×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Engine-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Engine-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Transformer purging after tripping off line

Transformer purging after tripping off line

Transformer purging after tripping off line

(OP)
When we have a distribution transformer clear the system due to fault indications on the transformer, we test the cover gas head space before we perform any testing on the transformer. The gas tester tests for hydrogen and level is given out in percent LEL. What is your process for purging the head space of hydrogen gas and what is an acceptable limit of hydrogen concentration before performing tests? The tests we start off with is meggar, ratio and TTR

RE: Transformer purging after tripping off line

SparkyPete,
The term 'Purging' is not used with transformers. The oil is degassed / dried using an transformer oil processing plant to remove the dissolved gases and moisture (if any) as well as other impurities.
Before that, since you are finding H2 in the gasses evolved from the transformer oil, you may want to inspect the transformer to diagnose the cause of gasses. You may also want to have DGA done on an oil sample for identifying the gasses in detail with the individual gas concentration levels.
It is not recommended to energise the transformer ithout identifying and addressing the underlying cause.

RE: Transformer purging after tripping off line

(OP)
We also do DGA samples but the question is removing hi hydrogen concentration in the gas headspace to enable us to perform transformer testing?

RE: Transformer purging after tripping off line

How about purging the space with nitrogen.

RE: Transformer purging after tripping off line

Quote:

How about purging the space with nitrogen.
Or the heavier CO2, admitted low while the H2 is drawn off high.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Transformer purging after tripping off line

This is what happened when a generator was improperly purged of hydrogen.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Transformer purging after tripping off line

(OP)
Waross,
That’s exactly what we want to prevent. I want to know what the industry thinks is a safe percentage of H2 gas in the head space before testing. Also we fill the head space with N2 to 8-10lbs through the 1/4”pipe fill valve and regulator and then vent through the same pipe and test for H2.

RE: Transformer purging after tripping off line

Why is the transformer creating hydrogen in the first place?
Your XF overloaded?
Oil supersaturated and creating gas bubbles?
Partial discharge an issue?

I believe I would try to find the underlying cause before I worry about just purging and replacing an N2 blanket

RE: Transformer purging after tripping off line

By the way, some power plant generators are cooled with pressurized hydrogen because it is a very efficient heat transfer fluid both because of its ability to convey heat and it requires less power to blow it around than air. Also, hydrogen without any oxygen or moisture protects the generator from moisture and oxygen degradation ( rust, etc. ) .

I am u too late. See you next week.

RE: Transformer purging after tripping off line

Sparkeypete, It looks like your transformer failed and the extent of failure is not known to you. The arcing must have produced hydrogen and other combustible hydrocarbon gases. In power transformers, it is a general guideline never to start low voltage testing immediately after any low impedance fault inside the transformer.
https://www.linkedin.com/pulse/a38-how-prevent-pow...
In distribution transformers, energy levels will be low and chances of excess combustible gases are low. My suggestion will be to purge out nitrogen and do fresh gas filling if you detect even slight levels of hydrogen and other gases. Wait for a couple of days before testing.

RE: Transformer purging after tripping off line

While hydrogen in the gas space is not a good sign, why do you wish to purge it prior to testing? Hydrogen and nitrogen is not an explosive mixture. Do you have reason to believe oxygen is present?

RE: Transformer purging after tripping off line

Nitrogen or air will dissolve in oil and transformers in service may contain 8-10 % dissolved air in oil. In nitrogen-sealed transformers chances of dissolved oxygen is remote but purging nitrogen may be an extra safety margin.

RE: Transformer purging after tripping off line

Not only H2 is a flammable gas. CO, methane, C2H2, C2H4 are too. Your last DGA should show a % value of combustible gas in the oil sample.

RE: Transformer purging after tripping off line

Rule of thumb is 10% of the LEL. Devices measuring % LEL are not sensitive to the particular gases being measured. https://safels.com/19-facts-you-should-know-about-...
I would consider energizing a faulted transformer risky, even with testing devices risky. Follow the advice above please.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Engine-Tips Forums free from inappropriate posts.
The Engine-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Engine-Tips forums is a member-only feature.

Click Here to join Engine-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Engine-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Engine-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close