How to Design efficient Street lighting-(Part-4)


(C) Lighting Factor:

(1) Maintenance Factor (Light Loss Factors) (MF)

  • The Maintenance Factor (Light loss factor) is the combination of factors used to denote the reduction of the illumination for a given area after a period of time compared to the initial illumination on the same area.
  • The efficiency of the luminaire is reduced over time. The designer must estimate this reduction to properly estimate the light available at the end of the lamp maintenance life.
  • Luminaire maintenance factors vary according to the intervals between cleaning, the amount of atmospheric pollution and the IP rating of the luminaire.
  • However, it is proposed to consider maintenance factor of not less than 0.5 for LED Road lighting installations for IP66 rated luminaires.
  • The maintenance factor may range from 0.50 to 0.90, with the typical range between 0.65 To 0.75
  • These maintenance factor values shall be adopted for the purposes of producing the lighting simulation design.
  • The maintenance factor is the product of the following factors.
  • LLF = LLD x LDD x EF
  • Mostly We consider Maintenance factor from 0.8 to 0.9
  • We have to choose Maintenance factor carefully by increasing maintenance factor 0.5 the spacing of pole increasing 2 meter to 2.5 meter.
Maintenance Factor Max. Spacing of Pole (Meter)
0.95 43
0.9 40.5
0.85 38
0.8 36

(A) Lamp Lumen Depreciation Factor (LLD)

  • As the lamp progresses through its service life, the lumen output of the lamp decreases. This is an inherent characteristic of all lamps. The initial lamp lumen value is adjusted by a lumen depreciation factor to compensate for the anticipated lumen reduction.
  • This assures that a minimum level of illumination will be available at the end of the assumed lamp life, even though lamp lumen depreciation has occurred. This information should be provided by the manufacturer. For design purposes, a LLD factor of 0.9 to 0.78 should be used.

(B) Luminaire Dirt Depreciation Factor (LDD).

  • Dirt on the exterior and interior of the luminaries and to some on the lamp reduces the amount of light reaching the roadway.
  • Various degrees of dirt accumulation may be anticipated depending upon the area in which the luminaire is located. Industry, exhaust of vehicles, especially large diesel trucks, dust, etc, all combine to produce the dirt accumulation on the luminaries.
  • Higher mounting heights, however, reduce the vehicle-related dirt accumulations.
  • LDD factor of 0.87 to 0.95 should be used. This is based on a moderately dirty environment and three years exposure time.

(C) Equipment Factor (EF).

  • Allows for variations inherent in the manufacture and operation of the equipment (i.e., luminaries, system voltage and voltage drop).
  • It is generally assumed to be 95%.

(2) Coefficient of Utilization (CU):

  • Coefficient of Utilization is the ratio of the luminous flux from a luminaire received on the surface of the roadway to the lumens emitted by the luminaire’s lamps alone.
  • Coefficient of Utilization should be maximum.
  • Coefficient of Utilization differs with each luminaire type, and depends upon mounting height, road width, and overhang.
  • The coefficient of utilization (K) should be over 30% or the utilance above 40% for the road, highway, square or enclosure. Luminaires or floodlights should not by placed far from the area to be lit or, where appropriate, light projection beyond the useful zone should be minimized (K = average maintained illuminance multiplied by the surface calculation and divided by the lumens installed).

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Type Luminaries Dirt Depreciation Luminaire Lumen Depreciation Total Light Loss Factor
LED 0.9 0.85 0.765
HPS 0.9 0.9 0.81
LPS 0.9 0.85 (0.7 for 180W) 0.765 (0.63 for 180W)

 

Light Loss Factors

Type of Lamp Laminar Dirt description Light Loss Factor
HPS 0.88 0.74
Induction 0.88 0.62
LED 0.88 0.72

 

Maintenance factors

Cleaning intervals (months) Pollution category
High Medium Low
12 0.53 0.62 0.82
18 0.48 0.58 0.8
24 0.45 0.56 0.79
36 0.42 0.53 0.78

 

Maintenance Factors for 36 month cleaning interval

Factors IP5X IP6X
Pollution category Pollution category
Low Medium High Low Medium High
LMF 0.88 0.82 0.76 0.9 0.87 0.83
LLMF 0.89 0.89 0.89 0.89 0.89 0.89
MF 0.78 0.73 0.68 0.80 0.77 0.74

 (E) Lighting Uniformities

(1) Lighting Uniformities

  • Uniformity is a description of the smoothness of the lighting pattern or the degree of the intensity of bright and dark areas on the road.
  • Uniformity is a measure of how evenly distributed the light on the road is, which can be expressed as Overall Uniformity (UO) and Longitudinal Uniformity (UL).
  • The uniformity ratio shall not exceed 4:1 and preferably should not exceed 3:1 except on residential streets, where 6:1 may be acceptable.

(A) Overall uniformity:

  • In design, the overall uniformity (UO) is expressed as a ratio of the minimum to the average luminance on the road surface of the carriageway within the calculation area.
  • UO=Lmin / Lave

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  • It is a measure of how evenly or uniformly illuminate on the road surface.
  • A good overall uniformity ensures that all spots and objects on the road are sufficiently lit and visible to the motorist.
  • The industry accepted value for UO is 30 to 0.40.

(B) Longitudinal uniformity:

  • The longitudinal uniformity (UL) is expressed as the ratio of the minimum to maximum luminance along the center line of a lane within the calculation area.
  • UL=Lmin / Lmax.
  • Longitudinal uniformity is a measure to reduce bright and dark bands of light appearing on road lit surfaces. The effect can be somewhat hypnotic and present confusing luminance patterns.

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  • It is a measure to reduce the intensity of bright and dark banding on road lit surface.
  • A good level of longitudinal uniformity ensures comfortable driving conditions by reducing the Pattern of high and low luminance levels on a road (i.e. zebra effect).
  • It is applicable to long continuous roads.

 Combination of Overall Uniformity and Longitudinal Uniformity:

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  • The picture on the left shows a road with good UO while the picture on the right has low level of UO. The Road is more visible in the road with higher UO. Having higher UO allows the motorist to see the road clearly and anticipate potential road hazards (e.g. open manholes, road excavations, sharp objects on the road, people crossing the street).
  • The picture on the right shows a road with low level of UL demonstrating the ‘Zebra Effect’ while the picture on the left has high level of UL without ‘Zebra Effect’.
  • The ‘zebra effect’ can cause discomfort to motorists, posing a risk to road safety. Ensuring good level of uniformity can reduce the luminance level needed. 
Lighting levels
Category Eave ( LUX) Emin  LUX) Uniformity ratios
Emax : Emin Eave : Emin
Express & Main street 30 15 3:01 2.5:1
Suburban shopping street 25 10 5:01 3:01
Subsidiary street 15 10 5:01 3:01
Other streets 15 5 10:01 5:01

 

Road Classification Area Classification Average  Lux Uniformity Ratio (Aver./Min.)
Arterial (Minor & Major) Commercial 12 3 to 1
Intermediate 9
Residential 6
Collector (Minor & Major) Commercial 8
Intermediate 6 4 to 1
Residential 4
Local Commercial 6
Intermediate 5 6 to 1
Residential 3
Alleys Commercial 4
Intermediate 3 6 to 1
Residential 2
Sidewalks (Roadside) Commercial 3 3 to 1
Intermediate 6 4 to 1
Residential 2 6 to 1
Pedestrian Ways 15 3 to 1

  

