First Trip

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First Trip
Jozef Levi Application Engineer Doble Engineering
Company
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Introduction

• What is First Trip?
• Definition
• What and how to monitor?

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What is First Trip?

• First Trip explanation
• Circuit breaker is mechanical device
• Require lubrication
• Recording of first operation after long idling
  with breaker in service

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Definitions

• Opening time
• Trip coil current
• Auxiliary contact
• Main arcing contact and contact separation
• Control voltage

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Opening time

• The opening time is interval of time from
  energizing of the opening release (opening coil)
  for circuit breaker in closed position and the
  instant when arcing contacts have separate in all
  poles

energizing
Last arcing contact separate
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Trip Coil Current
I
Maximum Current
(A)
imax2
Contact 52a Open
Change in inductance
Trip Latch Release
t0-t2 pick-up time
imax1
t1-t2 transient time
t2 armature hit stop
t0-t3 ON period
t3-t4 fall time
t
t2
t0
t1
t4
t3
(ms)
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Auxiliary switch

• Auxiliary contacts are contacts that show the
  circuit breaker position. At least one contact is
  used in each control circuit (trip/close) to
  control the coil supply.

• 52 a auxiliary switch
• S1 trip switch
• S4 selector switch
• Y1 trip coil

S1
S4
52a
Y1
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Main arcing contact and contact separation

• Contact separation during mechanical test

Opening time
Arcing contact parted phase A
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Main arcing contact and contact separation

• Contact separation during test with energized
  breaker

Arcing contact separation
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Control voltage

• Control voltage is a DC supply to control close
  circuit and trip circuits.
• The operating mechanism with his control circuit
  are designed for a rated control voltage but must
  operate throughout a specific voltage range due
  to variations in supply voltage
• Close circuit Min voltage 85 of rated voltage
• Close circuit Max voltage 110 of rated voltage
• Trip circuit Min voltage 70 of rated voltage
• Trip circuit Max voltage 110 of rated voltage

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Control voltage

• Control voltage drop during trip operation

Control voltage (V)
Time (ms)
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Control voltage and Trip Coil Current

• Voltage supply imperfection frequency 300 Hz

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What to monitor?

• Two basic approaches
• 1. Monitor large number of breakers
  distribution. Use of portable test device
  specifically developed for first trip testing.
• 2. Compare test results from same breaker
  transmission. Use of regular circuit breaker test
  instrument.

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Monitoring for comparison

• Use of circuit breaker test instrument

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Test Set-up
Circuit breaker in service
Test instrument
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Cable Connection
Main current measurement option l
Current probe in measuring transformer secondary
circuit
All connections are done in mechanism cubicle
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Cable Connection
Trip coil current measurement
Current probe in trip coil circuit
All connections are done in mechanism cubicle
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Test results

• Trip coil current, voltage supply and main current

Trip coil current
Supply voltage
Main current
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Test results

• Trip coil current

Initiation
Plunger stops
52 a opens
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Test results

• Main current

Contact separation at First Trip
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Test results comparison

• Main contact separation

t
Contact separation at First Trip
Initiation
Contact separation at mechanical test
t time difference 2.6 ms
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Test results comparison

• Third trip test

t
t time difference 2.6 ms
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Conclusion

• Easy to connect
• Results shows how breaker would perform in real
  situations
• Good for comparison with previous results

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