The commission may investigate the interstate rates, traffic facilities, or service of any public utility within this Commonwealth, and when such rates, facilities or service are, in the determination of the commission, unjust, unreasonable, discriminatory or in violation of any Federal law, or in conflict with the rulings, orders or regulations of any Federal regulatory body, the commission may apply, by petition to the proper Federal regulatory body, for relief, or may present to the proper Federal regulatory body all facts coming to its knowledge as to the violation of the rules, orders, or regulations of such regulatory body, or as to the violation of the particular Federal law.