Units that must be grounded on one side of the primary are usually provided with only primary connection bushing. Progress report on failures of high voltage bushings with draw leads by jim mcbride and larry coffeen, jmx services neetrac 7262010 7262010 ieee pes july 26, 2010 7 prestrike of the 345 kv ocb contacts on energizing 345 kv transformer from high side the top trace is the magnitude vs. Bushing current transformersbushing current transformers. Understanding the breakdown mechanism of bushings and. This particular 3d transformer is a stepup transformer more windings on the secondary than on the primary. Transformer bushings transformer monitoring bushinggard. Bushings are very important and costly accessories of a transformer. The bushing of the power transformer is a type of porcelain or ebonite post insulator put on the top or side of the transformer tank through which connections are. The solid active part of the oilfree transformer bushing is made of resinimpregnated paper. A basic transformer consists of two coils that are electrically separate and inductive, but are magnetically linked through a path of reluctance. Progress report on failures of high voltage bushings with.
Bushing and explosion vent fitting of distribution transformers. Depending on the extent of the damage caused, the disruption could last for weeks. Operating damages of bushings in power transformers. Safety is demonstrated if no parts are projected outside a circular safety area of 3 m radius around the bushing, and if no explosive events occur in the air side, i. Internally mounted oiltype bushing current transformer meramec. Condition assessment of hv bushings with solid insulation.
The internally mounted oiltype bct is designed to be mounted onto a high voltage bushing shank along the ground collar, inside the tank of a power transformer, power circuit breaker or voltage regulator, that uses oil as the insulating medium. An optimization procedure for the effective cooling of a drytype transformer using cfd was used by 11 to minimize the hotspot temperature of the windings, by 12 to determine a bushings. Jan 07, 2015 bushing and explosion vent fitting of distribution transformers. Heat analysis of the power transformer bushings using the. With the benefit of decades of bushing testing and analysis, doble provides tools, techniques, and services to identify signs of incipient bushing failure. The test is made in line with iec standards or, on request, according to relevant ieee standards. Ac withstand and partial discharge prior to leaving.
Monitors bushing monitoring transformer monitoring. Typical bushing failure modes include moisture ingress, electrical flashover, lightning strike, shortcircuited capacitancegraded layers, bushing misapplication. Transformer basicsworking principle,construction,types. Transformer secondary bushing overheating electric power. The wall sheet of bushing insulator can withstand the ac power frequency voltage about 78. Transformer bushing failures are often credited as one of the top causes of transformer failures so the condition of the bushings is of high interest to transformer asset owners. Bushing testing solutions doble engineering company. Obct internally mounted oiltype bushing current transformer. A bushing can be made of resin, thermoplastic or ceramic. Transformer bushing standards in north america the three main bushing standards that are used are can csa c88. Continuous monitoring of operational and performance data of your transformers allows for better utilization and longer life. Eaton s bushinggard predictive diagnostic solution uses predictive diagnostics to help users prevent malfunctions or breakdowns in large power transformer bushing equipment. The main insulation of hv transformer bushings constructed using rbp.
Parc did not have the exact replacement, but was able to fabricate adaptor flanges for the secondary bushings within a week. During the impregnation of the transformer it is po ssible to reach the max temperature of 110c in oil and 120c in air for. With more than 250 000 bushings in service around the world, and a yearly production of 10 000 units, trench is a leading player in the energy market. The selfoperating systems and remote monitoring services provide realtime detection and allow users to work towards solving problems instead of finding them. The main principle of operation of a transformer is mutual inductance between two circuits which is linked by a common magnetic flux. Abb low voltage bushings terminate the transformers internal low voltage leads at the tank wall and provide a standard threaded stud for connections to the external low voltage circuit. Mar 11, 2010 bushings used to insulate the transformer winding connections from the metallic enclosure. Transformer bushing cts should be tested using the current ratio test method before the. Before delivery, each bushing is subject to an electrical routine test.
With the measurement on the hv bushing tap, not only failure of the bushings dielectric but also of the transformer insulation system can be. Testing during the manufacture and on its completion the bushing is subjected to a number of routine tests, in compliance with iec 607. Hvdc transformer bushing, type ggf installation and. Power transformer reliability modelling technische universiteit. Failing of a bushing can lead to catastrophic failures and can be going along with environmental disasters or fatal accidents of personal. A bushing failure may be catastrophic, which is why doble offers a complete portfolio of products and services to help you track bushing health, from insulation analysis through teardowns. In axial direction, the ggf bushings can be loaded with 3. In this case, the bushing insulator can withstand the maximum electric field strength at contact.
