Xu Shuang Ankerui Electric Co., Ltd., Shanghai 201801 In the operating room of a hospital, when an operation is performed on a patient, it is sometimes necessary to use an electronic medical device to penetrate inside the patient's body. Since the patient is in an anesthesia state, a slight electric current flows between ordinary grounded conductors to cause a micro-shock. Failure to take appropriate measures may endanger the safety of the patient and cause medical accidents. At present, most of the distribution systems of large-scale general hospitals in China use TN systems for grounding. The system ground faults are mostly metallic short circuits. Due to the large fault current, the circuit breaker and other over-current protection devices are operated, resulting in power outages. Obviously, the TN system cannot meet the requirements for uninterrupted power supply in some important sites in the hospital. “Section 14.7.6.3 of the Civil Building Electrical Design Specification†clearly states that power supply system ungrounded (IT system) power supply methods shall be used in places where major medical hazards occur after sudden power interruption. At the same time, the “Technical Specification for Hospital Clean Surgery Department†GB50333-2002 stipulates that: Class 2 medical sites should maintain the life of patients, and surgical operations and other electrical devices located around the patient should adopt medical IT systems. Such as: rescue room (outpatient operating room), operating room, cardiac monitoring and treatment room, catheter intervention room, blood photography examination room and so on. 1. Composition of medical insulation monitoring products 1.1 The IT system shall be powered by a dedicated AITR series medical isolation transformer. The national standard requires equipment: 1) Medical IT systems usually use single-phase transformers, whose rated capacity should not be less than 0.5 kVA and no more than 10 kVA. 2) The isolation transformer should be as close as possible to the medical site and take measures to prevent unintentional contact by people. 3) The rated voltage on the secondary side of the isolation transformer shall not exceed 250V. 4) When the isolation transformer is at rated voltage and rated frequency, leakage current flowing to the enclosure or earth shall not exceed 0.5 mA when operating at no load. 5) For Type 2 medical facilities, the distribution system shall be provided with overcurrent protection. It is forbidden to use overload protection on the primary side and secondary side of the isolation transformer. Secondary circuit breakers should be installed on the secondary side. 6) In Class 2 medical establishments, each outlet circuit of the IT system shall be independently provided with overcurrent protection, and overload alarms shall be set independently. 1.2 Medical smart insulation monitor should meet IEC61557-8 and meet the following requirements 1) The AC internal impedance of the medical insulation monitor should be at least 100KΩ. 2) The measurement voltage should not exceed 25V DC. 3) The peak value of the injected current should not be greater than 1 mA even in the event of a fault. 4) At the latest when the insulation resistance drops to 50KΩ, a signal should be given. Should be configured to test this functional apparatus. 1.3 Monitor the winding temperature and load current of the isolation transformer in IT systems. 1.4 external alarm and display instrument. Installed in the workplace of the patient or medical worker. It is used to display the measurement data and alarm conditions of the monitoring instruments in the medical place, and informs the use of the IT system about the operation of the system. It can display all the information of the insulation monitor. It can also connect multiple external alarm displays and test units in parallel. 1.5 Test signal generator. When the insulation monitor detects insulation failure in the system, it will activate the insulation fault location signal of the test signal generator product, and cooperate with the insulation fault locator to locate the circuit with insulation failure. 1.6 Insulation fault locator. With the test signal generator, in the event of an insulation fault in the system, the faulty circuit is quickly located to facilitate the maintenance of the operation and maintenance personnel. Acrel medical insulation monitoring products include: AITR series isolation transformers, AIM series medical intelligent insulation monitors, AID series of external alarm indicators, AIL series fault locator, ASG signal generators and other equipment. 2. The necessity of selecting IT systems in the medical field 2.1 The IT system has reduced the risk of electrical shock to a minimum by reducing the contact voltage and ground leakage current (effectively controlling the direct leakage current to the heart). As we all know, when the direct leakage of electrical equipment to the human heart is greater than 10μA, it will cause a micro-shock accident to the patient. The RCD and other ground leakage protection switches used in general general buildings do not meet the needs of the medical field because their operation response value is mA level (eg 30mA). Therefore, nowadays in the medical field, important places such as operating rooms, ICUs, and CCUs are usually powered by local “neutral point ungrounded power supply systems†(ie, IT systems). To supply power to these sites through a single-phase 0.5kVA-10kVA isolation transformer, it is possible to prevent leakage currents in other power supply circuits from entering the operating room, ICU, and CCU's medical electrical equipment and pose a threat to the patient's safety. Once the load (such as various medical electrical equipments) connected to the isolated power supply has a ground fault, the loop cannot be formed, and only a small capacitive leakage current can be generated, which greatly protects the patient from leakage current. hurt. 2.2 When there is an insulation failure point in the grid load, it will not cause the circuit breaker or the fuse to act, thus ensuring the reliability of the power supply; In the medical field, some places have high requirements for the continuity of the power supply, so it is designed to be two ways. (Even three-way) power supply (grounded power supply system) is automatically switched to ensure the continuity of power supply in these special places. However, if