Steven McFadyen's Articles

Steven is a Chartered electrical engineering consultant with considerable experience on major internationally recognised and award winning projects in Europe, South East Asia, and the Middle East. His expertise has been called on for numerous technically challenging projects in power systems, airports, rail, mining, pharmaceutical, datacentre, and other industries.

IEC 60287 Current Capacity of Cables - An Introduction

IEC 60287 "Calculation of the continuous current rating of cables (100% load factor)" is the International Standard which defines the procedures and equations to be used in determining the current carry capacity of cable. The standard is applicable to all alternating current voltages and direct current cables up to 5kV.

This note will introduce the concepts adopted by the standard, provide some guidance on using the standard and direct the reader to further resources.

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Voltage Levels to IEC 60038

The standard aims to consolidate AC and traction voltages within the industry and defines the following bands:

  • band 1 - A.C. systems 100 V to 1000 V
  • band 2 - A.C and D.C traction systems
  • band 3 - A.C. systems above 1 kV to 35 kV
  • band 4 - A.C. systems above 35 kV to 230 kV
  • band 5 - A.C. systems above 245 kV

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DC Component of Asymmetrical Faults

The image (reproduced from IEC 60909) shows a typical fault in an ac system.  From the illustration it can seen that there is an initial dc component (id.c.).  This initial dc component decays over time, eventually reaching zero.  Addition of the dc component to the symmetrical short circuit current give the asymmetrical fault current.

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Understanding Circuit Breaker Markings

IEC 60947 is the circuit breaker standard and covers the marking of breakers in detail. Any manufacturer following this standard should comply with the markings.

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Power Transformers - An Introduction

One of the fundamental requirements of an alternating current distribution systems it to have the ability to change the magnitude of voltages.  It is more efficient to transmit power at high voltages over long distances, whereas it is safer and more practical to use a low voltage to drive appliances and equipment.   Transformers are used to achieve this. 

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Lithium Ion Battery

Over recent years the Lithium Ion battery has become popular in applications requiring high power densities with small weight and footprint.  Today Lithium Ion batteries are commonly found in mobile phones, portable electronics, power tools, electrically operated vehicles and military applications. In addition to high power densities, Lithium Ion batteries are chargeable and have no memory effect. Charge/discharge mechanism of a Lithium Ion battery Image Source: http://batteryuniversity.com Developed in the early 1970's  at Birmingham University in the UK, Lithium Ion batteries consist of a Lithium Metal Oxide positive electrode (cathode), carbon negative electrode (anode) and electrolyte of a lithium salt organic solution. During the discharge process, Lithium Ions move from the negative to the positive electrode, via the external circuit.   During the charging the process is reversed by applying an over voltage. The Lithium Metal Oxide cathode is constructed using various ...

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What is a rectifier transformer?

I've recently come across this question a couple times browsing the internet. Decided to give a quick answer here. A rectifier transformer is a transformer which includes diodes or thyristors in the same tank. Voltage regulation may also be included. Typically these are used for industrial processes which require a significant direct current (dc) supply. Typical processes would include dc traction, electrolysis, smelting operations, large variable speed drive trains, etc.

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How to refer fault levels across a transformer

Over the past year or so I've been involved in on going discussions related to referring fault levels from the secondary of a transformer to the primary side.  While this is easy for some people to grasp, for others it's not so straight forward.  Here is a brief explanation of how to do this.

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Electromagnetic Compatibility (EMC)

Electromagnetic compatibility (EMC) is the study of coordinating electromagnetic fields give off equipment, with the withstand (compatibility) of other equipment within the vicinity. In it's simplest form, we endeavour to ensure that the magnitude of any electromagnetic fields generated are less than the withstand level of adjacent equipment.

Within Europe there is the EMC directive (2004/108/EC), which is law in all European Countries.  Equipment which bears the CE mark has been certified to comply with the relevant standards.

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Power Factor

Power factor is the ratio between the real power (P in kW) and apparent power (S in kVA) drawn by an electrical load.

The reactive power (Q in kVAr) causes the real and apparent power to be displaced from each other. Reactive power provides the necessity for electric and magnetic fields to enable the power system to work.

In addition to being the ratio of real power to apparent power, the power factor can also be express as the cosine of the angle between the two.

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Resistors

Resistors are electronic components that oppose the flow of current.  Manufactured in various types and ranges they have a wide application to electronics. 

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9 power supply issues solved by using a UPS

Installation of a UPS can help in reducing problems due to issues with the power supply.  A lot of people relate this to nine key issues.  Depending on the type of UPS installed it is possible to resolve some or all of the above issues.  The simplest installation of an off-line UPS will resolve issues (1) to (3), while the installation of a full double conversion unit could potential resolve all issues. 

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Back to Basics - Ohm’s Law

Electrical engineering has a multitude of laws and theorems. It is fair to say the Ohm's Law is one of the more widely known; it not the most known. Developed...

Low Voltage Circuit Breakers

Circuit breakers are switching devices whose primary function is to isolate parts of an electrical distribution system in the even of abnormal conditions...

myElectrical - Cable Sizing Tool Upgrade

Our IEE cable sizing was wrote a few years ago and had become rough around the edges. I thought it was time to give the tool a service. Unfortunately when...

Periodic Electrical Installation Inspection – What to Inspect?

This is the second post in a series of two on periodic electrical inspections. In the first post, I discussed how often inspections should be carried out...

Electrical Engineering

Electrical engineering is a field that covers a wide variety of sub-fields, including electricity and electronics. It is a field that goes back to the...

Laplace Transform

Laplace transforms and their inverse are a mathematical technique which allows us to solve differential equations, by primarily using algebraic methods...

Why use catalogues

I'm a fan of using manufacturers catalogues. There are two main reasons for this. Firstly, if your involved in the purchase of equipment, you will likely...

HTML Symbol Entities

HTML supports a variety of entity symbols which can be entered using either numbers or an entity name.  The number or name is preceded by the ‘&’ sign...

Understanding LV Circuit Breaker Fault Ratings

I think this post is going to be helpful to several of our readers. While the IEC low voltage circuit breaker Standard [IEC 60947-2, Low voltage switchgear...

Electromechanical Relays

Electromechanical relays have been the traditional backbone of electrical protection systems.  While over recent years these have been replaced by microprocessor...

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