Seguranca eletrica

7/27/2019 Seguranca eletrica

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Segurana Eltricaem ambientes

Mdico-hospitalar

Srgio Francisco PichorimBaseado no cap 14 - Webster


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Introduo Nos E.U.A., cerca de 10.000 acidentes por

ano causados por equipamentos mdicos(dados de 1998)

Quality Review in Anesthesia, Vol. 10, Issue1, March/April 2007


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Introduo

Projeto com SEGURANA: tudo que PODE dar errado considerar que

VAI dar errado .

Fontes de risco: fogo, ar, gua, drogas,microorganismos, infeco, lixo, som,eletricidade, raio X, materiais cortantes, etc.


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Corrente eltrica pelo corpo

Estimulao muscular e nervosa

Aquecimento do tecido / Queimaduras

Reaes eletroqumicas


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Figure 14.1 Physiological effects of electricityThreshold or estimated mean values are given for each effect in a 70 kg human a 1 to 3 s exposure to 60 Hz current applied via copper wires grasp

by the hands.


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Parmetros importantes de

Susceptibilidade Variabilidade dos limites

Freqncia Durao e momento (onda T fibrilao) Peso do corpo Pontos de entrada (risco menor se pontos

so na mesma extremidade) derivao I menos sensvel que II e III.


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Figure 14.2 Distrubutions of perception thresholds and let-go currentsThesedata depend on surface area of contact (moistened hand grasping AWG No. 8copper wire). (from C. F. Dalziel, "Electric Shock," Advances in Biomedical

Engineering , edited by J. H. U. Brown and J. F. Dickson IIII, 1973, 3, 223-248


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Figure 14.3 Let-gocurrent versus

frequency Percentile

values indicatevariability of let-gocurrent among

individuals. Let-gocurrents for women are

about two-thirds thevalues for men.(Reproduced, with

permission, from C. F.Dalziel, "Electric

Shock," Advances in Biomedical

Engineering , edited byJ. H. U. Brown and J. F.Dickson IIII, 1973, 3,

223-248.)


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Figure 14.4 Fibrillationcurrent versus shock duration. Thresholds for ventricular fibrillation in

animals for 60 Hz ac current.Duration of current (0.2 to 5 s)

and weight of animal bodywere varied. (From L. A.

Geddes, IEEE Trans. Biomed. Eng ., 1973, 20, 465-468.

Copyright 1973 by theInstitute of Electrical and

Electronics Engineers.Reproduced with permission.)


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REDE ELTRICA

HOSPITALAR Equipamentos mdicos Iluminao Aquecimento e ar condicionado

Convenincias (TV, frigobar, secador de cabelo, etc, etc)


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ENTRADA: Transformador trifsico

Potncia de 15 a 300 kVA


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Figure 14.6 Simplified electric-power distribution for 115 Vcircuits. Power frequency is 60 Hz.


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TOMADA UNIVERSAL&

TOMADA ABNT NBR 14136 - 2002


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Valores mximos nas

proximidades do paciente rea geral = 500 mV

rea de cuidado crtico = 40 mV Superfcies condutoras aterradas no

mesmo ponto de terra. Testes peridicos de tenso e de

continuidade entre os terras das tomadas


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Presena de Tenso no Paciente

Principal problema Falha deaterramentoi.e., um curto entre a fase e oterra.

Uma possvel soluo isolar oscondutores do terra, utilizandotransformadores de isolao.


16/53Figure 14.7 Power-isolation-transformer system.


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LIM

Monitor de Isolao de Linha Monitora a corrente de fuga (resistiva ou

capacitiva) entre fase e terra e neutro eterra. Alarme para correntes superiores a 5 mA. Custo elevado (US$ 2.000,00) Necessrio em reas com presena de

umidade e com anestsicos inflamveis.


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Figure 14.7 Power-isolation-transformer system with a line-isolation

monitor to detect ground faults.


