Alstom Grid has successfully tested 820 kV bushings for HVDC converter transformers, placing the company as one of only three players in the world to manufacture this technology, which is key to ensuring the reliability of HVDC lines. The bushings are designed and manufactured at Alstom’s bushing competence centre, in Milan, Italy.
Bushings are electric devices that allow high voltage conductors to pass through earthed walls of transformers, switchgear and substation structures. DC bushings must be based on solutions that minimise the risk of oil spill inside the valve room to meet stringent fire prevention regulations in HVDC converter plants. Alstom’s 820 kV / 4500 A transformer and wall bushings have now been fully type-tested in accordance with international standards, including temperature rise tests.
“This success strengthens Alstom’s leadership in HVDC technology worldwide, following other recent announcements such as the testing of our ultra HVDC wall bushings, and our high voltage DC breaker”, said Lars Martinsson, Vice President Alstom Grid.
Alstom’s converter transformer bushings use a hybrid design to meet these specific market requirements. They demonstrate exceptional thermal performance exceeding the specified current rating of 4500 A. In parallel, the grading capacitor is totally encased by special fiberglass cones to ensure a triple barrier system between transformer oil and valve room to avoid oil spills. Pressure sensors installed on the oil impregnated paper also prevent direct gas leakages to ensure the safety and reliability of the DC equipment.
The bushings tested form part of a major 800 kV HVDC project for State Grid Corporation of China (SGCC). Alstom Grid was recently selected by SGCC to supply through-wall bushings for the Xiluodu-Zhexi ±800 kV line, as part of the country’s UHVDC development programme.
Alstom is a global leader in the world of power generation, power transmission and rail infrastructure and sets the benchmark for innovative and environmentally friendly technologies. Alstom builds the fastest train and the highest capacity automated metro in the world, provides turnkey integrated power plant solutions and associated services for a wide variety of energy sources, including hydro, nuclear, gas, coal and wind, and it offers a wide range of solutions for power transmission, with a focus on smart grids. The Group employs 93,000 people in around 100 countries. It had sales of over €20 billion and booked close to €24 billion in orders in 2012/13.
Alstom Grid has 130 years of expertise in electrical grids. Whether for utilities or electro-intensive industries or facilitating the trading of energy, Alstom Grid brings power to its customers’ projects. Alstom Grid ranks among the top 3 in electrical transmission sector with an annual sales turnover of more than €4 billion. It has 20,000 employees and over 90 manufacturing and engineering sites worldwide. At the heart of the development of Smart Grid, Alstom Grid offers products, services and integrated energy management solutions across the full energy value chain—from power generation, through transmission and distribution grids and to the large end user.
Press contacts Alstom Italy
Daniela Pradella – Tel. +39 02 348 2586205; mob. +39 348 2586205
Nathalie Bourotte (Alstom Grid) – Tel: +33 1 49 01 62 17
 HVDC lines: high voltage direct current lines, the so-called “energy highways” of the future, are designed to transport more energy over longer distances while cutting electrical current losses, and to connect intermittent renewable energy into the grid.
 While wall bushings are based on a pure gas and composite insulator technology, converter transformer bushings use a fully sealed oil impregnated paper (OIP) grading capacitor for the interface with the transformer and a composite insulator filled by SF6 gas for the part of the bushing that protrudes into the valve hall. This technology is known as Hybrid.