Investigation on combined effect of humidity–temperature on partial discharge through dielectric performance evaluation

Abstract

The humidity role in the partial discharge (PD) inception mechanism is quite challenging, especially when considering the environmental temperature. Indeed, there is no general rule to explain the humidity effect on the PD phenomenon. In this paper, the PD activity in inter‐turn insulation is experimentally investigated for different relative humidity (RH) conditions at three different ambient temperatures, that is, 30°C, 60°C, and 90°C. Partial discharge inception voltage (PDIV) is directly measured through a photomultiplier tube (PMT), whereas the tip‐up tests are performed aiming at monitoring both dissipation factor (tanδ) and insulation capacitance (IC). These extra measurements (diagnostic dielectric markers) allow better assessing the insulation status. The adoption of the tip‐up test enables the insulation properties measurement. Based on the tip‐up tests’ findings, the interfacial polarization process starts at 75% RH under 60°C, while the high conductivity area is already formed at 75% RH when the ambient temperature is 90°C. The water film formation deduced from the tip‐up test is then used to explain the trend of PDIV, and the validity is further proved by finite element analysis (FEA).

On the frequency dependence of the PDIV in twisted pair magnet wire analogy in humid air

“…On the other hand, the decrease of the PDIV stems from the condensation of water on the insulation's surface, which is speculated to enhance the electric field. Also increasing PDIV with rising RH (above 60% at 30 • C) was observed for twisted pair samples in [Ji+23]. Similarly, the increment in PDIV is attributed to attachment of electrons via water molecules in air.…”

Static breakdown threshold modeling of quasi-uniform gas gaps with a focus on the PDIV of contacting enameled wire pairs

“…This result questions the general need for numerical field simulation in dry air that is often employed for calculating the PDIV of contacting enameled wires (e.g. [17,21,43]). Also, it should be emphasized that the quasi-uniform approximation (3) has been used successfully by Halleck as early as 1956 to calculate the PDIV of twisted wire samples [44], and is thus not to be regarded as an original contribution of this paper.…”

Besisukančių elektros mašinų izoliacijos varžos matavimo metodų tyrimas

“…Remdamiesi DD matavimo rezultatais ir nustatyta priežastimi, imamasi atitinkamų veiksnių suprastėjusiai izoliacijai pagerinti. Tokie veiksniai apima apvijų izoliuojančios medžiagos džiovinimą, valymą ar net izoliacijos pakeitimą (Ji et al, 2023).…”