How does surge arrester operate?

Answer 1

A surge arrestor helps prevent a voltage spike on your home electrical supply from damaging your electronics by shunting that voltage to ground. Here is an article that describes what the do and how to use them. http://handydandytips.googlepages.com/howtoprotectyourhomeelectronicsfromlight

Answer 2

Gas-filled surge arresters operate on the gas-physical principle of the highly effective arc discharge. Electrically, surge arresters act as voltage dependent switches. As soon as the voltage applied to the arrester exceeds the spark-over voltage, an arc is formed in the hermetically sealed discharge region within nanoseconds. The high surge current handling capability and the arc voltage, which is almost independent of the current, short-circuit the overvoltage. When the discharge has doed down, the arrester exinguishes and the internal resistance immediately returns to values of several 100 Mohms.

The surge arrester thus meets almost perfectly requirements made on a protective element. It reliably limit the overvoltage to permissible values and - under normal operating conditions - the high insulation resistance and the very low capacitance contribute to the fact that a surge arrester has virtually no impact on the system to be protected up to the GHz area.

The electrical properties of an open gas-discharge path depend greatly on environmental parameters such as gas type, gas pressure, humidity and pollution. Stable conditions can only be ensured if the discharge path is shielded against these environmental influences. The design principle of surge arresters is based on this requirement. A proven technique of connector insulator and electrode ensures hermetic sealing of the discharge space. The type and pressure of the gas in the discharge space can thus be selected on the basis of optimun criteria. The rare gases argon and neon are predominantly used in gas filled arresters since they ensure optimum electrical characteristics througout the entire useful life of the arrester. An activating compound is applied to the effective electron emission surfaces of the electrodes, themselves separated typically by less than 1 mm, to reduce the work function of the electrons and to guarantee the stability of the ignition voltage even after repeated current loads. Gas filled surge arrestersfeature an optimum relationship between size, impulse discharge capability and a longer than average useful life.

To achieve excellent response characteristic at fast rise time, ignition aids have been attached to the cylindrical internmal surface of the insulator. It speeds up the gas discharge by distorting the electric field. Gas arrestors has therefore a fast response characteristic. The electrical characteristics of the arrester, such as DC-spark over voltage, pulsed and AC dischargecurrent handling capability as well as its service life, can be optimized to the specific requirements of various systems. This is achieved by varying the gas type and pressure as well as the spacing of the electrodes and the emission-promoting coating of the electrodes.

Normally the surge arresters are designed with two or three electrodes. Both types can include temperature dependent short circuit springs to protect the arrester against to high overload.

A simplified surge arrester can be compared with a symmetrical low-capacitance switch whose resistance may jump from several Gohms during normal operation to values <1 ohm after ignition, caused by a surge voltage.

If a voltage of low rate of rise (typically 100V/s) is applied to the arrester, the spark-over voltage will be determined mainly by the electrode spacing, the gas type and pressure, and by the degree of pre-ionization of the enclosed noble gas. the ignition value is defined as the DC-spark over voltage. This is called the static response behavior.

At fast rate of rise, the spark-over voltage of the arrester exceeds the static response level. This effect is caused by the finite time necessary for the gas to ionize. All these dynamic spark over voltages are subject to considerable statistical variation. However, the average value of the spark-over voltage distribution can be significantly reduced by attaching the ignition aid to the inside surface of the arrester.

This is called the dynamic response behavior.

A gas filled surge arrester can operate both at AC and DC voltages but it is important that the DC source may not be low-ohmic because if it is, it can under certain circumstances overheat the arrester and as a result of this, it does not return to the off-state again since the gas will still be in the ionized mode due to the heat created by the current flow

Gas filled surge arresters are classical components for protecting telecommunication installations, AC-power transmission systems, customer premises equipment such as xDSL-modems, WLAN routers, TVsets and cable modems etc.

Answer 3

surge arrestor is a device which is used to normalize the transient deveoped in the system due to faults occurring in the overhead lines,these faults maily occur due to thunder and flashing of light that occured in clouds, they are used as a protecting medium for the devices attached to the system.

Answer 4

Inorder to protect the electrical system from damage.It just limits the magnitude of transient overvoltage.