Transcript power_quality_at_the.. - IDEAL INDUSTRIES, INC.

Power Quality At the Plug
IDEAL INDUSTRIES
Application Guide to
Power Quality at the Plug
Author: Brian Blanchette
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
Branch circuit
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
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www.idealindustries.com
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Branch Circuit Testing
Safety
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 rating
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
Circuit Integrity
Three Possible Ways to Test Branch Circuits
1.
Branch Circuit Integrity
•
2.
Quality of the voltage supplied
•
3.
The physical structure of the branch circuit
How connected equipment will perform
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.
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
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??
© 2007 Ideal Industries
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Branch Circuit Testing
Evaluating Branch Circuit Structure
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
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Test for correct wiring polarity
Make voltage measurements
Test for neutral / ground integrity
Test Voltage Drop
Measure circuit impedance
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Branch Circuit Testing
Step 1: Wiring Polarity Test
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
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www.idealindustries.com
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Branch Circuit Testing
Step 2: Measure Voltage
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Branch Circuit Testing
Description
Normal
Range
Comments
Line to Neutral
RMS Volt
108 To 132
volts
Different
standards apply
Neutral to
ground RMS
Voltage
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www.idealindustries.com
Less than
0.5 volts
Power Quality At the Plug
Some N-G
voltage is
normal
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Branch Circuit Testing
Step 3: Test for Bootleg or Neutral to
ground Shorts
• 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.
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
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
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
Step 4: Measure Voltage Drop
This way?
Or
This way?
Voltage Drop = V (no-load) – V (load)
% Voltage Drop = Voltage Drop/ V (no-load)
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
Using Voltage Drop
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%”
• 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
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
• 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
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
Practical Application for Voltage Drop testing
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)
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Testing
General tester can not identify high
resistance or series faults
• 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.
© 2007 Ideal Industries
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A high resistance
connection can result in hot
spots or glowing
connections which can
breakdown insulation and
create poor efficiency of the
electrical system
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Branch Circuit Testing
Step 5: Measure the resistance of each
conductor
Hot Conductor
Neutral Conductor
Ground
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Branch Circuit Testing
• 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.
© 2007 Ideal Industries
www.idealindustries.com
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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?
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Voltage Performance Monitor
Step 2: Voltage Performance
Two Steps to test the Voltage Performance of
the branch circuit:
1. Perform Harmonic Analysis of Branch
2. Capture and Analyzer Voltage Events
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Voltage Performance Monitor
What is 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?
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Voltage Performance Monitor
What Can we do with the information
• 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
© 2007 Ideal Industries
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Voltage Performance Monitor
How do we compare voltage over time to these
Standards
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
© 2007 Ideal Industries
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Voltage Performance Monitor
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
© 2007 Ideal Industries
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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)
© 2007 Ideal Industries
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Voltage Performance Monitor
Test the Quality of Voltage
What is good and bad
voltage?
– Sag and Swell limits
Note the use of
Magnitude And
Duration
© 2007 Ideal Industries
www.idealindustries.com
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Voltage Performance Monitor
What Utilities Promise: ANSI C84
ANSI C84
Range A
ANSI C84
Range B
•
•
Fully
Satisfactory
Performance on
120Vac
114V to 126V
continuous
95% to 105% of
nominal
Acceptable
Performance on
120Vac circuit
106V to 127V
continuous
87% to 106% of
nominal
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:
© 2007 Ideal Industries
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Voltage Performance Monitor
What Utilities Deliver! Service Agreement
•
•
•
•
•
•
•
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).
© 2007 Ideal Industries
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•
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
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Voltage Performance Monitor
What Voltage Quality do we really need?
© 2007 Ideal Industries
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Voltage Performance Monitor
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
© 2007 Ideal Industries
www.idealindustries.com
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Voltage Performance Monitor
Testing Our Voltage Quality
•No computer
•No software
•No setup
•Just the information you need
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www.idealindustries.com
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Voltage Performance Monitor
Total Harmonic Distortion
Measure at service entrance &
points of connections
• IEEE 519 limits for voltage
THD
– < 5% for most facilities
– <3% for Hospitals and
Airports
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Voltage Performance Monitor
Transient Voltages
Measure 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)
© 2007 Ideal Industries
www.idealindustries.com
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Branch Circuit Power Quality
Comments
Branch Circuit Test
Pass/fail
Line Voltage
108 – 132
% 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.
© 2007 Ideal Industries
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Low or high voltage will harm equipment.
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THANK YOU FOR YOUR
TIME AND ATTENTION
Application Guide to
Power Quality at the Plug
QUESTIONS PLEASE!
© 2007 Ideal Industries
www.idealindustries.com
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