PowerPoint 프레젠테이션 - School of Engineering and Applied
Download
Report
Transcript PowerPoint 프레젠테이션 - School of Engineering and Applied
Study SF6 Thermal Plasma generated
during/after power interruption
Final Project for Introduction to Plasma Processing
Instructor: Prof. Kasra Etemadi
STUDENT:
Hosny, Ahmed A.
EE403/503, Fall 2005
1
Outline
Introduction
Plasma characteristics
Advantages and Disadvantages of SF6
Residual SF6 plasma species
Gas Insulated Switchgear (GIS)
Conclusion
Future work
References
Hosny, Ahmed
2
What is Circuit Breaker (CB)?
CB is one of the most essential
safety mechanisms in electric
networks.
Interrupt short circuit currents
(~ 60kA, low pf ~ 0.1).
Fault clearance time is very
important for power system
stability and avoid equipment
damage for itself and the rest of
the network.
CB can be characterized by,
short circuit current, Rated
voltage, …
Electric
Subcircuit
A
V,
I
Circuit
Breaker
(CB)
ON/Off
V,
I
Electric
Subcircuit
B
Figure 1: A schematic of Circuit
Breaker Conditions
Hosny, Ahmed
3
Plasma Elements…
+
+
+
+
Coupling
Impulse Voltage,
Transient Recovery
Voltage (TRV)
+
+
Breakdown
Gas ( SF6)
+
+
+
Extinguish
Manmade
Plasmas
Figure 2: A plot shows plasma elements.
Hosny, Ahmed
4
Plasma Parameters…
104
D 69
101
100
Interstellar
Gas
Gaseous
Nebulae
Ionosphere
Glow
Discharge
MHD
Generator
P = 1 THz
P = 10 GHz
P = 100 MHz
P = 10 KHz
Solar
Corona
P = 1 MHz
Electron
Beam
103
102
Debye Length
Thermonuclear
Plasmas
P = 100 Hz
Average Electron Energy, [eV]
105
Arc
Discharge
Te
ne
[m]
Plasma Frequency
p 8.97 ne
Solid
10-1
100 102 104 106 108 1010 1012 1014 1016 1018 1020 1022 1024
Electron Number density, [cm-3]
Hosny, Ahmed
5
Plasma … Power Source
Transient Recovery Voltage (TRV)
TRV is the voltage that builds up across
a circuit breaker after the interruption of
a fault current.
It consists of oscillations of lumped
elements and of traveling waves.
It stresses the circuit breaker contacts
and depends on the type and location of
the fault in addition to the CB it self.
di 1
Ri L idt E cos t
dt c
Rt
er E cos t exp
cos 0t
2L
0 1
Lc
Figure 3: (a) Single-phase equivalent circuit,
(b) Transient recovery voltage [10]
Hosny, Ahmed
6
Arc Quenching Mechanism
Figure 4: A Schematic representation of the puffer interrupter
indicating some important physical processes. [2]
Hosny, Ahmed
7
Pros & Cons of SF6
SF6 has a dielectric strength of about two to three
times that of air.
It is nontoxic.
It is nonflammable.
It is noncorrosive; it doesn’t react with other
materials because it is inert gas. However, when it
is heated to 5000C it decomposes and its
decomposition products react with other
materials.
It exhibits excellent properties for arc quenching.
So, it used as an interrupting medium in circuit
breakers instead of air or oil.
Hosny, Ahmed
8
SF6 Circuit Breaker
Figure 6: SF6 Circuit breaker,
Figure 5: A plot of the thermal
36kV, 4000A, SC 50kA. [12]
conductivity of SF6 and N2 [11]
Hosny, Ahmed
9
Residual SF6 Plasma Species
Ionization
e F F ee
e S S ee
Associative detachment
F F F2 e
F S SF e
Dissociative attachment
F2 e F F
SF e F S
Table 1: Particle densities of
residual SF6 plasma at 3000 K,
105 Pa [1]
Hosny, Ahmed
10
Electron Velocity Distribution Function
Normalization Factor
Energy loss due to collisions
Collision frequency
Hosny, Ahmed
11
SF6CB applications … GIS
Advantages of Gas-insulated
switchgear (GIS) are:
Compact size.
