This work proposes a novel protocol within the framework provided by the draft amendment IEEE 802.15.4k meant for massive scale, low-energy monitoring of critical infrastructures. The framework is exploitable by smart grid, the next generation of electric power systems. The proposed protocol, termed primary-link - recovery-protocol, is tailored for a professionally installed star topology network and it presents the advantage of eliminating a number of relays that are required in a typical multi-hop environment. The protocol is used in conjunction with Slotted Aloha channel access every time the radio link between the traffic sink, which is also the network coordinator, and a sensor is disrupted. The proposed protocol is formulated for monitoring anomalies of various components of the smart grid distributed over a wide area. Furthermore, the protocol performance assessment is made in terms of success probability and throughput by means of a Markov chain approach and the optimal number of sensors, with respect to sensor nodes in the network, that take part to the proposed solution is identified.