Electrical routine testing of high voltage bushings. Our ekto transformer oil bushing is a solution that was specifically developed for use in the oil environment. Transformer testing equipment transformer bushings. Pdf analysis of the root causes of transformer bushing. The product is designed to come into contact with both transformer oil and cable connection box oil. Series multiple switches offer easy reconnect of transformer windings from series to parallel with a simple turn of the switch on a deenergized. The installation of the current transformer reduces the linetoground strike distance of the apparatus on which it is mounted, a ground shield should be used. The dielectric strength of materials is shown in tab. Transformer bushing provides a very effective insulation be. The reason we normally keep bil of bushings one step higher than that of windings is that we want more safety margin in bushings as any failure in condenser bushings can lead to a fire unlike a winding failure. The enticing range offered by us is widely acclaimed for its dimensional accuracy, low power loss, low noise, durability and efficiency. Oilfilled bushings are usually furnished with a magnetic oil gauge mounted on.
Bushing current transformersbushing current transformers 600v. Pdf analysis of the root causes of transformer bushing failures. A bushing or rubber bushing is a type of vibration isolator. Buchhloz relay, oltc buchhloz, differential relay, and ref relay etc. Bushing searches alamo, tn, usa the following searches apply only to products manufactured at our alamo, tn, usa facility. What is the purpose of using bushings for a transformer. Transformer cant stepup or stepdown the level of dc voltage or dc current.
The general constructional details, are shown in fig. Along with transformer parts surge arresters, isolator, current transformer and many other equipments of substation got damaged. The bushing insulator was designed to be a wall thickness of main body insulator about 4 mm. High current application up to 52 kv, 37000 a transformer to sf6 connection up to 550kv. We manufacture high current bushings of 24kv, 36kv with current rating 4000a16000a. Transformer bushing telk manufactures hermetically sealed, oil impregnated paper condenser bushings 52kv 420 kv voltage class and rated current up to 3150a with standard dimensionscustomer requirements. The new use of the svm method applied mainly in hv motor. The design shows the windings mounted on the same limb of the transformer core, but it is also possible to have low voltage windings wrapped around the core limb and. Beyond this point your transformer may not reliably withstand the next surge load or short circuit. Transformer bushings high voltage insulation and parts. Standards also now recognise this and new iec on bushings calls for 10 % higher ac test voltage than normal ac test voltage for that voltage class of windings. Transformer components type a bushings instructions for.
Abstract deregulation of electric utility industry has forced the industry to operate as a for profit enterprise in a competitive field with no geographical barriers. An unexpected transformer bushing or insulation failure can disrupt an industrial process, shut down a commercial site, cripple a power plant or cause areawide power outages. Features and benefits solid reduced risk for fire, any mounting angle possible, oil leakage from the bushing eliminated, no monitoring of pressure and oil level. There is a chapter on maintenance and a guide for replacing bushings. Transformer operates when both circuits take effect of mutual induction. The bushing sensor requires minimum resources, accounts for. Damage of 220 kv bushing in 160 mva transformer during operation of 160 mva power transformer 220 kv bushing in l2 phase exploded. Bushings are usually associated with voltages above 100 volts. A transformer bushing is an insulating structure that facilitates the passage of an energized, currentcarrying conductor through the grounded tank of the transformer.
Follow instructions in the transformer manual carefully. A common application is in vehicle suspension systems, where a bushing made of rubber or, more often, synthetic rubber or polyurethane separates the faces of two metal objects while allowing a certain amount of movement. Before applying vacuum to a transformer, be certain there is sufficient slack in the external line connections to the bushing to allow for bushing movement caused by flexing of the transformer cover andor walls. An analysis of the root causes of transformer bushing failures following five incidents occurred at jaalan bani bu jbb ali grid station on 2011, has been conducted by feilat et al. A new approach to transformer bushing monitoring by. Porcelain bushings lv series a triedandtested mediumvoltage bushing for distribution transformers. High voltage bushing wells pdf 600a epoxy bushings pdf distribution transformer lv bushings. The test is made at room temperature, and for transformer bushings with the lower end submerged in oil. The gsa bushing is designed and tested according to iec 607 and ieee c57.
