Background
A certain broadcasting center, as a core facility of a local television station, has a main power load including wireless signal towers, network data centers, and broadcasting centers. It needs to ensure the stable operation of wireless signal transmission monitoring and live and recorded broadcasting systems. It extensively uses non-linear equipment such as silicon controlled rectifier (SCR) dimming devices, fluorescent lamps, and metal halide lamps, which generate high-order harmonics during operation. Since programs need to be continuously broadcast and the equipment operates for extended periods, harmonic pollution threatens the accurate and high-quality broadcasting of programs, making pollution control an urgent necessity.
Power Quality Issues
Harmonic Sources
Theater lighting systems, SCR dimming equipment, and mechanical frequency converters are the main sources of harmonics, generating low-order harmonics such as the 3rd, 5th, and 7th, as well as high-order harmonics above the 40th. The harmonic distortion rate of stage lighting systems is 26%-110%. The 3rd and 3Nth harmonics superimpose on the neutral line, and the neutral line current can reach three times the phase line current.
Hazards
Harmful effects include malfunctions and crashes in mechanical and electronic control systems and television broadcasting equipment; audio and video distortion; interference with electroacoustic systems, affecting sound quality; resonance between the power grid and capacitors, damaging equipment; increased line losses; neutral line overcurrent causing transformer tripping and cable overheating; and malfunctions in relay protection systems, metering errors, and interference with communication systems.
Solution
Referring to GB/T14549-1993 (total harmonic distortion rate limit of 5% for 0.38kV power grid voltage) and IEEE519/1992 standard (odd harmonic current distortion rate ≤10%), we adopted the L-HTS series active harmonic mitigation products from Reed Electric (UK) to customize configuration solutions based on harmonic distortion rates in key power distribution rooms such as wireless signal systems, concert halls, and multi-functional demonstration halls, blocking harmonic interference at the power distribution nodes.
Benefit Analysis
Treatment Effects
The current waveform was restored to a sine wave; the THDV of the thyristor room's incoming cabinet decreased from 11.63% to 4.20%, and the THDI decreased from 34.27% to 5.44%; the THDI of the concert hall and multi-purpose hall were both ≤10%, and the power factor improved from 0.7166 to 0.9578, meeting national and international standards.
Economic Benefits
Reduced additional equipment losses and improved the load capacity of transformers, etc.; extended the lifespan of transformers and lighting fixtures, reducing maintenance costs; the apparent power saving rate of the multi-purpose hall was 17.8%.
Operational Benefits
Reduced equipment failure rate, avoided power outages, reduced interference with communication and automatic control systems, and ensured the quality of program broadcasting and the stable operation of the center.