power systems loss

Completed and Authored by: Chetan C. Adalja M.L. Jain, Technology Department, EMCO Limited, Thane India INTRODUCTION The stray losses in a transformer comprise winding stray losses, viz. eddy loss and circulating current loss; the loss in the edge stack (smallest packet of the core limb); and the loss in structural parts, viz. frame, flitch plate and tank. Core loss at the impedance voltage being insignificantly low, is not considered in the present analysis. In case of large generator transformers, stray losses due to high current carrying leads also become significant.

LOADING POWER TRANSFORMERS BEYOND NAMEPLATE RATING:SIMULATION SOFTWARE VIDEO Power transsformers are one of the most critical asset in any power system network. Transformers undergoe different load cycles that vary depending the time of day and year in power system conditions. For example, the daily load cycle tends to increase during the early hours of the morning before people leave for work and in the evning after they arrive home. Similarly, a yearly load cycle during the hot summer months when high ambient temperature cause consumers to ramp up their air conditioners and use more electrical power. During contingecy conditions, single or variuos network elemaents such as transsmission lines, generators or transformers might be isolated from the power system. As a consequence,transformers can become overloaded by reaching magnitudes above its maximum nameplate capability affecting and possible reducing the overall life of the transformer.During transformer overloads, theextra pow

IEEE STD C57.93-1995: GUIDE FOR INSTALLATION OF LIQUID-IMMERSED POWER TRANSFORMERS This IEEE standard aims to show the appropriate way of shipping, handling, inspecting, installing, and maintaining liquid-immersed power transformers. Power transformers are defined in this guide to be above 501kVA and which its secondary voltage should be equal or above 1000V. Two sizes of transformers are basically discussed in this guide, those which are 10MVA and above with a primary voltage winding of 69kV and above and transformers which are 501kVA to 10MVA (oil or ail cooled) having a primary voltage winding of 69kV and below. 501kVA TO 10 MVA (OA) LIQUID-IMMERSED POWER TRANSFORMERS This type of transformers are said to be usually a station or pad-mount installed transformers. Its tanks are tightly sealed to preserve the liquid or inert gas used as insulation. Radiators which are usually provided by manufacturer for cooling can be welded directly to the tank. Transformers with lower capacity ar

K-FACTOR TRANSFORMER K factor has been a basis for measuring the capability of a transformer to carry nonlinear loads. It is the factor to determine whether the transformer can withstand transformer heating due to harmonic load currents. ANSI/IEEE Std.C57-110 is the primary reference when it comes to the discussion of k-factor in a transformer. Below are selected articles discussing the k-factor and the k-rated transformers. FAQs are also available for your reference to make yourself familiar with the nature of use of this k-factor for transformer. K-Factor Definition K-factor is a weighting of the harmonic load currents according to their effects on transformer heating, as derived from ANSI/IEEE C57.110. A K-factor of 1.0 indicates a linear load (no harmonics). The higher the K-factor, the greater the harmonic heating effects. When a non-linear load is supplied from a transformer, it is sometimes necessary to derate the transformer capacity to avoid overheating and subsequent ins

(From npsc2010.uceou.edu ) The performance of transformer, the most ancient power system static element, is affected due to presence of distortion in the input supply voltage and non-linearity in the load current. Due to extensive use of modern power electronics controlled devices, the degree of non-linearity in the load current has increased in recent years. 

(From http://www.metglas.com/ ) Metal alloys typically possess crystalline atomic structures in which individual atoms are arranged in ordered, repeating patterns. Amorphous-metal alloys differ from their crystalline counterparts in that they consist of atoms arranged in near random configurations devoid of long-range order.

Generally, two main types of losses exist during an electrical power transformation and are also inherent in every transformer. We have the load loss also known as the winding loss where this type of loss depends on the loading of the transformer, the higher the load, the higher the loss that it can generate. Also, we have the no-load loss also known as the core loss where this is type of loss is constant in every transformer regardless it is fully loaded or no-load at all.

