Sensor Comparison for Corona Discharge Detection Under Low Pressure Conditions

Abstract

Low pressure environments, situate insulation systems in a challenging position since partial discharges (PDs), corona and arc tracking are more likely to develop. Therefore, specific solutions are required to detect such harmful phenomena before major failure occurrence. This paper deals with three low-cost and small-size sensing methods, i.e., a single loop antenna, a visible-UV imaging sensor and the measurement of the leakage current to detect corona in the early stage, thus anticipating the appearance of severer effects such as arc tracking or disruptive breakdown. The three studied methods can be applied for an on-line monitoring of corona activity under low pressure environments, thus being compatible with predictive maintenance approaches. This on-line monitoring can be used to develop improved electrical protection devices able to detect such effects in an initial stage, thus improving current solutions which are unable to do so. All three studied sensors give consistent linear responses within the studied pressure range, i.e., 10-100 kPa, with almost no drift. The sensitivity of the visible-UV imaging sensor is slightly lower than that of the others, but it has the advantage of directly locating the discharge points. Results presented in this paper can be very useful for the more electrical aircraft (MEA), which is forcing electrical distribution systems to operate at higher voltage levels. Due to the little experience and scarcity of published data, the experimental results presented in this paper can be valuable for a better understanding of the combined action of high voltage and low pressure environments.

Corona Discharge Characteristics under Variable Frequency and Pressure Environments

“…The results presented in Figure 4 clearly show that CEV values are mainly affected by ambient pressure. The results plotted in Figure 4 are in accordance with previous studies analyzing gas discharges for specific supply frequencies [ 7 ]. This effect is due to the fact that the mean free path between ion collisions is inversely proportional to air density, and thus, a larger number of successful secondary ionizations are produced at a lower pressure, so that partial discharges can occur at lower voltages than the ones required at atmospheric pressure [ 39 ].…”

“…The sensibility to detect corona discharges of the image sensor has been tested and compared with that of the leakage current sensor, obtaining very close results, as shown in Figure 4 and in Table 4 , where the percentage differences are calculated, which are very low. A similar comparison was performed in [ 7 ] where it was also concluded that the imaging method with a CMOS camera has almost the same sensitivity as other sensitive methods for corona detection.…”

“…Jet aircrafts typically fly at altitudes between 33,000 and 42,000 feet (10,000 m to 12,800 m) [ 5 ], thus operating under harsh environmental conditions. Some electric and electronic aircraft systems operate in unpressurized zones [ 6 ], so electric and electronic aircraft systems must be designed to operate under a broad range of pressures, in the range 1 atm to 0.15 atm [ 7 ].…”

Measurement of Corona Discharges under Variable Geometry, Frequency and Pressure Environment

“…However, operation at high-voltage pose aircraft insulation systems in a big challenge, since the combined effect of higher voltages, high compactness ratios, high power-to-weight ratios, higher operating frequencies and low-pressure operation greatly increase the risk of partial discharge (PD) occurrence [1,2]. It is well known that low-pressure operation significantly reduces the dielectric strength of air [3][4][5], and thus, surface discharges tend to initiate at lower voltages compared to the voltages at which they initiate at sea-level. The reduction of the dielectric strength of atmospheric air at low pressure presents several disadvantages related to premature insulation degradation, insulation lifetime reduction and finally complete electrical breakdown [6] with the consequent risk of fire [7,8] and disconnection of circuits, which can lead to emergency landings, aborted operations or severe accidents [9].…”

Harmonic Components Analysis of Emitted Ultraviolet Signals of Aged Transmission Line Insulators under Different Surface Discharge Intensities

“…Currently, there has been more focus on non-contact methods of monitoring insulator surfaces for convenience and reliability. Such methods include acoustic, thermal [ 2 , 5 , 6 ], UV intensity, infrared [ 7 , 8 ], etc.…”