Calculation of relay protection (RP) settings ensuring its adequate functioning under specific operating conditions is extremely difficult task. The main prerequisite for solving this problem is availability of a detailed analysis of functioning of key elements of RPs schemes in the specific conditions of its operation. That is possible to do with adequate RPs mathematical models and modern EPS simulators. Based on developed by authors approach for detailed RPs simulation the models of the whole circuit of measuring part (MP) of numerical transformer differential protection were developed for different types of auxiliary transformers and low-pass filters. A comparative numerical analysis of its impact on the primary signal processing is carried out, including taking into account the magnetization current transformers. Summarizing, the theoretical and practical studies presented in the article allows formulating requirements for RPs’ detailed mathematical models, which will be used in the further research.
Słowa kluczowe: mathematical simulation, flow graph, settings, relay protection.
W artykule analizoano warunki prawidłowej pracy cyfrowego zabezpieczenia pracy transformatora. W tym celu opracowano model matematyczny układu zabezpieczającego ze szczególnym uwzględnieniem pracy filtru. Przeprowadzono symulacje dla różnych typów zewnętrznego transformatora i filtru dolnoprzepustowego.
Keywords: cyfrowe różnicowe zabezpieczenie transformatora, model matematyczny.
The well-known fact is the rapid growth of energy consumption in the world. Over the past 15 years, the increase was approximately 35-40%  and there are no prerequisites for reducing these numbers. Thus, the buildup of generated capacities will also continue. As a result, the modern electric power system (EPS), which already is a complex, dynamic and nonlinear system, will become even more complicated. The situation is aggravated by increasing the share of distributed generation and penetration of renewable energy sources . In accordance with , the total generated power of wind and solar energy sources has increased by more than 30% over the past 15 years. Protection of EPS due to these changes becomes extremely difficult and urgent task. According to the statistics , one of the main causes of severe accidents in the world is incorrect actions of relay protection (RP) and automation. As for the specific reasons, approximately 20% of the incorrect actions are associated with errors in the schemes and settings, which are connected with discrepancy of protection settings and real operating conditions. This problem and factors determining it are considered by the authors in . An obvious condition for solving the problem is possibility of a detailed analysis of operation of RP devices key elements in its specific regimes [5, 6]. This will allow to reliably estimate the processes in the protected objects, to evaluate the processing error of instrument transformers (IT) - current transformers (CT) and potential transformers (PT), as well as RP elements, and also to determine the parameters of adequate RP settings. The RPs detailed mathematical models reproducing the entire set of elements, including CTs and PTs, ensure this possibility. The main demotivator for creating such models for a long time was the lack of tools for complete and reliable EPS simulation. That is determined by the adequacy of the applied math [...]
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