CALCULATION OF TRANSFORMER LOSSES UNDER NON-SINUSOIDAL CURRENTS USING:TWO ANALYTICAL METHODS AND FINITE ELEMENTS ANALYSIS An article discussing effects of non-sinusoidal currents to the transformer losses. This article was made through the effort of M.Yazdani-Asrami, M.Mirzaie and A.Shayegani-Akmal of Babol University of Technology, Babol, Iran. Introduction Transformers are the most important component in power system and are interfaces between consumers and suppliers. Contemporary with ever-increasing electrical energy demand, the number and capacity of installed transmission transformers and especially distribution transformers are increasing. However, considering the point that the efficiency of these components is 97-99%, there was not enough attention to the amount of loss and performance of transformers. By considering the large number of transformers in transmission and distribution networks, it can be seen that the total power loss of these components is high. So, any reduct

TRANSFORMER LOSSES AND THE EFFECT OF HARMONIC CURRENTS ON THESE LOSSES TUTORIAL DISCUSSION (From ANNEX D of IEEE STD C57.110-1998) Power transformers with ratings up to 50 MVA are almost always of core form construction. High-voltage and low-voltage windings are concentric cylinders surrounding a vertical core leg of rectangular or circular cross section. The vertical core legs and the horizontal core yoke members that constitute the magnetic circuit are made up of thin steel laminations. In the top and bottom yoke regions there are usually external clamping structures (clamps) that may be made of either metallic or insulating materials. Oil-immersed transformers are contained within a steel tank, while dry-type transformers may be either freestanding or surrounded by a metal enclosure. If direct current is passed through the transformer winding conductors, a simple I 2R loss will be produced, where R is the dc resistance of the winding. However, if an alternating current (ac) of the

HARMONICS EFFECT TO TRANSFORMER LOSSES How does harmonics contributes to transformer losses? Harmonics or harmonic distortion in electrical definition is a type of disturbance both found in the voltage and current waveform. Most common source of this distortion is primarily associated with non-linear loads like electronic loads. These electronic loads can either be from a single phase or three-phase form. Harmonics is said to be caused by a non-sinusoidal load currents usually are blamed from commercial power supplies and motor drives like personal computers and other electronically driven devices. Harmonic distortions to either voltage or current are also reflective to the other according to the ohm’s law principle. Previously we have discussed that transformer loss are usually categorized as no-load loss (referred sometimes as excitation loss), load loss (also called as impedance loss), and total loss (the sum of no-load loss and load loss). If you try to recall our discussions re

PARALLELING TRANSFORMER’S LOADING CONSIDERATIONS Paralleling transformers has been practiced mostly in commercial and industrial facilities along with electric utilities where reliability and the quality of power is the main objective. For many years, it has been a practice that transformers installed for paralleling have the same kVA, turns ratio and impedances which served also as a reason why most of the engineers today is having a hard time understanding load sharing and circulating currents. Often times during transformer replacement or upgrades, they tend to not know the impact of paralleling transformers with different parameters and could later result to transformer failures. Simple transformer paralleling with the same kVA, turns ratio and impedance is not enough in practicing this kind of activity. An engineer must consider all possible scenarios and simulate the effects of his decisions. The most appropriate type of transformers that should be use in paralleling must have t

SPOTLIGHT ON MODERN TRANSFORMER DESIGN BOOK DOWNLOAD Increasing competition in the global transformer market has put tremendous responsibilities on the industry to increase reliability while reducing cost. Spotlight on Modern Transformer Design introduces a novel approach to transformer design using artificial intelligence (AI) techniques in combination with finite element method (FEM). Today, AI is widely used for modeling nonlinear and large-scale systems, especially when explicit mathematical models are difficult to obtain or completely lacking. Moreover, AI is computationally efficient in solving hard optimization problems. On the other hand, FEM is particularly capable of dealing with complex geometries, and also yields stable and accurate solutions. Many numerical examples throughout the book illustrate the application of the techniques discussed to a variety of real-life transformer design problems, including: • problems relating to the prediction of no-load losses; • winding

