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more number of points for illumination, fan, heater stove, electric iron, television etc., without paying for them. An open or shunted current transformer. Increase in acid value of insulating oil due to thermal aging (Insulating paper) [9]. Furthermore, oil samples of 27 failed distribution transformers of different capacities are taken and Breakdown Voltage (BDV), Total Acid Number (TAN) and Viscosity are measured to find the most appropriate property that can give prior information of failure of distribution transformers and interesting results are reported. rural and urban areas. PowerPoint PPT presentation, Electrical Commissioning | BCJ Controls | Secondary Protection. Transformer (1) and (3) are having identical kVA rating but are supplied by different manufacturers. Hence CLP current is many times greater than pre- outage current which causes heavy overloading of the distribution transformers. CLP problem occurs in rural area due to scheduled power cut in M.P. It is a case of continuous overloading as all three phasesof HV and LV are utterly scorched. This indicates that the temperature of the oil must have reached to above 413 K ((1400C)). Each has different voltage stress applied to different components of the winding (individual strand to-strand, conductor-to-conductor, layer to-layer or disc-to-disc, etc.). In practice, the life of a transformer can be as long as 30 years with appropriate maintenance. Since the operational situations of a transformer keeps changing over its life time so does its expected life time. samples lies between 0.224 and 0.336. Radial tension failure, also known as hoop tension failure, can occur;conversely, radial compression failure can also occur. The remaining two phases of LV windings and paper insulation were also found in severely burnt condition as shown in Fig. 12th Int.Conf. InternaPtiornael Jmournaaltouf SrcientiFfica&iElnugrineeerinogfReDseiasrcht, rVoilbumuet5,iIossnue T6, rJuanen-20s1f4 ormers A Case Study, Dept. Thermal aging of transformer insulating material is related with the chemical reactions - pyrolysis, oxidation and hydrolysis, occurring within the transformer. VFQq_W:#\8 :H5V^?nf!m:Tod8];2IU)#mPAf:pRG'Cq'`7y^-"e Uq0aL[>RUtCVJ!V8hJ1kn g7JQ}t]);SgB*J: x'Q'C+rZ udfKuUt]@t(JF'!(P6euFZ,oT%. Failure can be prevented by adequate support of the outer turns. There are various parameters which can be measured to assess the condition of the oil such as density, flash point, relative permittivity, breakdown voltage, dissipation factor, viscosity, specific resistance, total acid number etc. Also it results in a good overall efficiency since conditions related to transformer losses can be corrected. Oil samples from 27 distribution transformers which failed within the warranty period are analysed. In more interesting fashion it sometime also happens due to snakes, squirrels etc. This resulted into severe overloading and burning of B Phase of LV winding as shown in Figure11. 19 shows the increase in acid value of insulating oil due to thermal aging in the presence of insulating paper only. Therefore, a proper maintenance program should be in place in order to for the aging process to be quantified and tracked so that catastrophic failures can be avoided. Well convert it to an HTML5 slideshow that includes all the media types youve already added: audio, video, music, pictures, animations and transition effects. The consequences can be arc from the energized winding to an adjacent winding or to ground. This means that up to the age of 25 years TAN remained below 0.18 mg KOH/g because transformers were not overloaded and hence not overheated. - Circuit breakers can fail to open due to a burned out trip coil, or to ensure that the proper circuit breakers are tripped at the proper speed to: SURGE%20PROTECTION%20USING%20SUPERCONDUCTORS. BDV was reduced to about 30% of initial value, for aging time of 1500 hours (62.5 days only), which can be seen in Fig. CLP is a phenomenon that takes place when a distribution circuit is reenergized following an extended outage of that circuit. It was installed in a rural area. less than three years. - No job is too large or too small. Unbalance Loads :Due to the presence of the unbalance load in the power system a higher temperature on the one of the phase may occur resulting in local heating. of Electrical Engineering Dr. C. V. Raman University, Guru Ramdas Khalsa Institute ofJabalpur Engineering College, Bilaspur, C.G., India Science and Technology,Jabalpur, M.P., India