A Hospital in Zhejiang Province
It is a large-scale general hospital integrating medical treatment, scientific research, teaching and rehabilitation. The hospital has more than 30 clinical and medical technology departments, 11 wards including internal medicine, surgery, orthopedics, rehabilitation medicine, geriatrics, ophthalmology and ICU, as well as a health check-up center.
Most of the electrical equipment in the hospital are single-phase loads with a large amount of third harmonics, which will superimpose on the neutral line and cause neutral line voltage offset, thus impairing the power supply quality and reliability. The precision medical instruments in the hospital are quite sensitive to power supply quality and have relatively high requirements for power quality and supply reliability. Therefore, it is necessary to improve the power supply quality of its power distribution system to maintain the power quality and reliability of the power supply system.
Figure 1: Hospital Actual Scene
The recommended solution is to install one set of NCSA Active Harmonic Filter, and adopt the selective harmonic elimination mode to mitigate the 3rd, 5th, 7th, 9th, and 11th harmonic currents of the system, which can significantly improve the power quality and reliability of the power supply system.
Key Features of NCSA Active Harmonic Filter
- Filters out system harmonics, suitable for various harmonic environments with no overload issues
- Fast dynamic compensation response time ≤ 20 ms
- Multiple harmonic filtering modes and compensation functions available
- Capable of full-load output current
- High-reliability IGBT protection architecture with excellent stability
- Touch-screen graphical human-machine interface for easy operation
Figure 2: Cabinet Diagram of NCSA Active Harmonic Filter
Since the harmonic filters were put into operation on December 18, 2014, they have significantly mitigated the 3rd harmonic currents in the neutral line of the power distribution system. The power quality measurement data of the system main circuit before and after the improvement are summarized in Table 1.
Table 1: Summary of System Improvement Effects (Before & After)
Figure 3: System Voltage and Current Waveforms (Before Improvement)
Figure 4: System Voltage and Current Waveforms (After Improvement)