Illumination for Intersections

Functional Classification Average Maintained Illumination at Pavement by Pedestrian Area Classification in Lumen Uniformity
High Medium Low Eavg/Emin
Major/Major 37 28 19 32
Major/Collector 31 24 16 32
Major/Local 28 22 14 32
Collector/Collector 26 19 16 43
Collector/Local 23 17 11 43
Local/Local 19 15 9 65

 

Illumination for Pedestrian Areas

Maintained Illuminance Values for Walkways
Area Classification Description E avg (Lux) EV min (Lux) E avg/Emin
High Pedestrian Conflict Mixed Vehicle and Pedestrian 22 11 43
Areas Pedestrian Only 11 5 43
Medium Pedestrian Pedestrian Areas 5 2 43
Conflict Areas
Low Pedestrian Rural/Semi-Rural Areas 2 1 108
Conflict Areas Low Density Residential (2 or fewer dwelling units per acre) 3 1 65
Medium Density Residential (2.1 to 6.0 dwelling units per acre) 4 1 43
Pedestrian Portion of Pedestrian/Vehicular Underpasses Day 108 54 43

How to Design efficient Street lighting-(Part-3)


(C) Lighting Fixture:

(1) Fixture’s Mounting Height:

  • Higher mounting heights used in conjunction with higher wattage luminaries enhances lighting uniformity and typically reduces the number of light poles needed to produce the same illumination level.
  • In general, higher mounting heights tend to produce a more cost-effective design. For practical and aesthetic reasons, the mounting height should remain constant throughout the system.
  • The manufacturer’s photometric data is required to determine an appropriate mounting height.
  • Typical mounting heights for highway lighting purposes range from 30 ft to 55 ft (9.1 meter to 16.8 meter).
  • Mounting heights for light towers or High mast is typically 80 ft (24 m) or greater.
  • The installation height is too low, the glare of the lamp increases.
  • As the installation high increase, glare decreases, but the lighting utilization rate decreases.

 

(2) Fixtures Classification:

  • The Illuminating Engineering Society of North America (IESNA, IES or BIS1981) provides classifications for luminaires according to their glare control and high-angle brightness.

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(A) Full Cutoff (F):

  • A luminaire light distribution is designated as full cutoff (F) when Zero intensity at or above horizontal (90° above nadir) and Less than 10% of lamp lumens at or above 80°.
  • Full-cutoff fixtures reduce glare dramatically and eliminate direct up light by sending all their light toward the ground .This efficiency should translate into lower bulb wattages if the existing poles are used. However, some lighting engineers believe that to achieve the same illumination uniformity as their semi-cutoff counterparts, full-cutoff fixtures need to be mounted either on taller poles or closer together
  • Benefits:
  • Limits spill light on to adjacent property, reduces glare. No light is emitted directly from the luminaries into the sky.
  • Reduce Lighting Pollution.
  • Limitations:
  • May reduce pole spacing to maintain uniformity and increase pole and luminaire quantities.
  • Application:
  • Use for roadway, parking, and other vehicular lighting applications. Minimizes glare and light pollution and light trespass.

 (B) Cutoff (C):

  • A luminaries light distribution is designated as cutoff (C) when Less than 2.5% Intensity at or above horizontal (90° above nadir) and Less than 10% of lamp lumens at or above 80°.
  • The direction of maximum intensity may vary but should be below 65º.
  • Benefits:
  • Small increase in high-angle light allows increased pole spacing.
  • Cutoff system is the reduction of glare.
  • Limitations:
  • May allow some up light (Sky Light) from luminaries. Typically a small overall impact on sky glow.
  • Application:
  • Interchange lighting and rural intersections due to the ability to reduce glare.
  • Use in applications where pedestrians are present. Provides more vertical illuminance than Full Cutoff luminaires.
  • Lamp rating should be less than 3200 lumens.
  • The cutoff design is where the luminaire light distribution is less than 25,000 lm at an angle of 90° above nadir (vertical axis) and 100,000 lm at a vertical angle of 80° above nadir.

 (C) Semi Cutoff (S) (Medium Beam Angle):

  • A luminaire light distribution is designated as Semi cutoff (S) when Less than 5% Intensity at or above horizontal (90° above nadir) and Less than 20% of lamp lumens at or above 80°.
  • The direction of maximum intensity may vary but should be below 75º.
  • Benefits:
  • High-angle light accents taller vertical surfaces such as buildings. Most light is still directed downward.
  • Limitations:
  • Little control of light at property line.
  • Potential for increased glare when using high wattage luminaries. Typically directs more light into the sky than cutoff.
  • Application:
  • Used for standard road lighting. Adequate glare control is obtained with reasonable spacing.
  • The principal advantage of the semi-cutoff system is a greater flexibility in sitting.
  • Use in pedestrian areas. If using in residential areas, provide with house side shields to minimize light trespass. Lamp rating should be less than 3200 lumens.
  • For the semi-cutoff design, the luminous flux numbers become 50,000 lm for 90° above nadir and 200,000 lm at a vertical angle of 80° above nadir.
  • Semi-cutoff fixtures create broad cones of light that permit wide spacing between poles. But such fixtures create harsh glare and send some light directly into the sky.

(D) Non Cutoff (N) (Higher Beam Angle):

  • A luminaries light distribution is designated as Non Cutoff (N) when Emit light into all directions.
  • No limitations on light distribution at any angle.
  • There is considerable output near the horizontal plane.
  • Benefits:
  • Uniform luminous surfaces such as internally illuminated signs or globes. Wattage should be limited. Suitable for sports lighting, facade, landscape or other applications where luminaires are tilted due to limitations in pole or fixture locations
  • Limitations:
  • Location and aiming are critical. Most likely of all categories to produce offensive brightness and sky glow.
  • Application:
  • Used in areas with a lot of background light. Non-cutoff luminaries shall not be used at lower mounting heights because of glare.
  • Use for decorative applications only. Lamp rating should be less than 3200 lumens.
  • “Full cut off” fixtures must be installed properly, so that the bottom of the fixture is level with the ground.
  • “Fully Shielded” fixtures do not allow any light to be emitted above the lowest light emitting
  • part, but do not restrict light output in the “glare” zone, 90-80 degrees below horizontal.

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  (3) Fixtures Distributions (Optical System):

  • The Illuminating Engineering Society classified series of Fixture distribution patterns as Types I, II, III, IV, and V.

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(A) Type I (Two-way):

  • The lateral distribution having a preferred lateral width of 15 degrees in the cone of maximum Lumen.
  • Illumination Pattern: Narrow, symmetric luminance pattern.
  • Fixture Location: This type is generally applicable to a luminaire location near the center of a roadway where the mounting height is approximately equal to the roadway width.
  • Type of Road: The luminaire is placed on the side of the street or edge of the area to be lighted. Most 1or 2 Lane Road

(B) Type II (Two Way) :

  • Light distributions have a preferred lateral width of 25 degrees.
  • Illumination Pattern: Slightly wider illuminance pattern than Type I.
  • Fixture Location: They are generally applicable to luminaires located at or near the side of relatively narrow roadways, where the width of the roadway does not exceed 1.75 times the designed mounting height.
  • Type of Road: The luminaire is placed on the side of the street or edge of the area to be lighted. It produces a long, narrow, oval-shaped lighted area which is usually applicable to narrower streets.

