debates over most important TVSS location

[eddie11]

Hi. A site I am working with is subject to a company spec that says only that commercial power line protection must be installed at or near the ATS.

The site is a telecom/data center hub. The building service main switchboard feeds into the standby generator ATS and from there into some UPSs before hitting the main distribution switchboard feeding the data center floor. There is no outside lightning protection system for the facility.

I interpreted the power line philosophy inherent in the quote I gave above to suggest that we must (and should) first put a TVSS on the load side of the first service disconnect for the commercial power service into the building. This approach is also consistent with what I thought was a general philospophy of keeping outside transients from getting into the building off the power line as a first step of protection.

As a secondary protection, I was still planning on then putting downstream protection on the main distribution switchboard to offer protection when on generator power and from internal transients.

However, a counter argument has been made that the only TVSS needed is at the distribution switchboard because that protects the critical load. This concept is that there is no need for TVSS at the service entrance at all because the main switchboard has an integrated surge arrestor module (Everguard AMP arrestor) and the UPSs also have some filtering abilities.

I am wondering what the advice any of you would have if this would your site. Would you put in a service entrance TVSS based on what I said.

Thanks.

 

[stevenal]

Transients tend to ring about the lines, bouncing back with voltage doubling near the reflection points. Best protection is achieved with TVSS at entrance and at sensitive loads.

 

[eddie11]

Hi stevenal.

I know the situation may vary, but if you had to choose just one location, which would you usually end up choosing in the environments you are familiar with:

1. service entrance
2. the output of the emergency power ATS that is fed by utility (normal) and generator (emergency)
3. most critical load panel

My situation is for a data center

 

[advidana]

I agree with you eddie11. REMEMBER IF SOMETHING GO'S WROMG YOUR BOSS OR CLIENT WILL MAKE YOU RESPONSIBLE, HE WILL NOT REMEMBER THAT THEY WANTED TO KEEP THE COST DOWN BY REDUCING THE TVSS USED. STICK TO YOUR GUNS. Why did they use you if they choose not to follow your recommendations.

 

[stevenal]

A question I would refuse to answer, substituting my own: Is the equipment and data worth protecting or not?

 

[stevenal]

See IEEE C62.41.