Safety Clearance Recommendations for Transformer _ EEP

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12/17/2013 Safety Clearance Recommendations for Transformer | EEP

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Safety Clearance Recommendations for

Transformer

Safety Clearance Recommendations for Transformer (on photo 10/0.4 kV transformer

substation by FIMA)

Clearance Tables

1. Clearance from Outdoor Liquid Insulated Transformers to Buildings (NEC)

2. Clearance between Two Outdoor Liquid Insulated Transformers (NEC)

3. Dry Type Transformer in Indoor Installation (NES 420.21)

4. Dry Type Transformer in Outdoor Installation (NES 420.22)

5. Non Flammable Liquid-Insulated Transformer in Indoor Installation (NES 420.21)

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6. Oil Insulated Transformer in Indoor Installation (NES 420.25)

7. Transformer Clearance from Bui lding (IEEE Stand.)

8. Transformer Clearance Specificat ions (Stand. Georgia Power Company)

9. Clearance of Transformer-Cable-Overhead Line (Stand. Georgia Power Company)

Clearance from Outdoor Liquid Insulated Transformers to Buildings

(NEC)

LiquidLiquid

Volume (m3)

Fire

Resistant

Wall

Non-

Combustible

Wall

Combustible

Wall

Vertical

Distance

Less

Flammable

NA 0.9 Meter 0.9 Meter 0.9 Meter 0.9 Meter

38 m3 4.6 Meter 4.6 Meter 15.2 Meter15.2

Meter

Mineral

Oil

19 m3 7.6 Meter 15.2 Meter 30.5 Meter 30.5Meter

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Clearance between Two Outdoor Liquid Insulated Transformers (NEC

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Liquid Liquid Volume (m3) Distance

Less

Flammable

NA 0.9 Meter

38 m3 7.6 Meter

Mineral Oil

19 m3 15.2 Meter

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Dry Type Transformer in Indoor Installation (NES 420.21)

Voltage Distance (min)

Up to 112.5 KVA

300 mm (12 in.) from combustible material

unless separated from the combustible

material by a heat-insulated barrier.

Above 112.5 KVAInstalled in a transformer room of fire-

resistant construction.

Above 112.5 KVA with Class

155 Insulation

separated from a fire-resistant barrier not

less than 1.83 m (6 ft) horizontally and 3.7

m (12 ft) vertically

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Dry Type Transformer in Outdoor Installation (NES 420.22)


Above 112.5 KVA with Class

155 Insulation

separated from a fire-resistant barrier not

less than 1.83 m (6 ft) horizontally and 3.7

m (12 ft) vertically

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Non Flammable Liquid-Insulated Transformer in Indoor Installation

(NES 420.21)


Over 35KV

Installed indoors Vault (Having liquid confinement area

and a pressure-relief vent for absorbing any gases generated

by arcing inside the tank, the pressure-relief vent shall be

connected to a chimney or flue that will carry such gases

to an environmentally safe area

Above 112.5 KVA Installed in a transformer room of fire-resistantconstruction.

Above 112.5 KVA

(Class 155 Insulation)

separated from a fire-resistant barrier not less than 1.83 m

(6 ft) horizontally and 3.7 m (12 ft) vertically

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Oil Insulated Transformer in Indoor Installation (NES 420.25)


Up to 112.5 KVAInstalled indoors Vault (With construction of reinforced

concrete that is not less than 100 mm (4 in.) thick.

Up to 10 KVA &

Up to 600V

Vault shall not be required if suitable arrangements are made

to prevent a transformer oil fire from igniting

Up to 75 KVA &

Up to 600V

Vault shall not be required if where the surrounding Structure

is classified as fire-resistant construction.

Furnace

transformers (Up to

75 kVA)

Installed without a vault in a building or room of fire

resistant construction

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Transformer Clearance from Building (IEEE Stand)

Transformer Distance from Building (min)

Up to 75 KVA 3.0 Meter

75 KVA to 333

KVA6.0 Meter

More than 333 KVA 9.0 Meter

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Transformer Clearance Specifications (Stand: Georgia Power

Company)

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Description of Clearance Distance (min)

Clearance in front of the transformer 3.0 Meter

Between Two pad mounted transformers (including

Cooling fin)2.1 Meter

Between Transformer and Trees, shrubs, vegetation(

for unrestricted natural cooling ) 3.0 Meter

The edge of the concrete transformer pad to nearest

the building 4.2 Meter

The edge of the concrete transformer pad to nearest

building wall, windows, or other openings3.0 Meter

Clearance from the transformer to edge of (or

Canopy) building (3 or less stories)3.0 Meter

Clearance in front of the transformer doors and on

the left side of the transformer, looking at it from

the front (For operation of protective and switching

devices on the unit)

3.0 Meter

Gas service meter relief vents. 0.9 Meter

Fire sprinkler values, standpipes and fire hydrants 1.8 Meter

The water’s edge of a swimming pool or any body of

water.4.5 Meter

Facil it ies used to dispense hazardous l iquids or gases 6.0 Meter

Facilities used to store hazardous liquids or gases 3.0 Meter

Clear vehicle passageway at all times, immediately

adjacent of Transformer3.6 Meter

Fire safety clearances can be reduced by building a

suitable masonry fire barrier wall (2.7 Meter wide

and 4.5 Meter Tall) 0.9 Meter from the back or sideof the Pad Mounted Transformer to the side of the

combustible wall

Front of the transformer must face away from the

building.

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Clearance of Transformer-Cable-Overhead Line (Stand: Georgia

Power Company)

Description of

Clearance

Horizontal Distance (mm)

to pad-

mounted

transformers

to buried

HV cable

to

overhead

HV Line

Fuel tanks 7.5 Meter 1.5 Meter 7.5 Meter

Granaries 6.0 Meter 0.6 Meter 15 Meter

Homes 6.0 Meter 0.6 Meter 15 Meter

Barns, sheds, garages 6.0 Meter 0.6 Meter 15 Meter

Water wells 1.5 Meter 1.5 Meter 15 Meter

Antennas 3.0 Meter 0.6 Meter

Height of

Antenna +

3.0 Meter

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Safety Clearance Recommendations for Transformer _ EEP