Three Core Extra High Voltage Cable – A Global Innovation

Residential Consumers

Industrial ConsumersGeneration 220/66 KV

Substation

TPDDL 66/11 KV

Substation11/0.433 KV Distribution Transformer

TPDDL 66000 V Underground network 273 Circuit KM,

3600 MVA, ~ 0.5 Million Consumers

Background

1st 2nd 3rd

Only Single Core cable is being used at 66000 V Level.

Single Core Cables have some inherent issues.

Underground 66000 V , 1C, Cable Voltage Induction in sheath (V)

Conductor Metallic SheathInsulation

V

LengthMeter

Volts

L

3

Outer jacket

Problems Associated with Single Core Cable

Underground

SVLSVL

Other Utilities

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Cable gets Heated

Cable gets de-rated

Cable Life Reduces

Cable gets Damaged

• Complete length of the cable becomes faulty.• The complete Cable needs to be replaced by a new

cable.

Problems Associated with Single Core Cable

Impact of Tripping of a 66000 V Circuit

6 Million INR per day – Revenue loss

Whole circuit gets damaged .

Approximately 20 crore INR loss

Approximately 1 Lakh Consumers get affected per

circuit.

66000 V Substation 1

66000 V Substation 2

Bonding Arrangement

Bonding Arrangement

Problems Associated with Single Core CableIn Loop In Loop Out

New 66000 V Substation 3

66000 V Substation 1

66000 V Substation 2

Bonding arrangement to be changed.

It’s a very costly and time consuming job

Problems Associated with Single Core CableIn Loop In Loop Out

What is the solution??

FUNDAMENTAL CHANGE IN THE DESIGN OF THE 66000 V CABLE

Development of 3 Core 66000 V Cable

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Due to its inherent design the 3 core cable has almost nil Sheath Voltage

ConductorInsulator

Metallic Sheath

Outer Sheath

Armour

Inner Sheath

Vector Sum is Zero

Can We move from 3 Core 33000 V to 3 Core 66000 V Cable?

3 Core Cable can be one of the Solution.No Standard

available for 3 Core 66000 V

cable Worldwide

Can We Manufacture 3 Core 66000 V Cable?

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• We Studied Indian Standards for manufacturing cables BIS 7098 part II & part III.

• We also studied Global Standards for Cables, IEC 60840, 60228, 60502.

• American Standard ASTM D2633. • European Standards.

• None of these standards cover 3 Core 66 KV Cable.

No Standard available for 3 Core 66000 V

cable Worldwide

We Decided to make our Own Specification

with stringent testing norms

Issues Faced in Framing the Specifications

The First issue was Sizing of the Cable.

We started by creating conceptual design for 3 Core 1000 Sqmm cable.

But it became very bulky with 29 kg of weight for 1 Mtr. Which can’t be handled by standard machines.

The diameter of the cable was also 170 mm, which is an exceptionally high value and would prove difficult to handle.

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Can we go for Higher

Conductivity Material?

Can we go for higher conductivity material

We also explored possibility of using Copper conductor in place of Aluminum. Weight still was out of limit.

We reached a dead end.

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What Next?Can we go for 2 runs of 3 core

cable in place of 1 run?

Sizing of the cable- Development of 3 Core 66000 V Cable

1. Sizing

2. Three nos. of Single Core Cables are equivalent Two nos. Three Core Cables

Diameter of the new 3 Core 66000 V Cable is 128 mm & Weight is 14 kg /Meter

PARAMETERS 66KV 1 x 1000 sq.mm 66KV 3 x 300 sq.mmCurrent capacity (in

Ground) 600 A 303 A x 2 = 606 A

Diameter & weight of the new 3 Core 66 KV Cable is within standard limits

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Associated Accessories

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These Accessories are not available

Straight Through Joint Kit Termination Kit

TPDDL along with associates developed these accessories with lot of efforts within 3-4 months.

With this concept draft specifications were

finalized for 66000 V 3C X 300 Sqmm cable

Manufactures’ Reluctance

Specifications were shared with the manufacturers & only one associate turned up.

The Reasons were:

1) Huge risk involved as the cost of 1 Mtr 66000 V Circuit is approx. 15000 INR.

2) Resistance to Change

But When we floated the tender all associates participated and finally the order was awarded to one of the associate.

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Final Cable

Aerial & front view of the Cable

CPRI Tested & Approved

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Experience so far…

5 Km Cable has been laid as a pilot project & working satisfactorily

since last seven months

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Impact of the Development

There is no Voltage on Outer Sheath of 3 Core Cables. so bonding arrangement is not required. And there is no issue of total length of cable getting damaged . This results in annual cost saving of 20 crores INR annually

Cost is less by 5%. This results in annual cost saving of 1.2 crores INR annually

Width of the Trench is less by 15 %. This results in reduction of road restoration charges by 1.12 crores INR annually

Flexibility of system shall increase as Loop in loop out shall become easy by 2.64 crores annually

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Resulting in total Saving of Approx. 25 Crores INR

Annually

Impact of the Development

Double run for single circuit – results in reliability & customer satisfaction without paying any thing extra. Directly linked to brand image of the organization

Only 2 drums required at site instead of three drums as required in single core cable

Laying is very easy & simple, TODAY. As single core cables are laid in trefoil formation with clamps

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Recognition by Industry

Matter was taken up by TPDDL with Bureau of Indian Standards for framing of specifications

CIGRE(The Council on Large Electric System) – IEC has invited TPDDL to discuss the framing of standards for 3 Core EHV Cables in Colloquium 2016 , Montreal, Canada

Central Power Research Institute is updating its testing facility to cater to 3 Core EHV Cables.

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BIS 7098 Part II & Part III are taken up for revision by Bureau of Indian Standard for Three core Extra High Voltage cables

TPDDL’s letter to BIS to take up for spec revision

Excerpts from the MOM of Meeting held with Beureau of Indian Standards

Invitation from CIGRE

Uniqueness & Scalability

Uniqueness : First time implementation across industries, globally.

Scalability : Huge potential for whole distribution and sub-transmission sector world wide. The consumption of 66000 Voltage & above Cable in SAARC nations itself is of 6700 KM, costing 2000 Crore INR.Boon for Smart Cities.

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Thank You