Bare Overhead Transmission Conductors “Selection and Application”

Smart Grid Workshop For

Utilities and Regulators of Eastern Region

Pradeep AgnihotriDy.Manager (Tech & QA)Apar Industries limited.

Objectives

• Become familiar with the available conductor constructions.

• Understand the differences between them.• Understand their application• High Performance Conductors (HPC)

Conductor Properties• Current Carrying Capacity• Strength• Weight• Diameter• Corrosion Resistance• Creep Rate• Thermal Coefficient of Expansion• Fatigue Strength• Operating Temperature• Short Circuit Current/Temperature• Thermal Stability• Cost

Categories of Overhead Conductors• Homogeneous Conductors

CopperAACAAACAL-57, AL-59 (HPC)

• Non - homogeneous ConductorACARACSRAACSRACSS, ACSS/TW (HPC)TACSR (HPC)STACIR (HPC)GTACSR, GZTACSR (HPC)ACCC (HPC)

Why so many Choices?

• Power Delivery RequirementsCurrent Carrying CapacityElectrical Losses

• Line Design RequirementsDistances to be SpannedSag and Clearance Requirements

• Environmental ConsiderationsIce and Wind LoadingAmbient Temperatures

AAC - (All Aluminum Conductor)

FeaturesGood Conductivity - 61.2% IACSGood Corrosion ResistanceHigh Conductivity to Weight RatioModerate Strength

Typical ApplicationShort spans where maximum current transfer is required.

Metal: 1350-H19 Aluminum (160

MPa)

AAAC - (All Aluminum Alloy Conductor)

FeaturesHigher Tensile StrengthExcellent Corrosion ResistanceGood Strength to Weight RatioModerate Electrical LossesModerate Conductivity – 52.5% IACS

Typical ApplicationTransmission and Distribution applications incorrosive environments, ACSR replacement.

Metal: 6201-T81 Aluminum Alloy

(300 MPa)

AL59 (AAAC) - (High Conductivity All Aluminum Alloy Conductor)

FeaturesModerate Tensile StrengthExcellent Corrosion ResistanceModerate Strength to Weight RatioLower Electrical LossesModerate Conductivity – 59% IACS

Typical ApplicationTransmission and Distribution applications incorrosive environments, ACSR replacement.

Metal: Sp. Aluminum Alloy

(240 MPa)

ACAR - (Aluminum Conductor Al. Alloy Reinforced)

FeaturesBalance of Mechanical & Electrical Excellent Corrosion ResistanceVariable Strength to Weight RatioHigher Conductivity than AAACCustom Designed, diameter equivalent to ACSR most common

Typical ApplicationUsed for both transmission and distribution circuits.

Metal: 1350-H19 Aluminum (160

MPa) & 6201-T81 Aluminum Alloy

(300 MPa)

ACSR - (Aluminum Conductor Steel Reinforced)

FeaturesGood Ampacity Good Thermal CharacteristicsHigh Strength to Weight RatioLow sagHigh Tensile Strength

Typical ApplicationUsed for both transmission and distribution circuits.

Metal: 1350-H19 Aluminum (160 MPa) & Coated

Steel Core (1350 -1500 MPa)

AACSR - (Aluminum Alloy Conductor Steel Reinforced)

FeaturesExtra High Tensile Strength Good Thermal CharacteristicsHigh Strength to Weight RatioLow sagLower Conductivity

Typical ApplicationLong span and severe loading applications for both transmission and distribution circuits.

Metal: 6201-T81 Aluminum Alloy

(300 MPa) & Coated Steel Core (1350 -1500 MPa)

Categories of Overhead Conductors• Homogeneous Conductors

CopperAACAAACAL-57, AL-59 (HPC)

• Non - homogeneous ConductorACARACSRAACSRACSS, ACSS/TW (HPC)TACSR (HPC)STACIR (HPC)GTACSR, GZTACSR (HPC)ACCC (HPC)

RECONDUCTORING• Enhanced Current Carrying Capacity for the same diameter/weight.• No modification/reinforcement to the existing towers.

NEW LINES• Enhanced Current Carrying Capacity.• Reduction in per unit transmission cost.• Higher Corrosion Resistance.• Shorter Project Duration.• Additional capacity is reserved for future demand

GREEN SOLUTIONS• Low loss leading to lower carbon emissions.• Run at lower temperature for the same current.

