Estimation of 11 KV Lines Or HT Line Or High Tension Line

July 23, 2020February 21, 2022 CS Electrical And Electronics

Hello everyone, in this article, I will discuss the estimation of 11 KV lines or HT line or high tension line, specifications of materials used in the 11 KV High Tension line, methods of calculating an estimation of materials required.

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Also read – Transmission, Distribution, And Utilization Question And Answers. and now I will discuss the estimation of 11KV lines.

Estimation of 11 KV Lines

1. Poles

Materials used: R.C.C
length of pole 8 meters or 9 meters, working load 140 Kg.
Cement concrete proportion, 1:2:3 or steel with M.S round.

2. Cross Arm

Type: H.T Horizontal cross arm or H.T v-cross arm.
Section: L-section (Angle iron)
Length: 0.9 meter

With HT single top support, pole clamp, bolt, nuts, washers complete set.

3. Guy Set

11 KV class, a stay clamp is fixed at which a turnbuckle with eyebolt is bolted.

15 KV strain insulator, stay wire of 8/11 SWG standard, Anchor plate of MS 300 mm * 300 mm * 3.1 mm, Guy pit is filled with sufficient weight of stones and then fit into the earth, A complete set.

4. Pin Insulator

Class: 11 KV for H.T
Material: Well glazed porcelain
Size: height 125 mm and dia 178 mm

Complete with insulator pin, nut, and washer.

5. Strain insulator

Material: Well glazed porcelain
No: 15
Voltage: 15 KV

6. Conductor

Size: Squirrel, (No.4 A.C.S.R) of 6/1/2.11 mm (6. no of aluminum conductor and one central galvanized steel conductor having a diameter of 2.11 mm each). Weasel, (No. 2 A.C.S.R) of 6/1/2.59 mm. Rabbit ( No. 1 A.C.S.R) of 6/1/3.35 mm. Wren (No. 8 A.C.S.R) of 6/1/3.33 mm. Fox (A.C.S.R) of 6/1/2.79 mm. Drake (A.C.S.R) of 30/7/4.27 mm

7. Gang operating switch (G.O.S)

Operating voltage: 11 KV or 13.2 KV
No of Break: Single or double
Current rating: 200 or 400 Amps

Operating handle with locking arrangement.

8. Spiral earth electrode (SEE)

Material: 8 SWG G.I wire
Size: 150 mm dia, 450 mm long with 115 turns.

Wound spirally from top of the pole to the ground and buried 1.5 m below the ground at bottom of the pole.

9. Anti-climbing devices

AC devices such as barbed wire are to be wound on all H.T poles above the height of 1.5 meters so that ignored persons do not climb the pole and meet with an accident.

10. Danger board or Caution board

Size of plate : 20 * 15 * 1.6 mm thick
Color: Red letters in a white background or white letters on a red background

11. Earth guard stirrup (EGS)

Material: M.S. flat of size: 25 * 6 mm, length 2.74 meters.

Double inverted V-Shaped flat forming a net of 8 SWG G.I wire for conductors. If the line snaps it will hit earth G.I wire and gets earthed.

12. Double pole structure

Type of pole: P.C.C or R.C.C
Height of pole: 8 meters or 9 meter

with cross arms braces, clamps bolt, nuts, with 2 No. of 8 meter RCC pole a complete set.

13. Bird guards

Material: MS sheet of 1.6 mm thick.

Size: Saw-type with a suitable arrangement for fixing in to cross arms, etc.

14. Primary cutout

Type: Drop out lift-off (DOLO)
Material: Porcelain
Voltage rating: 8, 11 and 15 KV class

15. Lightening Arresters

Type: Electrolytic multi-gap, oxide film, Thy-rite, etc
Voltage rating : 6, 11, 13.2 KV etc.
Enclosure material: porcelain with suitable top and bottom terminal for connection.

