The surge protection system required by the automatic control system is usually composed of two or three stages, and the reliable protection can be realized by using the characteristics of various surge suppression devices. Gas discharge tube is generally placed on the input line, as a surge protection device, withstand large surge current. The two stage protection device uses a varistor, which responds faster in the time scale of the range of S. For highly sensitive electronic circuits, the three stage protection device TVS can be used to respond to the surge voltage in the PS time range. As shown in figure 5. When the lightning surge arrives, TVS will first start, the transient overvoltage control at a certain level; if the surge current is large, varistor starter, and discharge the inrush current; the voltage will be increased, until the electric push put before the gas discharge tube, high current discharge ground.

Arc extinguishing characteristic AC working state:
After the surge, the general discharge tube will extinguish the arc, because the AC voltage zero will fall below the arc voltage of the discharge tube, but in the low impedance of the electric, this arc extinguishing characteristics can not be fully realized. This is caused by the low internal resistance of the circuit and the low resistance ohm of the discharge tube after ignition. The actual current passed through the discharge tube may exceed the maximum current, and the current can be as high as several thousand amperes. (Note: after the surge, the discharge current of the discharge tube should be limited, otherwise the discharge tube may start the peripheral components

DC working state:
Generally speaking, DC power supply is used in communication system protection. Under sustained DC voltage, the discharge tube should be able to extinguish after the surge. Because the communication circuit is generally high resistance, so the discharge tube for this can easily meet this requirement. When the system has high DC voltage or low impedance, it is necessary to confirm the arc extinction performance of the discharge tube according to individual cases.
Discharge tube with function of failure protection card:
When the power line and the communication line overlap, the current usually lasts for a long time through the discharge tube after the breakdown, so that the discharge tube temperature rises. In this case, in order to avoid the peripheral hardware overheating, the protection card device can be used to monitor its heating situation. The configuration in short circuit on the spring separator (solder or plastic), at the beginning of the short-circuit spring and the electrode to maintain a certain distance, the tin solder melt when the temperature exceeds the melting points of the materials used, the reed reed bias down and contact discharge electrode, the discharge circuit.

Discharge tube test condition:
The impact of the nominal discharge current 8/20 s 8/20 s rated discharge current waveform.
– ITU-T and DIN VDE requirements: 10 discharges.
Additional requirements for ITU-T: no DUT temperature accumulation during continuous discharge.

The single largest single impact load discharge current 8/20 s waveform
The impact of discharge current 10/350 s
A 10/350 s rated discharge current discharge
Rated effective value of nominal power frequency current AC current 50 Hz/1s.
- ITU-T requirements: 10 discharge (without DUT temperature accumulation).
- DIN VDE requirements: 5 discharge.

AC discharge current
Rated effective value of AC current at 9 /50 Hz.
– RUS PE-80 requirements: 11 cycles /60 Hz

Maximum continuous flow
For the EF series, we set this characteristic for the most current from the current source through the discharge tube during the surge attenuation to the next zero crossing voltage
Large allowable current. This discharge can be repeated 10 times within 30 seconds.
Service life
Discharge rated discharge current 10/1000 under s 300. Technical specifications preparation.

Normally, the test voltage 100V DC is used to test the discharge tube. The test voltage of the discharge tubes of the 90 and 150 V DC models is 50V DC.
Capacitance C

The discharge capacitance (not plus spring):
Epp Kos gas discharge tube: 0.5 pF... 3 pF
(depending on the type)
ITU-T requirements: < 20 pF
DIN VDE requirements: < 5 pF

Transistor test form
The specific breakdown voltage, insulation resistance and capacitance between the electrode a/b of one end and the intermediate electrode C are detected by referring to relevant testing methods.
The pulse or AC withstand current, as specified in this catalogue, is the total current from both electrodes loaded to the intermediate electrode unless otherwise specified.