Electrical Measurement Safety

You’re right to be concerned

Presenter: Curt Geeting, Fluke Corporation

Risks from electrocution and shock hazards

Shock• Contact with any source of electricity that causes a sufficient current

through the skin, muscles, or hair. • Shock can cause electrocution and death.

Risks from an arc flash

Created by a phase to phase or phase to ground short circuit.• Current passes through the air. • Ionized air (plasma) is a good conductor.• Once an arc begins, it feeds off any matter in its path and vaporizes it.• Duration is under one second.

Risks from an arc blast

The explosive result of an arcing fault. • Vaporized conductors are rapidly expelled creating such hazards as intense heat,

thermoacoustic shock wave, molten metal, shrapnel, blinding light, toxic smoke and contact with energized components.

Transients can trigger an arc flash

What causes a transient?• Motor or other inductive load switching off• Equipment malfunction• Utility load switching• Adjustable speed drives• Lightning strike

480 V rms, +/- 678 V peaks

Spikes up to 8,000 volts

Transients:• Are invisible and largely unavoidable.• May last under 100 mS but can be extremely dangerous.• May overcome test equipment input protection causing an

arc/short in the tester.

What likely causes these incidents?

1. Racking a circuit breaker – Inserting or removing a breaker on a

live bus.

2. Lose panel wiring– A lose conductor that shorts across

another conductor or ground.

3. Removing panel covers– Retaining screws and fasteners fall

into an unsecured panel against a live bus.

4. Hand tool shorted across two phases– Experienced electrician cuts into live

cable with cable shears, shear handle touches another phase.

5. Using incorrect test probes– The user gets distracted or hand

slips while measuring phase to phase or phase to ground while using old style ¾ inch probe tips.

6. Misuse of measurement tools– Measuring across phases with

an inline amp meter creating a short circuit.

– Measuring continuity on a live circuit with a tool that cannot withstand full voltage.

– Accidental shorting of phases with a test lead tip that is too long for the safety category.

1NFPA-70E – Standard for Electrical Safety in the Workplace

As the work environment and the type of job become more hazardous, the need for protection increases.

Follow industry guidelines

NFPA-70E1 addresses:Safety-related work practicesMaintenance of safety equipmentSafety requirements for special equipmentSafety related installation requirements

Boundaries apply when workers are exposed to energized electrical conductors or circuit parts.

Safe working distances Flash limits of approach

PPE Category Required Minimum Arc Rating of PPE Typical Layers 1 4 Cal/cm² 12 8 Cal/cm² 1 or 23 25 Cal/cm² 2 or 34 40 Cal/cm² 3 or more

The higher the electrical environment, the stronger the personal protective equipment must be to withstand an arc-flash incident.

Images courtesy of Salisbury

PPE – Personal Protective Equipment

The PPE category is used to determine the necessary arc rating of a garment worn during a given job task.

NFPA: Test instruments are part of PPE (Article 110.4):

• Shall be rated for circuits and equipment to which they will be connected*• Shall be designed for the environment to which they will be exposed, and the

manner in which they will be used.*• Shall be visually inspected before use. Defective or damaged equipment must

be repaired and tested before being used again*• The insulation of protective tools, including voltage test indicators, shall be verified

by test and inspection (Article 110.4(5))

* NFPA 70E 110.4(A), 2015 Edition

Reduce the risk by using the right test equipment

IEC 61010: International Standards for low voltage “test, measurement and control equipment”

Measurement Category locations or ratings

CAT IV Three-phase at utility connection, any outdoor mains conductor

CAT III Three-phase distribution, including single-phase commercial lighting

CAT II Single-phase receptacle connected loads

The level and energy of voltage impulses are dependent on the location. The closer the location is to the utility supply, the higher the available fault current and the higher the category.

IEC 61010 defines three measurement locations or categories:

The greatest danger from transients is in the high categories, because they could trigger an arc blast.

Ensure your test equipment meets or exceeds industry standards

To provide better protection for electrical workers standards have been developed for test equipment used in environments of 1000 volts or less, including 480 volt and 600 volt three-phase circuits.

1International Electrotechnical Commission

IEC 61010 are the group standards for low voltage “test, measurement and control equipment”

First the category, then the voltage

First know the category you are working in, then choose the appropriate voltage rating

• The working voltage could be 1,000 V, 600 V or 300 V• Equipment can be dual rated, meeting both requirements• If you measure power circuits, you should use a CAT III-600 V or CAT IV-600 V/CAT III-1000 V

meter, in addition to CAT IV-600 V/CAT III-1000 V test leads and probes

Voltage rating by itself can be misleading• CAT III-1000 V (withstands 8 kV transient) is safer than CAT III-600 V (withstands 6 kV

transient)

Bottom line and most importantly, know the measurement category and voltage you are working in.

