Electrical Clearance in Substation
April 6, 2011 59 Comments
Minimum Clearance in Substation:
| Voltage | Highest Voltage | Lighting Impulse Level (Kvp) | Switching Impulse Level (Kvp) | Minimum Clearance | Safety Clearance(Mt) | Ground Clearance(Mt) | |
| Phase-Earth | Phase-Phase | ||||||
| 11KV | 12KV | 70 | 0.178 | 0.229 | 2.600 | 3.700 | |
| 33KV | 36KV | 170 | 0.320 | 0.320 | 2.800 | 3.700 | |
| 132KV | 145KV | 550 | 1.100 | 1.100 | 3.700 | 4.600 | |
| 650 | 1.100 | 1.100 | 2.700 | 4.600 | |||
| 220KV | 245KV | 950 | 1.900 | 1.900 | 4.300 | 5.500 | |
| 1050 | 1.900 | 1.900 | 4.300 | 5.500 | |||
| 400KV | 420KV | 1425 | 1050(P-E) | 3.400 | 4.200 | 6.400 | 8.000 |
Electrical Clearance in Substation:
| Voltage | Height of I Bay From Ground (Mt) | Height of II Bay From Ground (Mt) | Bay Width (Mt) | Phase-Phase (Mt) | BetweenEquipment | Earth Wire From Ground |
| 132KV (Single) | 8.0 | – | 11.0 | 3.0 | 3.0 | 10.5 |
| 220KV (Single) | 12.5 | – | 18 | 4.5 | 4.5 | 15.5 |
| 220KV (Double) | 18.5 | 25 | 25 | 4.5 | 4.5 | 28.5 |
| 400KV | 15.6 | 22 | 22.0 | 7.0 | >6.0 | 30.0 |
Standard Bay Widths in Meters:
| Voltage | Bay Width (Meter) |
| 11KV | 4.7 Meter |
| 33KV | 4.7 Meter |
| 66KV | 7.6 Meter |
| 132KV | 12.2 Meter |
| 220KV | 17 Meter |
| 400KV | 27 Meter |
Standard Bus and Equipment Elevation
| Voltage | Equipment live Terminal Elevation (Meter) | Main Bus | Take of Elevation (Meter) | |
| Low | High | |||
| 11 KV/33KV | 2.8To 4 | 5.5 To6.5 | 9 | 6.5To8.5 |
| 66KV | 2.8To 4 | 6To8 | 9To 10.5 | 9.5 |
| 132KV | 3.7To5 | 8To9.5 | 13.5To14.5 | 12To12.5 |
| 220KV | 4.9To5.5 | 9To13 | 18.5 | 15To18.5 |
| 400KV | 8.0 | 15.5 | – | 23 |
Phase spacing for strung Bus:
| Voltage | Clearance |
| 11KV | 1300 mm |
| 33KV | 1300 mm |
| 66KV | 2200 mm |
| 132KV | 3000 mm |
| 220KV | 4500 mm |
| 400KV | 7000 mm |
Minimum Clearance of Live Parts from Ground:
| Voltage | Minimum Clearance to Ground (Mt) | Section Clearance (Mt) |
| 11KV | 3.700 | 2.600 |
| 33KV | 3.700 | 2.800 |
| 66KV | 4.600 | 3.000 |
| 132KV | 4.600 | 3.500 |
| 220KV | 5.500 | 4.300 |
| 400KV | 8.000 | 7.000 |
Insulator String:
| Voltage | No of Suspension String | Length (mm) | No of Disc for Tension String | Length in (mm) |
| 66KV | 5 | 965 | 6 | 1070 |
| 132KV | 9 | 1255 | 10 | 1820 |
| 220KV | 14 | 1915 | 15 | 2915 |
| 400KV | 23 | 3850 | 2 X 23 | 5450 |
Nominal Span:
| Voltage | Normal Span (Meter) |
| 66KV | 240-250-275 |
| 132KV | 315-325-335 |
| 220KV | 315-325-335 |
| 400KV | 315-325-335 |
Minimum Ground Clearance:
| Voltage | Ground (Meter) |
| 66KV | 5.5 |
| 132KV | 6.1 |
| 220KV | 7.0 |
