40
GASTUBE
ARRESTER
Gas tube arrester(GTA)is a surge absorber
featuring low capacitance and high surge
absorption energy.
lt consists of a sealed tube in which inert
gas is injected and electrodes which are
set at fixed intervals. The simple structure
and the dimensional accuracy offer high
reliability and stabilized characteristics.
Applications
Maximum Single lmpulse Dischrge Current
Capacitance
Operating Temperature Range
DC Holdover Voltage
Impulse Waveform
1. Protection for telephone set, facsimile, telex,
telephone system, CATV, computer and peripheral
equipment.
2. Semiconductor circuit protection in equipment
that also uses high voltage such as TV,
oscilloscope, and electron microscope.
3. Automatic control of luminous energy in
stroboscopic tube.
4. Generator of high-voltage for gas igniter.
Voltage-Current Characteristics
Electrical Characteristics
AC Discharge Current
lmpulse Surge Life
lnsulation Resistance
DC Breakdown Voltage
Impulse Breakdown Voltage
The current through the GTA is changed over the
range of values of 10 18 to 102 amps which is shown
as the figure below and the voltage across the GTA will
also valy.The discharge characteristics are changed to
various mode by the flowing current, and the final
mode of the discharge characteristics is arc discharge .
When the applied voltage across the GTA exceeds
the breakdown voltage (sparkover voltage), the
current through the GTA increases rapidly to value
of several amps or greater. The rate of current rise and
level to be reached are limited by the series impedance
of the circuit.The voltage across the GTA at this
time is very low with typical value of 20 to 30 volts.
The current is the rms value of sinusoidal alternating
current of 50Hz or 60Hz which can flow through the
GTA in accordance with a certain test method without
substantially altering its sparkover voltage. The
usual test consists of specified loads applied for 1
sec at interval of 1 min alternately. ln the test of the
maximum AC discharge current, the GTA is applied
9 cycles of 50Hz AC(180 ms) continuously.
The life is defined as the minimum number of surges
of a certain current waveform the GTA can survive
without deterioration of its operating specifications.
This is defined as the resistance value across the
terminal of GTA at 100VDC for devices over 230VDC
(140VDC for GTA type) breakdown voltage and 50VDC
for devices less than 230VDC(140VDC for GTA type) ratings.
The voltage is the minimum slowly rising DC voltage that
will cause sparkover when applied across the terminal
of the GTA.The GTA shall be placed in darkness for
at least 15 min and tested in this condition using a
ramp voltage waveform with 100V/s to 500V/s.
The GTA shall be tested with a positive and a
negative waveform. The sparkover current for DC
sparkover voltage test shall be within 10 amps.
The GTA to be exposed to the test shall be kept in
total darkness before (for at least 15 min) and during
the test. Then, with a ramp voltage with 5kV / s
applied to the GTA, the breakdown voltage level is
recorded. ln case of testing with opposite polarity,
using the same GTA, a minimum of 15 min shall
elapse.
This test is to determine the ability of the GTA t o
conduct a maximum single impulse Discharge
current. The current impulse waveform is 8 / 20
s.
The maximum single impulse discharge current
is the crest
current of the impulse.
This values is defined as the maximum DC voltage
across the terminals of the GTA which is
expected
to clear and restore its high impedance state within
150 ms or less after the passage of a surge.
The capacitance of the GTA is defined as
capacitance across terminals of the GTA at 1 kHz.
20 C 65 C
lmpulse breakdown voltage is the voltage at which
the GTA fires when the voltage increases at rates
of more than 100V/ s. This value may not vary even
after the GTA has been stored in the dark for long
period. The value of the impulse breakdown voltage
increases with increasing steepness of the surge
voltage as the figure below.
Non self
sustaining
Townsent
Glow
b
c
d
a
e
f
g
Arc
1A
10
16
10
4
10
5A
abnomalous
glow
100
90
50
10
Tf
Tt
Time ( s)
V
V
T
D
D
D
R
R
Ro
Ro
C
C
loc
li
1
2
1. DC constant-voltage regulated power supply
2. lmpulse generator
: DC current adjustment resistor
: Line mimic resistor 136 Ohms
: Line mimic capacitor 0.083 F
: lnsulation diode
Current
A
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