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Application of Low-Voltage Active Filter in Hospital Building


2021-02-08

1. Introduction
    In order to improve the level of medical services, modern medical institutions continue to introduce new and complex advanced medical equipment such as nuclear magnetic resonance, CT machine, X-ray machine, Hemodialysis machine, etc. At the same time, a large number of energy-saving lighting equipment, inverter air conditioners, elevator equipment, etc. put into use. These devices are non-linear devices, and a large number of high-order harmonics will be generated during operation, which will cause certain interference to the power distribution system and medical equipment. At the same time, these advanced medical equipment have high-end computer components and a large number of highly sensitive microelectronic devices. They have high requirements on the power quality of the power supply and are very sensitive to voltage fluctuations and power harmonics. Serious power harmonic problems can lead to medical treatment. The damage of the equipment even leads to the occurrence of medical accidents. 

 

2. Analysis of Harmonic Source, Harmonic Characteristics and Harmonic Harm of the Hospital Building Power Supply System

2.1  Source of harmonics

Main classification Facilities and equipment names
Building facilities Elevator equipment
central air-condition system
Fire water pump
lighting device
Medical Facilities Operating room, laminar flow room system
ICU, delivery room, neonatal care unit, hemodialysis center, etc.
Preparations, samples, blood preservation and freezing facilities
Hospital office automation facilities
Medical diagnostic equipment Main diagnostic equipment, such as spiral CT machine, color Doppler, MRI machine, laparoscope, EEG machine, chromatograph, various functional testing instruments, etc.
Main treatment equipment, such as ventilator, hyperbaric oxygen chamber, various monitors, laser treatment equipment, etc.

 

 

2.2 Harmonic characteristics

Harmonic source load type  Frequency of harmonic current Harmonic current distortion rate
Lighting fixtures, computers, etc 3, 5, 7, 9, etc. (2n+1) times 7~10%
Electronic testing equipment, operating room, gamma knife, etc 3, 5, 7, 9, etc. (2n+1) times 10~15%
CT, magnetic resonance, DSA, etc. 3, 5, 7, 9, etc. (2n+1) times 30~40%
Accelerator, X-ray machine, gastrointestinal machine, etc. 3, 5, 7, 9, etc. (2n+1) times 50~60%
UPS, variable frequency ventilation equipment, elevators, etc. 3, 5, 7, 9, etc. (6n+1) times 25~35%

 

 

2.3  Harmonic hazard analysis
2.3.1 The harm of harmonics to the distribution system
   Make the additional loss of power components increase, easy to cause fire, affect the normal operation of electrical equipment, cause power network resonance, make the relay protection wrong action, electrical measurement error is too large, crash the industrial control system

2.3.2 Hazard of Harmonics to Medical Equipment
 Causes synchronization imbalance and data errors of devices that rely on microprocessor technology, directly endangers the safety of the internal electronic circuits of the device, causing breakdown or discharge, affecting the performance and accuracy of precision medical equipment
 
3.
Grid harmonic standard requirements

3.1 Harmonic current limit

Calculation standard: According to IEEE-519, the harmonic current limit is calculated according to Table 3-1

Table 3-1 IEEE519 harmonic current limit Ih/IL

ISC/IL Ih/IL (%) General power distribution system (120V~69kV) THDi (%)
h<11 11h<17 17h<23 23h<35 h35
<20 4.0 2.0 1.5 0.6 0.3 5
20~50 7.0 3.5 2.5 1.0 0.5 8
50~100 10 4.5 4.0 1.5 0.7 12
100~1000 12 5.5 5.0 2.0 1.0 15
>1000 15 7.0 6.0 2.5 14 20

 

3.2   Voltage quality index limits

The harmonic voltage limit should meet the harmonic voltage index specified in IEC61000-3-6, as shown in Table 3-2:

Table 3-2 MV, HV and EHV harmonic voltage planning level index values (percentage of nominal voltage)

Non-3 times odd harmonics 3 times odd harmonic Even harmonics
Harmonic number Harmonic voltage (% Harmonic number Harmonic voltage (% Harmonic number Harmonic voltage (%
h MV HV-EHV h MV HV-EHV h MV HV-EHV
5 5 2 3 4 2 2 1.6 1.5
7 4 2 9 1.2 1 4 1 1
11 3 1.5 15 0.3 0.3 6 0.5 0.5
13 2.5 1.5 21 0.2 0.2 8 0.4 0.4
17 1.6 1 >21 0.2 0.2 10 0.4 0.4
19 1.2 1       12 0.2 0.2
23 1.2 0.7       >12 0.2 0.2
25 1.2 0.7            
>25 0.2+0.5×(25/h) 0.2+0.5×(25/h)            

Note: Total distortion rate (THD): MV network is 6.5%, HV network is 3%; 110kV is calculated according to HV, and 35 and below is calculated according to MV.

