DEICING OF TRANSMISSION LINE
Deicing of Transmission Line
Oct 15, 2014
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DEICING OF TRANSMISSION LINE
CONTENTS Introduction Methods Heating and mechanical deicing High frequency high voltage excitation Theory How to achieve uniform heating? Problems faced & methods of elimination Conclusion Reference
22
INTRODUCTION
In many cold regions of the world, transmission lines are subjected to atmospheric ice accumulation
Collapse of transmission line Repair expenses-high Emergence of deicing
3 3
PREVENTION OF ICE ACCUMULATION
METHODS
1)Heating and mechanical deicing [up to 245 kv]
2) High frequency, high voltage excitation [315-735 kv]
44
METHOD 1
Heating and mechanical deicing
Using rollers, conductor heatingUp to 245 kvNot widely used
55
METHOD 2
HIGH FREQUENCY HIGH VOLTAGE EXITATION
315-735 kv High frequency excitation of 8-200 KHz is
used for deicing Ice becomes a lossy dielectric & heats ice In addition skin effect causes resistive losses
&heating
66
System used in two different ways
1)Lines with chronic icing-system permanently attached to a section of line
2)Mounted to a truck & dispatched in an emergency to rescue a section of line
77
THEORY
Source of excitation current - high frequency high voltage power inverter 88
Coupling circuit connect inverter to transmission line
Functions of coupling circuit
o Low impedance path for high frequency excitation current
o Insulation between transmission line & inverter
Most appropriate configuration- series combination of capacitor & inductor
99
Capacitor- Voltage Insulation
Inductor along with capacitor- low impedance
Capacitor and inductor work in resonance
Trap- omit high frequency current prior entering HV substation
1010
STANDING WAVE
Two waves- equal magnitude, wavelength, sped, frequency
Move in opposite direction
Displacement of two wave add
Non traveling vibration
Oscillate up & down1111
ACHIEVING UNIFORM HEATING
High frequency power excitation produce standing waves unless line is terminated
Ice dielectric heating / skin effect resistive heating act alone
Uneven heating
1212
SOLUTIONS
SOLUTION 1 Terminate the line
Running waves are produced
Entail large energy flow
Energy greater than energy dissipation in ice
1313
DISADVANTAGE
Power capability of source increases
Termination- capable of dissipating/recycling the power
Expensive
Not used
1414
SOLUTION 2 Use standing wave
Apply two heating effect in complementary fashion
If magnitude in proper ratio-total heating is uniform
1515
1616
Total heating have ripple
Acceptable
Requires high total input power
Ripple free total heating- adjust frequency
1717
Frequency adjustment affects
1. Dielectric loss in ice2. Skin effect loss in conductor
1818
CONCLUSION
The application of high-frequency electric field to melting ice on power transmission lines appears promising. Combined dielectric heating & skin effect heating can be used to achieve uniform heating despite standing wave patterns.
2020
REFERENCE1. Sullivan C R “Breaking the ice driving power
transmission lines with high frequency, high voltage excitation”. IEEE Industrial Application Magazine vol.9 no”:5 PP 49-54
2. J.D. McCurdy, C.R. Sullivan, and V.F. Petrenko,“Using dielectric losses to de-ice power transmission lines with 100 khz high-voltage excitation,” in Conf. Rec. IEEE Industry Applications Society Annu. Meeting, 2001, pp. 2515-2519.Lawrence J “Frequency and time domain analysis” vol.32 Januvary 1996 IEEE .
3. J. Hu and C.R. Sullivan, “Optimization of shapes for round-wire high-frequency gapped-inducto windings,” in Conf. Rec. IEEE Industry Applications Society Annu. Meeting, 1998, pp. 900-906. 2121
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