Clearance Tables
- Clearance from Outdoor Liquid Insulated Transformers to Buildings (NEC)
- Clearance between Two Outdoor Liquid Insulated Transformers (NEC)
- Dry Type Transformer in Indoor Installation (NES 420.21)
- Dry Type Transformer in Outdoor Installation (NES 420.22)
- Non Flammable Liquid-Insulated Transformer in Indoor Installation (NES 420.21)
- Oil Insulated Transformer in Indoor Installation (NES 420.25)
- Transformer Clearance from Building (IEEE Stand.)
- Transformer Clearance Specifications (Stand. Georgia Power Company)
- Clearance of Transformer-Cable-Overhead Line (Stand. Georgia Power Company)
Clearance from Outdoor Liquid Insulated Transformers to Buildings (NEC)
| Liquid | Liquid 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 | 1.5 Meter | 1.5 Meter | 7.6 Meter | 7.6 Meter | |
| >38 m3 | 4.6 Meter | 4.6 Meter | 15.2 Meter | 15.2 Meter | |
| Mineral Oil | <1.9 m3 | 1.5 Meter | 4.6 Meter | 7.6 Meter | 7.6 Meter |
| 1.9 m3 to 19 m3 | 4.6 Meter | 7.6 Meter | 15.2 Meter | 15.2 Meter | |
| > 19 m3 | 7.6 Meter | 15.2 Meter | 30.5 Meter | 30.5 Meter |
Clearance between Two Outdoor Liquid Insulated Transformers (NEC)
| Liquid | Liquid Volume (m3) | Distance |
| Less Flammable | NA | 0.9 Meter |
| <38 m3 | 1.5 Meter | |
| >38 m3 | 7.6 Meter | |
| Mineral Oil | <1.9 m3 | 1.5 Meter |
| 1.9 m3 to 19 m3 | 7.6 Meter | |
| > 19 m3 | 15.2 Meter |
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 KVA | Installed 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 |
Dry Type Transformer in Outdoor Installation (NES 420.22)
| Voltage | Distance (min) |
| 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 |
Non Flammable Liquid-Insulated Transformer in Indoor Installation (NES 420.21)
| Voltage | Distance (min) |
| 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-resistant construction. |
| 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 |
Oil Insulated Transformer in Indoor Installation (NES 420.25)
| Voltage | Distance (min) |
| Up to 112.5 KVA | Installed 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 |
Transformer Clearance from Building (IEEE Stand)
| Transformer | Distance from Building (min) |
| Up to 75 KVA | 3.0 Meter |
| 75 KVA to 333 KVA | 6.0 Meter |
| More than 333 KVA | 9.0 Meter |
Transformer Clearance Specifications (Stand: Georgia Power Company)
| 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 openings | 3.0 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 |
| Facilities used to dispense hazardous liquids 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 Transformer | 3.6 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 side of the Pad Mounted Transformer to the side of the combustible wall | |
| Front of the transformer must face away from the building. |
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 |
Related electrical guides & articles
Jignesh Parmar
Electrical Middle management professional having more than 22 years rich and dynamic experience in Project Execution / Project Management / Designing / Maintenance diversifies from Electrical Power Transmission (400KV/220KV/66KV)- Distribution(11KV/220V) to Lifts-HVAC-Ventilation-Fire Fighting-Fire Alarm-Lifts-CCTV-Stack Parking Works (High Rise Buildings, Townships, Shopping Complex, Commercial Complex, School, Temple).Profile: Jignesh Parmar
please share fire safety requirement for oil type inddor transformer for 2mVA.
can I fix the transformer above the private road in a villa project by making a concrete slab and taking other required precaution?
A new transformer is installing in front of my residencial boundary wall. Is it legal?
What should be the minimum distance clearance between the two 2000 KVA liquids insulated indoor transformers?
