How to protect Electrical Equipments in Hospitals and Health Care Centres

Electrical & Electronic systems design in health care facility is an extraordinary challenge. Required technical knowledge exceeds typical residential and
industrial construction.
Eg Patients may be undergoing surgery and in life support systems. Any break in electrical supply for more than few seconds could be fatal for them.
Further some patients may have conductive instruments in contact with the bloodstream or heart muscle where the possibility for serious injury and/or death if that metal becomes energized (even to a very low level ). Other GDQJHUV LQFOXGH ZHW DUHDV, KD]DUGV GXH WR ÁDPPDEOH
liquids and the presence of oxygen.
Technical requirement of equipment are not considered
/ provided while designing electrical system. Most equipment are connected to redundant UPS / Generators, to take care in case of a supply failure, but we forget to think what will happen if a circuit breaker trips due to a fault. This means electrical work must be designed and installed to an unusual level of safety and redundancy.
Similar to normal buildings, grounding and bonding issues create much confusion. Earthing and bonding systems distinctly differ from residential and industrial wiring systems. NEC-2011 (National Electric Code
– Bureau of Indian standards) explains a hospital environment as
The patient may not be in a condition to react normally to the effects of hazardous events
The electrical resistance of the skin, which is normally an important protection against harmful electric currents is bypassed in certain examinations or treatments
Medical electrical equipment may often be used to support or substitute vital body functions, the breakdown of which may cause a dangerous situation 6SHFLÀF ORFDWLRQV LQ PHGLFDO HVWDEOLVKPHQWV ZKHUH ÁDPPDEOH DWPRVSKHUH H[LVWV, FDOO IRU VSHFLDO WUHDWPHQW
Electric and magnetic interference may disturb certain medical examinations or treatments.
Safety Provision requirement in Hospitals

 

Sr. no Provi- sions Principal Requirements Installation Measures
 

i)

 

P0

Duration of touch voltages restricted to a safe limit TN-S, TT or IT

system

 

 

ii)

 

 

P1

As P0 but additionally: Touch voltages in patient

environment restricted to a safe limit

Additional to P0: Supply system with additional requirements

for protective earthing, etc.

 

 

 

iii)

 

 

 

P2

As P1 but additionally: Resistance between extraneous conductive parts and the protective conductor but bar of the bonding room QRW H[FHHGLQJ 0.1Ÿ  

 

Additional to P1: Supplementary equipotential

 

 

 

 

iv)

 

 

 

 

P3

As P1 or P2 but additionally: Potential difference between exposed & extraneous conductive parts and the protective possibly necessary conductor bus bar

not exceeding 10 mV in normal condition

 

 

As P1 or P2: Measurement necessary, corrective action

 

v)

 

P4

As P1 or P2. Additional protection against electric shock by limitation of disconnecting time Additional to P1 or P2: Residual current operated protective device
 

 

vi)

 

 

P5

Continuity of the mains supply maintained in case RI D ÀUVW LQVXODWLRQ

fault to earth and currents to earth restricted

 

Additional to P1, P2 or P3: IT

supply system with insulation monitoring

 

 

 

vii)

 

 

P6

 

Reduction of fault currents and touch voltages in case of a fault in the basic insulation

Additional P1 or P2: Medical isolating transformer supplying one individually piece of equipment
 

 

viii)

 

 

P7

Prevention of dangerous touch voltages in normal condition

and in single fault condition

Additional to P1 or P2: Supply with medical safety,

extra low voltage

 

ix)

 

G E

No interruption of the power supply of the essential circuits of the hospital for more than 15 s  

Safety supply system

 

 

x)

 

 

E1

No interruption of the power supply of life-supporting

equipment for more than 15 s

 

Special safety supply system

 

xi)

 

E2

No interruption of the power supply of the operating lamp for

more than 0.5 s

Special safety supply system for operating lamp
 

xii)

 

A

Prevention of

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electrostatic charges

Measures concerning explosion and ÀUH KD]DUGV
 

xiii)

 

I

No exercise interference from electric and PDJQHWLF ÀHOGV Layout of building and installation, screening

LV  electrical system in hospital should follow TN-S  with

30( GRXEOH HDUWKLQJ IRU EDVLF VDIHW\. )RU VSHFLÀF DUHDV

un earthed system or IT earthing need to be followed to

DYRLG WULSSLQJ RI SURWHFWLYH GHYLFH LQ FDVH RI ÀUVW IDXOW.

