Field Testing
of
Electrical Power Equipment
Utilizing NETA Testing Standards
Shermco Industries Canada Inc.
What is NETA?
• NETA (International Electrical Testing Association) is
an association of leading electrical testing companies;
and visionaries committed to advancing the industry's
standards for power system installation and maintenance
to ensure the highest level of reliability and safety
• NETA Accreditation is not easy to attain. NETA
Accredited Companies earn their accreditation through a
rigorous application process conducted by the NETA
Association. This ensures that every NETA Accredited
Company provides testing services to the highest
standards of safety and reliability as specified by such
entities as: ASTM, CSA, EASA (Electrical Apparatus
Service Association), ICEA (Insulated Cable
Engineers Association) , IEEE, NEMA (National
Electrical Manufacturers Association), NFPA, and UL
and ULc.
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Section 7 of the NETA Testing Standards
Section 7, Inspection and Test Procedures in ATS (Acceptance Testing
Specs) and MTS (Maintenance Testing Specs)
•
The main body of the document, with specific information on what to do
relative to testing of electrical power equipment and systems
•
The specification is not intended to be a “how to test” document
•
There are four main bodies of information in Section 7:
A. Visual and Mechanical Inspection
B. Electrical Tests
C. Test Values – Visual and Mechanical
D. Test Values – Electrical
•
Optional Tests
– There are certain tests identified as “optional” with an asterisk
• Does another test provide similar information
• Cost of test versus data from similar tests
• How commonplace is the test
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Section 7 Common Tests Performed
Section 7, Inspection and Test Procedures in
ATS and MTS
Inspect bolted electrical connections for high
resistance using one or more of the following
methods:
1. Use of a low-resistance ohmmeter in
accordance with Section 7.[X]
2. Verify tightness of accessible bolted
electrical connections by calibrated torquewrench method in accordance with
manufacturer’s published data or Table
100.12.
3. Perform a thermographic survey in
accordance with Section 9.
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Section 7.1 Switchgear and Switchboard Assemblies
Key points in the standard
•
Clean the unit*
•
Inspect bolted connections
•
Confirm correct operation and sequencing of
mechanical and electrical interlocks*
•
Use appropriate lubrication on currentcarrying parts and on moving and sliding
parts*
•
Insulation resistance test
•
Dielectric withstand test
•
Test instrument transformers
•
Perform a system function test
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Section 7.1 Switchgear and Switchboard Assemblies
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Section 7.2 Transformers (Dry-Type)
Key points in the standard
• Clean the unit
• Inspect bolted connections
• Verify cooling fans operate correctly
• Verify the presence of surge arresters
• Insulation resistance test (Megger test)
• Insulation power-factor test (Doble test)
• Measure winding resistance
• Measure core resistance
• Test on as-found tap (MTS) or all taps
(ATS)
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Section 7.2 Transformers (Oil-Filled)
Key points in the standard
• Verify presence of PCB labeling
• Verify cooling fans/pumps operate
correctly*
• Verify the presence of surge arresters
• Verify operation of alarm, control, and trip
from auxiliary devices
• Test load tap changer (LTC)
• Insulation resistance test (Megger test)
• Insulation power-factor test (Doble test)
• Measure winding resistance
• Measure core resistance
• Test oil quality and DGA (dissolved gas
analysis)
• Test on as-found tap (MTS) or all taps
(ATS)
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Cooling Problems (Bird Nest)
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Cooling Problems (Defective Fan)
Even a few fan
failures degrade
the overall
cooling capacity
of the
transformer
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Cooling Problems (Oil Flow/Level)
• Oil level is
extremely
important for
proper cooling
• Oil fill line errors
• Continual DGA
and oil quality
testing can lower
oil levels over time
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Cooling Problems (Pad Leveling)
• Transformer pad
sinking causing oil
to only flow
through some
radiators
• Check for oil fill
line errors
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Tank Rupture with Oil Spill
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Key points in the standard (cable testing methods)
•
Dielectric Withstand
– Direct current (DC) dielectric withstand voltage
– Very low frequency (VLF) dielectric withstand
voltage
– Power frequency (50/60 Hz) dielectric withstand
voltage
• Diagnostic Tests
 Power factor/dissipation factor (tan delta) Ratio of
resistive component to capacitive component.