(C) Type III (Bat Wing) :

  • Type III light distributions have a preferred lateral width of 40 degrees.
  • Illumination Pattern: It produces an oval-shaped lighted
  • Fixture Location: This distribution is intended for luminaires mounted at or near the side of medium width roadways, where the width of the roadway does not exceed 2.75 times the mounting height.
  • Type of Road: The luminaire is placed on the side of the street or edge of area to medium width streets.

(D) Type IV (Forward throw “Asymmetric”):

  • Type IV light distributions have a preferred lateral width of 60 degrees.
  • Illumination Pattern: Widest luminance pattern.
  • Fixture Location: This distribution is intended for side-of-road mounting and is generally used on wide roadways where the roadway width does not exceed 3.7 times the mounting height.
  • Type of Road: very wide roadway (4 to 6 Lane)
  • Applications: Type IV often use at perimeters where Spill Light is required and there is no place to add Pole.

(E) Type V:

  • Type V light distributions have a circular symmetry of candlepower that is essentially the same at all lateral angles.
  • Illumination Pattern: It produces a circular, wider lighted area and is usually applicable to wide streets.
  • Fixture Location: The luminaries are mounting at or near center of roadways, center islands of parkway, and intersections.
  • Type of Road: very wide roadway (4 to 6 Lane)
  • Applications: Type V often applies to high-mast lighting.

GUIDE FOR LUMINAIRE LATERAL LIGHT TYPE AND PLACEMENT

Pole Arrangement Road Width Type of Distribution
One Side or Staggered up to 1.5 x Mounting Height Types II-III-IV
Staggered or Opposite Beyond 1.5 x Mounting Height Types III & IV
Center of the Roadway Mounting up to 2 x Mounting Height Type I

 

Type of Classification

AREA CLASSIFICATION  CUTOFF TYPE
Commercial Full Cutoff or Semi Cutoff
Intermediate Full Cutoff or Semi Cutoff
Residential Full Cutoff

 

THE SELECTION OF LUMINAIRE MOUNTING HEIGHTS

Lamp Lumens Mounting Height
≤20,000 Lumen  ≤35 Foot
20,000 To 45,000 Lumen 35 To 45 Foot
45,000 To 90,000 Lumen 45 To 60 Foot

 

Type of LED Luminaries Type of Road Lamp mounting height from the floor level (Meters) Minimum Illumination Level (Lux) at centre of road Color of Illumination
250-260W Above 18 (20 To 22) 5000K-6500K
190W A1 Between 11 To 15 (20 To 22) 5000K-6500K
140-170W A1 Between 9 To 15 (18 To 20) 5000K-6500K
90-120W A2/B1 07 To 11 (15 To 18) 4300K-5600K
70-120W A2/B1 07- To 11 (15 To 18) 4300K-5600K
70-120W B1/B2 06 To 09 (15 To 18) 4300K-5600K
70-50W B1/B2/C1 7 To 9 (12 To 15) 4300K-5600K
45-50W B1/B2/C1 5 To 7 (12 To 15) 4300K-5600K
25-30W B1/B2/C1 5 To 7 (10 To 12) 4300K-5600K

 

Relationship between mounting height and spacing

Mounting Height Width of road 6 Meter to 7 Meter 9 Meter to 10.5 Meter 12 Meter to 14 Meter
Pole  arrangement Cut-off Type Semi Cutoff Type Cut-off Type Semi Cutoff Type Cut-off Type Semi Cutoff Type
8 Meter Single side 24 28
Staggered 24 28
Opposite 28 28
10 Meter Single side 30 30
Staggered 35 35 30 35
Opposite 35 40 30 35
12 Meter Single side 42 48 36 42
Staggered 36 42 36 42
Opposite 42 48 42 48

 

GUIDE FOR LUMINAIRE LATERAL LIGHT TYPE AND PLACEMENT

SIDE OF THE ROADWAY MOUNTING            CENTER OF THE ROADWAY MOUNTING
One Side
or Staggered
Staggered
or Opposite
Local
Street Intersection
Single Roadway Twin Roadways
(Median Mounting)
Local
Street Intersections
Road Width up to 1.5 x Mounting Height Road Width beyond1.5 x Mounting Height Road Width up to 1.5x Mounting Height Road Width up to 2x Mounting Height Road Width up to 1.5x Mounting Height (each pavement) Width up to 2.0x Mounting Height
Types Types Type Type Types Types
II, III, IV III & IV II (4-way) I II & III I (4-way) & V

 

How to Design efficient Street lighting-(Part-2)


(2) Proper Placement of Pole:

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(A) Setback

  • Set back is the horizontal distance between the face of a light pole and the edge of traveled way.
  • Placing luminaries too close to a vertical surface results in hotspots at its base.
  • A setback of 3 foot to 4 foot works well for many applications.
  • Light from luminaires at extremely short setbacks grazes the surface and enhances its texture.
  • Light from luminaries at Long setbacks (Luminaries too far from a vertical surface) cause shadows at low levels.
  • Longer setbacks may be required for taller surfaces.
  • Scallops between fixtures become more noticeable as setback increases.
  • As setback (or spacing) distance increases, Light levels and uniformity decrease.

Set Back (BS 5489)

Design Speed Pole Set Back
50 Km/Hr 0.8 Meter
80 Km/Hr 1 Meter
100 Km/Hr 1.5 Meter
120 Km/Hr 1.5 Meter

(B) Overhang

  • Overhang is the horizontal distance between the center of a luminaries mounted on a bracket (Nadir) and the adjacent edge of a carriage way or traveled way.
  • In general, overhang should not exceed one fourth of the mounting height to avoid reduced visibility of curbs, obstacles, and footpaths.

(C) Outreach

  • Outreach is the horizontal distance between the center of the column and the center of the luminaries and is usually determined for architectural aesthetic considerations.

(D) Pole Boom(Arm) Length:

  • The use of an arm places the light source closer to the traveled way while allowing the pole to be located further from the edge of the traveled way.
  • Depending on the application, Pole arms may be single and/or double mast arms or davit arms at the top of the pole.
  • There are several different arm lengths and styles of arms that are used.
  • Arm Type:
  • Type A bracket an arm has a single member arm. It is used when the Arm length is less than 3.5 Meter.
  • Type B bracket arm has a two member truss arm design. Type B arms are used when the Arm length is more than 3.5 Meter.
  • Arm Lengths:
  • The length of the bracket arm is dependent upon a street width, pole location in relation to the curb and the presence of a median.
  • Type A (Single member bracket) arms are available in 2 Meter and 2.5 Meter lengths.
  • Type B (Twin member bracket) arms are available in 3.5 Meter, 4 Meter and 5 Meter Lengths.
  • Pole Height is 10 Meter: On typical streets that are 12 Meter’ wide from curb to curb, either a 2 Meter or 2.5 Meter arm is used. Depending on whether the pole is located behind the sidewalk or in the grass parkway between the sidewalk and the curb, the arm length may need to be increased to 4 Meter.
  • Pole Height is 13 Meter: On an undivided street, generally Meter, 2.5 Meter or 4 Meter arms are used.
  • Pole Height is 13 Meter: divided Street, typically have a 8 Meter wide center median to divide opposing lanes of traffic. On streets where the light poles are installed in a raised median, two 4 Meter arms oriented 180° apart are used.

