What is the difference between Dyn11 and Dyn5?

A Dyn11 transformer, if abc terminals are connected to rst phases, will shift the output from "12 o clock" to "11 o clock" ie 30 degrees back. A Dyn5 if connected the same way will advance the output to "5 o clock" ie 150 degrees forward. The difference in output between the Dyn11 and Dny5 and is therefore 180 degrees.

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What's the difference between ONAN and ONAF?

Cooling Methods In Oil Immersed Transformers

ONAN - It is short for Oil Natural Air Natural and in this method, the heat that gets generated in the core and winding of the device is transferred to the oil. Then, the heated oil flows upwards and reaches the radiator. The place that is now vacant gets filled with the cooled oil from the radiator. The heat generated in the oil will then dissipate into the atmosphere because of the natural air flow around the transformer. 

ONAF – With the method of Oil Natural Air Forced, the heat dissipation can be improvised by applying forced air on the dissipating surface. This technique is used because forced air provides faster heat dissipation than the natural one. 

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What is the compact substation?A Compact Secondary Substation (CSS) is a type tested and arc tested assembly comprising an enclosure containing medium voltage (MV) switchgear, distribution transformers, low voltage (LV) switchboards, connections and auxiliary equipment to supply LV energy from MV systems.

What are the four types of substations?

Substation Types: Although, there are generally four types of substations there are substations that are a combination of two or more types.

• Step-up Transmission Substation.

• Step-down Transmission Substation.

• Distribution Substation.

• Underground Distribution Substation.

• Substation Functions.

• Substation Equipment.

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Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer

A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil.

Transformers are used to change AC voltage levels, such transformers being termed step-up or step-down type to increase or decrease voltage level, respectively. Transformers can also be used to provide galvanic isolation between circuits as well as to couple stages of signal-processing circuits. Since the invention of the first constant-potential transformer in 1885, transformers have become essential for the transmission, distribution, and utilization of alternating current electric power.A wide range of transformer designs is encountered in electronic and electric power applications. Transformers range in size from RF transformers less than a cubic centimeter in volume, to units weighing hundreds of tons used to interconnect the power grid.

Ideal transformer

An ideal transformer is linear, lossless and perfectly coupled. Perfect coupling implies infinitely high core magnetic permeability and winding inductance and zero net magnetomotive force (i.e. i_pn_p − i_sn_s = 0).^[3][c]

A varying current in the transformer's primary winding creates a varying magnetic flux in the transformer core, which is also encircled by the secondary winding. This varying flux at the secondary winding induces a varying electromotive force or voltage in the secondary winding. This electromagnetic induction phenomenon is the basis of transformer action and, in accordance with Lenz's law, the secondary current so produced creates a flux equal and opposite to that produced by the primary winding.

The windings are wound around a core of infinitely high magnetic permeability so that all of the magnetic flux passes through both the primary and secondary windings. With a voltage source connected to the primary winding and a load connected to the secondary winding, the transformer currents flow in the indicated directions and the core magnetomotive force cancels to zero.

According to Faraday's law, since the same magnetic flux passes through both the primary and secondary windings in an ideal transformer, a voltage is induced in each winding proportional to its number of turns. The transformer winding voltage ratio is equal to the winding turns ratio.

An ideal transformer is a reasonable approximation for a typical commercial transformer, with voltage ratio and winding turns ratio both being inversely proportional to the corresponding current ratio.

The load impedance referred to the primary circuit is equal to the turns ratio squared times the secondary circuit load impedance.

Real transformer

Deviations from ideal transformer

The ideal transformer model neglects many basic linear aspects of real transformers, including unavoidable losses and inefficiencies.

(a) Core losses, collectively called magnetizing current losses, consisting of.

• Hysteresis losses due to nonlinear magnetic effects in the transformer core, and

• Eddy current losses due to joule heating in the core that are proportional to the square of the transformer's applied voltage.

(b) Unlike the ideal model, the windings in a real transformer have non-zero resistances and inductances associated with:

• Joule losses due to resistance in the primary and secondary windings

• Leakage flux that escapes from the core and passes through one winding only resulting in primary and secondary reactive impedance.

