M6

Power Quality Training Courses

Earthing

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Module 6 Earthing

1 INTRODUCTION The aim of this module is to provide the user a detailed overview of earthing system design related problems. The course gives an overview of the requirements of the earthing system and introduces the principle of systematic approach to its design. After an introductive part dedicated to definitions and standards, the successive lessons deal with the design of the ground electrode system by suppying practical guidance on the design and calculation of ground electrodes. 1.1 General aims This module’s general aim is to provide the attendants the basic knowledge about earthing, and some tools for the design of earthing systems. The aim is achieved through 6 didactic sections, as follows: − Section 1: Basic definitions, standards; − Section 2: Earth resistivity; − Section 3: Electrical properties of earth electrodes; − Section 4: Typical constructions of earth electrodes; − Section 5: Durability of earth electrodes; − Section 6: Measurements. − 1.2 Target groups This module’s target group includes: designers, experts, installers, and all those who wish to expand their knowledge in earthing systems. 2 SPECIFIC AIMS AND TOPICS The pathway of learning consists of a 2 days course, divided in sections (with different duration), with these contents and related aims.

Contents Aims

Contents Aims

1st day Introduction: basic definitions, standards, earth resistivity, electrical properties of earth electrodes. Introduce the basic knowledge related to earthing (definitions, standards, related problems, ground resistivity,ecc…). 2nd day Typical constructions of the earth electrodes, durability of the earth electrodes, Measurements. Provide information on constructive aspects, to give a practical guidance on the design and calculation of earthing systems. The last section of the course will be dedicated to the key problem of measurements.

Below there’s a detailed overview of the course contents.

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2.1

Pathway of learning flow chart Time progression (hours)

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COURSE DETAILED PROGRAM

General notes: − each day there will be one coffee break (30 mins) which will divide the lesson in two parts no longer than 2,5 hours; − at the beginning of the course the lecturer will explain course aims and at the end he will verify their fulfilment through a knowledge test; − the course will be divided in theoretical and practical sections; − at the end of the lessons, a user satisfaction survey will help the lecturer in monitoring the course quality.

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First day: 30 mins

Participants registration and course introduction

60 mins

Section 1: Basic definitions, standards − Definitions (Earthing or earthing system, Earth electrode, Earthing conductor, Earth surface potential, etc…) − Standards (National and International) Modality: Lesson

90 mins

Section 2: Ground resistivity − Soil resistivity − influence of the soil temperature − influence of the soil humidity Modality: Lesson

30 mins

Coffe break

90 mins

Section 3: Electrical properties of the earth electrodes − resistance − impedance − potential distribution − properties at lightning currents Modality: Lesson and discussion

Second day: 90 mins

Section 4: Typical constructions − earth electrodes − vertical electrodes − horizontal electrodes − natural earth electrodes Modality: Lesson and discussion

60 mins

Section 5: Durability of the earth electrodes − corrosion in the soil (chemical, from DC currents and galvanic) − minimum cross section of the earth electrodes − earth electrodes materials Modality: Lesson and practical training

30 mins

Coffe break

90 mins

Section 6: Measurements − measuring of the soil resistivity − measuring of the earth resistance (impedance) − measuring of the potential distribution Modality: Lesson and practical training

60 mins

Final discussion; end of the course; user’s satisfaction questionnaire; Confirmations of attendance

4 TEACHING METHODS Teaching methods are summarized in three main moments: www.lpqi.org

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− − −

knowledge transfer (Lesson) topics exposure by the lecturer with the help of slides and eventually other electronic tools (animations, data sheets, didactic movies…); deepening/learning verification (Discussion) general discussion stimulated by the lecturer (also during the lesson) to verify knowledge transfer and to eventually deepen particular topics; practical training (and eventually laboratory activities) group work (~ 6 persons/group) for topics deepening, practical problems solution and case studies overview under the supervision of the lecturer.

During all the sections, the lecturer will always attend, with teaching and/or activity coordination duty. 5 DIDACTIC MATERIAL AND TOOLS The didactic tools which will be used by the lecturers will be: − Blackboard − Video-projector − Notebook − Microphone The lecture room will be suitable to allow the use of all the above listed didactic tools and to enable group work for the attendants. Each user will receive, during the registration, a folder containing: − course program; − lecture notes containing all or part of the lecture slides; − LPQIVES knowledge database access personal key. All this didactic material, and eventually some additional electronic tools, will be available also in electronic format at: http://lpqi.org/custom/1036/ The folder will also include a user satisfaction questionnaire and a knowledge test (which will be both filled and submitted at the end of the course). 6 EXISTING KNOWLEDGE REQUIREMENTS The user’s existing knowledge should include: Topic

Basic

Mathematical analysis Electrical engineering Electrical circuits Power systems Power quality

Level Medium • •

High

• • •

7 ACQUIRED COURSE KNOWLEDGE REQUIREMENTS At the end of this course the user will have learned the basic aspects related to earthing (definitions, standards, related problems, ground resistivity, electrodes) along with some practical informations and tools on earthing system design and on the measurements of the related parameters.

