The continuous monitoring of power system devices is an important step towards keeping such capital assets safe. Partial discharge (PD) based measurement tools provide a reliable and accurate condition assessment of power system insulations. It is very common that voids or cavities exist in every solid dielectric insulation medium. In this paper, different voids are modeled and analysed using an advanced finite-element (FE)-based computational algorithm. The proposed approach can be used to measure PD in cavities and voids regardless of their shape and size. The frequentative scripting approach with finite element modeling (FEM) provides the results which satisfy all PD conditions. PD behavior has been studied and analysed through PD statistical features obtained from the simulated PD signal. A comparative study between simulated and experimental results is also performed to validate the accuracy of the proposed modeling approach. To further improve the accuracy of the model, the influence and optimization of certain free parameters required for modeling has been carried out. The paper shows how PD is greatly influenced with the shape and size of voids in dielectric insulators. The research realized in this paper further provides the PD statistical features and its variation with respect to void shape and size. These features are utilized for the assessment of the insulation quality. The variation in PD parameters with respect to voltage level is also presented and discussed.

Power transformers and gas-insulated switchgear (GIS) play crucial roles in electrical power grids. However, they may suffer from degradation of insulation material due to wear and tear, leading to their imminent failure. Partial discharges (PDs) are an initial sign of insulation materials degradation which emit signals spanning various physical domains, including electromagnetic. PDs are temporally narrow, high-frequency, stochastic radiation sources. The Ultra-Wideband Vivaldi Antenna is the key element for the detection of PDs in power transformers and gas-insulated switchgear. However, they may be subject to different interference environments due to external sources of telecommunication radiation noise occupying the 2.4 GHz – 2.5 GHz band. Noise mixing with PD signals is challenging to resolve, especially for external sensors. Wi-Fi and Bluetooth signals from mobile devices easily overshadow faint PD signals. Band-reject frequency filters may be attached to the antenna, often at the detriment of the insertion loss. The integrated filter does not require any additional post-processing, making it less computationally demanding for smaller processors used in practice. Wi-Fi and Bluetooth degrade the PD signal, necessitating an integrated analog notch filter for noise removal. Therefore, an external ultra-wideband (UWB) Vivaldi antenna with an integrated noise-rejecting parasitic notch filter is designed, fabricated, and tested to detect PDs in electrical assets such as transformers, power cables, and GIS, with GIS being the focus in the experimental validation in this study. A comparative study of the proposed antenna is presented. This paper proposed an antenna that is designed to provide coverage of 95.516% of the 0.226 GHz – 3.506 GHz frequency band, with an average return loss of -16.04 dB and a peak gain of 5.5 in the working band, excluding the notched band. The peak return loss in the 2.4 GHz – 2.5 GHz rejection band is -2.68 dB, with an average attenuation of -35.74 dB. This wide coverage is demonstrated in this paper using simulation and experimentally.

The paper presents the methods of assessing the technical condition of varistor surge arresters used in laboratory tests and in operation—performed without disconnecting the arresters from the network. The analysis of the diagnostic methods was supplemented with the results of the measurements of the leakage current of arresters coming directly from their production and used in the power industry. Among the available methods of evaluating the technical condition of arresters, mainly indicator solutions (temperature and operation counter) and the measurement of the selected parameters of the leakage current are used. In the latter, the method of determining the resistive component of the leakage current, determined on the basis of the analysis of the voltage and current waveforms, or only the arrester current, has become widespread. In this type of measurement, current clamps are used in the operation, and additionally, in voltage measurements, voltage transformers are used, where you have to take into account the fundamental, additional sources of errors discussed in the article. These errors and the dispersion resulting from the production technology may fundamentally hinder the proper assessment of the technical condition; hence, it is so important to properly recognize the listed basic sources of measurement uncertainty. In addition, the analysis should take into account three factors related to external conditions: temperature, the voltage applied to the arrester, and the content of higher harmonics in the supply voltage, for which appropriate methods have been provided to determine the active component of the leakage current for reference conditions. This article presents the results of the measurements of the leakage currents of surge arresters measured with various methods.

This paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact, protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled void is placed inside and outside the protrusions, and a water tree produced from protrusions is under consideration. The partial discharge influence taking place at the protrusions and the stress enhancement factor is determined for all the variations mentioned to quantify the rise in the inception of partial discharges due to the protrusions.

Users expect reliable operation of the surge arrester during overvoltages, which may originate from a switching process or a lightning discharge. The necessary conditions to guarantee these expectations are: appropriate construction of the surge arrester, its production being maintained in accordance with technical standards, and a positive results of the type test. The recipient, especially when purchasing large quantities of the product, can check the final quality of the product through selective testing of samples from the market in order to find the best supplier. This manuscript specifies the basic parameters of low-voltage (LV) surge arresters of four manufacturers. Basic electrical parameters, i.e. leakage current and reference voltage before and after the discharge current of 8 μs /20 μs, were determined for 10 randomly selected surge arresters of each manufacturer. Moreover one sample of each varistor batches was aged by 50 simulated lightning strikes. The obtained results of structural analysis indicate that the crystal structure of the varistor materials changes after ageing process, affecting its electrical properties. The proposed research methodology can be employed as a basis for forecasting the stability of the arrester parameters under operating conditions.