A zigzag transformer is used for providing grounding on the transformer. Many protection engineers face difficulties applying these principles to transformers of nonstandard or unusual connections e. 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. Groundingzigzag transformers quality transformer and. Applicable standards the transformer shall be designed, manufactured and tested as per the latest revisions of ieee32. Design of zig zag earthing transformer in an 11kv system. The vector group of transformer is an essential property for successful parallel operation of transformers. Training on vector groups of transformer presented by.
Jul 20, 2018 the zigzag transformer is a special type of 3 phase transformer. Zig zag grounding transformer modeling for zerosequnce impedance calculation using finite element method diyala journal of engineering sciences, vol. The determination of vector group of transformers is very important before connecting two or more transformers in parallel. If one browses transformer sales literature, technical papers and books, and industry standards such as ieee c57. If one phase, or more, faults to earth, the voltage applied to each phase of the transformer is no longer. If the earthing current has to be limited under fault conditions, a suitable resistor can be placed in zig zag neutral terminal. The main ct secondary current magnitudes are not altered at all on the lv side. Pdf zigzag transformer some new applications with a. Star, delta or zigzag connection is indicated by the let. Transformer vector group test conditions transformer. 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. Together these make up the high voltage side of the transformer.
The zigzag vector phase shift transformer is designed to trap triplen harmonic currents 3rd, 9th, 15th, and 21st. Can you please explain that earthing transformer with the vector group and how to connect with the main transformer. You can use the zigzag transformer in two winding transformer applications, where you obtain voltage transformation and isolation with the zigzag feature. Zigzagwye zy1 or zy11 is a complex vector group used in specialized application. The clock method is used to produce the numerical index of the vector group.
Vector grouping of a three phase transformer part3zigzag. If there is a zero sequence impedance of transformer, the power and leakage impedance rating. For this, a more complex vector group the zigzag or interconnected star configuration is used. The zigzag transformer is a special type of 3 phase transformer. The dtz transformer is constructed with delta connection in primary winding and the three transposed windings at the different core legs of secondary winding. Design of delta primary transposed zigzag secondary dtz. It is not possible to generate a zero phase shift between primary and secondary with a combination of delta and star windings. The most common connection used in grounding transformers is the zigzag connection. Transformer vector group test conditions ynd1, ynd11, dyn11, ynyn0 and. It is used to create a ground for the floating system and also to filter 3rd harmonics in 3 phase ac power supply system. 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 lower diodes d2, d4, d6 form the negative group of diodes.
The transformer vector group is indicated on the name plate of transformer by. Occasionally engineers use a combination of yd and zigzag windings to achieve a vector phase shift. 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. 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 2 phases offset by 120. 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. Implement zigzag phaseshifting transformer with configurable. Vector group of transformers transformer electric power. 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. The secondary windings may be of different sizes from the primary winding to give the desired phase shift. Each zigzag design can be created with a specific impedance in mind.
Singlephase transformers may be specified for hydraulic stations because of transport. Even though this type of transformer connection is not useful in transforming power, it has many features combining star and delta type winding connections. For this a more complex vector group the zigzag or interconnected star configuration is used. In this format half of each secondary is wound on a different leg of the transformer. Zag grounding transformer a pv facility with 1 mva inverter total ac nameplate is interconnected to a. Pdf zigzag transformer some new applications with a note. It is used as a grounding transformer, creating a missing neutral connection.
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. We have already discussed all the main configurations of transformer vector groups. Vector groups are the iec method of categorizing the primary and secondary winding configurations of 3phase transformers. Transformer the transformer shall be a threephase, drytype, air cooled autotransformer with each phase having two windings connected in a zigzag configuration. A bank of three singlephase transformers cost about 1.
Pdf in large industry production facilities, twelve pulse rectifier units are often used for the conversion to dccurrent. In the case of three phase transformer windings, three forms of connection are possible. For this a more complex vector group the zig zag or interconnected star configuration is used. Points to be consider while selecting of vector group. The zig zag winding reduces voltage unbalance in systems where the load is. Zigzag grounding transformer modeling for zerosequnce impedance calculation using finite element method diyala journal of engineering sciences, vol. The vector group indicates the phase difference between the primary and secondary sides, introduced due to that particular configuration of transformer windings connection. The zigzag deltaconnected transformer presents a similar zps equivalent circuit as the zigzag transformer shown in figure 4. To specify a zigzag transformer the following information should be considered. Here yy 0 will mean its both the windings are starconnected and phase displacement between primary and secondary emfs is zero degree. The windings a1a2, a1a2 and a3a4 are wound on the same limb of the core hence they are all colored red. Earthing transformer an overview sciencedirect topics. The clock method is used to produce the numerical index of.
