Saturday, July 19, 2014

Lightning Arrester Working Priciple; How Lightning Arrester works

Lightning arrester is nothing more than a spark air gap with one side connected to a line conductor and the other side connected to earth. When the line-to-ground voltage reached the spark-over level, the voltage surge would be discharged to earth.

The modern metal oxide arrester provides both excellent protective characteristics and temporary overvoltage capability. The metal oxide disks maintain a stable characteristic and sufficient non-linearity and do not require series gaps

Current level in a Lightning Stroke,
Current levels in lighting stokes is as below:-
1 percent'of strokes exceed 200 000 A
10 percent of Strokes Exceed 80 000 A
50 percent of Strokes Exceed 28 000 A
90 percent of Strokes Exceed 8 000 A
99 percent of Strokes Exceed 3 000 A

The current in the majority of earth flashes is from the negatively charged cells and the flash current is, thus, a negative Row from cloud to earth there will be lighting strokes from positive charged cell but they are very few ones.

Sometime lighting stokes took place in span of 50 ms to 100 ms.

Voltage rise due to lightning
There will be few 100 million of volts in every lighting stroke.  These strokes can  generate heat of upto 54000 degree fahrenheit.

 The lightning stroke begins by the detailed descent in the cloud of a leader stroke step dancing some tens of meters. When the last measure brings the point of the leader adequately close to ground, the ground to join the point of down leader is left by an upward streamer.
This upward streamer's initiation is determined by an essential field being surpass at the world emission point and is a function of the charge - any improvement of the field and coming leader due to the earth's geometry. The amount of the streamer that is upward will be greater for charges that are greater and thus high flashes that are current will begin from high constructions that the field improvement is not low.
Electrical Effects
It may additionally create a high potential gradient dangerous to creatures and men. In exactly the same general way the inductance must be considered due to the steep leading edge of the lightning pulsation.
The resulting voltage drop is so, the mixture of the inductive and resistive voltage elements.
Side Flashing
The stage of strike the protective system may be increased to adjoining metal' into a high potential with regard. There exists thus, a danger of flashover in the protective system any other metal on or in the construction. If such flashover occurs, part is released through internal setups, including wiring and conduits, and thus this flashover represents a danger to the occupants and fabric of the construction.
Thermal effects
As far as lightning protection is affected by it, the effects are confined to the temperature rise of the conductor whereby the current passes. Although the current is high, its duration is brief, and the thermal effect on the protective system is usually negligible. (This discounts the fusing or welding effects on damaged conductors ") In general, the cross-sectional area of a lightning conductor is chosen primarily to meet the demands of mechanical strength, meaning it's big enough to keep the rise in temperature to 1degC in case of copper conductor. The substitution of steel results in a rise of less than 10 degree C.
Mechanical Effects
Where a high current is discharged along parallel conductors at close proximity, or along one conductor with sudden bends, considerable mechanical forces are generated. Secure mechanical fittings arc, thus, crucial. A different mechanical effect used by a lightning Bash is primarily due to the abrupt rise in air temperature along which the charge is propagated in the channel to 30000 K and the ensuing volatile expansion of the adjoining atmosphere. That is because, when that of an arc route replaces the conductivity of the metal, the energy increases about one hundredfold.

Likewise, with a secondary flash inside the building, the shock wave can lead to damage to the building material.

Voltage spikes can be created by lightning in several of these manners. It can hit at the overhead power line or a primary power line that's blocks from your residence. Lightning can hit at division circuitry wiring in your house's walls.
Lightning can hit an item near your residence for example the earth or a tree itself and cause a spike.
Normal on and off changing actions of big electric motors or pieces of gear can also cause voltage spikes.
They are able to happen with little if any warning.

What is Lightning arrester??
A Device Used on Power Systems above 1000V to Protect other Equipment from Lightning and Switching Surges.
•It Does not Absorb the Lightning
•It Does not Stop the Lightning
•It Does Divert the Lightning to Ground
•It Does Clamp (limit) the Voltage produced by the Lightning
•It Only protects equipment electrically in parallel with it.