| 400KV | 8.0 |
| 800KV | 12.4 |
Indoor Substation Minimum Clearances
| Distance | Descriptions |
| 0.9 Meter | Horizontally between any item of equipment and thesubstation wall |
| 0.6 Meter | Horizontally between any Two items of equipment |
| 1.2 Meter | Horizontally in front of any HV switchgear |
Clearance of Conductor on Tower
| Voltage | Tower Type | Vertical Space (Mt) | Horizontal Space(Mt) | Total Height From Ground(Mt) |
| 66KV | A | 1.03 | 4.0 | 15.91 |
| B | 1.03 | 4.27 | 15.42 | |
| C | 1.22 | 4.88 | 16.24 | |
| 132KV | A | 7.140 | 2.17 | 23.14 |
| B | 4.2 | 6.29 | 22.06 | |
| C | 4.2 | 7.15 | 22.68 | |
| D | 4.2 | 8.8 | 24.06 | |
| 220KV | A | 5.2 | 8.5 | 28.55 |
| B | 5.25 | 10.5 | 29.08 | |
| C | 6.7 | 12.6 | 31.68 | |
| D |
NORMS OF PROTECTION FOR EHV CLASS POWER TRANSFORMERS
| Voltage ratio & capacity | HV Side | LV Side | Common relays |
| 132/33/11KV up to 8 MVA | 3 O/L relays + 1 E/L relay | 2 O/L relays + 1 E/L relay | Buchholz, OLTC Buchholz, OT, WT |
| 132/33/11KV above 8 MVA and below 31.5 MVA | 3 O/L relays + 1 dir. E/L relay | 3 O/L relays + 1 E/L relay | Differential, Buchholz, OLTC Buchholz, OT, WT |
| 132/33KV, 31.5 MVA & above | 3 O/L relays + 1 dir. E/L relay | 3 O/L relays + 1 E/L relay | Differential, Over flux,Buchholz, OLTC PRV, OT, WT |
| 220/33 KV, 31.5MVA & 50MVA 220/132KV, 100 MVA | 3 O/L relays + 1 dir. E/L relay | 3 O/L relays + 1 dir. relay | Differential, Over flux,Buchholz, OLTC PRV, OT, WT |
| 400/220KV 315MVA | 3 directional O/L relays (with dir. High set) +1 directional E/L relays. Restricted E/F relay + 3 Directional O/L relays for action | 3 directional O/L relays (with dir. High set)+1 directional E/L relays. Restricted E/F relay | Differential, Over flux,Buchholz, OLTC PRV, OT, WT and overload (alarm) relay |
The bottom most portion of any insulator or bushing in service should be at a minimum height of 2500 mm above ground level.
Location of L.A (From T.C Bushing):
| Voltage | BIL KV Peak | Distance (Mt) |
| 11KV | 75 | 12 |
| 33KV | 200 | 15 |
| 66KV | 325 | 24 |
| 132KV | 550 | 35 |
| 220KV | 900 To 1050 | Close To T.C |
| 400KV | 1425 To 1550 |
JIGNESH PARMAR
I am a chief engineer attached to Ceylon Electricity Board Srilanka.I conduct lecture for CEB
engineers,electrical superintendents,technical staff therefore i need tecnical information for overhead lines,substation and ddlo,lighting arrester installation etc
thanking you
Krishnamoorthy
PLEASE SENT APROJECT ABOUT SUBSTATION
Could i have the various references for clearnace w.r.t National/International standard, for indoor s/s upto 33 kv level also……….
