Application of APF in Harmonic Control in a Hospital

1.Analysis of project problems

A hospital mainly includes 1 # transformer and 2 # transformer in the distribution room of outpatient building, 3 # transformer and 4 # transformer in the distribution room of inpatient department, and four transformers are in normal operation. At present, they are mainly applied to the load circuit under two transformers in the distribution room of outpatient building:

Transformer 1 #: The capacity of the transformer is 2500KVA and it operates normally during the test. Its load mainly includes building air conditioning system, elevator elevator, lighting system, etc.

Transformer 2 #: The capacity of the transformer is 2500KVA and it operates normally during the test. Its load is mainly important medical equipment, mainly including X-ray machine, nuclear magnetic resonance, CT, B ultrasound machine, biochemical analyzer, etc.

High harmonic distortion rate and large harmonic current were detected in the power supply system, which caused great harm to the switch cabinet, busbar, live neutral line, medical electrical equipment with terminal load, power supply compensation equipment capacitor and reactor of the power supply system. Aiming at this problem, we have installed APF active filter harmonic control equipment according to the actual situation of the site after the equipment transformation and project preparation in the early stage, which ensures the safe and reliable operation of the electrical equipment, solves the interference of the site, excessive zero line current, serious three-phase imbalance and high harmonics to the X-ray machine and biochemical analysis instruments.

In order to solve the above problems, our company combined with the actual test data of the project and made the following treatment plans.

2.Solutions

The harmonic current distortion rate of the hospital was 17.4% before treatment and 2.2% after treatment; It was 16.6% before treatment of Phase B and 3.3% after treatment; C: 17.1% before treatment and 2.1% after treatment; The harmonic current was relatively large. The harmonic current was mainly 3 times, 5 times, 7 times and 11 times. The total distortion rate of harmonic current reached 17.2%. The harmonic current of Phase A was 210.4A, that of Phase B is 210.2A, and that of Phase C was 209.4A. The harmonic current of Phase N was the highest, which has reached 251.4A and has exceeded the national standard limit.

3.Use of APF after installation

The main load of 1 # transformer and 2 # transformer in the power distribution room of an outpatient building of a hospital is air conditioning, elevator, lighting, frequency converter, medical equipment and single-phase electrical equipment. The temperature rise of zero row was relatively high. When the maximum phase line current of the system reaches 251A, the system N line current reaches 290A level. The cable and busbar in the system generated a lot of heat, the insulating sleeve and insulating layer were seriously aged, and the harmonic wave had a great impact on the power supply and load equipment.

When the active filter APF equipment is put into use after equipment installation and commissioning, the three-phase current of the system is restored to balance, and the N-phase current is reduced from 251A to 17A, avoiding more serious accidents and problems. It effectively solves the instability of electrical equipment caused by excessive zero line current, the interference of medical equipment data, the skin effect of cable, the aging of cable insulation and other problems, and ensures the reliability of equipment operation.