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PurposeThe paper proposes and presents a comprehensive and integrated circuit model for investigating the behaviour of partial discharges occurring in voids inside the solid insulations of medium and high voltage cables.Design/methodology/approachThe model is based on the well‐known three capacitors model, which is remarkably improved to handle physical parameters such as cavity size, position, shape and pressure, environmental parameters such as cable temperature, in addition to operational parameters such as the contributions of the avalanche of free electrons inside the cavity through considering stochastic time delays.FindingsA complete, flexible and reliable model for partial discharges in voids inside the solid insulation of medium and high voltage cables is presented whose output agrees with experimental reported results.Research limitations/implicationsThe proposed model deals only with single voids, and the semiconductor layers in the insulation of cables are not considered.Practical implicationsThe model can be used in different physical, environmental and operational conditions in order to investigate the characteristics of partial discharge signals to be used as the bases for partial discharge detection and classification in power cables.Originality/valueThis paper presents a novel comprehensive and integrated circuit model with controlling functions to propose the behaviour of partial discharge occurring in voids inside the solid insulation of power cables. The model provides the contribution of geometrical parameters of the void, and operational conditions such as cable temperature and source frequency in partial discharge analysis.

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Loss of field (LOF) phenomenon in synchronous generators may cause serious damages and voltage drop in the power system, which can result in a blackout. Conventional methods, which detect LOF on the basis of the measured impedance from terminal viewpoint, are slow and may exhibit mal-operation in the face of other phenomena, e.g. stable power swing (SPS). In this paper, a novel technique is proposed to detect LOF in synchronous generators on the basis of some electrical quantities variations including voltage of terminal (V), current (I), active power (P), reactive power (Q) and power angle (δ). To evaluate the performance of the proposed algorithm, some cases are simulated under various operation conditions. Obtained results show that this algorithm on the basis of V, Q and δ not only can be considered as a fast LOF detector in comparison with the conventional impedance-based schemes, but also it is a robust and secure technique in the face of SPS and other power system disturbances. The proposed algorithm is tested by using an experimental setup including the laboratory synchronous generators, too. The obtained results show that the proposed technique can exhibit suitable performance in the actual conditions.