TRANSFORMER PARALLELING TUTORIAL & DOWNLOAD In actual electrical engineering application, sometimes an engineer would sacrifice logic in order for him to achieve a greater purpose. Unlike in theory, actual engineering practice requires decision making situations where we base our decisions on more than just what we compute and what we think as the most correct action. Say for instance in paralleling tansformers, generally, it is not recommended to use two smaller size transformers, to be used in one circuit by paralleling in replacement for using a single full-size transformer with the same capacity with latter set-up. Logically speaking, utilizing two transformers will be more expensive compared to using a single unit transformer both with the same transformation capacity. Not to mention the fact that the combined losses of two transformer will be higher to that of a single transformer especially when it comes to its no-load loss  considerations. Also, a two-unit transformer will

IEEE STD C37.91-2000: GUIDE FOR PROTECTIVE RELAY APPLICATIONS TO POWER TRANSFORMER Power Transformers are not only one of the most important piece of electrical device in the power system with respect to its functions but also the most expensive among all other devices found in an electrical substation. Furthermore, once a power transformer is out of service during its operation, the electric utility can not simply replace it in a short period of time not unless one has a spare which is also, mind you, can be very impractical. An electric utility can not afford to loss a power transformer because it would also mean a loss in revenue and for a manufacturer’s perspective is a loss in production. A power transformer, in which I think everybody would agree, is a very complicated form of electrical apparatus. While in operation, it is subjected to a quite number of threats which can be unpredictable, one of which is a fault that can be very damaging. Proper care and maintenance are always

TRANSFORMER HANDBOOK: ABB This Transformer Handbook prepared by ABB contains a wide range of power and distribution transformers that aims to serve as a guide in understanding, selection, ordering, operation and maintenance of this transformers. The construction of this devices follows standards to the likings of the customers including but not limited to IEC, CENELEC, and ANSI/IEEE. This Handbook although focuses on ABB products, does not significantly differs to the common practice in specifying transformers and ABB based this handbook on their knowledge and experience. Listed below are the main topics that were discussed in this handbook: Every point found in the list are carefully considered. Also, a portion of this handbook tackles all the available standards that are relevant to transformer information. Transformer Types and their Application Quality, Internal Control, Sustainability Loss Capitalization and Optimum Transformer Design Information Required with Enquiry and Ord

CONSTRUCTING POWER TRANSFORMERS: VIDEO Construction of power transformers undergoes a rigorous process. A video presentation of ABB shows the step-by-step process in manufacturing this complex electrical power apparatus. Shown also in this video is the part-by-part construction, from winding, core, tank, accesories up to the delivery of the power transformer is clearly explained in this video. ABB is a major transformer manufacturer throughout the world. ABB power transformers are built and designed to meet the individual customer's needs. This experienced attendance to details lies behind the success of ABB's transformers. This approach is carried throughout the manufacturing process: design, core, winding, drying, tank, quality assurance, assembly, testing, transport and installation and support.

TRANSFORMER CATALOGUE: A SAMPLE FROM MANUFACTURER Transformers are one of the primary components for the transmission and distribution of electrical energy. Their design results mainly from the range of application, the construction, the rated power and the voltage level. The scope of transformer types starts with generator transformers and ends with distribution transformers. Transformers which are directly connected to the generator of the power station are called generator transformers. Their power range goes up to far above 1000 MVA. Their voltage range extends to approx.1500 kV. The connection between the different highvoltage system levels is made via network transformers (network interconnecting transformers). Their power range exceeds 1000 MVA. The voltage range exceeds 1500 kV. Distribution transformers are within the range from 50 to 2500 kVA and max. 36 kV. In the last step, they distribute the electrical energy to the consumers by feeding from the high-voltage into the low-

J & P TRANSFORMER BOOK DOWNLOAD By:Martin J. Heathcote Maintaining appropriate power systems and equipment expertise is necessary for a utility to support the reliability, availability, and quality of service goals demanded by energy consumers now and into the future. However, transformer talent is at a premium today, and all aspects of the power industry are suffering a diminishing of the supply of knowledgeable and experienced engineers. Now in print for over 80 years since initial publication in 1925 by Johnson & Phillips Ltd, the J & P Transformer Book continues to withstand the test of time as a key body of reference material for students, teachers, and all whose careers are involved in the engineering processes associated with power delivery, and particularly with transformer design, manufacture, testing, procurement, application, operation, maintenance, condition assessment and life extension. Current experience and knowledge have been brought into this thirteenth

