Corona inception field of typical overhead line conductors under variable atmospheric conditions

The Corona Phenomenon in Overhead Lines: Critical Overview of Most Common and Reliable Available Models

“…where K P = 0.3 in the original formulation by Peek. As expected, the inception field in (1), expressed in kV/cm, only depends on the conductor radius r 0 , and not on any other geometrical feature of the configuration under test (which, on the contrary, affects the onset voltage); δ is the air density factor, and f p is the polarity factor, which takes into account the effect of voltage polarity on E inc since experimental evidence has shown that the inception electric field associated with positive corona may hold different values with respect to those related to negative corona (with reference to the coaxial configuration, [38]); m is a constant to take into account the irregularity of the conductor surface, distinguishing between perfectly smooth conductors and rough surfaces due to weather conditions and aging under operation. From the manipulation of (1), assuming δ = 1 and axial-symmetric configuration, Peek's criterion may be alternatively interpreted as the value of the electric field at the conductor surface allowing to reach a field equal to E 0 at distance r = r 0 + 0.301 √ r 0 from the conductor axis, E 0 being independent from the configuration under analysis.…”

“…Even though we have referred to the potential, since it is often used in numerical codes as a threshold value for the simulation of the corona inception, the electric field distribution is the primary cause of corona. Bousiou et al [38] showed the trend of the electric field magnitude at increasing distance from the conductor outer radius r 0 , for different stranding ratios, showing that, for r → r 0 , the electric field for stranded conductors tends to a value approximately equal to 1.4 times E inc for the corresponding smooth conductor, independently from the number of external strands; however, as expected, the trend of E(r) approximates that of smooth conductors as the number of external strands increases. Furthermore, at equal applied voltage, the electric field holds higher values with a decreasing number of strands, also at larger distance from the conductor axis [44]; it is reasonable that the inception depends on the distribution of the electric field and not only on its maximum value; thus, lower values of E inc found for higher stranding ratios [38] are justified.…”

Fast Corona Discharge Assessment Using FDM integrated With Full Multigrid Method in HVDC Transmission Lines Considering Wind Impact

“…From a mathematical point of view, the solution of the monopolar corona problem, defined by equations (1) to (4), requires three boundary conditions for any conductor geometry. It is required to provide sufficient estimations of the corona inception field of line conductors [27]. In the present study, the assumptions of the electric field constancy at the ionized wire surface at its onset value (Deutsch assumption), and that the space charge impacts only the magnitude, but not the direction of the electric field (Kaptzov assumption) are ignored.…”

Corona Effect Influence on the Lightning Performance of Overhead Distribution Lines

“…Figure 4 of Reference [21] showed the variation of the critical electric field as a function of the air humidity. In Reference [22], recently, the authors provided a new expression for the critical electric field under variable atmospheric conditions, which is here proposed for sake of completeness.…”

“…being δ the relative air density, H the air humidity, n s a coefficient depending on the number of strands in the outer layer of the conductor and A, a, b, c coefficients depending on the voltage polarity ( Table 1 of Reference [22]). In addition to this, the corona discharge occurs if a free electron is available at the instant when the electric field overcomes the critical value in (1).…”