Jabalpur, M.P., India, Distribution transformer is an imperative link of thedistribution system without which the utility would not be able to supply electricity to consumers. Diagnostic tests will typically show deterioration and the results will provide clues where the failure occurred or where it is about to happen. Core form designs have subsets consisting of numerous winding configurations such as layer windings, helical (or spiral-type)windings, continuous disc, and interleaved disc windings. Call us: (02) 9534 8465. Then you can share it with your target audience as well as PowerShow.coms millions of monthly visitors. This excessive heat is caused by heavy overloading. There is no single measurement which can give a complete picture of the condition of transformer oil. Thus it's very essential to carryout regular oil filtration of the transformer and leak arrests before it becomes very critical. As they say prevention is better than cure, problems can be detected at an early stage before it becomes a hazard. In case of a lower dielectric value transformer filtration should be carried out for the transformer by taking it offline. - ILAC G13:2007 Proficiency Testing Requirements A2LA PT Training 2008 Conclave April 11, 2008 Dan Tholen ILAC G13 Training Introduction to A2LA PT Provider - Title: Con Edison of New York FFR PPE TESTING Author: G. Pilate Last modified by: tillr Created Date: 10/15/2003 2:44:22 PM Document presentation format. The question that then arises is: Can the distribution transformer survive? Figure 10 gives the view of HV winding andclearly shows the burnt condition. ), Dr. C.V. Raman University, Bilaspur (Chhattisgarh) and Jabalpur Engineering College, Jabalpur.of the repairing unit considered, also show that almost 90% of transformers fail due to overheating caused by overloading. Results of DGA also agree with these diagnosis results as ethylene is the principal gas with some amount of ethaneand methane in each case, the cause of which is overheatingof the oil. Up to 26% of major transformer failures are related to the tap changer ! How much do you know about Transformer Maintenance? This additional circulating current will superimpose on the main branch current of the delta winding and will cause additional heat, which may lead to the failure of the HV winding insulation. Oil ages rapidly at high temperature and moisture acts as a catalyst for its aging. 6 gives the view of R phase of HV winding in which b urnout and breakage/puncture of coil canbe seen clearly. <>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.44 841.68] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> It has been reported that 20 working transformers having age up to 13 years had TAN less than 0.1 mg KOH/g oil and 18 transformers having age 14 to 25 years had TAN from 0.1 to 0.18 mg KOH/g oil i.e. They are accelerated by increased levels of temperature. According to studies the best material to use for the core is magnetic silicon steel with thinner thickness. These faults arecorona or partial discharge, thermal heating and arcing. It was installed in an urban area. Various investigators have not agreed on life-duration at any given temperature. This could be a classic example of overheating ofboth low and high voltage winding. They frequently show results observed during an internal inspection or tear-down as some form of insulation burning which appears as discoloration or carbonisation of cellulose. The ambient temperature adds on to the effect of loading. Shell form construction is resistant to winding deformation due to thru-faults.This is because the coil pancakes are arranged in multiple groups to limit force magnitude. An example of a detailed transformer failure report of a 315MVA which failed at Bamnauli Substation, Delhi-India can be found here. As soon as power is restored, all loads simultaneously draw current and overload the transformer. This could have been the reason for failure of this particular transformer. The reason for severe destruction of R phase of LV winding may be the high impedance fault along with overloading. This means that the temperature is dependent not only on the present load, but also on the loading in the previous hours. The normal values of BDV, viscosity and TAN according to Indian standards335 [6] are given in Table II. Those where cellulose is not involved typically show as points of contact on core steel or tank steel and winding or leads where the conductor is bare. 4 0 obj The obvious result of a mechanical failure is