In the 1960s, the Spanish Regulations for Health and Safety at Work prohibited live-line work on electric installations unless the supply was disconnected and earthed. However, the Spanish Association for Medicine and Safety of the Electrical Industry (AMYS) contributed in an important way to the modification of the Health and Safety at Work regulations. As a result, live-line work is now acceptable in Spain under the following conditions:

  • Specific work methods are used

  • Safety-approved materials and tools are used

  • Utility technicians are authorised to undertake the procedure

  • Work site is under constant surveillance by technical staff, who are authorised to ensure compliance with safety standards and the appropriate working instructions.

The development of regulations for live-line working techniques led to the creation of the Live-Working Spanish Committee, which comprises a large cross section of electricity utilities and contract companies authorised to undertake live-line working in Spain. The minimum provisions for the safety and health protection of workers against electric hazards defined in Spanish regulations are based on CENELEC UNE-EN 50110 standard. This European norm was the first step toward standardizing the safety levels when carrying out works in electric installations. In practice, the conditions and requirements established in utilities with respect to live-line work are normally much stricter than those specified in official standards.

At present, the practice of live working is increasing significantly because the utilities obtain a three-fold benefit by using these live-line techniques: economic, social and environmental.


Circuit availability has a positive impact on a utility's balance sheet, because the availability index is an integral part of the remuneration formula applicable to transmission companies. In the event a network's availability is above the fixed value, the utility receives a bonus over and above the standard remuneration. Live-line working is one of the maintenance activities where innovation and improvements are continually developed. This often leads to the creation of applied research projects, and the cost of this research and development can attract tax relief, depending on the prevailing national policies.

Areas of current Spanish research in transmission and distribution include:

  • The use of robotised means to replace insulator chains/strings, hardware and accessories, disconnect switches on distribution lines, substation switchgear and electric field measurement of composite insulators

  • The use of airborne means to repair conductors, replace line components and clean the insulation

  • New methods and materials to clean the insulation on substation switchgear and composite insulators.

Business opportunities arise as developed technology is sold to other companies, creating an interesting mix of income sources that can increase the utility's intangible value based on its technological reputation.

The availability of all system circuits for the large power transfers from the point of generation to the consumer can significantly reduce the power losses, minimising system operating costs. Additionally, a circuit remaining in operation while being repaired using live-line techniques allows the system to operate as planned.


A key external social benefit of using live-line working techniques for routine maintenance and construction work is that energy is supplied without interruption. This effectively increases system availability, reducing planned outages and thereby satisfying society's demand for improved service quality.

On the Spanish transmission system and distribution network, more than 1.5 million man-hours are used annually on live-line working procedures. This reduces circuit disconnections by some 300,000 circuit-hours, increasing the transmission system circuit availability above 98.5%. On the distribution network, the times of equivalent interruption of the power installed (TIEPI) have been reduced from 2.86 hours in 2003 to 1.82 hours in 2005.

Another external social benefit affects the use of helicopters for public services. Transmission circuits are often routed over roads and reservoirs, the same locations commonly used by helicopters for public service responsibilities. The transmission lines are highly visible and serve as beacons in adequate numbers, size and colour, which are installed using live-line working procedures.

Intensive staff training has a more internal social benefit as it directly impacts employees' personal development and helps to maintain their self-esteem and pride. The theoretical and practical training, together with the written procedures, enable high safety levels. The increased safety at work is one of the most important contributions of live-line working. The accident ratios in Spain for live-line working on all voltage levels are less than 30% than those of disconnected installations. And for the past 20 years, live-line working on the transmission system has been accident free.


The reduction of losses by an increased availability leads to savings in generation and lower emissions of polluting gases in the atmosphere. Also, live-line working procedures and methods are specially designed to address environmental issues, such as the installation of bird flight diverters and the replacement of insulators, spacers and other accessories that generate noise.


The need to work on energised circuits arose from satisfying the increasing need to keep circuits connected even when repairs or circuit modifications were necessary, a practice that also offered the opportunity to improve network availability substantially. As it is increasingly difficult to obtain consents for the construction of new lines, the value and interest in live-line working practices increase.

In Spain, the first live-line work was carried out by Cobra Electricidad on May 16, 1968, in Dos Hermanas, Sevilla, on a 15-kV line owned by the Compañía Sevillana de Electricidad. The team consisted of a foreman and six workers changing a wooden alignment support on the line. The introduction of live-line working procedures was a busy period, with the need to examine the techniques already in use by other countries, train the first technicians and work crews, design specialised tools and establish the first guidelines for the techniques in Spain.

Live-line working practices gradually became relatively common throughout the entire electric sector, but in the early 1990s, there was a slight regression in the use of these procedures on medium- and low-voltage networks. This period proved to be short lived, as it was followed by a strong push at the national level to develop these techniques and expand their application to a wider range of work types.

