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Yoshino T. et al.: Experimental Study on Rotary Arcs in CO2 Model Gas Circuit Breaker
Plasma Physics and Technology
2015, 2, 2, 211-214
Experimental Study on Rotary Arcs in CO2 Model Gas Circuit Breaker
Yoshino T.1, Kawano H.1, Mori T.1, Miyazaki K.1, Fujino T.2
1TOSHIBA Co., 2-1 Ukishima-cho Kawasaki 210-0862, Japan, [email protected] 2University of Tsukuba, 1-1-1 Tennnodai Tsukuba 305-8577, Japan, [email protected]
The present study has examined the influence of rotary arcs with a permanent magnet in CO2 gas circuit
breaker under conditions of low and high current interruption. The rotary arc extremely increases extinc-
tion peak and decreases arc conductance of 200ns before current zero in the case of low current condition,
because the rotary arc generates the rotation gas velocity and enhances turbulent energy transport, when
there is no pressure rise of thermal puffer in the case of low current.
Keywords: rotary arc, CO2, GCB
1 INTRODUCTION
SF6 gas has been used in most high-voltage
transmission and distribution network because
of its remarkable arc quenching properties,
dielectric insulation and ease in handling.
However, the SF6 gas has a potential of sig-
nificant environmental impacts if it leaks into
the atmosphere. CO2 gas is expected as a one
of the alternative solutions to SF6 gas [1].
The arc quenching properties of CO2 gas is
inferior to that of SF6 gas. One of the ideas for
the improvement of current interruption capa-
bility in Gas Circuit Breakers (GCBs) is to
rotate arcs by electromagnetic force [2-5]. By
the rotation, the arc is expected to be cooled
by fresh gas, and hot gas is expanded rapidly
and raises gas pressure of a thermal puffer.
But rotary arcs in CO2 gas have not been in-
vestigated in detail.
Authors have been conducted current interrup-
tion test with and without a magnet in CO2
gas, and examine the feasibility of application
of rotary arcs to CO2 gas circuit breaker.
2 EXPERIMENTAL SETUP
Figure 1 shows a schematic figure of a model
chamber used in this study. The interruption
chamber has a movable arcing contact and a
stationary arcing finger. The stationary arcing
finger is set in a thermal puffer which does not
have a mechanical puffer. A permanent mag-
net is set around the stationary arcing finger
concentrically. A disc electrode, called an arc-
runner, is set at the front of the stationary arc-
ing fingers with which the arc-runner is con-
nected in parallel electrically.
When the movable arcing contact is driven
and detached from the stationary arcing fin-
gers, an arc ignites between the stationary arc-
ing finger and the movable arcing contact, and
then the arc is expected to transfer from the
arcing finger to the arc-runner.
The permanent magnet is of Nd-Fe-B. The
magnet is coated with aluminum, and the
coated magnet is set in a case made of PTFE
to protect the magnet from hot gas or arc itself.
The maximum magnetic flux density of radial
component on the surface of the arc-runner is
about 0.14T.
Interruption current is supplied by a short-
circuit generator, and its magnitude is set to
values of 4.5 and 40kA peak. The arc voltage
is measured by a voltage divider, and the cur-
rent is measured by Rogowski coil [6]. Pres-
sure in the thermal puffer is measured by a
pressure transducer as shown in Fig. 1.
The tank is filled with CO2 gas. The gas pres-
sure is 0.5MPa-abs. Experiments have also
performed for a chamber without a magnet for
comparisons.
Pressuretransducer
Thermal puffer(About 500cc)
Arcingfinger
Arc-runner
Nozzle
Movablearcing contact
PermanentMagnet
Tank
f16
Fig.1: Schematic figure of model chamber
Yoshino T. et al.: Experimental Study on Rotary Arcs in CO2 Model Gas Circuit Breaker
212
3 RESULTS AND DISCUSSIONS
3.1 LOW CURRENT CONDITION
(4.5kA peak)
Figure 2 shows arc voltage waveforms with
and without the magnet in low current condi-
tions of about 4.5kA peak. The arcing time is
about 26ms, and current zeros exist at around
8ms and 17ms. High frequency oscillation is
observed on the arc voltage in the case with
the magnet, while it cannot be observed with-
out the magnet. Arc voltage with the magnet is
higher than that without in almost all time dur-
ing arc discharge. In particular, the extinction
peaks increase drastically at every current ze-
ros by applying the magnetic field.