Electrical technology and industrial practice 6,658 views 15. Introduction to vector group the vector group marks the circuitry of windings and their phase position to each other. Here yy 0 will mean its both the windings are starconnected and phase displacement between primary and secondary emfs is zero. Transformer the transformer shall be a threephase, drytype, air cooled auto transformer with each phase having two windings connected in a zigzag configuration. The primary and secondary windings of a transformer can be connected in different configuration as shown to meet practically any requirement. 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. Significance of vector group of transformer on the nameplate of threephase transformer vector group is printed as yy 0, dd 1 etc. Three phase transformer vector grouping significance.
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. Harmonic analysis of power transformer vector groups estirj. 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. D hv winding neutral n zig zag z single phase i star y delta d lv winding zig. W7, w8, and w9 only seen herein in zigzag transformers. This application note is focusing on using transformer turn ratio measurements for diagnostic purposes. Pdf transformer vector group test conditions k pandian.
Transformer vector group test conditions transformer vector. Zigzag grounding transformers post glover resistors. The transformer primary or secondary can be connected in. The grounding transformer is commonly referred to by this connection type, the zigzag transformer.
The zigzag transformer contains six coils on three cores. 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. Fundamentals of shortcircuit protection for transformers. Positive group of diodes conduct when these have the most positive anode. Vector group test of power transformer electrical4u. 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. 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.
Contents hide 1 basic idea about transformer vector group 1. 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. 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. Windings can be connected as delta, star, or interconnec. This symbol indicates the winding connections and their relative phase displacement by means of a numerical index e.
In star to zig zag transformer is vector group possible if its yes how if its no then. 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 connection of all the windings in a threephase transformer is indicated by a vector group symbol. It consists of a capital and small letter plus a code number. The threephase transformer feeding the bridge is connected in deltastar.
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. Mar 16, 2016 the most common connection used in grounding transformers is the zig zag connection. This rectifier is also called 3 phase 6pulse diode rectifier, 3phase full wave diode rectifier. If one phase, or more, faults to earth, the voltage applied to each phase of the transformer is no longer in balance. It shall have class b insulation up to 2400 volts line to neutral or class h insulation above 2400 volts. Three phase transformer winding configurations and. Third harmonic suppression the zigzag connection in power systems to trap triple harmonic 3rd, 9th, 15th, etc. Design of zig zag earthing transformer in an 11kv system ralphchristie electrical 6 dec 07 09. Group 4 has phase displacement of 30 degree lead, i. It shall have class b insulation up to 2400 volts line to neutral or class h insulation above 2400. 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. The phase sequence or the order in which the phases reach their. The determination of vector group of transformers is very important.
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. Less costly for grounding purpose it is typically the least costly than yd and scott transformer. If there is a zero sequence impedance of transformer, the power and leakage impedance rating of the transformer may be calculated. Mar 06, 2017 transformer vector group determinationelectrical engineeringelectrical technology duration. May 04, 2012 during a phase to ground fault the zigzag transformers coils magnetic flux are no longer equal in the faulted line. Significance of vector group of transformer your electrical. Can you please explain that earthing transformer with the vector group.
Understanding vector group of transformer part 1 the primary windings are connected in one of several ways. Zigzag transformer some new applications with a note to energy efficiency article pdf available in international journal of power and energy conversion 63. And therefore the magnetic flux set up by these two currents will. This paper describes the modeling of zigzag grounding transformer wound core type.
Windings can be connected as delta, star, or interconnectedstar zigzag. 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. The transformer vector group is indicated on the name plate of. 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. Transformer vector group determinationelectrical engineeringelectrical technology duration. Winding polarity is also important, since reversing the connections across a set of windings affects the phaseshift between primary and secondary. It provides insulation between the ground and the component so that the component may not be affected by the fault currents. The common portion of an autotransformer low voltage is the common winding, and the remainder is the series winding. During a phase to ground fault the zigzag transformers coils magnetic flux are no longer equal in the faulted line. Vector grouping of a three phase transformer part3.
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