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