Below figure shows how a lightning arrester works.

Lightning Arrestot working principle; LA Principle

Yellow line shows lightning path when arrester is installed.

Arrester Internal Structure:-

MOV In Arrester; Lightning internal

Above diagram shows internal of Lightning arrester which consists of MOV'S i.e. Metal oxide varistors .
The MOV Disk is a Semiconductor that is sensitive to Voltage. At normal Voltages the MOV disk is an insulator and will not conduct current. But at higher voltages caused by lightning it becomes a conductor.

Methodology to Suppress Voltage Spike and Lighting:
When there is a voltage spike created, it needs to equalize itself and it needs to do it as fast as possible. These matters appear to have little patience. The spikes will do whatever is necessary neutralize or to equalize themselves, even though it means short circuiting all your electronic equipment.

The way of supplying maximum protection for gear is fairly straightforward.
That is not, generally, a task that is difficult.

Step one is not complex.

Create a fantastic grounding system for the home electrical system. A large proportion of houses don't have a great grounding system. Many houses have /or a metallic subterranean water pipe which are part and one grounding pole. Typically, that is not adequate. The reason is not fairly difficult to describe. I doubt the drain could manage all the water. Your grounding system would respond to some huge voltage spike in exactly the same manner. As the water leaps out from the sink, the electricity looks for areas to go and jumps in the grounding system. They're a simple target.

Voltage spikes are interested in being directed to the grounding system, and they would like to enter the earth when they do. It's possible for you to accomplish this by driving grounding rods that are numerous around your house into virgin land. These poles should be UL approved and joined by a constant heavy solid copper wire that is welded to each grounding pole. This solid copper cable terminates at the last grounding pole and starts on the grounding pub interior of your electric panel. Avoid using clamps. The connection can corrode or become creating incredible resistance. This will become a roadblock to the electricity attempting to enter the earth around your house.

The should be found in land which easily takes electricity. Clay lands that are damp have become desirable. Lands with gravel, or rugged, sandy typically have high resistance variables. Electricity has a rough time dissipating into the. Resistance readings should take the range.

The second part of home spike protection would be to install a lightning arrester interior of your electrical service panel. These apparatus can be tremendously successful in intercepting substantial voltage spikes which go in the electric power lines. The voltage spikes are captured by these devices and 'bleed' them away to the grounding cable which we only spoke of. If for some reason you don't have enough ground poles, the arrester cannot, or a big enough grounding wire do its occupation. It must have the ability to send the spike immediately to the earth beyond your home. One is made by nearly every maker . Have a skilled electrician install this capability for you, if you don't have it.

The ultimate part of the protection strategy would be to install 'point of use' spike suppression devices. Frequently you'll see these named 'transient voltage surge suppressors'. They may be capable of just quitting the left over voltage spike which got past the lightning arrester and the grounding system. Themselves must be applied in conjunction with the lightning arresters and the grounding system.

The' point' spike suppression devices can be found in various degrees of quality. Some are not much worse than others. What sets the apart are several matters. Most of the time, you look to find out how speedy the's time is. That is frequently called clamping speed. Ensure the apparatus has a 500 volt maximum suppression degree was rated by UL. Check to see if it's an indicator, either sound or visual, which allows you to understand if it's not working. The units that are better offer both, in the event you install the apparatus out of sight. Check to see whether it offers various modes regarding protection. There's a difference! Check to see if it tracks the standard sine waves of routine household current. Irregularities can be caused by spikes . Ultimately, assess the joule rating. Try to find a device that has a joule rating or higher. Electric supply houses frequently are the ideal spot to look for these apparatus that are high quality.

Some devices also can shield your telephone gear at once. That is essential for those people that have computer modems. Huge voltage spikes can run into phone lines at the same time. These spikes can enter your computer! Do not forget to shield this line. Additionally, be certain the phone ground wire is tied to the updated electric grounding system.