Transcript Electrical Safety * NFPA Requirements

Created by: SSgt Hans Arcand
2012 NFPA - TESTING INTERVALS
- Electrical safety tests must be performed when equipment is initially installed, and
after any patient-care related repairs or modifications
Electrical Safety Inspections Include:
- Leakage Current (Fixed Equipment)
- Touch Current (Portable Equipment)
- Lead Leakage (All Leads Tested In Parallel)
- Resistance Measurements (All Units)
Reference NFPA 99, 2012, Section 10.5.2.1.2, Testing Intervals
VISUAL INSPECTION
Visually inspect the power cord assy for signs of degradation…pay close attention to
the means of grounding.
-Power Cord Assy
- Power Cord
- Attachment Plug
- Cord Strain Relief
- Look for cuts, knicks, abrasions, tears or possible separation of the power cord assy,
and its contents.
- Visual electrical safety inspections do not have to be formally documented, BUT they
will be completed on all scheduled AND unscheduled maintenance work orders.
BE OBSERVANT!!!
Reference NFPA 99, 2012, Section 10.3.1, Physical Integrity
POWER CORD RESISTANCE
- Power Cord Resistance Tolerances
- NFPA 99
.50 Ohms – Maximum Permissible Limit Within a Healthcare Facility
(1)The cord shall be flexed at its connection to the attachment
plug or connector.
(2)The cord shall be flexed at its connection to the strain relief
on the chassis.
- IEC 60601-1
Detachable Power Cord - .10 Ohm
Non-Detachable Power Cord - .20 Ohms
- Polarity tests are recommended on initial equipment assembly and power cord repairs.
Reference NFPA 99, 2012, Section 10.3.2, Resistance
LEAKAGE CURRENT TESTING – FIXED EQUIP
- Leakage current refers to the current that is felt on the grounding conductor of
FIXED/PERMANENTLY-WIRED EQUIPMENT
- Leakage tests shall be performed in the ‘ON’ and ‘OFF’ positions to simulate realworld patient-care situations
- Leakage current shall not exceed 10mA through the grounding conductor of
permanently-wired equipment, while grounds are lifted.
- No annual requirement for performing electrical safety tests on fixed/ permanentlywired equipment.
Reference NFPA 99, 2012, Section 10.3.4, Fixed Equipment
TOUCH CURRENT
- Previously known as chassis leakage, chassis touch, or leakage current
- Refers to the leakage current through the chassis/housing of portable equipment
- Touch current limits
- Cord-connected equipment/normal polarity/ground intact- 100uA
- Cord-connected equipment/normal polarity/ground disconnected - 500uA
- When multiple devices are connected together and more than one power cord supplies
power, the devices shall be separated into groups according to their power supply cord,
and the leakage current shall be measured independently for each group as an
assembly.
If the collective leakage current of connected devices exceeds 500uA, efforts to
reduce the leakage current must be made. (e.g. separating equipment/appliances,
additional power supplies)
Reference NFPA 99, 2012, Section 10.3.5.1, Touch Current Limits
LEAD LEAKAGE TESTING
- Leads should be tested in parallel (all connected)
- The testing of individual leads is no longer required, per NFPA 99, 2012 rev.
- Lead Leakage is performed with the plug connected normally and the device ON
- Limits
-100uA/Ground Connected
-500uA/Ground Open
Reference NFPA 99, 2012, Section 10.5.2.1.2, Testing Intervals
NFPA TESTING DIAGRAMS
2-Wire Resistance Measurement
-Two-Wire Resistance Technique. A known current is fed through the unknown
resistance. A high-input-impedance voltmeter measures the voltage drop across
the resistance, R, and R is calculated as voltage divided by impedance, V/I. This
technique measures the lead resistance in series with the unknown resistance.
When the unknown resistance is a ground wire (less than 0.15 ohm), the lead
resistance is appreciable. This is accounted for by shorting the lead wires
together and “zeroing” the voltmeter. The actual resistance, in effect, subtracts
out the lead wire resistance. In order for this technique to be reasonably accurate
for measuring ground wires, an active high-impedance millivoltmeter has to be
used.
Reference NFPA 99, 2012, Section A10.3.2, Resistance
NFPA TESTING DIAGRAMS
4-Wire Resistance Measurement
Four-Wire Resistance Technique. This technique is very similar to the two-wire
resistance technique. The difference is that the known current is fed to the
resistance to be measured through a pair of leads separate from the pair of leads
to the voltmeter. The voltmeter is measuring the true voltage across the
resistance to be measured, regardless of the resistance of the measuring leads.
This method eliminates the need for zeroing out the measuring lead resistance.
