An apparatus for measuring variable in relation to a power cable accessory, including: an RFID tag, including: a sensor configured to generate a signal indicative of the variable in its environment, an antenna, and an RFID IC electrically connected to the sensor and configured to process and modulate the signal generated by the sensor and transmit the modulated signal to an RFID reader via the antenna, wherein: the RFID tag is shaped to be fitted with the power cable accessory with its sensor in thermal contact with an electrical connector of the power cable accessory and with its antenna external to the electrical connector.