Max Voltage Ratings on NON-Insulated Conductors

Thread Starter

TeraOhmTerry

Joined Apr 28, 2020
4
Good Morning All!

Firstly, I am brand new to this community but I can already tell this will be a huge resource for me going forward, and so I thank you all ahead of time for the help I am bound to receive here. Also I have no idea which "section" this would really belong in so please feel free to move this to wherever it should be.

So onto my question:

While ordering a few parts for a test fixture I am building at work, I was looking at a spec sheet for some various connectors that would be wired into this test fixture. My confusion comes from a "Maximum Hands-Free Voltage" rating. For this BANANA JACK it lists a 30/60VDC "Hand-Held Voltage" and a 2500VAC "Hands-Free Voltage". This confused me as there is no insulator involved here, so what could these ratings be based on?

I decided to check a few other non-insulated connectors and found many of them list max voltages despite not having any insulation. (EXAMPLE 2). Now in this application I am currently working on, I am not very concerned with these rating as it will see a maximum of 1kVDC and the currents are between femtoamp and microamp range. But I am also the person who handles high voltage testing of our components with up to 100kVDC. Many of the fixtures in those applications also use things like non-insulated ring terminals and butt connectors which when I look up the data sheets some of which list max voltage ratings like the examples above.

Until this discovery I had adhered to the idea that conductors have amperage ratings, insulators have voltage ratings, and I have based my designs around these ideas and now that this is casting doubt on my understanding of these fundamentals I worry that perhaps I have created a room full of un-safe designs all running tests between 10kVDC and 100kVDC.

What did I miss?

Again, thank you for any advice/information you can provide!
 

dl324

Joined Mar 30, 2015
10,750
Welcome to AAC!

The voltage ratings on uninsulated connectors may be CYA by the legal department at manufacturers. If you're designing things that operate at such high voltages, you should contact manufacturers for appropriate parameters.

For uninsulated materials, I'd factor in the environmental factors. If you're connecting to barrier strips, that becomes your insulating material. If you're connecting to a PCB, air and the board material are your insulating material.
 

Reloadron

Joined Jan 15, 2015
5,455
What did I miss?
Nothing unless I also didn't get the same memo? In this case I would call a manufacturer (and email them). Get what I call an applications engineer on the line and ask for a definition. I have been retired going on 7 years but in my over 40 years I never heard the term used. I would go with a company like Pomona:

"For technical support, please contact us at <E-mail address removed> and provide as many details as possible. We will attempt to respond to all requests in 72 business hours, but some questions will take further research and may take up to two weeks to answer. We appreciate your patience and understanding".

Ron

MOD EDIT: The e-mail link to Pomona's tech support was removed to prevent spambots from snarfing it up. That not only exposes Pomona to spam, but it makes AAC more attractive to spambots.

Go to their website, instead: https://www.pomonaelectronics.com/support/technical-support
 
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Janis59

Joined Aug 21, 2017
1,179
The thumb-rules for free air situation is for sure beat-through 3 kV/mm and for sure keep well 1 kV/mm, meanwhile in vacuum obstacles 3x lesser. If there are any sharp geometry able to koroning then divide distance to 10. Insulation provides most cases 10 kV/mm while some rare materials up to 30-40 kV/mm (without of any warranty).
 

Thread Starter

TeraOhmTerry

Joined Apr 28, 2020
4
Thank you for your replies. Its comforting to know that I wasn't crazy or uneducated in the field I work in.

In basically all cases above 10kVDC I am lowering this fixture into a large bath of FR3 dielectric oil, so I have all the insulation I need, even at 100kVDC. In the cases where I am testing <10kVDC typically the conductors are mounted in fixtures built from G10 and PTFE and are given ample spacing from everything else.

I will probably shoot Pomona/3M an email regarding their specs and just ask for any information on how that limit was determined.
 

SamR

Joined Mar 19, 2019
2,126
The bottom line is to follow the Code Specifications for the Governing Body (or Corporate Engineering Specs) for your location. I never heard of this during my career in the US following NEC and Corporate specifications. From the verbiage, I am assuming this deals with handheld measuring instruments and not enclosed or panel mounted devices? Which when dealing with old school "gauge thumpers" might as well be handheld.
 

MisterBill2

Joined Jan 23, 2018
6,072
That warning is because some folks see nothing unwise about grabbing wires and connectors with high voltage applied to them. And unfortunately our legal system is intensely opposed to natural selection work. So in your case it is important to avoid grabbing energized conductors. But you already knew that.
 
The banana jacks have two voltage ratings.
One is their "touch safe" voltage, which is obviously 30VAC/50VDC for OP's uninsulated part because that is the OSHA limit for safety... and liability reasons for any workers who could get an electric shock working with banana connectors. You should not be using banana jacks with hazardous live voltages unless there are safety lockouts etc. to prevent stupidity from killing someone and your employer being sued.

The other is the operating voltage which is about the insulation rating, usually for the bushing to chassis, which is 1000VDC "for hands-free use" in other words no touch use.
 
@Reloadron Yep, those. the arc lamp needed a 40 kV pulse to start, so basically you create your own insulator that the binding post mounts too like a 4" x 4" bakelite and get the higher breakdown voltage that you need. The cables were silicone insulated.

Later, the light source manufacturer, put the ignitor in the lamp housing. Before they did that, their external ignotor needed some serious re-working which I passed onto them.
 

WBahn

Joined Mar 31, 2012
25,760
The Pomona catalog states (in several places):

"The components in this section have a hands free rating for use in controlled voltage environments. "

So your next step in the journey is to ask Pomona exactly what constitutes a "controlled voltage environment".

At the same time, you might ask then "voltage relative to what"?