During this period, Spanish utilities developed their own technologies in the field of live-line working. In some cases, the solution to specific problems became accepted international practice. For example, the practice of using helicopters to clean insulators with pressure-water jets. More recently, an important growth in the number of contract companies in the field of live-line working has led to electricity utilities outsourcing this activity.


Spanish utilities have made significant improvements in the live-line working procedures for distribution networks. Among their most-outstanding developments are those linked to the use of robotics, putting Spain at the forefront of this technological field.

Spanish utility Iberdrola, the Engineering Department of Systems and Automation (DISAM) of the Polytechnic University of Madrid and Cobra started in 1990 to develop a tele-operated system for the maintenance of distribution lines under live conditions, carried out within the electrotechnical research and development program (PIE).

The laboratory prototype proved the project's technical feasibility and made it possible to identify its critical points. In 1994, the industrial prototype (Robtet) was developed to carry out the maintenance works on live lines up to 46 kV. By the end of 1997, the first field tests were carried out on live lines, and during 1999, work was done to improve Robtet's performance levels. Mainly the focus was on a new design for communication and information systems.

The key advantages offered by the use of the Robtet system for live-line working electric line maintenance are as follows:

  • Substantially improves operator comfort and safety when carrying out the work

  • Reduces physically demanding work for crew members, limiting the risk of electric contact and falls

  • Enables work under relatively bad climate conditions

  • Positively influences the standardisation of electricity network construction

  • Reduces training period of operators for these works

  • Offers technological advances in live-line working electric line maintenance that will promote future development.


As Spain's transmission system operator and transmission grid manager, Red Eléctrica de España (REE; Madrid) has a transmission system comprising 400-kV lines some 17,600 km (10,936 miles) in length and 220-kV lines some 16,600 km (10,314 miles) in length. REE uses live-line working procedures as the preferred method to undertake a variety of maintenance tasks to achieve an acceptable level of system availability.

REE now employs all the available techniques and live-working procedures, selecting the most-convenient method for each situation. Therefore, in order to replace insulator strings, for example, it uses the bare-hand method.

Within the philosophy of selecting the most-convenient technique, REE makes extensive use of helicopters to support the live-line teams, and the transmission utility has developed its own procedures using the fitted platform technique and the hanging cradle. In addition to developing techniques and technology, REE has shared them with other European utilities.

REE has a large number of transmission lines in the coastal region, and these circuits require regular cleaning to remove salt deposits. To clean the insulators using a high-pressure water jet, REE has developed a washing system from a cradle hanging from a helicopter.

The use of the hanging cradle is particularly suitable for use on the internal phases of lines in horizontal configuration, which in Europe are practically impossible to access via a platform because of the conductor clearances and voltages. To clean the insulators of the external phases, REE uses the faster method of a jet pipeline directly from the helicopter. The combination of both methods optimizes the cost and duration of the insulator cleaning process.

REE also has developed a large range of maintenance activities that can be accomplished using bare-hand methods with the trained and authorised operatives being suspended from the helicopter. This method is used for changing spacers, repairing conductors and ground wires, and fitting beacons and bird flight diverters. Airborne methods are also used for measuring the distribution of the electric field in the insulator chain and installing conductor vibration recorders.


REE continues to demonstrate the benefits of live-line working procedures for routine maintenance and fault-repair activities on the Spanish transmission system. The extensive use of helicopters has led to the development of innovative high-performance techniques. By sharing these developments with other European transmission system operators, it is apparent that the transmission system and distribution network operators in Spain are among the world leaders in the development and application of live-line working practices.

Dr. Martín Portillo Belinchón ( had a 23-year career with Red Eléctrica de España, and he has more than 35 years of experience in R&D, design, construction, maintenance and management of transmission networks. Currently, he is general manager of MP Consulting and a member of the Live-Working Spanish Committee and International Live-Working Association (LWA). He is also a distinguished member of CIGRÉ. In addition to numerous international conference presentations and articles, Portillo has chaired the LWA and Live-Working Spanish Committee, has been a member of the Jicable Technical Committee, and has served on working groups for CIGRÉ, the International Electrotechnical Commission and CENELEC.

Miguel Ángel Fernández (, head of the Live-Line Working Division of Cobra Electricidad has been manager for various international projects. With a long career in live-line work, he is chairman of the Cobra Group Live-Line Committee and a member of the Live-Working Spanish Committee, Spanish Standardisation Committee, IEC and CENELEC. Fernández has authored papers on live-line working for national and international seminars and conferences.

Ángel Pérez Herranz ( is the health and safety manager of the Spanish Electricity Industry Association and a member of the International Live-Working Association (LWA). As secretary of the Live-Working Spanish Committee, the Standardisation Spanish Technical Committee on Electrical Safety and the working group for electrical risk prevention, Pérez has authored articles on live-line working and his experience in this field has resulted in participation in more than 200 seminars, conferences and congresses.