Increasing voltage levels and realizing power-line communications are important parts of a smart grid, and because of this, the need for intelligent, digital, and multi-functional electronic sensors that can simultaneously perform the functions of high-voltage monitoring and carrier-signal demodulation in a power transmission system is urgent. Insp. ••LED-in-capacitors (LIC) is proposed inspired by TENG technology.••LIC is highly sensitive to the rate of change of the electric potential.••LIC can be used for smart self-powered high-voltage monitoring.••LIC can be used for high sensitivity demodulation in power line communication.High-voltage monitoringPower-line communicationsOne-dimensional convolutional neural networkTriboelectric nanogeneratorsWith the continuous development of power supply systems, the realization of accurate and reliable electric power calculations, relay protection, overvoltage detection, etc. would be a powerful guarantee for the safe, reliable, and efficient operation of the power-supply system. Especially, real-time, accurate realization of high-voltage (HV) monitoring is the basis for ensuring stable operation of the power supply,,,. Whether the voltage monitor can correctly reflect the voltage fluctuation, the voltage frequency, and the voltage waveform distortion caused by harmonic pollution due to the nonlinear load in the transmission system is the most important criterion for measuring the characteristics of HV monitors,. Nowadays, diverse HV monitors based on the principles of the electric field coupling, electromagnetic induction, Hall, electro-optic effects, and contact electrification, and so on are used to obtain voltage signals,,,,,. Traditional electromagnetic transformers are large and meeting the requirements of a new generation of power systems, such as online detection, high-precision fault diagnosis, and a power network that is digital, is difficult. At present, new HV monitors, such as electro-optic crystal-based monitors and D-Dot type monitors, have the advantages of small size, light weight, and digitization,,,. However, these new HV monitors also have disadvantages. For example, electro-optic crystal-based monitors require additional driving power and electr. 2.1. Fabrication of LICTwo circular copper panels with radii of 20, 30, 40, or 50 mm are used as the electrodes (1st electrode and 2nd electrode) of the LIC. The two copper panels are arranged in parallel in the horizontal direction with 40 mm between them. The positive and the negative leads of a commercial LED are connected to the upper and the lower copper panels, respectively. The two copper panels are electrically isolated by using insulating ceramics. Three-dimensional (3D) printing technology is utilized to prepare insulating brackets. An optical fiber is used to connect the LED to a photodiode. One end of the optical fiber is connected to the photodiode, and the other end is combined with the head of the LED.2.2. MeasurementA waveform generator (RIGOL, DG4162), a power amplifier (Aigtek, ATA-2161) and a high voltage generator (P-AC-20KV20W) are used to generate voltages with high-amplitude sine waveforms. The output EL waveform from the LIC is detected by using avalanche photodetectors (Thorlabs APD120A2/M) and an oscilloscope (RIGOL, DS1102E).