POWER TRANSFORMER SPECIFICATION ISSUES: GUIDE This presentation was originally made by the Electric Power Engineering Centre (EPECentre) at the University of Canterbury in Christchurch, New Zealand. The information found in this document is based on a power transformer specification workshop held in July 2007. The EPECentre takes no responsibility for damages or other liability whatsoever from the use of this document. This includes any consequential damages resulting from interpretation of material. A detailed technical specification of a power transformer is an effective tool in keeping the relationship between a manufacturer and the buyer in harmony. On the Buyer's perspective, having a comprehensive specification for his desired power transformer will  create an effective communication to the manufacturer on what he wants the contractor to deliver. Likewise, from a manufacturer'sperspective, through a clear power transformer technical specification, he can be able to prov

IEEE STD C57.91-1995: GUIDE FOR LOADING MINERAL-OIL-IMMERSED TRANSFORMERS Applications of loads in excess of nameplate rating involve some degree of risk. While aging and long time mechanical deterioration of winding insulation have been the basis for the loading of transformers for many years, it is recognized that there are additional factors that may involve greater risk for transformers of higher megavoltampere and voltage ratings. The risk areas that should be considered when loading transformers beyond nameplate rating are listed below. This guide is applicable to loading 65 C mineral-oil-immersed distribution and power transformers. Guides for loading, IEEE Std C57.91-1981 (prior edition), IEEE Std C57.92-1981, and IEEE Std C57.115-1991 (redesignation of IEEE Std 756) are all combined in this document as the basic theory of transformer loading is the same, whether the subject is distribution transformers, power transformers 100 MVA and smaller, or transformers larger than 100 M

IEEE STD 62-1995: GUIDE FOR DIAGNOSTIC FIELD TESTING OF ELECTRIC POWER APPARATUS-PART 1: OIL FILLED POWER TRANSFORMERS, REGULATORS, AND REACTORS Majority of the power transformers used by electric utilities are oil-filled including regulators and reactors. Since it is important to have these power apparatus in their top performance, it is therefore imperative to keep its reliability and useful life to the maximum. The early detection of possible defects is very important in this nature of operation. One way of keeping this requirement met is through regular diagnostic evaluation. By testing and measurements, maintenance engineers can be able to know the present condition of these electrical apparatus. However, in order for them to have a reference point they should first establish a benchmark values that future results could be compared to. With these values a clear evaluation can be obtained and to know how the apparatus is doing. Usually this benchmark value is from the first measure

ENERGY EFFICIENT TRANSFORMERS BOOK BY: Barry W. Kennedy CHECK OUT THIS BOOK! The author wrote this book hoping that he may able to help users of transformers save money as well as energy. For those who are new to Transformers, Chapter 2 entitled "Tranformer Characteristics" will provide you with the necessary fundamentals on transformer theory, construction, operation, and energy consumption. Included also in this book that are signficant to our topic of "System's Loss" are the following;Transformer Efficiency, Value of Losses, Transformer Cost, Transformer Economics,Transformer Replacement, High Efficiency Transformers, etc. Purchase book at Amazon

ELECTRIC POWER TRANSFORMER ENGINEERING BOOK DOWNLOAD This is an excellent book that tackles all about transformers, and I mean all kinds of transformers. I recommend this book if you want to know more about Power Transformers. Some of the power transformer discussion is about "Rating & Classification", "Efficiency, Losses, &Regulation", "Construction", "Accesory Equipment" and "Modern & Future Dvelopments". Here are some of the topics that are discussed in this book. Power Transformers Distribution Transformers Phase-Shifting Transformers Rectifier Transformers Dry-Type Transformers Instrument Transformers Step-Voltage Regulators Constant-Voltage Transformers Reactors Again, I highly recommend this book. For me, this a complete source for all your information needs regarding transformers. It even includes procedure for Power Transformer Installation. DOWNLOAD THIS BOOK NOW!