TACSR

ACSS

STACIRGAP

AL59

CCC

Application of HPC

Green solution

Re-ConductoringNew Line

Thermal Alloy Conductor Steel Reinforced

TACSR

Green solution

ReconductoringNew LineTACSR

TACSR conductors are the conductors wherein the

inner core is composed of galvanised steel and

outer layers are composed of thermal-resistant

aluminium alloy.

PRO’s:

•50% more – Power Transfer Capacity.

CON’s:

• Higher sag than ACSR.

Thermal Aluminium Alloy Wire

Wire-Galvanised Steel

Super Thermal Aluminium Conductor Invar Reinforced (STACIR)

Green solution

ReconductoringNew Line

TACSRSTACIR

This low sag conductor is manufactured from Al-

Zr(Aluminium Zirconium) alloy rods. The

conductor comprises of an strong inner Invar

steel core and concentrically arranged STAL

strands forming the outer layer of conductors.

PRO’s•No modification/reinforcement is required to the existing towers.• 100% more – Power Transfer CapacityCON’s:•High losses

Super-thermal resistant Al

alloy wire(STAL)

Aluminium Clad INVAR Core

GAP-Type Conductor

Green solution

ReconductoringNew LineTACSR

STACIR

GAP conductors are manufactured from

(super) thermal-resistant Aluminium Alloy

wire and the high strength steel core.

There is a small annular gap filled with

grease between the high-strength steel

core and the first layer of trapezoidal-

shaped aluminum strands.

PRO’s:

•Low Sag

CON’s:

• High losses

High Strength Steel Wire

(Super) Thermal resistant

aluminium alloy wire

Gap filled with grease

GAP

Aluminium Conductor Steel Supported (ACSS)

Green solution

ReconductoringNew LineTACSR

ACSS

STACIR

ACSS conductors are manufactured from

Annealed Aluminium 1350 wires and an

inner high tensile strength core of Galfan

(Zn 5% Al Mischmetal) coated steel wires.

PRO’s:•Capable of operating at upto 2500 C.• Low Loss due to Annealing of AluminumCON’s:• SAG exceeds the conventional Conductor Sag at the maximum Operating temperature of the conductor.

1350 Annealed Al Wire

Mischmetal Steel Wire

GAP

Aluminium Carbon Composite Core (ACCC)

TACSR

ACSS

STACIRGAP

Green solution

ReconductoringNew Line

Composite carbon core for cable

PRO’s:

• 40% reduction of Line loss.

• Low weight and Low SAG.

CON’s:

• Special Installation required.

Carbon Composite Core

Annealed Aluminum Wire

AL59CCC

Actual Case Studies:

New 220 kV Transmission Line

Need: GETCO was in need to increase power transmission by at least 50% to 100%Available Infrastructure : D/C ACSR Zebra

Challenges:• Mechanical Load should not violate existing loads on the 220 kV Towers.• Cost should be 20% - 30% more than existing 220 kV T/L with ACSR Zebra + Fittings.• Fittings ware required to be developed as first time ever this conductor was going to be used in

India.

The Basis of Solution:(a) Conductor capable of carrying 1.5 to 2.0 times the current atleast (900 amp. to 1200 amp.)(b) AL-59 (zebra) equivalent conductor was having 2+ mtr sag & was incorporated by 3 mtr

extension.(c) The installation is as good as that of conventional ACSR or AAAC conductors.

(i) Case Study – Govt. Utility Project

Rajkot City – 66 kV D/C Line Gondal Hadmatala

Need: GETCO was in need to increase power transmission by at least 50%Available Infrastructure : D/C ACSR Dog

Challenges:• Ground Clearance was to be maintained.• Mechanical Load should not violate existing loads on the 66 kV Towers.• Cost should be equal R&M Cost of GETCO with ACSR Dog + Fittings.

The Basis of Solution:(a) Conductor capable of carrying 1.6 times the current atleast (260 amp. Vs 420 amp.)(b) Conductor with Sag should be 1.2 mtrs higher than existing ACSR Dog . (c) The installation will be very safe so as to not affect the hutment settlement.

(ii) Case Study – Govt. Utility Project

CEA References

Usage of HPC has been endorsed by CEA.

Thank You !Thank You !