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Electrical Installation Regulations: Scope, Object, and Fundamental Principles, Lecture notes of Electrical Engineering

South Eastern University of Sri LankaElectrical Engineering

Course Materials of Electrical Installations

Typology: Lecture notes

2012/2013

Uploaded on 09/18/2023

iresha-dissanayake
iresha-dissanayake 🇱🇰

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ECX4234 – Session 3 – Scope, Object and Fundamental Principles
Lalith A. Samaliarachchi
Session 3
Scope, Object and Fundamental
Principles
Contents
3.1 The scope of the wiring regulations
3.2 The object of the regulations
3.3 Fundamental principles
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Download Electrical Installation Regulations: Scope, Object, and Fundamental Principles and more Lecture notes Electrical Engineering in PDF only on Docsity!

Lalith A. Samaliarachchi

Session 3

Scope, Object and Fundamental

Principles

Contents

3.1 The scope of the wiring regulations 3.2 The object of the regulations 3.3 Fundamental principles

Lalith A. Samaliarachchi

Aim

The aim of this session is to teach you the scope, object and the fundamental principles in an electrical installation.

Lalith A. Samaliarachchi

Introduction

In the previous session we learnt that the Part I of the Regulations gave the overriding requirements. What were they? They were the scope, object and the fundamental requirements of principles.

3.1 The scope of the wiring regulations

The Wiring Regulations, like any other design manual, has a scope. For example, it will not give any regulations as to the design of buildings, as this is completely outside its scope. Others may not be that obvious, so that chapter 11 of the Regulations specify its scope and exclusions. Regulation 110.1 states that these Regulations relate principally to the design, erection and verification of electrical installations such as those of:

  1. Residential premises
  2. Commercial premises
  3. Public premises
  4. Industrial premises
  5. Agricultural and horticultural premises
  6. Prefabricated buildings
  7. Caravans, Caravan parks and similar sites
  8. Construction sites, exhibitions, shows, fairgrounds and other installations for temporary purposes including professional stage and broadcast applications
  9. Marinas
  10. External lighting and similar installations
  11. Mobile or transportable units
  12. Photovoltaic systems
  13. Low voltage generator sets
  14. Highway equipment and street furniture. When you say “premises” it covers the land and all facilities including buildings belonging to it. The regulations include requirements for:
  15. Circuits supplied at nominal voltages up to and including 1000 V a.c. or 1500 V d.c. For a.c., the preferred frequencies which are taken into account in this standard are 50 Hz, 60 Hz, and 400 Hz. The use of other frequencies for special purposes is not excluded.
  16. Circuits, other than the internal wiring of apparatus, operating at voltages exceeding 1000V and derived from an installation having a voltage not exceeding 1000 V a.c., e.g. discharge lighting, electrostatic precipitators
  17. Any wiring systems and cables not specifically covered by the standards for appliances

Lalith A. Samaliarachchi

  1. All consumer installations external to buildings
  2. Fixed wiring for information and communication technology, signalling, control and the like (excluding internal wiring of equipments)
  3. The addition to or alteration to installations and also parts of the existing installations affected by the addition or alteration. In certain cases the above may need to be supplemented by the requirements or recommendations of other British or local established standards. Regulations 110.2 states that the Regulations do not apply to the following installations:
  4. Systems for the distribution of electricity to the public
  5. Railway traction equipment, rolling stock and signalling equipment
  6. Equipment of motor vehicles, except those to which the requirements of the Regulations concerning caravans or mobile units applicable
  7. Equipment on board ships
  8. Equipment of mobile and fixed offshore installations
  9. Equipment of aircrafts
  10. Those aspects of mines and quarries specially covered by statutory Regulations
  11. Radio interference suppressions equipment, except so far as it affects safety of the electrical installation
  12. Lighting protection of buildings
  13. Those aspects of lift installations

3.2 The object of the regulations

The object and Effects of the Regulations are specified in chapter 12. Regulation 120.1 states that the standard contains the rules for the design and erection of electrical installations so as to provide for safety and proper functioning for the intended use. Chapter 13 of this standard states the fundamental principles. However, it does not contain the detailed technical requirements which may be subject to modifications because of the technical developments. This standard sets out technical requirements intended to ensure that electrical installation confirm to the fundamental principles of Chapter 13, as follows: Part 3 Assessment of general characteristics Part 4 Protection for safety Part 5 Selection and erection of equipment Part 6 Inspection and testing Part 7 Special installations or locations

Lalith A. Samaliarachchi 131.2.1 Basic Protection (protection against direct contact) Persons and livestock shall be protected against dangers that may arise from contact with live parts of the installation. This protection can be achieved by one of the following methods:

