The IEC 61850 series of standards for electrical substations harness the potential of Ethernet based wired networks as the backbone for intra-substation data communication. However, the flexibility of the standard, particularly the IEC 61850-90-5, enables the integration of emerging communication technologies such as wireless 5G cellular network for both intra and inter-substation data communication. In this paper, we evaluate and compare the reliability of a digital substation by analyzing different network architectures used based on wired Ethernet networks and wireless 5G networks. Reliability Block Diagram (RBD) approach have been implemented to conduct the comparison and the availability and Mean Time to Failure (MTTF) have been evaluated. The results show that the wireless 5G networks have a positive impact on the availability of the substation but the MTTF and Mean Time to Repair (MTTR) was found to decrease when compared to the wired Ethernet networks. However, such results indicate that the wireless 5G network is a sensible upgrade for the digital substation when considering the advantages and flexibility offered by the technology.

Digital substation technology adhering to the IEC 61850 standard has provided several opportunities and flexibility for the rapid growth and complexity of the present and future electrical grid. The communication infrastructure allows complete interoperability between legacy and modern devices. The emergence of 5G wireless communication and its utilization in substation operation presents significant advantages in terms of cost and scalability, while also introducing challenges. This paper identifies research gaps in the literature and offers valuable insights for future analysis by providing a simulation study using an empirical latency dataset of a 5G network to illustrate three aspects of substation operational challenges: coordination of protection schemes, sequential reception of packet data streams, and time synchronization processes. The findings show a mean latency of 8.5 ms for the 5G network, which is significantly higher than that of a wired Ethernet network. The results also indicate that the high latency and jitter compromise the selectivity of protection schemes. The variability in latency disrupts the sequence of arriving data packets such that the packet buffering and processing delay increases from around 1.5 ms to 11.0 ms and the buffer size would need to increase by 6 to 10 times to handle out-of-sequence packets. Additionally, a time synchronization success rate of 14.3% within a 0.1 ms accuracy range found in this study indicates that the IEEE 1588 protocol is severely affected by the latency fluctuations.

The specific frequency range of 9 to 150 kHz was omitted from the main part of the IEC 62236 (2018), which is equivalent to EN 50121, and is presented as an informative part due to the poor reproducibility of the measurement results of the radiated emission of trains. In this paper, the merits of time domain measurements and time-frequency analysis of the radiated emission of trains have been utilized in order to propose some prerequisites to lessen the uncertainties to obtain repeatable and reproducible measurement results in the frequency range of 9 to 150 kHz. To this end, 23 measurements from trains are presented, the performance of the trains have been investigated considering the previous IEC/EN limits, and comparisons have been made between some of them. Furthermore, based on the results of time-frequency analysis of the radiated emission, it has been revealed that the maximum amplitude of the radiated emission for some frequency components occurs before train arrival to (or after train passage from) the measurement location. Moreover, two indices have been introduced to compare the performance of different trains from radiated emission perspective. Finally, calculation of the rms radiated emission spectrum has been proposed to alleviate the influence of train operation (e.g., acceleration, cruising, coasting, and braking) on radiated emission measurement results; and some constraints have been proposed to minimize the uncertainties resulted from operation modes so that repeatable and reproducible results could be achieved to find more accurate curve of maximum radiated emission spectrum of a train.

The CIGRE Working Group A3.43 has published the technical brochure (TB) 953 Tools for lifecycle management of T&D switchgear based on data from condition monitoring. This work is a continuation of the previous working group that produced the CIGRE technical brochure 737 and it builds on other ones as well. The main objective is to develop a method for assessing the condition of the switchgear, considering mechanical, dielectric and electric wear as well as the functioning of the auxiliary circuits. It covers both transmission and distribution (T&D) equipment.One of the results is a large table that shows the correlation between condition indicators and degradation mechanisms. Based on data mining of that table, we propose the monitoring of 23 condition indicators out of 39 ones. This table is part of a systematic approach for lifecycle management of switchgear. A systematic methodology is outlined to group the potential degradation mechanisms and derive a well-defined conservative subset of 23 condition indicators out of the total set of 39, thereby providing a coherent strategy to minimize the number of sensors required to be installed for condition assessment of switchgear.

