There are several reasons why electrical safety and reliability is of uttermost importance for medical facilities.These include among others:
- Electromagnetic Compatibility: The high density of electric and electronic equipment in medical premises involves a risk on electromagnetic disturbances between the electricity supply and medical devices.
- Criticality of continuity: Many medical treatments cannot be interrupted even for a moment without entailing risk for patient and on occasion, life-threatening risk.
- Data integrity: Accurate medical data is essential and are often gathered by long-term or invasive patient examination.
- Leakage currents: Currents leaking from various devices may be individually safe but combined with others can add up quickly and exceed the safe level.
- Weak or sensitive patients: Some patients have weakened or non-existing reflexes in the event of direct contact with live electrical parts. Other patients may have reduced skin resistance because of stress, sweating, or catheters/electrodes introduced on or into the body.
ENSURING SAFETY: STANDARD IEC 60364-7-710
All low voltage electrical installations must comply with IEC 60364, the general international standard for electrical safety. In particular, Section 710 of this standard is dedicated to medical locations and prescribe certain additional requirements for such locations. It is included in the seventh part of IEC 60364, hence the code IEC 60364-7-710. Most national regulations on electrical safety in medical facilities are derived from IEC 60364-7-710. It applies to hospitals, medical clinics (including the self-contained type), medical and dental surgical facilities, dedicated rooms in nursing homes where patients are given medical treatment, rooms for physiotherapy, beauty centers, ambulatory and emergency aid units in industrial or sport facilities and veterinary surgeries. It is primarily a safety standard, as well as providing some rules on ensuring availability.
Standard IEC 60364-7-710 categorizes all medical rooms into three groups, based primarily upon the use of applied parts. An applied part is any part of an electro-medical device that might come into contact with a patient. Each group has a dedicated set of protective measures.
Group 1 includes all rooms where the loss of power supply may endanger the patient’s life. It also includes all medical locations in which applied parts are used for intra-cardiac procedures (risk of micro-shock to cardiac muscles). Finally, it includes all rooms related to operations involving general anesthesia: pre-operation rooms, operating theaters, surgical plaster rooms, and post-operative recovery rooms.
The measures for Group 1 include:
- Protection against direct contact through proper insulation
- No power interruption is allowed (for medical equipment nor for support services such as lighting)
- An IT earthing system to protect against earth faults (avoiding power interruptions)
Group 2 includes all medical locations that do not belong to Group 2 and where applied parts are used,
externally or invasively. Examples are rooms serving for physiotherapy or hydrotherapy, and dental surgery.
The measures for Group 2 include:
- Protection against direct contact through proper insulation
- In case of a power interruption, crucial support services such as lighting should switch to an alternative power supply
- A TNS earthing system is permitted
Group 3 includes all medical locations where no applied parts are used, such as outpatient rooms, massage rooms without electro-medical devices, offices, store rooms, canteens, changing rooms, corridors, staff hygiene facilities, waiting rooms, et cetera. No extra measures have to be taken for Group 3 other than those general prescriptions for electrical safety in buildings (Standard IEC 60364). Nevertheless, a high level of electrical reliability and safety should be maintained. This means that power quality disturbances (e.g. harmonic distortion, stray currents, et cetera), electric faults, and equipment damage (e.g. neutral conductor interruption, insulation degradation, et cetera) should be avoided. If a TN or TT earthing system is being used, it is advisable to continuously monitor the insulation quality by a Residual Current Monitor (RCM). This device should not be confused with a Residual Current Device (RCD). The RCM monitor can never disconnect the circuit, but rather continuously monitors the differential current value and sends alarm signals if thresholds are exceeded. This enables taking predictive measures and avoiding unexpected failures. Such monitoring can also
be a first step in improving the energy efficiency of the system.
Qualified medical personnel must carry out the assignment of the rooms to one of these three groups. If no such personnel are available, the national healthcare organization must be called in.
The function of a particular room is often changed during the lifetime of a hospital; for instance because of changed needs. It can therefore be wise to equip certain rooms for a higher group classification than their initial use demands. Those rooms will then be upgradable without significant costs for the electrical installation.
Source: European Cu Institute
