新概念英语2册53课问题.有俩句话：1.the snake then wound itself round the wi

新概念英语2册53课问题.
有俩句话：
1.the snake then wound itself round the wires
2.He noticed the remains of a snake which was wound round the electric wries of a 16000-volt power line.
我有俩个问题：
1.这俩句话中都有wound round,为什么第一句要加itself,而第二句不用.
2.第二句中能否把末尾的“of a 16000-volt power line.”改成of 16000-volt,因为我觉得power line.和electric wries 重复了.