Delta PQC Series Active Power Filter (APF) Protects the Operations in Hospitals

Industry background
Hospitals are places where reliable power distribution is needed to guarantee patient health and save lives. Continuity and reliability of power supply are extremely important. Automatic power restoration time of different healthcare venues is as follows: category 0 venues t≤15s; category 1 venues 0.5s≤t≤15s; and category 2 venues t≤0.5s.

The use of new medical equipment, such as X-ray machines, CT scanners, MRI scanners, and others is increasing in hospitals. Equipment loads contain a high volume of harmonic current, and can impact the hospital power distribution system thereby reducing power quality. Harmonic management is necessary to ensure the safety of hospital distribution systems.

UPSs are increasingly common as hospitals pursue a reliable power supply. As most UPSs use 6-pulse or 12-pulse rectifiers, a high volume of harmonic current can flow into the grid and affect grid stability.

Customers
One hospital in Jilin province and another hospital in Inner Mongolia province, China.

Power quality problem description
Harmonics affect lighting stability and interfere with precision medical instruments such as CT scanners, MRI scanners and ECGs, reducing examination accuracy and ultimately affecting physician diagnoses of patients’ conditions. In addition, high volumes of harmonic current also reduce the stability of hospital distribution systems, which result in power outages due to tripping and the necessity of harmonic elimination.

Solution
The harmonic elimination solution is diagrammed below. Referring to onsite inspection, pilot testing and assessment, an APF is installed at the secondary site of the LV distribution transformer. In this project, twelve 75A APF power modules are implemented as shown below.

 

Effectiveness
The effectiveness of the PQC active power filer is significant, as shown in the data below:

Current waveform and THD before and after Delta PQC active power filer implementation are shown below:

Voltage waveform and THD before and after PQC active power filter implementation are shown below:

 

Conclusions
After implementing an APF in a large hospital in Jilin, the lighting system became stable, there were reduced reports of extreme noise interference on instruments, machine stability was enhanced, failure and maintenance frequency was reduced, and harmonic impact on the stability and safety of the hospital distribution system were eradicated.