Power Systems Earthing | An Introduction to Substation and Electrical Equipment Protection

Published 31 Oct 2023

Power Systems Earthing | Electrode System

Power Earthing Systems

An earth electrode system, professionally designed by competent engineers, is essential to ensure the safety of personnel and protection of equipment from dangerous voltages in and around medium and high voltage (MV & HV) substations.

Earth Electrode Systems are a critical part of any electrical system and they are often seen as inert which may sometimes be dismissed as cost-saving or forgotten about until a later stage of the project – should these systems fail due to incompetent design or the use of cheap substandard components, the resulting events may be catastrophic or even lethal.

For instance this will carried out by competent and highly experienced electrical engineers and technicians. A.N Wallis are able to offer earth electrode system designs and associated testing services using the most up to date Earthing & Lightning Protection Equipment and design software CDEGS. 

CDEGS (Copper Earth Electrode Design) is now recognised as the industry standard earthing design analysis software in the UK and in many other parts of the world.

Power Earthing System products, manufactured by A.N Wallis and distributed by Thorne and Derrick from high conductivity copper to BS EN 13601 is installed to protect buildings, overhead lines and medium/high voltage substations (MV-HV) against potentially catastrophic damage that can be caused by a lightning strike resulting in short circuiting.

Power Earthing System | A.N Wallis

CDEGS

CDEGS (Current Distribution, Electromagnetic Fields, Grounding and Soil Structure Analysis) is a grounding (earthing) and electromagnetic analysis software package. It is dedicated to accurately analyse problems involving grounding, electromagnetic fields, electromagnetic interference including AC/DC .

This software allows to stress test designs and systems to evaluate performance under given conditions making the electrode systems safe.

using Substation Electrode Systems

A.N Wallis offer high specification test equipment to carry out soil resistivity testing. This helps it gain data from tried and tested methods. It is then analysed using CDEGS software to then produce a representative electrical equivalent soil resistivity model which can be used in the earthing design process.

As a result if this were to fail due to a incompetent design they would be running multiple tests to keep the workplace safe.

The Importance of Earth Bars For Power Earthing Systems

Substation earthing bars (LV HV) are used to marshall earth connections, connect copper earth rods or earth cable conductors using crimp lugs for terminations in substations, cable pits, feeder pillars and switchgear.

Earthing bars can be tinned and bases power coated to improve corrosion resistance. Bars are pre-drilled with cable connection holes with optional threads for installation ease. Manufactured from highest conductivity and quality copper to British Standards.

Full range of standard, single and twin link types for LV, MV & HV switchroom/substations. Customised to suit the earthing requirements of your project on short lead times.

Electrode Systems

To outline, the three main areas to analyse with any Earth Electrode system are:

– Touch, Step and Rise of Earth Potentials (RoEP). (These are also known as Earth Potential Rise (EPR or Ground Potential Rise (GPR).

Thorne & Derrick working with A.N Wallis will liaise with the DNO (Distribution Network Operator) or Electricity Supply Company on your behalf to gain all the required ‘Point of Connection’ data for your new electrical connection. Using the Soil Resistivity data, A.N Wallis produce a conceptual earth electrode system layout based on the existing plant layout drawings and analyse the associated voltage contours using either the MALT or MALZ module of the CDEGS software. Graphical plots are produced using the CDEGS software that visually identifies any ‘hot’ spots around the site that may need further design time.

MALT (CDEGS) assumes that the entire earth mat is at the same voltage, which is very dangerous to consider, particularly on more significant sites with low soil resistivity.

MALZ (CDEGS) does allow for voltage drops along conductors but does not account for inductive or capacitive effects between conductors.

These Touch, Step and Rise of Earth Potential levels are assessed, and only when they are within safe limits will A.N Wallis pass this design for construction.

Further calculations will be carried out to determine whether the site may influence other electrical installations under fault conditions and from that we can determine the site ITU (International Telecommunications Union) classification as either HOT or COLD.

Only once we have confidence that the design parameters are met, a full ‘for construction’ style drawing will be produced.

Key Benefits of Power Earthing Systems

• Provides safety for LV MV HV electrical sites
• Provides protection against dangerous voltage in and around substations
• Helps identify and document loss in Power Earthing Systems

Further Reading 

• Earth Bars | Wallis Earth Bar Software (WEBS)
• Correct Termination Of A Cable Lug Onto An Earth Bar | AN Wallis Guide
• AN Wallis Earthing & Lightning Protection | ECA Consultant & Specifier Associate

Earth Rods | Earth Tapes | Copper Earth Plates | Copper Earth Mats

THORNE & DERRICK are national distributors of LV, MV & HV Cable Installation, Jointing, Duct Sealing, Earthing & Electrical Equipment – we service UK and global businesses involved in cable installations, substation, overhead line and the installation of medium/high voltage cable joints and terminations at LV, 11kV, 33kV and HV.

Contact us for 3M Electrical, ABB, Alroc, AN Wallis, CATU Electrical, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.

Further Reading

• Earthing & Lightning Protection Systems – AN Wallis Handbook Size: 676.61 KB
• AN Wallis – Earthing & Lightning Protection Size: 3.88 MB