there is a relative insulation failure at the load side, the fault current will form a loop through the neutral point of the power supply to the ground, thus forming a large fault current and allowing the upper open air or fuse to operate. Eventually lead to power interruption. If local IT distribution systems are used in these special locations, because the neutral point of the power supply is not grounded, when the first point of the load is relatively insulated, it will not be able to form a loop due to its ground. It will only produce a small The capacitive leakage current will not cause harm to the human body, and it will not cause the air-opening action at the same time, thus ensuring the connectivity of the operating room power supply. The insulation monitor in the IT system monitors the phase-to-ground insulation resistance. Once the phase-to-ground insulation fault occurs, the insulation monitor immediately warns the operator of the first ground fault in the system, but the system can still bring Failure to operate requires an appropriate amount of time to identify and eliminate. If the insulation monitor is not installed in the IT system, when the first failure occurs, the operator will not get any alarm information. If the second and third failures occur again, the gradually increasing fault current will eventually lead to the inside of the system. Miniature circuit breakers or fuses act to de-energize the entire IT system. If two faults occur in different phases, the same short circuit will be formed to the ground, causing great harm to the IT power system and causing life-threatening hazards to the patient. 2.3 Reduced ground leakage current and improved fire safety. 3 Major Products and Applications The medical isolation power solution of Ankerui Electric Co., Ltd. is designed and developed for the power supply needs of medical Class II sites, and it can well meet the requirements of various operating rooms and intensive care units for power safety and reliability. And in line with national standards. 3.1 ICU and CCU Ward Distribution Solutions (Example of GGF-I8G Isolation Distribution Cabinet System Diagram) Scheme configuration table 3.2 Operating Room Power Distribution Solution (using the GGF-O8G Isolation Distribution Cabinet system diagram as an example) 4 Quotations for main products and power cabinets In order to facilitate our customers' choice of Acryle products, we now list product quotation, as shown in the following table: 4.1 GGF-I Series ICU/CCU Ward Isolation Power Cabinet shape model specification unit Price (ten thousand yuan) GGF-I3.15 3.15KVA set 3.8~5.3* GGF-I6.3 6.3KVA set 4.4~5.9* GGF-I8 8KVA set 5~7* GGF-I10 10KVA set 6.8~9.8* ups Optional, additional price Dual power switching device Optional, additional price Freight Reference logistics company quote Note The above quotation includes commissioning fees, excluding freight and installation fees 4.2 GGF-O Series Operating Room Isolated Power Supply Cabinet shape model specification unit Price (ten thousand yuan) GGF-O6.3 6.3KVA set 6.4~7.9 GGF-O8 8KVA set 7~9 GGF-O10 10KVA set 8.6~11.6 ups Optional, additional price Dual power switching device Optional, additional price Freight Reference logistics company quote Note The above quotation includes commissioning fees, excluding freight and installation fees 4.3 Medical IT Insulation Monitoring Products shape name model Features price Optional and price (yuan) Insulation monitor AIM-M100 IT system ground insulation resistance, load current, transformer temperature monitoring 15600 AIM-M200 19600 DC power supply ACLP10-24 Instrument dedicated power supply 300 / Alarm and display AID100 Insulation resistance, transformer load rate; remotely set the insulation monitor alarm threshold / AID120 / AID200 Using CAN communication, can remotely display and set the parameters of up to 16 sets of insulation monitoring system, real-time monitoring whether the communication is in good condition 900 / Current Transformer AKH0.66-P26 Real-time measurement of transformer load current 150 / Test signal generator ASG100 Using CAN bus technology, data exchange with other devices can occur. When an insulation fault occurs in the system, a fault location signal can be injected into the system to achieve L1, L2 disconnection detection. 3780 / Fault location (evaluation) instrument AIL100-4 Adopt CAN bus technology, when the insulation fault occurs in the system, it can cooperate with ASG100 to realize fault location function 6050 / AIL100-8 8050 / 5 Issues to Consider When Applying IT Systems 1. Isolation transformer setting position of IT system. The location where the isolation transformer is to be placed should be close to the ventilated and easily dissipated area of ​​the operating room, and the distance between the outlet end of the transformer and the socket of the operating room should be as short as possible. Isolation transformers are usually placed in the operating room wall with built-in electrical cabinets, operating room ceilings or surgical preparation rooms with vertical electrical cabinets. 2. Use three-phase isolated power supplies with caution in the second-class locations. If a single-phase earth fault occurs in the three-phase isolation system (IT system), the voltage of the non-faulted earth will increase by 1.7 times of the rated voltage of the earth, and thus there is a danger of the earth fault extending. Therefore, the three-phase isolated power supply should be used with caution. Use a single-phase isolated power system as much as possible. 3. The distribution system of the IT system shall be equipped with two-stage switches as short-circuit protection. Because the IT system should not be equipped with a neutral (N) line, the 220V power required by the single-phase load in the system is provided by the single-phase 220V power supply in the IT system via the secondary side of the 1:1 isolation transformer. Therefore, the distribution lines in the IT system are all live wires, and two-stage switches should be installed as short-circuit protection. references: [1] Application of IT System in Hospitals. Building Technology 2006 No.13 [2] Ankerui Electric Co., Ltd. Product Selection Manual 2013.1. About the Author: Xu Shuang, female, undergraduate, Ankerui Electric Co., Ltd., the main research direction for the smart grid power distribution, Email: Mobile QQ
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