古城古国
Ancient city and ancient state
古城墙
ancient city wall
ancient circumvallation
Protection of Ancient City Wall
Ancient circumvallation of Pingyao
开封古城墙
Kaifeng ancient city wall
800kV穿墙套管
800 kV wall-through sleeve
不对称故障穿越
asymmetrical fault ride through
不对称故障穿越(不间断)运行
asymmetrical fault ride-through operation
不对称性故障穿越
unbalanced fault ride through
步进变频穿墙雷达
stepped-frequency through-the-wall radar