(c) similar to an inductor, parasitic capacitance and self-resonance phenomenon due to the electric field distribution. Three kinds of parasitic capacitance are usually considered and the closed-loop equations are provided

• Capacitance between adjacent turns in any one layer;

• Capacitance between adjacent layers;

• Capacitance between the core and the layer(s) adjacent to the core;

Inclusion of capacitance into the transformer model is complicated, and is rarely attempted; the ‘real’ transformer model's equivalent circuit shown below does not include parasitic capacitance. However, the capacitance effect can be measured by comparing open-circuit inductance, i.e. the inductance of a primary winding when the secondary circuit is open, to a short-circuit inductance when the secondary winding is shorted.

Leakage flux

Main article: Leakage inductance

The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings.Such flux is termed leakage flux, and results in leakage inductance in series with the mutually coupled transformer windings. Leakage flux results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a power loss, but results in inferior voltage regulation, causing the secondary voltage not to be directly proportional to the primary voltage, particularly under heavy load. Transformers are therefore normally designed to have very low leakage inductance.

In some applications increased leakage is desired, and long magnetic paths, air gaps, or magnetic bypass shunts may deliberately be introduced in a transformer design to limit the short-circuit current it will supply. Leaky transformers may be used to supply loads that exhibit negative resistance, such as electric arcs, mercury- and sodium- vapor lamps and neon signs or for safely handling loads that become periodically short-circuited such as electric arc welders.

Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a DC component flowing in the windings. A saturable reactor exploits saturation of the core to control alternating current.

Knowledge of leakage inductance is also useful when transformers are operated in parallel. It can be shown that if the percent impedance  and associated winding leakage reactance-to-resistance (X/R) ratio of two transformers were the same, the transformers would share the load power in proportion to their respective ratings. However, the impedance tolerances of commercial transformers are significant. Also, the impedance and X/R ratio of different capacity transformers tends to vary.

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A transformer designed to increase the voltage from primary to secondary is called a step-up transformer. A transformer designed to reduce the voltage from primary to secondary is called a step-down transformer.

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Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer Three phases transformer

Liquid-cooled (oil-filled) transformers use oil as the cooling and insulating medium. They are commonly used in high-voltage power transmission and distribution systems, as well as in industrial and commercial applications, where a higher power rating and increased efficiency is required.

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Simply put, Chinese New Year and Lunar New Year are not the same, although they are very much connected. In a casual conversation, both terms can be used interchangeably as synonyms. However, in a more strict cultural environment, it is necessary to understand the differences between the two.

Why is Chinese New Year not on the same day every year? 

Chinese New Year is not on the same day every year because it is worked out according to the first day of the Chinese Lunar calendar. This means the year is determined by the movements of the sun and moon.

Why is red a significant colour in Chinese culture? 

Use evidence from the text to support your answer. The colour red is very lucky to the Chinese as it symbolises fortune, good luck and joy. It is also the colour that, according to legend, scared away the Nian beast, ensuring the safety of the village. 

Why is money given in even amounts? 

Money is given in even amounts because odd numbers are believed to be bad luck in Chinese culture. 

 Why do you think lions and dragons are used for the dance in the parade rather than animals such as rabbits, cats and dogs? Lions and dragons are the most commonly used animals as part of the Chinese New Year parade dance as these costumes are bigger allowing more people to fit underneath them. Lions and dragons are big, fierce creatures, they can scare away evil spirits and bad luck. 

 In your own words, explain the legend of how Chinese New Year began. Pupils’ own responses, such as ‘According to Chinese legend, a village was attacked by a monster called the Nian, which ate their food, livestock and people. The villagers left food out for it but noticed that it was scared of a girl wearing red. They then used red lanters, scrolls and firecrackers to scare away the Nian and it never returned.’

Power transformers are used in transmission network of higher voltages for step-up and step down application (400 kV, 200 kV, 110 kV, 66 kV, 33kV) and are generally rated above 200MVA. Distribution transformers are used for lower voltage distribution networks as a means to end user connectivity.

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High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer

Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer

High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer

Three phases transformer Liquid transformer Dry type transformer Surge arrester Lightning arrester Distribution transformer Power transformer Paid mounted transformer

High voltage switchgear Low voltage switchgear Skid mounted transformer Mother coil Silicone steel plate Single phase transformer

Three phases transformer