Discuss the design of centralized monitoring system in the application of medical IT system, the combination of UPS and medical IT system, the selection of circuit breakers for IT systems, and the installation of medical isolation power cabinets in different medical places, emphasizing the design of medical IT systems. And construction should be standardized and standardized.
Gu Fanghong (Jiangyin City Architectural Design and Research Institute Co., Ltd., Jiangyin City, Jiangsu Province, 214401)
Xu Jun (Ankerui Electric Co., Ltd., Shanghai, 201801)
In recent years, with the deepening of people's understanding of IT systems, the design and application of IT systems are becoming more and more extensive. Among them, medical isolated power systems are typical applications of IT systems in medical facilities . Due to the special nature of its functions, hospitals also have special requirements for their distribution methods. Such as hospital surgical equipment, equipment for maintaining the life of patients, etc., in order to ensure the continuity and reliability of power supply, to ensure the safety of equipment users and patients, should use IT system power supply, supplemented by high-demand local Equipotential bonding .
In response to the design and application of IT systems in medical facilities, many domestic electrical experts and colleagues have published articles and provided invaluable advice and experience. The design of the medical IT system has different characteristics from the IT system design of other places, and the insulation monitoring device used also has special requirements. Based on the actual engineering experience, the author puts forward his own opinions on several related issues in the application of medical IT systems. I hope that experts in the industry will not hesitate to deepen the research and discussion on the application of medical IT systems.
1 Centralized monitoring system setting for medical IT system insulation monitoring
In medical IT systems, the device used to monitor the system's operating status in real time and alarm in time when the system fails is an Insulation Monitor (IMD). In addition, an external alarm and display device should be set up. External display device). GB 16895.24-2005/IEC 60364-7-710:2002 "Electrical installations of buildings - Part 7-710: Requirements for medical devices for special installations or establishments". Requirements in 710.413.1.5: Each medical IT system, equipped with A device with an audible and visual alarm system that should be installed in a suitable location so that medical personnel can monitor it frequently. At present, most of the external display devices with communication functions are used. The device reads the monitoring data of the insulation monitor in real time through communication. When the insulation monitor detects the system failure, the device emits an audible and visual alarm signal. The sound signal can be released, but the light signal must be extinguished after the fault is cleared and returned to normal. When purifying the decoration in a medical class 2, the external display device used for monitoring the IT system of the surgical room is usually installed on the intelligence panel of the operating room, or the wall is installed next to the intelligence panel. The external display device used for monitoring various indoor ICU (CCU) indoor IT systems is usually installed in the nurse station and monitored by nurses.
In practical applications, the medical IT system of all medical categories can be centrally monitored through the centralized monitoring system of the upper computer. The isolated power centralized monitoring system topology diagram includes a monitoring layer, a communication layer, and a device layer. The monitoring layer includes a monitoring host and a printing device, the communication layer includes a communication gateway and a communication line, and the device layer includes all isolated power devices and monitoring instruments applied to each medical site. Since the monitoring system adopts the upper computer platform, it can display richer monitoring information and realize more monitoring functions through software. These information and functions mainly include power distribution one-time map and on-site distribution map, operation parameter monitoring of each medical IT system, and remote control. Parameter setting, fault sound and light alarm and recording, and curve display of monitoring data of each IT system. Figure 1 is a graph showing the monitoring of the insulation resistance of the IT system to ground conducted by the monitoring system. The curve clearly shows the change of the insulation resistance of the IT system to the ground. According to the downward trend, the cause of the system insulation decline can be analyzed and found, and measures can be taken to eliminate the hidden troubles in advance, thus effectively ensuring the safe and reliable operation of the system.
Figure 1 IT system grounding resistance resistance monitoring curve
The above analysis shows that the centralized monitoring system of the upper computer is used to monitor each IT system, and the external display device with simple function is installed on the site for monitoring, which has better monitoring and prevention effects. This centralized monitoring system can be set up in the duty room of the hospital's electrical operation and maintenance personnel, or integrated into other power monitoring systems, and monitored by professional electricians. Once an IT system fails, electrical maintenance personnel can also Make judgments in the first time and deal with them according to the situation on the spot. In contrast, the external display device installed on the site is monitored by non-electrical professional hospital personnel. When the fault is alarmed, it is difficult for the hospital personnel to identify the cause of the alarm, and it is impossible to judge whether the work can be continued according to the fault condition. In many cases, electrical maintenance personnel may not be notified in a timely manner. If there is an insulation fault and it cannot be eliminated in time, if a second fault occurs, it will be converted into a short circuit between the live conductors and the overcurrent trip will stop, resulting in serious consequences.
