Electric Power Systems

Requirements:

There are no special requirements applied to this subject because it belongs to the first term. However, students should preferably possess knowledge of three-phase systems and phasors, differential equations, matrix algebra, computer programming, and a basic understanding of electrical machines and transformers.

The teaching methodologies, that promote active and collaborative learning, follow a temporal sequence that enables students to acquire theoretical concepts, solve a set of exercises and carry out practical case studies. The numbers of hours assigned to this subject are divided in “Presential work” and “Non-presential work”. The “Presential work” hours are divided in lectures, class practice, laboratory and evaluation sessions.

Competences and Learning Outcomes

This course provides students with skills related to the operation electric power systems as well as a comprehensive view of all the problems and tasks involved. Modern electric power systems are large, widely interconnected, operate with restricted security margins and under more stressed conditions. The restructuring of the electric power industry has introduced a much more competitive environment, new economic and social constraints, that forced the electric utilities to operate their power networks closer to their physical and security limits. Furthermore, the integration of renewable energy sources into the electric power systems has become an important challenge for operating and controlling the networks safely and efficiently. Under such increasingly complex conditions, the planning, operation and maintenance of power systems has become a very important issue.
The main aims of this course unit include the following topics: to model major types of components used in electrical power systems, to demonstrate load flow concepts and to study system performance under different operating conditions, to analysis fault conditions including both balanced and unbalanced faults, to understand the use of sequence networks in the analysis of faults and unbalanced power system operation, to evaluate the electric power system dynamics and its stability, to acquire knowledge to analyse the security of an electrical power system and propose/implement measures to improve it, to understand the basics of power system protection systems. The laboratory will be of a problem solving nature and will involve the solution of network problems using computer simulation and analysis software. This subject is related with the “Distribution Systems” subject in the same term. This package of two subjects provides to the students a wide overview of how the power systems works, how they are operated and how must be designed and protected.

Competences and learning outcomes that the students are intended to reach through the oriented work in the subject:
• Project, design and management in the scope of the course topics.
• Writing, communicating and presenting scientific documents to specialists, within the scope of the contents of the electric power systems subject.
• Identify, formulate and solve engineering problems.
• Understanding of the importance and the area of utilization of electrical power systems for generation, transmission and distribution of electrical energy.
• Identification of the main characteristics, design strategies and the constructive elements and materials of the Electrical Power Systems.
• Ability to understand the basics of the dynamic modelling of electrical power systems.
• Understanding the relevance of the control systems and monitoring in electrical power systems.
• Develop analytical skills needed for modelling the different components of an electrical power systems and to perform power flows studies.
• Understand the operation of the electrical power systems protection system and the equipment used.
• Design and conduct experiments and to analyse and interpret data.

Contents of the subject:

• Power systems basic concepts and models
− Structure of power systems
− Conventional sources of electric energy
− Renewable energy sources
− Distributed and dispersed generation
− Environmental aspects of electric energy generation
− Electric energy markets
− Electrical Power System Models: Generators, Transformers, Lines and Loads

• Power flow analysis
− Network model formulation
− Formation of bus admittance matrix
− Power flow problem formulation
− Power flow DC method
− Gauss-Seidel method
− Newton-Raphson method
− Decoupled power flow methods
− Comparison of power flow methods
− Control of voltage profile

• Power systems security analysis
− An overview of security analysis
− Factors affecting power system security
− Detection of network problems
− Contingency analysis
− System reduction for contingency analysis and fault studies

• Short-circuit analysis
− Symmetrical fault analysis
− Systematic fault analysis using bus impedance matrix
− Symmetrical components
− Construction of sequence networks of a power system
− Methods for measurement of symmetrical components
− Unsymmetrical fault analysis
− Symmetrical component analysis of unsymmetrical faults
− Bus impedance matrix method for analysis of unsymmetrical shunt faults
− Limitation of short-circuit currents

• Power systems protection
− Protection concepts
− Protective devices and controls, transmission protection, apparatus protection
− System aspects of protective systems

• Power system operation
− Generation control
− Voltage control
− Energy management systems
− Renewable generation

• Power systems dynamics and stability
− Steady state stability
− Transient stability
− Equal area criterion
− Numerical solution of swing equation
− Multimachine stability
− Factors affecting transient stability
− Voltage stability
− Comparison of angle and voltage stability

NAO