Practical Power System and Protective Relays Commissioning

Omar Salah Elsayed Atwa

• Publisher: Academic Press
• Year: 2019
• ISBN:
  9780128173121
• Topic: Technik & Maschinenbau
• Subtopic: Elektrotechnik & Telekommunikation

Practical Power System and Protective Relays Commissioning is a unique collection of the most important developments in the field of power system setup. It includes simple explanations and cost affordable models for operating engineers. The book explains the theory of power system components in a simple, clear method that also shows how to apply different commissioning tests for different protective relays. The book discusses scheduling for substation commissioning and how to manage available resources to efficiently complete projects on budget and with optimal use of resources.

• Explains the theory of power system components and how to set the different types of relays
• Discusses the time schedule for substation commissioning and how to manage available resources and cost implications
• Details worked examples and illustrates best practices

Chapter 1

Power System Elements

Abstract

This chapter defines the elements of a power system and shows how it is connected to create a system. It also discusses IEEE device numbers and the functions of switchgear apparatus symbols.

Keywords

Power system; generation; transmission system; distribution system; loads; system voltages; power system components; IEEE device numbers; functions of switchgear symbols

1.1 Introduction

A power system consists of a group of elements working together, including generation, transmission, distribution, and loads. Each of these are discussed in the following sections.

1.2 Overview of a Power System

1.2.1 Generation of Power

Power generation converts energy from one form to another. Examples are:

1. 1. Thermal generating stations that use fuels such as coal, oil, and gas that are burnt to generate electricity.
2. 2. Hydro generating stations that depend on water flow through a turbine to drive the generator.
3. 3. Nuclear generation stations that depend on uranium to generate electricity (nuclear fuel).

1.2.2 Transmission System

A transmission system is a network of overhead lines, underground cables, and transformers that transfer generated power in high voltage levels to loads.

High voltage levels are used to reduce the losses in the system during power transfer between each end of the transmission line.

1.2.3 Distribution System

A distribution system is a network of overhead transmission lines, underground cables, and transformers that carry small amounts of power to loads in medium and low voltage levels.

1.2.4 Loads

Loads are defined as items that consume electricity, for example, homes and factories.

1.3 System Voltages

Voltages differ from country to country, however, a general classification is:

• Generation voltage levels range from 12 to 33 kV.
• Transmission voltage levels range from 110 to 800 kV.
• Distribution voltage levels range from 4 to 35 kV.

1.4 Power System Components

A power system is made up of multiple components. These are:

Generators that generate electrical power.

Transformers that change voltage levels as per system requirements.

Circuit breakers that open and close the power circuits under normal and abnormal conditions.

Shunt reactors and capacitors that are used for system compensation for reactive power in transmission lines.

Surge arresters are used for protecting the primary system from overvoltages.

Protective relays are used to detect any faults in the system and to trip the circuit breakers to isolate the faulty part in the power system to keep other parts of the system healthy and working in normal condition.

Substations are nodes of several transmission lines or distribution lines with power transformers.

Buses are heavy conductors that collect power and distribute it to the different system components.

These are all shown in the simplified power system shown in Fig. 1.1.

Figure 1.1 Simple power system.

1.5 IEEE Device Numbers and Functions for Switchgear Apparatus

The devices in switching equipment are referred to by numbers, according to the functions they perform. These numbers are based on a system which has been adopted as standard for automatic switchgear by the Institute of Electrical and Electronics Engineers (IEEE). This system is used on connection diagrams, in instruction books, and in specifications. The standard numbers referring to device functions in switchgear components are as follows.

32 Directional power relay

21 Distance relay

25 Synchronizing or synchrocheck device

27 Under voltage relay

37 Under current or under power relay

40 Field relay

41 Field circuit breaker

42 Running circuit breaker

46 Reverse phase or phase–balance current relay

47 Phase–sequence voltage relay

49 Machine or transformer thermal relay

50 Instantaneous overcurrent or rate of rise relay

51 AC time overcurrent relay

52 AC circuit breakers

55 Power factor...