Search

Premium Membership ♕

Limited Time Offer: Save 15% on PRO Plan with discount code: LRN15 and study specialized LV/MV/HV technical articles and studies.

Home / Technical Articles / Moisture Effect On Insulation Of Generator

Moisture, which can enter the insulation of a generator or motor winding from damp air or which can enter the winding of a transformer from wet oil, will make a surprisingly large difference in the insulation resistance. This is clearly shown by the curves of figure 2 for a Grand Coulee generator.

Curve “A” was taken shortly after the generator was placed in service, at a temperature of 36 EC. Curve “C” was taken after a dry-out run of 168 hours on the generator.

Figure 2. - Dielectric absorption curves before and after initial dryout for Grand Coulee unit L-6 108,000-kVA, 120-r/min, 13.8-kV, 60-Hz generator.
Figure 2. - Dielectric absorption curves before and after initial dryout for Grand Coulee unit L-6 108,000-kVA, 120-r/min, 13.8-kV, 60-Hz generator.

The generator winding was, therefore, more thoroughly dried out in curve “C” than in curve “A,” although evaporation of the volatile content of the insulation or other curing or aging effect may have had an appreciable effect. Low insulation resistance resulting from exposure to moisture does not mean that the insulation is unsuitable for operation, particularly if the insulation resistance value is comparable to that obtained from recent periodic tests.

Dry out of thermosetting insulation is not as big a factor, and is sometimes not done, except to cure field applied insulation.

Premium Membership

Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! It helps you to shape up your technical skills in your everyday life as an electrical engineer.
More Information
author-pic

Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.

Leave a Comment

Tell us what you're thinking. We care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

2  +  five  =  

Learn How to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Enjoy learning!

Subscribe to Weekly Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and guides (PDF).
EEP Academy Courses - A hand crafted cutting-edge electrical engineering knowledge