By Richard Smith, Smith Brothers
Within any power system, the ability to disconnect and isolate electrical equipment is of paramount importance for safety reasons, as well as to enable both preventative maintenance and emergency repair work to be carried out efficiently. From low voltages of 11 kV up to high voltage systems producing 132kV, it is switchgear that enables critical parts of the circuit to be isolated and de-energised.
In the field of electrical and power engineering, when the voltage increases, so too do the risks-both to the individuals carrying out the work and to the equipment itself. Safety is therefore always the number one priority for any professional electrical contracting firm. When the occupational hazards are unavoidably heightened by higher voltage requirements, safety systems must be enhanced and adhered to accordingly, from the planning, testing and installation of switchgear and transformer equipment, through to its operation and maintenance. There are, however, several wider challenges facing electrical contractors who are hired to conduct high voltage switchgear and transformer work. This article focuses on electrical contractors’ responsibilities and elaborates on the key challenges they face when conducting transformer work and how they can overcome those challenges.
Although applicable to all types of installation and maintenance, the challenge of coordinating site access and timings can be especially heightened when working on higher voltage switchgear projects. This is mainly due to the necessity of arranging power outages with distribution network operators (DNOs) that equally satisfy customer requirements. It is inevitable that networks will be disrupted to connect into the system, even if conducting only routine safety and efficiency testing of the equipment.
In addition, because power outages cause knock-on effects to those reliant upon the power being delivered, projects must be carefully planned to minimize inconvenience. This makes seasonality another key consideration, as most DNOs will not permit an outage for installation or maintenance work during the winter months, when power access is crucial. Similarly, for industrial clients, outages can often result in production being halted while work is carried out. These jobs also must be scheduled as far in advance as possible to enable alternative power to be arranged beforehand.
In addition to the difficulties of working to client specifications, managing time-critical deliverances often are beyond the contractor’s control. Successfully installing new switchgear on time, for example, is almost entirely reliant upon suppliers meeting delivery deadlines-without the equipment there to be installed, the contractor’s job is impossible.
Along the same lines, organizing witness testing for DNO projects carries its own set of preparatory challenges. While clearances are required for operatives on specialist sites, the process isn’t always straightforward. Careful planning and third-party scheduling is required before the project gets off the ground to ensure that the work can be conducted.
While initial difficulties reside in project preparations, many factors outside of human control present further substantial obstacles. Differing from lower voltage equipment that can be entirely housed within a building, switchgear for higher voltages of 66kV and above is usually mounted externally, requiring installations and maintenance work to take place outside. Both the systems and workers are exposed to the elements, making work difficult and even dangerous in high winds or torrential rain. Weather conditions and other external factors, therefore, must be considered.
Although DNOs won’t usually coordinate installation and maintenance works during winter, these timing restrictions don’t apply to all projects. In addition, even during warmer months, adverse weather conditions can still pose a huge challenge to contracting teams, as well as a hazard to equipment. Offshore wind sites, for example, require transformers and switchgear that can withstand humidity, variable temperatures and saltiness of the marine air.
These environmental challenges vary significantly across different sectors, too. Gaining access to wind and solar sites-both on and offshore-can be especially hazardous in winter.
Mother Nature is not something that can be controlled, therefore, contractors must conduct individual risk assessments for every site and schedule. Sometimes the conditions of the project are manageable, if added caution is exercised, but there will be occasions when work must be postponed if the dangers pose too great a concern.
The nature of modern switchgear and transformer equipment makes it easier to install, safer to use and more environmentally friendly. SF6 gas and vacuum equipment has largely replaced oil-filled tanks, facilitating automatic control and consequently reducing the hazards associated with testing, maintenance and operation. This switchgear also is far less risky to install and is a “greener” alternative than the older liquid systems.
As technology advances, however, so too do project regulations and training requirements for those installing, maintaining and operating the systems. Industrial installations, for example, necessitate that the substation building and concrete plinths be built to increasingly stringent specifications. Failure to keep up with these developments can be detrimental not only to project progress, but also the equipment and workers’ safety.
Relay systems are similarly advancing. Their multi-functionality means that fewer are now needed to fulfil system protection requirements, resulting in increased efficiency and cost-savings. But again, the safe operation of modern electronic protection relies on a much higher level of technical training among workers.
In addition to keeping up with advancing equipment and installation techniques, the capability to deal with older systems also is crucial. In an ideal world, all switchgear and transformers would be periodically upgraded and replaced with more innovative models. But, economic and practical limitations mean that this isn’t always the case. Contractors, therefore, must be trained in the maintenance of older equipment, as well as the installation of newer technologies.
With such a wide breadth of switchgear equipment from an array of manufacturers, having an awareness of the technical differences and operational restrictions is undeniably tough, but essential. Parts often are difficult to source for repair work, especially if the originals have been discontinued. That said, alternatives can usually be sourced, if the contractor knows what to look for.
Alongside the trade and discipline-specific qualifications required for switchgear fitters, cable jointers and commission engineers, appropriate health and safety accreditations also are required. High voltage safety rules are far more stringent-correlating with the hazardous nature of the work being carried out-so specialist training and authorization in safe systems of work is an essential requirement for teams. In addition, site-specific certifications often are a prerequisite. Water assignments, for example, require workers to undertake hygiene training before site access can be granted.
While appropriate preparatory measures should always be taken with any high voltage installation or maintenance project, unforeseen challenges can, and often do, crop up. By building good relationships with clients, suppliers and subcontractors and working together collaboratively, however, any obstacles that may appear can be overcome safely and effectively.
Richard Smith is joint managing director at Smith Brothers, an electrical engineering specialist company based in Elland, West Yorkshire county, England. It provides high voltage power to clients throughout the commercial, renewables and water treatment sectors.