It is used to create a ground for the floating system and also to filter 3rd harmonics in 3 phase ac power supply system. Regardless of the configuration, star, delta or zigzag, the measurements are normally made phase to phase and comparisons are made to the estimated ratios defined by the transformer template voltages and configuration. It consists of a capital and small letter plus a code number. The zigzag transformer is a special type of 3 phase transformer. For this a more complex vector group the zig zag or interconnected star configuration is used. W7, w8, and w9 only seen herein in zigzag transformers. Here yy 0 will mean its both the windings are starconnected and phase displacement between primary and secondary emfs is zero. Contents hide 1 basic idea about transformer vector group 1. The transformer vector group is indicated on the name plate of. For this, a more complex vector group the zigzag or interconnected star configuration is used. D hv winding neutral n zig zag z single phase i star y delta d lv winding zig.
It shall have class b insulation up to 2400 volts line to neutral or class h insulation above 2400 volts. Design of zig zag earthing transformer in an 11kv system. You can use the zigzag transformer in two winding transformer applications, where you obtain voltage transformation and isolation with the zigzag feature. A zigzag transformer is a specialpurpose transformer with a zigzag or interconnected star winding connection, such that each output is the vector sum of two 2 phases offset by 120. The transformer primary or secondary can be connected in. Training on vector groups of transformer presented by.
Mar 06, 2017 transformer vector group determinationelectrical engineeringelectrical technology duration. P department of electrical and electronics engineering loyola institute of technology and science loyola nagar, thovalai, tamilnadu629302, india abstract transformer is the most important unit in an electrical distribution network. The secondary windings may be of different sizes from the primary winding to give the desired phase shift. The capital letter a, b, c refers to the hv winding and the lower case a, b, c to the lv winding with a, b, c for. A zigzag transformer is a specialpurpose transformer with a zigzag or interconnected star winding connection, such that each output is the vector sum of two. Pdf zigzag transformer some new applications with a. Design of zig zag earthing transformer in an 11kv system ralphchristie electrical 6 dec 07 09. Introduction to vector group the vector group marks the circuitry of windings and their phase position to each other. Can you please explain that earthing transformer with the vector group and how to connect with the main transformer. For this a more complex vector group the zigzag or interconnected star configuration is used. The grounding transformer is commonly referred to by this connection type, the zigzag transformer. Regardless of the configuration, star, delta or zig zag, the measurements are normally made phase to phase and comparisons are made to the estimated ratios defined by the transformer template voltages and configuration. Zigzag transformer some new applications with a note to energy efficiency article pdf available in international journal of power and energy conversion 63.
Here yy 0 will mean its both the windings are starconnected and phase displacement between primary and secondary emfs is zero degree. If the earthing current has to be limited under fault conditions, a suitable resistor can be placed in zig zag neutral terminal. W 3 and w 6 windings w 7, w 8 and w 9, used herein for zigzag windings, are hard to classify into a particular leg since zigzag windings crossconnect core phase legs. Zigzagwye zy1 or zy11 is a complex vector group used in specialized application. This rectifier is also called 3 phase 6pulse diode rectifier, 3phase full wave diode rectifier. Transformer the transformer shall be a threephase, drytype, air cooled auto transformer with each phase having two windings connected in a zigzag configuration. The vector group of transformer is an essential property for successful parallel operation of transformers. In star to zig zag transformer is vector group possible if its yes how if its no then. The zigzag transformer contains six coils on three cores. May 04, 2012 during a phase to ground fault the zigzag transformers coils magnetic flux are no longer equal in the faulted line. The most common connection used in grounding transformers is the zigzag connection. Earthing transformer an overview sciencedirect topics. The lower diodes d2, d4, d6 form the negative group of diodes. Pdf zigzag transformer some new applications with a note.
Hence every electrical power transformer must undergo through vector group test of transformer at factory site for ensuring the customer specified vector group of transformer. Significance of vector group of transformer your electrical. If one phase, or more, faults to earth, the voltage applied to each phase of the transformer is no longer in balance. The dtz transformer is constructed with delta connection in primary winding and the three transposed windings at the different core legs of secondary winding. The main ct secondary current magnitudes are not altered at all on the lv side. Vector group test of power transformer electrical4u. Jul 20, 2018 the zigzag transformer is a special type of 3 phase transformer. Vector grouping of a three phase transformer part3. Basic idea about transformer vector group in theory of a threephase transformer works like three equal and separated singlephase transformers working separately with three phase system with shared limbs. The two most common configurations are the delta, in which the polarity end of one winding is connected to the nonpolarity end of the next, and the star, in which all three nonpolarities or polarity ends are connected together. Vector group of transformers transformer electric power. It provides insulation between the ground and the component so that the component may not be affected by the fault currents. The clock method is used to produce the numerical index of.
The connection of all the windings in a threephase transformer is indicated by a vector group symbol. Design of delta primary transposed zigzag secondary dtz. Vector groups are the iec method of categorizing the primary and secondary winding configurations of 3phase transformers. If one browses transformer sales literature, technical papers and books, and industry standards such as ieee c57. It is not possible to generate a zero phase shift between primary and secondary with a combination of delta and star windings. Points to be consider while selecting of vector group. Vector grouping of a three phase transformer part3zigzag. Harmonic analysis of power transformer vector groups estirj. If you need a neutral for grounding or for supplying singlephase line to neutral loads when working with a 3wire, ungrounded power system, a zigzag connection. Fundamentals of shortcircuit protection for transformers. This symbol indicates the winding connections and their relative phase displacement by means of a numerical index e.
If there is a zero sequence impedance of transformer, the power and leakage impedance rating of the transformer may be calculated. The power transformer is with deltadelta dd0 vector group for a 3311kv class transformer of 4 mva for this if neutral is required we need earthing rtransformer. This paper describes the modeling of zigzag grounding transformer wound core type. The clock method is used to produce the numerical index of the vector group. And therefore the magnetic flux set up by these two currents will.