 

4.  Application of STS-APF Low Voltage Active Power Filter in Hospital Building

4.1  Application of active power filter

The newly-built outpatient and inpatient complex of a large tertiary hospital has 4 transformers of 2000kVA and 1 1600kVA, and a diesel generator of 800kW. According to the load rate of the non-linear load equipment of each transformer in the hospital and the corresponding harmonic distortion rate and The simultaneous utilization rate of each non-linear device is used to calculate the magnitude of the harmonic current, and 5 sets of STS-APF active filters with different capacity specifications are configured.

The following takes the comparative analysis of the power quality test of the power distribution system before and after the 1#STS-APF active filter is put into operation as an example. The load of the 1# transformer is mainly lighting, elevator, submersible sewage pump, and computer center etc.

4.1.1 Data before and after the operation of the active power filter
1Before the active filter was put into use, the current waveform distortion was serious. The harmonic content of the three-phase current was 19.7%, 27.8%, and 26.6%, respectively, the three-phase current was 45A, 40A, 64A, and the neutral current was 37A.
2After the input of the active power filter, the current waveform distortion is obviously improved, and the harmonic content of the three-phase current is obviously reduced, which is 2.9%, 2.8%, 3.4%, respectively. The three-phase current is 47A, 48A, 47A, and the neutral line current is 5A.
3The current waveform is improved obviously, and the current waveform is approximately sinusoidal after the use of the filter. The expected goal and effect of harmonic control are achieved.

4.1.2 Data recorded before and after the active power filter is put into operation

4.2 Application significance of active power filter in hospital building
    Protect the safety of medical electrical equipment, purify the power supply, protect the power factor compensation equipment, prevent the malfunction of the protection device, reduce the power loss, and expand the power supply capacity of transformers and generators.

 
4.3 Main technical specification of active filter.

Wiring Three-phase three-wire or three-phase four-wire
Access to the voltage 3×380V ±10%
Access frequency 50Hz ±2%
Dynamic compensating response time Dynamic response < 4ms, full response time < 20ms;
switching frequency 10kHz
Function setting Compensate only harmonics, only reactive power, both harmonics and reactive power; manual and automatic switching.
Harmonic compensation times 2-21 times
Type of protection DC overvoltage, IGBT overcurrent, device temperature protection
Overload protection Automatic current limit at the set value, no overload
cooling method Smart air cooling
noise  65db (In the cabinet and operating in rated state)
Working temperature -10℃~+45
Working environment humidity 85%RH  Non-condensing
installations Indoor installations
The altitude 1000m (Capacity reduction is required for higher altitude)
Inlet and outlet mode Bottom in and bottom out
Protection level IP21
Intelligent communication interface RS485/MODBUS-RTU
Remote monitoring Optional
Dimensions (mm)
(W×D×H)
30A 50A 75A 100A
600×500×1500 600×500×1500 600×500×1800 800×600×2200
Weight (kg) Three-phase four-wire Three-phase three-wire
30A50A 75A100A 30A50A 75A100A
280 360 240 290

 

 

4.4  Active filter component list

Main products list:
No. Name Model Qty.
1 APF electrical cabinet 800X600X2200 1
2 Current transformer APFCOV-CVT100 1
3 The controller APFMC-C100 1
4 reactor APF-RE.(S)DG-100 1
5 Active current transformer LT208-S7 3
6 filter STS-WF001 2
7 The circuit breaker CVS160FTM160D4P3D 1
8 contactor LC1D150M7C 1
9 Microcircuit breaker NDM1-63C32 1
10 Intermediate relay MY4NAC 2
11 R-type transformer R320-0.38/0.22 1
12 Harmonic detector ACR350EGH 1
13 electric wire 16mm2 A number of
14 electric wire 4mm2 A number of

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.  Conclusion
   This article analyzes the harmonic sources, harmonic characteristics and hazards of hospital buildings, and compares and analyzes the situation before and after the active filter is put into use through the application case of the active filter in the low-voltage power distribution system of a large hospital. The harmonic control technology of the filter is one of the effective means to improve the quality of power supply. It can control the generated harmonics to a minimum range, achieve scientific and reasonable power use, suppress grid pollution, improve power quality, and ensure the safety of medical equipment.

