This document discusses a low-wear on-load tap changer (OLTC) diverter switch for voltage control on distribution networks. It introduces classic OLTCs and classifications of hybrid OLTC schemes, focusing on the active shunt type. The active shunt type circuits and timing diagrams are presented, showing how thyristors commutate load current between switches without interruption. Arc energy comparisons show the active shunt type experiences much less contact wear than passive designs. It is concluded that hybrid OLTC systems can eliminate electrical arcing and allow over a million switching operations with reduced size.

1. Dipin S. Anand
M1 Power System
EEE,CET
Roll No. 07
A LOW-WEAR OLTC DIVERTER
SWITCH FOR VOLTAGE CONTROL
ON DISTRIBUTION NETWORKS
17/09/2015 Dept.of EEE,CET
1

2. 2
CONTENTS
 Introduction
 Classic OLTC
 Classifications
 Active Shunt Type OLTC Scheme
 Circuits
 Timing Diagrams
 Arc Energy Comparison
 Conclusions
 References
17/09/2015 Dept.of EEE,CET

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.
17/09/2015 Dept.of EEE,CET

4. 4
Classic OLTC
17/09/2015 Dept.of EEE,CET

5. Classification of Hybrid OLTC Schemes
5
(a) Passive (b) Active series(c) Active shunt
17/09/2015 Dept.of EEE,CET

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.
6
Features
17/09/2015 Dept.of EEE,CET

7. Active Shunt Type : Circuits
7
Fig.(a): t<tc
17/09/2015 Dept.of EEE,CET

8. 8
Fig.(b): tC<t<tD
Circuits contd.
17/09/2015 Dept.of EEE,CET

9. 9
Fig.(c): tE<t<tF
Circuits contd.
17-09-15
Dept.of EEE,CET

10. 10
Fig.(d): tF<t<tG
Circuits contd.
17/09/2015 Dept.of EEE,CET

11. 11
Fig.(e): tH<t<tI
Circuits contd.
17/09/2015 Dept.of EEE,CET

12. 12
Fig.(f): t>tI
Circuits contd.
17/09/2015 Dept.of EEE,CET

13. Timing Diagram
13
17/09/2015 Dept.of EEE,CET

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.
14
Active Shunt Type OLTC
17/09/2015 Dept.of EEE,CET

15. Arc Energy as an Indicator of Wear
 Greater arc energy leads to greater contact wear.
 For a particular event ‘n’ ,arc energy
15
to is the time at which switch is opened and
te is the time at which arc extinguishes

te
to
dttIatVaEn ).()(
17/09/2015 Dept.of EEE,CET

16.  The total arc energy over N switching operation
may calculated as,
16
• Average energy dissipated by the contact,


N
n
ntot EE 1
N
EE tot
av

17/09/2015 Dept.of EEE,CET
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.
17
17/09/2015 Dept.of EEE,CET

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.
18
17/09/2015 Dept.of EEE,CET

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.
19
17/09/2015 Dept.of EEE,CET

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”
20
17/09/2015 Dept.of EEE,CET

21. Thank You
21
Dept.of EEE,CET17/09/2015