Clearances (Extract from Manual of Electricity Laws)

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Sl. No.	Subject
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
3.							3050 mm above HFL. Suitable clearance in maximum water level condition, above the tallest mast, in consultation with Navigational authorities 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 questionnaire 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.