This 3d model shows a very basic single phase shell type transformer. It provides an interface between two parts, damping the energy transmitted through the bushing. A tightness test is carried out on the assembled bushing after the final drying and. Ris bushings are characterized by a very low dielectric loss factor tan. The bushing is designed for the following cantilever load applied to the midpoint of the top end terminal perpendicularly to the bushing axis. The book covers the different technologies used in bushing construction and will examine the techniques used in the selection of bushings for power transformers.
A new approach to transformer bushing monitoring by thomas. Providing the missing piece in your condition based. Specification substation power transformer horizon power. High voltage bushings from hsp hochspannungsgerate gmbh. The active part of the bushing consists of an oil impregnated paper oip core manufactured from superior grade kraft insulating paper with condenser graded layers for field control wound under tension on central tube conductor. The shield purpose is to prevent a bushing flashover from penetrating the.
Removable stud bushing well provisions for easy removal of broken parts from both the bushing well and insert. To demonstrate this, a 420 kv normal production bushing was subject to an internal arc test with a short circuit current of 63 ka applied for 0. Buildings, wall up to 245 kv, 5000 a bushings according standard iec. The enticing range offered by us is widely acclaimed for its dimensional accuracy, low power loss, low noise, durability and. Pdf a new method for online monitoring of bushings and partial. Can anyone explain what is the difference between a 2 bushing, single phase transformer and a single bushing, single phase transformer. The ground shields are fabricated of aluminum and fit closely over the top of the current transformer. Bushings according to customers special specification at trench quality is a way of life. Transformer only stepup or stepdown the level of ac voltage or ac current. Our internally mounted oiltype bushing current transformer is designed to be mounted onto a high voltage bushing shank along the ground collar inside the tank of a power transformer, power circuit breaker, or voltage regulator that uses oil as the insulating medium.
The user configurable c50 series transformer monitor provides accurate control for cooling and voltage control, bushing monitoring, and tap wear as well as incorporating inputs from dga devices. The bushing can withstand 250 nm torque on the outer terminal. Early detection of transformer abnormally may allow for a shorter issue resolution cycle and avoidance of. Product range quality bushings for power transformers up to 550 kv, 3150a. The csa standard is in large part an adoption of the ieee standard with some specific canadian requirements e. Rootcause analysis of transformer failure scenario at.
A wide variety of power transformer bushing options are available to you, such as power, high frequency, and electronic. Failure to relieve this stress at the bushing connection may result in damage to the bushing seals and loss of oil. According to a transformer reliability study published in 2, 70% of all transformer fires are cause by bushing failures. The user configurable c50 series transformer monitor provides accurate control for cooling and voltage control, bushing monitoring, and tap wear as well as incorporating inputs from dga devices continuous monitoring of operational and performance data of your transformers allows for better utilization and longer life. In majority of the transformers, hv and lv line terminals are taken out from tank through bushings. Bushings, fuses, fan and pump motors, lightning arrestors, and. Abb low voltage bushings terminate the transformer s internal low voltage leads at the tank wall and provide a standard threaded stud for connections to the external low voltage circuit.
Bushings, cooler banks, conservator and maximum dimensions. Throughout the manual, various types of safety risks are indicated. The paper wrapping and spacers withstand this movement when your transformer is new. The bushing mounting angle can be from 0 to 75 from vertical. Design of 33 kv transformer bushing insulator from nr and. Ieee defines your transformers end of life when there is a 75% loss in paper tensile strength. Abb has introduced many online utilities to facilitate your search for transformer bushings. Transformer bushings connect the network cables to the primary and. Transformer secondary bushing overheating gianoli electrical 26 feb 08 10.
In electric power, a bushing is an insulated device that allows an electrical conductor to pass safely through a grounded conducting barrier such as the case of a transformer or circuit breaker. Transformer monitoring system providing the missing piece in your condition based monitoring platform product summary modular design. Parc was able to deliver a new unused abb replacement transformer bushing in less than 48 hours. Dew 1102235b bushing well 35 200 150 50 50 43 10 1202635b2 bushing 35 600 150 50 50 43 10 1203935b2 bushing 35 900 150. Transformer bushing transformer bushing manufactures.
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