In this chapter, the problem of supplying power economically is covered from the various aspects of choosing underground or overhead, the route, the line voltage, wayleave and the various relevant electricity regulations. Although looking initially at new lines, much of this also applies to refurbishment or change of use of lines. By the end of this chapter, the different functions served by undergrounding or overhead construction will be established. Sometimes, ease of establishing an underground network can mean it is just as easy for someone to dig it up. Wayleave and environmental problems are major negatives for overhead lines, but faults are generally easier to find and quicker to repair compared with underground cables. However, this chapter will not soke this perennial argument it is not intended to but it may help an enlightened choice to be made.

This chapter looks at surveying and profiling essential first requirements for any new line construction or for refurbishment. Traditional ground-based techniques are covered first, followed by a description of the increasing trend to use helicopters and laser profiling. The chapter is split into three main areas: 1. traditional surveying /profiling for a proposed new green field route; 2. refurbishing an existing line; and 3. laser profiling using helicopters.

Throughout the twentieth century electricity became arguably the most important commodity provided to the home and industry and now interacts with almost every aspect of our lifestyle. Distribution overhead line designs supplying electricity up to 33 kV, unlike electrical goods, have not necessarily changed all that much, yet there have been significant developments in design criteria that should be noted. Overhead line reliability and safety have been heavily criticised in recent years and so there is a need to address the issues of future overhead line design. This chapter looks at some of the fundamental steps that are adopted in developing a new overhead line wood pole design for the UK environment together with some historical references and the effects of new European legislation.

The next two chapters look at conductors the workhorse of the overhead line. Chapter 8 looks at the electrical choice for conductors and how to calculate what is required. This chapter, however, continues with the mechanical theme of chapter 6. The conductor that goes up must maintain its statutory clearance to ground for the next 40 or 50 years, whether cold or up to its maximum allowable operating temperature (normally 50 °C but now often higher). Mechanical and metallurgical creep cause a conductor to stretch and so slacken off between the poles and this must be allowed for Conductors also take wind and ice loads and. within reason, should not break or be strained beyond their elastic limit under severe weather conditions. There is. therefore, a need to make further allowances e.g. use factors of safety. Finally, not all lines are on level ground. Hills are always present and sag/tension calculations must take account of the fact that an intermediate pole may be on top of a hill or deep in a gully. This chapter therefore seeks to cover the most general aspects of conductor sag and tension calculations, including the weather loads and uneven ground and compares manual methods of line design with computer software design packages.

This chapter looks briefly at the various types of conductor on the market with particular reference to covered and insulated conductors. Aspects such as current carrying capacity, weather loads and line design have been covered in other chapters. A brief introduction to novel conductors that may be used in the future on wood pole lines is given at the end of the chapter.

The Electricity Supply Regulations 1988 (Part V, Paragraph 24) state: 'The supplier shall take all reasonably practicable steps to inspect his installations to ensure compliance with these Regulations'. The electricity utilities (or DNOs as they are now known in the UK) therefore have a responsibility to inspect their networks and, in the context of this book in particular, their overhead lines. This is not only essential to maintain supplies in a costeffective maimer and to be certain that regulatory clearances etc. are complied with, but also to provide a legal defence in any litigation where third parties may try to blame the DNO for incidents involving electricity supply lines. Unfortunately, the regulations give no guidance on methods or frequency of inspections and so it is up to the DNO to decide upon a regime that will deliver the required network performance in terms of supply and safely.

Recent years have seen the derivation and population of health indices to rank assets on the basis of condition (in relation to proximity to end of life) as a means of assisting asset managers in formulating and justifying replacement or refurbishment plans. This chapter looks at the concept of health indices, which are based on utilising existing information, and summarises the experience gained over the past few years with developing and implementing health indices. This enables initial health indices to be derived and populated quickly, without the need for large-scale information collection. This gives a knowledge of present asset condition that can be immediately used to provide a very structured, well defined assessment of future condition assessment activities that can be used to focus and direct future asset management activities.

This chapter looks at the decay processes in wood poles used for electricity distribution networks. It covers the commonly used rot detection techniques as well as the various remedial methods employed. The use of these data to evaluate pole strength and remnant life is then discussed. The need to link wood poles to the load they are required to carry is emphasised and a simple evaluation technique is demonstrated.

This chapter looks at the historical development of working on live lines and illustrates the basics of hot-glove (live line) working on distribution wood pole lines in the UK.

This chapter looks at the future trends in overhead line design, construction and maintenance and also at draft regulations and how these may affect the current situation. The future is something that can be anticipated and precautions taken current data can be extrapolated and the present situation gauged in terms of overhead line supply quality and economic performance. For the future, the challenges of climate change and new regulations and practices require preparations now. The future trend for overhead lines has to be based on two areas what sort of environment the overhead line is likely to face for the next 50 years and how supply quality can be maintained costeffectively.