(E) Boom Tilt Angle (Boom Angle)

  • When the angle of tilt is larger, a uniformity ratio is increasing. Otherwise discomfort glare is increasing because strong light comes into driver’s eyes. So the angle of tilt shall be kept from 15° to 30°.
Tilt Angle
Pole Height Arm Length Arm Tile Angle
6 Meter 0.5 Meter 5°,10°,15°
8 Meter 1 Meter 5°,10°,15°
10 Meter 1.5 Meter 5°,10°,15°
>=12 Meter 2 Meter 5°,10°,15°

(F) Pole Height:

  • Light poles for conventional highway lighting applications support luminaire mounting heights ranging from approximately 30 ft to 50 ft (9.1 m to 15.2 m).
  • Light towers for high-mast lighting applications generally range from 80 ft to 160 ft (24.4 m to 48.8 m) and are designed in multiple sections.
  • Weathering steel is a common material choice for light towers.
  • Ornamental light Poles used for local streets generally range in height for 8 ft to 15 ft (2.4 m to 4.5 m).
Pole Height Application
< 6 Meter Majority of side streets or alleys, Public gardens and parking Area to make people feel safe
8 Meter Urban traffic route , the multiplicity of road junctions
10 Meter Urban traffic routes
12 Meter Heavily used routes
18 Meter High mast lighting poles shall be installed at large-scale area such as airports, dockyards, large industrial areas, sports areas and road Intersections.

 (G) Poles distance from Curb (Offset):

  • The lighting poles should not be installed very close to the pavement edge, because the capacity of the roadway is decreased and the free movement of traffic is obstructed.
  • For roads with raised curbs (as in urban roads) =Min. 0.3 meter and desirable 0.6 meter from the edge of raised curb.
  • For roads without raised curbs (as in rural roads)=Min. 1.5 meter from the edge of the carriageway, subject to min. 5.0 meter from the center line of the carriageway.
  • Height and overhang of mounting
  • The glare on eyes from the mounted lights decreases with increases in the height of mounting. Usually, mounting height range from 6 to 10m.
  • Overhangs on the lighting poles would keep the poles away from the pavement edges, but still allow the lamp to be held above the curb or towards the pavements.

 (H) Pole to Pole Spacing

  • Spacing is the distance, measured along the center line of the road, between successive luminaries in an installation.
  • To preserve longitudinal uniformity, the space height ratio should generally be greater than 3.
  • Placing luminaries too far apart creates scallops at the base of the surface.
  • Spacing distances that are equal to 3 to 4 times the setback work well for many applications.
  • Placing luminaries closer together eliminates scallops.
  • Uniformity and light levels increase as spacing (or setback) distances decrease.
  • Spacing of luminaires normally does not exceed five to six mounting heights.
  • The span must not be more than 45 meters and for an average of 20-30 meters.

Lighting Pole details as per Road

Road Road Width (Meter) Pole Arrangement Lamp (Watts) Pole to Pole Spacing (Meters) Mounting Height, (Meters) Arm Length, (Meters)
Expressway 10 Twin Central 250 25 To 35 12 1.5
15 250 20 To 35 12 3.0
20 Opposite 250 20 To 45 12 1.5
25 250 20 To 40 12 1.5
30 250 20 To 30 12 1.5
36 250 20 To 25 12 1.5
40 250 20 To 22 12 1.5
Major 10 One-side 250 10 To 40 10 1.5
15 250 10 To 45 12 3.0
10 Twin Central 150 20 To 37 10 1.5
15 250 20 To 43 12 3.0
20 Opposite 150 20 To 40 10 3.0
25 250 20 To 45 10 1.5
30 250 20 To 45 10 1.5
36 250 20 To 45 12 3.0
40 250 20 To 45 2 3.0
Collector 10 One-side 150 10 To 40 10 1.5
15 250 10 To 50 12 3.0
10 Twin Central 150 20 To 40 10 1.5
15 150 20 To 37 12 3.0
20 Opposite 150 20 To 47 10 1.5
25 250 20 To 48 10 1.5
Rural
Highway
8 One-side 150 10 To 38 8 1.5
10 150 10 To 37 8 3.0
15 150 15 To 38 10 3.0
10 Twin Central 150 20 To 45 10 3.0
15 150 20 To 39 12 3.0
20 1.5
Minor 4 One-side 70 10 To 40 8 1.5
6 70 10 To 40 8 1.5
8 70 10 To 40 8 1.5
10 70 10 To 39 8 1.5
10 Twin Central 70 20 To 35 8 1.5
15 Staggered 70 10 To 20 8 1.5
15 Opposite 70 20 To 40 8 1.5

 

Illumination Level
Classification  Average Illumination (lux) Ratio Minimum to average illumination
Class A1 30 0.4
Class A2 15 0.4
Class B1 8 0.3
Class B2 4 0.3

 

Relationship between Mounting Height and Spacing of Fixtures

Pole Arrangement Cut-off type Semi cutoff type
Height Spacing Height Spacing
Single side >=0.7 X Width of Road <=3 X Fixture Mounting Height >=0.8 X Width of Road <=3.5 X Fixture Mounting Height
Both Side Staggered >=1.5 X Width of Road <=3.5 X Fixture Mounting Height >=1.7 X Width of Road <=4 X Fixture Mounting Height
Both Side Opposite >=0.5 X Width of Road <=3 X Fixture Mounting Height >=0.6 X Width of Road <=3.5 X Fixture Mounting Height
Twin central >=0.7 X Width of Road <=3.5 X Fixture Mounting Height >=0.8 X Width of Road <=4 X Fixture Mounting Height

 

 Pole to Pole Distance vs Lux Level

Pole Height Lamp Pole to Pole Distance Max. Illumination (Lux) Average (Lux)
4 Meter 15 watt 12 to 18 Meter 25 18
5 Meter 18 watt 14 to 20 Meter 30 18
6 Meter 30 watt 18 to 24 Meter 32 20
7 Meter 50 watt 21 to 28 Meter 32 20
8 Meter 100 watt 24 to 32 Meter 40 22
9 Meter 110 watt 27 to 35 Meter 34 20
10 Meter 140 watt 30 to 40 Meter 35 22
12 Meter 180 watt 30 to 40 Meter 33 23
14 Meter 200 watt 30 to 40 Meter 30 21

 

Lux Vs Mounting Height

Fixtures (Lux) Mounting Height
3000 to 10000 Lux 6 to 7 Meter
10000 to 20000 Lux 7 to  9 Meter
More than 20000 Lux More than 9 Meter

 

 
Road Road Type Type of Pole positions Individual Carriageway Width (Meter) Central Verge (Meter) Pole Height above Ground (Meter) Maximum Pole to Pole Spacing (Meter) Clearance from Road Edge (Meter) Bracket Length (Meter) Tilt Angle Lighting Specifications Lamp (Watt)
A1 Dual Carriage Central Verge 10 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 11 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 12 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 14 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 16 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 12 0 12 35 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 250W
A1 Single Carriage Opposite 14.5 0 12 35 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 250W
A1 Single Carriage Opposite 16 0 12 40 0.6 Around one meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 18 0 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 21 0 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
Single Carriage Opposite 25 0 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 31 0 12 40 0.6 1 meter  10° 35 lux/ 0.4/
0.33
HP SV 400W
A2 Single Carriage Single Sided 10 11 30 0.6 < 1.0 meter  10° 25 lux
/0.4/ 0.33
HP SV 250W
A2 Single Carriage Single Sided 9 11 30 0.6 < 0.5 meter  10° 25 lux
/0.4/ 0.33
HP SV 250W
A2 Single Carriage Single Sided 7 11 30 0.6 < 0.5 meter  10° 25 lux
/0.4/ 0.33
HP SV 250W
A2 Single Carriage Single Sided 7 11 30 0.6 < 0.5 meter  10° 25lux
/0.4/ 0.33
HP SV 250W
A3 Single Carriage Single Sided 7 8 20 0.6 < 0.5 meter  10° 20lux
/0.4
HP SV 150W
Pedestrian Pathway Single Carriage Single Sided 3m-6m 7.5 20-25 0.6 <0.5 meter  10° 20 lux
/0.4
HP SV 150W