It could be that they are talking about the voltage difference between the plug and the jack as they are being connected. But that doesn't give me a warm fuzzy.

Never be afraid to call and talk to the manufacturer. My experience has almost universally been that it doesn't take long to get transferred to someone that knows what they are talking about and who is more than willing to talk to you about it.
 

MisterBill2

Joined Jan 23, 2018
6,072
The Pomona catalog states (in several places):

"The components in this section have a hands free rating for use in controlled voltage environments. "

So your next step in the journey is to ask Pomona exactly what constitutes a "controlled voltage environment".

At the same time, you might ask then "voltage relative to what"?

It could be that they are talking about the voltage difference between the plug and the jack as they are being connected. But that doesn't give me a warm fuzzy.

Never be afraid to call and talk to the manufacturer. My experience has almost universally been that it doesn't take long to get transferred to someone that knows what they are talking about and who is more than willing to talk to you about it.
"Voltage relative to WHAT?" would be relative to anything else that a person could touch at the same time. Not "reasonably" touch, but possibly touch. The safety rules seem to be writen to protect those bent on self destruction, rather than folks who have some understanding of what they are involved with. It relates back to the ISO9000 concept that the job should be simple enough and the instructions so explicit that "any person off the street could do the job correctly the first time." At least that is the understanding of it that I gained when one company I worked at worked to become ISO9000 certified. The hidden whole concept was intended to avoid the need of hiring expensive and highly skilled folks to do the complex technical tasks. Of course that part is denied by many of the folks who claim it is only about quality. (sorry about deviating from the original thread topic there.)
 

Thread Starter

TeraOhmTerry

Joined Apr 28, 2020
4
Great info and suggestions from all of you! I appreciate it.

To be more clear about MY specific application (which these banana jacks are not a part of, just was a good example of a bare conductor with a "max voltage" rating.) I am performing qualification tests on a multitude of very high value resistors (in the range of 10G to 4.5T) which require varying lengths of tests (24-2000hrs) at voltages up to 100kVDC. Anywhere between femtoamps to ~10mA for current. (Typically I have the current limit on the supplies set to around 5mA unless more is needed.)

As far as the "controlled voltage environment", the HV supply output cable is stripped down to bare wire at the end and connected with a heavy duty crimp ring terminal to a bolt mounted in a PP basket. Both the source and return cables are attached to this basket. Inside the basket, I have simple silicone test lead wire (1000VDC) with alligator clips on both ends to connect the resistor under test to the bolts the power supply cables are attached to. This basket rests on top of a large PP tank full of FR3 oil. Once the resistor(s) are connected to the wires, the basket is lowered into the tank and ALL bare metal surfaces are fully submerged in the oil. Only then is power slowly ramped up to 100kVDC.

To me this constitutes a "Controlled voltage environment" as long as I keep up with replacing the oil and re-checking the crimped connections on the HV cables. Also, I am the only person that is allowed to enter this room at all, with the exception of a couple engineers trained as my back-up. So I'm not too worried about any general employee coming into contact with these set-ups, as they would have had to ignore all the "AUTHORIZED PERSONNEL ONLY. HAZARDOUS VOLTAGES PRESENT" signs on the door.

I just wanted to make sure that these connectors wouldn't exhibit some unexpected behavior due to seeing 100x their rated voltage. (like becoming brittle and breaking).
 

MisterBill2

Joined Jan 23, 2018
6,072
OK, and that is the most unusual application have heard of, by far. In some countries there would need to be automatic locks on the doors to keep those who ignore warning signs out. I have had to deal with that.
And I am quite certain that everybody associated with that project understands the hazards of high voltages.

One project I did at one place, the one electrical enclosure has a sign "High voltage, HAZARD OF DEATH". Quite an explicit warning. That enclosure is installed eight feet up a column, so nobody will get into it accidentally. And nobody has sought to lessen the warning to a gentler one.
And that is only a 480 and 240 system enclosure.
 

Janis59

Joined Aug 21, 2017
1,179
RE:""That warning is because some folks see nothing unwise about grabbing wires and connectors with high voltage""
Not only this whatever true. But if the voltage is really high like the cathode of electron microscope, the last I repaired was on 380 000 Volts the so tiny thing as open cover means that across the work hall all my hairs on the head lifts up and stay there upward. However distance is many meters.
 

Janis59

Joined Aug 21, 2017
1,179
RE: ""Voltage relative to WHAT?""
Its a question having a multiple answers. Yes, for well insulated hand, theoretically, is safe to touch practically ethernal Voltage. But it isnt so in the practice. Just Human Body Exuivalent Modell means 1) capacitance to the ground 2)capacitance to itself the body. So, if touch, the short but powerful lading current will run through, and it is esaily noted wit just touching the high voltage wire staying on good taburette. It beats anyway. I am witness.
 

WBahn

Joined Mar 31, 2012
25,760
To me this constitutes a "Controlled voltage environment"
It really doesn't matter if it constitutes such an environment to you (or me or anyone except the people writing the spec). You really need to find out from Pomona (or, if it's a standardized term from some regulatory or standards organization, from them or their publications) what THEY mean by it, because it is only within that context that the number has meaning.

RE: ""Voltage relative to WHAT?""
Its a question having a multiple answers.
Not really. It has multiple reasonable answers, but the only one that matters is the one that applies to that specification and that involves finding out what that answer is, probably from Pomona.
 

WBahn

Joined Mar 31, 2012
25,760
"Voltage relative to WHAT?" would be relative to anything else that a person could touch at the same time.
I don't think that's the case, otherwise there wouldn't be such widely different specs ranging from a few hundred voltage for some parts to tens of thousands of volts for others.
 
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