Lightning and lightning induced effects have significant influence on many aspects affecting the public, which makes the research of lightning and lightning protection very important. However, due to the strong randomness and complex discharge mechanisms of lightning, the understanding of lightning is still far from satisfactory. On the basis of the International Conference on Lightning Protection 2014, this study gives a review of recent progress on lightning and lightning protection research covering the following aspects: lightning locating and observation, lightning physics, lightning electromagnetic transients, and lightning protection for various systems. The goals of this study are to give readers an overall introduction to the recent progress in lightning and lightning protection research, and to motivate them to conduct further studies to address the unsolved problems in lightning-related research.

High-speed video images of 24 downward negative lightning flashes terminating on tall structures in Guangzhou are selected to analyse the connecting behaviour of the downward and upward leaders during the attachment process preceding the first return stroke. Three types of leader connecting behaviour have been observed: Type I, the tip of downward leader (DL) to the tip of upward connecting leader (UCL), which accounts for 42% of all the events (10/24); Type II, the DL's tip to the lateral surface of UCL, which accounts for 50% (12/24); and Type III, the combination of Types I and II, which accounts for 8% (2/24). For the two cases of Type III behaviour, each case had two junction points (one with Type I and the other with Type II behaviour) between the downward and upward leaders. Therefore, Types I and II can be viewed as the two basic types of the leader connecting behaviour during the attachment process in negative lightning. No attachment process exhibited the connection of the UCL's tip to the lateral surface of DL. The presence of multiple DL branches and their integrated effect on the development of positive UCL/UCLs are likely to be the main reasons for the Type II behaviour.

At present, the insulation performances of electrical apparatus under lightning impulse voltages are always evaluated by the withstand test of standard lightning impulse voltage (1.2/50 µs), which is recommended by IEC Standard. However, the actual time parameters of transformer invading lightning impulse voltage present an obvious dispersibility characteristics. The standard wave shape is only representative of one particular class of lightning waves, which is far from satisfactory to act as the guidance waveform in the design of power equipment insulation. On the basis of the above research background, the relationship between breakdown characteristics of oil paper insulation and time parameters of applied lightning impulse voltage was investigated in this study. The 50% breakdown voltage characteristics of oil paper insulation under lightning impulse voltage with different time parameters were determined. The test results indicate that a short wave front time could lead to relatively low 50% breakdown voltage, while when the wave tail time varied, the 50% breakdown voltage of oil paper insulation barely changed. At last the simulation model of oil paper insulation was developed, and the current flowing through the oil paper insulating system under lightning impulse voltage was calculated. On the basis of the simulating results, the relationship between current and time parameters was analysed.

A comprehensive review on the methods used for fault detection, classification and location in transmission lines and distribution systems is presented in this study. Though the three topics are highly correlated, the authors try to discuss them separately, so that one may have a more logical and comprehensive understanding of the concepts without getting confused. Great significance is also attached to the feature extraction process, without which the majority of the methods may not be implemented properly. Fault detection techniques are discussed on the basis of feature extraction. After the overall concepts and general ideas are presented, representative works as well as new progress in the techniques are covered and discussed in detail. One may find the content of this study helpful as a detailed literature review or a practical technical guidance.

Traditional insulation material is thermally insulating and has a low thermal conductivity. The miniaturisation and higher power of electrical devices would generate lots of heat, which have created new challenges to safe and stable operation of the grid. The development of insulating materials with high thermal conductivity provides a new method to solve these problems. The improvement of thermal conductivity would increase the ability to conduct heat and greatly reduce the operating temperature of the electrical equipment, which could reduce the equipment size and extend service life. On the other hand, inorganic thermally conductive particles and the improved thermal conductivity may have great effect on thermal breakdown. In this study, the factors affecting the thermal conductivity of dielectric polymer composites were explored. Intrinsic thermal conductive polymer and particle-filled thermal conductive composites were discussed. Effect of thermal conductivity, shape, size, surface treatment of the particle and prepare process on thermal properties of the composites were illustrated. This study focused on the electrical and thermal properties of thermally conductive epoxy, polyimide and polyethylene composites. Tracking failure caused by thermal accumulation is a typical thermal breakdown phenomenon. The performance of the resistance to tracking failure was studied for these composites. The results showed that thermal conductive particles improved the resistance to tracking failure. Finally, application of thermally conductive epoxy in electrical equipment was discussed.

The collectors for measuring the time profile of a current pulse of the runaway electron beam that are generated under atmospheric pressure are described. An analysis of changes in pulse shape depending on the bandwidth of the registration path with a temporal resolution of up to 20 ps was performed. It is shown that the electron beam detected behind small-diameter diaphragms has a complex structure, which depends on the parameters of the gas diode. There is a design of the current shunts with a temporal resolution of up to 100 ps in this study. Measurement techniques of voltage pulses with subnanosecond and nanosecond duration are briefly described.

It is important to estimate the current magnitude and charge amount of a partial discharge (PD) in a gas-insulated switchgear (GIS). In this study, electromagnetic fields generated by a PD in an 84 kV-class three-phase GIS for testing have been measured with a voltage probe installed on the outer surface of an insulation spacer of the GIS tank, and the corresponding simulations have been carried out using the three-dimensional finite-difference time-domain (FDTD) method. FDTD-computed time-domain voltages across spacers agree reasonably well with the corresponding measured ones, and the current magnitude of PD and its charge amount have been estimated.

An instability in the stable operation of microdischarges sustained at microwave frequencies, is investigated by a self-consistent one-dimensional particle-in-cell Monte Carlo collisions model. The instability is caused by the field electron emission from electrodes and is triggered by the high electric fields at the sheaths in a dense microplasma. For an operating frequency of 9 GHz, and electrode gap of 60 µm, the field emission (FE) is not active at the breakdown voltage. However, once a stable dense plasma is produced post-breakdown, a strong sheath results in an electrode electric fields that exceed the threshold for FE causing a runaway in the electron generation in the plasma.