the displacement of winding turns or damage of the turns by the forces exerted during the damaging event. Tests for TAN and viscosity can be performed more easily and more frequently to assess the state of oil insulation of distribution transformers. In rural areas if connection of 5 pumps is authorized, after load shedding when supply is restored, 10 pumps are operated by the farmer to finishthe required irrigation i.e. Some of the most common causes of transformer failure are : The following graph describes the relative failure rate of a whole group of similar products like transformers. However, the long thermal time constants of a transformer make the relationship between load and transformer temperature highly dynamic. Here is a short video the showing the devastating consequences when an electrical transformer explodes : Loose connections :Due to long term vibration, connections can loosen in the transformer. Electrical failures are the result of insulation degradation. hP `(rY}?:oYWO~XpU]%:_\ ,MGl[V,*c>@qv{1U%T]cz{D(|6tP)5QO? %Y. &Ve'zzwYizCqAG,r/XDevx{{O &xJ/(@C?M$hv&hL6=Rt3s)[ nT4T2IP-P1.,JOPrPlZr~*Pow_0,i@|zRNm7K>[*r-@ju8_=Z]7\s - SURGE PROTECTION USING SUPERCONDUCTORS. Yoshida et al 1987 gives results of investigation of changes in characteristics of cellulose insulating materials i.e. If so, share your PPT presentation slides online with PowerShow.com. Radial failure can collapse the inner winding unless the winding support structure is strong. nonlinear loads, in offices, industries as well aswindings was found in burnt conditionas shown in FigurIJeSER 2014 http://www.ijser.org. It is important to note that overloads rarely result in transformer failures, but do cause thermal aging of winding insulation. Our technicians also have extensive experience in substation commissioning, from low voltage distribution right through to high voltage transmission systems. (1)Transformer which failed within two years Its life was only one year and eight months. These might include tap changer failures, bushing failures, tank failures, moisture ingress, and other forms of dielectric fluid contamination. The area which is vulnerable is the edge of the coil where pancake windings are connected together. - Voltage and current transformers play a vital role in the power protection scheme. Please feel free to view any of the related presentations to the right. 9, This transformer failed due to unbalanced loading andpoor maintenance. Completed 2008 Electra article will be published shortly - EHV transformer failure, asset classification into consideration when determining overall operational risk to the organization 27 Power factor testing, - Transformer Protection, DGPT2, DMCR or thermal protection activating coil tripping of Fuse switch combination or Circuit breaker IM Switch units wo ILAC G13:2007 Proficiency Testing Requirements. White Topic #1: Review of research projects and identification System of Systems Analysis of Future Combat Systems Sustainment Requirements. Here, a case study of four distribution transformers which failed within warranty period of three years is presented and causes of failure are analyzed. Discharge Rod. In M.P., more than 200,000 distribution transformers are installed [1]. stream Other two phases were in heal thy condition.would have been drawn that cause not only the LVwinding to burn but also punctured the HV winding as shown in Fig. This trend is inagreement with present study of failed transformers in which BDV of all the 27 oil samples lies in the range of 12 to46 kV, as shown in Fig. Deliberate overloading for long durations must not be encouraged. <> 22 months. The B phase of HV winding was also overstressed bythis overloading and got damaged as shown in Figure 10.Oil samples are taken from each transformer for DGA and all results are reported in Table I. on High Voltage Engineering and Applications (ICHVE), New Orleans, 2010, pp 393-396. 2 0 obj The acidity measurements show that the most certain and clear change in the oil characteristics, due to thermal aging, takes place in its acidity. Our new CrystalGraphics Chart and Diagram Slides for PowerPoint is a collection of over 1000 impressively designed data-driven chart and editable diagram s guaranteed to impress any audience. [10] Myeong- Seop. The increased current by each nonlinear load due to harmonics is one of the major causes of overloading of distribution transformer in the urban areas. 