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ELECTRICAL SAFETY


The result is safer, and more efficient, hospitals, and in turn cost savings.


How we do it in Finland In Finland, the operating theatre’s electrical power network is separated from the electrical grid by a medical isolation transformer (IT system). The circuit feeding into the electronic device is insulated from the feeder network, and its secondary circuit is not earthed. The isolation transformers ensure a constant supply of power, and filter out any disruptions to the main grid. The leakage current is minimal, and the first short circuit that occurs does not cause an outage. In other words, the isolation transformers provide the necessary protection, while the insulation-level monitoring system indicates any faults and sounds the alarm.


An insulation monitoring relay measures leakage current from a floating isolated AC (alternating current) system to earth. The system uses pulse measurement, and is therefore compatible with both DC (direct current) and AC voltage networks. Pulse measurement also works well with modern switched-mode power supplies, and indicates capacitive faults. An insulation monitoring relay also monitors measurement wires and transformer load/temperature. Different addressable modules can be added to the system, and they communicate with the main unit via an RS-485 serial communication bus, which makes cabling simple.


Remote control module A remote-control module indicates insulation and PE (protective earth grounding) wire alarms, and a transformer monitor module indicates transformer overload and over-temperature in the operating theatre via light and sound. These modules are mandatory (European Standard EN 55022, Class B regarding medical locations, international standards IEC 60364-7-710: 2012 and IEC 61557-8 insulation monitoring device for IT systems, Finnish standard SFS6000-7- 710). There is also a system panel module that combines both remote control and transformer monitor modules with an integrated LCD screen, which can be used to view alarm logs and fault indications in text format.


Alternatively, the system can be expanded with a module to monitor PE (protective earth grounding) continuity. The module will separately monitor every fuse line, and if there is an interruption in the protective earth (loose or damaged wire/contact), the maintenance team will be instantly notified. The module will also immediately indicate which fuse line is the faulty one. For the maintenance team, there is also a fault locator module, which will locate the fuse line with the insulation


70 Health Estate Journal September 2020


A transformer room in a Finnish hospital.


fault. In a fail situation, the system will communicate with the automation centre via relay contacts, which will inform the maintenance team of the fault. Early detection of a fault might prevent further degradation of the device. In the worst case, a faulty unit in open surgery may cause a deadly electric shock.


Guidelines on the alarm system Personnel are provided with guidelines on how the alarm system related to the insulation-level monitoring operates in the room; these are also displayed on the wall of the operating room for everyone to see. If the system in the theatre sounds the alarm, the personnel unplug the faulty electronic device from the socket and acknowledge the alarm with the ‘Acknowledge’ button. In the meantime, the technical staff are notified of the alarm.


All medical devices used in G2 facilities must be connected to a network insulated by isolation transformers. A separate socket may be available for cleaning and maintenance work, for example, in the operating room. The socket must be directly connected to the national grid, not to the insulated network. Medical devices must not be plugged into this socket, and it must be used for its assigned purpose only, excluding any patient treatment. The socket must be clearly equipped with a sign stipulating ‘Not for medical devices’, or ‘Maintenance socket’.


A thorough commissioning inspection


must always be completed prior to the deployment of an insulation-level monitoring system. The inspection must be conducted in both new premises and those under renovation. The commissioning inspection can only be conducted by a qualified electrician. It is recommended that the inspection be conducted by an IT system equipment supplier with in-depth knowledge of the system and related requirements.


Example of a ‘fail’ scenario Let us now move on to look at how the insulation monitoring system works in practice. In the operating theatre, a staff member connects the faulty device, which has an insulation fault in the socket. An insulation monitoring relay measures leakage current from a floating isolated AC system to earth, detects the isolation fault, and notifies the hospital automation centre by relay, which then informs the maintenance team of the failure. An alarm is also emitted locally in the operating theatre by a remote control module with light and sound. In the theatre itself, the staff disconnect the device that was last connected after the alarm. After the failed device is removed, the system automatically resets the alarm. The operating theatre staff then replace the failed device with a spare one, and the operation can continue with just a short delay. The faulty unit is removed and delivered to the hospital’s Maintenance team, who are also notified as to which unit has been emitting the alarm via an


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