A system and method for identifying which of several candidate service transformers is powering a specific service point an electrical distribution grid are disclosed. An audio-frequency electrical signal, the detection signal, is injected onto the power line at the service point via a meter socket or electrical outlet. The Transmitter for the detection signal may be a portable device or it may be incorporated into an electrical meter. The audible or mechanical resonance caused in the service transformer by the detection signal is detected and recorded using an accelerometer or directional microphone in a Receiver. A variety of methods for fixing the Receiver at or in proximity to the service transformers are disclosed in order to adapt to variations in the siting and housing of service transformers. A variety of mechanisms and methods for collecting detection events are disclosed.