The paper presents the defined conception of the agent structure of the multi-agent system that performs the tasks of power system protection. The required input data sets and the input agents that provide observability of the power system were determined. The paper also proposes the agent input data acquisition ways that allow fast access to power system status information. The proposal of agents' attributes that define their functionality in spatially and layered distributed structure of the multi-agent systems was also discussed. The paper presents also the simulation results evolving from the implementation of the agents' functionalities in the digital power line distance protections.

Complex phase shifting transformer protection scheme and complexity of the object itself created a need to use simulation programs for their analysis. Often phase shifting transformer (PST) are modeled as a simplified series impedance and quadrature voltage source which cannot be used for power system protection analysis, especially in a transient condition. Therefore, the procedure of building realistic PST model was presented by using available transformer models with calculation of their parameters including interconnections between units. Paper consist calculations based on case study with symmetrical dual-core PST example. Additionally, theoretical background of PST principle, operation, and their impact of power system protection were introduced with numerus examples of PST model verification.

Paper presents an innovative concept for automatic selection of an optimal tap of the phase shifting transformer (PST) before its switching-on. The purpose of the system is to enable the switching-on of the PST without sudden changes in power network operating conditions. For the investigation of the underlying phenomena during switching, a test power network containing the accurate dynamic model of the PST was developed. The investigations were performed for different scenarios of changes in the power network parameters and control options of the PST. This allowed determining the desired functionality and structure of the automation system for selecting an optimal tap of the PST before its switching-on. The developed automation system is based on synchronous measurements, and this represents a novel implementation of such measurements. Verification simulation studies indicate that the proposed concept achieves the stated objectives. It is expected that the practical application of this automation system can resolve the transient overcurrent in the adjoining network components arising from PST switching. Overall this will enable significant minimization of negative effects of PST switching-on the power network operating conditions.

This publication discusses the risks of further use of classical overcurrent protections in modern power systems. The increasing penetration of renewable energy sources has caused a lot of challenges, among other things, the development of energy communities that balance local generation and consumption. Usually the interconnection line between the energy community and power systems are only used to balance the shortage or overflow of energy. As a result, most of the time these connections can be low loaded. Such a state can cause incorrect operation of power system protection approached, because the current level values are smaller than the required activation level for the protections. This article presents the potential incorrect operation of digital power system protection with overcurrent function. The obtained simulation results clearly show that the correctness of protection operation is strongly dependent on the level load of lines and the parameters and structure of the protection decision algorithms. These problems occur during low load line periods because these were not taken into account during the classical digital protection design stage. In the future this can cause problems with the fulfillment of the basic protection requirements of stability, speed, sensitivity. This publication suggests extra problems for power system protection research.

The observed development of offshore wind farms has resulted in an increasing presence of long extra-high voltage cables, with lengths ranging from 10 to 200 km. These cable lines are compensated for by a shunt reactor(s). The transient states that accompany switching operations, in this type of line, cause a number of challenges. There are slightly different and more dangerous phenomena than in classic uncompensated lines. One such phenomenon is the zero-missing phenomenon. The most effective methods for mitigating these phenomena are still under investigation and comparison to identify the optimal countermeasures. Applying a single minimization countermeasure often leads to avoiding one phenomenon (e.g., zero-missing phenomenon) while enhancing another (e.g., switching overvoltages). This can challenge designers, as they must consider the trade-offs between these competing objectives. The added value of this article is an analysis of the impact of the compensation level and its distribution (shunt reactor(s) location) in the offshore wind farm power export systems on zero-missing phenomenon and switching overvoltages. These analyses are supported by simulation cases mapping the case of the Polish power system. The results of the presented analysis are very important in light of a dynamic development of offshore wind farms and may be utilized by designers of power export systems, and can mitigate the significant risks occurring in such systems during energization cable lines.

The paper presents an innovative concept of the new area measuring algorithm and new area decision algorithm for power lines' distance protection. These algorithms improve the operating conditions of the distance protection. The primary purpose of the new measuring algorithm is correct the short-circuit impedance calculation. The purpose of the new decision algorithm is correct identify of the line operating conditions. For the investigation of classic and proposed new distance protections, a test power network containing the accurate model of the distance protection was developed. Verification simulation studies indicate that the proposed concept achieves the stated objectives. It is expected that the practical application of these new algorithms will enable significant minimization faulty operation of classic distance protection.