PROTECTING POWER TRANSFORMERS FROM COMMON ADVERSE CONDITIONS PDF Power transformers play a significant role in power system delivery. Proper application of relay elements that monitor a transformer’s thermal state and through-faults can provide both short and long term benefits. These benefits include: •  Transformer overload protection, including cyclic overloads •  Continuous transformer thermal status indication that allows the system operator to make transformer loading decisions based on transformer thermal state •  Cooling system efficiency indication •  Records of cumulative per phase I2t values as seen by the transformer •  Settable I2t alarm thresholds that can notify the system operator of excessive through-fault current seen by the transformer •  Cumulative I2tvalues as a measure to prioritize transformer maintenance Overexcitation is a system condition and is not limited to generating stations. Proper application of Volts/Hz elements can prevent damage to tran

POWER TRANSFORMER LIFE-CYCLE COST REDUCTION CASE STUDY ANALYSIS PDF Using long-term thermal loss-of-life analysis, probability of failure analysis, and economic analysis, it is shown that power transformers may be kept in service longer than is the  present policy in many utilities. This analysis, coupled with the use of on-line dissolved gas analysers (DGA’s) and other improved monitoring equipment can instil confidence in a longer in-service life policy for large transformers. An actual Manitoba Hydro transformer replacement scenario is presented. The cost of the monitoring equipment is significantly less than the potential savings. READ MORE >>>

POWER TRANSFORMER MAINTENANCE AND ACCEPTANCE TESTING PDF This manual contains a generalized overview of the fundamentals of transformer theory and operation. The transformer is one of the most reliable pieces of electrical distribution equipment. It has no moving parts, requires minimal maintenance, and is capable of withstanding overloads, surges, faults, and physical abuse that may damage or destroy other items in the circuit. Often, the electrical event that burns up a motor, opens a circuit breaker, or blows a fuse has a subtle effect on the transformer. Although the transformer may continue to operate as before, repeat occurrences of such damaging electrical events, or lack of even minimal maintenance can greatly accelerate the evenhml failure of the transformer. The fact that a transformer continues to operate satisfactorily in spite of neglect and abuse is a testament to its durability. However, this durability is no excuse for not providing the proper care. Most of the correcte

TRANSFORMER TESTS AND MEASUREMENTS Previously, we have discussed that a Power Transformer is the biggest, heaviest and the most expensive piece of equipment that can be found in a substation. Furthermore, the role it plays in the system is also very important that an electric utility can not afford to loss it during its operation. Proper care and maintenance are always carefully observed to ensure that a power transformer is in its top performance. Making sure that it performs well is a priority in every electric distribution utility much more to a commercial company that depends on electric power for its production and a loss of power means also a loss of revenue. To make sure that a transformer is doing its expected performance and future failures could be avoided, tests and measurements are periodically exercised to know whether the said transformer is doing fine or will it need to be replaced. Due to the complexity of the transformer’s construction and operation, plenty of tests

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ETAP LESSON 8:INSERT PROTECTIVE DEVICE WITH ETAP SOFTWARE Learn how to add protective devices like circuit breakers, switches, fuses, etc. to an existing one-line without breaking any equipment connections.

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TRANSFORMERS BOOK By: Bharat Heavy Electricals Limited CHECK OUT THIS BOOK!

TRANSFORMER ENGINEERING:DESIGN AND PRACTICE BOOK By: Shrikrishna V. Kulkarni, S. V. Kulkarni, S. A. Khaparde CHECK OUT THIS BOOK!

POWER TRANSFORMERS:PRINCIPLES AND APPLICATIONS By: John J. Winders Jr.  CHECK OUT THIS BOOK!

GUIDE FOR THE EVALUATION OF LARGE POWER TRANSFORMER LOSSES This guide is from United States Department of Agriculture Rural Utilities Service RUS Bulletin 1724-301. Stated in this guide is that Losses and Purchase price should be considered when deciding which transformer to purchase. The purpose of this bulletin is to present a uniform approach that can be used to determine the dollar value of these losses over the life of the transformer. The three different types of transformer losses that should be evaluated separately are: a. Load losses (sometimes called copper or coil losses); b. No-load losses (sometimes called core or iron losses); and c. Auxiliary losses (electric fan losses, other such equipment losses).

