Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Lightning protection

  • Please log in to reply
12 replies to this topic

#1 sberrada

sberrada

    Mariner 2

  • -----
  • topic starter
  • Posts: 237
  • Joined: 28 Aug 2011
  • Loc: Montreal, Quebec

Posted 14 June 2021 - 07:34 AM

Hi,

 

There was a heavy lightning storm yesterday in the area where my ROR observatory is located.

Fortunately there was no lightning strike, but i am wondering whether there is a need to install lightning protection ?

 

My ROR has a metal roof and is lower than my chalet which is about 50 feet away.

 

I would appreciate your thoughts / suggestions on this question.

 

thanks

Sam 

 



#2 MJB87

MJB87

    Gemini

  • *****
  • Moderators
  • Posts: 3,155
  • Joined: 17 Feb 2014
  • Loc: Talbot County, MD & Washington, DC

Posted 14 June 2021 - 08:35 AM

There are two worries here. The first is a direct strike on the observatory. The second is a nearby ground strike which sends a surge up through any metal cables (power, ethernet) that may be buried nearby.

 

The second problem can be solved relatively easily by disconnecting the breaker when you are not in the observatory. My ROR (metal roof) and adjacent dome operates four circuits, two of which I leave on all of the time (air conditioner, lighting, network) and two that I disconnect when I am not there (the two mounts/piers).  You can also install surge protectors on the circuits themselves. Finally, you should install surge protectors on any buried ethernet lines. I had a ground strike come up the buried Cat6 line and take out my LAN switch.

 

The first problem is more challenging.  A a minimum you might want to ground the structure so that lightning hitting the closed roof finds an easy way to the ground besides your pier/mount. Not sure what the regs are in Montreal but in general you need to bury a copper rod and tie it until a copper wire of sufficient gauge that links with the metal roof.

 

We considered adding lightning rods to the top of the observatory but in the decided against it. It would have expensive, it was hard to find a contractor willing to do such a small (for them) job, the rods would interfere with telescope views and the mechanics of fixing a lightning rod to a moving metal roof were complicated. Moreover, there are numerous tall trees in the general area and we thought the odds of a direct strike on the observatory were minimal.



#3 astrokeith

astrokeith

    Apollo

  • -----
  • Posts: 1,105
  • Joined: 14 Mar 2010
  • Loc: Surrey, UK

Posted 14 June 2021 - 08:43 AM

Protecting the building is a big job. You have your chalet nearby which could protect you. A simple approach is to imaging a 50m diameter sphere rolling over the area. Will it touch the ROR observatory? If not the lightning will 'likely' strike elsewhere. Grounding the metal observatory may invalidate this approach as a well earthed metal structure may be more 'attractive' to a discharge forming.

 

protecting cables is both more important and easier!



#4 Jethro7

Jethro7

    Vanguard

  • *****
  • Posts: 2,253
  • Joined: 17 Dec 2018
  • Loc: N.W. Florida

Posted 14 June 2021 - 08:47 AM

Hello Sam,

I live in the lightning capital of the U.S,A. here in Florida, the bottom line is, there is a few  things that can be done to help prevent the damage from lightning. You have to redirect the lightning's potential through the use of a lightning rod system and this system can be made fairly cheap. And the use of a isolation transformer placed between the power service and your observatory. Here is the caveat. You dont need to have a direct lightning strike to receive damage to electronics. Even close proximity strikes can produce a EMP that can find its way into your sensitive equipment through internal wiring in the device, even though nothing is directly plugged in. To help counter this, you need to ground your observatory essentially turning it into a Faraday cage to shunt the lightning's electrical potential to the ground away from your equipment.  The bottom line is these techniques greatly bring down the potential of lightning damage but sometimes lightning will find a way. 

 

HAPPY SKIES AND KEEP LOOKING UP Jethro


Edited by Jethro7, 14 June 2021 - 08:51 AM.


#5 sberrada

sberrada

    Mariner 2

  • -----
  • topic starter
  • Posts: 237
  • Joined: 28 Aug 2011
  • Loc: Montreal, Quebec

Posted 14 June 2021 - 11:21 PM

Hi,

 

i really appreciate the excellent advice.

I attached a drone view of the observatory - on the north is the chalet (50 feet away) which is higher, on the south are trees (also 50 feet away) which are higher than the observatory.  The east has tall trees about 100 feet away, whereas the west is open. Based on what I read these higher objects would reduce risk of direct strikes.

I don’t think that I will install a lighting rod / cable because of the complexity of attaching to the mobile metal roof.

i have all my imaging equipment (mount, camera, etc) connected to a UPS with surge protection so hopefully this would help.  
 

i think that I will need to protect the cat7 Ethernet cables running between the observatory and chalet (my computers are inside the chalet controlling the mounts / scopes).

 

Any further advice / thoughts would be appreciated 

 

cheers

sam

 

 

Drone view


#6 astrokeith

astrokeith

    Apollo

  • -----
  • Posts: 1,105
  • Joined: 14 Mar 2010
  • Loc: Surrey, UK

Posted 15 June 2021 - 01:50 AM

A great looking place! Nice.

 

I think your decisions are good and that cat7 just needs attention.


  • archer1960 likes this

#7 MJB87

MJB87

    Gemini

  • *****
  • Moderators
  • Posts: 3,155
  • Joined: 17 Feb 2014
  • Loc: Talbot County, MD & Washington, DC

Posted 15 June 2021 - 06:37 AM

Nice spot!

 

Your approach makes sense. Protect the electronics and data connections. Assume the trees and other structures divert lightning away from your observatory.

