Wireless powered communication (WPC) with cooperative relaying is a promising strategy to improve reliability and energy efficiency in industrial wireless sensor networks (IWSNs), particularly the use of a combination of WPC with multi-relay technologies. This paper considers a multi-source wireless powered IWSN with beacon transfer in the downlink and cooperative information transmissions in the uplink, where the energy harvesting sources harvest energy and receive information simultaneously from the beacon power and volunteer to serve as relays whenever they have enough harvested energy for cooperation. In such multi-relay scenarios, conventional schemes select the relay with the “best” characteristics in energy or in channel quality as the only best relay in considered networks, which would be not valid when multiple sources are present, where the only best relay’s energy highly likely to get drained in frequently cooperation. The key contribution of this paper is that a cooperation protocol with multiple best relays is proposed. It addresses the “energy drain” problem and is easy to implement in practical IWSNs. Besides, to reduce the possible conflicts in relay selection and further improve the achievable performance, two selection algorithms stand from separately source perspective and relay perspective are studied for the centralized scenarios, and a distributed competition algorithm is developed for the distributed scenarios. Simulation results demonstrate the performance of the provided schemes.