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Sensors 2015, 15(2), 3610-3624;

Development of a Moisture-in-Solid-Insulation Sensor for Power Transformers

Department of Electrical Engineering, Universidad Carlos III de Madrid, Avda de la Universidad 30, Leganés, Madrid 28911, Spain
School of Electrical and Electronic Engineering, Edificio 356 - Ciudad Universitaria, Meléndez, Calle 13 No 100-00, Cali 760032, Colombia
Author to whom correspondence should be addressed.
Received: 23 December 2014 / Revised: 7 January 2015 / Accepted: 22 January 2015 / Published: 4 February 2015
(This article belongs to the Section Physical Sensors)
Full-Text   |   PDF [455 KB, uploaded 4 February 2015]


Moisture is an important variable that must be kept under control to guarantee a safe operation of power transformers. Because of the hydrophilic character of cellulose, water mainly remains in the solid insulation, while just a few parts per million are dissolved in oil. The distribution of moisture between paper and oil is not static, but varies depending on the insulation temperature, and thus, water migration processes take place continuously during transformers operation. In this work, a sensor is presented that allows the determination of the moisture content of the transformer solid insulation in the steady state and during the moisture migration processes. The main objective of the design is that the electrodes of the sensor should not obstruct the movement of water from the solid insulation to the oil, so the proposed prototype uses a metallic-mesh electrode to do the measurements. The measurement setup is based on the characterization of the insulation dielectric response by means of the frequency dielectric spectroscopy (FDS) method. The sensitivity of the proposed sensor has been tested on samples with a moisture content within 1% to 5%, demonstrating the good sensitivity and repeatability of the measurements. View Full-Text
Keywords: dielectric response; power transformer; moisture; solid insulation; moisture sensor; FDS; moisture monitoring dielectric response; power transformer; moisture; solid insulation; moisture sensor; FDS; moisture monitoring
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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MDPI and ACS Style

García, B.; García, D.; Robles, G. Development of a Moisture-in-Solid-Insulation Sensor for Power Transformers. Sensors 2015, 15, 3610-3624.

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