Reference NFPA 99, 2012, Section A10.3.2, Resistance
NFPA TESTING DIAGRAMS
AC Current Method
AC Current Method. This technique utilizes a step-down transformer of known
voltage output to feed current through the ground wire and measure the current
that flows. The impedance of the ground wire is then calculated by Ohm’s law.
Reference NFPA 99, 2012, Section A10.3.2, Resistance
LEAKAGE CURRENT TESTS - NFPA TESTING DIAGRAMS
If the required performance is obtained by a meter with integral response-shaping
properties, then that meter should have a constant input resistance of 1000 ohms. (A
high-input-impedance meter can be used by shunting a 1000 ohm resistor across the
meter’s input terminals.)
If, however, the required frequency response is obtained by a network that precedes an
otherwise flat-response meter, then the input impedance of the network should be
1000 ohms ±10 percent, over the frequency range from 0 to 1 MHz, and the frequency
response of the network–meter combination should be substantially independent of
the impedance of the signal source.
For maximum chassis leakage current permitted (i.e., 300 μA) below 1 kHz, this network
will yield the limiting current of 10 mA above 30 kHz.
Reference NFPA 99, 2012, Section A10.3.3, Leakage Current Tests
2012 NFPA CHANGES
The 2012 edition of NFPA 99 has eliminated the 2005 edition requirements for the
leakage current tests between each patient lead and ground; the isolation test;
and the tests of leakage current between any one lead and each other lead,
non-isolated input, and isolated input.
This decision was based on an effort to streamline regular testing requirements and
to ensure that the effort expended in required testing provides a reasonable level
of safety value.
The remaining requirement for testing the leakage current between all patient leads
connected together and ground, as well as the touch current tests, is considered
to be sufficient to determine any failures in leakage current protection for patients
connected to portable equipment.
Reference NFPA 99, 2012, Section 10.3.6.3
PATIENT/NON-PATIENT OWNED ELECTRICAL
DEVICES
- Electrical appliances/equipment in patient-care areas shall be visually inspected by
patient care staff or other personnel
- Non-patient care items must be in a clean, serviceable and working order, in order to
be used in the healthcare facility
- Equipment that is deemed unsafe, dirty or in unserviceable condition, shall be
immediately removed from service
- Non-patient care items, in patient care areas, are not required to meet the same
electrical safety requirements, as defined throughout this training.
- a few examples of these non-patient care items include:
-computers, speakers, dvd players…etc
Reference NFPA 99, 2012, Section 10.4.2.1, Portable Equipment
in Patient Care Room.
EXTENSION CORDS
- Only used in emergencies
- No 3 to 2-prong connectors are allowed in healthcare facilities
- Extension cords will be tested for:
1. Physical Integrity
2. Polarity
3. Continuity of grounding at the time of assembly
WHAT DOES THIS ALL MEAN?
Electrical Safety Measurements (e.g., Touch Curent, Chassis Current, Grounding
Resistance, Lead Leakage) will only be completed during INITIAL
INSPECTION/ACCEPTANCE work orders, and ALL open-case REPAIRS.
Visual Safety Inspections (e.g., inspection of power cord assy, strain reliefs,
attachment plugs and chassis integrity) will be conducted during EVERY
scheduled AND unscheduled maintenance activity.
--Visual safety inspections are the new electrical safety standard, as outlined in
NFPA 99, 2012 Edition.
SET-UP 232D
For PCR/CL, external lead, the unit
needs to be set to Case Leakage
uA, EXT LEAD, w/ ground closed
For CL through the Ground
Conductor, the unit needs to be set
to Case Leakage uA, GROUND
CONDUCTOR, w/ ground open
FLUKE 232D – SAFETY ANALYZER
- Grounding resistance of the equipment power cord;
- Leakage current from the equipment's chassis or ground wire;
- Equipment load current;
- Voltage gradient (mV) and intergrounding resistance (mOhms) using the external meter function;
and
- Power system AC voltages:
• neutral to hot,
• neutral to ground, and
• hot to ground
- Fault Conditions
• neutral (open and closed)
• ground (open and closed)
• polarity (normal and reverse)
An internal ground fault circuit interrupter (GFCI) protects both the operator
and the equipment under test. If a hot line to ground fault condition
exceeding 10 milliamperes occurs, line voltage is immediately removed from
the test receptacle.
FLUKE 232D CONT’D
- Leakage current tests referenced to power ground
• on all patient electrodes;
• on individual patient electrodes-RL, 'RA, LA, LL, and
the Vl-6 set; and
• between specified patient electrode pairs:
right arm and left arm (RA-LA),
right arm and right leg (RA-RL), and
left arm and right leg (LA-RL).
- Isolation of all patient electrodes from ground with 120 VAC
applied by the analyzer. (The current-limited test voltage is
applied to the patient electrodes only when a front panel
push-button is depressed and held by the operator.)