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What is the difference between lightning arrester and surge arrester

Time:2018/05/29     From:composite insulator Fittings c     Views:0
What is the difference between lightning arrester fittings and surge arrester fittings?

Lightning Arrester fittings

The lightning conductor protects structures against direct lightning strikes.

The lightning conductor material is arranged outside on the highest point of a structure.

The lightning conductor has the function of capturing lightning strikes are succeptibles directly hitting the structure it protects.

The Outdoor Installation Protection against Lightning consists of a sensor called lightning rod, at least oneconductorand a grounded outlet dedicated to each driver.

The ground connections must be connected together and all the metal masses in the vicinity.

Outdoor installation Protection against Lightning captures leads and flows into the ground the electric current from lightning.

Surge Arrester fittings

The arrester protects against indirect effects of lightning strikes.

The SPD is the material placed inside of a structure on networks that transport electricity (power, communications, data ...).

The arrester has the function to avoid surges in the network it protects.

The Inside Installation of Protection against Lightning consists of one or more arresters systems.

The arresters act as switches. The arresters close their circuit when surge appears on the network and they divert the current to earth ground.

Indoor installation Protection against Lightning duct and flows surges and currents in the electrical grounding.
Lightning arrestor gives the protection against lightning only, as you can see these are installed on the top of the huge buildings. That lightning arrestor is connected to a conductor which runs along the walls and goes into the earth.
Surge arrestor gives the protection against surge currents or voltages in a circuit. Surges can be produced because of short circuit, lightning, sparking etc.
Hence, a surge arrestor can also be used as a lightning arrestor but a lightning arrestor can't be used as a surge arrestor in case of short circuits.
That lightning arrestor is connected to a conductor which runs along the walls and goes into the earth. Surge arrestor gives the protection against surge currents or voltages in a circuit. Surges can be produced because of short circuit, lightning, sparking etc.

A surge arrester is a device to protect electrical equipment from over-voltage transients caused by external (lightning) or internal (switching) events. ... The same kind of induction happens in overhead and above ground conductors which experience the passing energy of an atmospheric EMP caused by the lightning flash.

A lightning arrester is a device used on electrical power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth.
In the present day, both these terms are used interchangeably.

In the olden days, Over voltages produced due to lightning acted as a severe threat to the power system. So the device which was used to suppress this lightning over-voltage was termed as lightning arrester.

But in the recent times due to the development in power system, EHV and UHV systems came into existence. Thus the effect of Switching over-voltages ( due to the opening and closing of circuit breakers) is much severe when compared to the Lightning Over-voltage.(as the transmission line voltages have multiplied by many folds)

Thus they have re-framed the word as Surge arrestor as it has to arrest both lightning and as well as Switching over voltage. Basically, both the lightning arrester and surge arrester are one and the same in construction, operation and in everything.
Surge Arresters are widely also known Lightning arrester. However strictly speaking the two are in fact different.

Surge arresters are devices installed on Over head lines, substations etc to avoid a surge of an additional current/ voltage/charge due to various faults occurring and since one of the major reasons of a surge is due to lightning, these surge arresters are also coined as Lightning arrester.

However Lightning arresters are separate instruments specifically designed for protection of structures solely from lightning this equipment neutralizes the charge by nullifying the charge it receives from the lightning and grounds it.

Lightning arresters don't intervene with the excess current / voltage surge due to electrical faults - it is solely for lightning protection unlike surge arrestors which is a protection against electrical faults and Lightning which is a natural charge dispenser.

In short, lightning arrester is not supposed to conduct at power frequency. Whereas surge arrester is supposed to conduct at power frequency.
Lightning arrestor is installed outside and the effect of lightning is grounded, where as surge arrestor installed inside panels comprising of resistors which consumes the energy and nullify the effect of surge.

Transmission Line Lightning Protection:

The transmission line towers would normally be higher than a substation structure, unless you have a multi-storey structure at your substation.
Earth Mats are essential in all substation areas, along with driven earth electrodes (unless in a dry sandy desert site).
It is likewise normal to run catenaries(aerial earth conductors) for at least1kM out from all substation structures. Those earth wires to be properly isolated electrically to each supporting transmission tower, and bonded back to the substation earth system.
It is important to have the catenary earth conductors above the power conductor lines, at a sufficient distance and position that a lightning strike will not hit the power conductors.
In some cases it is thus an advantage to have two catenary earth conductors, one each side of the transmission tower as they protect the power lines below in a better manner.
In lightning-prone areas it is often necessary to have catenary earthing along the full distance of the transmission line.
Without specifics, (and you could not presently give tower pictures in a Post because of a CR4 Server graphics upload problem), specifics would include:
Structure Lightning Protection:

At the Substation, it is normal to have vertical electrodes bonded to the structure, and projecting up from the highest points of the structure, with the location and number of those electrodes to be sufficient that if a lightning strike arrived, it would always be a vertical earthed electrode which would be struck, rather than any electrical equipment.
In some older outdoor substation structures, air-break isolator switches are often at a very high point in the structure, and in those cases small structure extension towers are installed, with electrodes at the tapered peak of those extension towers.
The extension towers are normally600mm square approximately until the extension tower changes shape at the tapered peak, and in some cases project upwards from the general structure2 to6 metres, with the electrode some2 to3 metres projecting upwards from the top of the extension tower.
The substation normally has a Lightning Counter – which registers a strike on the structure or connected to earth conductors, and the gathering of that information (Lightning Days, number per Day/Month/Year, Amperage of each strike).
ZnO Gap-less Lightning Arrester or Surge Arrester

An electrical surge can be occurred in an ELECTRICAL POWER TRANSMISSION SYSTEM due to various reasons. Surge in an electrical system originated mainly due to lightning impulses and switching impulses. Electrical surge produces a large transient over voltage in the electrical network and system. The shape of the transient over voltage has a steeply rising front with slowly decaying tail as shown in the figure below. This steep voltage wave travels through the electrical network and causes over voltage stresses on all the ELECTRICAL INSULATORS and equipment come under its traveling path.

That is why all electrical equipment and insulators of power system must be protected against electrical surges. The method of protecting system from surge is normally referred as surge protection.

The main equipment commonly used for this purpose is lightning arrester or surge arrester. There are two types of surges one comes externally from atmosphere such as atmospheric lightning. Second type is originated from electrical system itself, such as switching surges.

Construction of Zinc Oxide Lightning Arrester

This type of arrester comprises of numbers of solid zinc oxide disc. This discs are arranged one by one to form a cylindrical stack. The number of zinc oxide discs used per lightning arrester depends upon the voltage rating of the system. This stack is kept inside a cylindrical housing of polymer or porcelain. Then the stack is placed inside the housing and highly pressed by heavy spring load attached to end cap at top. The equipment connection terminal for line is projected from top cap and connection terminal for earth is projected from the bottom cap.

Working Principle of Zinc Oxide Lightning Arrester

The normal operation is defined as condition when no surge is presented and the surge arrester is subjected to normal system voltage only. The zinc oxide has highly non-uniform current voltage (I-V) characteristics. This typical I-V characteristic makes zinc oxide very suitable for designing gap less zinc oxide lightning arrester for surge protection. The non linear resistance of the block is an inherent bulk property and consists of mainly zinc oxide (90 to 95%) with relatively small amounts of several additives of other metal oxide (5 to 10%) like alumina, antimony tri-oxide, bismuth oxide, cobalt oxide, zirconium etc. On a macroscopic scale the additives are almost homogeneously distributed throughout the arrester blocks. But the micro structures of the metal oxide block represents a network of series and parallel arrangements of highly doped zinc oxide (ZnO) grains separated by inter granular junctions. The non linear behavior is the super imposition of non linear characteristics of individual junctions. The current carrying capacity of the surge arrester block is proportional to the total cross-section of the block.
The main differences between a lightning arrester and a surge arrester are time and position. In the past, there were only lightning arresters, since lightning was the only place where big power surges would come from. Now, a lighting arrester typically prevents surges from outside the electrical grid, and a surge arrester prevents ones from inside.
"Both are doing the same job,but both are not same".

A surge arrester is device that intercepts electrical surges and sends the spike to ground before it can hurt a connected device. These arresters are also known as surge protectors or lightning arresters, but there are some very small differences between these devices. In most cases, when a surge arrester intercepts a power surge, it fuses itself to prevent transmission. This will stop the surge, but it also destroys the surge arrester. If the arrester is improperly installed, this fusion can cause more problems than the initial surge.
In power system, surges are transients that occur all of a sudden. These transients can reach amplitudes of very high voltages and will last only for a short period of time. Within that short period, it can damage or degrade electrical or electronic equipment. Most of the electrical devices are designed in such a way that they can withstand very slight variations in their nominal operating voltage. But they will get damaged when they are subjected to the surge voltages that are oscillating and decaying over time in nature.