  1. Preventing a current from passing through the body of any person or any livestock
  2. Limiting the current which can pass through a body to a non-hazardous value. 131.2.2 Fault protection (protection against indirect contact) Persons and livestock shall be protected against dangers that may arise from contact with exposed-conductive-parts during a fault. (mainly with regards to failure of basic insulation) This protection can be achieved by one of the following methods:
  3. Preventing a current resulting from a fault from passing through the body of any person or any livestock
  4. Limiting the magnitude of a current resulting from a fault, which can pass through a body, to a non hazardous value
  5. Limiting the duration of a current resulting from a fault, which can pass through a body, to a non hazardous period. In connection with fault protection, the application of the method of protective equipotential bonding is one of the important principles for safety. 131.3 Protection against thermal effects 131.3.1 The electrical installation shall be so arranged that the risk of ignition of flammable materials due to high temperature or electric arc is minimized. In addition, during normal operation of the electrical equipment, there shall be minimal risk of burns to persons or livestock. 131.3.2 Persons, fixed equipment and fixed materials adjacent to electrical equipment shall be protected against harmful effects of heat or thermal radiation emitted by electrical equipment, particularly the following consequences:
  6. Combustion, ignition, or degradation of materials
  7. Risk of burns
  8. Impairment of the safe function of installed equipment. Electrical equipment shall not present a fire hazard to adjacent materials. 131.4 Protection against overcurrent Persons or livestock shall be protected against injury, and property shall be protected against damage, due to excessive temperatures or electromechanical stresses caused by any overcurrents likely to arise in live conductors. Protection can be achieved by limiting the overcurrent to a safe value and/or duration.

Lalith A. Samaliarachchi 131.5 Protection against fault current Conductors other than live conductors, and any other parts intended to carry a fault current, shall be capable of carrying that current without attaining an excessive temperature. Electrical equipment, including conductors, shall be provided with mechanical protection against eletromechanical stresses of fault currents as necessary to prevent injury or damage to persons, livestock or property. For live conductors, compliance with Regulation 131.4 assures their protection against over-currents caused by faults. 131.6 Protection against voltage disturbances and measures against electromagnetic influences 131.6.1 Persons and livestock shall be protected against injury, and property shall be protected against any harmful effects, as a consequence of a fault between live parts of circuits supplied at different voltages, in accordance with Section 442. 131.6.2 Persons and livestock shall be protected against injury, and property shall be protected against damage, as a consequence of overvoltages such as those originating from atmospheric events or from switching, in accordance with Section 443. 131.6.3 Persons and livestock shall be protected against injury, and property shall be protected against damage, as a consequence of undervoltage and any subsequent voltage recovery, in accordance with section 445. 131.6.4 The installation shall have an adequate level of immunity against electromagnetic disturbances so as to function correctly in the specified environment. The installation design shall take into consideration the anticipated electromagnetic emissions, generated by the installation or the installed equipment, which shall be suitable for the current-using equipment used with, or connected to, the installation. 131.7 Protection against power supply interruption Where danger or damage is expected to arise due to an interruption of supply, suitable provisions shall be made in the installation or installed equipment. 131.8 Additions and alterations to an installation No addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributor, will be adequate for the altered circumstances. Furthermore, the earthing and bonding arrangements, if necessary for the protective measure applied for the safety of the addition or alteration, shall be adequate. 132 DESIGN

Lalith A. Samaliarachchi

  1. Loads to be expected on the various circuits
  2. Daily and yearly variation of demand
  3. Any special conditions, such as harmonics
  4. Requirements for control, signalling, communication and information technology, etc.
  5. Anticipated future demand if specified. 132.4 Electrcal supply systems for safety services or standby electrical supply systems Where a supply for safety services or standby electrical supply system is specified the following shall be determined:
  6. Characteristics of the supply
  7. Circuits to be supplied by the safety source. 132.5 Environmental conditions 132.5.1 Equipment likely to be exposed to weather, corrosive atmospheres or other adverse conditions, shall be so constructed or protected as may be necessary to prevent danger arising from such exposure. 132.5.2 Equipment in surroundings susceptible to risk of fire or explosion shall be so constructed or protected, and such other special precautions shall be taken, as to prevent, danger. 132.6 Cross-sectional area of conductors The cross-sectional area of conductors shall be determined for both normal operating conditions and, where appropriate, for fault conditions according to:
  8. The admissible maximum temperature
  9. The voltage drop limit
  10. The electromechanical stresses likely to occur due to short-circuit and earth fault currents
  11. Other mechanical stresses to which conductors are likely to be exposed
  12. The maximum impedance for operation of short-circuit and earth fault protection.
  13. The method of installation
  14. Harmonics
  15. Thermal insulation.