The author believes that considering the human being, for the IT system of important medical 2 types of places, in addition to the on-site monitoring of the external display device, the centralized monitoring system of the upper computer can be used, and the centralized monitoring by professional electricians can be more effective. Ensure the reliable operation of IT systems.
2 UPS and medical IT system combined application
JGJ312-2013 "Electrical Building Electrical Design Code" Article 4.4.6 stipulates: "The load that is required to interrupt the power supply time less than or equal to 0.5s is particularly important, and an uninterruptible power supply unit (UPS) shall be provided, and Online." For critical loads that use medical IT systems, an uninterruptible power supply unit should be configured. Some of the existing design methods are to set the UPS in front of the isolation transformer, and the UPS with three-phase input three-phase output is concentrated to supply power to multiple IT systems; some UPSs that use single-phase input and single-phase output supply power to one IT system. . Specifically pointed out here, the UPS of single-phase input single-phase output can be directly connected to the secondary side of the isolation transformer. At this time, the input and output ends of the UPS adopt ungrounded wiring, that is, IT system. It has been stated in the literature  that the load side system of the UPS is not an extension of the power supply side system, but another system that is restarted, and the output of the UPS is the starting point of this alternative system. The UPS is placed directly on the secondary side of the isolation transformer, and the output is terminated by an ungrounded IT system. Compared with the front of the isolation transformer, one layer is reduced and the power supply reliability is higher. From the selection of the rated output power of the UPS, the UPS is used. Since the maximum power requirement of the isolation transformer during transient startup is not considered, the rated output power of the UPS can be reduced, the equipment cost can be reduced, and the economy of the system can be improved.
For the design of the UPS capacity of the medical IT system configuration, the traditional method is determined according to the designed load power and considering a certain margin at the same time, usually multiplied by the coefficient of 1.2~1.5 based on the total load power. For UPSs that are individually configured for the operating room or intensive care unit, this design ensures the reliability of uninterrupted power supply. For UPSs that are distributed to multiple operating rooms, since not all operating rooms are in use at the same time, adopting this method to design UPS capacity will result in a â€œbig horse carâ€ situation, so that UPS When it is put into use, it is always in a low load rate, low efficiency, and high energy consumption. The efficiency of the UPS is proportional to the load ratio (the ratio of the actual output power of the UPS to the rated output power). The closer the rated output power of the UPS is to the actual load power consumption, the higher the efficiency. Generally, the load rate should be controlled at 40%~ Between 80%. Therefore, for the design of the capacity of the UPS in the operating room, in addition to considering the reliability, it should also be combined with the ratio of all operating rooms simultaneously, multiplied by a factor of 0.5 to 1, so as to overcome the UPS power reserve as much as possible. Defects with high energy consumption and poor economy.
3 Medical IT system breaker selection
GB 16895.24-2005/IEC 60364-7-710:2002 Section 710.53.1 Protection of lines in Class 2 medical facilities: "Short-circuit protection and overload protection are required for each terminal circuit, but medical IT systems The transformer's inlet and outlet circuits are not allowed to be installed with overload protection, but fuses can be used for short-circuit protection." The load that is distributed by the medical IT system is mostly important equipment for surgery or maintenance of the patient's life. These devices are not allowed to be powered off during use, and the overload protection of the circuit breaker is not allowed even under overload operation. Single-magnetic circuit breakers can be selected. These circuit breakers are only short-circuit protected, have no overload protection function, and are short-circuited by electromagnetic force, which is a kind of magnetic protection. According to the author's understanding, due to the limited use of single-magnetic circuit breakers, only a few companies are currently producing, and the price is more expensive than ordinary circuit breakers. Therefore, most electrical designers still use the medical IT system power distribution design. Circuit breaker with overload protection. This design should fully ensure that the protected circuit can not be overloaded, otherwise the circuit breaker may be overloaded and disconnected, resulting in serious medical accidents.
