Clearances
(Extract From Manual Of electricity Laws)

1. BUILDING:
(a)

Where a high or extra high voltage over head line passes above or adjacent to any building or part of a building, it shall have on the basis of maximum sag, a vertical clearance above the highest part of the building  immediately under such line, of not less than:

(a)  for high voltage line upto and including.

33 KV

3.685 mtrs. (12 ft.)

(b)  for extra high voltage lines 3.685 mtrs. (12 ft.) plus
0.305 mtrs. (1 ft.) for every additional 33 KV or part there of
(b) The horizontal clearance between the nearest conductor and any part of such building shall on the basis of maximum deflection due to wind pressure, be not less than:
(a)  for high voltage line upto and including 11 KV 1.219 mtrs. (4 ft.)
(b)  for high voltage line above 11 KV and upto and including 33 KV 1.829 mtrs. (6 ft.)
(c)  For extra high voltage line 1.829 mtrs. (6 ft.) plus
0.305 mtrs. (1 ft;) for every additional 33 KV or part thereof.
2. CLEARANCE ABOVE GROUNDS:
(Clause 77 of Indian Electricity Rules)
m.m.

33 KV
66 KV
132 KV
220 KV
400 KV

5100
5490
6100
7015
8840
3. CLEARANCE OVER RIVERS:
(Above maximum flood level)
Rivers not Navigable
Rivers Navigable
 
3050 mm above HFL.
Suitable clearance in maximum water level  condition, above the tallest mast, in consultation with Navigational authotities concerned.
4. CLEARANCE OVER PTCC LINE:
m.m.

66 KV
132 KV
220 KV
400 KV

2440
2745
3050
4880
5. MINIMUM CLEARANCE BETWEEN POWER LINES:
Nominal System Voltage of line to be crossed:
KV 11 33 66 132 220 400
11 2.44 2.44 2.44 3.05 4.58 6.10
33 2.44 2.44 3.05 4.58 6.10
66 2.44 3.05 4.58 6.10
132 3.05 4.58 6.10
220 4.58 6.10
400 6.10

Higher voltage line normally be kept over lower voltage line.

6.

As per ISS 162-1961 minimum electrical clearance from live part to earth and safety clearance in case of different voltage must be kept as follows:

VOLTAGE

ELECTRICAL CLEARANCE (mm) Phase-Earth / Phase-Phase

SAFETY CLEARANCE IN SIS (mm)

KV

33

381 432 2740
66 658 786 3050
132 1127 1473 3810
220 2082 2388 4570
4000 3500 4000 6100
7.

CLEARANCE FROM RAILWAY TRACKS:
(As per Regulation for Electrical Crossing of Railway Tracks 1963)
The relevant provisions for the crossings of Railway Tracks by the power lines are as under: The minimum height above rail level of the lowest portion of any conductor under conditions of maximum sag are as follows in accordance with the Regulations for Electrical Crossings of Railway Tracks, 1963:
(i)  FOR UNELECTRIFIED TRACKS OR TRACKS ELECTRIFIED ON 1500 VOLTS D.C.

Broad Gauge Meter and Narrow Gauge
Inside Outside Inside Outside
station station station station
limits limits limits limits
(mm) (mm) (mm) (mm)
66 KV 10,300 7,900 9,100 6,700
132 KV 10,900 8,500 9,800 7,300
220 KV 11,200 8,800 10,000 7,600
440 KV* 13,600 11,200 12,400 10,000
(ii) TRACKS ELECTRIFIED ON 25 KV A.C.
For Broad, Meter and Narrow Gauges
Inside Outside
station station
limits limits
(mm) (mm)
66 KV 13,000 11,000
132 KV 14,000 12,000
220 KV 15,300 13,300
440 KV* 16,300 14,300
* Tentatively assumed.
 

No conductor of an extra high voltage overhead line crossing a tramway or trolley bus using trolley wires should have a clearance less than 3050 mm above the trolley line.

The provisions of the above Regulations must be kept in mind while carrying out the patrolling of Transmission lines. Any deviation noticed should be reported / attended on top-priority.

8. PROVISIONS OF PTCC:
 

The requisite information's as per the questionaire of PTCC Proforma  have to be taken care of during patrolling / checking of the line. The copy of the above proforma is also enclosed in the manual at Annexure XVIII

An abstract from the "Model Code for Safe Operation and Maintenance of Transmission and  Distribution System" as published by the Ministry of Irrigation and power, Central Electricity Board vide No. PMIP-27/ 200-1979 (DSKII) is also enclosed herewith for general guidance at Annexure XV.

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