Data from Electricity of Vietnam (EVN) reported that among 106 power plants with a total capacity of 5655.5MW registering for commercial operation (COD) testing, 28 power plants with a total capacity of 1,247.4MW have received COD acceptance. In addition, hundreds of solar power plants with a minimum capacity of 40MW have been energised. By the end of 2021, the total capacity of renewable energy sources expected to operate is 21,951MW, comprising 8,972MW of farm solar power, 7,630MW of rooftop solar power, and 5,349MW of wind power.
|Checking solar panel failure with Fluke thermal camera |
According to Le Van Tai, project manager of Unitek Trading Co., Ltd., an authorised distributor in Vietnam for the world's leading measurement and calibration companies such as Fluke, TRTest, Rotronic, Qualitrol, or Amprobe, the operation of substations or transmission lines in power plants always requires the highest attention and accuracy and harbour a lot risks and dangers.
Each power plant owns a transformer station and transmission line of 110kV, 220kV, or 500kV contingent upon the project's actual capacity. The stability in operation along with the life cycle of transformers and electrical equipment depends on the insulation system's endurance when subjected to high electric fields of up to 500kV. During operation, the insulation system will deteriorate owing to various environmental influences.
Tai indicated that projects’ issues commonly arise from unstandardised or degraded grounding systems, heat generation on solar panels or DC Combinerbox connection cabinets. For substations, problems may include insulation degradation due to partial discharge (PD) that is not identified and addressed in a timely manner. Hence, periodical tests should be conducted in order to avoid potential risks.
Vietnam is one of the world's three regions with the most thunderstorms and lightning. Therefore, direct and transmitted lightning protection of solar and wind power systems is essential. Tai said that projects will frequently have a direct and transmitted lightning protection system.
However, during operation, the lightning protection grounding system will degrade and no longer match the standards previously committed by the engineering, procurement, and construction (EPC) contractor to the investor, which is 4 ohms as specified in the regulation on grounding resistance in TCVN 4756:1898.
Lightning is another source of damage to the solar panel sides, apart from common factors such as dirt, cell button cracks, bypass diode failure, and more. According to Tai, the quickest method to determine the health of solar batteries is thermal imaging. The damaged parts that generate heat are visualised on thermal images, supporting technicians in promptly detecting and addressing the problem.
Another factor that needs to be controlled strictly to ensure the safe and stable operation of substations is partial discharge (PD). Nguyen Phuc Hung, co-founder of the Reliability Centered Maintenance Institute (RCMI) in Thu Duc district explained that surface PD produces sound waves with a frequency range mostly between 20kHz and 110kHz. The main components requiring PD testing include insulation systems, transmission lines, equipment switches, insulators, medium voltage cable terminals, cabinets, and transformers. Traditional methods of testing PD are heavily dependent on the technician's skills and experience.
|PD analysis report template with AI technology from Fluke ii910 |
However, Hung shared that at present his RCMI has substituted the Fluke ii910 Acoustic Imager in teaching and service packages for traditional ultrasonic testing equipment. "I highly appreciate Fluke ii910 due to its secure, rapid, and simple method for detecting and locating PD. By implementing SoundSight and SoundMap technologies, the equipment converts the sound of the discharge into a visual image on the meter display. The frequency range of 2-100 kHz and the filter enables us to easily extract environmental noise, thereby timely identifying the locations where PD occurs," Hung said.
Safe distancing is also a concern when testing in a high voltage environment. The Fluke ii910 can detect PDs and corona phenomena at a distance of 120 meters.
Hung believed this is an ideal instrument for high-voltage electrical technicians, electrical test engineers, and grid maintenance teams tasked with the continual testing and maintenance of power distribution as well as high-pressure industrial equipment.