I.S. HD 637:1999

FOREWORD
1 SCOPE AND NORMATIVE REFERENCES
2 DEFINITIONS
   2.1 GENERAL DEFINITIONS
   2.2 INSTALLATIONS
   2.3 TYPES OF INSTALLATIONS
   2.4 SAFETY MEASURES AGAINST ELECTRIC SHOCK
   2.5 CLEARANCES
   2.6 CONTROL AND PROTECTION
   2.7 EARTHING
3 FUNDAMENTAL REQUIREMENTS
   3.1 ELECTRICAL REQUIREMENTS
        3.1.1 Methods of neutral earthing
        3.1.2 Voltage classification
        3.1.3 Current in normal operation
        3.1.4 Short circuit current
        3.1.5 Rated frequency
        3.1.6 Corona
   3.2 MECHANICAL REQUIREMENTS
        3.2.1 Tension load
        3.2.2 Erection load
        3.2.3 Ice load
        3.2.4 Wind load
        3.2.5 Switching forces
        3.2.6 Short-circuit forces
        3.2.7 Loss of conductor tension
        3.2.8 Vibration
        3.2.9 Dimensioning of supporting structures
   3.3 CLIMATIC AND ENVIRONMENTAL CONDITIONS
        3.3.1 Temperature
        3.3.2 Altitude and air pressure
        3.3.3 Humidity
        3.3.4 Precipitation
        3.3.5 Pollution
        3.3.6 Solar radiation
   3.4 SPECIAL REQUIREMENTS
        3.4.1 Installations at high altitudes
        3.4.2 Effects of small animals and microorganisms
        3.4.3 Noise level
        3.4.4 Effects of earthquakes
4 INSULATION
   4.1 SELECTION OF INSULATION LEVEL
   4.2 VERIFICATION OF WITHSTAND VALUES
   4.3 MINIMUM CLEARANCES OF LIVE PARTS
   4.4 MINIMUM CLEARANCES BETWEEN PARTS UNDER SPECIAL
        CONDITIONS
   4.5 TESTED CONNECTION ZONES
5 EQUIPMENT
   5.1 COMMON RULES
        5.1.1 General
        5.1.2 Installation
   5.2 SPECIFIC REQUIREMENTS
        5.2.1 Circuit-breakers, switch-disconnectors, fuses,
               fuse-switch disconnectors, contactors,
               disconnectors and earthing switches
        5.2.2 Power transformers and reactors
        5.2.3 Gas insulated metal-enclosed switchgear (GIS),
               metal-enclosed switchgear, insulation-enclosed
               switchgear and other prefabricated type-tested
               switchgear assemblies
        5.2.4 Instrument transformers
        5.2.5 Surge arresters
        5.2.6 Capacitors
        5.2.7 Line traps
        5.2.8 Insulators
        5.2.9 Insulated cables
        5.2.10 Conductors and accessories
        5.2.11 Rotating machines
        5.2.12 Static converters
6 INSTALLATIONS
   6.1 GENERAL REQUIREMENTS
        6.1.1 Circuit arrangement
        6.1.2 Documentation
        6.1.3 Transport routes
        6.1.4 Aisles and access areas
        6.1.5 Lighting
        6.1.6 Operational safety
        6.1.7 Labelling
   6.2 OPEN-TYPE OUTDOOR INSTALLATIONS
        6.2.1 Barrier clearances
        6.2.2 Obstacle clearances
        6.2.3 Boundary clearances
        6.2.4 Minimum height over access area
        6.2.5 Clearances to buildings
        6.2.6 External fences and access doors
   6.3 OPEN-TYPE INDOOR INSTALLATIONS
   6.4 INSTALLATION OF FACTORY-BUILT TYPE-TESTED
        ENCLOSED SWITCHGEAR
        6.4.1 General
        6.4.2 Additional requirements for gas-insulated
               metal-enclosed switchgear
   6.5 REQUIREMENTS FOR BUILDINGS
        6.5.1 Introduction
        6.5.2 Structural provisions
        6.5.3 Rooms for switchgear
        6.5.4 Service areas
        6.5.5 Doors
        6.5.6 Draining of dielectric fluids
        6.5.7 Air conditioning and ventilation
        6.5.8 Building which require special consideration
   6.6 HIGH-VOLTAGE/LOW-VOLTAGE PREFABRICATED SUBSTATIONS
   6.7 MAST POLE AND TOWER INSTALLATIONS
7 SAFETY MEASURES
   7.1 PROTECTION AGAINST DIRECT CONTACT
        7.1.1 General
        7.1.2 Measures for protection against direct
               contact
        7.1.3 Protection requirements
