The cost-optimized generation and distribution of electrical energy is crucial for energy supply companies. One of the ways to achieve this goal is to improve the utilization of existing resources in terms of their loading and overall operating time and to reduce maintenance costs while maintaining a high level of security of supply. Modern monitoring and diagnostic techniques for electrical energy technology equipment can make a significant contribution to this.

The failure of high-voltage devices, e.g. bushings, cables and transformers, causes immense costs. As links between power plants and the electrical grid or power systems with different voltage levels, large transformers ensure the economical distribution of electrical energy. Their constant availability is therefore the basis for a reliable electrical energy supply.

A reduction in maintenance costs for electrical energy technology equipment could be achieved through a new maintenance and repair strategy. The use of modern monitoring and diagnostic techniques could lead to maintenance measures being carried out less prophylactically in the future and instead primarily based on technical necessity.

All physical and chemical effects that either cause a degradation of the device condition or that arise as a result of the degradation can be used to develop diagnostic techniques. Diagnostic techniques exist to detect thermally caused defects or to detect insulation damage, some of which have been in use on site or in the test field for years. Examples of this are gas-in-oil analysis or partial discharge measurement technology.

The goals for future diagnostics can be derived from the considerations so far:

• Social goals:
  • Reduction of risks to the environment through early detection of developing errors,
  • technical information through conscious action
  • Increasing safety for operating personnel,
  • reduced stress for staff.
• Economic goals:
  • Adaptive maintenance should lead to a reduction in operating costs,
  • Reduction of effort for maintenance personnel,
  • Business interruptions (for maintenance) can be planned better, with the aim of lower downtime costs, as well
  • Planning replacement investments based on the condition of the equipment (remaining lifespan can be estimated)
• Technical goals:
  • Optimization of resources and a system through better knowledge of the loads in operation,
  • Detection of sporadic malfunctions through continuous diagnostics, quantitative information about the development and behavior of certain measured variables, e.g. partial discharge, as well
  • Correlations of the measured variables with maintenance intervals and remaining service life.

An electrical grid component, such as a generator, transformer, coil, cable, can only be put into operation in the power system if it is correctly designed and functions correctly under all possible conditions in the system. Functional requirements for grid components must be identified in the first step, which can then be included in a specification. This starts with the correct identification of nominal sizes, especially nominal voltage and nominal power. All possible loads, such as asymmetrical loads, star point loads and harmonics, should then be precisely determined. Additional system requirements, particularly insulation coordination and short-circuit strength, play a large role in the design of each component.

Digitalization and climate change are creating new challenges in connection with the design of components. An example of this are the so-called environmental requirements, in particular temperature rise limits and cooling requirements.

Power system analyses are an essential part of the design of electrical grids. Calculations and simulations are performed to ensure that the electrical system, including system components, are correctly specified to perform as intended, withstand expected loads and be protected from failure.

International standards and local regulations are used as a basis for robust system designs. They include requirements and recommendations for protecting personnel and equipment, system behavior and device performance. Regulations and standards, together with device characteristics, form the basis for evaluating calculation and simulation results. Several software tools, e.g. PSS®SINCAL, PSS®NETOMAC, PSS®E, PSCAD, ETAP, PowerFactory, are used for power system analysis.

Power system analyses include: load flow analyses, short-circuit and fault analyses, protective device coordination and settings, harmonic analyses, dynamic and transient analyses, grounding studies, switching operations and insulation coordination.

The classic planning of electrical grids with their short- to long-term time horizon is already often implemented in an automation framework, so that a grid planner can initially take many planning premises into account independently of the network level:

• Use case-specific conditions, e.g.
• Request for connection from new consumers or new producers
• planned maintenance or switching measures
• different grid expansion variants as possible paths for development
• long-term forecasts on consumer, generation and storage development trajectories
• Operating scenarios based on standard profiles, predictions or measurement data
• optimized design parameters of operating resources and control devices
• different optimization goals with regard to voltage maintenance, loss minimization, degree of self-sufficiency, stability aspects and other criteria
• and other…

However, the result range of the combination of these planning premises is very large even when using a small part of the combinatorics and automatically forces the classic grid planner to reduce the considerations in terms of regional grid coverage, time horizon, consideration of operating scenarios and other dimensions. In this way, the grid planner manages to do justice to his tasks, but in view of the current developments, he is heavily burdened by the many parallel development strands and political and social demands. Additional colleagues take on some of the work, but the measures developed must be prioritized and synchronized with regard to the optimization goals.

However, fully automated grid planning, from which the overall optimized decisions regarding connection requests, investments and operating resource parameterization are directly derived, appears to be neither realistic nor expedient. The human or engineer factor will continue to play an important role in electrical power systems in the coming decades and the aim is not to replace them completely, but rather to enable them to carry out their tasks efficiently and well without being overloaded. Assisted grid planning offers the planner:

• Derivation of data sets and automated implementation of use cases,
• the efficient and high-performance consideration of the combinatorics of the planning premises,
• Development of suitable proposals for measures based on the experience of classic grid planning and new methods,
• effective verification of proposed measures and basis for decision-making for implementation,
• Synchronization of the measures to be implemented from multiple processes or regions

The assessment and decision-making authority remains with the grid planner; at the same time, the burden on the planner is significantly reduced and he can use his experience to make good decisions for the grid operators and the entire energy supply.

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