In the last several years, Slovenian power distribution companies have been successfully carrying out preventive maintenance works within the framework of live working (LW) on both low voltage (LV) and medium voltage (MV). The utility company Elektro Gorenjska (EG) supported idea of implementation LW in Slovenia when activities started in 2006. At the end of 2010, the EG management decided to accelerate the process of introducing LW on low voltage (LV) and in 2013 also on medium voltage (MV) – cleaning of MV transformer station. In 2014, the utility company EG started the systematic planning of MV transformer station revisions with the LW method. This paper presents the multi-year experiences with carrying out LW on MV. It shows the effects on the indicators of power supply reliability in the period 2014–2021 and the advantages of carrying out maintenance works with the LW method on MV in the utility company EG and experiences with effects of LW on the improvement of indicators SAIDI (System Average Interruption Duration Index) and SAIFI (System Average Interruption Frequency Index).
Although statistics prove that live working methods are safer than de-energized activities, in some cases accidents may occur due to the neglect of safety rules. Generally, more than one safety factor shall apply individually to guarantee the expected level of safety; however, routine, hurry, or inattention might be very dangerous even during quite simple activities. The rubber glove method is widely used in the whole territory of Hungary and is a common practice in the area of surroundings of Budapest for almost ten years. In the fall of 2018, an unfortunate and serious accident occurred during dismounting a pole-mounted switch. Although the terrain and the geometry were not usual, this looked like a routine job for the practiced crew. While the job was performed, one of the workers suffered a major electric shock. Despite the immediate medical help, permanent damage has occurred. This paper introduces the circumstances of the accident and the measures which were performed by the responsible DSO in cooperation with the training center of BME.
The inspection of power lines using UAVs has become more and more common in the last few years. Albeit it is usually possible to fly the drones at a safe distance from the conductors, some specific measurements may require the UAV to get very close (tens of centimeters) to the power line. In this work, several tests that aim to assess the effects on UAVs of the electromagnetic field produced by high voltage live cables are presented. The issues detected during the experiments are solved using different technical measures that are tested in a real-world environment.
During live working operation, some operation shall be done on insulating strings or insulating columns. This article presents the principles applied by RTE to guarantee the withstand voltage of those insulating strings and columns according to the switching impulse voltage and to the insulators pollution level.
To ensure the availability of electrical power grid, some maintenance and installation works are sometimes carried out in the vicinity of live parts or near high voltage installations. In practice this means that work is carried out on double-and multi-circuit overhead lines and works are carried out on a circuit that is not under voltage (dead), while the other circuit is at the same time under voltage (live). In all such cases of work in the vicinity of live parts the workers must observe the appropriate safety distance, which is prescribed in regards to the voltage level and the third danger zone. Even when taking into account all safety factors, such works can cause increased risks to safety at work, for example risk of electric shock due to induced voltages, voltages of capacitive sets etc. To reduce these risks, special attention should be paid to ensure safety and health at work in the vicinity of live parts with appropriate regulations, reviews of dangerous occurrences, introduction of improvements to working tools and procedures, qualification of workers and consistent use of prescribed personal safety equipment. Based on domestic and worldwide practises, measurements and findings, we conclude that written safety instructions or a manual for safe work in the vicinity of live parts is necessary.
The paper deals with historical aspects of creation the Polish regulations and standards on live maintenance, development of devices and equipment for live working based often on original Polish technology. Some achievements of live working at main distribution companies as well training centers in Poland are also characterized.
The Italian Network Code establishes that all work activities that take place on the electrical systems (electrical stations and lines) of the National Transmission Grid (NTG), must be carried out in compliance with national legislation on occupational safety and electrical risk as well as the CEI EN 50110-1 standards that provide the minimum safety requirements for the operation of electrical systems and for the execution of works on them, in the vicinity of these plants and with the provisions of the Consolidated Law on safety at work referred to in Legislative Decree no. 81/2008, in the CEI 11-27/1 Standards.The Network Code also establishes that each NTG portion holder and network user has the obligation to adopt Terna’s Electrical Risk Prevention Provisions (DPRET) for the management of the decommissioning and safety of the NTG connections and the connection points with it.In this context, recognizing full autonomy to the individual companies in carrying out work activities safely in their plants, according to their provisions for the prevention of electrical risk, the Memorandum of Understanding (PRINT), drawn up in accordance with the DPRET, harmonizes the various existing company provisions and is the right to the above for the aspects regulated by the PRINT.This article illustrates the specific agreements envisaged by the PRINT on Live Work.
