In the event of failure of distribution transformer, apart from the loss of capital to the utility, the consumer Suffers due to inconvenience caused by the interruption of power supply. It was installed in a rural area. In rural areas power pilferage, loading of transformer by State Electricity Boards (SEBs) personnel ( without consideration of already existing load on the transformer) and CLP current are the major causes of overloading and to some extent harmonic distortion of current is responsible for failure of transformers. These faults arecorona or partial discharge, thermal heating and arcing. Various investigators have not agreed on life-duration at any given temperature. failures transformer density predicting transformers failure doble statistics published discharge partial frequency detection sensitivity radio check power The area which is vulnerable is the edge of the coil where pancake windings are connected together. [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? 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. 14. 2001. Our product offerings include millions of PowerPoint templates, diagrams, animated 3D characters and more. This leads to aging and decomposition of both liquid and solid insulation material i.e.oil and cellulose which liberate gasses within the transformer. Diagnostic tests will typically show deterioration and the results will provide clues where the failure occurred or where it is about to happen. The specifications of this transformer are as follows: 63 kVA, 11/0.433 kV, DY11, 50Hz, 3-phase, High Voltage winding current 3.3 A, LowVoltage winding current 84 A, Aluminium wound, natural oil cooled, temperature rise 323 K(500C), percentage impedance 4.5, Oil 110 L, weight of oil 93 kg, weight of core and winding 191 kg, total weight 382 kg .It was found by inspection that all three high voltage windings were damaged as shown in Fig. But since its not possible for all the tests to be carried out on transformer on a regular basis a predictive maintenance program for transformer is essential since it provides trending data to help anticipate and plan future maintenance activities, which saves time and money. Failure can be prevented by adequate support of the outer turns. Round-wound transformer designs are preferred as it reduces the voltage stresses, stay cooler, don't create noise and also offers less risk of short circuit with sheet wound secondary. In Shim 2010, the aging of insulating paper and oil is studied by performing accelerated thermal aging test. It can be seen that a temperature of 413 K (1400C) and6 months aging caused the TAN to increase from 0.002 to0.105 mg KOH/g approximately. On inspection its connected load was found to be 19kW. Power supply utility also suffers due to loss of revenue for supply outage period. Other causes of distribution transformer failure modes can be the result of a grounded core or core clamping structures (such as through-bolts) that develop shorts. Our technicians also have extensive experience in substation commissioning, from low voltage distribution right through to high voltage transmission systems. 10C is referred to as the Montsinger Factor and is a rule of thumb describing the Arrhenius theory of electrolytic dissociation. However, the long thermal time constants of a transformer make the relationship between load and transformer temperature highly dynamic. The specifications of this transformer are as follows: 100 kVA, 11/0.433 kV, DY11, 50 Hz, 3-phase, High Voltagewinding current5.25 A, Low Voltage winding current 133.33 A, Aluminium wound, natural oil cooled, temperature rise 323 K (500C), percentage impedance 4.5, quantity of oil 190 L, weight of oil 167 kg, weight of core and winding 269 kg, total weight517 kg. For liquid filled transformers, the traditional insulation system consists of oil and paper. - Electrical Testing and Commissioning Services UAE - These services are rendered by our diligent professional team using optimum quality equipment and methodology. 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. One phase of HV windings, Remaining two phases of LV windings were in healthycondition.Figure 9. well within the range as per specifications, as shown in Fig. E1-22, No. This means that the temperature is dependent not only on the present load, but also on the loading in the previous hours. - Food Supply Protection in an Age of Biocrimes, Terrorism, and Emerging Infections No meat or dairy, no aquariums, no circuses, no hunting or fishing, no fur or SC B5 - Protection and Automation Report to the Canadian National Committee of CIGR, - Report to the Canadian National Committee of CIGR 2009 Simon R. Chano Protection Specialist Hydro Qu bec Trans nergie 800 de Maisonneuve est, 22i me tage, Application of Digital Relay Protection on APUA T&D Network, - Application of Digital Relay Protection on APUA T&D Network Presented by: Li Zhengrong Substation Maintenance & Protection Engineer Andre Matthias Division Manager, Using AMI to Improve the Operation of the Electric Distribution System. After craftsmanship comes the most important factor : material. International Journal of Scientific & Engineering Research, Volume 5, Issue 6, June-2014. Two main reasons for low maintenance are: one, a large number of transformers that are installed in remote rural areas. Results of present study show that insulation degraded due to excessive heat and not due to normal aging. They draw more current than the fundamental current and cause overloading of the distribution transformer. Design also plays an important role in the life of a transformer. The voltage rating of all transformers is 11/0.4kV and the capacity ratings are25kVA, 63kVA, 100kVA and 200kVA respectively. ', Types of Renewable Energy Sources [With Pros & Cons], Electrical and Smart Grid 101: All you need to know. An open or shunted current transformer. the load is doubled by eachfarmer. Insulation aging is a thermo chemical process in which aging progresses as a highly nonlinear function of the absolute temperature. This could be a classic example of overheating ofboth low and high voltage winding. Cooling issue :Some times the cooling fans are out of order or the transformer is suffering a severe oi leakage resulting in the increase of temperature inside. Mohammad R 2008 gives measurement of some parameters for nine oil samples of operating power transformers manufactured by the same company. 2Figure 1 Figure 2. And sometimes it could be due to natural causes like lightning which causes electrical surge in the power lines. Transformer temperature, in turn, is related to loading. According to a latest 'Technical Paper' and transformer failure report published by OMICRON, up to 26% of the major transformer failure is related to tap changer. Cases of illegal hooking of supply lines have been reported in newspapers almost every alternate day.During wedding season, temporary connections areprovided on request in both rural and urban areas. 