1. Dielectrometry Measurements of Moisture Diffusion and Temperature Dynamics in Oil Impregnated PILC Cables Zachary M. Thomas Wolf, Greenfield & Sacks P.C. Markus Zahn Massachusetts Institute of Technology

2. Presentation Outline Motivation Dielectrometry Sensors Sample Materials and Setup Constant Temperature Measurements Transient Measurements Summary

3. Motivation Develop technology for cable health monitoring. What can dielectrometry sensors tell us about the electrical properties of PILC insulation? Cable Aging Mechanisms Temperature Fluctuations –Temperature varies with loading conditions. Moisture Ingress –Cracks and corrosion provide sights. –Aging of cellulose releases water. Partial Discharge (PD) –Formed in gaps and voids formed during temperature cycling in the cable insulation. –Regions of low oil content.

4. Dielectrometry Sensors Capacitive sensing technique. Requires access to one surface of MUT (material under test). Sensor response determined by MUT “effective permittivity” Periodicity i.e. wavelength determines sensor’s “depth perception.” Frequency domain measurements taken from mHz to kHz.

5. Sensor Excitation

6. Sensor Theory

7. Field Line Results

8. Sample Materials and Setup Sample Materials –PILC – Paper insulated lead covered cables –Teflon –Wood (Birch & Oak) –Polycarbonate –Polyethylene –Acrylic Experiments conducted in a vacuum chamber.

9. Constant Temp. Measurements

10. Transient Measurements

11. Maple Rod Measurements (130 F, 30% RH)

12. Maple Rod Mapping at 1 Hz

13. Maple Rod Moisture Profiles at 1 Hz

14. Single Conductor Cable Measurement

15. Single Conductor Cable Mapping at 1 Hz

16. Summary