Electrical Engineering. The Inside Story. Overview of AC Power Unit. Carla L. Hoyer E3 Texas A&M University Summer 2003. Ocean: Unit Topic Green: Teacher-Led PP Pink: Student Activity and Assessment. Electrical Engineers. Improve our lives by: Generating Electrical Power
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The Inside Story
Carla L. Hoyer
Texas A&M University
Green: Teacher-Led PP
Pink: Student Activity and Assessment
Improve our lives by:
During the operation of the transformer, insulation inside deteriorates. When the gradual aging gets more severe, arcing discharge or incipient fault may occur. This may cause a short circuit between the adjacent turns of primary or secondary winding leading to a catastrophic failure. This catastrophic failure may damage other equipment, buildings and even people near the transformer. Therefore, it is desirable to develop a method that detects any unusual current activities in the primary or secondary winding of the transformer before they become destructive and damage the transformer.
The situation of degraded insulation in the transformer before short circuit and failure occurs is referred to as an Incipient Fault.
Internal heating due to overloads
Excessive Voltage gradient
Short circuit and centrifugal forces
Why Detect Incipient Faults?
Comparison to DC
AC and DC Power – what’s the difference?
Batteries are a source of DC Power
= -nF(+1.5V), so
ε = +1.5V
ε = +1.5V
Is Alternating Current
also a one-way street?
Let’s do some Science…
Alternating Current Lab
DC Voltage, Current and Light Intensityare INDEPENDENT of time
Next Class: How do they get AC current to ‘cha-cha’?
The Electron Cha-Cha
And Magnetic Magic
Photo of Lab Setup
Electromagnetic Induction and The Transformer
Power (watts) = VI
Ohm’s Law: V = IR (In AC, V=IZ)
Substituting: P= IRI
Simplifying: P= I2R
P = f (I,R)
Due to the Resistance in the Transmission Line, The voltage (∆V=IR) will drop during the trip:
Voltage Sent = Volts Lost + Volts Needed
= IR + Volts Needed
= 2000V + 120 V= 2120V
Power Lost = Power Sent - Power Received
Power Received = VI = (120V)(1000amp)
= 120,000 watts
Power Sent = VI=(2120V)(1000amp)
= 2,120,000 watts
Power Lost = 2,120,000 watt -120,000 watt
= 2,000,000 watt ( 94% lost!)
What Can We Do?
∆V = IR = (2amp)(0.1ohm/mi)(20mi)
= only 4V lost
Power loss = (4V)(2amp)= 8 watts
NEGLIGIBLE POWER LOSS WITH LOW AMPS
The Relative Number of Turns Dictates the Output Current and Voltage
AC Allows Efficient Transmission
Westinghouse, Edison and the Electric Chair
Find specific pattern unique to failing research transformer first
THE NOTES ARE IMPORTANT
Then, Find that pattern in live data
Unique Pattern- Irregular Waveform
followed by spike