The frequency domain measurement of radiated emissions from electric railways (from 9 kHz up to 150 kHz) has been omitted from the main part of the relevant standard (lack of repeatability and reproducibility of the results is mentioned as the reason). This paper describes the radiated emissions measured from three electric trains to emphasize the importance of the suitable time length selection (by comparing specific durations of the recorded data: 1 min and 5 min) and the influence of calculation methods of the resultant spectrum in frequency domain (RMS, mean, and Max of spectrum). The results revealed the requirement of unique definitions for pre-, during-, and post-measurement factors so that the repeatable and reproducible results could be achieved. The prerequisites for having less uncertain results are as follows: (1) pure background measurement (in energized and de-energized state of the catenary); (2) precoordinated operation mode, speed, and power of the train during the measurement; (3) precise details of the analysis step. A unique analysis method is required (to be clearly elaborated in the relevant standards) to obtain comparable results between different working groups engaged with the radiated-emission measurements from a train in a frequency range of 9 kHz to 150 kHz.

Alternative solutions, instead of building new transmission lines, are needed to enable the fast electrification of sectors such as industry, transportation, and heating. This includes smart-grid technology allowing for an increase in hosting capacity without the need for building new transmission lines. The increase in hosting capacity beyond the firm hosting capacity is, with many of the schemes, related to the ability of the installation to tolerate curtailment. The paper gives an overview of different smart-grid schemes and how they potentially increase the hosting capacity. The connection of a large electrolyser installation for hydrogen production is used as an illustrative example introducing some of the issues.

Distributed generation feeds into the distribution part of the electric grid. As it is constructed with power flows going from higher to lower voltages, there might be problems with overloading and high currents, caused by more production than consumption in the area fed by a substation. To estimate the impact of generation connected to the distribution system, there is need for a statistical description of the production. Five years of data from a solar power plant in Luleå have been analysed statistically. Also, a physical model has been applied. The results show that the physical model manages to predict reasonable the data. Of the five years, one has apparently a lower production, but it is due to the lack of data. There is a marked seasonality, where the power drops considerable in September and vanishes during winter. The variation at a certain day and a certain hour is large, as the interquartile distance is about one half of the maximum power in summer.

Distributed generation feeds into the distribution part of the electric grid. As it is constructed with power flows going from higher to lower voltages, there might be problems with overloading and high currents, caused by more production than consumption in the area fed by a substation. 

To estimate the impact of generation connected to the distribution system, there is need for a statistical description of the production. Five years of data from a solar power plant in Luleå have been analysed statistically. Also, a physical model has been applied. 

The results show that the physical model manages to predict reasonable the data. There right-hand tail is reasonably similar from year to year. 

Planning of maintenance should take into account the condition of the different pieces of equipment instead of having a prescribed interval of certain number of years.

The working group A3.43 of CIGRE, an organisation for high-voltage electrical technology, studies maintenance strategies for circuit breakers, a key component in electric grids. It has compiled a 46x39 matrix, which maps the connection between failure modes and diagnostic methods as estimated by experienced engineers. Each element is a number from 0 to 3, where a higher number indicates a clearer connection between them.

In order to understand better how the failure modes and the diagnostic methods are related to each other, a clustering method is applied to the matrix. The chosen method is a hierarchical clustering, where both rows and columns are reordered using the Euclidean and the Manhattan distance function.\cite[p 301]{cha2007} The result is presented as a heatmap with dendrograms showing the possible clusters in the columns and the rows, respectively.

The results are graphs that give a comprehensive picture of how the failure modes and the diagnostic methods are related. This is valuable for newcomers in the field. The Manhattan distance function gives less value to elements in the matrix.