active shunt diverter for oltc

Dipin S. AnandM1 Power System

EEE,CETRoll No. 07

A LOW-WEAR OLTC DIVERTER SWITCH FOR VOLTAGE CONTROL

ON DISTRIBUTION NETWORKS

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CONTENTSIntroductionClassic OLTCClassificationsActive Shunt Type OLTC SchemeCircuitsTiming DiagramsArc Energy ComparisonConclusionsReferences17/09/2015 Dept.of EEE,CET

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INTRODUCTIONOLTC is for voltage control(Regulation).Arcless operation of OLTC contacts by providing

zero-current opening and zero-voltage closing with a shunt-connected active element.

Semiconductor devices provide wearless commutation capability during a tap change operation.

Thyristor assisted OLTC scheme.

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Classic OLTC

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Classification of Hybrid OLTC Schemes

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(a) Passive (b) Active series(c) Active shunt17/09/2015 Dept.of EEE,CET

Passive Active Series Active ShuntNo control source. Voltage source in

series with mechanical switch.

Voltage source in series with thyristor path.

Voltage drop across mechanical contact trigger the thyristor.

Voltage source act to trigger thyristor.

Source drive a current equal to the load current.

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Features

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Active Shunt Type : Circuits

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Fig.(a): t<tc17/09/2015 Dept.of EEE,CET

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Fig.(b): tC<t<tD

Circuits contd.

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Fig.(c): tE<t<tF

Circuits contd.

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Fig.(d): tF<t<tG

Circuits contd.

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Fig.(e): tH<t<tI

Circuits contd.

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Fig.(f): t>tI

Circuits contd.

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Timing Diagram

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Fundamental task is to transfer load current between switches SL and SR without interruption.

To ensure zero-current zero-voltage conditions are maintained during switching

Switch closed:Controlled source in current mode.Switch open condition:Controlled source in voltage mode.At zero-crossing,outgoing thyristor goes to blocking mode

and trigger signal applied to incoming thyristor.

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Active Shunt Type OLTC

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Arc Energy as an Indicator of Wear

Greater arc energy leads to greater contact wear.

For a particular event ‘n’ ,arc energy

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to is the time at which switch is opened and te is the time at which arc extinguishes

te

todttIatVaEn ).()(

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The total arc energy over N switching operation may calculated as,

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• Average energy dissipated by the contact,

N

nntot EE

1

NEE tot

av

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Arc Energy

Correlation Between Contact Wear and Total Arc Energy

The calculated total arc energies correlate well with the general visual appearance of the contacts.

High total energies correspond to greater contact wear and vice-versa.

The passive contact experiences between 60 and 300 times the average arc energy of the other electrically loaded contacts.

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CONCLUSIONSHybrid OLTC systems almost completely

eliminate electrical arcing.No other arc elimination scheme is needed

thereby reducing the size and mass of the switching system.

More than one million switching operations are possible by hybrid OLTC scheme.

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REFERENCES

[1] D. Rogers and T. Green, “An active-shunt diverter for onload tap changers,” IEEE Trans. Power Del. , vol.

28, no. 2, pp. 649–657, Apr.2013.[2] D. J. Rogers and T. C. Green, “Zero-current zero-

voltage switching for on-load tap changers,” presented at the 5th IET Int. Conf. Power Electron., Mach. Drives, Brighton, U.K., Apr. 2010.

[3] G. Cooke and K. Williams, “New thyristor assisted diverter switch for on load transformer tap changers,” in Proc. Inst.Elect. Eng., B Elect.Power Appl., Nov. 1992, vol. 139, no. 6, pp. 507–511.

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[4] D. J. Rogers and T. C. Green, “A hybrid diverter design for distribution level on-load tap changers,” in Proc.

IEEE Energy Convers. Congr.Expo., Sep. 2010, pp. 1493–1500.

[5] J. Faiz, B Siahkolah, “New Solid-State Onload Tap-Changers Topology for Distribution Transformers”,

IEEE Transactions on Power Delivery, vol. 18, pp. 136-141, January 2003

[6] Telk,Angamaly, “Instruction Manual for ON LOAD TAP CHANGERS”

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Thank You

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