This paper presents an arc flash risk assessment procedure using different computer tools from different countries. Different computation methods according new requirements in NFPA 70E (2018), IEEE 1584 and DGUV I 203-077 standard. Four different software are used and compared incident energy (EI) or full energy (WE), arc flash boundary and the level of Personnel Protection Equipment (PPE).Arc flash risk assessment is today a mandatory part of each risk assessment for electrical workplaces and several recommendations exist in different countries like national OSHA rules, PPE Directive in Europe and different standards (EN 50110-1, IEEE 1584, NEPA 70E, DGUV).A short circuit analysis is performed to calculate the values of arching currents and compute arc flash energy dissipated at busbars at HV and LV voltage busbars. Worst case scenario approach is used to examine what is highest level of Arc Thermal Performance Value (ATPV). There are different software tools where used in computation: “EasyPower Arc Flash” (USA), BSD Arc Calculator (Germany), RENblad 1710 (Norway) and ARCPRO™ 3.0 (Canada). These tools are an easy-to-use software package for the calculation of radiated and converted thermal energy from electric arcs. This highly-effective tools offer proven value in helping utilities and other industries select protective clothing (PPE) and meet workplace regulations for safety apparel and comply with OSHA regulations.A practical sample case is presented, and arc flash energy is computed, and PPE recommended for high and low voltage busbars in one stone pit facility in Slovenia. In Slovenia and we started promoting the safety of the electric arc some years ago and we continue with this activity.
Working in the vicinity of live parts is an effective working method on the high voltage power system. However, AC induction poses a threat to the linemen during vicinity working. The aim of this paper is to introduce the induction phenomenon on high voltage equipment, including the different coupling types, and also the magnitude of the evolving induced voltage and current. Moreover, a summary of accidents due to AC induction, their cause and outcome are also presented. One effective protection method against AC induction is the use of personnel protective equipment. For that purpose, some conductive clothing manufacturers developed specially strengthened garments against AC induction. The working philosophy of conductive clothing against AC induction is presented in detail, moreover the developed laboratory testing methodology is also discussed in this paper.
For a big amount of Live Working technologies hot sticks or insulating sticks are an important part of the necessary Live Working equipment. Especially for overhead line work but also for medium voltage indoor applications they will be used in a wide range. Thus a lot of different types of sticks for different purposes exist on the market as well as different technical standards for these equipment by different national and international standardization bodies. Almost all of these sticks must be re-tested periodical by electrical test of the insulation properties. For test laboratories it is often not easy to find the right test procedure for particular insulating sticks. This paper will introduce in the situation of periodical tests of insulating sticks by explaining and comparison of requirements, scopes and test arrangements of different stick standards.
We have been effectively carrying out live work (LW) in the Slovenian electrical energy field for the last ten years. In January 2009 the first permission to an electrical maintenance worker was issued in Krško Nuclear Power Plant (NEK). We implemented a confirmed system for live work based on the French method.Systematic manuals were prepared for the electrical energy (transmission & distribution) and industrial companies. We successfully trained more than one hundred line and maintenance workers and more than one hundred coordinators from the electrical energy, industrial and service fields. Systematic and independent audits of carrying out LW confirm that electricians consistently use the prescribed and required personal protective equipment (PPE) and tools for safe work. We have reached a notable level of efficiency and effectiveness of carrying out LW. Our main concern in Slovenia is safety and health at work. During last ten years there was not any dangerous situations and no accidents while carrying out LW. Now in Slovenia, we carry out LW on low voltage (LV) and we started on medium volt-age (MV) but just cleaning of substation. In Slovenia we still have many challenges ahead of us, mostly to implement the LW method in additional working milieus and use it with the aim to improve electrical energy quality indicators and reduce unnecessary disconnections during preventive planned maintenance works in utilities and process industry. Despite more than 100 years’ experience, our neighbouring countries and other countries worldwide continue with the development of LW methods on all voltage levels, from LV to HV. One of important aim in Slovenia is to carry out LW like a meth-od as a method which supports the “zero accidents” idea. Stakeholders need to promote the safe implementation of LW, so that the safety of LW will be emphasised as much as the economic impacts.