The test equipment should be independently tested, marked and certified.

CAT III-600 V CAT III-1000 VCAT IV-600 V

CAT III-1000 VCAT IV-600 V

Look for CAT markings between input jacks

What if I can’t find a rating?

Older Fluke 70 Series-IIICAT II-600 V

Original Fluke 70 Series

UNDER RATEDNOT RATED

Meters and testers designed and produced prior to 1997no longer meet code and therefore should be replaced.

Independent testing and certification

• IEC sets standards, but does not test or inspect for compliance.• A manufacturer can claim to “design to” a standard with no independent verification.• To be UL listed, or CSA or TÜV certified, a manufacturer must employ the

listing agency to test the product’s compliance with the standard.• Look for the listing agency’s emblem on the meter.

“Listed” vs. “designed to”

Tester must be independently tested, marked and certified.

Read and understand the manufacturer’s instructions

1. Verify the voltage detector function is working properly.2. Make sure the detector is rated for the level of voltage being measured and

is sensitive enough for your application.3. Make sure that you also wear the appropriate PPE based on the

environment you're in.4. Make sure the hazardous voltage is not shielded.

Use only a digital multimeter or contact type voltage tester to test for the absence of voltage.

Non-contact voltage detectors

Non-contact voltage detectors are a quick, inexpensive way to check for the presence of live voltage on ac circuits, switches and outlets before working on them.

Live-dead-live testingVerify the operation of the contact voltage tester

Before beginning the absence of voltage test, check the test instrument to ensure it is working properly in accordance with NFPA 70E Article 110.9 (A)(4)

1. Wearing proper PPE, measure a voltage similar to the voltage of the equipment about to be tested. This would include whether it is ac or dc and approximately the same magnitude.

2. Now test the circuit that is supposed to be de-energized.3. Once testing is complete, re-verify the meter is still functioning properly by

going to the same known voltage source and making another measurement.

Operational readiness test

Verify proper operation of test tools on a known voltage source before and after absence or presence of voltage testing is performed.

Several options:1. Use a convenient electrical outlet (if available)2. Access live conductors (posing unnecessary risk)

–Suit up in appropriate PPE arc flash gear3. No power exists

• The Fluke PRV240 Proving Unit provides a regulated and fixed ac or dc output voltage of 240 volts specificallyto allow for verification testing of Multimeters, Clampmeters or testers

When test instruments are used for testing the absence of voltage on conductors or circuit parts operating at 50 volts or more, the operation of the test instrument shall be verified on a known voltage source before and after an absence of voltage test is performed.

NFPA70 E 2015 edition Article 110.4 (A)(5) Operation Verification proposed wording change

Double insulation, finger guards, shrouds and recessed input jacks protect against electric shock from accidental contact with live circuits.

Perform an inspection of the test leads CAT III-1000 V or CAT IV-600 V/CAT III-1000 V rating Wear indicator on lead wires Shrouded connectors Finger guards Insulation not damaged (melted, cut, cracked or

stretched) Connectors: no insulation pulled away from end

connectors Probe tips: not loose or broken off (too short) 4mm exposed probe tips in CAT III or CAT IV

environments

Test Lead Safety ChecklistDon’t let test leads be a weak point!

The amount of exposed metal at the tip of the test lead must match the energy potential of a given measurement

Minimize exposed metal for safetyIn accordance with IEC 61010-031Safety requirements for hand-held probe assemblies for electrical measurement and test.

Some leads offer extendable tip shrouds to meet the reduced tip length requirement

Other leads come with tip guards

to minimize exposed metal The higher the CAT rating the less exposed metal is allowed at the tip of the test lead.

CAT II – 19 mm (0.75 inch)CAT IV – 4 mm (0.16 inch)

The bottom line ― Safety First

Best practices include:

1. Whenever possible, work on de-energized circuits.• Follow proper lock-out/tag-out procedures

2. Use well maintained tools and appropriate personal protective equipment according to NFPA 70E.• Safety glasses, insulated tools, insulating gloves, arc-

rated clothing, arc shields, flash suits, insulating mats, etc.

