A comparative study of insulator materials exposed to high voltage AC and DC surface discharges
Date
2009-03
Authors
Heger, Gernot
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
The rising worldwide popularity of HVDC applications for power transmission
purposes increases the need to study the performance of commonly used insulation
materials when exposed to this voltage type. The aim of this study is thus to compare
several insulation materials according to their resistance to erosion and tracking when
exposed to surface discharges of HVAC and HVDC voltages of both polarities. The
materials are tested according to the Incline Plane Test method described in the IEC
60587 standard, using a test voltage of 4.0 kV (rms).
An important aspect of this project is the development of a bipolar DC source capable
of delivering the required test voltage and current for both positive and negative
polarities, while performing in accordance with the specifications set down in the
standard. The design is intentionally kept modular in order to make it adaptable for
future installations.
Since the standard describes two different test methods, i.e. the constant tracking
voltage method and the stepwise tracking voltage method, a comparison is done
between the two methods in order to determine which one delivers best results for the
test samples. The comparison shows that the methods deliver comparable results, but
the constant tracking voltage method is preferred due to its superior test procedure.
Finally, four different polymer insulator materials are tested and successfully
compared under the effects of HVAC and HVDC of both polarities. The test materials
include a RTV silicone rubber coated ceramic, two different HTV silicone rubbers
and an EPDM rubber. The comparison is done according to the results obtained for a
number of evaluation criteria. The results show that the RTV silicone rubber coating
exhibits the least erosion for an AC voltage, but shows extensive erosion for a
negative DC voltage. The HTV silicone rubbers exhibit only minimal erosion when
exposed to an AC test voltage, but develop strong erosion under a positive DC voltage
which can result in sample failure. The EPDM experiences its least erosion for a
negative DC voltage, but shows maximum erosion severity for the AC voltage.
Description
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.
Keywords
Theses -- Electrical and electronic engineering, Dissertations -- Electrical and electronic engineering