online hv bushing monitoring

EE 476/576

High Voltage Engineering*

On Line HV Bushing Monitoring Instructor: Dr. K. M. BurkeEnergy Systems InstituteDepartment of Electrical EngineeringUniversity at BuffaloAljuboori Ahmed Email:[email protected] Ahmed

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Aljuboori Ahmed E576 High Voltage Engineering

Define Electrical BushingBe familiar with the reasons for transformer failureBe Familiar with Online Bushing MonitoringIdentify the future failing bushing.Detect the condition of electrical bushing.Benefits of online monitoring

Objectives*

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The conductive materials can be classified into three groups:Bus barIsolator Bus barElectrical Bushing

Introduction*

Figure 1: Bushings on 380 kV transformerFrom Wikipedia, the free encyclopedia [1]Aljuboori Ahmed

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Electrical Bushingconductive material with insulation and it is passes through any earthed material[1].

Figure 2: Electrical Bushinghttp://www.myfactoryrep.com/infosheets/eci/Electrical_Bushings.aspx Aljuboori Ahmed*

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Capacitor of Electrical Bushing C1 Capacitance is the capacitance between the center conductor and the tap. As shown in figure 3.[2]C2 Capacitance is the capacitance from tap to ground.

Figure 3: Capacitor of Electrical Bushing[]Aljuboori Ahmed*

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Electrical Bushing FailureAljuboori Ahmed*The voltage can be attracted towards earth point. When the electric field becomes of sufficient strength, this can generator a leakage path. This lead to the failure of electrical bushing[3].

Figure 3: Electrical Bushing Failure[3]

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The Reason of Bushing FailureAljuboori Ahmed*About 90 percent of bushing failure are caused by moisture failure entering the bushing through leaky gaskets or other openings[4]. Improper maintenance for electrical bushing was a major cause of transformer failure.

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The Reason of Bushing FailureAljuboori Ahmed*Also, overloading can be caused the failure.Line surge such as voltage spikes and line faults.Lightning

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Power Transformer AgingAljuboori Ahmed*It is aging of insulation system which reduces both the mechanical and dielectric-withstand strength of the transformer . Figure 4 displays the distribution of transformer failures by age. The average age at failure was 18 years[5].

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Power Transformer AgingAljuboori Ahmed*

Figure 4: Distribution of losses by Age of Transformer[5]

http://www.bplglobal.net/eng/knowledge-center/download.aspx?id=191

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The increasing number of failures in the power transformer, causing Increase the cost of maintenanceReduce transformer life spanIncrease outage timeNew transformer might cost millions of dollarsIt might take time to fix the fault

Problem Description *

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There are many reasons for transformer failure[6]

Problem Description *

Figure 4: Electrical Bushing Failure[6]Aljuboori Ahmed

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How to know the condition of electrical bushing of transformer to detect impending failures in a timely manner.

Figure 5: Transformer Firehttp://www.nttworldwide.com/xfmrfail2.htmWhat is the Solution? *

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Faults of HV Bushing for transformer can be detected by using different technology.One method is to take a sample of oil transformer and sent it to lab. The negative of this method that a fault may develop over shorter time. Inappropriate storage and bad sampling techniques may lead to errors in the results.

What is the Solution? *

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Online Bushing Monitoring is active method to detect and replace failing bushing to supporting asset management. Run the test without outage so it is continuous monitoring while the bushing in service

Figure 6: Advance Monitoring of transformerhttp://www.ldic.de

Proposed Solution? *

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It is Continuous method to collect of parameter data from power transformer and the analysis it to determine the risk of unexpected.

What is Online Monitoring? *

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Online Bushing theory is based on the relationship between detection of insulation deterioration and measure minimal partial discharge. By applying a test voltage while observing the waveform on an oscilloscope.

What is Online Monitoring? *

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Incorrect design Manufacturing errorsElectrical and Thermal stress due to agingIncrease the risk of failures due to transformer age

Figure: 7 Typical Power Transformerhttp://www.cst.com/Content/Applications/Article/Siemens+Energy+optimises+power+transformers+with+the+aid+of+3D+EM+Simulation Why Online Monitoring is required for Transformer ? *

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The results of monitoring are recorded by different methods and compared with previous result in order to predict the life service of the equipment.