 

Poles (Meter) Top Dia (mm) Bottom Dia (mm) Thickness (mm) Base plate (mm) Single Arm Bracket (mm) Double Arm Bracket (mm)
3 70 130 3 200x200x12 1000 NA
3 70 130 3 200x200x12 NA 1000
4 70 130 3 200x200x12 1000 NA
4 70 130 3 200x200x12 NA 1000
4 70 130 3 200x200x12 1000 NA
5 70 130 3 200x200x12 NA 1000
5 70 130 3 200x200x12 1000 NA
6 70 130 3 200x200x12 NA 1000
6 70 130 3 200x200x12 1000 NA
7 70 135 3 225x225x16 1000 NA
7 70 135 3 225x225x16 NA 1000
8 70 135 3 225x225x16 1000 NA
8 70 135 3 225x225x16 NA 1000
9 70 155 3 260x260x16 1000 NA
9 70 155 3 260x260x16 NA 1000
9 70 175 3 275x275x16 1000 NA
9 70 175 3 275x275x16 NA 1000
10 70 175 3 275x275x16 1000 NA
10 70 175 3 275x275x16 NA 1000
10 70 200 3 290x290x16 1000 NA
10 70 200 3 290x290x16 NA 1000
11 70 210 3 320x320x20 1000 NA
11 70 210 3 320x320x20 NA 1000
12 70 230 3 325x325x20 1000 NA
12 70 230 3 325x325x20 NA 1000

 

Recommended Levels of Illumination (BIS 1981) (IS 1944)

Type of Road Road Characteristics Road Width (Meter) Average Level of Illumination on Road Surface in Lux Ratio of Minimum/Average Illumination Ratio of Minimum/Max Illumination Type of Luminaire Preferred Luminas Mounting Height
A-1 Important traffic routes carrying fast traffic >10.5,12,14,16,18,20,30 30 0.4 33 Cutoff 9 To 10 Meter
A-2 Main roads carrying mixed traffic like city main roads/streets, arterial roads, throughways > 7 m up to 10 m 15 0.4 33 Cutoff 9 To 10 Meter
B-1 Secondary roads with considerable traffic like local traffic routes, shopping streets < 7m Colony Roads 8 0.3 20 Cutoff or semi-cutoff 7.5 To 9 Meter
B-2 Secondary roads with light traffic 4m,5m, 6m 4 0.3 20 Cutoff or semi-cutoff 7.5 To 9 Meter

 

How to Design efficient Street lighting-(Part-1)


Introduction:

  • The basic idea of roadway and Highway lighting is to provide uniform level of illumination on road at horizontal and vertical level and provide a safe and comfortable environment for the night time driver.
  • Lighting design is basic idea of the selection and the location of lighting equipment to provide improved visibility and increased safety.
  • Street lighting systems should be designed in a way to avoid significant differences in luminance levels at the light source and on road areas. Furthermore, continuous variation of lighting levels can cause eye strain and should be avoided, in particular on long roads.
  • Road lighting provides visual conditions for safe, quick and comfortable movement of Road users.

 Designing Factor for Street Light:

  • The factors that are playing a vital role in the Road Lighting are following.

(A) Type of Road

  • Road Classification

(B) Street Light Pole

  • Street Light Pole Arrangements
  • Placement of Pole

(C) Lighting Fixture

  • Lighting Fixture Mounting Height
  • Lighting Fixture Classification
  • Lighting Fixture Distributor

(D) Lighting Factors

  • Maintenance Factor
  • Coefficient of Utilization

(E) Lighting Uniformity

  • Lighting Uniformity
  • Surrounding Ratio

(F) Lighting Pollution

  • Glare
  • Sky Glow
  • Trespass

(G) Selection of Luminas

  • Type of Light
  • Watt
  • Lumen
  • CRI
  • Efficiency

(A) Road Classification:

Table 4 : Road Classes as per SP 72 (Part 8), IS 1944 (Part 1) and IS 1970

Class A1 Important routes with rapid and dense traffic where safety, traffic speed, and driving comfort are the main considerations
Class A2 Main Roads with considerable volume of mixed traffic, such as main city streets, arterial roads and thoroughfares.
Class B1 Secondary roads with considerable traffic such as main local traffic routes, shopping streets
Class B2 Secondary roads, with light traffic
Class C Lighting for residential and unclassified roads not included in previous groups
Class D Lighting for bridges and flyovers
Class E Lighting for town and city centers
Class F Lighting for roads with special requirement such as roads near air fields, railways and docks

 

TYPE OF ROAD

TYPE OF ROAD DENSITY OF TRAFFIC TYPE EXAMPLE
A Heavy and high speed motorized traffic Road with fixed separators, No crossings for very long distance National highways or state highways or called interstate highways, express ways or motor ways
B Slightly lower density and lower speed traffic termed Road which is made for vehicular traffic with adjoining streets for slow traffic and pedestrians as we find in metros Trunk road or major road in a city
C Heavy and moderate speed traffic Important urban roads or rural roads. they do not interfere with the local traffic within the town Ring roads
D Slow traffic, pedestrians Linking to shopping areas and invariably the pedestrians, approach road Shopping street, trunk road
E Limited speed. Slow or mixed traffic predominantly pedestrians, Local streets, collectors road

(B) Street Light Pole:

(1) Street Light Arrangement:

  • There are four basic types of street lighting layout arrangements used for streets or highways illumination.

(A) One Side Pole Layout:

  • In One Side Pole Layout, all luminaries are located on one side of the road.
  • Road Width: For narrower roads.
  • Pole Height: The installation height of the lamp be equal to or less than the effective width of the road surface.

1

  • Advantage: There are good indelibility and low manufacturing cost.
  • Disadvantage: The brightness (illuminance) of the road on the side where the lamp is not placed is lower than the on which side the light pole is placed.

(B) Both Side Staggered Pole Layout:

  • In the staggered arrangement, the luminaires are placed alternately on each side of the road in a “zig-zag” or staggered fashion.
  • Road Width: For Medium Size roads.
  • Pole Height: The installation height of the lamp is equal or 1.5 time the effective width of the road.

1

  • Advantage: This type of arrangement is better than single side arrangement.
  • Disadvantage: Their longitudinal luminance uniformity is generally low and creates an alternating pattern of bright and dark patches. However, during wet weather they cover the whole road better than single-side arrangements.

(C) Both Side opposite Pole Layout:

  • In Both Side Opposite Pole Layout, the luminaries located on both sides of the road opposite to one another.
  • Road Width: For Medium Size roads.
  • Pole Height: The installation height of the lamp will be 2 to 2.5 time the effective width of the road.

1.jpg

  • Advantage: opposite arrangements may provide slightly better lighting under wet conditions.
  • Disadvantage:
  • If the arrangement is used for a dual carriageway with a central reserve of at least one-third the carriageway with, or if the central reserve includes other significant visual obstructions (such as trees or screens), it effectively becomes two single-sided arrangements and must be treated as such.

