1. Dipin S. Anand
M1 Power System
EEE,CET
Roll No. 07
A LOW-WEAR OLTC DIVERTER
SWITCH FOR VOLTAGE CONTROL
ON DISTRIBUTION NETWORKS
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3. 3
INTRODUCTION
OLTC 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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5. Classification of Hybrid OLTC Schemes
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(a) Passive (b) Active series(c) Active shunt
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6. Passive Active Series Active Shunt
No 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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7. Active Shunt Type : Circuits
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Fig.(a): t<tc
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14. 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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15. 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
to
dttIatVaEn ).()(
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16. The total arc energy over N switching operation
may calculated as,
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• Average energy dissipated by the contact,
N
n
ntot EE 1
N
EE tot
av
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Arc Energy
17. 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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18. CONCLUSIONS
Hybrid 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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19. 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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20. [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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