 

1. Introduction
    In order to improve the level of medical services, modern medical institutions continue to introduce new and complex advanced medical equipment such as nuclear magnetic resonance, CT machine, X-ray machine, Hemodialysis machine, etc. At the same time, a large number of energy-saving lighting equipment, inverter air conditioners, elevator equipment, etc. put into use. These devices are non-linear devices, and a large number of high-order harmonics will be generated during operation, which will cause certain interference to the power distribution system and medical equipment. At the same time, these advanced medical equipment have high-end computer components and a large number of highly sensitive microelectronic devices. They have high requirements on the power quality of the power supply and are very sensitive to voltage fluctuations and power harmonics. Serious power harmonic problems can lead to medical treatment. The damage of the equipment even leads to the occurrence of medical accidents. 

 

2. Analysis of Harmonic Source, Harmonic Characteristics and Harmonic Harm of the Hospital Building Power Supply System

2.1  Source of harmonics

Main classification Facilities and equipment names
Building facilities Elevator equipment
central air-condition system
Fire water pump
lighting device
Medical Facilities Operating room, laminar flow room system
ICU, delivery room, neonatal care unit, hemodialysis center, etc.
Preparations, samples, blood preservation and freezing facilities
Hospital office automation facilities
Medical diagnostic equipment Main diagnostic equipment, such as spiral CT machine, color Doppler, MRI machine, laparoscope, EEG machine, chromatograph, various functional testing instruments, etc.
Main treatment equipment, such as ventilator, hyperbaric oxygen chamber, various monitors, laser treatment equipment, etc.

 

 

2.2 Harmonic characteristics

Harmonic source load type  Frequency of harmonic current Harmonic current distortion rate
Lighting fixtures, computers, etc 3, 5, 7, 9, etc. (2n+1) times 7~10%
Electronic testing equipment, operating room, gamma knife, etc 3, 5, 7, 9, etc. (2n+1) times 10~15%
CT, magnetic resonance, DSA, etc. 3, 5, 7, 9, etc. (2n+1) times 30~40%
Accelerator, X-ray machine, gastrointestinal machine, etc. 3, 5, 7, 9, etc. (2n+1) times 50~60%
UPS, variable frequency ventilation equipment, elevators, etc. 3, 5, 7, 9, etc. (6n+1) times 25~35%

 

 

2.3  Harmonic hazard analysis
2.3.1 The harm of harmonics to the distribution system
   Make the additional loss of power components increase, easy to cause fire, affect the normal operation of electrical equipment, cause power network resonance, make the relay protection wrong action, electrical measurement error is too large, crash the industrial control system

2.3.2 Hazard of Harmonics to Medical Equipment
 Causes synchronization imbalance and data errors of devices that rely on microprocessor technology, directly endangers the safety of the internal electronic circuits of the device, causing breakdown or discharge, affecting the performance and accuracy of precision medical equipment
 
3.
Grid harmonic standard requirements

3.1 Harmonic current limit

Calculation standard: According to IEEE-519, the harmonic current limit is calculated according to Table 3-1

Table 3-1 IEEE519 harmonic current limit Ih/IL

ISC/IL Ih/IL (%) General power distribution system (120V~69kV) THDi (%)
h<11 11h<17 17h<23 23h<35 h35
<20 4.0 2.0 1.5 0.6 0.3 5
20~50 7.0 3.5 2.5 1.0 0.5 8
50~100 10 4.5 4.0 1.5 0.7 12
100~1000 12 5.5 5.0 2.0 1.0 15
>1000 15 7.0 6.0 2.5 14 20

 

3.2   Voltage quality index limits

The harmonic voltage limit should meet the harmonic voltage index specified in IEC61000-3-6, as shown in Table 3-2:

Table 3-2 MV, HV and EHV harmonic voltage planning level index values (percentage of nominal voltage)

Non-3 times odd harmonics 3 times odd harmonic Even harmonics
Harmonic number Harmonic voltage (% Harmonic number Harmonic voltage (% Harmonic number Harmonic voltage (%
h MV HV-EHV h MV HV-EHV h MV HV-EHV
5 5 2 3 4 2 2 1.6 1.5
7 4 2 9 1.2 1 4 1 1
11 3 1.5 15 0.3 0.3 6 0.5 0.5
13 2.5 1.5 21 0.2 0.2 8 0.4 0.4
17 1.6 1 >21 0.2 0.2 10 0.4 0.4
19 1.2 1       12 0.2 0.2
23 1.2 0.7       >12 0.2 0.2
25 1.2 0.7            
>25 0.2+0.5×(25/h) 0.2+0.5×(25/h)            

Note: Total distortion rate (THD): MV network is 6.5%, HV network is 3%; 110kV is calculated according to HV, and 35 and below is calculated according to MV.

