Lightning-induced voltages on multiconductor overhead lines

Lightning Currents Flowing in the Soil and Entering a Test Power Distribution Line Via Its Grounding

“…Table I gives the peak values for the total currents and corresponding charges of three return strokes and three Initial-Stage (IS) currents and compares them with the peak values of the currents and charges entering the line through the pole 15 line ground. The charge transfer was obtained by numerically integrating the measured return stroke currents and the IS currents over a 1 ms time interval and a 10-ms time interval, respectively 1 . Table I shows that the percentage of the return stroke current peaks entering the line through the pole 15 line ground is significantly smaller than the percentage of the IS current peaks entering the line (return stroke events: 7%, initial stage events: between 12% and 17%).…”

“…Note that the time of operation of these arresters depends on their proximity to the lightning; the pole 10 arrester operates first, and the pole 6 and pole 2 arresters operate 0.8 s and 1.5 s, respectively, after the pole 10 arrester operates. Currently available models for calculating currents and voltages on power lines due to nearby lightning strikes (e.g., [1]- [5]) do not explain the experimental result that the closest arrester at pole 14 does not conduct negative current. In fact, preliminary modeling results show not only negative current in all arresters but also negative current in the closest arrester at pole 14 to be over four times larger than the current in the pole 2 arrester (the arrester furthest away from the lightning).…”

“…, where is the coefficient of determination), but the linear regression equations are different for the return stroke and initial stage events (return stroke events: 1 A longer time interval was chosen to determine the charge transfer during the IS due to the longer duration of the IS current compared to the return stroke current. The length of the integration time interval to determine the IS charge does not affect the percentage of lightning charge entering the line (last column in Table I) since the charge injected into the pole 15 line ground and the lightning charge have very similar waveshapes (see Fig.…”

“…models simulate either: 1) nearby strike effects resulting from interaction of the power lines with the electromagnetic fields from lightning striking ground in the vicinity and inducing currents and voltages in the line [1]- [5] or 2) direct strike effects, which occur when lightning currents are directly injected into one of the line conductors or other above-ground elements of the line [1], [6]- [11]. In this latter case electromagnetic coupling effects are thought to be relatively small and are usually neglected.…”

Ground terminations of lightning protective systems

“…They have in fact different characteristics and thus it is necessary to verify the most dangerous to grounding system dimensioning Assuming that the step voltage is Us, ( t ) = us& (t) (8) and that the maximum step voltage V,, is a fraction K of the total ground voltage V,, according to the experimental results, it results in To design the ground system, the energies evaluated with Equations (16) and (17) values of the impulse impedance of the ground system to keep the step voltage within safety limits are shown in Table 2, for R, = 500 R and R, = 3000 0. Computations were carried out for negative lightning flashes only since it is more critical for the design.…”