Tertiary winding in transformer

• • • • • • • • Tertiary winding in transformers have been widely used in the transmission and distribution of electricity – from power transformers up to distribution transformers. In most cases, the role of the tertiary is for voltage stability and suppression of third harmonic voltages. The discussion will begin with a brief introduction to wye-wye transformers, their advantages and potential issues associated with their operation. Wye-wye connected transformers are very common and have been used throughout the electric power industry for several reasons. The following are the most notable reasons for using wye-wye transformers. • 0° shift between primary and secondary voltages • Availability of a secondary neutral point for grounding • One end of the winding can be placed at low potential to ground (except for ungrounded neutral) Voltage Stability The conveniences offered by a wye-wye transformer come with a stability issue to the line-to-neutral voltage which may become unstable when • Unbalanced line-to-neutral loads with the primary not effectively grounded • Third harmonic currents cannot flow through the primary or secondary windings Unbalanced Loads and Isolated Primary Neutral Unbalanced Loads and Isolated Primary Neutral Image taken from Unbalanced loads on a wye-wye transformer with isolated primary neutral presents a voltage stability issue as illustrated in the above figure. The load current which flows through the neutral of the secondary side produces a ze...

The application of tertiary and stabilizing windings in liquid-immersed power transformers, as covered by IEEE Std C57.12.00™, as well as recommendations to evaluate the need or convenience of having such windings, are addressed in this guide. The primary application of this guide is for transformers and autotransformers with wye-wye-connected windings, with or without a delta-connected tertiary or stabilizing winding. Tertiary windings in conventional delta-wye and delta-delta–connected transformers are not addressed by this guide.

e4u In some high rating transformer, one winding in addition to its primary and secondary winding is used. This additional winding, apart from primary and secondary windings, is known as Tertiary winding of transformer. Because of this third winding, the transformer is called three winding transformer or 3 winding transformer. Advantages of Using Tertiary Winding in Transformer Tertiary winding is provided in electrical power transformer to meet one or more of the following requirements- • It reduces the unbalancing in the primary due to unbalancing in three phase load. • It redistributes the flow of fault current. • Sometime it is required to supply an auxiliary load in different voltage level in addition to its main secondary load. This secondary load can be taken from tertiary winding of three winding transformer. • As the tertiary winding is connected in delta formation in 3 winding transformer, it assists in limitation of fault current in the event of a short circuit from line to neutral. • In a star/star connection unbalanced load may result in neutral displacement and third-harmonic currents may circulate between lines and earth. These difficulties may be overcome by providing a delta connected stabilising (tertiary) winding with a rating sufficient to take short-circuit fault currents. Stabilization by Tertiary Winding of Transformer In star-star transformer comprising three single units or a single unit with 5 limb core offers high impedance to the flow of unbalan...

Maybe. Is you question about the need for a physical tertiary winding? If so no we don't need a physical winding. Is your question about the need for a stablizing circuit for zero sequence, or harmonic content? We most likely need this. Or is your question about the need for a power source for station power? It's got to come from somewhere. RE: Autotransformer Tertiary Winding? (Electrical) "Is your question about the need for a stablizing circuit for zero sequence, or harmonic content? We most likely need this". This explanation is what i wanted . Bu i need more detail..I mean how stablizing circuit for zero sequence and harmonic content RE: Autotransformer Tertiary Winding? (Electrical) 10 Dec 15 14:42 At present time, in most cases delta winding on (high voltage) autotransformers, as well as YNyn transformers, is not only unnecessary, but also detrimental. Magnetizing current for large unit is now less than 0.1%, and its zero sequence components are even lower. Furthermore the three-limbs core structure acts as a "phantom" delta tertiary: the high zero sequence reluctance acts as a low impedance path for zero sequence currents; proper design of flux shields allows to cope with umbalanced loads, with are by the way uncommon in high voltage transmission systems. On the other hand, the delta winding is a weak point from the mechanical point of view, being interested by short circuit currents in case of single-phase to ground fault, which are the most common ones in the HV ...

