Measurements and Modeling of Moisture in Transformer Insulation

The presence of moisture in a transformer
deteriorates the insulation by decreasing its
electrical, mechanical, and thermal strength.
Therefore, it is critical to monitor the moisture
condition in both liquid and solid insulation.
This book performs an extensive study of on-line
moisture monitoring for transformer insulation
systems and provides new tools and advanced
approaches on this topic.

A new set of moisture equilibrium curves for oil and
paper systems is constructed with a wider range than
reported in prior literature. Such curves can be
used to predict moisture in the paper insulation
from oil moisture measurements taken when the system
is in equilibrium.

When the system is not in equilibrium, the three-
wavelength interdigital dielectrometry sensor
developed at MIT provides a unique way to non-
destructively measure the spatial profile of the
moisture distribution in transformer pressboard. A
universal curve is found relating dielectric
properties to moisture concentration and
temperature. The diffusion coefficient for
pressboard as a function of temperature and moisture
concentration is estimated.

Autorentext
Dr.Du received her B.S. and M.S. degrees from Northwestern Polytechnical University in China, and E.E. and Ph.D. degrees from MIT, USA. She is currently a Managing Engineer at Exponent Inc. and a recognized expert on moisture issues for power insulation. She has published many papers, including award papers and invited lectures.

Klappentext
The presence of moisture in a transformer deteriorates the insulation by decreasing its electrical, mechanical, and thermal strength. Therefore, it is critical to monitor the moisture condition in both liquid and solid insulation. This book performs an extensive study of on-line moisture monitoring for transformer insulation systems and provides new tools and advanced approaches on this topic. A new set of moisture equilibrium curves for oil and paper systems is constructed with a wider range than reported in prior literature. Such curves can be used to predict moisture in the paper insulation from oil moisture measurements taken when the system is in equilibrium. When the system is not in equilibrium, the three- wavelength interdigital dielectrometry sensor developed at MIT provides a unique way to non- destructively measure the spatial profile of the moisture distribution in transformer pressboard. A universal curve is found relating dielectric properties to moisture concentration and temperature. The diffusion coefficient for pressboard as a function of temperature and moisture concentration is estimated.