Tamperproof Protective Device Settings

[mayanees]

I'm looking for people's opinion and/or experience on the topic of assuring the integrity of breaker settings after they've been field-adjusted.
Or alternately stated, what do you do to assure that the adjustments on a breaker don't get changed from the value developed in a Power System Fault and Coordination Study.

One method I've seen that was effective - is that a sticker listing the settings is placed on the space/cubicle occupied by the breaker, then the Testing outfit accompanies that with their sticker directly on the breaker - showing when it was last tested.

But another way to do it - would be to equip the breaker with a lockable settings cover, and then seal the cover with a tamper-proof seal. We're considering doing this for Data Center electrical equipment, and I'm curious as to other folks' opinions and experience.

Thanks for any responses.

JM

 

[Krim]

I'm looking for people's opinion and/or experience on the topic of assuring the integrity of breaker settings after they've been field-adjusted.
Or alternately stated, what do you do to assure that the adjustments on a breaker don't get changed from the value developed in a Power System Fault and Coordination Study.

One method I've seen that was effective - is that a sticker listing the settings is placed on the space/cubicle occupied by the breaker, then the Testing outfit accompanies that with their sticker directly on the breaker - showing when it was last tested.

But another way to do it - would be to equip the breaker with a lockable settings cover, and then seal the cover with a tamper-proof seal. We're considering doing this for Data Center electrical equipment, and I'm curious as to other folks' opinions and experience.

Thanks for any responses.

JM

JM,
Often times these settings will require re-setting (or fine tuning) after a recommended break in period.Some spec sheets state this time period.
I usually don't put anything over them. These should be something that only "Qualified Persons" are tampering with anyway.

Carl

 

[zog]

Many modern trip units have password protected trip settings. I.E. AC PRO

Sometimes a retrofit is not necessary, direct replacement options exist.

What type of trip units do you have?

 

[mayanees]

trip unit types

trip unit types

Many modern trip units have password protected trip settings. I.E. AC PRO

Sometimes a retrofit is not necessary, direct replacement options exist.

What type of trip units do you have?

Zog,

I'm speaking in generalities, which is to say I'm trying to establish a standard for our company in the way that we leave the electrical system after the electrical equipment has been commissioned.
We do critical power systems design, and reliability and safety are compromised if someone can open a breaker door and change the adjustments on the breaker.

So what I'm generally referring to is new installations, with a concentration of Square D Masterpact breakers (among other manufacturers). The ones I'm most familiar with have a plexiglass cover over the settings, that has a built-in hasp, which allows for the installation of a seal to prevent opening - much like a POCO tamper-proof seal.

But it feels somewhat harsh to me that the breakers be sealed. The facility is manned with competent personnel, and the equipment is generally inaccessible. Although installation of that seal would certainly provide some degree of protection against willful sabotage - or even well-intentioned adjustments.

JM

 

[WDeanN]

Many modern trip units have password protected trip settings. I.E. AC PRO

Sometimes a retrofit is not necessary, direct replacement options exist.

What type of trip units do you have?

Zog,
Do you have any numbers on cost of replacement vs. retrofit?

 

[zog]

The micrologic trip units on the masterpact dosent have any password protection, as you know they are just dial settings with a cover as you described.

I trained substation techs for 10 years and 99% of them do not understand the result of changing these settings on the system coordination (or arc flash for that matter) if a breaker trips cranking up the setting is one of the first things that is done, then the main trips, then I get a call at 3AM on sunday for an outage. You know the drill.

May I suggest putting stickers on the covers that say something like "Unauthorized adjustment may cause........., contact engineering prior to adjusting" or something like that.

You can always spec your design with programable trip units that is password protected, these usually cost less than the OEM provided trip devices anyways.

 

[zog]

WdeanN,

That varies depending on what you are replacing but basically its less than half the cost, however if you breaker needs an overhaul you might as well do the retrofit, a new trip unit is worthless on a breaker that is in poor operating condition anyways. PM me for specific pricing if you want.

 

[Jraef]

The new Siemens VL Series MCCBs with Electronic Trip Units have a clear window that goes over the adjustment knobs. The window flips up or down to make adjustments, but has a small hasp into which a wire and tamper seal can be used to keep out the riff raff (or at least let you know it has been messed with by being broken)

Hard to see it on these pictures, but it is there.
http://www.icc-control.com/VL-Trip-Units.php.