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! Electric and magnetic interferences, e.g. from the power system, may expose patients to hazards or may influence the function of medical electrical devices.
! Surgeries cannot be interrupted or repeated.
! Intensive care requires simultaneous application of several medical electrical devices.
! Permitted leakage currents may add to critical values.
! Long term recordings of patient data get lost in case of power failures.
! IEC 60364-7-710 apply to electrical installations in medical locations so as to ensure safety of patients and medical staff.
!NOTE 1 It may be necessary to modify the existing electrical installationwhen a change of utilization of the location occurs. Special care should be taken where intracardiac procedures areperformed in existing installations.
!Classification of a medical location shall be made in agreement with ! the medical staff! health organization concerned or ! body responsible for the safety of workers in accordance with
national regulations.
! It is necessary that the medical staff indicate which medical procedureswill take place within the location. Based on the intended use, the appropriate classification for the location shall be determined.
! NOTE 1 Classification of a medical location should be related to the type of contactbetween applied parts and the patient, as well as the purpose for which the location is used.
! Protective measures ! Double insulation! Safety extra-low voltage SELV! Functional extra-low voltage PELV, FELV! RCD in TN-S systems! IT system with insulation monitoring
! Supplementary protection! by equipotential bonding
Which power supply system is required by theIEC 60364-4-410 standard ?
1st letter: earthing of the current source
T = direct earthing one point of the current source
I = isolation of all active parts from earth
2nd letter: earthing conditions of the body of the electrical installation
T = the exposed conductive parts are earthed, independently of the earthing of any point of the current source which might exist
N =the exposed conductive parts are directly connected with the earthing point of the current source in AC systems, the earthed point is generally the neutral point
The TN-S system in medical locations (710.413.1.3)
! In final circuits of group 1 rated up to 32 A, RCDs ≤ 30 mA shall beused (additional protection).
!Care shall be taken to ensure that simultaneous use of many items of such equipment connected to the same circuit cannot cause unwanted tripping of the residual current protective device (RCD).
! In medical locations of group 1 and group 2, where RCDs are required, only type A or type B shall be selected, depending on the possiblefault-current arising.
!NOTE: It is recommended that TN-S systems are monitored to ensure the insulation level of all live conductors.
! Transformers shall be ! installed in close proximity to, inside or outside, the medical location ! placed in cabinets or enclosures to prevent unintentional contact with live
parts.
! Rated voltage Un on the secondary side of transformers ≤ 250 VAC
! Transformers according IEC 61558-2-15, with additional requirements:
! The leakage current of the output winding to earth and the leakagecurrent of the enclosure, when measured in no-load condition and the transformer supplied at rated voltage and rated frequency, ≤ 0.5 mA.
! Rated output of the transformers 0.5 kVA … 10 kVA.! For three-phase loads with an IT system a separate three-phase
transformer shall be provided for this purpose with output line-to-line voltage not exceeding 250 V.
The insulation monitoring device (IMD) (710.413.1.5)
! For each group of rooms serving the same function, at least oneseparate medical IT system is necessary.
! The medical IT system shall be equipped with an insulationmonitoring device in accordance with IEC 61557-8 with the followingspecific requirements:
! a.c. internal impedance > 100 kOhm! the test voltage ≤ 25 V d.c.! injected current ≤ 1 mA peak, even under fault conditions! indication when insulation resistance ≤ 50kOhm! a test device shall be provided
! Overload and overcurrent protection is not allowed upstream and downstream in the feeder circuit of the medical IT system transformer (risk: unexpectedtripping)
! Fuses may be used for short circuit protection
! Monitoring of overload and high temperature for the medical IT transformer is required
! Socket outlet circuits in group 2 rooms:at each patient‘s place of treatment!Min. two separate circuits or! each socket- outlet shall be protected individually
against overcurrent
Protection of the IT system (710.413.1.5, 710.53.1, 710.55.3)
Remote alarm indications in rooms of group 2 (710.413.1.5)
! For each medical IT system, an acoustic and visual alarm systemshall be arranged at a suitable placeso that it can be permanently monitored by the medical staff:
! A green signal lamp to indicate normal operation! A yellow signal lamp which lights when the minimum value set for the
insulation resistance is reached. It shall not be possible for this light to be cancelled or disconnected
! An audible alarm which sounds when the minimum value set for the insulation resistance is reached. This audible alarm may be silenced.
! The yellow signal shall go out on removal of the fault and when thenormal condition is restored
! Note: Additionally overload and overtemperature of the IT system transformer must be indicated.
! In each medical location of group 1 and group 2, supplementaryequipotential bonding conductors shall be installed and connected to the equipotential bonding bus bar for the purpose of equalizingpotential differences between the following parts, located in the"patient environment":
! protective conductors! extraneous-conductive-parts! screening against electrical interference fields, if installed! connection to conductive floor grids, if installed!metal screen of the isolating transformer, if any
!At each patient’s place of treatment, e.g. bedheads, the configurationof socket-outlets shall be as follows:
! either a minimum of two separate circuits feeding socket-outlets shall be installed or
! each socket-outlet shall be individually protected againstovercurrent.
!Where circuits are supplied from other systems (TN-S systems) in the same medical location, socket-outlets connected to the medical IT system shall either:
! be of such construction that prevents their use in other systems or! be clearly and permanently marked.
! In medical locations the distribution system should be designedand installed to facilitate the automatic change-over from the main distribution network to the electrical safety source feeding essential loads
! AV = Normal power supply source! SV = Safety power supply source! HV = Main distribution board
Safety services power supply sources (710.556.5.2)
!General requirements for safety power supply sources of group 1 and group 2
! In medical locations, a power supply for safety services isrequired which, in case of a failure of the normal power supplysource, shall be energized to feed the equipment stated in 710.556.5.2.2.1, 710.556.5.2.2.2 and 710.556.5.2.2.3 withelectrical energy for a defined period of time and within a pre-determined changeover period.
! If the voltage at the main distribution board drops in one orseveral line conductors by more than 10 % of the nominal voltage, a safety power supply source shall assume the supplyautomatically.
! Equipment which is required for the maintenance of hospital services, may beconnected either automatically or manually to a safety power supply sourcecapable of maintaining it for a minimum period of 24 h. This equipment mayinclude, for example:
! sterilization equipment! technical building installations, in particular air conditioning,
heating and ventilation systems, building services and waste disposal systems
! selected lifts for firemen! ventilating systems for smoke extraction;! paging systems!medical electrical equipment used in group 2 medical
locations which serves for surgical or other measures of vital importance. Such equipment will be defined by responsiblestaff
! electrical equipment of medical gas supply including compressedair, vacuum supply and narcosis (anaesthetics) exhaustion as well as their monitoring devices
! fire detection, fire alarms and fire extinguishing systems
! Two supply cables –main distribution: In case one cable fails, an automatic changeover unit initiates automatically a transfer to a second supply line
! changeover time <15s(time to start the generator)