Lalith A. Samaliarachchi 132.7 Type of wiring and method of installation The choice of the type of wiring system and the method of installation shall include consideration of the following:

  1. The nature of the location
  2. The nature of the structure supporting the wiring
  3. Accessibility of wiring to persons and livestock
  4. Voltage
  5. The electromechanical stresses likely to occur due to short-circuit and earth fault currents
  6. Electromagnetic interference
  7. Other external influences (e.g. mechanical, thermal and those associated with fire) to which the wiring is likely to be exposed during the erection of the electrical installation or in service. 132.8 Protective equipment The characteristics of protective equipment shall be determined with respect to their function, including protection against the effects of:
  8. Over-current (overload, short-circuit)
  9. Earth fault current
  10. Overvoltage
  11. Undervoltage and no-voltage. The protective devices shall operate at values of current, voltage and time which are suitably related to the characteristics of the circuits and to the possibilities of danger. 132.9 Emergency control Where in case of danger there is the necessity for immediate interruption of supply, an interrupting device shall be installed in such a way that it can be easily recognised and effectively and rapidly operated. 132.10 Disconnecting devices Disconnecting devices shall be provided so as to permit disconnection of the electrical installation, circuits or individual items of equipment as required for operation, inspection, fault detection, testing, maintenance and repair. 132.11 Prevention of mutual detrimental influence

Lalith A. Samaliarachchi 133.1.2 Where there is no applicable standard, the item of equipment concerned shall be selected by special agreement between the person specifying the installation and the installer. 133.1.3 Where equipment to be used is not in accordance with Regulation 133.1.1 or is used outside the scope of its standard, the designer or other person responsible for specifying the installation shall confirm that the equipment provides at least the same degree of safety as that afforded by compliance with the Regulations. 133.2 Characteristics Every item of electrical equipment selected shall have suitable characteristics appropriate to the values and conditions on which the design of the electrical installation (see Section 132 of IEE Regulations) is based and shall, in particular, fulfil the requirements of Regulations 133.2.1 to 133.2.4. 133.2.1 Voltage Electrical equipment shall be suitable with respect to maximum steady-state voltage (rms value for a.c.) likely to be applied, as well as overvoltage likely to occur. For certain equipment, it may also be necessary to take account of the lowest voltage likely to occur. 133.2.2 Current Electrical equipment shall be selected with respect to the maximum steady current (rms value for a.c.) which it has to carry in normal service and with respect to the current likely to be carried in abnormal conditions and the period (e.g. operating time of protective devices, if any) during which it may be expected to flow. 133.2.3 Frequency Equipment shall be suitable for the frequencies likely to occur in the circuit. 133.2.4 Power Electrical equipment which is selected on the basis of its power characteristics shall be suitable for the duty demanded of the equipment, taking into account the load factor and the normal service conditions. 133.3 Conditions of installation Electrical equipment shall be selected so as to withstand safely the stresses, the environmental conditions (see Regulation 132.5) and the characteristics of its location. An item of equipment which does not by design have the properties corresponding to its location may be used where adequate further protection is provided as part of the completed electrical installations. 133.4 Prevention of harmful effects

Lalith A. Samaliarachchi All Electrical equipment shall be selected so that it will not cause harmful effects on other equipment or impair the supply during normal service, including switching operations. 134 ERECTION AND INITIAL VERIFICATION OF ELECTRICAL INSTALLATIONS 134.1 Erection 134.1.1 Good workmanship by competent persons or persons under their supervision and proper materials shall be used in the erection of the electrical installation. Electrical equipment shall be installed in accordance with the instruction provided by the manufacturer of the equipment. 134.1.2 The characteristics of the electrical equipment, as determined in accordance with Section 133, shall not be impaired by the process of erection. 134.1.3 Conductors shall be identified in accordance with Section 514. Where identification of terminals is necessary, they shall be identified in accordance with Section 514. 134.1.4 Every electrical joint and connection shall be of proper construction as regards conductance, insulation, mechanical strength and protection. 134.1.5 Electrical equipment shall be installed in such a manner that the design temperatures are not exceeded. 134.1.6 Electrical equipment likely to cause high temperatures or electric arcs shall be placed or guarded so as to minimise the risk of ignition of flammable materials. Where the temperature of an exposed part of electrical equipment is likely to cause injury to persons or livestock that part shall be so located or guarded as to prevent accidental contact therewith. 134.1.7 Where necessary for safety purposes, suitable warning signs and/or notices shall be provided. 134.2 Initial Verification 134.2.1 On completion of an installation or an addition or alteration to an installation, appropriate inspection and testing shall be carried out to verify so far as is reasonably practicable that the requirements of this standard have been met. Appropriate certification shall be issued in accordance with Section 631. 134.2.2 The designer of the installation shall make a recommendation for the interval to the first periodic inspection and test as detailed in Part 6. The requirement of Chapter 34 (maintainability) should be taken unto consideration. 135 PERIODIC INSPECTION AND TESTING