Two most of import equipment found on the power distribution grid are transformers and circuit surfs. Their dependability and public presentation is important to power distribution. Any dislocation of such equipment entails loss of gross for both providers every bit good as consumers. Therefore it is of topmost importance to maintain them operational throughout their being. Care is the lone manner to maintain them suit for responsibility. Minor debasement in transformers and circuit surfs should non be neglected because Oklahoman or later it becomes the weak point in the equipment. Detecting these failings in progress aid in many ways to minimise care cost, prevent unanticipated outages and supply a smooth power distribution on the web. Continuous monitoring of these equipment demand to be carried out for good in order to observe any debasement and failures utilizing proper instruments based on makers informations. Using the information collected, the status appraisal of each device can be build up.
Condition appraisal history helps to schedule the right type of care in clip which will guaranty the life-time of equipment. It besides helps makers and developers to convey betterments to their merchandises which at the terminal will be good for terminal users. It can besides be used by the planning squad to measure the burden capablenesss as clip base on ballss.
Condition appraisal of equipment should therefore form portion along with the production line.It should be scientifically carried out to acquire the upper limit of the equipment.
THE POWER TRANSFORMER
hypertext transfer protocol: //www.o-digital.com/uploads/2179/2225-1/S11_M_30~1600kVA_Oil_Immersed_Power_Transformer_913.jpgFIG 1.
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A transformer is an equipment for transforming electrical energy in an ac circuit from one electromotive force or current into electrical energy at a higher or lower electromotive force or current.
A constant-voltage transformer consists basically of three parts:
1. Primary spiral playing as the input from bring forthing works,
2. A magnetic nucleus bring forthing an alternating magnetic field,
3. The secondary spiral connected to the burden.
The high-voltage weaving consists of many bends of insulated Cu wire compared to the low-tension weaving composed of lesser bends of thick Cu wire transporting high current at a low applied potency.
Different types of transformers that are used in the power distribution grid for both industrial and domestic utilizations. Power Transformers, Distribution Transformers of measure up and step down types are widely used. Transformers play an of import portion in the power distribution web and its failure leads to many jobs both economically and socially for illustration in transit and infirmaries. Our premier aim is to maintain the average clip between failures of these equipment every bit low as possible or ideally no down clip.
Recently there has been surveies in transformer life rating and monitoring because there are big figure of the transformers in the universe acquiring old, that is approaching end-of-life and the demand additions for better methods to see whether the transformers are still fit for usage or demand to be upgraded or replaced. Transformer status appraisal every bit good as on-site fix solution as agencies to increase both the dependability and handiness of transformers has been developed. The advanced diagnosing of the transformer status is used to place defects. Failure of such of import equipment implies loss of gross for industries which have to cut down their production by trusting on in house generators and many incommodiousnesss for domestic contraptions.
Table 1.0 shows causes of transformers failure due to both external and internal factors.
CAUSES OF FAILURES OF POWER TRANSFORMERS.
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EXTERNAL/A Natural Causes – Weather Related
NO ROUTINE CHECK
Of all the factors listed, it is understood that some of them are beyond our control and small can be done to minimise their effects. These are solar eruption, heavy rain and humidness and lightning. Rush defenders, switch surfs and arrestors are used to salvage transformer from entire loss in certain instances. As for climatic effects, high quality stuffs are employed for transformer shells which provide both protections against corrosion and at the same clip acts as a good heat dispersing stuff.
AA direct lightning strikeA on power lines causes highly high electromotive force pulsations at the work stoppage point, which travel from the point of work stoppage to TRANSFORMER.http: //electrical-engineering-portal.com/wp-content/uploads/effect-lightning-strike-electrical-lines.jpg
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Condition appraisal of a power transformer is based on regular everyday cheques of basic things with the transformers.Examination of the cellulose paper insularity, executing burden trials, proving oil for taints, look intoing the twist oppositions, electric resistance and the stage angle. Appropriate trials cogwheels are readily available for technicians to transport out the set of trials.
Oil CONDITION TEST.
( beginning ) www.transformerworld.co.uk/oxygen.htm.
Oxidation of oil.
Oxygen has a strong affinity for negatrons. Oxidation of oil arises in a chemical reaction of oil with O to bring forth an oxide.A Oil and paper degrade due to oxidization. With the ripening of oils, there is a lessening in the sum of antioxidants present and the formation of acids and finally sludge. If the oil is non renewed, the contaminations attack the cellulose in the insulating stuff and the acerb react with the Cu spirals. Once the insularity is destroyed, the transformer is of no usage as the twists are short circuited.