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. Total Acid Number of the oil specimens of presen t study. Moreover, it requires a large quantity of oil to perform the analysis and requires expertise for interpretation of results. TAN is defined as the acidity of the oil which is milligrams of 0.1 normal KOH needed for neutralizing the acidity of 1g oil. This increase in TAN is due to combined thermal aging of insulating paper, pressboard and oil in actual distribution transformers.The experiments, conducted on vessels, by Yoshida et al1987 & shim 2010 do not represent an actual transformer because actual windings, hot spots, core, poor workmanship etc. Increase in acid value of insulating oil due to thermal aging (Insulating paper) [9]. 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. In India, the failure rate of distribution transformers is very high, around 25% per annum. 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. This resulted into severe overloading and burning of B Phase of LV winding as shown in Figure11. 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. Therefore harmonic currents produced due to nonlinear loads may also be one of the causes of its failure. These might include tap changer failures, bushing failures, tank failures, moisture ingress, and other forms of dielectric fluid contamination. Cold load pickup (CLP) current may also be one of the causes of its failure. Proper and timely maintenance could have saved this transformer. 57.100, IEEE Standard Test Procedure for Thermal Evaluation of Liquid-Immersed Distribution and Power Transformers? 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. This could have been the reason for failure of this particular transformer. In India, most failures of distribution transformers occur even before the life of 5 years due to overloading. Home Electrical World Distribution Transformer Failure : Causes, Analysis and Prevention. You might even have a presentation youd like to share with others. Which unfortunately is overlooked where we try to automate all our manufacturing process. Worlds Best Portable AC Unit which helps to keep the electricity bill down ! Why Use An Electric Screwdriver? 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. 57.100, the minimum expected life of liquid-immersed distribution and power transformers, operating at 303 K (300c) average ambient, is about 20.55 years (180,000hours) [12]. Open coil. 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. If this goes unnoticed it might lead to excessive buzzing and overheating. Sometimes,load shedding is done without any prior intimation to consumers and loads remain switched during supply outage period. Causes of overloading of distribution transformer may be different for different areas i.e. <>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.44 841.68] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> Radial failure can collapse the inner winding unless the winding support structure is strong. Oil samples from 27 distribution transformers which failed within the warranty period are analysed. 3 has been reproduced from[5]. The life of a transformer is normally dependent upon the life of the insulation. It was installed in a rural area.

Thus by having a good and reliable transformer maintenance program catastrophic failures and high cost repairs can be avoided. Prolonged overloading may be caused by use of inadequate size fuses. are all drawing current at the same time. 8 gives the view of one phase of HV winding and clearly shows the burnt condition. Boasting an impressive range of designs, they will support your presentations with inspiring background photos or videos that support your themes, set the right mood, enhance your credibility and inspire your audiences.

PowerPoint PPT presentation, Electrical Commissioning | BCJ Controls | Secondary Protection. 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 dU] 8Lj4V2-uKNRT<3@ulpHKz2)Y?OYNGy%9" RXO`i'*UJ`>"&)Qp[} All transformers were installed in the state of Madhya Pradesh and supplied by different manufacturers. 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. In case of unbalanced loading, voltage is generated on the neutral and will remain floating between neutral and earth. Well convert it to an HTML5 slideshow that includes all the media types youve already added: audio, video, music, pictures, animations and transition effects. [5] The secrets of transformer cooling? Losses in the transformer cause thermal stress in the active part. Cost efficiency since necessary repair works can be properly scheduled. Helmet. In urban areas most of the load is nonlinear which are increasing day by day. Usually when a distribution circuit is restored after an extended outage, the demand is more than pre- outage demand. According to a newspaper report, a temporary connection for 8kW load was requested for, in an urban area in the heart of the city. Safety Gloves. 16 These transformers were of the age 2 to 35 Years approximately and were working properly.He viscosity of transformer oil is varying from 28.09 to 65.0 cSt in the present study of 27 samples as shown in Fig.17. on: Electricity Distri., vol.1, Birmingham, UK, May 1993, pp 1.16/1-1.16/5. <> Discharge Rod. Fig. 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. 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. Fig. Since the neutral is solidly grounded through external link, a circulating current will flow through the loop of delta winding. Thus it's very essential to carryout regular oil filtration of the transformer and leak arrests before it becomes very critical. Fig. And theyre ready for you to use in your PowerPoint presentations the moment you need them. These gasses dissolve in the oil. Thermal aging of transformer insulating material is related with the chemical reactions - pyrolysis, oxidation and hydrolysis, occurring within the transformer. Sometimes the windings telescope, caused by uneven axial forces.The result is typically a tangled mess of winding conductors which eventually arc to ground or each other, and disrupt the force vectors in ways that were not accounted for in the original design. Mechanical failures can be the result of shipping damage, seismic activity, and thru-faults. Usually the harmonics on the third and fifth level indicates interference from the electronics loads. Power theft and deliberate overloading by SEBs also leads to premature failure of distribution transformers in urban areas. 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- 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. [12] IEEE Std. 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. 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. Electrical failures are the result of insulation degradation. The diagnosis results are then verified by dissolved gas analysis. The overheating may be due to prolonged overloading. Fig. It was found that BDV of 31 samples was above 60kV and 18 samples had BDV above 70kV as shown in Fig. The reason for severe destruction of R phase of LV winding may be the high impedance fault along with overloading. However, they do agree, that between 353 K(800C) to 413 K(1400C), the rate of loss of life due to aging of transformer insulation is doubled for every 60C rise in temperature [3]. 22. Conf. This validates the results of the present study. 6, pp 795-800, December 1987. Especially for overloading and high operating temperatures over longer periods of time a rise in TAN should appear [11]. During their life cycle, transformerswill go through three different periods of failure rates, which explains the bathtub shape.