Practical HV Cable Jointing & Terminations for Engineers and Technicians

THE WORKSHOP

The range of voltage and capacity of power transmitted through cables is showing a steady increase over the years. Environmental concerns, aesthetic issues, lack of transmission corridors and difficulty in routing overhead lines in crowded human habitats are some of the reasons for the explosive growth of cable technology well into the extra high voltage range. Due to physical limits on cable lengths for manufacturing and packaging, joints in cable become inevitable, particularly in the context of the utility sector. The cables need to be also terminated at sending and receiving end equipment, a very wide variety of them, in utility as well as industry applications and this calls for appropriate cable termination accessories.

Cable terminations and joints form the weakest link in any distribution system. Also, a failed joint in an underground distribution system is much more difficult to locate and repair compared to any similar problem in overhead distribution systems. This means that we should do our upmost to achieve a good joint or termination, which can give years of trouble-free service. The quality of a joint or termination depends to a large extent on the skill of cable jointer. The aim of a cable jointer must therefore be to obtain a joint whose electrical properties are as good as the original cable both in electrical and mechanical terms. The design of cable jointing and termination accessories is based on this perception. Dependence on operator-skill is sought to be reduced to the extent possible by good choice and quality of jointing materials, though such dependence cannot be totally eliminated.

We will discuss these issues in this course by looking at the fundamental theoretical aspects involved so that the importance of the correct execution of a termination or joint will be brought home to those who attend the workshop.

WHAT IS INCLUDED?

  • Receive a certificate of attendance in support of your continuing professional commitment
  • All workshops include the associated hardcopy technical manual
  • Printed workshop handouts
  • Lunch and refreshments
  • Interact and network with workshop attendees and experienced instructors
  • Practical, industry driven content to assist you in your continuing professional development (CPD)
  • Attendees automatically become IDC subscribers and receive exclusive deals and technical content every month

WHO SHOULD ATTEND?

  • Building service designers
  • Consulting engineers
  • Control engineers
  • Data systems planners and managers
  • Electrical engineers and technicians
  • Instrumentation engineers and technicians
  • Maintenance engineersPower system protection engineers
  • Project engineers

CONTENT SUMMARY

COURSE OVERVIEW

  • Need for cable joints and terminations
  • Cables - historic perspective
  • Types of cables
  • Types of insulation materials
  • Basic types of terminations and joints
  • Installation aspects; reducing the number of joints by proper planning
  • Standards and testing
  • Failures

CABLES

  • Basic construction
  • Conductor materials and configurations
  • Insulation materials for different applications and voltages
    • PVC
    • Paper
    • XLPE
  • Use of screen in HV cables
  • Use of armour for ground continuity and mechanical protection
  • Special aspects of single core cables
  • Voltage rating of cables and impact of system grounding method on voltage rating
  • Stress distribution in single core and multi core power cables
  • Electrical breakdown of insulating materials
  • HV cables using XLPE insulation
  • Treeing in XLPE and need for end sealing of cables in storage
  • Basic manufacturing process

CABLE CONNECTORS

  • Materials
  • Types of connectors for cable terminations and joints
  • Current path
  • Method of connections
  • Soldering
  • Brazing
  • Welding
  • Crimping (compression)
  • Bolting
  • Comparison
  • Contact resistance
  • Preferred methods in practice for different cable ratings
  • Contact of dissimilar materials and galvanic effects; use of bi-metal accessories

JOINTS AND TERMINATIONS-THEORY

  • Basic approaches
  • Broad classification of joints/termination approach
  • Prefabricated
  • Site fabricated from kits
  • Comparative merits
  • Prefabricated
  • Pre-moulded (slip-on)
  • Cold shrink
  • Site fabricated
  • Taped and compound sealed
  • Taped and cast resin sealed
  • Heat shrinkable
  • Additional requirements of outdoor terminations
  • Reconstitution of cable properties
  • Insulating tape
  • Semi conducting tape
  • High permittivity stress control tape
  • Sealing against moisture
  • Connectivity for cable screen and armour
  • Mechanical protection of joints and terminations

STRESS CONTROL

  • Effect of joints and terminations on stress gradients
  • Areas requiring stress control
  • Terminations
  • Joints
  • Basics of stress control approach
  • Geometric solutions; use of stress control tubes, cones         
  • High permittivity solutions; use of stress control tapes

JOINTING AND TERMINATION PRACTICE

  • Kits for joints and terminations
  • Shelf life issues
  • Importance of matching diameter of insulated conductor with kit specifications in pre-fabricated kits
  • Preparation of cable for termination and jointing
  • Connection
  • Reconstitution of cable properties
  • Continuity and grounding aspects
  • Sealing
  • Healthiness of joint/termination
  • Installation aspects for joints
  • Buried joints and markers for identification
  • Joints placed on cable structures with other cables-safety issues
  • Access for repairs

STANDARDS AND TESTING

  • International/national standards
  • Type tests
  • Limitations
  • Routine tests
  • Training and certification of personnel

TERMINATIONS TO EQUIPMENT

  • Terminations to indoor switchgear
  • Need for coordination with manufacturer of switchgear
  • Issues arising from multiple terminations - design of switchgear terminals
  • Terminations to electrical machines
  • Termination of outdoor HV installations
  • Terminations to GIS installations
  • Importance of correct orientation of terminations

FAILURES AND ANALYSIS

  • Reasons for failures
  • Documentation of work
  • Documentation of failures
  • Analysis of failures
  • Predictive approach
  • Use of partial discharge detection

NEW TRENDS

  • Reasons for increasing preference to underground cables
  • New technologies for very high capacities and voltages
  • EHV XLPE
  • High temperature superconductivity in cables and likely impact on current practices

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