1 of 35 © 2007 Ideal Industries Power Quality At the Plug IDEAL INDUSTRIES Author: Brian Blanchette Application Guide to Power

© 2007 Ideal Industries www.idealindustries.com Power Quality At the Plug 1 of 35

Power Quality At the Plug

IDEAL INDUSTRIES

Author: Brian Blanchette

Application Guide to

Power Quality at the Plug


Branch Circuit Testing

A portion of a wiring system in the interior of a

structure that extends from a final overload protective device to a

plug receptacle or a load such as a lighting fixture,

motor, or heater

Branch circuit



Branch circuits include:

Category II locations,and

Category III locations.

As you can see, homes with submersible pumps have

Category IV locations as well

Check your tester for safety ratingCheck your tester for safety rating

Safety



Three Possible Ways to Test Branch Circuits

1. Branch Circuit Integrity

• The physical structure of the branch circuit

2. Quality of the voltage supplied

• How connected equipment will perform

3. Profile the Loads on the Branch Circuit

• Measure the energy and the load on the circuit

We will examine the first and second of these in the time we have today.

Circuit Integrity



Test the physical structure of the branch circuit

• Connections to receptacles and devices

• Connections to panel

• Capacity of Hot and Neutral

Age, type, length and size of conductor

Quality of connections, splices, pigtails, bonds

• Integrity of Ground Conductor

HOW??

Circuit Integrity


Step 1: Test for correct wiring polarity

Step 2: Make voltage measurements

Step 3: Test for neutral / ground integrity

Step 4: Test Voltage Drop

Step 5: Measure circuit impedance

Evaluating Branch Circuit Structure



Common receptacle tester Detects, as go-no-go test,

Hot, Neutral and Ground

There can be < 100,000 ohms on the ground and a standard receptacle tester

with show the circuit to be OK

Step 1: Wiring Polarity Test



Step 2: Measure Voltage



Description Normal

Range

Comments

Line to Neutral RMS Volt

108 To 132 volts

Different standards apply

Neutral to ground RMS Voltage

Less than

0.5 volts

Some N-G voltage is normal




• SureTest indicates possible neutral to ground contact faults to within 15’ of the fault and 15’ from the panel.

• Looks for similar low resistance on ground and neutral conductor.

Step 3: Test for Bootleg or Neutral to ground Shorts



• General Purpose testers can’t identify a “False” or “bootleg” ground– Defined as an accidental

short or improper bonding of ground to neutral conductors

– Shows up as normally wired condition with general receptacle testers

– Sensed by the new AFCI breakers, will trip an AFCI

Test for Bootleg or Neutral to ground Shorts



Voltage Drop = V (no-load) – V (load)

% Voltage Drop = Voltage Drop/ V (no-load)

This way? Or This way?

Step 4: Measure Voltage Drop



• Measure the voltage drop at the furthest receptacle from the panel

• Low voltage drop indicates a low impedance system– Lowers the risk of hidden hazards– Improves power efficiency and operation

NEC code Articles {210-19(a) FPN No. 4} {215-2(d) FPN No. 2} - “Branch circuit conductors should be sized so as not to exceed a maximum voltage drop of 3% at the farthest outlet , and that the combined voltage drop for both a branch and feeder should not exceed 5%”

Using Voltage Drop



• Testing under a load and calculating voltage drop can identify common wiring problems– Undersized wiring for load or length of run

• NEC 210-19(a) FPN no.4 states that conductors be sized to provide reasonable efficiency of equipment operation

– High resistance connections

• Loose or corroded connections

• Poor splices

• Defective devices

• Voltage drop can detect an estimated 90% of defects on a branch circuit



The Philadelphia Housing Development Corporation)•Contractors must perform the 15-ampere-load test prior to insulating older row homes with blown insulation in attic and crawl spaces. •Smoldering fires had been associated with half a dozen installations. •The PHDC found that 70% of the homes flunked the 5% maximum voltage drop test with “a cluster around 6%”. •The PHDC arbitrarily established 10% as an unacceptable voltage drop, beyond which the contractor must repair/replace the circuit prior to proceeding with the insulation project. •(HUD recently adopted a similar requirement, according to reliable sources)

Practical Application for Voltage Drop testing



• Nor can they identify a neutral to ground bond– Glowing contacts in copper or

aluminum wiring

– High resistance in Back-wired devices like receptacle

– Loose or corroded connections

– Bad splices

– Hot plugs, or high resistance contact between outlet to plug.

A high resistance connection can result in hot spots or glowing connections which can breakdown insulation and create poor efficiency of the electrical system

General tester can not identify high resistance or series faults



Step 5: Measure the resistance of each conductor

Hot ConductorNeutral Conductor

Ground



• ASSC or Available Short Circuit Current

– Hot to Neutral ‘Ampacity’

– Hot/neutral/ground ‘Ampacity’

– A look at the energy available

ASSC, along with resistance of the conductors, and voltage drop, gives us a snapshot of

the entire circuit.


