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Electrical Control & Protection Systems

This course introduces electrical control & protection systems which are a critical part of any electrical substation
Stephen Brooks
3,502 students enrolled
understand all of the key elements & principles of an electrical protection system
Draw what an electrical protection system looks like
Identify what primary, secondary and control equipments are
Explain how an overcurrent relay operates
Explain how an earth fault relay operates
Equip a protection panel and identify all of the main equipments
Use phasor diagrams to explain all of the key elements of three phase currents
Understand the requirements for a current transformer
Identify the requirements for a voltage transformer
Explain how a circuit breaker mechanism operates
Explain how the currents and voltages vary during all three phase fault conditions
Know the difference between a TP & TPN system

Electrical control & protection systems are a critical part of the distribution & transmission systems that feed power to our cities & industries.

The aim of this course is to introduce all of the basic principles associated with these complex systems. 

The course will go into detail for the following key topics :-

  • Introduce all of the key symbols, equipment’s and architecture of a substation protection system
  • Show the basic principles behind electrical protection philosophy
  • Look at three phase currents and see how they can be broken down into sequence components and harmonics.
  • Provide the basic principles behind current transformers, how they operate and need to be connected
  • Show how voltage transformers operate and introduce the key types
  • Go into detail on what happens when a fault occurs on the system
  • Look into circuit breaker control and protection systems and how they interact with the protection systems.
  • The main protection relay we will look at on this course is over protection. We go into detail on the basic and more advanced versions and show how this relay can be put to good use to provide great fault discrimination
  • Look at the different types of earth fault relays and see how they can be used to protect some key equipments

By the end of the course the student will be able to identify all of the key components of a protection & control system and understand how all of these components fit together to create a fully integrated system.

Electrical secondary protection systems


Electrical protection is a key element in all electrical systems, and ensures that the electrical network can operate safely and efficiently.

This first protection course is the first in a series and will introduce all of the basic principles of electrical protection systems,

The aim is that by the end of the course you have a good theoretical and practical understanding of electrical protection systems.

Protection system basics

In this lecture the student will learn about all of the symbols & terms that we will be using in this course, and introduces them to the differences between primary & secondary systems.

We will then look in detail at how the different elements of the secondary protection connect together.

Protection principles

After the first module in which we looked at the equipment's that we use for the protection system, in this module we look at the basic principles behind protection systems.

By the end of this section you will understand some of the principles behind protection systems including the importance of clearing a fault quickly whilst keeping as much of the healthy system connected as possible

Current transformer theory

In this next section we will look at one of the key primary equipment's that we use which are current transformers.

We will show all of their key features and how they operate during normal and fault situations, this will allow you to understand all of the parameters that you will find on a CT rating plate.

Three phase currents

In this section we will look at three phase currents.

Before you can start designing a protection system you need to understand in detail how the electrical network behaves when it is operating normal, only then can you design a system that reacts quickly and decisively when things go wrong.

By the end of this section you will understand how the current vectors behave under normal conditions and how the current vectors can be analysed to obtain information to give us clues of a fault taking place.

Voltage Transformers

In this section we will look at the other main primary measuring device that we use, which are voltage transformers.

In the same way as we looked at current transformers we will learn how voltage transformers operate and how they should be connected to the secondary protection system.

Current transformer installation

In this next section we will leave the theory behind and start looking at the practical side of protection systems, by looking at how we use current transformers, connect them together and feed the protection and control circuits..

Electrical Faults

In this section we will start looking at the theory of secondary protection systems, by introducing some of the basic principles behind fault detection.

Our aim is to detect faults quickly and accurately so that we minimise the impact on the equipment and network, and keep as many customers connect as possible

This section shows what happens to the voltages and currents for each of the different types of fault.

Protection Panels & Wiring

In this module we will look in detail at protection panels & wiring.

These house all of the protection and control equipment's that we use, and it is interesting to study how they are constructed, and look at some of the equipment's that they contain, some of which only appears in protection systems

Circuit Breaker Controls

In this section we will look at circuit breaker controls.

Circuit breakers are the main device that we use to switch the electricity around the network and for disconnecting faults as they occur.

In this section we will see look at the different types of circuit breaker and how the secondary protection system interacts with the breaker controls circuits.

Overcurrent protection part 1

Welcome to the first module on overcurrent protection. Overcurrent protection is the most widely used protection device that we use on the distribution and transmission network and appears on the most simple and complicated systems.

In this module you will learn the basic principles behind instantaneous overcurrent protection and see how an overcurrent relay can be used to provide a basic overload function.

Overcurrent protection part 2

This is the second module on one of the most important protection relays that we use on the network, overcurrent protection

We will introduce you to some additional features that will improve how the relay reacts to faults, and provide better fault discrimination to keep as many of the customers connected as possible when something goes wrong with the network

Overcurrent protection part 3

In this section we will introduce some practical examples of how to use all of the available features of overcurrent relays.

It is obviously impossible to cover every single network configuration, but hopefully by the end of this section you will have learned some basic principles that can be applied to any situation.

Earth Fault Protection

Earth fault protection is one of the most widely used protection systems. 

In this module we will show how the earth fault relay works and how it can be connected to the current transformers to generate the current information that we need. We will then finish by introducing the earth fault connections required to protect a transformer from internal & external faults.

You can view and review the lecture materials indefinitely, like an on-demand channel.
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3 hours on-demand video
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