3. Don’t work alone.

4. Practice safe measurement techniques.• Always connect the grounded lead first, hot second• Disconnect the hot lead first, grounded lead second

5. Use the live-dead-live test method.• Test known circuit, measure target circuit, then re-test

known circuit

Built-in protection devices guard against the most common safety hazards:

Overload protection on all functions

1000 V high energy fuses

CAT IV-600 VCAT III-1000 V

Protection that’s designed in

An industrial grade Fluke meter devotes 10 to 15% of its components exclusively to protection

1. High voltage transients and danger of arc-over2. Voltage contact while in continuity or resistance

mode3. Voltage measurement while test leads are plugged

into the amps jacks

Common errors with measurement toolsConnecting a meter to a voltage source with the meter configured for inline amp measurements.The amps mode on a meter is almost a short circuit

Measuring ohms or continuity on a live circuit.Most older meters cannot handle the full voltage on the ohms function

Handheld Test Tool Safety

Last known earthly residence of automotive fuse used to replace original fuse

Test leads survived intact

How not to save time...

The wrong meter to use on a power circuit.

Probe tips burned off

Poor quality leads and probes led to injury.

250V fuse didn’t open in time

Handheld Test Tool Safety

Fingerprints burned into probes

The electrician suffered severe burn injuries on his hand and arm.

Handheld Test Tool Safety

Fluke incorporates specially designed “high-energy” fuses in our digital multimeters

Designed to keep the energy generated by an electrical short within the fuse enclosure

• Limit the amount of time current is applied and oxygen available for combustion

• In addition to the specially designed fuse element, the high energy fuse is filled with sand

Protection devices provide additional safety

30

High temperatures (up to 10,000F) generated by the energy will meltthe sand and turn it into glass, smothering the fireball by cutting off the available oxygen

Common DMM safety hazards

• Measuring voltage while test leads are in the current jacks: short-circuit!Protection: Fluke meters use

high energy fuses.• Contact with ac or dc power

source while in Ohms mode.

• Using meter above rated voltage, i.e., on medium voltage circuits.• No Protection above rated voltages

Protection: Fluke meters have “Overload Protection”. Functions are self-protected to the meter’s rated voltage.

Three common errors that are avoidable

PRESENTER SLIDE: HIDEMeter Examples/Demonstrations

• Hold up Fluke 87 with leads in Amps Jack• To measure amps in-line, you wire your meter in series with the circuit. In order not to interfere

with the measurement , you want your meter to look like a piece of wire. Another word for a piece of wire is a short circuit. So when you have your leads in the amps input terminals, you have a dead short across these probe tips. That is why it is so important that your meter has fused input jacks. And not just any fuse, but a specially designed high energy fuse.

“ If this happens with a properly fused meter, the fuse will blow, and you will not even know it. to check the fuse, you open the meter, pull out the fuse, close the meter or get another meter, and measure the ohms or continuity to see of the fuse is open. There is a much easier way to do this, without even having to open up your meterThe black input jack is common for all measurements. So, by measuring across the Common and Amps input jacks in Ohms, you can check your fuses without opening the case(show how to do this while talking)

Never change a fuse with the wrong fuse. It is very important to replace the fuse with the manufacturer’s suggested high energy fuse Now most of the time you will be using a current clamp to measure current safely (play amps input-fuse animation)?

Safety Inspection

• In a power circuit, use current clamp accessory.• In low energy ckt, 10A or less, open the circuit:

– Measure in series (current is the same in a series circuit). The amps circuit resistance must be small, to have a minimal effect on the current. This low impedance input requires fuse protection.

Caution!!! Don’t leave the leads in mA or A input jacks and then take voltage measurements.

A, mA/uA inputs

COM

Ammeter circuit inside DMM

Amps inputs need high energy fuses

PRESENTERS SLIDE: HIDE BEFORE PRESENTATION:Next 3 slides ClampMeter Examples/Demonstrations

• Hold up Fluke 376 with iFLEX plugged into it

• “Most of the time you will be measuring current with a current clamp accessory or ClampMeter. This is a safer, noncontact method for measuring current.

• There are two type of current clamps and ClampMeters: AC and AC/DC– AC CLAMP SLIDE: AC is just a coil of wire that picks up the magnetic field (AC Current clamp slide) There are new technologies that make this

easier than every (do iFLex explanation)

– AC DC CLAMP SLIDE: AC/DC uses an electronic sensor, because DC current generates a much smaller magnetic field around the wire. (DC Current clamp slide)

• This applied to current clamp accessories you plug into your meter as well. (How DMMs measure current slide). One of the most common questions on our 800-44-FLUKE technical hot line is “I plug in my new clamp meter accessories into my meter and it does not work”

• Process Loop slide: Does any one have to check 4-20 mA control loops? Until recently, the only way to do this was too break the circuit. Now there are new test tools that can measure the loop currents with out breaking the loop (hold up Fluke 771 or 773). For these , it is very important to zero out the ClampMeter next to the wire before making the measurement.

