science

Lightning arrester

Lightning arrester is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lightning arrester rather than just read about it. In short: A lightning arrester (alternative spelling lightning arrestor) (also called lightning isolator) is a device used on electric power transmission and telecommunication 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.

Key takeaways

Lightning arrester belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lightning arrester to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lightning arrester from memory before moving on to harder problems.

Reference excerpt

A lightning arrester (alternative spelling lightning arrestor) (also called lightning isolator) is a device used on electric power transmission and telecommunication 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 arrester, in most cases to earth. In telegraphy and telephony, a lightning arrester is placed where wires enter a structure, preventing damage to electronic instruments within and ensuring the safety of individuals near them. Smaller versions of lightning arresters, called surge arresters, are devices that are connected between each conductor in power and communications systems and the earth. These prevent the flow of the normal power or signal currents to ground, but provide a path over which high-voltage lightning current flows, bypassing the connected equipment. Their purpose is to limit the rise in voltage when a communications or power line is struck by lightning or is near to a lightning strike. If protection fails or is absent, lightning that strikes the electrical system introduces thousands of kilovolts that may damage the transmission lines, and can also cause severe damage to transformers and other electrical or electronic devices. Lightning-produced extreme voltage spikes in incoming power lines can damage electrical home appliances or even cause death. Lightning arresters are used to protect electric fences. They consist of a spark gap and sometimes a series inductor. Such type of equipment is also used for protecting transmitters feeding a mast radiator. For such devices the series inductance has usually just one winding.

Lightning arresters can form part of large electrical transformers and can fragment during transformer ruptures. High-voltage transformer fire barriers are required to defeat ballistics from small arms as well as projectiles from transformer bushings and lightning arresters, per NFPA 850.

Components A potential target for a lightning strike, such as an outdoor television antenna, is attached to the terminal labeled A in the photograph. Terminal E is attached to a long rod buried in the ground. Ordinarily no current will flow between the antenna and the ground because there is extremely high resistance between B and C, and also between C and D. The voltage of a lightning strike, however, is many times higher than that needed to move electrons through the two air gaps. The result is that electrons go through the lightning arresters rather than traveling on to the television set and destroying it. A lightning arrester may be a spark gap or may have a block of a semiconducting material such as silicon carbide or zinc oxide. "Thyrite" was the trade name used by General Electric for the silicon carbide composite used in their arrester and varistor products. Some spark gaps are open to the air, but most modern varieties are filled with a precision gas mixture, and have a small amount of radioactive material to encourage the gas to ionize when the voltage across the gap reaches a specified level. Other designs of lightning arresters use a glow-discharge tube (essentially like a neon glow lamp) connected between the protected conductor and ground, or voltage-activated solid-state switches called varistors or MOVs. Lightning arresters used in power substations are large devices, consisting of a porcelain tube several feet long and several inches in diameter, typically filled with discs of zinc oxide. A safety port on the side of the device vents the occasional internal explosion without shattering the porcelain cylinder. Lightning arresters are rated by the peak current they can withstand, the amount of energy they can absorb, and the breakover voltage that they require to begin conduction. They are applied as part of a lightning protection system, in combination with air terminals and bonding.

See also Lightning rod Surge arrester Thyristor switched capacitor Faraday cage

References

External links "Electrical Devices and How They Work, Part 14: Lightning Arresters" (article about lightning arresters and how they were used in early AC and DC power distribution systems), Popular Science monthly, February 1919, 5 unnumbered pages, scanned by Google Books OSHA Electric Power eTool: Illustrated Glossary: Lightning Arresters An extensive dictionary of terms used with arresters at ArresterWorks.com History of arresters at ArresterWorks.com Graphic Overview of how an arrester works NEMA Surge Protection Institute

Illustrations

Worked examples

Example 1 — a first encounter with Lightning arrester

Start with the simplest possible case. Write down what Lightning arrester claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lightning arrester before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lightning arrester ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lightning arrester

In research: Lightning arrester appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lightning arrester in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lightning arrester is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electrical safety, Lightning, so understanding it makes those chapters shorter.
In everyday life: Look for Lightning arrester outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lightning arrester in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lightning arrester means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lightning arrester out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lightning arrester in simple terms?

Why does Lightning arrester matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lightning arrester?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lightning arrester.