14. Why preventive maintenance for transformers? Which unfortunately is overlooked where we try to automate all our manufacturing process. The diagnosis results are then verified by dissolved gas analysis. Shim 2010 simulated the distribution transformer by sealedvessels containing all materials in the same ratio as in transformer and reported that TAN for mineral oil increases from 0.01 to 0.26mg KOH/g oil at a temperature of413 K (140) for aging time of 1500 hours as shown in Fig.21. 18. And, best of all, it is completely free and easy to use. During their life cycle, transformerswill go through three different periods of failure rates, which explains the bathtub shape. They draw more current than the fundamental current and cause overloading of the distribution transformer. (Lets Find Out), 2022 Engineering World. insulating paper and pressboard, through accelerated tests using models of oil- impregnated insulating systems but these model coils do not represent the actual transformer. The overheating may be due to prolonged overloading. This current is combined with the other continuously operating loads and causes the overloading of distribution transformer in the urban areas. TAN of the 21 oil. Why Use An Electric Screwdriver? Transformer Failureappear in different ways, depending on the type of construction. It is found that transformers fail mainly due to overheating caused by overloading. Agenda. 10C is referred to as the Montsinger Factor and is a rule of thumb describing the Arrhenius theory of electrolytic dissociation. - Electrical Testing and Commissioning Services UAE - These services are rendered by our diligent professional team using optimum quality equipment and methodology. TAN does not change much over time, but at elevated temperature caused by increased load TAN increases and gives information about the accelerated thermal aging [7]. B phase of the system. Bymeans of dissolved gas analysis it is possible to distinguishbetween the faults. Moreover change in low voltage excitation current, a change in impedance, and sometimes, the presence of partial discharge (PD) during an induce voltage test can also give valuable indications about a mechanical failure in the transformer. These nonlinear loads are mostly used in urban areas. Antonioli, CESI, Milano; Study of the life consumption ofDistribution transformers and assessment of end-of-life criteria? Thus by having a good and reliable transformer maintenance program catastrophic failures and high cost repairs can be avoided. dU] 8Lj4V2-uKNRT<3@ulpHKz2)Y?OYNGy%9" RXO`i'*UJ`>"&)Qp[} Two main reasons for low maintenance are: one, a large number of transformers that are installed in remote rural areas. This high value of viscosity will result in inefficient cooling of transformer and the temperature of oil may exceed permissible limit.Hence it is a deciding factor for thermal aging of the oil. - Melted arc chutes will not interrupt fault currents. Hood, August 15-18, 2002. Jon L. Giesecke, InfraMation 2007 Proceedings, ITC 121A, 2007-05-24[6] Indian Standards IS: 335-1983 New Insulating oils for transformers and switchgear. the load is doubled by eachfarmer. Cost efficiency since necessary repair works can be properly scheduled. 5 gives the rear view of HV windings. ', Types of Renewable Energy Sources [With Pros & Cons], Electrical and Smart Grid 101: All you need to know. [1]Number of existing distribution transformer available- www.mperc.nic.in/290811 performance -Standards-2010-11.pdf [Accessed:Dec.23, 2011][2] IEEE Guide for loading Mineral Oil ImmersedTransformers, IEEE C57.91 1995[3] D.P.Gupta, Loading and life of transformers? Out of these parameters dielectric strength, viscosity and total acid number of the oil were measured and analyzed According to manufacturers in India, same oil is used in power as well as distribution transformers; therefore properties of oil from both the transformers are presumed to be same. e; ^d=*_eB"q >k40-z\M+Pi}C &T t_ez9{lD;qy8a/Z>S]r\Sr 2001. One phase of LV windings was found in an extremely smashed condition. A dielectric breakdown can also be the result of mechanical forces tearing the insulation. Experimental analysis was performed on the oil samples taken from these distribution transformers. The voltage rating of all transformers is 11/0.4kV and the capacity ratings are25kVA, 63kVA, 100kVA and 200kVA respectively. They'll give your presentations a professional, memorable appearance - the kind of sophisticated look that today's audiences expect. Transmission and Distribution Technology Research Stem Meeting. Due to constantly increasing population and hence load demand, the number