I am an electrical engineer in training working for an engineering firm. Currently I am working on some technical aspects of a substation of a Wind Farm Project. The main transformer for this substation has a rating of 34.5/138 KV (wye/wye configuration) Rating with buried Delta in Tertiary. I have checked Electrical Transmission and Distribution Reference Book from Westinghouse which shows that for Star/Star/Delta Solidly Grounded Neutrals configurations, calculated impedance parameters for the zero-sequence are the same as for positive sequence. Now I have been asked to determine whether the Buried delta in the Tertiary winding will have any contributions to the zero-sequence under Fault conditions. Any ideas? Thanks so0774 RE: Buried Delta tertiary- Zero Sequnce (Electrical) 25 Jul 05 15:30 The tertiary acts as a shunt from the H and L terminals to the reference bus in the zero phase sequence circuit.How much it affects the primary and secondary windings depends on the impedance between the tertiary and each of the primary and secondary (as shown in the Westinghouse book). Bung Life is non-linear... RE: Buried Delta tertiary- Zero Sequnce (Electrical) 26 Jul 05 09:50 Now I have been asked to determine whether the Buried delta in the Tertiary winding will have any contributions to the zero-sequence under fault conditions. The delta tertiary winding do not have any contribution to the zero-sequence under fault conditions. The delta-winding of the Yyd -transformers permits...

Nothing!😨 The neutral of the primary winding is ungrounded. Feeding a single-phase load is impossible.😲 For current to flow in phase X1, current will have to flow in phase H1. With the primary winding neutral ungrounded, the current will have to flow in phases H2 and H3. Since there are no opposing amper-turns on the secondary winding X2 and X3 current cannot flow in phases H2 and H3 hence current cannot flow in phase H1. The question becomes, how do we go around this issue?😏 The answer is to use a transformer with a tertiary winding.🙈 Note: We have assumed transformer ratios to be 1:1. Also, all parallel windings on the figure are on the same core. This helps understand how currents add up. The tertiary winding on a Y-Y connected transformer is not only used to solve the aforementioned problem. Other benefits of using a tertiary winding on a Y-Y connected transformer include: 1️⃣As can be seen in the figure above, using the tertiary winding reduces the current unbalance on the primary caused by single-phase loads on the secondary; 3I current on the phase X1 on the secondary is reflected as a current of 2I on phase H1 on the primary (a reduction of 33.3%). By the same principle, the use of tertiary winding also limits phase to ground short circuit currents. It is important to understand that greater current unbalance and single line to ground faults can lead to neutral shift even with the secondary neutral grounded. 2️⃣By connecting the tertiary winding in the Delta config...

A 3,000-degree Fahrenheit electric arc furnace prepares to receive a "charge" of scrap metal for conversion into steel Saturday at Severstal Columbus (Photo by Carmen K. Sisson/Dispatch Staff) The method of symmetrical components can be employed for analysis of the system’s response to harmonic currents provided care is taken not to violate the fundamental assumptions of the method. The method allows any unbalanced set of phase currents (or voltages) to be transformed into three balanced sets. The positive sequence set contains three sinusoids displaced 120 from each other, with the normal A-B-C phase rotation (e.g., 0, −120, 120 ). The sinusoids of the negative-sequence set are also displaced 120 , but have opposite phase rotation (A-C-B, e.g., 0, 120, −120 ). The sinusoids of the In a perfect balanced 3-phase system, the harmonic phase sequence can be determined by multiplying the harmonic number h with the normal positive sequence phase rotation. For example, for the second harmonic, h = 2, produces 2 × (0, −120, −120 ) or (0, 120, −120 ) which is the negative sequence. For the third harmonic, h = 3, produces 3 × (0, −120, −120 ) or (0, 0, 0°) which is the zero sequence. Phase sequence for all other harmonic orders can be determined in the same fashion. Since a distorted waveform in power systems contains only odd harmonic components, only odd harmonic phase sequence rotations are summarized below: • Harmonics of order h = 1, 7, 13, … are purely positive sequence. • Har...