Thermal Imaging Transformer Oil Transformer

Types of Technology Monitoring *

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Transformer Oil AnalysisThermographyUltrasonicVibrationLube Oil AnalysisBattery TestingMotor Testing

Types of Technology Monitoring *

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It is based to measure the sum of current method according to the formula below[2]

Where Sum of Currents

Tangent delta change

Relative Change in bushing capacitance

Initial Capacitance Reading

Initial Sum of Current value

Online Bushing monitoring Procedure*

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In normal situation , the sum of three current is equal to zero as shown in figure 8a[7]. If any defect develops, the sum of three current is not equal to zero due to unbalance system as shown in figure 8b[7].

Online Bushing monitoring Procedure*

Aljuboori AhmedFigure 8: Phase Diagram A, B &C [7]

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DGA is the best detector for any defect in power transformer. The faults detect by DGA is based on measuring of partial discharge in insulation system of transformer.Partial Discharge (PD) may occur small arcs within the insulation system and it destroys the insulation and can lead to breakdown of insulation. Dissolved Gas for Transformer Oil Analysis *

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DGA can detect and give warning based on that each faults produces different level of gases.The type of faults that detect by DGA as following:- CoronaArcingHigh Temperature

Dissolved Gas Analysis*

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The gases may produce from bushing and transformer as following[8] Hydrocarbons and hydrogen gases: methane, ethane,Ethylene, acetylene and hydrogen.Carbon oxide: carbon monoxide and carbon dioxide.Naturally occurring gases: nitrogen and oxygen.

Dissolved Gas Analysis*

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The hydrogen, methane, ethane, ethylene and acetylene are produced this means the fault is oil breakdownHigh levels of hydrogen this means the fault is corona.High levels of acetylene this means the presence of arcing at high temperatures.carbon monoxide this means high temperature.

Dissolved Gas Analysis Results[8]*

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Figure 9: Typical output from on-line DGA monitoring system[9] Dissolved Gas Analysis Results[9]*

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Device accuracy NoiseSystem voltage variations

Factors Affecting Online Accuracy*

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Power transformer is the most expensive equipment in substation. It can be raised the service life of transformer to 60 years. By using Online monitoring, it can be scheduled outage and reduced the repair costs

Benefits: Online Monitoring*

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Online HV Bushing monitoring can give a good result to estimate the transformer aging and provide details for transformer condition.Online program can do testing and monitoring to make sure the equipment is safe for personals and operation.

Conclusion *

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The results of online monitoring can be recorded and compared with previous result in order to predict the life.DGA can detect and give warning of 70% of the most common failure in transformer. Online technology can produce alarm before bushing failure has been occurred.

Conclusion *

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www.Wikipedia.com. Bushing (electrical) [cited 09/2013]; 1:[Available from:http://en.wikipedia.org/wiki/Bushing_(electrical)].2. Kane, Claude, On-line Bushing Monitoring and Comparision to Off- line Testing Dynamic Rating ; 4:[Available from; www.dynamicratings.com/US/Application/Transformers/... /AppNote8.pd...3. http://www.bplglobal.net/eng/knowledge- center/download.aspx?id=2294. http://www.usbr.gov/power/data/fist/fist3_2/vol3-2.pdf

References *

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5. http://www.bplglobal.net/eng/knowledge- center/download.aspx?id=1916. Maik Kock, Michael Kruger, A new Method for On-line Monitoring of Bushings and Partial Discharges of Power Transformer, 2012 IEEE International Conference on Condition Monitoring and Diagnosis23-27 September 2012, Bali,Indonesia7.http://www.eaton.com/ecm/groups/public/@pub/@electrical/doc uments/content/1077779936326.pdf8. S. M. Dhlamini and T. Marwala, "Using SVM, RBF and MLP for bushings," in Proceedings of IEEE Africon, pp. 613 - 617, 2004.

References *

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E. A. Mackenzie, J. Crossey, A. dePablo, W. Ferguson, On-line Monitoring and Diagnostics For Power Transformers, Transformer Services GE Energy

References *

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Aljuboori Ahmed E576 High Voltage Engineering E576 High Voltage Engineering Aljuboori Ahmed *


























Aljuboori Ahmed E576 High Voltage Engineering E576 High Voltage Engineering