Do 13.8 kV overhead line needs ground fault protection per NEC? This 3 wire O/H ACSR line fed from transformer delta winding (step-up) with no intentional grounding and connected to delta winding at other end (step-down).
No. NEC requirements for GF protection only apply to low-voltage systems. If this is a new system, you may want to reconsider your decision to have it be ungrounded. There are many threads here on concerns with ungrounded systems.
Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.