Voltage Correction Factors for Air-Insulated Transmission Lines Operating in High-Altitude Regions to Limit Corona Activity: A Review

Abstract

Nowadays there are several transmission lines projected to be operating in high-altitude regions. It is well known that the installation altitude has an impact on the dielectric behavior of air-insulated systems. As a result, atmospheric and voltage correction factors must be applied in air-insulated transmission systems operating in high-altitude conditions. This paper performs an exhaustive literature review, including state-of-the-art research papers and International Standards of the available correction factors to limit corona activity and ensure proper performance when planning air-insulated transmission lines intended for high-altitude areas. It has been found that there are substantial differences among the various correction methods, differences that are more evident at higher altitudes. Most high-voltage standards were not conceived to test samples to be installed in high-altitude regions and, therefore, most high-voltage laboratories are not ready to face this issue, since more detailed information is required. It is proposed to conduct more research on this topic so that the atmospheric corrections and altitude correction factors found in the current International Standards can be updated and/or modified so that high-voltage components to be installed in high-altitude regions can be tested with more accuracy, taking into account their insulation structure.

Sensor Comparison for Corona Discharge Detection Under Low Pressure Conditions

“…Relative air density (RAD), which depends on atmospheric pressure P and thus on the altitude h above sea level, highly influences CEV and critical breakdown voltage values [41], [42]. In a lesser extent, other factors such as debris, moisture, vapors, fumes, conductive smoke, or extreme temperatures can also influence CEV and critical breakdown voltage values [43].…”

“…However, since most practical air gaps are non-uniform to some extent, Paschen's curves cannot be directly applied in such cases, whereas PD or corona activity can be generated at lower voltages than those required to form a disruptive discharge [48]. Most of the studies related to PD or corona inception values in low pressure environments are related to HVAC and HVDC transmission lines operating in high altitude regions in countries such as China, Nepal, Bhutan, India or Peru [42]. However, the pressure range analyzed in such studies is insufficient to understand the behavior of the discharges under typical aircraft environments, requiring broader pressure range.…”

Experimental Study of Visual Corona under Aeronautic Pressure Conditions Using Low-Cost Imaging Sensors

“…The presented data are based on different pressure conditions ranging from 100 to 20 kPa, thus covering the pressures typically found in aeronautic environments, while different air gap distances are analyzed. Most of the studies refer to power lines operating at higher altitudes [11][12][13], usually below 4000 m, dealing with pressure levels different than those found in aeronautic applications, whereas many other studies are based on spark [14][15][16], glow discharges [17], or discharges in gases other than air [18]. Therefore, there are a lack of experimental studies centered on the inception of corona for aeronautic applications, and this paper makes a contribution to this area.…”

Insulation Failure Quantification Based on the Energy of Digital Images Using Low-Cost Imaging Sensors

“…The dielectric strength reduces with air pressure, thus promoting ionization processes such as PDs, corona, arcing and arc tracking. Due to the low operating pressures, electrical systems appropriately designed for ground operations can be exposed to important levels of PDs in aircraft environments [ 13 ]. Low-pressure environments favor premature insulation ageing and degradation [ 14 ].…”