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Transformer Oil Testing MachineTransformer Oil Testing Machine
Transformer Oil Testing Machine checklists
1. Specific Resistance ( Resistivity ) .
2. Dielectric Dissipation Factor ( Tan Delta ) .
3. ( Acidity ) .
4. Sediment ( Sludge ) .
5. Flash Point.
6. Water Contents ( PPM ) .
7. Inter facial Tension.
8. Dielectric Strength ( BDV ) .A
9. Dissolved Gas Analysis.A
12. Kinematic Viscosity.
13. PNA Analysis ( Paraffinic, Naphthanic & A ; Aromatic content ) A .
14. Pour Point.
15. Caustic Sulphur.
16. Oxidation Stability.A
17. Aging Characteristic.
18. Presence of oxidization Inhibitor.
Oxidation of Cellulose ( present in insulating stuff ) .
Cellulose oxidizes because it contains O within its molecular construction. During oxidization procedure generates H2O, C dioxide, which is speed up by high temperature and addition in oil sourness.
Megger Delta-4310 Power Factor Test Set
Megger DELTA4000 Series 12 kV Insulation Diagnostic System
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Transformer Winding opposition examiner.
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Weaving opposition measuring in a transformer is really of import for the undermentioned intents: –
1. Calculations of power loss in music director.
2. Weaving temperature computation at the terminal of a temperature trial rhythm.
3. to measure how much its value has deviated from the original valer.
Transformer are tested above rated electromotive force to guarantee that there is no inordinate escape
between the twists ( low electromotive force twists to high electromotive force twists ) and to land.
Indian institute of engineering Tamil Nadus
Prof. Krishna Vasudevan, Prof. G. Sridhara Rao, Prof. P. Sasidhara Rao
Performing burden trial allows us to cipher the entire loss taking topographic point in the twists of the transformer at different current and electromotive force values.
Load trial is used chiefly
1. to find the current burden and the temperature rise.
2. to find the efficiency of the transformer.
Rated current burden is calculated by providing the transformer continuously with current and entering the temperature rise. The losingss that are generated inside the transformer
on burden appear as heat.
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Breathing Procedure of Transformer:
Breathing is the procedure where the transformer takes in and out the air from its casing due to thermic contraction & A ; enlargement of the oil present indoors. When the transformer is runing the oil temperature inside the transformer may lift or falls depending upon the tonss the twists are transporting. We say that the transformer is take a breathing. The air motion in and out contains r dust atoms and humidness that alters the dielectric belongingss of the oil. For proper operation of transformer the dielectric strength of the oil should stay every bit far as possible to the same value when manufactured. Hence, the air come ining the transformer demand to be freed from any dust and H2O vapor.
Silica Gel BreatherA is widely used in the fabrication of transformer because of their efficiency in the controlling of the degree the wet, come ining in the Transformer. A Silica Gel Breather is made from the high quality Blue Silica Gel crystal. The Silica Gel, which is filled in the breathing place, is deep bluish crystals at start and has considerable soaking up power for wet. When Silica Gel absorbs wet its colour alterations depending upon the impregnation degree with H2O.
Color as follows.
Deep Blue Silica Gel wholly dry.
Light Blue Silica Gel partially humid. ( Captive H2O for approximately 15 % of its weight ) .
Pink Silica Gel saturated with wet. ( Captive H2O for about 30 – 40 % of its weight ) .
Dehydrator unit attached to transformerhttp: //www.reinhausen.com/en/Portaldata/1/Resources/tc/news/2005-11-02/scaled/2_m.jpg hypertext transfer protocol: //t2.gstatic.com/images? q=tbn: ANd9GcTkNMNjWS9bDt1wV31idABkU9g8kHzzEHFPgxBKskBP-JNrXRMsNg
Having gone through the different causes of failures due climatic and in-service conditions, we can widen the life of the transformers by executing scheduled everyday trial and carry out the needed overhauling ( serving ) .A care matrix can be set up which will be executed by both the indoor and out-of-door care division.All proving cogwheels shall be supplied to the nomadic squad and with the concerned checklists including consequences records.
This matrix can be used on a sporadically.This will enable, through the cheque list, to find the current provinces of the transformers both part wise every bit good as at national degree. Unnecessary outage will non be encountered, therefore running a healthy power distribution grid. By constructing statistics we can foretell and calculate, when certain transformers need to be decidedly replaced, therefore holding plentifulness of clip for budgeting and telling of new 1s.