For good insulator this ratio would be quite low.

Power frequency (50/60 Hz)

Very low frequency (VLF)
• DC insulation resistance
• Partial discharge
– On line (50/60 Hz)
• Off line
– Power frequency (50/60 Hz)
– Very low frequency (VLF)
Field Testing Utilizing NETA Standards
Section 7.3
Cables
Tape Shielded
Wire Shielded
UniShield®
PILC
14
Cable Life Expectancy
•
Underground applications
– Under normal operating condition 30-35
years
•
In direct sunlight
– Under normal operating condition 25-30
years
•
Reducing Factors
– Improper handling during installation
• Bending radius
• Poor installation practice (pulling;
trench preparation)
• Mechanical damage to metallic or
extruded shield, jacket compromised
– Poor workmanship during installation of
stress relief devices and/or in-line splices
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Unshielded cable
tracking and arcing
to switchgear and
not properly routed
through current
transformer
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Section 7.4 Metal-Enclosed Busways
Key points in the standard
•
Confirm physical orientation
•
Insulation resistance test*
•
Dielectric withstand test*
• Minimum resistance values are for a
nominal 1000-foot busway run. Use
the following formula to convert the
measured resistance value to the
1000-foot nominal value:
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Section 7.4 Dielectric Withstand (Table 100.17)
Key points in the standard
Dielectric withstand test voltages
•
Isolated phase for generator
leads
•
Isolated phase for other than
generator leads
•
Non-segregated phase
•
Segregated
•
DC bus duct
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Section 7.5 Switches
Key points in the standard
• Perform a ground-fault test (low voltage)
• Verify cubicle space heater*
• Measure contact resistance across each
switchblade assembly
• Measure fuse resistance*
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Section 7.6
Circuit Breakers
Key points in the standard
•
Determine LT, ST, Inst, GF pickup (LV)
•
Ensure compliance with NEMA AB4 - Guidelines
for Inspection and Preventive Maintenance of
Molded Case Circuit Breakers Used in Commercial
and Industrial Applications
•
Test at final settings of coordination study
•
Slow-close breaker
•
Verify cell fit and alignment
•
Perform time-travel analysis
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Section 7.6 Circuit Breakers
A simple task
such as a visual
inspection can be
very revealing
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NETA Survey Results
•
In 2007 a survey of NETA Accredited
Companies was taken [Heid/Widup IEEE
ESW paper]
•
On average, 22% of the breakers tested in
the field had an issue affecting operation
•
Closely correlates with IEEE Std. 493 data to
“poor to fair” maintenance data.
(Recommended Practice for the Design of
Reliable Industrial and Commercial Power
Systems)
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Muscular Skeletal System: The Mechanism
•
A circuit breaker’s
muscular skeletal
system is the
mechanism
•
It is vital that this system
is well taken care of
•
Lubrication is key
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Corrosion of Mechanism
• Corrosion can have an
effect on opening times
• Increases incident
energy exposure
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Bearing Failure
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Dirty Mechanism
Will likely change the breaker’s opening time
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Galling of Silver Plating (lubrication)
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Poorly-Maintained Mechanism
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Section 7.9 Protective Relays
Key points in the standard
•
Determine pickup and dropout of
electromagnetic targets
•
Determine time delay at two points of the trip
curve
•
Learn the ANSI (American National Standards
Institute) relay number standard
•
Upgrade firmware (if applicable)
•
Relays can be complex, requires a very skilled
technician/engineer*
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Section 7.9 Relays (Example of Test Parameters)
21 Distance Relay
47 Phase Sequence Relay
•
•
Determine max torque angle and
directional characteristic
Determine positive sequence voltage
to close normally-open contact
25 Synch Check Relay
87 Differential Relay
•
•
Determine closing zone at rated
voltage
Determine the operation of each
restraint unit
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Section 7.10 Instrument Transformers
Key points in the standard
• Verify all required grounding and
shorting connections provide contact
• Perform a polarity test of each
transformer
• Perform an excitation test
• Perform a burden test
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Section 7.10 Instrument Transformers
Installation error
Unit not
commissioned
properly
Close to failure
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Section 7.11 Metering Devices
Key points in the standard
• Verify accuracy at cardinal points
• Verify instrument multiples
