Hospital has very high standard for the electricity safety and reliability, but there is great amount of the nonlinear devices such as the X-ray machine, Magnetic resonance machine (MR), Computer Tomoscan (CT), variety of LED lighting system, Frequency Inverter-base air conditioner，elevator equipment, UPS, EPS etc. The above mentioned devices produced 3rd, 5th and 7th order harmonics. The harmonics which produced by the nonlinear devices will affect the stable running of the precise health care equipment, the composite of the 3rd order harmonic at the natural line will cause the natural line overhead damage the power distribution system of the entire hospital.

Take a Upper-second Class Hospital as example, the power supply was composed by 4 units of 10kV/0.4kV, the THDi of the load current is about 18%, distributing at 3rd, 5th , 7th and 9th order harmonic. According to the testing report, the engineer set 4 units of 150A APF module for each transformer. Since the AHF implemented, the incomer power distribution cabinet measuring the THDi, THDu has significant decline, the natural line current also has obvious decent. The AHF power quality improvement solution secure the stable running of the health care equipment of the hospital. 

As can be seen from the waveform before and after the harmonic filtering, the THDu of the hospital power grid decline from 8.1% to 2.4%, the THDi decline from 31% to 3.9%, the natural line current decline from 186A to 99A.