A current through a horizontal power line flows in east to west direction .What is the the direction of the magnetic field at a point directly below it and at a point directly above it?

Applying right hand thumb rule, we can find the direction of magnetic field lines.

ie, if we hold the wire with our right hand with the thumb pointing in the current direxction ie from east to west, the curling fingers will go into the plane above it and the fingers will come out of the plane below it.