of distribution transformers is now continuously increasing. One phase of LVFigure 10Figure 11, Overloading/unbalanced loading is the major cause of failure of this transformer. Although the number of distribution transformers is very large as compared to power transformers but the fault diagnosis of distribution transformers has not been given proper attention as they are not as expensive as power transformers. endobj 8 gives the view of one phase of HV winding and clearly shows the burnt condition. | PowerPoint PPT presentation | free to view, The Solar Protection Relay by BCJ Controls | Comap IntelliPro, - We offers installation, testing, commissioning, also we have a different protection relays. Preventive maintenance is the key to avoid such kinds of disasters. In Shim 2010, the aging of insulating paper and oil is studied by performing accelerated thermal aging test. The result of a electrical failure can be a turn to turn failure. It has been observed that line operators use morethan the recommended capacity fuse wires either due to lack of knowledge or just to avoid frequently replacing the fuse especially in remote rural areas. It was installed in a rural area. 3 0 obj Government of Madhya Pradesh has given one point legal connections per family free of cost to all economically weak families in both rural and urban areas. It wasinstalled in a rural area. In India, most failures of distribution transformers occur even before the life of 5 years due to overloading. In India, the failure rate of distribution transformers is very high, around 25% per annum. Whatever your area of interest, here youll be able to find and view presentations youll love and possibly download. 2Figure 1 Figure 2. Now let's try to another three important factors which could also lead to the failure of the distribution transformers : Probably one of the most important factor in transformer life is the level of the craftsmanship, the quality of manufacturing process and controls placed to keep a check on the process. Fig. 7. - Hot Spot Detection. PowerShow.com is a leading presentation sharing website. The specifications of this transformer are as follows: 200 kVA, 11/0.433 kV, DY11, 50 Hz, 3-phase, High Voltage winding current 10.5A, Low Voltage winding current 266.67 A, Aluminium wound, natural oil cooled, temperature rise 323 K (500C), percentage impedance 4.5, quantity of oil 400 L, weight of oil 340 kg, weight of core and winding 455 kg, total weight 1142 kg It was found by inspection that all three HV windings were severely damaged. The specifications of this transformer are as follows: 100 kVA, 11/0.433 kV, DY11, 50 Hz, 3-phase, High Voltagewinding current 5.25 A, Low Voltage winding current133.33 A, Aluminum wound, natural oil cooled, temperature rise 318K(450C), percentage impedance 4.5, quantity of oil 190 L, weight of oil 161.5 kg, weight of core and winding 280 kg, total weight 598 kg It was found by inspection that all three high voltage (HV) windings were damaged as shown in Fig.1. The main point of concern in ageing and the life expectancy of transformers is the condition of the insulation system, which is typically based on organic products.The organic products in a transformer degrade over time and finally they lose the capability to withstand the stresses a transformer might see in daily life. x=Yo7V}lYNdeH+14>e*6Rv4Huy~{q~[|X]\//nO3!>}"fOZmO|/ LMVVl!:|yV\b~-f7khq.Ed^n~65;|BJQRT:8;ukrQr4RVA"4Eaq1vM^cE-`[tIE,snaFjxy, [d jy.HV2lYH~CdC[1k- It has millions of presentations already uploaded and available with 1,000s more being uploaded by its users every day. (3) Transformer which failed within two and half yearsIts life was only two years and four months and was installed in a rural area. It is also found that the two transformers which had same rating but were supplied by different manufacturers and installed in rural area, failed due to lack of knowledge/carelessness or poor maintenance and not, due to manufacturing defects for which manufacturersare blamed every timeAccording to IEEE Std. And sometimes it could be due to natural causes like lightning which causes electrical surge in the power lines. By the measurement of TAN and viscosity it is possible to get a clear overview of the oil condition of the transformer and it can be saved from failure. 