• Book Name: Electrical Power System Essentials By Pieter Schavemaker and Lou Van der Sluis
• Author: Pieter Schavemaker and Lou Van der Sluis
• Pages: 339
• Size: 8 MB

In the field of power system analysis, an extensive amount of high-quality literature is available. Most of these textbooks follow more or less the same line and cover the same topics. This book differs from existing materials because the (steady-state) modeling of the power system components is covered in appendices. Therefore, the focus in the chapters itself is not on the modeling, but on the structure, functioning, and organization of the power system. The appendices contribute to the book by offering material that is not an integral part of the main text, but supports it, enhances it and as such is an integral part of the book. The following is a short summary of the contents of the chapters and the appendices.

Chapter 1 (Introduction to Power System Analysis) This first chapter describes the scope of the material, and is an introduction to the steady-state analysis of power systems. Questions like ‘why AC’, ‘why 50 or 60 Hz’, ‘why sinusoidally shaped AC’, ‘why a three-phase system’ are addressed. The basics for a steady-state analysis of balanced three-phase power systems are outlined, such as: phasors, single-line diagrams, active power, reactive power, complex power, power factor, and per-unit normalization.

Chapter 2 (The Generation of Electric Energy) The conversion from a primary source of energy to electrical energy is the topic of Chapter 2.The primary source of energy can be fossil fuels such as gas, oil and coal or uranium, but can come from renewable sources as well: wind energy, hydropower, solar power, geothermal power. In order to understand the nature of a thermal power plant, which is still the main source of power in the system, the principals of thermodynamics are briefly discussed. The final conversion from mechanical energy to electrical energy is achieved by the synchronous machine. The coupling of the machine with the grid and the actual power injection is analyzed.

Chapter 3 (The Transmission of Electric Energy) The transmission and distribution network is formed by the overhead lines, the underground cables, the transformers and the substations between the points of power injection and power consumption. Various substation concepts are presented, together with substation components and the protection installed. The transformers, overhead transmission lines, and underground cables are then considered in more detail. The transformer design, possible phase shift, and specific properties due to the magnetic core are highlighted. As overhead transmission lines are the most visible part of the power system, they are discussed from the point of view of what may be seen and why it is like that. The underground cables are also considered, contrasting them with overhead transmission.

Chapter 4 (The Utilization of Electric Energy) The power system is designed and arranged in such a way that demand may be fulfilled: consumers are supplied with the requested amount of active and reactive power at constant frequency and with a constant voltage. A load actually transforms the AC electrical energy into another form of energy. The focus in this chapter is on the various types of loads that transform the AC electrical energy into: mechanical energy (synchronous and induction motors), light, heat,DC electrical energy (rectifiers), and chemical energy.After that, the individual loads in the system are clustered and classified as grid users according to three categories: residential loads (mostly single-phase loads), commercial and industrial loads (often three-phase loads), and electric railways (either DC or single-phase AC).

Chapter 5 (Power System Control) Continuous control actions are necessary in the system for the control of the voltage, to maintain the balance between the amount of generated and consumed electricity and to keep the system frequency at either 50 Hz or 60 Hz. It is demonstrated that, in transmission networks, there is more or less a ‘decoupling’ between the active power and the voltage angles on one side and the reactive power and voltage magnitudes on the other, which is the basis for the control.The power balance is maintained (primary control), and the system frequency deviation minimized (secondary control), by controlling the active power output of the generators. Voltage is controlled locally either at generator buses by adjusting the generator voltage control or at fixed points in the system where tap-changing transformers, capacitor banks or other reactive power consumers/producers are connected. FACTS-devices (Flexible AC Transmission Systems) are large power-electronic devices; they are operated in a shunt configuration for reactive power and voltage control, or they are connected in series to control the power flow.

Chapter 6 (Energy Management Systems) In the control centre, the transmission and distribution of electrical energy are monitored, coordinated and controlled. The Energy Management System (EMS) is the interface between the operator and the actual power system. The SCADA (Supervisory Control and Data Acquisition) system collects real-time measured data from the system and presents it to the computer screen of the operator, and it sends control signals from the control centre to the actual components in the network. The EMS is in fact an extension of the basic functionality of the SCADA system and includes tools for the analysis and the optimal operation of the power system. The state estimator serves as a ‘filter’ for the collected measurement data; it determines the state of the power system that matches best with the available measurements. This is necessary input for other analysis programs in the EMS, like the load flow or power flow, and the optimal power flow. The load flow computation is one of the most important power system computations, giving us insight into the steady-state behavior of the power system. Therefore, besides the well-known Newton-Raphson load flow, a decoupled load flow and the DC load flow are also presented.

Chapter 7 (Electricity Markets) At a broad conceptual level, there exists such a thing as a ‘commonmarket model’ that provides for both spot market trading coordinated by a grid/market operator and for bilateral contract arrangements scheduled through the same entity. The spot market is based on a two-sided auction model: both the supply and demand bids are sent to the power exchange. Market equilibrium occurs when the economic balance among all participants is satisfied and the benefits for society, called ‘the social welfare’, are at their maximum value. The power system is a large interconnected system, so that multiplemarket areas are physically interconnected with each other: this facilitates the export of electricity from low-price areas to high-price areas.

Chapter 8 (Future Power Systems) In this chapter some developments, originating from the complex technological-ecologicalsociological and political playing field and their possible consequences on the power system, are highlighted. A large-scale implementation of electricity generation based on renewable sources, for example, will cause structural changes in the existing distribution and transmission networks. Many of these units are decentralized generation units, rather small-scale units that are connected to the distribution networks often by means of a power-electronic interface. A transition from the current ‘vertically operated power system’, into a ‘horizontally operated power system’ in the future is not unlikely.Energy storage can be applied to level out large power fluctuations when the power is generated by renewable energy sources, driven by intermittent primary energy. The complexity of the system increases because of the use of FACTS devices, power-electronic interfaces, intermittent power production and so on. Chaotic phenomena are likely to occur in the near future and large system blackouts will probably happen more often.