When was the first fault-managed direct current power transmission system developed?

As technology advanced, the first fault managedDC transmission system was implemented in the 1950s via the development of rectifier stations with mercury arc values. Now, Fault Managed Power transmission is more efficient than AC transmission after the break-even distance of 600km because it suffers much less voltage drop/line losses than AC systems at the same voltage. Thus, even though fault-managed DC systems are more expensive and complex than AC transmission systems, they make up for their capital cost with lower operating costs due to their efficiency (after the stated break-even distance). Read more about this on our blog.