Overvoltage and Insulation Coordination of Overhead Lines in Multiple-Terminal MMC-HVDC Link for Wind Power Delivery

Table 3

Required values of air gaps under switch impulse overvoltage for a 4-terminal MMC-HVDC project.

Lines	Switching overvoltage level (p.u.)	Required 50% switching impulse discharge voltage	Altitude (m)
			0	1000	2000
A-D	1.9 p.u.	1130	2.73	3.13	3.63
C-D	1.93 p.u.	1147	2.79	3.21	3.73
B-C	1.9 p.u.	1130	2.73	3.13	3.63
A-B	1.7 p.u.	1011	2.4	2.75	3.2