Health care facilities use number of computers and digital equipment. To eliminate data loss due  to  parallel grounding paths and resulting electromagnetic interference, insulated  earth  terminals  are  some  time necessary.

In Critical care areas or life support equipment, additional earth fault protection is required. If fault protection is for disconnection of power supply, then additional downstream protection must be installed to localize the fault so that power to life support or critical care equipment are not disturbed.

It is necessary that optimum selectivity is achieved  and

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are carried out only in few hospitals. Application of Safety Provisions

 

Sr.

No.

 

Medically Used Room

 

Protective Measures

Safety Supply System  

Explosion & Fire

Against EM

Measures Fields

    Po/P1 P2 P3 P4 P5 P6 P7 GE E1 E2 A I
i) Message room M O         O X        
ii) Operating wash room M X         O X        
iii) Ward general M O         O X        
iv) Delivery room M X   X O   O X O X O O
v) ECG, EEG, EMG room M X   X     O X       X
vi) Endoscopic room M X   X     O X   O    
vii) Examination or treatment room M O   X O   O X   O    
viii) Labour room M X   X O   O X       O
ix) Operating sterilization room M O   X     O X        
x) Urology room M X   X     O X   O    

 

xi) Radiological diagnostic and therapy room, other M X   X     O X        
  than mentioned under Sl No. (xx) and (xxiv)                        
xii) Hydrotherapy room M X   X   O O X        
xiii) Physiotherapy room M X   X O   O X        
xiv) Anaesthetic room M X X X1 X   O X X X O O
xv) Operating theatre M X X X1 X   O X X X X X
 

xvi)

Operating preparation room  

M

 

X

 

X

 

X1

 

X

  O X  

X

 

X

 

X

 

X

xvii) Operating plaster room M X   X1 X   O X X X X X
xviii) Operating recovery room M X X X1 X   O X X X X X
 

xix)

Outpatient operating theatre M X    

X1

 

X

  O X  

X

 

X

 

X

 

X

 

xx)

Heart catheterization room  

M

 

X

 

X

 

X1

 

X

  O X  

X

 

X

  X
xxi) Intensive care room M X O X1 X   O X X X   X
xxii) Intensive examination room  

M

 

X

 

O

 

X1

 

X

  O X  

O

 

O

  X
xxiii) Intensive monitoring room  

M

 

X

 

O

 

X1

 

X

  O X  

X

 

X

  X
xiv) Angiographic examination room  

M

 

X

 

O

 

X1

 

X

  O X  

O

 

O

  O
xxv) Hemodialysis room M X X X1 X     X        
xxvi) Central monitoring room M X O X1 X   O X       O
M = Mandatory measure, X = Recommended measure, X1 = As X, additionally insulation resistance measurement,

O = Additional measure, may be considered desirable.

 

Grounding and bonding requirements shall ensure optimum ground potential equipotentialisation in critical care areas using special bonding Techniques

Designing these special earthing & bonding system for hospitals is the job of an EMI/EMC expert who have wide knowledge in the subject. Some of the special Bonding requirements in hospitals are.

IT system earthing increases reliability of power supply in areas where an interruption of power supply may cause a hazard to patient. This reduces an earth fault current to a low value and thus reduces the touch voltage across a PE conductor through which this earth IDXOW FXUUHQW PD\ ÁRZ.

Separate circuits shall be provided for X-ray, electrotherapy, diathermy, electrocardiograph, etc Main Earthing Terminal for individual rooms as well as Local Equipotential bonding for patient environments.

Screening requirements against interference in rooms where measurements of bioelectric potentials are SHUIRUPHG (OHFWULFDO ZLULQJ LQVLGH ZDOOV, ÁRRU DQG

ceiling of rooms should be screened by means of metal shielding of cables to reduce Interference Caused by Mains-Induced Electric Fields Room screening inside wall structure for ECG and EEG monitoring

 

Conclusion

Special Bonding and Earthing requirements are mandatory for hospitals as per NEC – 2011 & IS 3043. But are generally  not  followed  due  to  unawareness of system requirements. Implementing these special bonding requirements is easy if structural PME earthing measures are implemented while constructing the building.

Implementing these bonding and earthing requirements, patient’s exposure to unwanted voltage on normally non- current-carrying conductive surfaces can be controlled so that their lives and health are not endangered by the electrical environment. Ɠ

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