C57.120.1991 IEEE LOSS EVALUATION GUIDE FOR POWER TRANSFORMERS AND REACTORS   This IEEE loss evaluation guide was made to help electrical practitioners provide a method of establishing the economic value of the electric power intended to supply the losses of a transformer or reactor. With the use of this C57.120.1991 standard, decision-makers can have a guide for the proper weighing of alternatives when it comes to transformer selection that considers the cost-benefit relationship between these choices. Normally, it is a loss evaluation relative to economic benefit of a high-first-cost, low-loss unit against one with a lower-first-cost but with higher losses. Beside the users of transformers, transformer manufacturers can also benefit with this standard by using this as guide a mean to optimize their design and provide the most economical unit to bid and manufacture.

IEEE STANDARD FOR TRANSFORMERS TABLE OF CONTENTS Listed below are some of the IEEE subscription for Power, Distribution and Regulating Transformers. Unapproved drafts are proposed IEEE standards. As such, these documents are subject to change. So, take a precautionary actions in using this standards. Because these drafts are unapproved, they must not be utilized for any conformance/compliance purposes. 1-2000 (R2005) IEEE Recommended Prasctice--General Principles for Temperature Limits in the Rating of Electric Equipment and for the Evaluation of Electrical Insulation 62-1995 (R2005) IEEE Guide for Diagnostic Field Testing of Electric Power Apparatus--Part 1: Oil Filled Power Transformers, Regulators, and Reactors 259-1999 (R2004)    IEEE Standard Test Procedure for Evaluation of Systems of Insulation for Dry-Type Specialty and General Purpose Transformers 315-1975 (R1993) IEEE Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters) Bound

EFFECTS OF TRANSFORMER LOADING TO LOSSES Transformers, especially substation transformers are subjected everyday to loads that varies in any given period of time. The behaviour of its transformer loading is dependent to the nature of customers that are connected to it. The load profile of residential loads is not identical to the commercial ones the same with the commercial loads not identical to the industrial ones. It is also a given fact that a substation caters a mixture of these loads thus we can conclude that the transformer loading behaviour of one substation will not be necessarily similar to its adjacent substations. Sample of Transformer Loading Profile

EDDY CURRENT LOSSES IN TRANSFORMER WINDINGS AND CIRCUIT WIRING By: Lloyd H.Dixon Jr. As  switching  power  supply  operating  frequencies  increase,  eddy  current  losses  and parasitic inductances  can greatly  impair  circuit performance.  These  high  frequency  effects  are caused  by  the  magnetic  field  resulting  from current  flow  in transformer  windings  and circuit wiring.This  paper is intended  to provide  insight  into these  phenomena  so  that  improved  high  frequency. performance  can  be  achieved.  Among other  things,  it  explains  (I)  why  eddy  current losses increase so dramatically  with  more  winding  layers,  (2)  why  parallelling  thin  strips  doesn't  work,  (3)  how  passive conductors  (Faraday shields  and  C. T .windings)  have  high  losses, and  (4)  why  increasing  conductor  surface  area will  actually  worsen  losses and  parasitic  inductance  if  the  configuration  is  not  correct. READ MORE >>>

AUXILIARY LOSSES IN POWER TRANSFORMER Beside Load loss and No load loss, another type of loss concerning substation transformers and are usually applicable to power transformers that are rated 5000kVA and above is the auxiliary loss. Auxiliary loss is a type loss that represents the electrical load of the transformer auxiliaries. This are the one that are utilize to operate the cooling fans and pumps of the transformer as discussed in our Load Loss topic. Although some utilities disregard this due to the fact that it does not impact the system’s loss in comparison to the Load and No-load losses, still technically they are still considered as losses. On the other hand, some electric utilities installs meters to properly account the power used in operating its substation auxiliaries thus, this can no longer be considered as losses.

