A unique facility for evaluation of HTLS conductors

With increased private participation in power generation and distribution in India, alongside that of public sector, there is a robust demand for bare overhead power conductors. The challenges faced by the transmission companies are to accommodate the necessary generated power over their network. This can be accomplished by laying extra lines, which is an expensive proposition or resources can be used for reconducting by high-temperature low sag (HTLS) conductors, which can increase the power transmission capacity. 

Indian transmission companies including utilities are adopting HTLS conductors. However, at present, for independent testing, the manufacturers have to go abroad.

It is, therefore, planned to set up a test laboratory for HTLS conductors at ERDA. Once this facility is created at ERDA, manufacturers and users will be able to carry out complete type and acceptance tests under one roof at ERDA as per the latest international and national standards.  

Specifications for evaluation

Facilities are being installed as per the following mentioned specifications:

• Power Grid specification II
• Draft of IEEE standard P####/D1.0, January 2009.
• CIGRE report No. 426 on guide for qualifying High-temperature conductor for use on overhead transmission lines.

Types of HTLS conductors to be evaluated

• Conductor composed of a steel core and an envelope for which the high temperature effect is controlled by means of thermal resistant aluminium alloy (GAP, TAL[Thermal Alloy Conductor Steel Reinforced]; ZTAL (ultra-thermal resistant)
• Conductor composed of a steel core and enveloped for which the high temperature effects are controlled by means of annealed aluminium or aluminium alloy (e.g., ACSS)
• Conductors composed of non-metallic core, and an envelope for which the high temperature effect are controlled by means ofthermal resistant aluminium alloy (e.g., ACCR)
• Conductor composed of a non-metallic core are controlled by an envelope for which the high temperature effects are controlled by means of annealed aluminium or aluminium alloys (e.g., ACCC)
• Thermal Aluminium Conductor Invar Reinforced (e.g., TACIR)

Tests to be carried out on HTLS conductors:

On complete conductor

• DC resistance test
• UTS test
• Stress-Strain test conductor and core at Room temperature
• Stress-strain test on conductor and core at elevated temperature
• High temperature endurance & creep test
• Conductor thermal expansion test
• Sheave test
• Axial impact test
• Radial crush test
• Torsional ductility test
• Aeolian vibration test
• Temperature cycle test

On conductor strand/core

• Bending test
• Coefficient of linear expansion
• Strand brittle fracture test
• Torsion and elongation tests
• Glass transition temperature test
• Flexural strength test
• Salt spray test