 (D) Twin-central Pole Layout:

  • In Twin central arrangement, the luminaries are mounted on a T-shaped in the middle of the center island of the road. The central reserve is not too wide, both luminaires can contribute to the luminance of the road surface on either lane.
  • Road Width: For Large Size roads.
  • Pole Height: The installation height of the lamp be equal to the effective width of the road.

1

  • Advantage: This arrangement generally more efficient than opposite arrangements. However, opposite arrangements may provide slightly better lighting under wet conditions.
  • Disadvantage:

Calculate Size of Pole Foundation & Wind Pressure on Pole


Example:

  • Calculate Pole foundation size and Wind pressure on Pole for following Details.
  • Tubular Street Light Pole (430V) height is 11 Meter which is in made with three different size of Tubular Pipe.
  • First Part is 2.7 meter height with 140mm diameter,
  • Second part of Pole is 2.7 meter height with 146 mm diameter and
  • Third part of Pole is 5.6 meter height with 194 mm diameter.
  • Weight of Pole is 241 kg and there is no any other Flood Light Fixtures Load on Pole.
  • Total Safety Factor is 2.
  • Wind zone category is 3.
  • The Pole is installed in open terrain with well scattered obstructions having height generally between 1.5 m to 10 m.
  • Foundation of pole is 700mm length, 700mm width and 1.95 meter depth. The Average weight of foundation concrete is 2500 Kg/M3.

1

Calculation:

 Wind Pressure according to Location:

  • Wind Zone is 3 so Wind Speed as per following Table.
Basic Wind Speed-Vb (As per IS 802-Part1)
Wind Zone  Basic Wind Speed, vb m/s
1 33
2 39
3 44
4 47
5 50
6 55
  • Wind Speed (vb) = 44Mile/Second.
  • Co-efficient Factor (K0)=1.37
  • K0 is a factor to convert 3 seconds peak gust speed into average speed of wind during 10 minutes period at a level of 10 meters above ground. K0 may be taken as 1.375.
  • The Pole is used for 430Vand wind zone is 3 so Risk Co-efficient (K1) as per following Table
Table 2 Risk Coefficient K1 for Different Reliability Levels and Wind Zones (As per IS 802-Part1)
Reliability  Level Wind Zone-1 Wind Zone-2 Wind Zone-3 Wind Zone-4 Wind Zone-5 Wind Zone-6
1 (Up to 400KV) 1 1 1 1 1 1
2 (Above 400KV) 1.08 1.1 1.11 1.12 1.13 1.14
3 (River Crossing) 1.17 1.22 1.25 1.27 1.28 1.3
  • Risk Co-efficient (K1) =1
  • Terrain category (K2) for Open terrain with well scattered obstructions having height generally between 1.5 m to 10 m is 1 as per following Table
  • Terrain category (K2)=1
Terrain Roughness Coefficient, K2 (As per IS 802-Part1)
Terrain Category Category 1 Category 2 Category 3
Exposed open terrain with no obstruction and in which the average height of any object surrounding the structure is less than 1.5 m. Open terrain with well scattered obstructions having height generally between 1.5 m to 10 m. Terrain with numerous
closely spaced obstructions.
Coefficient, K2 1.08 1 0.85
  • Reference Wind Speed (Vr)= Vb / K0.
  • Reference Wind Speed (Vr)= 44 / 1.37 =32 Mile/Second.
  • Design wind Speed (vd)= Vr X K1 X K2.
  • Design wind Speed (vd)= 32 X 1 X 1 =32 Mile/Second.
  • Design Wind Pressure (Pd)=0.6 x vd2
  • Design Wind Pressure (Pd)=0.6 x (32)2 =614.4 N/m2
  • Design Wind Pressure (Pd)=614.4/10 =61.4 Kg/m2

Foundation Detail:

  • Total Weight =Pole Weight +Foundation Weight.
  • Total Weight = 241 +(0.7×0.7×1.95×2500) =2620.75 Kg
  • Stabilizing Moment = Total Weight X (Foundation Length/2)
  • Stabilizing Moment = 2620.75 X (0.7/2) = 920.41 Kg/Meter.

Pole Detail:

  • First Part of Pole (h1) = 2.7 meter
  • Diameter of First Part (d1) =140mm
  • Second Part of Pole (h2) = 2.7 meter
  • Diameter of Second Part (d2) =146mm
  • Third Part of Pole (h3) = 5.6 meter
  • Diameter of Third Part (d3) =194mm .

Wind Pressure on Pole:

  • Overturning Moment due to the wind on 1st Part of the pole=pdxh1xd1x(h1/2+h2+h3)x0.6
  • Overturning Moment due to the wind on 1st Part of the pole=61.4×2.7x(140/1000)x(2.7/2+2.7+5.61)x0.6
  • Overturning Moment due to the wind on 1st Part of the pole=134.47 Kg/meter—I
  • Overturning Moment due to the wind on 2nd Part of the pole=pdxh2xd2x(h2/2+h3)x0.6
  • Overturning Moment due to the wind on 2nd Part of the pole=61.4×2.7x(146/1000)x(2.7/2+5.61)x0.6
  • Overturning Moment due to the wind on 2nd Part of the pole=112.76 Kg/meter.—-II
  • Overturning Moment due to the wind on 3rd Part of the pole=pdxh3xd3x(h3/2)x0.6
  • Overturning Moment due to the wind on 3rd Part of the pole=61.4×5.6x(194/1000)x(5.6/2)x0.6
  • Overturning Moment due to the wind on 3rd Part of the pole=112.14 Kg/meter.—III
  • Total Overturning Moment on Pole due to Wind=134.47+112.76+112.14=359.36 Kg/meter.

 Safety Factor:

  • Calculated Safety Factor= Stabilizing Moment / Total Overturning Moment on Pole.
  • Calculated Safety Factor=920.41/ 359.36 =2.56.
  • For safe Design Calculated Safety Factor > Safety Factor
  • Here Calculated Safety Factor (2.56) > Safety Factor (2) hence
  • Design is OK
  • B : If Calculated Safety Factor < Safety Factor then Change Foundation Size (Length, width or depth)

 

Calculate Size of Circuit Breaker/ Fuse for Transformer (As per NEC)


  • Calculate Size of Circuit Breaker or Fuse on Primary and Secondary side of Transformer having following Detail
  • Transformer Details(P)= 1000KVA
  • Primary Voltage (Vp)= 11000 Volt
  • Secondary Voltage (Vs)= 430 Volt
  • Transformer Impedance= 5%
  • Transformer Connection = Delta / Star
  • Transformer is in unsupervised condition.

Calculations:

  • Transformer Primary Current (Ip)= P/1.732xVp
  • Transformer Primary Current (Ip)=1000000/1.732×11000=49Amp
  • Transformer Secondary Current (Is)= P/1.732xVs
  • Transformer Secondary Current (Is)=1000000/1.732×430=71Amp
  • AS per NEC 450.3, Max.Rating of C.B or Fuse is following % of its Current according to it’s Primary Voltage,% Impedance and Supervised/Unsupervised Condition.

