Transmission & distribution | Breaker breakthrough


On 29 August, Hitachi Energy unveiled, in conjunction with CIGRE Session 2022, what it describes as “the world’s first fully tested SF6


tank breaker employing the new technology is to be installed for Eversource in the USA in 2023 -free 420 kV circuit-breaker.” A world-first SF6


accelerated roadmap, announced by Hitachi Energy at CIGRE Session 2021 (see Modern Power Systems, Nov/Dec 2021, pp 51-53).


The new circuit-breaker, which has passed all relevant tests described in the IEC and IEEE standards for 63 kA, 5000 A, 50 and 60 Hz, marks attainment of a significant milestone in the EconiQTM


The roadmap sets out Hitachi Energy’s development timetable for its EconiQ portfolio of SF6


switchgear. -free high voltage breakers and


The company says it has been investing in eco- efficient alternatives to SF6


for over two decades


and its achievements include the world’s first 170 kV eco-efficient gas-insulated switchgear. Over time, it has been working to steadily increase the voltage levels of its SF6


-free


offerings, with current interruption being the biggest technical challenge. Initially, the focus was on gas mixtures employing fluoroketones, but in April 2021 Hitachi Energy (then called Hitachi ABB Power Grids) announced a cross-licensing agreement with GE relating to


Q and A with Markus Heimbach, Managing Director, High Voltage Products, Hitachi Energy


breaker? From a technology perspective, high-voltage circuit-breakers are the most sophisticated and technically challenging modules in high-voltage switchgear. They are constantly exposed to extreme mechanical and electrical stresses. For example, at the 420 kV voltage level, circuit-breakers are meant to interrupt fault currents in the region of 63000 A. The energy that needs to be tamed by the circuit-breaker in a fraction of a second is enormous. It is comparable to a car hitting a wall at a speed of around 100 km/h, and for a brief moment, the temperatures inside the circuit-breaker will be hotter than the surface temperature of the sun. SF6


What were the main challenges that had to be addressed in developing the 420 kV SF6


has excellent insulation and current interruption


properties, which enables high-voltage equipment to be as compact as possible. Furthermore, modern SF6


circuit-


breakers use gas circuit-breaker technology, which means a gaseous medium is used for both switching (including current interruption) and insulation. Gas circuit-breaker technology is proven to be reliable and scalable. Scalability means that products using the same technology can cover a voltage level from 52 kV up to ultra-high voltage, 1200 kV. As SF6


alternatives, the main


challenges are to reach the same performance and scalability as SF6


at similar size.


Size is absolutely critical in modern high-voltage switchgear as installations tend to be near urban centres, where land and space are limited, and substations need to be as compact as possible. To achieve compactness without using SF6


, the deep


scientific understanding of the process inside the breaker needs to be translated into the design of the circuit-breaker. So far, this challenge has been achieved only for the lower voltage levels, up to 170 kV.


And how were they addressed? For over two decades we have been investing in research


How significant is this achievement? This is a historic milestone and ground-breaking achievement for the high-voltage industry. SF6


has been used for decades,


and now we have one of the most demanding, high-end, ratings commercially available without the use of SF6


. Eliminating SF6 is such an excellent gas and so important for the high-


voltage grid, it is a big feat to find an alternative gas to replace it at all high voltage levels. For SF6


means eliminating environmental impact


and reducing carbon footprint. This proves that fluoronitrile gas mixtures are the future of the high-voltage industry. The 420 kV circuit-breaker is now fully tested as described


in IEC and IEEE standards. The scalability of our technology is proven and we are the first in the world to deliver a 420 kV, 63 kA circuit-breaker free of SF6


– a significant technology


achievement in the high-voltage industry. It is also a key milestone in reducing environmental impact. In comparison, a conventional SF6


420 kV GIS contains around 1200 kg of SF6


per bay, which is around 15 times more than a 145 kV GIS. This breakthrough technology is the key enabler to unlocking the widest range in high-voltage eco-efficient switchgear applications. With a reliable and scalable technology with the lowest carbon footprint, we are enabling our customers and the industry as a whole to rapidly transition to eco-efficient solutions to advance a sustainable energy future for all.


-free circuit


and development in the field of eco-efficient technologies and pioneered the world’s first high-voltage eco-efficient switchgear. We have gained years of field experience from lower voltages and over time, and we have been successful in continuously increasing the voltage levels to 420 kV. Using gas circuit-breaker technology has enabled us to go alternatives.


beyond 170 kV and to achieve 420 kV with SF6


Gas circuit-breaker technology, with its high reliability, also enables us to retain around five decades of experience and knowledge from SF6


developments and technology. The key to this success is the scientific understanding of the


processes inside the breaker, and translating the design rules from SF6


to the new gas mixture, therefore keeping a similar


performance and size. As a result, using the fluoronitrile (C4-FN) mixture we can achieve the same compactness as equipment based on SF6


. -free 420 kV dead


16 | September 2022| www.modernpowersystems.com


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45