There is provided an apparatus (20) for monitoring a condition of an electrical power transmission medium (22), the apparatus (20) comprising: a signal source (24) for transmitting a signal (30) to travel along the electrical power transmission medium (22); and a monitoring device (26) configured to detect one or more reflected signals (34) in the electrical power transmission medium (22), wherein the monitoring device (24) is configured to use the or each detected reflected signal (34) to determine a change in capacitance of the electrical power transmission medium (22).