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three winding transformer
Three-winding power transformer capacity configuration and voltage ratio
2017-11-10
Three windings transformer windings of the capacity, respectively, as required. The rated capacity of the three windings that is the largest capacity of the winding, usually rated capacity of the primary winding. And as a 100%, then the capacity of the three windings are configured 100/100/50, 100/50/100, 100/100/100 three.The principle of no-load ... Three windings transformer windings of the capacity, respectively, as required. The rated capacity of the three windings that is the largest capacity of the winding, usually rated capacity of the primary winding. And as a 100%, then the capacity of the three windings are configured 100/100/50, 100/50/100, 100/100/100 three.The principle of no-load operation of three winding transformer is basically the same as that of double-wound transformer, but there are three voltage ratios, namely high voltage and medium voltage, high voltage and low voltage, medium voltage and low voltage. View Details
Features of Three-winding transformers
2017-11-08
In the three-winding transformer, the magnetic fluxes that are not synchronized with the three windings at the same time are all leakage magnetic fluxes. The magnetic flux that is linked to only one winding and not to the other two windings is called a self-leakage flux. The two windings are not linked to the third winding and the flux is called mu... In the three-winding transformer, the magnetic fluxes that are not synchronized with the three windings at the same time are all leakage magnetic fluxes. The magnetic flux that is linked to only one winding and not to the other two windings is called a self-leakage flux. The two windings are not linked to the third winding and the flux is called mutual leakage flux. The leakage voltage drop of each winding is affected by the other two windings. Therefore, the leakage reactance of the three-winding transformer is different from the leakage reactance of the two-winding transformer. In order to establish the voltage balance equation and the equivalent circuit, the concept of equivalent reactance is introduced. The equivalent reactances of the high, medium and low voltage windings include the self inductance inductance of each winding and the mutual inductance reactance between the windings, corresponding to the equivalent reactance of each winding There are their equivalent impedance, and are converted to the primary side of the value. View Details
The advantages of a three winding transformer are as given below
2017-06-13
The advantages of a three winding transformer are as given belowi) It can supply additional load providing insulation from secondary windings.ii) It can act as a source of voltage at substation to meet the internal load demand of substation which is at different voltage that either of primary or secondary voltage level.iii) The reactive power injec... The advantages of a three winding transformer are as given belowi) It can supply additional load providing insulation from secondary windings.ii) It can act as a source of voltage at substation to meet the internal load demand of substation which is at different voltage that either of primary or secondary voltage level.iii) The reactive power injection into the system is possible for voltage control by connecting synchronous condensers or static capacitors to the tertiary winding.iv) A delta connected tertiary winding offers less impedance to the flow of zero sequence currents. The allows larger earth fault current to flow through protective device facilitating its proper operation.v) It reduces voltage unbalance under unbalanced loading conditions and permits third harmonic current to flow which reduces third harmonic voltages.vi) Three transmission lines at different voltage levels can be interconnected by using three winding transformer.vii) The third winding of a three winding transformer, usually called tertiary winding can be used to serve purpose of measuring voltage of HV testing transformer. View Details
A three winding transformer comprising:
2017-05-22
A three winding transformer comprising:(a) a magnetic core;(b) low, middle and high voltage windings each inductively coupled to said magnetic core and which are coaxially wound on said magnetic core in that order;(c) two tap changers constituting a parallel circuit each including a tapped winding for tap changeover upon loading and which each have... A three winding transformer comprising:(a) a magnetic core;(b) low, middle and high voltage windings each inductively coupled to said magnetic core and which are coaxially wound on said magnetic core in that order;(c) two tap changers constituting a parallel circuit each including a tapped winding for tap changeover upon loading and which each have one end connected to said middle voltage winding and the other ends connected together;wherein further comprising middle voltage partial windings which are each connected in series between said middle voltage winding and said tap winding, and which are wound separately on the outside of said high voltage winding so that a circulating current in said parallel circuit will induce magnetic flux of opposite direction through each of the middle voltage partial windings of which one ends are connected to said middle voltage winding and of which the other ends are connected to said tap windings in said two tap changers. View Details
three winding transformer VS two winding
2017-05-10
A three winding transformer can be seen as two transformers in one and presenting a short-circuit level that will be dependent on the coupling reactance between the two secondaries. For ex., two generators feeding one common bus and with only one transformer has the least transformation cost, but the highest short-circuit level on that bu... A three winding transformer can be seen as two transformers in one and presenting a short-circuit level that will be dependent on the coupling reactance between the two secondaries. For ex., two generators feeding one common bus and with only one transformer has the least transformation cost, but the highest short-circuit level on that bus. The same generator, each one with their transformers present now the lowest Icc, but the highest transformation cost. With the 3-winding transformer, the cost of transformation should be in-between the two previous solutions, and the short circuit level will be dependent on the design of the transformer. For applications where the two secondaries are used in traction power and rectifier applications, they present a high coupling (and the same voltage) which increases the short-circuit in the secondaries ("tightly-coupled stucked secondary" design). For applications to serve continuously equal loads in both secondaries, the loosely-coupled stacked secondary design is more appropriate. But if the loads are unbalanced for long periods, this design is not appropriate. With less coupling between secondaries, the less short-circuit will be available in the secondaries. There are other aspects (11kv single phase transformer)of design impacting in more or less fault duties and losses, which is very well presented and summarized by a SKM's publication.I've seen the unloaded delta tertiary in "Y-Y-delta" transformer designs, with the primary Y with solidly grounded neutral. The primary Y neutral point at HV side must, in general, be solidly grounded to provide a SLG short-circuit level to be able to trip the overcurrent protection of the power company. The secondary Y neutral point at MV side is grounded by a resistor (ex. 400 A) to limit the damage caused by SLG fault at the consumers side. The Y-Y windings alone would make any unbalance or the existence of 3rd harmonics from consumer side to pass through to the HV side unless there is this delta winding which traps this unbalance of loading in the form of a circulating current in the delta. So, this delta tertiary works as a zero sequence filter. There are studies held by power companies which compare the advantages and disadvantages of this kind of transformer design with the Y-delta design. There are cases where the tertiary has auxiliary service loads of the substation. View Details
Three Winding Transformer - various purposes
2017-04-24
Three winding transformerTransformers may be built with a third winding, called the tertiary, in addition to the primary and secondary. Various purposes which dictate the use of a tertiary winding are enumerated below:•To supply the substation auxiliaries at a voltage different from those of the primary and secondary windings.•Static capacitors... Three winding transformerTransformers may be built with a third winding, called the tertiary, in addition to the primary and secondary. Various purposes which dictate the use of a tertiary winding are enumerated below:•To supply the substation auxiliaries at a voltage different from those of the primary and secondary windings.•Static capacitors or synchronous condensers may be connected to the tertiary winding for reactive power injection into the system for voltage control.•A delta-connected tertiary reduces the impedance offered to the zero se­quence currents thereby allowing a larger earth-fault current to flow for prop­er operation of protective equipment. Further, it limits voltage imbalance when the load is unbalanced. It also permits the third harmonic current to flow thereby reducing third-harmonic voltages.•Three windings may be used for interconnecting three transmission lines at different voltages.•Tertiary can serve the purpose of measuring voltage of an HV testing trans­former.When used for purpose (iii) above the tertiary winding is called a stabilizing winding. View Details

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