Upload
akjmv
View
542
Download
50
Embed Size (px)
Citation preview
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