Methods Of Calculating Materials Required for HT Lines

Materials required are :

1. No of span

= Length of line / span

2. No of supports

= No of span + 1

3. For 11 KV lines, Double pole structure is to be provided for each run of 1 KM with an additional DP structure required for tapping and deviations if any.

Therefore, No of DP structures = No of KM + (Deviation ) 1 + 1 ( for tapping )

4. Number of poles i.e., R.C.C poles of 8 meters long

= total no of supports – number of DP structures.

5. No of HT horizontal cross arms

= No of poles + No of additional deviations

= No of top fittings

6. No of pin insulators

=(No of supports + No of additional deviations) * 3

7. No of strain or Disc insulators

= 3[1 (staring end) + 2(additional anchoring) + 2(intermediate DP) + 1(dead end DP)]

8. No of Guy set required

= (No of intermediate D.P) * 4 + (No of additional anchoring’s) * 2 + No of deviation + (No of guardings) * 2 + No of storm guysets (for each KM two pairs) + 2(dead end DP)

9. Length of A.C.S.R conductor required with 3% sag

= 3*1.03*No of KMS.

10. During stringing of the conductor in order to reduce the sag of the conductor every 6th span pole is anchored is called anchored pole i.e., at a distance of 0.5 KM.

Hence additional anchoring at pole = No of KM, because the anchoring is to be had at each 0.5 KM, and as one anchoring will be done at DP itself, so for each KM there will be only one additional anchoring at the pole.

11. No of anti-climbing devices

= 1 (No of the single pole) + 2 ( No of DPS)

12. No of Danger boards = No of supports

13. No of Earth guard stirrups

= [No of poles – Additional anchoring poles]

14. Provision for guarding, Transportation charges, labor charges, inspection charges are to be provided.

Estimation of materials required for HT line construction

Q: A 11 KV line is to be tapped and extended to a distance of 7 km, rural electrification. Prepare a list of materials required for (a) Tapping (b) Extending an 11 KV line assuming a span of 85 meters.

Solution :

(A). Materials required for tapping

(B). Materials calculation for extension of 11 KV line

Assuming anchoring at 0.5 KM and D.P for each KM run.

1. No of span = 7000/85

= 82.3 or say 82

2. No of supports required

= 82 + 1 = 83 No’s

3. No of D.P structure = 7 No’s

4. No of 8-meter R.C.C poles

= No of supports – (No of DP + one tapping)

= 83 – 8 = 75

5. No of Horizontal cross arms with H.T.S.T.S

= No of poles = 75 (No deviations)

6. No of pin insulators with pin and clamps

= 3 (No of cross arms + No of DPS)

= 3(75 + 7) = 82 No’s

7. No of disc insulators

= 3[1(starting end + 2 * 6(Intermediate DPS) + 2 * 7(additional anchoring) + 1(dead end DP)]

= 3[1 + 2 * 6 + 2 * 7 + 1] = 28 * 3 = 84 No’s

additional anchoring at the pole for 7 KM length of line apart from DP is 7.

8. No of Guy sets

= 4 ( No of intermediate DP) + 2( No of additional anchoring ) + 2 ( dead ends )

= 4 * 6 + 2 * 7 + 2 * 1 = 40 sets.

9. Length of A.C.S.R No 2 with 3% sag

= 7 * 3 * 1.03 = 21.63 KM

10. No of spiral earth electrodes

= No of poles + No of DPS

= 75 + 7 = 82

11. No of danger boards = 82

12. Earth guard stirrups

= No of poles – No of anchoring points

= 75 – 7 = 68

13. No of A.C devices

= No of poles – No of anchoring points

= 75 – 7 = 68

14. Miscellaneous materials such as bolts and nuts, etc.

I hope this article may help you all a lot. Thank you for reading. If you have any doubts related to this article “estimation of 11 KV lines”, then comment below.

Tags: Estimation of 11 KV Lines Or HT Line Or High Tension Line.

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