Method and apparatus for monitoring live electrical equipment at high or medium voltage

A method of monitoring live electrical equipment at high or medium voltage, the method comprising the following steps;

• emitting a radio wave for illuminating a zone of the equipment in radio energy close to a point where physical parameter is to be monitored;
• re-emitting the received radio wave with amplitude-modulation responsive to said physical parameter crossing a threshold at said point;
• and
• receiving the retransmitted radio wave outside the equipment and demodulating it to obtain a signal indicative of said threshold being crossed.

An apparatus for monitoring live electrical equipment at high or medium voltage, the apparatus comprising:

• at lease one sensor unit placed on the equipment, comprising a first radio antenna, a sensor for producing a digital signal related to a determined physical parameter at a point to be monitored, and amplitude-modulation means connected to the sensor and to the first antenna, and activated by the energy received by said antenna;
• a transceiver unit placed outside the equipment and having a second radio antenna for emitting a radio wave to illuminate the first antenna, a power supply source, and signal processing means connected to the second antenna;
• and
• the first antenna retransmitting towards the second antenna the radio wave that has been transmitted thereby, while simultaneously amplitude-modulating it in response to the output signal of the sensor, said signal processing means being arranged to provide a signal related to said parameter.

An apparatus for monitoring live electrical equipment at high or medium voltage, the apparatus comprising:

• at least one sensor unit placed on the equipment, comprising a first radio antenna, a two-state sensor responsive to a determined physical parameter at a point to be monitored, the sensor changing state when said parameter crosses a threshold, and amplitude-modulation means connected to the sensor and to the first antenna, and activated by the energy of a radio wave received by said antenna;
• a transceiver unit placed outside the equipment and having a second radio antenna for illuminating the first antenna, a power supply source, and signal processing means connected to the second antenna;
• and
• the first antenna retransmitting towards the second antenna the radio wave that has been transmitted thereby, while simultaneously amplitude-modulating it in response to the state of the sensor, said signal processing means being arranged to provide a signal sign (12) indicative of the state of the sensor.

An apparatus for monitoring high or medium voltage electrical equipment, the apparatus comprising:

• at least one sensor unit per phase, the unit being placed on a live element of the equipment and comprising a first radio antenna, a two-state sensor responsive to temperature at a point of said live element, the sensor changing state when the temperature crosses a threshold, and amplitude-modulation means connected to the sensor and to the first antenna, and activated by the energy of a radio wave received by said first antenna;
• a transceiver unit placed outside the equipment and having a second radio antenna for illuminating the first antenna, a power supply source, and signal processing means connected to the second antenna;
• and
• the first antenna retransmitting to the second antenna the radio wave transmitted by the second antenna together with amplitude-modulation in response to the state of the sensor and to information identifying the sensor, said signal processing means being arranged to supply, for each sensor unit, a signal sgn(12) indicative of the state of the sensor together with associated identity information Id(12).