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ANNEXES - MIDAS REPORT

Publication REP-00112, 2000, Equipotentiality and grounding, Presentation This paper explains equipotentiality and how it provides protection against electric shock. This paper also describes the grounding circuit for the various power distribution systems. Finally, this paper shows the effect of the product grounding resistance on the voltage of accessible parts, and validates the value required by various safety standards.

REP-00125, 2002, Specification guidelines to improve power quality immunity and reduce plant operating costs, Paper There are many useful IEEE and IEC standards that support the design of chemical and petrochemical plants. This article brings relevant Power Quality standards information together and provides recommendations in areas not yet covered in current standards. Circuit configurations for cost saving solutions are provided.

REP-00029, 2002, 6-5-4 EMC in large buildings, Application Note EMC strategy for buildings This document presents the basic concept for successful EMC of a facility in detail, including measures relating to the technology of buildings. EMC definitely includes classic lightning protection, but that matter is treated only marginally here. The individual measures of the basic concept can be implemented both in new facilities and to some extent also, with certain deletions, in existing facilities. Subjects: - The problem - General information - EMC strategy for buildings: Building shielding Potential equalisation Connections outside the buildings - EMC-appropriate facility design Fundamentals Cable connections between buildings Treatment of cable shielding Earthing low-voltage power lines Functional potential equalisation of electronics systems Designing electronics and control cabinets Lightning current and surge arresters

REP-00142, 2002, EARTHING IN INFORMATION TECHNOLOGY, Paper Good practice earthing of IT devices

REP-00060, 2003, Earthing requirements in modern electrical installations, Application note In recent years, Power Quality and EMC add new dimensions to the discussion on earthing, which require a different (systems) design approach in new installations, while causing severe problems in existing installations. Installation codes do not yet follow required design practice. Solutions are proposed for providing, in the initial design stage or as a continuous refurbishment, a low impedance path to earth over a practical range of frequencies. Leakage currents and corrosion in existing installations are discussed. As practical case studies, two site surveys are discussed.

REP-00073, 2003, Earthing in information technology, Application note Supplying power to IT equipment requires a special earthing system. The problem is the relatively high leakage current, caused mainly by the high operating frequency of IT equipment. The regulations described in the paper enable to eliminate negative effects of leakage current in various low-voltage systems. In order to choose a solution, an exact analysis of the specific character and operation parameters of the used IT equipment is required.

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REP-00085, 2003, Earthing systems in LV - ect 172, Application note Earthing systems (TN, TT, IT) and protection of persons, hazards of insulation faults, influences of MV on LV, choice of switchgear depending on the earthing system, unavailability of electrical power.

REP-00086, 2003, Earthing systems worldwide and evolutions - ect 173, Application note Historical review of the origins of earthing systems, practices in some countries, evolutions and choices of earthing systems.

REP-00089, 2003, The IT earthing system (unearthed neutral) in LV - ect 178, Application note Advantages and areas of application of the IT earthing system, first-fault situation, double-fault situation, surge limiters.

REP-00094, 2003, Neutral earthing in an industrial HV network - ect 62, Application note Requirements imposed by the different parameters of the installation (overvoltages, network, receivers), calculation of fault currents, protection methods.

REP-00097, 2003, Disturbances in electronic systems and earthing systems - ect 177, Application note Disturbance found in LV installations originating from outside and inside the LV network, advantages and disadvantages of earthing systems in terms of the coexistence of electrical and electronic systems.

REP-00030, 2003, 6-5-8 Designing low voltage supply systems for electromagnetic compatibility. Increasing protection by improved earthing, Application Note TNS systems and EMC The basis for ensuring electromagnetic compatibility in buildings and facilities is an earthing and equipotential bonding system, free of operating current. The indicated measures must be taken into account and coordinated with the safety requirements of IEC 60364, but setting up low voltage supply systems for proper electromagnetic compatibility involves more than earthing for voltage protection in accordance to the standards. Subjects: - The advantages of the TN-S system - Line frequency magnetic fields in the TN system - Alternative supply of a consumer from two directions - Concentric earth wire - Leakage currents from filters - Residual current devices (RCD)

REP-00027, 2003, 6-2-1 Measurement guide to earthing systems - measurement of the earth-electrodes properties, Application Note Application Guide about measuring earthing resistance Subjects: - Basic concepts and requirements - Commonly used methods of measuring the earthing resistance - Methods for testing the substations earth-electrode systems

REP-00025, 2003, 6-0-0 Stray alternating and direct currents in protective earth conductors and in building earthing systems - a problem with potentially catastrophic consequenc, Application Note In this article we address the special risks that can arise in TN-C and TN-C-S power systems when stray currents arise in electrically conductive structural elements within a building, and we discuss the various remedial measures available. (2 case studies)

REP-00052, 2003, 6-1 A system approach to earthing, Application note Purposes of earthing systems - link to EMC

REP-00053, 2003, 6-3-1 Earthing Systems - Fundamentals of Calculation and Design, Application note Definitions. Ground properties - resisistance.

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REP-00054, 2004, 6-5-1 Earthing systems - Basic Constructional Aspects, Application note Design and application of earthing systems and particularly earthing electrodes

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