20 shows the increase in acid value of insulating oil due to thermal aging of model coil in the presence of pressboard only. Having a good transformer maintenance program in place will result in the following benefits: A good transformer maintenance program should have regular electrical testing of the transformer for different parameters like turns ratio, excitation current, polarization index, insulation resistance, short circuit impedance etc. This highly appreciable endeavor of the government is misused by almost 90 percent public, by drawing extra power than legally permitted, to run their appliances e.g. In addition to the above test oil sample should be taken a series of test should be conducted on a regular basis in order to determine the dielectric strength of the insulating oil inside the transformer. This validates the results of the present study. Axial failures can occur in both compression and tension. endobj 3 has been reproduced from[5]. The post-outage load in urban areasmay be significantly greater than pre-outage load when several, normally diverse, cyclic loads e.g. The value of 11.36586 cal/cm2 is based on a single-phase arc in open-air. Form fit tank and core prevent movement of the core and winding groups. are all drawing current at the same time. TRANSFORMERS, Second Ed., Bharat Heavy Electricals Limited Bhopal (M P), Tata McGraw-Hill Publishing Company Limited, 2003. Overloading increases the current and hence increases these losses and consequently temperature of the windings and oil increases and decreases the life of the transformer. Thats why its highly recommended to perform a SFRA (Sweep Frequency Response Test) test on site to observe any change in the SFRA test result in comparison to the factory results. Due to their low cost, distributiontransformers are removed after failure and replaced withof distribution transformer becomes essential. Since this transformer was installed in rural area this must have been the reason for failure. This can be caused by thermal degradation over the life of the transformer, by thermal degradation due to excessive or frequent fault current, or by dielectric breakdown due to high voltage stress. In present investigations, it has been found that TAN of all oil samples varies from 0.224 to 1.12 mgKOH/g as shown in Fig. The winding I2R losses, the core losses and the stray losses in the tank and metal support structures are the prime sources of heat that cause the oil and winding temperature to rise [4]. We can cater for smaller commercial generation systems (PV or diesel in parallel). The distribution of these gases can be related to the type of fault which caused the thermal stress. Transformer temperature, in turn, is related to loading. Fig. Theft of power by hooking the power line has been a regular phenomenon in both rural and urban areas. Fig. Excessive Harmonics :If a higher temperature is observed at the neutral termination then it's an indication of the presence of harmonics. Our product offerings include millions of PowerPoint templates, diagrams, animated 3D characters and more. Fig. - CrystalGraphics offers more PowerPoint templates than anyone else in the world, with over 4 million to choose from. Though they are some of the most reliable component of the electrical grid they are also prone to failure due to many factors both internal or external. Statistical data indicates that over 25% failures of distribution transformers are within the warranty period of three years only and this causes an immense capital loss. All three low voltage (LV) windings were also foundburnt and paper insulation was damaged as shown in Fig. residences is now increasing day by day due to its low costand high efficiency. Cold load pickup (CLP) current may also be one of the causes of its failure. After craftsmanship comes the most important factor : material. Often a number of new connections are added to the existing transformer without calculating the load which it can supply and line operators connect these new loads to the most reachable conductor i.e. 6, pp 795-800, December 1987. specimens taken from 43 working transformers of differenIJtSER 2014 http://www.ijser.org. You might even have a presentation youd like to share with others. Its life was only one year and eight months. Sealed aging test vessels containing copper, laminated core, Kraft paper and insulating oil were aged at 413 K (1400C) for 500, 1000 and 1500 hours respectively. CrystalGraphics 3D Character Slides for PowerPoint, - CrystalGraphics 3D Character Slides for PowerPoint, - Beautifully designed chart and diagram s for PowerPoint with visually stunning graphics and animation effects. Hence this is the deciding factor for the life of distribution transformers as it is an irreversible phenomenon [8].