Can you please explain me the difference between ground clearance and earth clearance
i am from Bhutan and i would like to know that my small land is near to the 66KV transmission line, And will there be safe enough for me to construct building near to the line and will there be no problem as such in the longer duration.
please refer http://electricalnotes.wordpress.com/2011/04/22/minimum-electrical-clearance-2/
Clearances from Buildings of high and extra-high voltage lines IE Rule 80
Vertical Distance
High voltage lines up to 33KV = 3.7 Meter
Extra High Voltage = 3.7 Meter + Add 0.3 meter for every additional 33KV
Horizontal clearance between the conductor and Building
High Voltage Up to 11 KV =1.2 Meter
11KV To 33KV = 2.0 Meter
Extra High Voltage = 2.0 Meter + Add 0.3 meter for every additional 33KV
my doubt was cleared with this reply…Thank you Mr.Jignesh
Dear Jignesh,
Excellent compilation! What is the difference between ‘min clearance to ground’ and sectional clearance?
thank you and regards.
Really Helpful Notes
May i know when operating the 11kV OR 33kV Air Break Isolator from ground how to determine which class of insulation glove to wear for the safety protection.
Dear sir.
I am Electrical sr engineer.we using 11KV/0.415KV substation for construction supply.
1.There four substations in various area.when we charging the transformers one bye first time no any problem.but next day we are charging the transformers.first transformer will charging with any problem but we go charge the second trans that incoming surge arrest er will burst.
2.what is reason sure arrester will burst.
I have observed following possibility in past for blasting of LA at DP structure.
(1) May be Phase to ground Fault ( May be touch branches of tree with phase in distribution Line)
(2) Failure of PIN Insulator of Distribution Line
(3) wrong connection of LA (You face problem while charging System so Recheck LA connection with Ground)
(4) Due to heavy Lighting Strock.
(5) Fault in HT/LT Cable.
(6) Selection of wrong size of LA.
i have expeirence that the primary line 13.2kv after energizing in 8hrs more or less the Lightning Arrester blown or fuse Line1& Line2, what findings could you advise? & solution
this problem.
Thank you
Halo Jignesh,
as part of my job, i would like to verify space adequacy of HVDC substation. can you please clarify below points. Thanks,
(1) what is the clearance to be followed for 400 kV HVDC substation?
(2) for indoor substation, is it sufficient to consider phase-ground, phase-phase and section clearances (i.e. ground clerances not considered) only? will it be enough to maintain adequate creepage distance between phase and ground & phase-phase if the live conductors are beyond the reach of working personnel?
(3) Is there any specific earthing design to be followed for HVDC substation?
Dear Jignesh
Thank you very much for such a nice updated details provided by you on this blog.
Er Vijay Kumar Harsh
Project Manager ,Yemen
Dear sir
In which IS standard will i find these details it is very urgent
regards
murthy
Dear Jignesh,
Please share your Email ID and contact nos..
Regards RAJEEV JAKHAR (09810386806)
sir,
can u please explain about that lightning impulse 550 & 650 since for the 1st one 132kv sectional clearance is 2.7 & for the second one 3.7 please explain
Hi Sir,
Am a Diploma EEE Student.i want to kow what is the ground,sectional,clearances.?
hello jignesh,
could you please tell what is ground clearance & safety clearance?
could you please mention standard for these clearance?
Most of CBIP
Hi Jignesh
There is a horizontal clearance between phases and fences. I’m referring to those fences protecting the substation. However, is there a clearence norm when wires are coming out of the substation? (Basically when the wires are connected to some tower or to some another equipment, in which moment there is only a vertical distance between wires and fences)
Is there any documentation about this specific topic?
Thank you in advance!
all these clearances based on which iec… pls tell me
Good job.
i love it
i live where we use 330kv. what is the clearances for the substation? do i assume the values for 400kv?
Hi….
