engineering

Switchyard reactor

Switchyard reactor is a engineering 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 Switchyard reactor rather than just read about it. In short: In an electric power transmission grid system, switchyard reactors are large inductors installed at substations to help stabilize the power system. For transmission lines, the space between the overhead line and the ground forms a capacitor parallel to transmission line, which causes an increase in voltage as the distance increases.

Key takeaways

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

Reference excerpt

In an electric power transmission grid system, switchyard reactors are large inductors installed at substations to help stabilize the power system. For transmission lines, the space between the overhead line and the ground forms a capacitor parallel to transmission line, which causes an increase in voltage as the distance increases. To offset the capacitive effect of the transmission line and to regulate the voltage and reactive power of the power system, reactors are connected either at line terminals or at the middle, thereby improving the voltage profile of transmission line. In large systems with many generators connected in parallel, it may be necessary to use a series reactor to prevent excessively large current flow during a short circuit; this protects transmission line conductors and switching apparatus from damage due to high currents and forces produced during a short circuit. A shunt reactor is connected in parallel with a transmission line or other load. A series reactor is connected between a load and source.

Bus reactors A bus reactor is an air core inductor, or oil filled inductor, connected between two buses or two sections of the same bus to limit the voltage transients on either bus. It is installed in a bus to maintain system voltage when the load of the bus changes. It adds inductance to the system to offset the capacitance of the line.

Line reactors A line reactor is placed in line at the point of use or just after a transformer to maintain a stable amperage to the user. When a line is disconnected from the system, the line reactor is also disconnected from the system. Line reactors are often used to compensate line capacitance, mitigate voltage transients due to switching, and to limit fault currents, especially in case of underground transmission lines. A bus reactor and a line reactor are interchangeable as long as they are rated for the same voltage which is dependent upon substation's physical layout, and bus configuration.

Shunt reactors Shunt reactors are used in power systems to counteract the effect of the line parasitic capacitance, thereby stabilizing the system voltage within acceptable limits. The utility of shunt reactors for voltage control on lightly-loaded transmission lines was examined in a 1926 paper presented at the AIEE by Edith Clarke. For short lines, we can basically ignore the impact of capacitive current from a voltage regulation point of view, but medium and long lines can have voltages at their receiving end much higher than the sending end, thus creating issues such as over-fluxing of power transformers and over stressing of line insulators. Under light-load conditions, the line produces more VARs, resulting in receiving end voltage being higher than sending end voltage. In order to consume the excess VARs when system is lightly loaded, an inductor is added to the system. A traditional shunt reactor has a fixed rating and is either connected to the power line all the time or switched in and out depending on the load. Recently variable shunt reactors (VSRs) have been developed and introduced on the market. The rating of a VSR can be changed in steps: the maximum regulation range depends on the capability of the on-load tap changer used in combination with the regulation winding used for the shunt reactor. The maximum regulation range has increased over the years, from 50%, up to 80% at some voltage levels. VSRs are considered technically advanced products and are mainly supplied by larger global manufacturers.

Controlled shunt reactors

A controlled shunt reactor (CSR) is a variable inductance, smoothly regulated by magnetic biasing of ferromagnetic elements of magnetic circuit. The magnetic system of a CSR single phase consists of two cores. Each core is equipped with control and power windings. In case of regulated DC voltage source connection to the control windings, biasing flow is increasing and directed to different sides in the adjacent cores. This resulted in saturation of CSR cores at relevant half-period of the current. Core saturation is resulted in initiation and increase of the current in the power winding due to non-linear characteristics of the magnetic core. Change in biasing current value leads to the power winding current change, due to which a stepless variation of voltage levels in CSR connection point as well as the value of reactive power consumed by the reactor is ensured.

Variable shunt reactor Variable shunt reactors are used in high voltage energy transmission systems to stabilize the voltage during load variations. The variability brings several benefits compared to a traditional fixed shunt reactors. The VSR can continuously compensate reactive power as the load varies and thereby stabilise the voltage. Other important benefits are:

reduced voltage jumps resulting from switching in and out a traditional fixed shunt reactor flexibility for future variation in load and generation patterns improved interaction with other transmission equipment and systems such as coarse tuning of SVC equipment limiting the footprint of a substation: if parallel, fixed shunt reactors can be replaced with one VSR a VSR can be used as a flexible spare unit and be moved to other locations in the power grid if needed mitigation of zero-miss phenomenon, while energisation of long power lines and cables

Series reactors Series reactors are used as current limiting reactors to increase the impedance of a system. They are also used for neutral earthing. Such reactors are also used to limit the starting currents of synchronous electric motors and to compensate reactive power in order to improve the transmission capacity of power lines.

References

External links

http://www05.abb.com/global/scot/scot252.nsf/veritydisplay/dadf3c1d27681cc48525775400608bb5/$file/1zse954001-21_vsr_pamphlet.pdf http://www.getra.it/default.php?mcat=azi&cod=casehistory&scod=casepower&id=320 http://www.swedishneutral.se/main.php?name=shunt_reactor

Worked examples

Example 1 — a first encounter with Switchyard reactor

Start with the simplest possible case. Write down what Switchyard reactor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, 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 Switchyard reactor 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 Switchyard reactor 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 Switchyard reactor

In research: Switchyard reactor appears in engineering 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 Switchyard reactor 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: Switchyard reactor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electric power transmission, Electrical engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Switchyard reactor 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Switchyard reactor in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Switchyard reactor 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 Switchyard reactor out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Switchyard reactor in simple terms?

Why does Switchyard reactor matter?

Because it connects several engineering 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 Switchyard reactor?

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 Switchyard reactor.