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Grupo Gerador a DieselRATED POWER 64 kWENGINE MODEL 6105ZD

SPEED 1500 rpmFUEL

CONSUMPTION 231 g/kW.h

COOLINGMETHOD RADITOR

STARTINGMETHOD

ELECTRICSTARTING

RATEDVOLTAGE 220 V/ 380 V

RATEDCURRENT 115 A

FREQUENCY 50 HZPOWER FACTOR 0.8

PHASECONNECTION

3-PHASE4-WIRE

PACKING SIZEL*W*H (mm)

2500 * 950 *1300


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Sistema No-Break
http://upload.wikimedia.org/wikipedia/commons/7/77/Standby_UPS_Diagram.png


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Macrochoque

&

Microchoque


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20A para cachorro 80 a 600 A para humanos

10A limite aceito como seguro


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M A C R O C H O Q U E

Resistncia da pele: seca e intacta de 15 k W a 1 MW.

Valor cai 100 vezes quando a pele estmolhada ou apresenta algum corte!

Resistncia interna 200W por membro e100W no tronco (= 500W entre braos!)


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Figure 14.8Macroshock due to

a ground faultfrom hot line toequipment cases

for (a) ungroundedcases and (b)

grounded chassis.


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M I C R O C H O Q U E Corrente de fuga: Capacitncias parasitas

de cabos prximos, ou Resistncia desujeiras, umidade ou m isolao.

Falta de aterramento ou alta resistncia no

terra.

I max = 10 A (normas de 10 a 100 A)


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Figure 14.9 Leakage-current pathways Assume 100 A of

leakage current from the power line to the

instrument chassis. (a)Intact ground, and 99.8A flows through theground. (b) Broken

ground, and 100 A flowsthrough the heart. (c)

Broken ground, and 100

A flows through theheart in the oppositedirection.


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Figure 14.11 (a) Large ground-fault current raises the potential of one groundconnection to the patient. The microshock current can then flow out through

catheter connected to a different ground.


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MICROCHOQUE POR DIFERENA DE

POTENCIAL DE TERRA ( > 40mV )


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NORMAS

IEC - International Electrotechnical Commission

Norma IEC 60.601-1 Norma geral desegurana eltrica.

Normas IEC 60.601-2-X Especficas para cada tipo de equipamento mdico.


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IEC 60601-2-X MEDICAL EQUIPMENT - PART 2REQUIREMENTS FOR THE SAFETY OF...

IEC 60601-2-2 HIGH FREQUENCY SURGICAL EQUIPMENT IEC 60601-2-4 CARDIAC DEFIBRILLATORS AND DEFIBRILLATORS - MONITORS IEC 60601-2-5 ULTRASONIC PHYSIOTHERAPY EQUIPMENT IEC 60601-2-10 NERVE AND MUSCLE STIMULATORS IEC 60601-2-12 LUNG VENTILATORS FOR MEDICAL USE IEC 60601-2-16 HAEMODIALYSIS EQUIPMENT IEC 60601-2-19 BABY INCUBATORS IEC 60601-2-22 DIAGNOSTIC AND THERAPEUTIC LASER EQUIPMENT IEC 60601-2-24 INFUSION PUMPS AND CONTROLLERS IEC 60601-2-25 ELECTROCARDIOGRAPHS IEC 60601-2-26 ELECTROENCEPHALOGRAPHS IEC 60601-2-27 ELECTROCARDIOGRAPHIC MONITORING EQUIPMENT

IEC 60601-2-30 NON-INVASIVE BLOOD PRESSURE MONITORING EQUIPMENT IEC 60601-2-33 MAGNETIC RESONANCE EQUIPMENT FOR MEDICAL DIAGNOS IEC 60601-2-37 ULTRASONIC MEDICAL DIAGNOSIC AND MONITORING EQUIPM IEC 60601-2-38 ELECTRICALLY OPERATED HOSPITAL BEDS IEC 60601-2-40 ELETROMYOGRAPHS AND EVOKED RESPONSE EQUIPMENT IEC 60601-2-51 RECORDING AND ANALYSING SINGLE CHANNEL AND

MULTICHANNEL ELECTROCARDIOGRAPHS


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Proteo contra choques

Paciente isolado de qualquer superfciecondutora

Superfcies condutoras no mesmo potencial

Pacientes com pele aberta ou ambientemido. Proteo e cuidados extra!