• Record passwords
• Download settings and compare to
specifications
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Section 7.12 Regulating Apparatus
Key points in the standard
• Record position indicator as-found,
minimum and maximum values
• Check motor and drive chain for correct
operation
• Verify indicator correctly identifies neutral
position
• Perform insulation power-factor test
• Remove oil sample from LTC (load tap
changer)
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Section 7.13
Grounding Systems
Key points in the standard
• Verify compliance with codes and
standards
• Perform fall-of-potential test (ground
resistance testing principle)
• Perform point-to-point tests
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Section 7.14 Ground-Fault Protection Systems, LV
Key points in the standard
•
Verify ground connection is on the source side
of the neutral disconnect link
•
Verify all phase conductors pass through
neutral in the sensor in the same direction
•
Verify grounding conductor does not pass
through zero sequence sensor
•
Perform testing by primary current injection
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Section 7.16 Motor Control Centers
Key points in the standard
• Test motor protective devices/relays
• Test circuit breakers
• Test electrical and mechanical interlocks
for proper operation
• Compare overload test data to motor
nameplate
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MCC Failure
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MCC Failure
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MCC Failure
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MCC Failure
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Section 7.17 Adjustable Speed Drives
Key points in the standard
• Ensure ventilation paths are clear
of debris
• Apply minimum and maximum
speed set points
• Test protective device functions
• Perform continuity test on bonding
conductors
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Section 7.18 Direct-Current Systems
Key points in the standard
• Verify ventilation system is operational
• Verify existence/ functionality of eye-wash
equipment
• Measure charger and equalizing and float
voltages
• Perform a load test
• Verify alarm indicators are functioning*
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When Good Electrical Systems Go Bad
This 100
amp
breaker is
worth
$5,000,000!
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Breaker Fed the Battery Charger
Battery
Charger
•
•
•
•
Field Testing Utilizing NETA Standards
The breaker would
not carry full-load
current
– Tripped at 45
amps in 70 to
90 seconds
The battery
charger had no
power
The batteries went
dead
No batteries, no
power for the
breaker trip coil
45
Loss of Production and Equipment
Total losses
for this $100
breaker
exceeded in
USD
$5,200,000
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The Winner and Still Champ!
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Section 7.22
Emergency Systems
Key points in the standard
•
The prime mover is not addressed in
the NETA testing standards
•
Perform insulation resistance tests per
IEEE 43 (Recommended Practice for
Testing Insulation Resistance of
Electric Machinery)
•
Verify correct functioning of governor
and regulator
•
Test protective devices
•
Test automatic transfer switches
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Frequency of
Maintenance Tests
Frequency of Maintenance Test: Why Do We Care?
• Equipment, like people, ages
• With time, environment, etc.
various factors affect overall
reliability
• Knowing when to test (and
when not to test) is critical
• Without proper maintenance
timing equipment and people
will suffer
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Influencing Factors
• There are many factors
influencing equipment safety and
reliability
• Not the least of which is when
you should perform maintenance
to achieve the highest reliability
• Additionally, other items affect the
overall equation for maintenance
frequency
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Equipment Criticality and Device Significance
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Current Condition of the Equipment
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Lubrication Life
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Maintenance History
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Operational History
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Industry Experience
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Maintenance Philosophy
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Operating Environment
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Time Allowed for Maintenance
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Manufacturer’s Recommendations
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Shermco Industries Canada Inc.
Mike Doherty – Director of Learning and Continual Improvement
Shermco Industries Canada Inc.
mdoherty@shermco.com
905-439-9329
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