circuit breaker testing & maintenance - home -...
TRANSCRIPT
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Circuit Breaker Testing & Maintenance Ken Elkinson Doble Engineering Co. May 2014
Proprietary & Confidential © 2012 Doble Engineering Company. All rights reserved.
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Agenda
• Why Test? • Types of Testing
– Timing – PF – Dielectric Quality – Inspections (V&O)
• Online Monitors • Operational
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Background Perspective
• Newly installed breakers operate for 30+ years • Under ‘normal’ conditions most breakers are operational for: less than 10 minutes in 30 years • Under ‘abnormal’ conditions most breakers are operational for less than 1 minute in 30 years
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Reasons for Testing
• Part of a comprehensive diagnostic maintenance program
• Find early indications of possible problems
• Prevent problems rather than pick up pieces
• Build up a test record database for trending
• Pick out the bad actors – Asset Management
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Reasons for Testing (cont’d)
Performing Timing Tests is the best way to: • Verify the control circuit • Check motion of the moving parts • Validate time of operation – verify manufacturer specs • Determine contact wear • Demonstrate results of maintenance • Assess overall breaker capability
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Before test start
• Circuit breaker design • What is breaking medium? • What is contact system design? • What kind of mechanism operate the breaker?
We have to know how testing breaker works
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Circuit breaker design
Dead tank breaker
Breaking element W MF-3A
Cross section
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Circuit Breaker Design
• Different breaker types will produce different data – SF6 – OCB – Live Tank – Vacuum – Air
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Trip Coil Current
S1
S4
52a
Y1
K9 K9
BD
TRIP/CLOSE leads connected
0 1
52a
ST
0 1
time ms
ST
V
I (A)
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Trip Coil Current
S1
S4
52a
Y1
K9 K9
BD
ST
V Test initiation
Safety switch closed
0 1
52a
ST
0 1
time ms
I (A)
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Trip Coil Current
S1
S4
52a
Y1
K9 K9
BD
ST
V
Current flows through trip coil
0 1
52a
ST
0 1
time ms
I (A)
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Trip Coil Current
0 1
52a
ST
0 1
time ms
52a
Y1
K9 K9
ST
V
S1
S4
K9 K9
BD
I (A)
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Trip Coil Current
0 1
52a
ST
0 1
time ms
52a
Y1
K9 K9
ST
V
S1
S4
K9 K9
BD
I (A)
66 ms
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Test results analyzing examples
• We must know the definition of what we are measuring and/or monitoring
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Maximum Current
Contact 52a Open
Trip Coil Current
t (ms)
I (A)
t2 t0 t1 t3 t4
imax2
imax1
t0-t2 pick-up time t1-t2 transient time
t0-t3 ON period t3-t4 fall time
t2 armature hit stop
Change in impedance
Plunger stops
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Contact 52a Open
Trip Coil Current
t (ms)
I (A)
t2 t0 t3
Plunger stops Three important moments of trip coil current
Voltage applied
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Trip Coil Current
• Voltage supply imperfection
t – opening time difference 1.7 ms
t
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Trip coil current – First Trip
• Auxiliary contact 52a used as trigger
Trip coil current
Power supply
52a
t
t = 100 ms pre recording time
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Trip coil current – First Trip
• Over laid results
Trip coil current during first trip Trip coil current after multiple operations
t
t = time difference 52a
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Trip coil current – First Trip • From the data captured in the First Trip
test the following problems can be identified: – Mechanism lubrication deficiencies – Trip coil damage – Auxiliary contact problems (dirty, burned,
etc…) – Loose connections in mechanism – Station battery and/or battery charger
problems – Control cable sizing and contamination issue
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T-Doble – Metrics (cont’d)
Comparing with test plan values: Pass/Investigate
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“Instant” Velocity Diagram
Travel
Trav
el (i
n)
Travel
Velocity
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“Instant” Velocity Diagram
Travel
Trav
el (i
n)
Travel
Velocity
Sharp velocity change
Travel reach for first time open position
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“Instant” Velocity Diagram
Travel
Trav
el (i
n)
Travel
∆X
∆t Shock absorber travel Shock Absorber Time
Velocity
∆X ∆t
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Timing diagram
arcing contact with low pressure
arcing contact with low pressure bounce
Timing Result Close Operation
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voltage drop on contact in motion
Timing main contacts
Bounce
CLOSE
Impedance change
0 1
Time (ms)
OPEN
Timing diagram
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Timing diagram
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Main contact timing
Timing diagram
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Power Factor Tests • mA, W, % PF • TLI (for oil breakers) • Rating • Bushing Tests
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Dielectric Quality • Obviously will depend on the type of
dielectric in breaker – SF6 breaker test for moisture, pressure,
density
– Oil breaker test for oil quality
– Vacuum breakers will require vacuum bottle to be tested
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Dynamic Resistance Measurement
• Detecting overlapping arcing with main contacts • Injecting DC current • Using external power source (12 V car battery) • Trip Free or C – delay – O • Measuring voltage drop during breaker
operation
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Online Monitors
• Measure Insulation Quality (SF6)
• Circuit Breaker Timing – Similar measurements
to offline testing
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Online Monitoring
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Operational Data
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Operational Data • Visual & Operational Inspections
– Reading gauges – Maintenance records – Information on breaker operating mechanism
• Counters – Tracks number of breaker operations – Important to note not all operations on
counter are due to faults, but the ones that are take a toll
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Goal • To avoid…
• Questions?