This page contains a Flash digital edition of a book.

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

Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92