Max Rating of Over current Protection for Unsupervised Transformer More than 600 Volts (As per NEC)

%Imp Primary secondary
>600Volt >600Volt <600Volt
C.B Fuse C.B Fuse C.B/Fuse
 Up to 6% 600% 300% 300% 250% 125%
More than 6% 400% 300% 250% 225% 125%

 

Max Rating of Over current Protection for Supervised Transformer More than 600 Volts (As per NEC)

%Imp Primary secondary
>600Volt >600Volt <600Volt
C.B Fuse C.B Fuse C.B/Fuse
 Up to 6% 600% 300% 300% 250% 250%
More than 6% 400% 300% 250% 225% 250%

 

Max Rating of Over current Protection for Transformers Primary Voltage Less than 600 Volts (As per NEC)

Protection Primary Protection Secondary Protection
Method More than 9A 2A to 9A Less than 2A More than 9A Less than 9A
Primary only protection 125% 167% 300% Not required Not required
Primary and secondary protection 250% 250% 250% 125% 167%

 

Size of Fuse / Inverse Time C.B as per NEC (Amp)

1 25 60 125 250 600 2000
3 30 70 150 300 700 2500
6 35 80 160 350 800 3000
10 40 90 175 400 1000 4000
15 45 100 200 450 1200 5000
20 50 110 225 500 1600 6000

For Primary Side:

  • Transformer Primary Current (Ip) =52.49Amp and impedance is 5%
  • As per above table in not supervised condition Size of Circuit Breaker= 600% of Primary Current
  • Size of Circuit Breaker = 52.49 x 600% =315Amp
  • If Transformer is in supervised condition then Select Circuit Breaker near that size but if Transformer is in unsupervised condition then Select Circuit Breaker next higher size.
  • Rating of Circuit Breaker =350Amp (Next Higher Size of 300Amp)
  • Size of Fuse = 52.49 x300% =157Amp
  • Rating of Fuse =160Amp (Next Higher Size of 150Amp)

For Secondary Side:

  • Transformer Secondary Current (Is) =1342.70Amp and impedance is 5%
  • As per above table in not supervised condition Size of Circuit Breaker= 125% of Secondary Current
  • Size of Circuit Breaker = 1342.70 x 125% =1678Amp
  • If Transformer is in supervised condition then Select Circuit Breaker near that size but if Transformer is in unsupervised condition then Select Circuit Breaker next higher size.
  • Rating of Circuit Breaker =2000Amp (Next Higher Size of 1600Amp)
  • Size of Fuse = 1342.70 x125% =1678Amp
  • Rating of Fuse =2000Amp (Next Higher Size of 1600Amp)

 Results:

  • Size of Circuit Breaker on Primary Side=350Amp
  • Size of Fuse on Primary Side=160Amp
  • Size of Circuit Breaker on Secondary Side=2000Amp
  • Size of Fuse on Secondary Side=2000Amp

Selection of Various Types of UPS (Part-2)


(2) Line-Inter active UPS:

  • Working Principle of Line Interactive UPS is same as OFF Line/ stand UPS. It connected directly from mains, switching to battery (via the inverter) in mains Power cut condition.
  • The designing of line interactive UPS is same as OFF Line UPS in addition the design Line Interactive generally includes an automatic voltage regulator (AVR) or a tap-changing transformer. This enhances the regulation of voltage by regulating transformer taps as the input voltage differs.
  • The main difference between an off-line and a line-interactive UPS is that a line-interactive UPS in the stand-by mode has active voltage regulation.
  • Voltage regulation is a significant feature when the conditions of a low voltage exist, otherwise the UPS would transfer to battery and then finally to the load. The usage of more common battery can cause early battery failure.
  • It typically uses either a Ferro resonant transformer or a buck-boost transformer. Both helps to reduce the frequency of transfers to battery, slightly improving efficiency and reducing battery wear.
  • Ferro resonant designs also offer power conditioning and tight voltage regulation, as well as an energy store that can maintain uninterrupted power supply output while the inverter switches on.

Circuit Diagram:

1

Working Function:

  •  Normal Condition:
  • In Normal Power Condition, power supply will continuously provide to Load with some filtering and voltage regulation circuit.
  • During normal operation, the Line Interactive UPS takes utility power and passes it through a transformer with various tap selections on the output. When utility power is high, the Line Interactive UPS selects a tap to lower (buck) the output voltage. Similarly, when the utility voltage is low, the UPS selects a tap to increase (boost) the output voltage.
  • In Normal Condition Battery is charged continuous charge through Battery Charger
  • Battery charger convert AC power to DC Power and this DC Power charged Battery.
  • Power outage Condition:
  • When utility power fails, the device will start its internal inverter Circuit by Mechanical Switch.
  • Mechanically transfer Switch Transfer from utility power to Battery Power, inverter output.
  • This transfer can take as 2 to 4 ms.

 Advantage:

  • small Size
  • Low cost
  • High Efficiency (because less power conversion is when AC input is present).
  • Sine Way Output.
  • Battery life is good compared to OFF Line UPS.
  • Voltage regulation is fair (more than OFF Line UPS but Less than ON Line UPS)
  • EMI/RFI/Noise Rejection is good.
  • Change over Time is 2 to 4 Milliseconds.
  • Lower electricity consumption (less costly to operate).
  • Higher reliability (Lower component count and lower operating temperatures).

 Disadvantage:

  • No isolation between main supply and load
  • Higher Heat Output
  • More Expensive
  • Problematic with power factor corrected loads.

Applications:

  • For small business.
  • IT Racks, Network Switches, Medical Instrument System where data loss is a serious problem.
  • The line interactive UPS may not be the appropriate choice for installations where AC power is unstable or highly distorted, because battery power will be used too often to keep the UPS output within specifications.

 Capacity:

  • UPS in the range of 500VA to 5kVA power.

 (3) ON Line UPS/ Double Conversion UPS

  • It is truly uninterrupted power system (UPS) provide continuous power to load in any condition.
  • Online UPS sometimes called “double conversion” UPS. 
  • Today most users with highly-critical loads are choose online UPS .It is used to protect sensitive equipment and data from mains problems at all times with any extra cost.
  • This UPS have no power transfer switches and therefore no transfer time is existed under the mains power failure. Thus this is truly an uninterrupted system.
  • In Online UPS to maintain the charge of the battery, a battery charging unit is continuously powered from the AC mains.
  • Online UPSs are often called ‘double conversion’ types because incoming power is Firstly converted once AC to DC for the battery and then back Secondly Converter DC to AC before reaching the load which is therefore well-insulated from the mains like an electrical firewall between the incoming power and sensitive electronic equipments. It also control of the output voltage and frequency regardless of the input voltage and frequency.
  • The online UPS continuously filters power through the battery before sending it to your computer.
  • By contrast, online UPS systems draw power through the power conditioning and charging components during normal operation, so the load always receives conditioned power rather than raw mains.

 Circuit Diagram:

1

Working Function:

  • The designing of this UPS is similar to the Standby UPS, excluding that the primary power source is the inverter instead of the AC main.
  • In this UPS design, any cutoff of input AC Supply does not cause triggering of the transfer switch, because the input AC Supply is charging the backup battery source which delivers power to the o/p inverter. So, during failure of input AC Supply, this UPS operation results in no transfer time.
  • The Transfer switch will automatically transfer the load to mains in case of overload or UPS failure.
  • Normal Condition or Power outage Condition:
  • In Normal Power Condition, power supply will continuously feed from the Inverter, providing conditioned, stabilized sinusoidal voltage.
  • Input Power is filter and regularized by RFI Filter circuit then it is feed to Battery charger which is convert AC Power to DC Power. This DC Power is charged Battery continuously.
  • Battery DC power is converted to AC power by Inverter Circuit.