 

4.  Application of STS-APF Low Voltage Active Power Filter in Hospital Building

4.1  Application of active power filter

The newly-built outpatient and inpatient complex of a large tertiary hospital has 4 transformers of 2000kVA and 1 1600kVA, and a diesel generator of 800kW. According to the load rate of the non-linear load equipment of each transformer in the hospital and the corresponding harmonic distortion rate and The simultaneous utilization rate of each non-linear device is used to calculate the magnitude of the harmonic current, and 5 sets of STS-APF active filters with different capacity specifications are configured.

The following takes the comparative analysis of the power quality test of the power distribution system before and after the 1#STS-APF active filter is put into operation as an example. The load of the 1# transformer is mainly lighting, elevator, submersible sewage pump, and computer center etc.

4.1.1 Data before and after the operation of the active power filter
1Before the active filter was put into use, the current waveform distortion was serious. The harmonic content of the three-phase current was 19.7%, 27.8%, and 26.6%, respectively, the three-phase current was 45A, 40A, 64A, and the neutral current was 37A.
2After the input of the active power filter, the current waveform distortion is obviously improved, and the harmonic content of the three-phase current is obviously reduced, which is 2.9%, 2.8%, 3.4%, respectively. The three-phase current is 47A, 48A, 47A, and the neutral line current is 5A.
3The current waveform is improved obviously, and the current waveform is approximately sinusoidal after the use of the filter. The expected goal and effect of harmonic control are achieved.

4.1.2 Data recorded before and after the active power filter is put into operation

4.2 Application significance of active power filter in hospital building
    Protect the safety of medical electrical equipment, purify the power supply, protect the power factor compensation equipment, prevent the malfunction of the protection device, reduce the power loss, and expand the power supply capacity of transformers and generators.

 
4.3 Main technical specification of active filter.

Wiring Three-phase three-wire or three-phase four-wire
Access to the voltage 3×380V ±10%
Access frequency 50Hz ±2%
Dynamic compensating response time Dynamic response < 4ms, full response time < 20ms;
switching frequency 10kHz
Function setting Compensate only harmonics, only reactive power, both harmonics and reactive power; manual and automatic switching.
Harmonic compensation times 2-21 times
Type of protection DC overvoltage, IGBT overcurrent, device temperature protection
Overload protection Automatic current limit at the set value, no overload
cooling method Smart air cooling
noise  65db (In the cabinet and operating in rated state)
Working temperature -10℃~+45
Working environment humidity 85%RH  Non-condensing
installations Indoor installations
The altitude 1000m (Capacity reduction is required for higher altitude)
Inlet and outlet mode Bottom in and bottom out
Protection level IP21
Intelligent communication interface RS485/MODBUS-RTU
Remote monitoring Optional
Dimensions (mm)
(W×D×H)
30A 50A 75A 100A
600×500×1500 600×500×1500 600×500×1800 800×600×2200
Weight (kg) Three-phase four-wire Three-phase three-wire
30A50A 75A100A 30A50A 75A100A
280 360 240 290

 

 

4.4  Active filter component list

Main products list:
No. Name Model Qty.
1 APF electrical cabinet 800X600X2200 1
2 Current transformer APFCOV-CVT100 1
3 The controller APFMC-C100 1
4 reactor APF-RE.(S)DG-100 1
5 Active current transformer LT208-S7 3
6 filter STS-WF001 2
7 The circuit breaker CVS160FTM160D4P3D 1
8 contactor LC1D150M7C 1
9 Microcircuit breaker NDM1-63C32 1
10 Intermediate relay MY4NAC 2
11 R-type transformer R320-0.38/0.22 1
12 Harmonic detector ACR350EGH 1
13 electric wire 16mm2 A number of
14 electric wire 4mm2 A number of

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.  Conclusion
   This article analyzes the harmonic sources, harmonic characteristics and hazards of hospital buildings, and compares and analyzes the situation before and after the active filter is put into use through the application case of the active filter in the low-voltage power distribution system of a large hospital. The harmonic control technology of the filter is one of the effective means to improve the quality of power supply. It can control the generated harmonics to a minimum range, achieve scientific and reasonable power use, suppress grid pollution, improve power quality, and ensure the safety of medical equipment.