Could you provide clause references for the first two tables? I cannot find these clearances in the NEC (2020 edition). Also tables 3-5, labeled NES … are likely NEC. And, the similar question regarding the reference to an IEEE Standard.
for the finalization of the distribution transformer 2/2.5/3.15 MVA rating what are the main considerable points to finalize?
Please let me know the Minimum distance required between 33KV HT underground cable and 200LPM gas bank.
SEPARATION DISTANCE BETWEEN 1600 KVA 11/433V OIL COOLED TRANSFORMERS AND 500 KVA DG ST
Please let ne know the minimum clearance between 33/.415kv,200 kva transformer to Oil pipeline .
Is there any standards available for this clearance ?
Please, what should be the distance to be observed between a residential/office building to a 100 kv diesel power generator ..? Please what distance apart should be maintained
Please, what should be the distance to be observed between a residential/office building to a 33 kv diesel power generator ..? Please what distance apart should be maintained
I WANT TO KNOW THE DISTANCE BETWEEN TWO 132 /33 KV 63 MVA X’MER IN THE GRID ( SUBSTATION ).WHAT IS RULE OF ELECTRICITY PLEASE SUGGEST.
Dear sir,
I want to construct house near a grid station
What should be the horizontal safe distance of my house and heavy transformer of grid station.
Thanks
What should be the safe distance of a transformer from the Control system(PLC) Cabinet. So that it may not effect(4 to 20mAmp) Control signals
what are the pros/cons in stacking indoor transformers?
Sir contractor 440 volt transformers installed closer to my house please suggest me how distance between home and transformers
UP TO WHAT CAPACITY FIRE PROTECTION WALL REQUIRED FOR OIL FILLED POWER TRANSFORMERS
Take a look at this document, hope it will shed a light on this issue, which is very important I would say.
https://axaxl.com/-/media/gaps/592____0.pdf
Dear Sir,
Please provide the NEC reference Number regarding minimum distance between two outdoor transformer?
I live in an apartment and from the electric office a transformer is being planted very near my building and outside my window. So , in this circumstance what should I do and what should be the check points and for complain where sholud I lodge them? Please help. Awaiting your early response.
Mr. Prasenjit Sardar, I have an exactly similar problem. Have you got answer to your problem from any source ? If yes, please let me know the details as it will help me a lot. I am particularly interested to know what should be the minimum distance they should maintain from building line / property line for a 6 KV / 430 V transformer ?
Dear Sir,
We are installing Dry type transformer of capacity 2750 KVA (11KV/433 V) inside the container with DNV certified 2.7.2 Pressurized container as the area is hazardous area Please suggest what should be the minimum distance of the transformer from the walls of the container. the walls of the container is of class A60. Also suggest the distance between two transformer as we are placing 2 transformer on the same offshore platform.
What is the max # of transformer can be located in one room with respect to fire/safety
Thanks for the valuable information and my comment is what is the fire min separation distance between TRFS located inside closed space?
Thanks for the useful article.
Could you let me know “NES”??
In the middle of the article, there is “NES 420.22 -Dry type transformaer”.
Is this the first letter of National Electric Safety Code? or Something?
I would really appreciate your help.
I would use both measurement units, Imperial and metric?
Also you should have referenced NFPA 850, UL and FM global.
Thanks,
A.
For tables 1 and 2, where exactly is this table referencing in the NEC? I’ve scoured all over article 450 and I don’t see anything with specific distances.
Hello,
Two days back punjab state elect. Board put on of tranceformer in front of my residental plot. The clearence from my plot to tranceformer pole is about 6 inches. I was planning to start construction this month. I want that traceformer should be fitted on some where else. Please can you advise how i can proceed. Do you have legal information about this issue. Even i planned to sale this plot but no one like to buy this plot.
thanks
gracias desde honduras
This is a very useful web site providing and sharing the design standards pertaining to electrical engineering. Recommeded for all serious electrical engineers.
Thanks Sanath!