Figure 3 shows the pressure rise in thermal
puffer with and without the magnet. The pres-
sure rise is no more than several tens of kPa
for both cases. It seems that there is little gas
flow between contacts in low current condi-
tions.
-10
-8
-6
-4
-2
0
2
4
6
8
10
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Cu
rre
nt,
kA
Arc
vo
ltag
e, k
V
Time, ms
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
Arc
vo
ltag
e [k
V]
10
8
6
4
2
0
-2
-4
-6
-8
-10
Cu
rren
t [k
A]
-4 0 4 8 12 16 20 24 28Time [ms]
With magnet (26.6ms)
Without magnet
(25.8ms)
Current
Fig.2: Example of arc voltage waveforms with and
without magnet (4.5kA)
100
50
0
-50
Pre
ssu
re r
ise
[kP
a]
Cu
rren
t [k
A]
-10 0 10 20 30 40Time [ms]
With magnet (26.6ms)
Without magnet(25.8ms)
Current
10
5
0
-5
Fig.3: Pressure rise in thermal puffer with and
without magnet (4.5kA)
Figure 4 depicts current-voltage characteristics
with and without the magnet under conditions
of various arcing times. The extinction peaks
are clearly observed in every arcing time con-
ditions when the magnetic field is applied.
However, it can be found from Fig. 4 (a) that
the extinction peak cannot be observed with-
out the magnet. This means that turbulent en-
ergy transport is weak around the current zero.
It seems that the gas flow keeps laminar and
does not become turbulent without magnet.
The rotary arc generates the rotation gas ve-
locity, and increases turbulent energy transport.
Therefore, arc cooling around current zero is
enhanced drastically, and the extinction peak
arises by applying the magnetic field, as
shown in Fig. 4 (b).
1
0.8
0.6
0.4
0.2
0
Arc
vo
ltag
e [k
V]
10-3 10-2 10-1 100 101 102 103 104
Current [A]
11.0ms
16.6ms
25.8ms
19.6ms
8.2ms
7.5ms
1
0.8
0.6
0.4
0.2
0
Arc
vo
ltag
e [k
V]
10-3 10-2 10-1 100 101 102 103 104
Current [A]
9.7ms
9.4ms
14.2ms
17.6ms
26.6ms
(a): without magnet
(b): with magnet
Fig.4: Current-voltage characteristics under
various arcing time conditions (4.5kA)
Yoshino T. et al.: Experimental Study on Rotary Arcs in CO2 Model Gas Circuit Breaker
213
3.2 HIGH CURRENT CONDITION
(40kA peak)
Figure 5 shows arc voltage waveforms with
and without the magnet in high current condi-
tions of about 40kA peak. The arcing time is
about 21ms. There are few frequency oscilla-
tions in arc voltage for both cases of with and
without the magnet. The voltage rising by ap-
plying the magnetic field is observed in first
half-cycle before 12ms. The extinction peak
with the magnet also increases around 12ms.
On the other hand, the voltage rising including
extinction peak by applying the magnetic field
cannot be observed in second half-cycle after
12ms.
Figure 6 shows the pressure rise in thermal
puffer with and without the magnet. The max-
imum value of pressure rise with the magnet
increases to the same extent as that without.
There is the influence of magnet for the pres-
sure rise at shorter arcing time before 12ms.
1.2
0.8
0.4
0
-0.4
-0.8
-1.2
Arc
vo
ltag
e [k
V]
60
40
20
0
-20
-40
-60
Cu
rren
t [k
A]
0 4 8 12 16 20 24Time [ms]
With magnet (19.6ms)
Without magnet(21.2ms)
Current
Fig.5: Example of arc voltage waveforms with and
without magnet (40kA)
1.2
1.0
0.8
0.6
0.4
0.2
0
-0.2
Pre
ssu
re r
ise
[P.U
.]
