Impedance Measurement System for Actively Transmitting Loads on Power Line

摘要

A measurement system to measure both the access impedance of the low voltage power grid and the impedance of a device connected to it in the frequency range of narrowband power line communication systems is presented. Injecting a signal into the power line at the connection point of a device and measuring the resulting voltage and the currents both to the device an to the grid allows for a concurrent measurement of both impedances, while measuring the current of the signal injection circuitry results in a redundant information that allows assessment of the measurement quality. Using a current source to inject the measurement signal minimises the effects on device behaviour for actively controlled or actively transmitting devices under test, allowing the measurement of the impedance of an active transmitter. To be able to measure cyclostationary behaviour of both the grid and the device under test, the measurement is done at a high temporal resolution and synchronised to the mains voltage.