I want to know the answer to the following question:
What two systems were compare in the Soviet Union in 1970?
All the background I'm provided with is that "Thus in spite of the much higher losses in the catenary, the 3 kV DC was a little more energy efficient than AC in providing energy from the USSR power grid to the terminals of the traction motors (all DC at that time).". Is that enough to answer the question?
Answer: no