• HOLD 771, 323, iFLex UP“ the moral of this story is that, depending on the size of the wire and the level of current you are looking to measure, there are different size ClampMeter openings to get the best measurement.

How DMMs Measure Current

• Current transformer (CT) style preferred for AC:– CT clamps have good noise immunity: recommended for

AC Variable Speed Drives and other noisy environments• How to use: use A inputs

– They are CTs with 1:1000 turns ratio: 1 A on primary (circuit being measured) =1 mA on secondary (input signal to DMM)

– Connect probe to Amps jacks of DMM.– Select A – 87: select manual range of 4000mA for direct

reading of Amps (since 1 mA = 1 A)– 26: Select manual range of 4.000A. Mentally

move the decimal three places to the right: .089 = 89 Amps• True-rms measurements require a T-rms meter.

AC Current Clamp Accessories

How DMMs Measure Current

• AC/DC clamps: use V inputs of DMM– Use Hall-effect technology:

require batteries in clamp– 1 mV per Amp. – Select Vdc or mVdc to measure DC current– Select Vac to measure AC current

• True-rms measurement (of ac current) requires a T-rms meter.

• Always “Zero” clamp next to wire before measurement to eliminate incorrect measurements from AC magnetic fields in cabinet

AC/DC Current Clamp Accessories

• In power circuits, clamps are used to measure amps.• Two types of clamps: AC or AC/DC

(Scope clamps have BNC connectors: AC or AC/DC both output mV. )

How DMMs Measure Current Current Clamp Accessories

ACModel: 80i-400

AC/DCModel: i410, i1010

Output signal Current Voltage

Scale factor 1 milliAmp per Amp

1 milliVolt per Amp

Sensor CurrentTransformer

Hall effect

Battery No Yes

2200 ºC

ZERO SPAN

Process Loops

4 to 20 mA

Transmitter

Sensor

Indicator

Loop Supply

4-20 mA process signals• Very low current, in line

measurement • Measure transmitter o/p:• Source 4-20 mA to indicator• Simulate 4-20 mA

Fluke 789

Fluke 771 mA Process Clamp Meter

• Measure mA signals without breaking the loop• Best in class mA measurement accuracy and resolution• Save time and money troubleshooting PLC analog I/O and

process loops• Detachable clamp with extension cable• Dual display with both mA and % of span readouts• Measurement spotlight illuminates hard to see wires.• Fluke 772 and Fluke 773 add full 4-20mA Source and

Measurement for loop calibration and troubleshooting

Measure 4-20 mA signals without breaking the loop.

Innovative new approach to measuring mA loop signals

Misuse of DMM in Ammeter Mode

Safety Inspection

Step 1: Plug test lead in V/ input. Select .Step 2: Insert probe tip into mA input. Read value.Step 3: Insert probe tip into A input. Read value.• Is the fuse okay? What would an open fuse read?

Checking fuses on the Fluke 87-IVStep 1: Select (w/o test leads). Step 2: Plug lead into mA and A input.Step 3: Listen for Beeps=fuse is good(special automatic warning circuit to prevent you from

doing this)

Checking meter fuses on most meters

DMM BASICS

Fluke 87: With lead in mA or A, select and listen

Common errors with measurement tools

Measuring ohms or continuity on a live circuit.Most older meters cannot handle the full voltage on the ohms function

PRESENTER SLIDE: PRACTICE and HIDE: Connecting Voltage while in the Ohms Demonstration

• Hold up Fluke 87 with leads plugged into Fluke 1587, 87=DC Volts; 1587 = Insulation Test mode

• “Part of the IEC 61010 Safety rating is if I have a 1000 volt meter, I should be able to connect 1000 volts in the volts terminals in any function, without anything happening to me or the meter.

• “Here I am applying 1000 volts to the input of this meter (Hold up 87-V with 1587 locked in 1000 mode output, walk around and show audience 1000V displayed on meter).

