DC-high speed circuit breakers (DC-HSCB) have been used on the railways since their electrification at the end of the 19th century.
To ensure these vital devices perform effectively, the BALTO line of testing equipment by STEVO Electric is at your service.
Why is it so important to test DC-HSCBs? “To protect passengers in trains, rail staff and assets,” said Wim D’Hooghe, Head of Global Sales, STEVO Electric.
“There have been cases where the current on lines has increased, due to faulty circuit breakers, leading to metal melting in the trains operating along them.
Also, it’s important to protect the switch gear in traction sub-stations – again, there have been accidents in the past here too.”
When DC-HSCBs cut off the power, they also handle arcing internally to reduce the risk of electrocution for maintenance workers.
Another factor to consider, DC-HSCBs are robust devices with impressively long service lives – “up to 40 years and even longer,” pointed out Mr D’Hooghe.
“During this time, their springs and other components are simply replaced in the workshop then returned into service, typically without prior testing to check whether they are functioning correctly.”
Manufacturers of DC-HSCBs of course take every measure to ensure their products are as safe as possible. Nevertheless, factors such as ageing, i.e. wear and tear, need to be taken into account.
Circuit breakers have many mechanical parts that deteriorate during use so customers should replace various items on a frequent basis (as stipulated by the manufacturer).
Also, a breaker that hasn’t operated for a while suffers from mechanical stiffness and won’t open/close as it should.
Other factors that may impact the performance of breakers are human error, which can never be totally ruled out, and location/environmental influences like electromagnetic currents (EMC), temperature, humidity, and dirt. “Dirt is often a nasty one,” said Mr D’Hooghe.
“We recently tested an Alstom breaker that proved to be completely out of range. After cleaning the parts, it was within spec.”
Proven track record
With a decade of experience under its belt, STEVO Electric has every confidence in its BALTO range of DC circuit testing equipment. “Back in 2003, the infrastructure division of the Belgian railways, now Infrabel, asked us to build portable equipment for on-site testing of DC-HSCBs used on its infrastructure,” explained Mr D’Hooghe.
“Prior to this, while some railway companies (operators, infrastructure managers, or operator+infrastructure managers) had built test equipment themselves, there generally wasn’t any around.”
In response, STEVO Electric developed its first portable testing device for this specific use. Since then, for the transport sector (trains, subways, trams and trolleys, both traction substations and rolling stock), the company has developed the following BALTO product range:
- BALTO Modular 3,000-30,000A, which generates up to 15,000A on a single trolley, and up to 30,000A with two trolleys in a master-slave configuration
- BALTO Modular 4,000A-40,000A, producing up to 20,000A on a single trolley, and up to 40,000A with two trolleys
- BALTO Compact, a compact version of the BALTO Modular, this device has a single power unit and can generate currents up to 3,000A or 4,000A
The power units contain sophisticated electronics and act as current sources, drawing energy from batteries and ultra-capacitors and injecting a high current into the DC-HSCB. These types of system are also known as primary injection test equipment.
BALTO units are in use today on rail networks in North and South America, Europe, China, Southeast-Asia (Singapore and Hong Kong), and Africa.
Clients include rail infrastructure managers, operators and companies such as Infrabel (Belgium), Deutsche Bahn (Germany), NedTrain (the Netherlands), Docklands Light Railway (DLR-U.K.), Metrovias (Argentina), RATP (France), and Washington Metropolitan Area Transit Authority (WMATA-US), as well as manufacturers such as Sécheron, Hawker Siddeley, and Alstom.
Given the niche market for this product and the presence of other suppliers, why are all these clients working with STEVO Electric?
“If you want to do this right you need experience,” reckons Mr D’Hooghe.
“Also, we believe our system is superior to others in terms of performance and reliability, plus it’s portable.”
Yes, being able to bring the equipment on site to perform accurate testing is a big draw, enabling valuable savings in terms of time and money.
“In the past, a few transport companies in Europe used to do primary injection tests in a central location,” said Mr D’Hooghe.
“The DC-HSCB's were disconnected from the traction substation and brought to the central workshop for testing, often using equipment designed by the transport company themselves. Needless to say, the process was time-consuming, ineffective, and often inaccurate,” he adds.
All BALTO products meet all the relevant specifications issued by standardisation bodies; namely the EN 50123-2 and IEC 61992-2 standards (slope of 200 A/second for measurement of Ids trip current)
STEVO Electric has around 70% of the global market share for rail-specific, DC-HSCB test equipment.
While business in China is booming – “the country is building new lines and systems so fast… they want the equipment to test the circuit breakers they are installing,” said Mr D’Hooghe – North America is “promising but will take time,” he reckons.
“We started introducing BALTO there in 2016 and have since sold equipment to Washington Metro and New York’s Long Island Railroad.
“Uptake is slower in the US because public transport and passenger rail aren’t as advanced or such a vital part of the transport network as elsewhere in the world.”
Since STEVO’s equipment is designed for the DC market, it covers all metro and light rail/tram systems worldwide, but not necessarily all the national rail networks: while those in countries like France, Spain, Italy, Belgium, and the Netherlands are based on DC electrification systems, others in countries like Germany, Sweden, China or India are powered by AC.
This technical characteristic explains STEVO’s focus on the world’s largest metro systems and the light rail/tramways.
In their user manuals, DC-HSCB manufacturers include information on how and when the breakers should be tested and maintained.
Although the procedures and timing indicated may differ, the general philosophy is identical: regular visual and mechanical checks to measure the important components for wear and tear, but that’s basically it,” said Mr D’Hooghe.
“None of the manufacturers specify primary injection, a simple test which demonstrates the behaviour of the breaker prior to going in service.”
Primary injection testing of DC-HSCBs in rail is not standard today; yet for High Voltage (HV) AC installations, e.g. power utilities, it is compulsory.
Why this discrepancy? Of course, following the manufacturers’ recommendations and observing stringent test and maintenance procedures significantly reduces the risks associated with short circuiting and overcurrents.
But why not provide maintenance engineers and commissioning staff with the right tools to guarantee their work is on track? The proof should be delivered by the test unit.