HOSPITAL SAFETY SYSTEMS SYSTEMS
 

 


Need for Electrical Safety in Hospital
  • The patient`s natural reactions to hazards are reduced or switched-off
  • The heart muscle is highly sensitive to electric currents (currents > 10 µA)
  • The insertion of catheters and the like into the body may reduce the electrical resistance of the skin
  • Body functions are temporarily or continuously supported or substituted by medical electrical devices
  • Fire and explosion risks through the use of anaesthetics, disinfectants or cleaning.
  • Even small currents flowing through the human body put the patients life and health at risk.
  • The availability of the power supply must be guaranteed, even under fault conditions.

 

Power Supply Group definitions in medically used Rooms according IEC 60364-7-710

710.3.5  Group 0

710.3.6  Group 1

710.3.7  Group 2

Medical location where no applied parts are intended to be used

Medical location where applied parts are intended to be used as follows:

    • Externally
    • Invasively to any part of the body, except where 710.3.7 applies

Medical location where applied parts are intended to be used in applications such as intra-cardiac procedures, operating theatres and vital treatment where discontinuity (failure) of the supply can cause danger of life
  • Massage room
  • BedroomHaemodialysis room
  • Physiotherapy room
  • Operating theatre
  • Heart catheterization room
  • Intensive care room
  • Premature baby room

 

Medical IT System in Group 2 Locations

In group 2 medical locations, the medical IT system shall be used for circuits supplying

  • Medical electrical equipment
  • Systems intended for life support
  • Surgical applications
  • Other electrical equipment located in the "Patient Environment"


The IT system is supplied by an independent power source, e.g.

    • Distribution / isolation transformer
    • Control-power transformer
    • Generating set
    • Battery
    • Inverter of an UPS


The IT system has no direct connection between live conductors and earth

  • All exposed conductive parts of the electrical installation are earthed
  • IEC 60364-7-71:A permanent insulation monitoring device must be designed to indicate the first occurrence of a live mass or earth fault; it must trigger an audible or visual signal.

Need for Medical IT System

Insulation Fault

  • In the event of an insulation fault RF only a very low current ICe flows 
  • Fuse does not trip
  • In the event of a single-pole earth fault, the power supply is guaranteed
  • No interruption of operation
  • An Alarm is indicated if an A-ISOMETER is installed

Leakage Current

  • The IT system is a small local network with low leakage capacitances.
  • The fault current is limited by the body impedance, the earthing resistance and the high impedance of the fault loop.
  • Hazards to persons and equipment arising from high fault currents are reduced.

 

Fire Risk

  • A small current flows limited by the high impedance of the fault loop.
  • Considerable less fire risk
  • Increased protection for persons and equipment

 

REQUIREMENTS OF MEDICAL IT SYSTEM

Protection against Dangerous Overloads and Insulation Failure

Requirements for Power Supply Transformer

  • 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 leakage current 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.
  • IEC 61558-2-15 Safety of power transformers, power supply units and similar
  • Part 2-15: Particular requirements for isolating transformers for the supply of medical locations:
    • short circuit voltage ≤ 3%
    • no-load input current ≤ 3%
    • inrush current ≤ 12 x rated input current
  • Single phase transformers
    • ES0710 series
    • acc. to IEC 61558-2-15
    • 1…10 kVA
    • Vertical or horizontal version, or installed in an enclosure
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Monitoring of Transformer

  • Monitoring of overload and high temperature for the medical IT transformer is required
  • But no circuit breaker for protection against overload and overcurrent should be used (risk: unexpected tripping of the fuse)
  • Overcurrent protective devices (MCB) should only be used for short-circuit protection.
  • If too many medical electrical devices are in use in an operating room, the information will be displayed on a remote indicator if provided.

Requirements for Insulation Monitoring Device
  • For each group of rooms serving the same function, at least one separate medical IT system is necessary.
  • The medical IT system shall be equipped with an insulation monitoring device in accordance with IEC 61557-8 with the following specific 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
  • The insulation monitoring device (IMD)
    • signals the first fault (RF < 50 kOhm)
    • provides advance information for the medical and technical staff

Hence the essential requirements for Medical IT System are Monitoring of Load, Temperature and Insulation

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Requirements for Remote Alarm Indications

 

  • For each medical IT system, an acoustic and visual alarm system shall be arranged at a suitable place so 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 the normal condition is restored
    • Note: Additionally overload and overtemperature of the IT system transformer must be indicated.

 

Insulation Fault Location

 

  • The problem
    • In intensive care locations several socket-outlets are arranged at every patient place, sometimes up to 24 socket outlets and more
    • In an intensive care unit with 4 beds, for example, these are more than 90 socket outlets
    • In intensive care units usually no technical experts are present, but medical personnel
    • If a defective device causes an insulation fault, it will be very difficult to locate the associated socket outlet
    • In order to guarantee the patient's safety, the insulation fault must be found as quick as possible.
  • The solution
    • Insulation fault location system EDS474

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Functional Diagram of EDS System

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Benefits

  • Ungrounded Power Systems according to IEC364-7-710
  • Fault location systems offer precise and fast localisation of defective electrical equipment offer and guarantee a higher protection for patients and staff
  • Modern and sophisticated indication panels and visualization possibilities offer precise and fast information to medical and technical staff
  • Testing the electrical safety of medical electrical equipment acc. to IEC 62353  / 60601-1