Transcript basics_of_meter_safe.. - IDEAL INDUSTRIES, INC.

Basics of Meter Safety
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
1 of 26
Digital Multimeter Safety
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
2 of 26
Ideal Test and Measurement
Safety Practices with Electrical Testers
• Goal
– Awareness of the potential
Measurement Hazards
– Learn How to minimize and
avoid Electrical measurement
hazards
– Understanding of UL61010
(IEC 601010)
• Over-Voltage Categories
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
3 of 26
Why should we be Concerned?
• An electrician
troubleshooting a live
480V motor control center
receives serious secondand third-degree burns
from an electric arc. The
cause?
– Meter was incorrectly
switched on his multimeter
to read resistance instead of
voltage.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
4 of 26
Why should we be Concerned?
• Two electricians are severely
burned — one fatally — while
testing for voltage in a motor
starter. One held the multimeter
while the other applied the
meter's probes to energized
terminals. One electrician's
movement caused one test lead
banana plug (energized from the
circuit under test) to pull loose
from the multimeter jack.
– The plug made contact with
the starter's grounded metal
enclosure and initiated a highenergy arc.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
5 of 26
Why should we be Concerned?
•
An electrician is sent spiraling
from a steel tower while
checking a circuit with a
multimeter. He was using a
meter rated for 1000V to verify a
15kV circuit believed dead. He
didn't know the circuit was hot.
Therefore, when he applied the
multimeter, a phase-to-ground
fault occurred.
– Fortunately, his safety
harness stopped his fall and
coworkers on the ground
rescued him.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
6 of 26
Common Mistakes Made
• Test Leads in the Current
input ports and user
mistakenly makes an AC or
DC Voltage
– In this example there were two
errors made by the end user.
• AC voltage measurement with
the Test leads in the current
input.
• Improper fuse had been used
in the meter from a past error.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
7 of 26
Common Mistakes Made
Current Measurements with Meters
Current
• Make sure not to exceed
the Max input of your
meter.
Protection
Fuse
– Most common mistake is to
measure voltage with the
leads in the current inputs.
– Current inputs are very low
resistance. It appears as a
short circuit to Voltage.
– For current input protection
most DMMs’ are Fused.
– Look for high energy fusing.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
Ideal 61-490 series give a probe error
message and High audible warning if
this mistake is made.
8 of 26
Common Mistakes Made
• Function Switch in
wrong function for
attempted measurement
– Example: AC or DC voltage
measurement with function
switch in Ohms.
– Most Ideal meters are Overload
Protected and the protected
levels are listed in the operation
manual.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
Ideal 61-700 series will
give you a Hi-V and
audible warning if you
make this Mistake
9 of 26
Common Mistakes Made
• Using a meter in an area
above its stated rating
– Example: 2,300 voltage
measurement with an
instrument rated for Low
Voltage (600V AC/DC.)
– Overload Protected can not
protect you from this Kind
of mistake.
– Most Overload protected is
rated based on instruments
highest voltage
measurement rating.
© 2007 Ideal Industries
www.idealindustries.com
There are Bold Electricians and
Old electricians, but not many
Bold-Old ones
Basics of Meter Safety
10 of 26
Common Safety Hazards
• High Voltage transients
from lightning, large
inductive loads being
switched on and off, or
capacitive discharge.
– Select meter with the proper
UL/IEC Category rating for
the environment that user is
going to be working in.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
11 of 26
Safety Practices
• Visually inspect the
test tool.
– Check for any contaminate on the test
leads, tester case, holsters, and
accessories.
– Never use testers that have signs of
cracked cases, or loose components.
– Never use a tester in an environment
that is beyond the capabilities
described in the specifications
– Use manufactures recommended
replacement components, like leads
and fuses.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
12 of 26
Safety Practices
• Visually inspect Test
Leads
–
–
–
–
–
Proper Category rating
Double insulation
Shrouded connectors
Finger guards
Insulation not damaged: not melted,
cut, cracked, stretched
– Connectors: no insulation pulled away
from end connectors
– Probe tips: not loose or broken off (too
short)
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
13 of 26
Before you get Started
• Quick Check of your Test Tool
–
–
–
–
•
Digital Multimeter or Digital Clamp meter
Check the Test Leads
Place the DMM in the lowest resistance range and short the Test Leads
Move the test lead at in input of the meter at the ankle of the leads. Watch that
the resistance is less than 0.5 ohms. Do the same at the leads grip and tips. If at
any time during this test the resistance exceeds 0.5 ohms the leads my need to
be replaced.
It is also a good Idea to check the DC voltage and Ac voltage with a
known source before beginning the day.
– This doesn't negate the “Three point measurement” method.
•
•
If the unit has current, check the Fuse, and remember to replace with only
the manufacturer recommended replacement part.
Remember to always be aware of your battery usage. Digital instruments
will become erratic or can give improper readings once the power drops
below normal operating levels
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
14 of 26
Before you get Started
•
•
Whenever possible, work on de-energized circuits.
Use well maintained tools and appropriate safety gear
– Follow New NFPA 70E Guidelines
• Safety glasses, insulated tools, insulating gloves,
flash suits, insulating mats, etc.
