]

Lightning terminals are not directly connected to lightning arresters. They are connected to a lightning grounding electrode. Lightning arresters are grounded to the power grounding electrode. The lightning and power grounding electrodes are bonded together.

 

[busbar]

 
Some guidance might be found in §6 ‘Protection of distribution systems’ of IEEE standard C62.22-1997 …Application of Metal-Oxide Surge Arresters for Alternating-Current Systems The material is descriptive in nature with minimal illustrations. It is a for-fee publication.

C62.22-1997 descriptive informaion at:

http://shop.ieee.org/ieeestore/Product.aspx?product_no=SS94593

http://ieeexplore.ieee.org/xpl/tocresult.jsp?isNumber=15094

http://standards.ieee.org/reading/ieee/std_public/description/surge/C62.22-1997_desc.html

 

[mc5w]

There is also the NFPA Lightning Protection Handbook ( or is it Code? ) that gives you a lot of useful tips.

Every underground feed transformer needs its own lightning arrestor particularly at the end of the cable. When a lightning voltage pulse reaches the end of an underground line it will bounce off of and open switch or transformer winding and the voltage at that point is doubled. This will happen even if a transformer winding is connected phase to ground.

Lightning protection is only as good as the ground. An 8 foot or 10 foot ground sometimes NOT good enough particularly during a drought. A drought is also a prime time for clear weather lightning which occurs when the winds aloft are moving in 2 different directions essentially creating a sidways Van de Graff generator. Coupled with dry ground rods clear weather lightning is very destructive.

Winter lightning is even more destructive because the clouds are closer to the ground which magnifies the available current not to mention that winter lightning oftentimes has a reverse polarity which allows higher voltage to build up.

A cable plant person at Ohio Bell (now SBC) had to repair damage to our wire pair and 2 others even though we did not hear any lightning during the last storm. He told us that 97% of cable damage comes from lightning that is silent or even invisible. He also told us that when one that you see and hear does strike there are about 100 side strikes over a 100 yard radius. Lightning does not just seek the easiest path to ground, it seeks every path to ground that it can find.

If you need to sink a ground rod or pipe very deep into the ground there are 2 companies named Borit and Borzit who make a hand held drilling machine to which you attach a water hose and an air drill. This works for small scale boring underneath sidewalks and driveways in soil that only has some ricks in it. You can also use it in appropriate soil to sink a shallow water well or a 1.25 inch pipe ground. Calculate your budget on the basis that you may have to leave the drill bit at the bottom of the ground rod.

This also brings to mind that a lot of older transmission tower and station grounds are rotten enough that you have the Cross Your Fingers Method of lightning protection.

Mike Cole, mc5w@earthlink.net