By Syed Raza Hassan DADU, Pakistan (Reuters) -Authorities in Pakistan are scrambling to protect a vital power station supplying electricity to millions of people against a growing threat of flooding, officials said on Monday. Floods from record monsoon rains and glacial melt in the mountainous north have affected 33 million people and killed almost 1,400, washing away homes, roads, railways, livestock and crops, in damage estimated at $30 billion. Both the government and U.N. Secretary General Antonio Guterres have blamed climate change for the extreme weather that led to the flooding that sub…