•
•
•
Follow proper safety precautions and Lockout Tag out
practices.
Never Work alone when making measurements on live
circuits.
Always do a performance test on your tester before making
a measurement on an unknown circuit.
– Use the 3 point method. Measure a known test point , Make
the unknown measurement, then back to the known test
measurement.
– Change battery when indicated
– Check test leads regularly
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
15 of 26
Know your tester
•
•
•
•
Packaging
– Material,
• Insulation rating
• Environmental rating,
Splash proof or not.
Features
– MIN/MAX, Peak, Hold
Measurement Functions
– AC Volts, DC Volts
Capacitance, etc
– Measurement range and
Maximum input
– Input protection.
Safety
– CATegory rating, UL, CE
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
16 of 26
Certified Devices and Equipment
• Look for tools that are
Certificated by an independent
lab,
– UL , IEC, CSA.
• Pay close attention to the safety
rating on the equipment.
– Never use equipment that
is not properly rated
• Never use accessories that are not
recommended or rated for your
tester or environment.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
IEC Cat ratings
The New UL 61010B standard
incorporates features of the IEC
601010 standard. This standard
has improved safety benefits
over the old UL 1244 standard
17 of 26
IEC Category Ratings
• IEC 61010 defines as
four Categories:
– CAT IV “Origin of
installation”,
– CAT III Distribution
Level,
– CAT II Local level,
– CAT I Signal Level,
If a lighting strike was to hit your electrical service a certain amount of
energy or impulse would travel and be dissipated by the electrical service.
The closer to the source of the impulse the Higher available fault current.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
18 of 26
International Electro-technical
Commission
•
•
•
IEC 61010 requires an instrument
provide protection against “overvoltage impulse transients” - voltage
spikes.
IEC 61010 is the basis for:
– ANSI/ISA-S82.01-94 (US)
– CAN C22.2 No. 1010.1-92 (CAN)
– EN61010-1:1993 (EUR)
UL 61010B standard incorporates
features of the IEC 601010 standard,
– This standard has improved safety
benefits over the old UL 1244
standard and the old IEC 348
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
19 of 26
Impulse Fault
– The closer to the source of the impulse the Higher available
fault current.
– If an instrument was to be hit by an impulse and a fault
condition was to occur the Available energy “Fuel” the Fault.
– Lets use the example of water or water pressure.
– The larger the pipe the Greater the potential
– The closer to the supply the Greater the potential
Faucet with
½ inch
supply line
© 2007 Ideal Industries
www.idealindustries.com
Fireman
with a 4 inch
hose
Basics of Meter Safety
20 of 26
Category rating, Voltage mean
What
• Voltage rating by itself
can be misleading.
– CAT III-1000V (8kV
transient) is safer than
CAT III-600V (6kV
transient)
– But CAT III-600V is
safer than CAT II1000V
© 2007 Ideal Industries
www.idealindustries.com
CAT III-600V or CAT II1000V?
The greater the source impedance,
the lower the Category:
• CAT III-600V:
– 6 kV impulse
– 2 Ohm test source
• CAT II-1000V:
– 6 kV impulse
– 12 Ohm test source
A CAT III-600V 6kV test impulse
has 6 times the current of a
CAT II-1000V 6kV test
impulse!
Basics of Meter Safety
21 of 26
CAT IV
Equipment of over-voltage category IV is for use
at the origin of the installation (utility service).
• Outside and service entrance
• Service drop from pole to
building
• Run between meter and
panel
• Overhead line to detached
building
• Underground line to well
pump
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
22 of 26
CAT III
Category III is Premises wiring: “mains”circuits, i.e.,
bus and feeders and distribution panels
•
•
•
Permanently installed loads:
motors, lighting systems, drives,
load centers.
Typically separated from utility
service by at least a single level
of transformer isolation.
Does not include receptacle
plug-in loads, except in the case
of heavy appliance outlets with
“short” connections to service
entrance
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
23 of 26
CAT II
Category II: Loads that plug in at receptacle outlet
• Examples of such equipment
are appliances, portable tools
and other household and
similar loads
• All outlets at more than 10 m
(30 ft) from Category III
• All outlets at more than 20 m
(60 ft) from Category IV
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
24 of 26
CAT I
Equipment in which measures are taken to limit
transient over-voltages to an appropriately low level.
• Examples are protected
electronic circuits. A
copier that has an internal
step-up transformer and
1000Vdc is still a CAT I1000V machine, because
the current levels are so
low.
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
25 of 26
Thank you
Ideal Industries, Inc
Test and Measurement Division
1 Becker Place
Sycamore, Il 60178
(800) 435-0705
You may want to refer to the Following Papers
Case histories come from an IEEE paper entitled “Personnel Safety
and Plant Reliability Considerations in the Selection and Use of
Voltage Test Instruments,” (IEEE Transactions on Industry
•
•
•
•
Applications, Vol. 33, No. 2, March/April 1997),written by
H. Landis Floyd II and Brian J. Nenninger.
ANSI C62.41 - IEEE Recommended Practice on Surge Voltages
IEC 601010
UL 3111
Part II NFPA Code 70E
© 2007 Ideal Industries
www.idealindustries.com
Basics of Meter Safety
26 of 26