I am shivkanth Vijayan from Bhoruka Power, Bangalore. I would like to know the IE standard for 66KV bus height in substation which is 4.6mtrs vertical????
can i have minimum clearances required for 66KV equipments in switchyard? CB to Bus Isolator, CB to CT, CT to Line Iso, Line Iso to Cable sealing end to LA, PT?
Dear Jignesh Sir,
Myself srikanta Ghosh B.tech Electrical engineer from west bengal. Recently working in a MNC company and posted in bangladesh. I work as site engineer in 132/33KV S/S. I want to be your assistant in any of your project or want a training from you. Is it possible sir ?
Dear Jignesh,
my self is Kuldeep Singh advocate by profession and Manager in Land acquisition & Liaison department in a company who going to enter in new business related to solar or wind energy parks in various states, i just check some of courses which help me to understand batter in electrical line, can you assist me to find any course .
regards.
Kuldeep Singh
Dear Jignesh.Parmar
Can u determine causes of bursting a Lightning Arrestor in 33kV end of a Transformer, used in dusty area.?
what’s the clearance would be phase to ground for 240 kv 1050 kv BIL. At the disconnect switch (240 kv 1050 kv BIL) point there is expansion type connector with corona ring. Now to calculate phase to ground clearance from edge of ring to ground point of ds whats distance need to consider. There is two types of distance given 1. rod to structure (2100mm) and 2. conductor to structure which is 1900mm. In this situation I believe we should consider 1900mm. Any comments is appreciated.
sir, Can I know what is the minimum ground clearance for a 230kv twin zebra conductor in a 230/110 kv air insulated Sub station.
sir,I want to know safety clearance for 36KV alive part and switch gear panel.
Sir,
I want to know the Bus arrangement reliable and costlier for a indoor substation of 33KV.
I am Looking for a career in uae. can you tell me about some standards of uae
dear sir,
how to calculate minimum clearance , is there any formula?
what is it that you call “bay” in here?
What is the difference between safety clearance and ground clearance in an EHV substation???
I have been trying to understand the same from long time.
e.g. for 132kV S/s at 550kVp safety clearance is 3.7 m and ground clearance is 4.6 m.
Please help
Regards
Palak
Dear sir,
I may known the phase to phase distance of line’s and substation’s Disconnecting switch(12kv DS, 33kV and 66kVDSE)
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How about clearance between CT and PT for 230KV outdoor substation?
Hi ,
Sir
In switchyard we are using hand gloves to open or close isolator and give a earth switch in 66 KV,132 kv and 220 kv but the rating of gloves is maximum 40 kv then why we using that gloves .
Please guide me about that .
Do you know what should be minimum clearance distance between a tree and a 500 kV DC transmission line.
How can we use air gap between a tree and a 500 kV dc transmission line in electrical modelling?
which unit of measurement is used in those tables above its only numbers mm,cm ,m ?
can you please tell me what is the minimum distance of fence from a six pole structure?
Regards,
shiwani
sir please tell Bay to Bay clearance(distance) of 33/11 kv outdoor substation .and clearance of 1 equipment to another equipment.in 33/11 kv outdoor substation.
Sir, Please tell any national or international reference is used for distance between equipments in substation layout
please help what is the minimum safe distance from blasting zone to High tension line
sir ,please tell me i cant identify the line break down from SS to windmill for 33kv ,two feeder A and B both connected in a single pole upto a distance 3km in a DP switch from there to a distance of 2.5 km into the site . A split one direction and B to another ,A has 2 DB switch and B has 3 DB switch . Nearly 2 weeks gone i could not found any clear into the site.
Sir,
Can you please guide us LA calculation for a building above 30 mtr. height,as per IS 2309.
We have calculated LA calculation below 30 mtr. height building .
If possible please share your ider.
Waiting for acknowledgement…
sir,
please give the idea of ground clearance of 765 & 1200 KV substation and transmission Line
please share is code which used for electrical substation installation
Sir
it is very useful thanks
Good explanation