• I switch to ohms mode and apply the same 1000V. (show meter face “OL”) Those of you who have been around a while probably instinctively wanted to step back a little. Why? With older or unprotected meters, when you do this, if you are lucky you typically would see a puff of smoke and be in the market for a new meter. If you are unlucky, you’re holding a fire ball

• I’ll go back to volts, and see how the meter is still working fine? (Show 1000V on meter display)

• What I am using here is a mega-ohm meter, or insulation resistance tester. This pressure tests electrical wires, motor coils and such, to see if the insulation is going bad. Just as I would use water pressure to look for leaks on a hose, we use Electrical Pressure, or VOLTS, to pressureize the wire and look for leaks in t he insulation. It is also a great way to test new wiring you just installed, instead of turning everything on and looking for smoke.

• Now while you have your meter with you at all times, chances are the megaohmmeter is back in the shop. What we’ve done is take the meter (show Fluke 87 in front) and the megger (show 1587 in front with other hand) and built them into one unit ( move and hold the Fluke 87 behind the Fluke 1587). This way you always have an insulation tester with you, and you are more likely to make these tests, instead of having to walk back to the shop.

Boundaries apply when workers are exposed to energized electrical conductors or circuit parts.

Safe working distances: Work Outside the Danger Zones Flash limits of approach

New Wireless measurement toolsProvide physical separation in an arc flash environment

One technician can do jobs that would otherwise require two peopleConnect the meter or clamp to a conductor, remove the display and walk across the room to operate controls or remove protective equipment, all the while watching real-time readings.

Enhance safety with wireless toolsFluke Connect™ enabled tools for data transfer

Fluke Connect Wireless Measurement Tools

Fluke 1736/1738 Power/Energy LoggersMonitor, Record and Troubleshoot behind closed doors!

• Key Power Measurements– All measurements are measured and logged to eliminate the risk

of not recording the important parameters.• Fluke Connect App Compatible

– Enables data to be viewed without having to suit up and can remotely view measurements – no need to visit panel

• Convenient Instrument Power– Powered from the measurement circuit means there’ no need to

find a power outlet and run power cord extensions

Improves measurement efficiency, improves safety while measuring to get to answers more quickly and reliably

Fluke Connect Wireless Measurement Tools

View multiple measurements simultaneouslywith Fluke Connect™ wireless tools

View up to 10 live measurements simultaneously from energized equipment well outside of arc flash boundaries

• 3-phase current and voltage• Cause and effect relationships• Log intermittent problems over time• Verify lockout/tagout electrically safe status

Save all measurements wirelessly, for each piece of equipment, in one place, with the same one App for all testers.

• Electrical measurements• Temperature measurements• Power and Energy usage• Thermal Images• Vibration:Build your equipment maintenance database over time while doing your normal work!

The Safest Way to Measure Electricity is to Get No Where Near It!!

View the degree of heat coming from various components, all in a single image

Most equipment’s failure mechanisms involve a significant rise in operating temperature long before catastrophic failure occurs

• Equipment remains operational• Captured at a safe distance increasing

safety• Live voltage still requires full electrical

safety precautions• Access components and systems not

otherwise measurable, such as ceiling runs• Help detect imminent failures in nearly all

types of equipment• Uncover potential problems in areas that

would typically be ignored

Fluke Infrared Cameras

Abnormal heating associated with high resistance or excessive current flow is the main cause of many problems in electrical systems

Analyze the invisible with Infrared

• Troubleshoot problems in electrical connections• Detect high resistance loose connections • Check for unbalance in 3-phase electrical systems• Balance branch loads and identify excessive current consumption

Inspect indoor or outdoor switchgear and panels safely An IR window can help increase the safety of personnel and reduce the cost of predictive maintenance, in compliance with switchgear codes.

Test instrument training and proficiency

NFPA states that “Employees shall be trained to”:

• Select an appropriate test instrument for a given task• Demonstrate how to use a test instrument• Interpret results• Understand ratings of the test instrument• Perform a visual inspection of the test instrument and accessories• Perform an operational verification on a known voltage source• Identify misapplication

Next steps: Test Equipment Safety Audit

1. Complete the on-line training course for electrical measurement safety2. Match you working environment to the CAT rating of your tools3. We can help Audit your test tool inventory

• Ensure compliance with industry ratings and standards• Verify the operational readiness of your tools• Order spare parts where appropriate

4. Make training and briefings part of your daily work

Electrical Measurement Safety

You’re right to be concerned

Thank you!

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Electrical Measurement Safety Fluke Corporation © 2016

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nvanwert@Transcat.com

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Electrical Measurement Safety Fluke Corporation © 2016