   7.2 MEANS TO PROTECT PERSONS IN CASE OF INDIRECT CURRENT
   7.3 MEANS TO PROTECT PERSONS WORKING ON ELECTRICAL
        INSTALLATIONS
        7.3.1 Equipment for isolating installations or
               apparatus
        7.3.2 Devices to prevent reclosing of isolating
               devices
        7.3.3 Devices for determining the de-energized
               state
        7.3.4 Devices for earthing and short-circuiting
        7.3.5 Equipment acting as barriers against
               adjacent live parts
        7.3.6 Storage of accident prevention equipment
   7.4 PROTECTION FROM DANGERS RESULTING FROM ARC FAULT
   7.5 PROTECTION AGAINST DIRECT LIGHTNING STROKES
   7.6 PROTECTION AGAINST FIRE
        7.6.1 General
        7.6.2 Transformers, reactors
        7.6.3 Cables and flexible cords
        7.6.4 Other equipment with flammable liquid
   7.7 PROTECTION AGAINST LEAKAGE OF INSULATING LIQUID AND
        SF[6]
        7.7.1 Insulating liquid leakage and subsoil water
               protection
        7.7.2 SF[6]-leakage (new SF[6])
        7.7.3 Failure with loss of SF[6] and its
               decomposition products
   7.8 IDENTIFICATION AND MARKING
        7.8.1 General
        7.8.2 Information plates and warning plates
        7.8.3 Electrical hazard warning
        7.8.4 Installations with incorporated capacitors
        7.8.5 Emergency signs for emergency exits
8 AUXILIARY INSTALLATIONS AND CONTROL SYSTEMS
   8.1 MONITORING AND CONTROL SYSTEMS
   8.2 DC AND AC SUPPLY CIRCUITS
        8.2.1 AC supply
        8.2.2 DC supply
   8.3 COMPRESSED AIR SYSTEMS
   8.4 SF[6] GAS HANDLING PLANTS
   8.5 BASIC RULES FOR ELECTO-MAGNETIC COMPATIBILITY OF
        CONTROL SYSTEMS
        8.5.1 Electrical noise sources in high voltage
               installations
        8.5.2 Measures to be taken to reduce the effects
               of high frequency interference
        8.5.3 Measures to be taken to reduce the effects
               of low frequency interference
        8.5.4 Measures related to the selection of
               equipment
        8.5.5 Other possible measures to reduce the
               effects of interference
9 EARTHING SYSTEMS
   9.1 PURPOSE
   9.2 DIMENSIONING OF EARTHING SYSTEMS AT POWER FREQUENCY
        9.2.1 General
        9.2.2 Dimensioning with respect to corrosion and
               mechanical strength
        9.2.3 Dimensioning with respect to thermal strength
        9.2.4 Dimensioning with regard to touch and step
               voltages
   9.3 CONSTRUCTION OF EARTHING SYSTEMS
        9.3.1 Installation of earth electrodes and
               earthing conductors
        9.3.2 Measures to be taken to reduce the effects
               of high frequency interference
        9.3.3 Transferred potentials
        9.3.4 Measures for earthing on equipment and
               installations
   9.4 COMMON EARTHING SYSTEM FOR HIGH VOLTAGE AND LOW
        VOLTAGE SYSTEMS
        9.4.1 Conditions for a common earthing system
        9.4.2 Supply of low voltage installations inside
               the area of a high voltage earthing system
        9.4.3 Supply of low voltage installations outside
               the area of a high voltage earthing system
        9.4.4 Separated earthing systems
   9.5 EARTHING MEASURES AGAINST LIGHTNING EFFECTS
   9.6 MEASUREMENTS FOR AND ON EARTHING SYSTEMS
   9.7 SITE INSPECTION AND DOCUMENTATION OF EARTHING SYSTEMS
   9.8 GENERAL COMMENTS ON CHECKING AND SUPERVISION OF
        EARTHING SYSTEMS
        9.8.1 Checking by inspection
        9.8.2 Checking by measurement or calculation
10 INSPECTION AND TESTING ON SITE BEFORE TAKING OVER
ANNEX A (NORMATIVE) TYPE AND MINIMUM DIMENSIONS OF EARTH
        ELECTRODE MATERIALS ENSURING MECHANICAL STRENGTH
        AND CORROSION RESISTANCE
ANNEX B (NORMATIVE) CURRENT RATING CALCULATION OF EARTHING
        CONDUCTORS AND EARTH ELECTRODES
ANNEX C (NORMATIVE) TOUCH VOLTAGE AND BODY CURRENT
   C.1 EQUIVALENCE BETWEEN TOUCH VOLTAGE AND BODY CURRENT
   C.2 TAKING INTO ACCOUNT ADDITIONAL RESISTANCES
ANNEX D (NORMATIVE) DESCRIPTION OF THE RECOGNIZED SPECIFIED
        MEASURES M
ANNEX E (NORMATIVE) MEASURES ON EARTHING SYSTEMS TO REDUCE
        THE EFFECTS OF HIGH FREQUENCY INTERFERENCE
ANNEX F (NORMATIVE) DETAILED MEASURES FOR EARTHING OF
        EQUIPMENT AND INSTALLATIONS
   F.1 FENCES AROUND SUBSTATION INSTALLATIONS
   F.2 PIPES
   F.3 TRACTION RAILS
   F.4 POLE MOUNTED TRANSFORMING AND/OR SWITCHING
        INSTALLATIONS
   F.5 SECONDARY CIRCUITS OF INSTRUMENT TRANSFORMERS
ANNEX G (NORMATIVE) MEASURING TOUCH VOLTAGES
ANNEX H (INFORMATIVE) METHODS OF PROTECTION AGAINST DIRECT
        LIGHTNING STROKES
   H.1 SHIELD WIRES
   H.2 LIGHTNING RODS
ANNEX J (INFORMATIVE) REDUCTION FACTORS RELATED TO EARTH
        WIRES OF OVERHEAD LINES AND METAL SHEATHS OF
        UNDERGROUND CABLES
   J.1 GENERAL
   J.2 TYPICAL VALUES OF REDUCTION FACTORS OF OVERHEAD
        LINES AND CABLES (50 Hz)
ANNEX K (INFORMATIVE) BASIS FOR THE DESIGN OF EARTHING
        SYSTEMS
   K.1 SOIL RESISTIVITY
   K.2 RESISTANCE TO EARTH
ANNEX L (INFORMATIVE) INSTALLING THE EARTH ELECTRODES
        AND EARTHING CONDUCTORS
   L.1 INSTALLATION OF EARTH ELECTRODES
        L.1.1 Horizontal earth electrodes
        L.1.2 Vertical or inclined driven rods
        L.1.3 Jointing the earth electrodes
   L.2 INSTALLATION OF EARTHING CONDUCTORS
        L.2.1 Installing the earthing conductors
        L.2.2 Jointing the earthing conductors
ANNEX M (INFORMATIVE) APPROXIMATE FORMULAE FOR SIMPLE
        EARTHING SYSTEMS: APPROPRIATE DISTANCES TO AVOID
        DANGEROUS VOLTAGES
ANNEX N (INFORMATIVE) MEASUREMENTS FOR AND ON EARTHING
        SYSTEMS
   N.1 MEASUREMENT OF SOIL RESISTIVITIES
   N.2 MEASUREMENT OF RESISTANCES TO EARTH AND IMPEDANCES
        TO EARTH
   N.3 DETERMINATION OF THE EARTH POTENTIAL RISE
   N.4 ELIMINATION OF INTERFERENCE AND DISTURBANCE
        VOLTAGES FOR EARTHING MEASUREMENTS
ANNEX P (INFORMATIVE) DETAILS ON SITE INSPECTION AND
        DOCUMENTATION OF EARTHING SYSTEMS
ANNEX Q (INFORMATIVE) EXAMPLES FOR CHECKING THE CORRECT
        DESIGN CONCERNING THE PERMISSIBLE TOUCH VOLTAGE
ANNEX R (INFORMATIVE) THE USE OF REINFORCING BARS IN
        CONCRETE FOR EARTHING PURPOSE
ANNEX S (INFORMATIVE) A-DEVIATIONS
A-DEVIATIONS FOR BELGIUM
A-DEVIATIONS FOR SWITZERLAND
A-DEVIATIONS FOR SPAIN
A-DEVIATIONS FOR FINLAND
A-DEVIATIONS FOR FRANCE
A-DEVIATIONS FOR UNITED KINGDOM
A-DEVIATIONS FOR ITALY
A-DEVIATIONS FOR SWEDEN
ANNEX T (NORMATIVE) SPECIAL NATIONAL CONDITIONS AND
        NATIONAL PROVISIONS (PART OF NATIONAL STANDARDS,
        SPECIFICATIONS OR PRACTICES)
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
CZECH REPUBLIC
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
DENMARK
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
FINLAND
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
FRANCE
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
UNITED KINGDOM
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
ITALY
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
THE NETHERLANDS
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
NORWAY
SPECIAL NATIONAL CONDITIONS AND NATIONAL PROVISIONS FOR
SWEDEN
ANNEX U (INFORMATIVE) BIBLIOGRAPHY

Provides the requirements for the design and erection of electrical installations, in systems with nominal voltage above 1 kV a.c., so as to provide safety and proper functioning for the use intended.