Totally
isolated
from
the
atmospheric conditions such as
air pollution, high temperature,
snow, etc.
High degree of reliability and
safety precaution.
Easy to install.
SF6 has a dielectric strength
much higher than air which is the
insulated gas for conventional
switchgear type.
Figure 7: Gas-insulated substations
(the picture shows a typical example)
are very compact in size and reliable in
operation
Hosny, Ahmed
12
Conclusion
The primary Cause of high transient over-voltage
is the generation of multiple re-ignitions during
the interrupting period by some types of CB. This
TRV are the most likely cause of CB damage.
The design of CB can be determined using the
thermal flow characteristics near current zero.
The critical field strength for the breakdown of
the residual plasma has been found to be
proportional to the pressure and is equal to
2.0V/(m.Pa), which is only ~ (1/45)th of that of SF6
at room temperature.
Hosny, Ahmed
13
Future Work
Further study on calculation of TRV and
post-arc current just after current zero.
Advanced arc model and measurement
techniques, which can support the physical
phenomena in CBs.
Study the theory of positive corona in SF6
due to impulse voltage.
Hosny, Ahmed
14
References
1.
2.
3.
4.
5.
6.
J.D. Yan, M.T.C. Fang and Q.S. Liu, “Dielectric Breakdown of a Residual
SF6 Plasma at 3000K under Diatomic Equilibrium”, IEEE Transaction on
Dielectrics and Electrical Insulation, Vol. 4 No.1, February 1997.
D.W. Shimmin and et al, “Transient Pressure Variations in SF6 Puffer
Circuit breakers”, Applied Physics, 23 (1990) pp. 533-541.
P.H. Schavemaker and L. Van der Sluis, “ The influence of the Topology of
Test Circuits on the Interrupter Performance of Circuit Breakers”, IEEE
Transaction on Power Delivery, Vol. 10, No. 4, October 1995.
M. T. C. Fang and M. Y. Shent, “A comparative study of two computational
methods for the simulation of discharge development in SF6”, Appl. Phys.
28 (1995) 364-370.
Z. Ma and et al, “ An Investigation of Transient Over voltage Generation
when switching high voltage shunt reactors by SF6 circuit Breaker”, IEEE
Transaction on Power Delivery, Vol. 13, No. 2, April 1998.
Jong-Chul Lee and Youn J. Kim, “ Numerical Modeling of SF6 thermal
plasma generated during the switching process”, Science Direct,
Elsevier, 2005, pp. 72-80.
Hosny, Ahmed
15
References (Cont.)
7.
8.
9.
10.
11.
12.
Richard Morrow, “ Theory of Positive Corona in SF6 Due to a Voltage
Impulse”, IEEE Transaction on Plasma Science, Vol. 19, No. 2, April
1991.
J. D. Yan, M. T. C. Fang and Q. S. Liu, “Dielectric Breakdown of a
Residual SF6 Plasma at 3000 K under Diatomic Equilibrium”, IEEE
Transaction on Dielectrics and Electric Insulation, Vol. 4, N0. 1,
February 1997.
Gerd Duning and Manfred Lindmayer,” Plasma Density Decay of
Vacuum Discharge After Current Zero”, IEEE Transaction on Plasma
Science, Vol. 27, No. 4, August 1999.
Mazen Abdel-Salam and et al, High-Voltage Engineering: Theory and
Practice, Marcel Dekker, Inc., New York, 2000
http://www.metatechcorp.com/aps/cold_weather_operating_problem
s_.htm.
http://www.abb.com/global/abbzh/abbzh251.nsf!OpenDatabase&db=/
global/seitp/seitp328.nsf&v=9AAC720001&e=us&c=C1256CCB004E3
ABBC125699F0042734E.
Hosny, Ahmed
16