Cu
rren
t [k
A]
-10 0 10 20 30 40Time [ms]
With magnet(19.6ms)
Without magnet(21.2ms)
Current
100
50
0
-50
Fig.6: Pressure rise in thermal puffer with and
without magnet (40kA)
Figure 7 illustrates the current-voltage charac-
teristics with and without the magnet under
conditions of various arcing times. The extinc-
tion peak at the shorter arcing time of 10 to
15ms becomes higher by applying magnetic
field. However, there is no effect of the mag-
net at the longer arcing time over 17ms.
It can be found from Fig. 7(b) that voltage os-
cillations occur in arc discharge below several
kA of current by applying magnetic field, but
there are no oscillations above 10kA. This is
likely due to the difference in arc structure. No
oscillation of arc voltage occurs in high cur-
rent duration above 10kA because the cylin-
drical stable arc structure is formed. The arc
discharge becomes spiral structure and spiral-
shaped arc yields the destabilization of arc
voltage when the arc current is reduced below
several kA.
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Arc
vo
ltag
e [k
V]
10-3 10-2 10-1 100 101 102 103 104 105
Current [A]
12.0ms
16.8ms
21.8ms
11.6ms
6.7ms
21.2ms
Arc
vo
ltag
e [k
V]
Current [A]
10.4ms
15.0ms
8.4ms
17.5ms
6.5ms
10-3 10-2 10-1 100 101 102 103 104 105
1.4
1.2
1
0.8
0.6
0.4
0.2
0
19.6ms
destabilization
stabili-zation
(a): without magnet
(b): with magnet
Fig.7: Current-voltage characteristics under
various arcing time conditions (40kA)
Yoshino T. et al.: Experimental Study on Rotary Arcs in CO2 Model Gas Circuit Breaker
214
3.3 COMPARISON OF ARC
CONDUCTANCE
Figure 8 shows the arc conductance of 200ns
before current zero (G-200) with and without
the magnet under low and high current condi-
tions. The G-200 is reduced by applying mag-
netic field for every current and arcing time
conditions. In the case of low current condi-
tion, the G-200 is significantly reduced at
shorter arcing time around 10ms. G-200 with
the magnet becomes also lower in the case of
high current conditions.
Arc
co
nd
uct
ance
[m
S]
Arcing time [ms]
5 10 15 20 25 30
100
10
1
0.1
0.01
With magnet
Without magnet
(a): Low current condition (4.5kA)
Arc
co
nd
uct
ance
[m
S]
Arcing time [ms]
5 10 15 20 25 30
With magnet
Without magnet
(b): High current condition (40kA)
Fig.8: Arc conductance of 200ns before current
zero in high and low current conditions
As mentioned above, the CO2 gas flow is dif-
ficult to become turbulent because CO2 gas
has the small mass number compared to the
SF6 gas. The rotation gas velocity by applying
the magnetic field increases the turbulent en-
ergy transport. Therefore, the influence of ro-
tary arcs is greatly enhanced under the condi-
tion of no pressure rise in thermal puffer such
as low current condition in gas circuit breaker
with CO2 gas.
4 CONCLUSIONS
The present study has examined the influence
of rotary arcs with a magnet in CO2 gas under
conditions of low and high current interruption.
Conclusions are as follows.
The rotary arc extremely increases extinction
peak and decreases arc conductance of 200ns
before current zero in the case of low current
condition in CO2 gas. The CO2 gas flow is
difficult to become turbulent because of the
small mass number. The rotary arc by apply-
ing magnetic field generates the rotation gas
velocity and turbulent energy transport, when
there is no pressure rise in thermal puffer.
Therefore, it is expected that the current inter-
ruption capability of CO2 gas is drastically
improved by the magnet in low current condi-
tion of CO2 gas circuit breaker.
REFERENCES
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Thermal interruption capabilities of CO2 gas and
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78-81.
[2] Sasao H, Hamano S, Wada Y, Hasegawa H,
Kobayashi N, Development of a magnet-assisted
autopuffer GCB, IEEE 90 WM 158-6 PWRD,
1990.
[3] Young K A, Spencer J W, Optical diagnostics
for studying a rotating arc in SF6 gas, In: 14th Int.
Conf. on Gas Discharges and their Applications,
Vol.II, 2002, 353-356.
[4] Ennis M G, Investigation of Fundamental Pro-
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