Voltage Performance Monitor

• What is a Voltage Performance Monitor?

• Why do I need to measure the integrity of the Voltage?

• What are the factors and features I need?



Two Steps to test the Voltage Performance of the branch circuit:

1. Perform Harmonic Analysis of Branch

2. Capture and Analyzer Voltage Events

Step 2: Voltage Performance



• Voltage performance?– Amplitude Must be measured over time.– Must meets some excepted standard– What would be a relevant Standards ?– How do we compare voltage over time to

these Standards?

What is Voltage performance?



• Eliminate sources of equipment failure

• Determine cause of voltage event using time stamps

• Determine if protective devices are effective

• Identify isolated or widespread problems

• Reduce Warranty Cost and Expense

What Can we do with the information



Each voltage waveform must be measured and compared to the standard:

If outside the range, timer starts, measures in cycles per second to the end of the event are taking.

• When an important event is detected, – The voltage of the event is logged– The duration of the event is logged– The day/date/time to the second of the event is logged

How do we compare voltage over time to these Standards



Key Points for comparison

• Only important events are logged

• Events are sorted by Time (log)

• Events are sorted by Type (event)

• Waveform shape is measured for THD


Voltage Performance Testing

What are these problems called?

•Sag – low voltage for brief periods (dips)

•Swell- high voltage for brief periods (surges)

•Voltage Transient- impulses (spikes)

•THD for Total Harmonic Distortion (noise)



What is good and bad voltage?– Sag and Swell limits

Note the use of Magnitude And Duration

Test the Quality of Voltage



• How does a standard say one thing, yet mean another? • Here is the actual wording from one real “Definition of Service”

regarding the application of ANSI C84:

ANSI C84

Range A

Fully Satisfactory

Performance on 120Vac

114V to 126V continuous

95% to 105% of nominal

ANSI C84

Range B

Acceptable Performance on 120Vac circuit

106V to 127V continuous

87% to 106% of nominal

What Utilities Promise: ANSI C84



• b.Exceptions to Voltage Limits (Ed.Note – ANSI C84)

• Voltage may be outside the limits specified when the variations:

• 1) Arise from the temporary action of the elements.

• 2) Are infrequent momentary fluctuations of a short duration.

• 3) Arise from service interruptions.

• 4) Arise from temporary separation of parts of the system from the main system.

• 5) Are from causes beyond the control of (power utility).

• c. It must be recognized that, because of conditions beyond the control of (power utility) or customer, or both, there will be infrequent and limited periods when sustained voltages outside of the service voltage ranges will occur. Utilization equipment may not operate satisfactorily under these conditions, and protective devices may operate to protect the equipment

What Utilities Deliver! Service Agreement



What Voltage Quality do we really need?



Power Quality problems are very expensive, but….

UNTIL NOW

•Power quality required very expensive analyzers

•Computers to set them up,

•Software to analyze

•Experts to review the data

Power Quality Monitors were too expensive for branch circuits



Testing Our Voltage Quality•No computer

•No software

•No setup

•Just the information you need



Measure at service entrance & points of connections

• IEEE 519 limits for voltage THD – < 5% for most facilities

– <3% for Hospitals and Airports

Total Harmonic Distortion



Transient VoltagesMeasure and record the time and voltage

Transients cause failure of communication control and datacom devices

Transients destroy insulation and capacitors

Determine if transient protection is working

(TVSS, SSDs)


Branch Circuit Test Pass/failComments

Line Voltage 108 – 132Low or high voltage will harm equipment.

% Voltage Drop@ 15 Amp. Load

<5.0% NEC Part. 210-19, FPN 4. Excessive voltage drop can cause fires. (test for 15 amp. Circuit)

% Voltage Drop@ 20 Amp. Load

<5.0% NEC Part. 210-19, FPN 4. Excessive voltage drop can cause fires. (test for 20 amp. Circuit)

Voltage between neutral and ground

< .5 Volts Higher voltages upset microprocessor operation. Can often be noise.

Phase Conductor Impedance

<.25 Ohms IEEE recommends less than .25 Ohms from any outlet to the building entry.

Neutral Conductor <.25 Ohms IEEE recommends less than .25 Ohms from any outlet to the building entry.

Ground Conductor Impedance

<.25 Ohms IEEE recommends less than .25 Ohms. Critical for proper operation of surge protection devices.

Branch Circuit Power Quality


THANK YOU FOR YOUR TIME AND ATTENTION

QUESTIONS PLEASE!

Application Guide to

Power Quality at the Plug

Documents

1 of 35 © 2007 Ideal Industries Power Quality At the Plug IDEAL INDUSTRIES Author: Brian Blanchette Application Guide to Power