Lightning Rod System

[mto12345]

Good morning
Due to surge issues/lightning strikes that caused sever damage to the this electrical system (one line below), the client is asking for a lightning rod system. Can someone please give me the pros and cons of introducing a lightning rod to this design. Also roughly how much would it cost and what does the design look like (capture device, down conductors (sizes?), grounding rod etc) . Thanks. this there any other thing i can introduce into this design to mitigate sever surge issues (bigger grounding conductors? etc)

 

[EC Dan]

Lightning rods are for personnel and structural protection, not equipment. Their purpose is to create a zone of protection within a radius of the lightning rod, in which lightning is more likely to be channeled through the rod to ground than to a person or through combustible building material such as wood. Lightning protection design a highly specialized field, and most of the time there are a limited amount of companies that can engineer this type of system properly. Lightning arrestors / surge protectors are for equipment protection.

 

[mto12345]

Lightning rods are for personnel and structural protection, not equipment. Their purpose is to create a zone of protection within a radius of the lightning rod, in which lightning is more likely to be channeled through the rod to ground than to a person or through combustible building material such as wood. Lightning protection design a highly specialized field, and most of the time there are a limited amount of companies that can engineer this type of system properly. Lightning arrestors / surge protectors are for equipment protection.

Thanks EC Dan, it so happens the places I am having issues are in Florida, I think the issues arises after severe weather conditions. Is there any other thing i can introduce into this design to mitigate severe surge issues. I already have SPD, and adequate grounding represented…..but I need so kind of solutions to booster my design.

 

[jaggedben]

If you want an LPS hire a professional. I do not believe this forum is going to give you accurate and productive advice. Doing it wrong could make things worse.

If you don't want to pay for a professional then my advice is to stay away from lightning rods and install the biggest surge protectors the client wants to pay for.

 

[winnie]

I concur with @jaggedben . If you really want a lightning protection system you need to hire a professional skilled in LPS design. As an engineer working with facilities in lightning prone areas, you might consider the various training courses (offered by UL among others) in LPS design. And yes, doing a system wrong can very much make things worse.

I am _not_ an LPS professional. However something worth exploring in the facility being discussed is the possibility that you have multiple grounding electrodes which are individually bonded to equipment, rather than being bonded together directly. This can have the counterproductive effect of causing 'earth current' from nearby strikes to enter the equipment at one electrode and exit via a separate electrode.

-Jon

 

[Engser18]

1. You should look into NFPA 780. it is depend on the structure height and area of cover. if you want to protect E-equipment (if they are inside the bldg) then SPD would do the jobs. However, the spd(s) would need frequent visual inspection (at least 1/yr and after the thunderstorm whenever come first). if you want to protect the bldg structure, then complete LPS would be provided. there are few option/type for LPS and the cost will depend on the type of LPS you installed.
2. Your SPD shall be located at SD not at the MDP. However, you can cascade SPD to protected E-equipment. I would put additional SPD at Panel CW and CW-B

Other comments on your single line diagram:
1. you need to show grounding electrode system at SD, not at MDP.
2. No need to run 2/0 G from meter cabinet to SD.
3. using 2-200A panels on the secondary side of 75 KVA, it doesn't meet NEC table 450.3(B) note 2.

 

[EC Dan]

Thanks EC Dan, it so happens the places I am having issues are in Florida, I think the issues arises after severe weather conditions. Is there any other thing i can introduce into this design to mitigate severe surge issues. I already have SPD, and adequate grounding represented…..but I need so kind of solutions to booster my design.

What exactly was damaged by lightning in the past at this facility? At the very least I would add SPDs to both 208V panels. I will say we used to have significant issues with lightning at this facility. Some of the equipment damaged were a 100 HP VFD, numerous analog input modules, switches, and a generator controller. We had a LPS specialist come out and evaluate our grounding and lightning protection, and their findings were basically that we should stick lightning rods on every roof and decrease the resistance of a few grounding rods that were above 25 Ohms. Not super helpful in solving equipment damage from lightning. I solved (so far at least) the analog input module issue by putting optical isolators on the more problematic analog input circuits (ie. ones that ran for significant length outdoors to the top of a metal tank) and adding a line reactor to the 100 HP VFD.

 

[tom baker]

If you want an LPS hire a professional. I do not believe this forum is going to give you accurate and productive advice. Doing it wrong could make things worse.

If you don't want to pay for a professional then my advice is to stay away from lightning rods and install the biggest surge protectors the client wants to pay for.

Excellent advice. This is an area that requires a specialist.

 

[mto12345]

If you want an LPS hire a professional. I do not believe this forum is going to give you accurate and productive advice. Doing it wrong could make things worse.

If you don't want to pay for a professional then my advice is to stay away from lightning rods and install the biggest surge protectors the client wants to pay for.

thanks for the professional advise

 

[mto12345]

1. You should look into NFPA 780. it is depend on the structure height and area of cover. if you want to protect E-equipment (if they are inside the bldg) then SPD would do the jobs. However, the spd(s) would need frequent visual inspection (at least 1/yr and after the thunderstorm whenever come first). if you want to protect the bldg structure, then complete LPS would be provided. there are few option/type for LPS and the cost will depend on the type of LPS you installed.
2. Your SPD shall be located at SD not at the MDP. However, you can cascade SPD to protected E-equipment. I would put additional SPD at Panel CW and CW-B

Other comments on your single line diagram:
1. you need to show grounding electrode system at SD, not at MDP.
2. No need to run 2/0 G from meter cabinet to SD.
3. using 2-200A panels on the secondary side of 75 KVA, it doesn't meet NEC table 450.3(B) note 2.

Thank you so much, how does this look

 

[Engser18]

Is your MBJP at CT cabinet? if not the GEC should be removed.
2-200A panels, should change combine MCB up 300A (1-200MCB, 1-100A or 2-150A or etc). Otherwise it is violated NEC. Or you can increase XFromer to 112.5 KVA.

 

[mto12345]

Is your MBJP at CT cabinet? if not the GEC should be removed.
2-200A panels, should change combine MCB up 300A (1-200MCB, 1-100A or 2-150A or etc). Otherwise it is violated NEC. Or you can increase XFromer to 112.5 KVA.

You are right, The amperage on one of the panels usually stay below 100A.