 

To be extra safe, disconnect the mount and pier from power when not in use (and thunderstorms are possible.) This is in addition to having an in-line surge protector.



#8 archer1960

archer1960

    Viking 1

  • *****
  • Posts: 854
  • Joined: 26 Jul 2011
  • Loc: Southern New England

Posted 16 June 2021 - 04:51 PM

Sounds like you have a sound plan. You might consider replacing your cat7 cable with fiber, which would completely eliminate the chance of EMP-caused spikes. Just needs a media converter on each end, and you would be good to go.



#9 Christopher Erickson

Christopher Erickson

    Skylab

  • *****
  • Posts: 4,040
  • Joined: 08 May 2006
  • Loc: Waikoloa Village, Hawaii

Posted 16 June 2021 - 05:51 PM

There are four different fundamental types of grounding. And a number of subdivisions.

 

1. Electrical grounding for fire and electrocution protection. The NEC, the (USA) National Electrical Code.

2. Lightning protection grounding. The Motorola R-56 Specification. MUCH more stringent than the NEC.

3. Signal propagation grounding. The ARRL reference libraries.

4. ESD protection grounding. IEEE standards for ESD mitigation and protection of electronics.

 

Each type of grounding is likely important to your observatory. Even Signal grounding.

 

The NEC has almost no considerations whatsoever for lightning, signal or ESD grounding.

 

Electricians are NOT trained on lightning, signal and ESD grounding. Most are not aware that there are four different types-of and purposes-for grounding.

 

A Telecommunications Engineer is the MOST qualified expert to correctly advise you on proper observatory grounding.

 

The Motorola R-56 specification is the best place for an observatory user start.

 

To add to the R-56:

 

1. Use fiber optic connectivity wherever possible. Especially between buildings and structures.

2. Install a ground ring around your observatory and tie your pier and everything else metal into it.

3. Build your observatory into a six-sided Faraday Cage, if you can. The bottom side is the most important.

4. Use Exothermal (CadWeld, etc.) bonding on all ground rod and ground ring connections. 

5. Replaceable copper brushes can be used to connect metal roofs to the vertical grounding conductors.

6. The goal of your grounding is to shunt external electrical charge surges outside and around your observatory to ground, and not through your observatory.

7. Learn what a GPR (ground Potential Rise) is and understand how it is the most likely thing that will destroy stuff in your observatory.

8. Put a Transtector (or similar device) on the outside of your observatory and interconnected structures where the power entrance is made.

9. Put Polyphasers (or similar devices) on the outside of your observatory and interconnected structures where all conductive communications entrances are made.

 

Most important of all, be suspicious of ALL grounding advice you read on the Internet. There is a whole-lot of BAD and DANGEROUS advice out there. Find a local electrical engineer or telecommunications engineer to advise you. Show them this post and have them comment about it.

 

I hope this helps.

 

 

Hi,

 

There was a heavy lightning storm yesterday in the area where my ROR observatory is located.

Fortunately there was no lightning strike, but i am wondering whether there is a need to install lightning protection ?

 

My ROR has a metal roof and is lower than my chalet which is about 50 feet away.

 

I would appreciate your thoughts / suggestions on this question.

 

thanks

Sam 


  • RazvanUnderStars and speedster like this

#10 sberrada

sberrada

    Mariner 2

  • -----
  • topic starter
  • Posts: 237
  • Joined: 28 Aug 2011
  • Loc: Montreal, Quebec

Posted 17 June 2021 - 12:03 AM

Thank you so much Christopher, for such a detailed response.

Sounds much more elaborate than what I anticipated.

quite frankly I was hoping for something not too complex (likely due to my lack of knowledge).

 

In consideration of the risk-reward equation, If there was one or two simple things that could be done to get some protection, albeit not as good as R-56, what would you recommend (ie priority 1, 2, and 3)

 

cheers

Sam 



#11 Christopher Erickson

Christopher Erickson

    Skylab

  • *****
  • Posts: 4,040
  • Joined: 08 May 2006
  • Loc: Waikoloa Village, Hawaii

Posted 17 June 2021 - 01:47 AM

Quick and dirty things that will make a big difference...

Disconnect from commercial power. Or at least have a way where you can unplug power to the observatory, right at the observatory. And not just a simple disconnect or switch. A way to put a big air gap between the observatory power connection and the power feed. Like unplugging a big extension cord.

Disconnect all metallic communications between the observatory and any other structures.

Put a ground rod into the ground next to the power entrance of your observatory and exothermically bond it to your pier (if its a steel pier) and every other major metallic structure parts.

Read up on GPR.

#12 sberrada

sberrada

    Mariner 2

  • -----
  • topic starter
  • Posts: 237
  • Joined: 28 Aug 2011
  • Loc: Montreal, Quebec

Posted 18 June 2021 - 11:07 PM

Thanks Christopher, that is very helpful.

i appreciate your help 

 

Sam 



#13 Christopher Erickson

Christopher Erickson

    Skylab

  • *****
  • Posts: 4,040
  • Joined: 08 May 2006
  • Loc: Waikoloa Village, Hawaii

Posted 18 June 2021 - 11:23 PM

Glad to help.

And here are some reasonable links for GPR - Ground Potential Rise. NOT Ground Penetrating Radar. (LOL)

 

https://www.solution...ential-rise-gpr

 

https://electrical-e...-potential-rise

 

https://esgrounding....ntial-rise.html

 

https://en.wikipedia..._potential_rise

 

http://www.apscservi...-069-c_20_1.pdf




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics