Introduction on indian codes as applied in electrical design

Introduction on Indian codes & Introduction on Indian codes & regulation as applied in electrical regulation as applied in electrical designdesign

ByByAsif EqbalAsif Eqbal

By Asif Eqbal

ContentContentMajor codes & standard followed in India for electrical design

Objective of codes & standard

Indian Code for Industrial Lighting System

Indian Code for Earthing System

Indian Code for Lightning Protection System

By Asif Eqbal

Major codes & standard followed in Major codes & standard followed in IndiaIndia Indian Electricity rules, 1956 as amended up to 25TH Nov., 2000

Bureau of Indian standards

Central electricity authority guidelines

CPCB norms (central pollution control board)

National building code

CBIP manuals (Central board of irrigation & power)

Oil Industry safety directorate (OISD) for oil & gas industry

IE rules & IS takes precedence over all the standards. None of the Indian standard contradicts each other, they only supplement each other in a way that what is not mentioned in one standard is available in another.

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Indian Electricity RulesIndian Electricity Rules Indian electricity rues are based on Indian Electricity Act,1910 recommended

by Central Electricity Board of India. IE rules are mandatory as they have been prepared and implemented by

legislation of government of India. All the statutory clearances and approval for any project is provided by

central electrical inspector to that province where the location of project is and also the local provincial inspector. Central electrical inspector carries the inspection as per the guidelines of IS and IE rules.

IE rules defines the eligibility criteria for any person to operate or undertake maintenance of any type of industrial electrical installation.

Major guidelines provided are as follows: Clearance above ground of the lowest conductor.-

No conductor of an overhead line, including service lines, erected across a street shall at any part thereof be at a height of less than-

(a) for low and medium voltage lines 5.8 meters(b) for high voltage lines 6.1 meters

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Indian Electricity RulesIndian Electricity Rules

No conductor of an overhead line including service lines, erected elsewhere than along or across any street shall be at a height less than -

for low, medium and high voltages lines up to and including 11,000 volts, if bare 4.6 meters

for low, medium and high voltage lines up to and including 11,000 volts, if insulated 4.0 meters

for high voltage lines above 11,000 volts 5.2 meters For extra-high voltage lines the clearance above ground shall not be less

than 5.2 meters plus 0.3 meter for every 33,000 volts or part thereof by which the voltage of the line exceeds 33,000 volts;

Provided that the minimum clearance along or across any street shall not be less than 6.1 meters.

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Indian Electricity RulesIndian Electricity Rules Routes; Proximity to aerodromes, Transporting and Storing of material near

overhead lines are also defined in IE rules. Other features and area covered by IE rules are:

I. GENERAL SAFETY REQUIREMENTSII. Testing of consumer’s installationIII. Installation and Testing of Generating UnitsIV. Test for resistance of insulationV. ELECTRIC TRACTIONVI. ADDITIONAL PRECAUTIONS TO BE ADOPTED IN MINES AND OIL-FIELDSVII. Connection with earth & Earth leakage protective deviceVIII. Identification of earthed and earthed neutral conductors andIX. position of switches and cut-outs thereinX. Earthed terminal on consumer’s premisesXI. Accessibility of bare conductors 15XII. Danger notices

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Indian Electricity RulesIndian Electricity RulesAs per IE rules voltage are categorized as “ low” where the voltage does not exceed 250 volts under normal

conditions. “medium "where the voltage does not exceed 650 volts under normal

conditions. “ high "where the voltage does not exceed 33,000 volts under normal

conditions. “ extra high "where the voltage exceeds 33,000 volts under normal

conditions. However as per general practice 415 and lesser is considered as low,

above 415 and less than 33kV is considered as medium and 33kV and above is considered as high. Above 400kV is considered as EHV.

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Central Electricity authority (CEA)Central Electricity authority (CEA) Standard Technical Specification for Sub- critical Thermal Power Project -

2x(500MW or above). Because of unprecedented growth being witnessed by the power sector

with a capacity addition of over 78,000 MW envisaged during 11th Plan and about 80,000 MW in 12th Plan, every possible opportunity for enhancing pace of capacity addition is explored and fully exploited. In this context, there has been a long felt need to standardize the technical specification of thermal power stations with a view to reducing the time for pre-award activities, design & engineering and the manufacturing by equipment manufacturers. To do this, a Committee was set up by CEA under the chairmanship of Member Thermal) in May 2007 with participation from major utilities and manufacturers for developing standard technical specifications for main plant equipment for coal based thermal power plant having 500MW and higher capacity sub-critical units.

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Central Electricity authority (CEA)Central Electricity authority (CEA)

This guideline covers the design, engineering, manufacture, inspection and testing at manufacturer's works, supply, packing and delivery at project site, unloading, storage and in plant transportation at site, erection, supervision, pre-commissioning, testing, successful commissioning, performance testing and handing over of main plant package for sub-critical thermal power project having two (2) units of 500 MW (or above) consisting of steam generator, steam turbine– generator, electrical system, and C&I system along with all associated auxiliaries and accessories and associated civil works.

These guidelines are framed by Government of India, Ministry of Power, New Delhi.

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Central Pollution Control Board Norms Central Pollution Control Board Norms (CPB)(CPB) The Central Pollution Control Board (CPCB), statutory

organization, was constituted in September, 1974 under the Water (Prevention and Control of Pollution) Act, 1974. Further, CPCB was entrusted with the powers and functions under the Air (Prevention and Control of Pollution) Act, 1981.

CPCB norms are framed by ministry of environment. Every industrial installation requires to get the clearance from

CPCB before being commissioned. In electrical industry/installation the most widely and important

CPCB norm is installation and exhaust of emergency diesel generator.

Stack height for exhaust gases from diesel generator as per CPCB norm is given by the following formula:H = h + 0.2(kVA)0.5

H = Height of stackh = Height of building in meter where DG is installed.kVA = Total electrical power output of diesel generator.

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Central Pollution Control Board Norms Central Pollution Control Board Norms (CPB)(CPB) The stack height was originally evolved for those to be evolved in

metropolitan areas of Delhi. The idea was to avoid the problem of road side discharge from stack and

built up of pollutants in ambient air. For factories set up away from metropolis which use the emergency diesel

set occasionally are given some relaxation with respect to height of stack . Hence for non residential and commercial area the height of stack as per CPCB should be 2.5 times the height of building where DG set is installed or height of that building within factory premises where people are working.

CPCB norms also specifies the emission norms for diesel engine rating more than 800kW for power plant generator set application and other requirements.

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National Building codeNational Building code National building code is the prime code applicable for commercial

buildings. The National Building Code of India (NBC), a comprehensive building

Code, is a national instrument providing guidelines for regulating the building construction activities across the country. It serves as a Model Code for adoption by all agencies involved in building construction works be they Public Works Departments, other government construction departments, local bodies or private construction agencies. The Code was first published in 1970 at the instance of Planning Commission and then revised in 1983. Thereafter three major amendments were issued, two in 1987 and the third in 1997.

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National Building codeNational Building code

All the wiring installations for lighting and power receptacles are carried out as per the NBC guidelines and IS 732.

The Code mainly contains administrative regulations, development control rules and general building requirements; fire safety requirements; stipulations regarding materials, structural design and construction (including safety); and building and plumbing services general requirements of telecommunication, fire safety, earthing and lightning protection and earthing for high rise buildings (Apartments, shopping malls, hotels and official complexes) is also covered in this code.

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Central Board of Irrigation & Central Board of Irrigation & Power (CBIP)Power (CBIP)

Central Board of Irrigation & Power (CBIP), a Premier Institution, rendering dedicated services to professional organizations, engineers and individuals for more than 81 years, resulting in accelerated development in Water Resources, Energy and Allied Fields, including renewable energy, in the country and abroad. CBIP has grown into an eminent organization of international importance while serving the nation equally with great distinction. CBIP is Indian chapter for 10 international organizations related to aforesaid sector.

Today, Central Board of Irrigation and Power presents a shining example of a pioneer organization and has enabled Indian industry to set higher benchmarks and attain international standards in excellence by creating a unique platform for growth and progress of these sector.

Some important features of CBIP norms are that lot of figures are clearly mentioned in this code which are not mentioned in any other Indian codes. Some examples are:Loss figure for oil type power & distribution transformer

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Central Board of Irrigation & Central Board of Irrigation & Power (CBIP)Power (CBIP)

Loss figure for oil type power & distribution transformer

Standard ratings for bus ducts at various voltage level

Complete step by step procedure for S/S earthing Earthing and transformers are the two electrical package where the CBIP

manuals are widely used. IS 3043 is supplemented by this standard as IS does not mentions details about earth mat design for switchyard or S/S.

IS for power transformer is also supplemented by this standard as none of the IS mentions the loss figure, relation between ONAN and ONAF rating over fluxing capability etc…..for any transformer.

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Objectives of codes & standardObjectives of codes & standard The Electrical System shall be designed to provide:

Safety to personnel and equipment both during operation and maintenance. Reliability of Service. Minimum fire risk. Ease of maintenance and convenience of operation. Automatic protection of all electrical equipment through selective relaying system. Electrical supply to equipment and machinery within the design operating limits. Adequate provision for future extension and modification. Cost effective.

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Objectives of codes & standardObjectives of codes & standard The design shall be in accordance with established codes, Standards, Specifications, sound engineering practices and shall conform to the statutory regulations applicable in India and at Site Location. In case of conflict in the various documents and drawings and various Codes and Standards followed, the moststringent shall govern.

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Indian Code for Industrial Lighting Indian Code for Industrial Lighting SystemSystem

IS 3646 : CODE OF PRACTICE FOR INTERIOR ILLUMINATION

IS 6665 : CODE OF PRACTICE FOR INDUSTRIAL LIGHTING

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Design GuidelinesDesign Guidelines Plant Illumination System comprise of following:

Normal 230V, ac lighting system.

Normal-cum-emergency 230 V, ac lighting system having DG backup.

Critical DC Lighting having DC Battery backup.

20-25% of total Plant Lighting should be emergency lighting having DG Back-up.

Critical Areas of Plant such as sub-station, control room, exit points should have critical DC Lighting having DC battery backup.

During normal operation, normal & emergency lighting fed by normal power source.

On failure of normal supply, emergency lighting load shall transfer to emergency source.

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Design GuidelinesDesign Guidelines Illuminance ranges recommended for interior or activity :

• Middle value (R) for working interiors

• Higher value (H) for visual work

• Lower value (L) where accuracy is non-important

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Design GuidelinesDesign GuidelinesTYPE OF LOCATION LUX

CONTROL ROOM- GENERAL LIGHTING 400-700

- REAR OF INSTRUMENT PANEL 250

- OUTSIDE, NEAR ENTRANCES 150

PUMP AND COMPRESSOR HOUSE 100

SWITCHROOM AND PIB’S 150

OUTDOOR OPERATIONAL AREAS 50

OUTDOOR NON-OPERATIONAL AREAS 10

DRAWING OFFICES 700

OFFICES 400

WORKSHOPS - INTERIOR 250

- EXTERIOR 50

STAIRWAYS,PLATFORMS & WALKWAYS 50

ROADS/ MAIN ACCESS 5

ROADS MINOR 5

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Type of Lighting SystemType of Lighting System

Type of Lamp

Lum / Watt Color

Rendering Index

Typical ApplicationLife

(Hours)Range

Avg.

Incandescent 8-18 14 Excellent Homes, restaurants, general lighting, emergency lighting

1000

Fluorescent Lamps 46-60 50 Good w.r.t. coating

Offices, shops, hospitals, homes 5000

Compact fluorescent lamps (CFL) 40-70 60 Very good Hotels, shops, homes, offices 8000-10000

High pressure mercury (HPMV) 44-57 50 Fair General lighting in factories, garages, car parking, flood lighting

5000

High pressure sodium (HPSV) SON

67-121 90 Fair General lighting in factories, ware houses, street lighting

6000-12000

Low pressure sodium (LPSV) SOX

101-175

150 Poor Roadways, tunnels, canals, street lighting

6000-12000

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Lighting CalculationLighting Calculation

Dia-LUX is a 3D-software used for effective and professional light planning.

It is possible to import CAD model of Architectural Building and plan lighting arrangement on exact location as desired and perform Lighting Calculation to achieve desired Illumination Level on work-plane area.

Dia-LUX can be used for planning of Indoor Lighting, Exterior Lighting and street lighting.

It issue normative documentation to validate the design.

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Indian Code for Earthing/Grounding Indian Code for Earthing/Grounding SystemSystem

IS 3043 : CODE OF PRACTICE FOR EARTHING

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Design GuidelinesDesign Guidelines The earthing system shall be provided for;  Equipment earthing for personnel safety System neutral earthing Static earthing Protection against lightning

The earthing conductor shall be adequately sized to carry the maximum earth fault current.

Earth resistance shall be less than 1 ohm.

The number and depth to which the electrodes are driven depend upon soil condition s and soil electrical resistivity levels.

All medium voltage equipment shall be earthed by two separate and distinct connections with earth. In case of High and extra high voltage, the neutral point shall be earthed by not less than two separate and distinct connections with earth, each having its own electrode at the sub-station.

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Design GuidelinesDesign Guidelines

Main switchboards and MCCs shall be provided with an earth bar running the full length of the board, which shall be connected to sub-station main earthing grid.

Separate clean earth system for instrumentation, DCS, PLC etc shall be provided as required.

A separate earth conductor shall be laid along the cable trays and all other trays shall be interconnected at every 10m distance.

Lighting fixtures, receptacles, switches, conduits and junction boxes shall be properly earthed using 12 SWG GI wire run along the entire length of the conduit.

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Earthing CalculationEarthing CalculationStep-1 To Determine minimum size of Earth Conductor (As per IS:3043)

S = I√t k

Where,S = Conductor cross section area in mm² I = Fault current in amperes. t = Fault duration in seconds k = Constant depending on material of earthing conductor, its

insulation, the initial and final temperature.

Step-2 Calculate Resistance of Earth Electrode (As per IS:3043)

Re = (100 X ρ X Ln (4L/D)) 2ΠL

Where,Re = Resistance of earth electrode L = Length of pipe in cm ρ = soil resistivity in ohm-m D = Diameter of pipe in cm

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Earthing CalculationEarthing CalculationStep-3 Calculate Net Resistance of Earth Electrode (As per IS:3043)

Rearth = Re

N

Where,Rearth = Net resistance of Earth PitsRe = Resistance of Pipe Electrode N = No. of Earth Electrode considered

Step-4 Calculate Resistance of Earth Strip (As per IS:3043)

Rs = (100 X ρ X Ln (2L2/(wXt))) 2ΠL

Where,RS = Resistance of earth strip L = Length of conductor in cm. w = Depth of burial of electrode in cm t = width of the electrode in cm or twice the diameter of

conductor in cm.

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Earthing CalculationEarthing CalculationStep-5 Calculate Total Grid Resistance (As per IS:3043)

RTotal = Rearth X Rs Rearth + Rs

Where,Rearth = Net resistance of Earth PitsRs = Resistance of Earth StripRTotal = Total Grid Resistance

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Indian Code for Lightning Protection Indian Code for Lightning Protection SystemSystem IS 2309 : PROTECTION OF BUILDINGS AND ALLIED STRUCTURES

AGAINST LIGHTNING

IEEE: 142 : IEEE RECOMMENDED PRACTICE FOR GROUNDING OF INDUSTRIAL AND COMMERCIAL POWER SYSTEM

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Design GuidelinesDesign Guidelines

Lightning is a natural hazard, being the discharge of static electricity generated in storm clouds, which may cause damage to structures.

The need for providing the lightning protection system shall be established by calculating risk index value for each building structure etc as per procedure give in IS: 2309 and any building whose overall risk factor is more than 10-5 shall be provided with lightning protection.

Lightning protection system shall consist of vertical air termination roads, horizontal roof conductors, down conductors and earth electrodes.

Air termination and down conductors for buildings shall be of GS flat. Electrodes shall be GS rod.

Each down conductor shall be connected to a rod electrode, which in turn shall be connected to the station earthing system through test links.

Conductors of lightning protection system shall not be connected with conductors of safety earthing system above ground level.

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Design GuidelinesDesign Guidelines

Galvanized Steel (GS) is used as the material for lightning protection conductor. The sizes of the conductors for lightning protection system are decided based on mechanical strength. The minimum size for air terminations and down conductor, as per IS-2309, table-4 is 20X3 mm GS. However, higher size is selected considering mechanical strength.

Air termination network may consist of vertical or horizontal conductors or combination of both which is provided for the buildings requiring lightning protection according to IS : 2309.

Down conductors shall be as short and straight as practicable and shall follow a direct path to earth electrode.

As per IS 2309, article no. 12.2.5, Steel column can be acted as Down Conductor and as per IS 2309, article no. 9.0.1, Metal roof can be acted as Air termination.

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