Grounding system design ensures safety compliance for transmission lines under lightning conditions. In this article, the transient response of short concrete encased grounding electrodes is investigated, that is, a 2.5 m vertical rod and a 10 m horizontal electrode (HE) (counterpoise). Situations of first and subsequent lightning strokes applied to horizontal and vertical concrete encapsulated electrodes are analyzed. The effect of the frequency dependence of soil parameters is considered. Also, soils with low, medium, and high resistivities $(\text{300}{\bm{ }}$ to $\text{4000}{\bm{\ }}\Omega .m)$ are evaluated. Different lengths of concrete encasement are considered in order to verify situations with either partial or total encapsulation. For all these cases, the harmonic impedance (from 60 Hz to 4 MHz) is calculated, and the respective ground potential rise is derived for median lightning currents. The results obtained indicate that concrete encased electrodes produced reductions in the impulse impedance up to 30% for the HE and 44% for the vertical electrode. Moreover, for the evaluated situations, the percentage reduction on impulse impedance was only slightly affected by the increase in soil resistivity, which is also observed for soils modeled with constant parameters.

In this study, a new technique for circuit breaker diagnosis, based on broadband microstrip antennas, is presented. The diagnosis is based on the electromagnetic signals radiated by electric arcs in circuit breaker poles during opening operations. From each measured signal, several parameters are calculated, such as arc duration and signal energy, which are then processed by a statistical analysis routine, providing information that allows a correlation between the radiated signals and the degradation of the breaker contacts to be established. A current injection system was used in order to produce electric arcs. The technique was tested using nine contact samples, with different degradation levels. With the obtained results, it can be verified that the proposed technique is able to provide information regarding contact degradation level, arc duration, arc reignitions, and mechanical defects. The proposed technique is a simple and non-invasive solution, since the antenna can be placed far away from the equipment under evaluation. The use of antennas is a low-cost solution to circuit breaker monitoring, and since it provides a continuous monitoring system, a database containing the evolution history of contact degradation may be available.

Multiple‐level and up‐and‐down test methods are commonly employed in laboratories to obtain the breakdown voltage distribution of self‐restoring insulation, which is applied for equipment evaluation and for risk calculation in insulation coordination studies. This study investigates the reliability of the methods and proposes a methodology for evaluating their performance. The accuracy and precision of the estimated distribution parameters were analysed considering the variation of the test parameters. Algorithms that simulate the random nature of the tests were developed and applied in simulations. Then, a case study of risk calculation was carried out. The results indicated that both methods estimate the critical flashover voltage with acceptable accuracy and precision, even for the minimum parameters defined by standards. However, estimating the standard deviation is the critical step of the tests. The proposed methodology allows parameter definition for a given reliability requirement in the case of the constant voltage method. In the case of the up‐and‐down method, however, high dispersion was observed for all analysed cases, which indicates that this method presents low reliability for calculating flashover risk and, therefore, its use for insulation coordination studies is not recommended.