 Advantage:

  • The cost is high compare to other type of UPS.
  • It provides isolation between main supply and load.
  • The output is pure Sign wave.
  • 100% Power Conditioning
  • Constant voltage output.
  • Correction of Input Power Factor
  • Zero transfer time
  • The output voltage is free from distortion due to inverter is always ON.
  • It offers the best power protection, covering any and all types of mains disturbances of supply such as blackout, brownouts, spikes etc are absent in the output.
  • Voltage regulation is better
  • Transfer time is practically zero since inverter is always ON.
  • High Reliability, Units can be connected in parallel redundant configuration.
  • This is the best choice, considering such issues as modularity, ability to work from generator, power factor correction, maintenance, hot swapping, fault clearing, supervising, and communicating.

 Disadvantages:

  • More Expensive
  • Lower Efficiency (Due to inverter is always ON).
  • Higher Heat Output
  • Higher battery TCO
  • Higher operating cost (Supplies power is charge Battery Charger and Inverter both).
  • The wattage of the rectifier is increased since it has to supply power to inverter as well as charge battery

 Applications:

  • It the preferred choice for most business applications.
  • Induction motor drives and similar other motor control applications.
  • Medical equipments and Intensive care units.
  • Electronics manufacturers.
  • Data and call centers.
  • TV stations
  • Production-based manufacturers.

 Capacity:

  • From 1 KVA up to 5 MVA.

 Comparison of all types of UPS: 

Comparison of all types of UPS

Features OFFLINE Line-Interactive ON Line
Size of UPS Compact Moderate Big
Cost Cheap Cheaper expensive
Circuit Simplicity Simple Simple Complicated
Transfer Time 4 to 10 millisecond 2 to 4 millisecond 0
Efficiency High Moderate Low
Power Consumption Less Less High
Battery Charging Time More More Less
Battery Life Less Less More
Backup Time Short Short More
Surge Protection
Voltage Regulation Low Better Best
Load Protection Low Better Best
Size Up to 2KVA Up to 5KVA 5 to 500KVA
Reliability Low Better Best
Isolation from Mains Not Available Not Available Available
Noise Reduction Good Good Best
Frequency Stability Not Stable Not Stable Always Stable
Voltage Conditioning Low Better Best
Cost/KVA Low Medium High
Inverter always Operating Yes Yes Yes
Application For Domestic Desktops IT Racks ,Switches ,Distributed Server Data Center, Hospital, Banks
Capacity Up to 800VA 800VA to 1500VA 1000VA to 5000VA

Selection of UPS:

 (1) Size of the UPS (VA & Watts)

  • To decide Power Capacity of the required UPS, we should decide which should be protected and its power consumption in Amps, VA, or Watt.

(2) Back-up time

  • Battery Backup time is the time that batteries are able to back-up operation and feed the load upon failure of utility power. Load consumption and size of UPS batteries decide the back-up time.

(3) Type of the UPS you need

  • UPS’s are divided to three main classes.
  • The Off Line (Stand-by) UPS is the simplest and the least expensive.
  • The Line Interactive type, which overcomes the major disadvantages of  the off-line unit  
  • The On-Line UPS, which provides the best power protection.

(4) Cost:

  • For applications where low cost is critical and it does not matter if backup times are short, an OFF Line UPS is proper solution. However it will not provide adequate protection against spikes or sags from the grid.
  • For applications that require complete isolation from any changes in grid power, such as many medical applications then On Line UPS is the best solution.
  • For applications where power losses due to inefficiencies are less of a concern and eliminating the delay from grid power available to back power is paramount, online UPS is the only solution.
  • For typical applications where conditioning Power is required and very short transfer times from grid to backup power are acceptable and daily energy consumption is a concern, Line Interactive is the preferred solution

 (5) Non-Essential or Critical Load

  • For small office where PC loads is less and small network data protection is required, a small single-phase UPS is often an adequate solution.
  • Most single-phase UPSs use off-line or line-interactive topologies.
  • If the equipment to be protected is critical, an online UPS is the best choice.
  • For loads above 10kVA, the most practical solution is a three-phase UPS, which is most normally with true-online topology. Three-phase online UPSs offer the advantage of providing centralized protection using a single UPS.

 (6) Efficiency:

  • Efficiency is mainly affected on UPS design or operating mode.
  • standby and line-interactive UPSs are more energy efficient than ON Line UPSs because there is no power conversion from AC to DC and then back to AC
  • Efficiency is a factor of UPS size. Larger UPS modules typically have higher energy efficiency than smaller ones, because the support power required for control electronics and auxiliary components becomes a smaller portion of the total capacity of the UPS system.
  • For example, a 500 kW UPS module of a given design would typically be more efficient than a 5 kW UPS module of the same design.

Efficiency of UPS

Capacity Size Standby UPS Line-interactive UPS On Line UPS
5 kW 95 % 96  % 91 %
100 kW  98 % 97 % 98 %
500 kW 99% 98 % 99%

(7) Form Factor:

  • Form factor refers to the the outer-shape of the unit. The Form Factor refers outer shape of UPS.
  • Tower: This is smaller and a stand-alone unit, and It is primarily designed for simple home/office setups.
  • Rack mounted: is larger, designed for a standard rack shelf, and is primarily used for more complex commercial operations.

(8) Noise

  • UPS fan noise may or may not be an issue as per your requirement.
  • Smaller UPS does not normally require a fan for cooling, but larger ones often will.
  • If r work requires perfect silence, make sure your UPS is fan-free.

Resolve Power Quality problem by Type of UPS:

Power Quality Problems & solution by UPS

Power Quality

Problem

Description Effect Solved by UPS
Temporary Interruption Accidental total loss of utility power  (Seconds to minutes) Equipment shutdown, loss of  data, file , hard disk and operating system Corruption Off-line – Yes

Line-interactive – Yes

On-line – Yes

Long-Term

Interruption

Accidental total loss of utility power (minutes to Hour) Equipment shutdown, loss of  data, file , hard disk and operating system Corruption Off-line – No

Line-interactive –No

On-line – Yes

Momentary

Interruption

Very short planned or

Accidental power loss.

(Milliseconds to seconds)

Computer and network equipment reboots or hangs, loss of work and data, file Off-line – Maybe

Line-interactive – Maybe

On-line – Yes

Sag or Under-Voltage A decrease in utility

voltage Sags  (Milliseconds to a few seconds)

Shrinking display screens,

Computer hangs or reset,

equipment power supply

damage, loss of data, file

Off-line – No

Line-interactive – Yes

On-line – Yes

Swell or Over-Voltage An increase in Utility

Voltage ( Milliseconds to a

few seconds)

Permanent equipment damage, Computer and network equipment reboots or hangs, loss of data Off-line – No

Line-interactive – Yes

On-line – Yes

Transient, Impulse or

Spike

A sudden change in

voltage up to several

hundreds to thousands of

volts (Microseconds)

Network Errors, Burned or

damaged equipment, computer and network

equipment reboots or hangs,

loss of work and data, file

Off-line – Yes

Line-interactive – Yes

On-line – Yes, Higher level of protection.

Noise An unwanted electrical

signal of high frequency

from other equipment

Slow LAN, audible noise in

telephone and audio equipment.

 

Off-line – No

Line-interactive – No

On-line – Yes

Harmonic Distortion An alteration of the pure

sine wave, due to nonlinear

loads

Causes motors, transformers

and wiring to overheat, lowers operating efficiency

Off-line – No

Line-interactive – No

On-line – Yes

 

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