In addition, since any isolation transformer will generate an inrush current (ie, inrush current) when it is engaged. Medical isolation transformers from different manufacturers have inconsistent inrush current values, usually several times the peak value of the rated input current. GB 19212.16-2005 "Safety of power transformers, power supply units and similar products Part 16: Particular requirements for isolating transformers for power supply in medical applications" Clause 13.3: "Inrush current shall not exceed 12 times the peak value of rated input current ...". Therefore, when selecting the rated current of the circuit breaker at the input end of the isolation transformer, the influence of the inrush current when the isolation transformer is engaged should be fully considered. If the inrush current is too large, the trip unit of the selected circuit breaker cannot be tolerated, which may result in the inability to close. Or a certain fit, but in operation, there may be a loss of power from the working power supply, and the safe power supply is switched. When the power angle of the power supply voltage is the most unfavorable, the excessive current may cause the circuit breaker to open, causing the operation to be interrupted. The medical device is not working properly. Therefore, the circuit breaker at the input end of the isolation transformer should adopt a single-magnetic circuit breaker that matches the rated input current of the transformer. If a circuit breaker with overload protection is selected, in addition to the sufficient current for the rated current, it should be selected. It complies with GB14048.2-2008 "Low-voltage switchgear and control equipment Part 2: Circuit breaker", and the tripping curve is C and D-type circuit breaker.
4 Medical isolation power cabinet installation
In the operating room or ICU (CCU) power distribution design, the current method is mostly to assemble the medical IT system and related distribution circuit breaker into a power distribution cabinet, called an isolated power cabinet. In addition to the IT system, the operating room is equipped with a TN system for powering non-surgical equipment such as viewing lights, writing desk lamps, and electric doors. Isolation power cabinets for all types of intensive care units are usually only available in IT systems to power the care towers next to the wards in the intensive care unit.
Medical isolated power cabinets are distributed equipment and should be installed in non-clean areas. The isolated power supply cabinet for the operating room is usually embedded in the side wall of the operating room, that is, the wall decoration interlayer between the operating room and the cleaning corridor, but it cannot be installed in the operating room or in the clean corridor. For the ICU (CCU) room, the situation is relatively complicated. For larger ICU centers, there are more beds and more isolated power cabinets are required, which means that there is a large installation space near the site. In some new hospital projects, the design of medical IT systems is designed by the design institute's electrical designers. The electrical designers will set up a power distribution room near the ICU (CCU) center to centrally install the isolated power cabinets according to the design requirements. However, in some projects, electrical designers only design the distribution box to the floor. The power distribution of the ICU (CCU) is designed by a professional purification company, so the electrical designer will not propose according to the power distribution requirements of the ICU (CCU) room. Set the setup requirements for the power distribution room. When the purification company is purifying the design, the functional partition of the space is often clear and cannot be adjusted, resulting in no suitable space for the isolated power cabinet. In some projects, the isolated power cabinet is installed in a power distribution room far from the center of the ICU (CCU), resulting in a long distribution line, which affects the security of the IT system. Some installations are installed in the nearest distribution box, and the isolation transformer ceiling is installed inside the ceiling. This treatment method is not convenient for the installation maintenance, ventilation and heat dissipation of the isolation transformer, and there are hidden dangers to the stable operation of the IT system. Therefore, for the ICU (CCU) center, regardless of whether the electrical designer is doing the distribution design of the medical IT, the space requirements for the installation of the isolated power cabinet should be proposed.
The application of medical IT systems has been clearly required in China's national standard, but the design and construction status of medical IT systems are uneven. Some designs only consider economic costs but neglect safety, reliability and national standards. The intention of adopting an IT system is opposite. Once a power distribution equipment fails, it is likely to cause a major medical accident. Therefore, the author also urges peers to seriously study the application of medical IT systems and form a relatively uniform and standard design and construction method to better guarantee the reliability and safety of distribution in medical 2 types of places. Limited to the level, the author must have a lot of fallacies, but also be willing to ask the peers to criticize and correct.
Source: Building Electrical, 2015, issue 12.
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