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SISTEMA DE TERRA. Conexes no excedendo0,15W etenso no maior que40mV!


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Ground-faultcircuit

interrupters

Custo de US$10,00


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Projeto do EquipamentoEletromdico

Terra confivel (no desligar o terra!)

Reduo de corrente de fuga (< 1 A/m) Dupla isolao (gabinete externo,knobs , botes e chaves no condutores.

Uso de baixa tenso (baterias) Amplificadores com Isolao eltrica


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Figure 14.14 Electrical isolation of patient leads to biopotentialamplifiers(a) General model for an isolation amplifier.

Isolation barrier

CM

CMCMRR

SIG ISO

ISO

Error

Isolationbarrier

IsolationCapacitanceand resistance

-

+

-

+

Input common

(a) *IMRR in v/v

Outputcommon o =

CMCMRR

ISOIMRR SIG Gain

R FISO

IMRR *~ ~

~

~

~

Error

1 a 10 kV e R > 10MW


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Isolamento ptico Digital Monitor de Pulsos Cardacos con Interfaz a PC , C A Centeno e I A Tren

Facultad Regional Crdoba - Universidad Tecnolgica Nacional

Isolation barrier


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Figure 14.14 Electrical isolation of patient leads to biopotential amplifiers(c)Simplified equivalent circuit for an optical isolator (Copyright (c) 1989 Burr-

Brown Corporation. Burr BrownISO100)

Isolation barrier

Inputcontrol Outputcontrol

-

V

+V + o

-

+

o = i R K R G

CR 3 CR 1 CR 2

i 2

i i

i

i 1

R G

AI AI I i 3i 2

o

R K = 1MW

-

+

-

++

-

(c)

~

1 2


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Figure 14.14 Electrical isolation of patient leads to biopotential amplifiers(d) Capacitively coupled isolation amplifier (Horowitz and Hill, Art of

Electronics , Cambridge Univ. Press. Burr BrownISO106).

Frequency-to-

voltage converter(phase-lockedloop)

OscQ Q

15 V (Receiver) 15 V (Driver)Isolationbarrier

(d)

3 pF

3 pF

Freqcontrol

Analogsignal out, oAnalogsignal in, i


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ISOLAO EM SENSOR DE PRESSO A) Cateter condutor - distribuir a corrente de fuga por todo corpoB) Sensor eltrico de presso isolado da soluo salina

C) Cateter com fibra ptica

D) Sensores passivos e telemtricos

Gel

Clear plastic4 cm

Saline Flush valve

IV tubing

Electrical cableSilicon chip

To patient


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Testes

Resistncia Neutro Terra < 0,2W

Tenso entre o aterramento e reascondutoras < 20 mV (normas aceitam

at 500 mV para construes antigas)


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Figure 14.17 Ground-pin-to-chassis resistance test

Appliance power switch( b h OFF d ON i i )


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Figure 14.18 (a) Chassis leakage-current test. (b) Current meter circuit to be

used for measuring leakage current.

To exposed conductivesurface or if none, then 10 by20 cm metal foil in contactwith the exposed surface

Insulating surface

Current meterI

Test circuit

Open switchfor appliancesnot intended tocontact a patient

Grounding-contactswitch (use inOPEN position)

Polarity- reversingswitch (use bothpositions)

(use both OFF and ON positions)

This connectionis at serviceentrance or onsupply side of separately derivedsystem

Buildingground

H (black)

N (white)

Appliance

GN

H

H = hotN = neutral (grounded)G = grounding conductor

< 500 uA for facility owned housekeeping andmaintenance appliances

< 300 uA for appliances intended for use in the patient vicinity

120 V

G (green)


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Figure 14.19 Test for leakage current from patient leads to ground


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Figure 14.20 Test for leakage current between patient leads


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Figure 14.21 Test for ac isolation current.

Se aparecer a tenso da linha sobre o paciente!


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