A system for determining a phase of a power supply coupled to a metering device. The system includes a collection device in electronic communication with a metering device connected to a power distribution network and having a memory and one or more electronic processors. The electronic processors are configured to receive a first beacon signal and measure a phasor in response to receiving the first beacon signal. The phasor is stored in the memory along with an identification value associated with the device that transmitted the first beacon signal and a first time. The electronic processors receive a second beacon signal, and extract data from the request message. The electronic processors determine whether the extracted time matches the first time and based on determining that the extracted time matches the first time stored in the memory, calculate a phase by comparing the reference phasor data to the stored phasor.