Sargo Picudo

The Extra High Tension Transmission Line red go Transmission &Distribution Scheme of Five Year Plans, (ii oad (iii) Special Transmission Schemes of Rural Electrification Projects. P

for c ic

rnmen e

System Stability Conditions. The Ce it s

proposals of the A.P. Transco and reco necessary changes if any. The Planning

Scheme guided by the budgetary cons h n

Engineer accords Technical Sanction whi sta o the lines. Normally the Plan lines have en up utio

clearance by the Planning Commission. However, in case of delay in getting such statutory clearance, the lines can still be taken up for execution after obtaining administrative authorization from the A.P. Transco. The proposals for extension of

w

single wire earth return circuits. The L.F. inductions produced in the telecommunication lines may cause fatal accidents to the personnel working on the

rrents exceeding 10% limitation may eech devoid of clarity. Based on the calculated values of induced voltages

g out the protective s stipulated therein.

LINES

s are cove by three cate ) Bulk L

ries (viz.) (i) Schemes and lan lines are those proposed by the A.P. Transco

and Planning Commission of Gove

learance by the

supply to the prospective bulk consumers are cleared by the Electricity Board based on considerations of remuneration. The other category of EHT lines aer linked up ith the Rural Electrification Schemes. These lines are cleared and financed by the ural Electrification Corporation of India under Special Transmission Schemes.

FIXING OF ROUTE ALIGNMENT

Reconnoiter surveys are made by the Transmission Line Construction Engineers and alignment of the power line will be finalized taking into consideration the site conditions. The route is to be got approved from the concerned Chief Engineer in Hqrs office.

ROUTE APPROVAL BY POWER TELECOMMUNICATION COORDINATION COMMITTEE (P.T.C.C.)

It is a statutory obligation of the Electricity Board to obtain approval of the Power Telecommunication Coordination Committee for the route of proposed E.H.T. line before its execution. The formation of this Coordination Committee is a result of recognition by the Government of the fact that a power line under fault conditions can cause L.F. inductions on the telecommunication lines, etc. in the vicinity.

Also, the power lines under normal conditions cause interference currents in the

telecommunication lines. The interference cu make sp

and interference currents, the P.T.C.C. decides the protective measures to be taken on the telecommunication lines and Railway Block Circuit etc. Approval for the route of the proposed power line will be given subject to carryin

measure

to facilitate quick clearance by the P.T.C.C. with lesser quantum of to judiciously choose the line kept in mind that the Low Frequency induction depends on Level at the sending end if the proposed line is a radial one or at both ends ms parallel one (ii) Soil resistances along the route of the proposed munication line from the power line (iv) line with the proposed power line, to the extent possible the power line may be taken away from the existing telecom lines.

articular region exceed 1,00,000 Ohm cms, it may be .H.T. line away from the telecom line by a s. If the region has soil resistances in the range of 5,000 to 20,000 Ohm cms., a separation distance of one to two K.M.s can still be adopted

2.1.3.3 in the route approvals of

C.C.

ines under single line to ground fault exceeds 2000 volts.

are to be provided at the cost of P & T Department.

iv) If the interference current in the single wire earth return circuits is found to be more than 10% such S.W.E.R. circuits are to be converted to metallic return circuits.

2.1.3.4 It may be noted that clearance from Railways is necessary if it is found that their telecom lines and/or block circuits are likely to be affected due to low frequency induction. The Railway Authorities formulate the protective measures required for their telecom/block circuits which shall form part of the list of protective measures to be annexed to P.T.T.C. approval letter.

2.1.4. OM AVIATION AUTHORITIES

2.1.4.1 learance from the Aviation authorities is to be obtained if the towers are proposed f one mile radius from the runway of the and coloured markings to be provided ill be ated by the aviation Authorities for clearing the line.

2.1.3.2 In order

protective measures stipulated, it is necessary alignment. It should be

(i) Fault if the line for

line (iii) The separation distance of telecom The length of parallelism of the telecom If the soil resistances in a p

necessary to take alignment of the E distance of 4 to 5 km

based on other site conditions. Judicious choice of the power line alignment may be made on the aforesaid conditions ensuring that the alignment so chosen shall not be longer than the ‘Bee’ line by 8%. To achieve this limitation, the Construction Engineer is at liberty to resort to Railway crossings and P & T line crossings, keeping in view however, the stipulated angles of crossing, electrical clearances and other design aspects.

Normally, the following protective measures are stipulated the P.T.

i) Re-Engineering of Telecommunication Lines has to be done if the L.F.

induction on the telecom l

ii) If the induction is more than 650 V but less than 2000 Volts, gas discharge tubes will be provided on the telecom lines at the cost of Power Supply undertaking.

iii) For the induced voltages in the range between 430V and 650V, gas discharge tubes

CLEARANCE FR C

to be erected within the Aviation Zone o aerodrome. The limitations of tower height

stipul w

2.1.5 P & T LINE CROSSINGS

.1.5.1 epartment has to give clearance for the crossing arrangement of power line with P & T lines. A detailed sketch showing profile of crossing span, e shall accompany the proposal along with nswered. Clearance for the power lines will be given if he following conditions are fulfilled.

(i) The angle of crossing of the power line with the P & T line is not less than 60^o

For 220 KV Lines : 4.572 Mtr. (15 feet) s : 4.881 Mtr. (16 feet)

2.1.6.1

2.1.6.2

i) The power line shall cross the railway track at an angle not less than 60^o. ll not exceed 80% of the normal design span.

iii) The minimum clearance of the lowest power conductor over the railway track

towers.

vi) The foundations, structures and power conductors and earth-wire are all provided to have a minimum Factor of Safety of 2.00 under normal conditions and 1.50 under Broken Wire Conditions.

vii) The towers shall be earthed by providing two earth pits on either side.

The clearance over the Railway Track and the bottom most conductor for different Transmission lines shall not be less than the distances below under max. sag conditions.

t 2-1.

For 132 KV Lines : 14.60 Metres.

For 220 KV Lines : 15.40 Metres For 400 KV Lines : 17.90 Metres.

2 Posts & Telegraphs D

angle of crossing and electrical clearanc the prescribed questionnaire duly a

t

(ii) The nearest power conductor shall be away from the telecom line by not less than the distances tabulated below under maximum sag conditions.

For 132 KV Lines: 2.744 Mtr. (9feet).

For 400 KV Line 2.1.6 RAIL CROSSINGS

Clearance is to be obtained from the Railway Authorities for the proposed power line crossing railway track. A sketch showing full particulars such as Vertical Clearance of the lowest power conductor over the railway track, angle of crossing and the shortest distance from the railway track from the nearest tower shall accompany the proposal for railway crossing. The prescribed questionnaire duly answered and Factor of Safety Calculations shall also be sent along with the proposals for railway crossing.

Clearance for the railway crossing will be accorded if the following conditions are fulfilled.

ii) The crossing span sha

shall be as per the statement 2-1 on page II-4.

iv) The minimum distance between footing of the nearest tower and the railway track shall not be less than 1.5 times the height of the tower.

v) The Railway crossing span shall be strung with double tension hardware fitted to the towers on either side of crossing span with dead end

Statemen

.2.1 RECONNOITRE SURVEY 2.2.1.1

ay stations/tracks, roads, rivers, etc. all along the probable alignment of the power line. Based on the findings during reconnoiter survey, the route of the proposed power line with Angle Points is marked on the topo sheets giving due consideration to the statutory requirements.