NO-LOAD LOSS IN POWER TRANSFORMER NO LOAD LOSS is the other type of transformer loss which is also known as CORE LOSS. Core loss exists for the reason that transformers of any kind requires electrical currents and magnetic fields that is needed to magnetize the core of the transformer, the sad part is that they are present whenever the transformer is energized whether loaded or unloaded. Unlike the winding loss, core loss requires a constant value regardless of the transformer load; in short, core loss does not vary as transformer load changes. For example, if a power transformer has a core loss of 24kW, 24kW of power must be drawn from the source of supply to cover these losses at all times when the transformer is energized, even if the transformer load side are open.

LOAD LOSS IN POWER TRANSFORMER LOAD LOSS also known as winding loss is similar to the analysis of a transmission line represented by the I squared R formula. Load loss is called this way because the losses here vary with the square of the load current. Higher load means higher loss and lower load means lower loss. In the past, load loss is referred to as copper loss but later this has been corrected since modern transformers now use aluminium windings in substitute for copper. Losses occurring in transformers are mostly load losses, so the maximization of the transformer use with respect to losses is a very vital form of analysis.  

SUBSTATION TRANSFORMER LOSSES The primary function of a power transformer is to transform system voltage from one nominal level to another. The transformer has to be capable of carrying (within the guidelines of ANSI/IEEE Std. C57.92) the power flow for its particular location in the system under various operating conditions and contingencies, such as line or transformer outages. After we have discussed the contribution of transmission lines and its effects to the level of system’s loss in every utility, we now move to the next part of our discussion which is the Power Transformer. Unlike transmission lines, the functions of power transformer in the system are somewhat more complicated. Power transformers, also known as substation transformers, steps down voltage level received from transmission lines from a higher voltage down to primary distribution levels. This exists in every electric utility due to the fact that most distributors purchase wholesale electricity at transmission vol

SUBSTATION WITH POWER TRANSFORMER A substation in a power system is the one that usually houses the Power transformer. This is also the place where the transformation of voltage occurs. Power transformers found in substations may be either autotransformers or multi-winding conventional transformers. A three-phase installation may consist of a three-phase unit or three single-phase units. The decision as to what type of transformer to purchase depends on such factors as initial installed cost, maintenance costs, operating cost (efficiency), reliability, etc. Three-phase units have lower construction and maintenance costs and can be built to the same efficiency ratings as single-phase units. The initial cost of a three-phase transformer is usually approximately one-third less than four single-phase units. Additionally, the exposure of three-phase units to long outages can be minimized system-wide when a mobile substation or transformer is available for backup in case of failure. RUS Bul

What are the name of the basic parts of a Power Transformer? We can not deny the fact that only a handful of electrical engineering students are presently familiar with power transformers especially on what it looks like. Unlike a transformer we found in our homes, a power transformer’s appearance and construction is somewhat more complicated. It is not just a simple winding with a primary and secondary terminal although basically any transformer has one. The function that a power transformer plays in an electrical system is very important that an electric utility can not afford to loss it during its operation. Our discussion here will focus more on the basic parts and functions of a power transformer that are usually tangible whenever you go to a substation . Although not all power transformers are identical, nonetheless they all have the following listed parts in which the way of construction may differ.

WHAT IS A POWER TRANSFORMER? A power transformer is considered to be a major electrical equipment found in every substation because of its function and since it is the largest, heaviest, and the most expensive device. That is why proper care and protection are done to insure that this device would not be easily damage if faults and overloading will occur. Protective devices like circuit breakers, surge arresters and fuses are usually used to do so.

load losses: Those losses that are incident to the carrying of a specified load. Load losses include I 2 R loss in the current carrying parts (windings, leads, busbars, bushings), eddy losses in conductors due to eddy currents and circulating currents (if any) in parallel windings or in parallel winding strands, and stray lossinduced by leakage flux in the tank, core clamps, or other structural parts. In equation form:  PLL = I 2 R+PEC+PSL where PLL is the load loss (W) I 2 R is the loss due to current and resistance (W) PEC is the eddy current loss (W) PSL is the stray loss (W). See also: no-load (excitation) losses.