The zigzag vector phase shift transformer is designed to trap triplen harmonic currents 3rd, 9th, 15th, and 21st. Zigzag grounding transformer modeling for zerosequnce impedance calculation using finite element method diyala journal of engineering sciences, vol. Transformer vector group determinationelectrical engineeringelectrical technology duration. Zag grounding transformer a pv facility with 1 mva inverter total ac nameplate is interconnected to a. Winding 2 zig zag r2 l2 the resistance and leakage inductance of the windings 2 of the singlephase transformers used to implement the primary winding of the zigzag phaseshifting transformer. Positive group of diodes conduct when these have the most positive anode. Calculation for sizing zigzag transformer electric. If the delta winding is loaded, the transformer ppsnps equivalent circuit includes a 90 phase shift and is similar to that of a twowinding transformer with an impedance derived from the star equivalent of the. The common portion of an autotransformer low voltage is the common winding, and the remainder is the series winding. It shall have class b insulation up to 2400 volts line to neutral or class h insulation above 2400. Windings can be connected as delta, star, or interconnec.
Singlephase transformers may be specified for hydraulic stations because of transport. In the table of groups we also included transformer zigzag connections. Implement zigzag phaseshifting transformer with configurable. Groundingzigzag transformers quality transformer and. Electrical technology and industrial practice 6,658 views 15. The threephase transformer feeding the bridge is connected in deltastar.
Pdf in large industry production facilities, twelve pulse rectifier units are often used for the conversion to dccurrent. This application note is focusing on using transformer turn ratio measurements for diagnostic purposes. The transformer vector group is indicated on the name plate of transformer by. In this format half of each secondary is wound on a different leg of the transformer. Pdf transformer vector group test conditions k pandian. The zigzag deltaconnected transformer presents a similar zps equivalent circuit as the zigzag transformer shown in figure 4. Zig zag grounding transformer modeling for zerosequnce impedance calculation using finite element method diyala journal of engineering sciences, vol. Can you please explain that earthing transformer with the vector group. Third harmonic suppression the zigzag connection in power systems to trap triple harmonic 3rd, 9th, 15th, etc. The vector group indicates the phase difference between the primary and secondary sides, introduced due to that particular configuration of transformer windings connection. Three phase transformer vector grouping significance. Pdf modeling of phaseshift zigzag transformers in atp. Group 4 has phase displacement of 30 degree lead, i. A transformer of group 3 can be connected in parallel with that of group 4 by cross connecting any two of the three external connections on hv side, without any other changes.
Significance of vector group of transformer on the nameplate of threephase transformer vector group is printed as yy 0, dd 1 etc. During a phase to ground fault the zigzag transformers coils magnetic flux are no longer equal in the faulted line. It is used as a grounding transformer, creating a missing neutral connection. If one phase, or more, faults to earth, the voltage applied to each phase of the transformer is no longer. If there is a zero sequence impedance of transformer, the power and leakage impedance rating. The zig zag winding reduces voltage unbalance in systems where the load is. Even though this type of transformer connection is not useful in transforming power, it has many features combining star and delta type winding connections. The power transformer is with deltadelta dd0 vector group for a 3311kv class transformer of 4 mva for this if neutral is required we need. Star, delta or zigzag connection is indicated by the let. Then ret 670 software features can be used in a usual way to compensate for this special transformer, as if it were a standard twowinding transformer with vector group yy0. Zig zag transformer offers low impedance path to zero sequence components under fault conditions so it can be perfectly used as earthing transformer with and earthing reference. Together these make up the high voltage side of the transformer. It should be noted that it is not possible to generate a zero phase shift between primary and secondary with a combination of delta and star windings. Three phase transformer winding configurations and.
Transformer vector group test conditions transformer vector. The phase sequence or the order in which the phases reach their. A zigzag transformer is used for providing grounding on the transformer. Applicable standards the transformer shall be designed, manufactured and tested as per the latest revisions of ieee32. Each zigzag design can be created with a specific impedance in mind. Transformer vector group test conditions transformer. We have already discussed all the main configurations of transformer vector groups. Understanding vector group of transformer part 1 the primary windings are connected in one of several ways. May 23, 2012 the vector group indicates the phase difference between the primary and secondary sides, introduced due to that particular configuration of transformer windings connection. Occasionally engineers use a combination of yd and zigzag windings to achieve a vector phase shift.
Grounding transformers are used for obtaining a grounded neutral on three phase, threewire systems, providing a return path for zero sequence current generated by the loads in the system or by the fault currents. The transformer shall be continuously rated for the. Many protection engineers face difficulties applying these principles to transformers of nonstandard or unusual connections e. A bank of three singlephase transformers cost about 1. In zig zag transformer connection, there are three windings on each of the three limbs of the core, one for primary and two for secondary. Transformer the transformer shall be a threephase, drytype, air cooled autotransformer with each phase having two windings connected in a zigzag configuration. Zigzag grounding transformers post glover resistors.
The windings a1a2, a1a2 and a3a4 are wound on the same limb of the core hence they are all colored red. Winding polarity is also important, since reversing the connections across a set of windings affects the phaseshift between primary and secondary. In the case of three phase transformer windings, three forms of connection are possible. The primary and secondary windings of a transformer can be connected in different configuration as shown to meet practically any requirement. Winding 2 zigzag r2 l2 the resistance and leakage inductance of the windings 2 of the singlephase transformers used to implement the primary winding of the zigzag phaseshifting transformer. The delta primary transposed zigzag secondary dtz transformer has been designed and used to reduce the bad impacts of the harmonic in the distribution power system.
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