INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Link to Hengfeng

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-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!

Join Us!

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

Posting Guidelines

Students Click Here

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

Eng-Tips Posting Policies

Contact US

Acceptable maximum Tan delta value for new distribution transformers

3

thread238- Forum Search FAQs Links MVPs

• Forum

• Search

• FAQs

• Links

• MVPs

If you are looking for more details, kindly visit Tan Delta Tester for Insulation Testing.

Acceptable maximum Tan delta value for new distribution transformers

Acceptable maximum Tan delta value for new distribution transformers

Rwelagedara

(Electrical)

(OP)

29 Jul 20 12:14

Dear All,
What shall be the acceptable tan delta values as power frequency and 20 degrees of Celsius for new small distribution transformers.
For larger power transformers there are specified maximum value of 0.5%. But when we are doing the testing in many number of small distribution transformers from many manufacturers, we are typically getting values over 0.5%.Is this normal?These small transformers are oil filled type and rated 33 kV/400 V and with porcelain type bushings.Is there any standard or guideline setting the maximum value for tan delta for these.

Replies continue below

Recommended for you

RE: Acceptable maximum Tan delta value for new distribution transformers

2

argotier

(Electrical)

29 Jul 20 23:02

First of all, there is no consensus for the tan delta (or power factor) limits in transformers.

The 0.5% limit for power transformers is not stated in the transformers "design" standards, but in the ones related to field testing and maintenance:

- ANSI/IEEE C57.152 IEEE Guide for Diagnostic Field Testing of Fluid-Filled Power Transformers, Regulators, and Reactors recommends for new transformers PF < 0.5% and between 0.5% and 1% worthy of further inspection/analysis.

- CIGRE 445 Guide for Transformer Maintenance it only states that a typical value is 0.5% and higher than 1% is questionable.

The only reference for distribution transformers I've found is this (frankly I didn't know this existed till now): ANSI/NETA MTS Standard for Maintenance Testing Specifications for Electrical Power Equipment and Systems

In that standard the maximum value (for maintenance test) for oil filled power transformers is 1% and for oil filled distribution transformers is 2%.

Hope it helps.

RE: Acceptable maximum Tan delta value for new distribution transformers

prc

(Electrical)

30 Jul 20 11:25

As per CIGRE TB761- Condition Assessment of Transformers limit for new units is 0.5 % for oil filled units and 1 % for natural ester filled units. Limit for keeping in service is 2.5 % and 4 % respectively.

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 Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

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

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

News

Contact us to discuss your requirements of Tan Delta Tester for preventive testing. Our experienced sales team can help you identify the options that best suit your needs.