Starting from the late 90s, Terna Rete Italia (TRI) has developed specific projects by awarding “beauty contests” to encourage the design of new trusses for high voltage power lines (380 kV): as the contest “sostegni per l’ambiente” awarded to Norman Foster. Alongside the design and installation of Foster Towers on the single circuit 380 kV “Tavarnuzze – S. Barbara – Casellina” overhead line in 2007, TRI has developed both standard and live-line maintenance techniques. This paper aims to present the main technical features of Foster towers and insulating catenary, describing design criteria for fittings and special tools and procedures to perform standard and live working.
In 2012, the board of the cross-border TSO in the Netherlands and a part of Germany TenneT supplied ‘SHE-Department’ with the task of looking for possibilities to carry out Live working at the high voltage system in the Netherlands. This request was based on the vision that planned outages would be more and more difficult to organize with the increasing inflow of renewables on the grid. After a short assessment, it was obvious that the actual legislation in the Netherlands legally blocked this. This was the starting point of a journey in the Netherlands (that is still going on today). The process of making Live working possible was divided into two workstreams; a short-term focus on carrying out a pilot project including obtaining a temporary dispensation from the labour-law authorities, and a long-term approach to, eventually, change the labor-law
Many overhead transmission lines (OHTL) around the world are very old. Some overhead conductors and ground wires have been in-service since the 1920’s, well past their intended design life, and with deterioration rates largely unknown. As lines continue to age, it becomes increasingly important for utilities to know the existing physical condition of aged conductors and ground wires for safety and reliability reasons but also to optimize the timely expenditures of maintenance and capital budgets. Conductors are of primary interest because their condition often drives asset management decisions.Live-line working is of highest importance for most maintenance operations, and the need to maintain system availability is a significant factor in the introduction of robotics in this field. In order to maintain or increase the reliability of OHTLs, new maintenance techniques are becoming available to assess and diagnose the condition of various OHTL components. Line inspection and maintenance of OHLs already benefit from developments in mobile robotics, which can reduce the potential risk to maintenance crews (e.g. live working), inspection of wire, reach hardly accessible spans (e.g. river crossings), perform tedious work faster, and finally decrease costs. Line inspection robot is a field-based, non-destructive inspection system that “looks through” the aluminium wires and into the steel core wires. Its function is to measure the remaining cross-sectional area of steel wires and to detect any localized breaks or corrosion pits. In many cases. The inspections have to be performed on energized conductors in order to avoid costly power outage. A study into the degradation process of conductors in various environments was undertaken to better understand the various stages of corrosion over time. This information is useful when used with the non-destructive in-situ testing and the asset management model to determine timeframes for projects such as the maintenance or replacement of the conductors.
This paper presents new approaches to the design of live line tools. These designs are based on the use of materials typically used in the production of polymer insulators for use on power line systems. It also includes robotic devices used to make more difficult live line work, easier and safer to complete.
Safety of live workers during live working maintenance is an imperative absolute. The electrotechnics studies, experiments and observations in the last decades are the cornerstone of the implementation of live working under operational conditions. Obviously, this vast knowledge cannot be consulted or analyzed for any live work preparation even though it must be taken in consideration anytime to keep it safe. This is precisely the aim of Special Operating Modes, in a way that will be described in the following sections.
This document describes a procedure for selecting suitable PPE to protect against the thermal effects of an electric arc. The procedure is described in detail in the information paper “DGUV Information 203-077” of the German Social Accident Insurance (DGUV). This paper is available in German and in an English translation.
Research work based on systematic measurements and testing in high-power labs has been done in the last years with respect–among others-to DC arc stability and risk parameters, to similarities and discrepancies between AC and DC arcs as well as to testing of PPE. In the paper, the correlations and dependencies of the DC arc risk parameters (arc power, arc energy, thermal incident energy) from the electric system parameters are analyzed. Conclusions are drawn on how to calculate arc power and arc energy. On this base an algorithm was developed for determining these parameters and to select the appropriate PPE against the thermal hazards of the DC fault arc. The algorithm was already introduced in the new edition of the user guide DGUV-I 203-07S.
this paper is about the impact of distributed generation (DG) on live working, particularly on the special operating mode required to limit the effects of incidents in the work site. It also has to do with the consideration of modern intelligent networks on working conditions.
Providing efficiency for the power utilities in the operation of replacement OHL conductors (reconductoring) in particular when operated under “induction” due to energized circuit adjacent the line under replacement.
