System and method for operating an on-load tap changer

Patent metadata

Field	Value
Publication number	US-9570252-B2
Application number	US-201414164620-A
Country	US
Kind code	B2
Filing date	Jan 27, 2014
Priority date	Jan 27, 2014
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

A system for operating an on-load tap changer (OLTC) includes a plurality of legs that include mechanical switches. At least one leg switches from a first to a second tap of the OLTC on receipt of a tap change signal. At least one mechanical switch is activated to establish an electrical connection between one of the first and the second tap and a power terminal of the OLTC. Further, the system includes semiconductor switches that are parallel to the mechanical switches and when activated electrically couple one of the first and the second tap and the power terminal. The system includes a processing unit that selectively activates and deactivates the mechanical and semiconductor switches in such a way that electrical contact is maintained between at least one of the taps and the power terminal during the transition of at least one leg from the first tap to the second tap.

First claim

The invention claimed is:

1. A system for operating an on-load tap changer, the system comprising:
a plurality of legs, at least one of which is triggered to switch from a first tap to a second tap of the on-load tap changer on receipt of a tap change signal, wherein each leg includes at least one mechanical switch, and wherein when at least one mechanical switch of at least one of the plurality of legs is switched on an electrical connection is established between one of the first and the second tap and a power terminal of the on-load tap changer; and
a plurality of semiconductor switches, each semiconductor switch being placed parallel to the mechanical switches and when activated provide electrical connection between one of the first and the second tap and a power terminal of the on-load tap changer;
a processing unit configured to selectively activate and deactivate the mechanical switches and the semiconductor switches in such a way that electrical contact is maintained between at least one of the taps and the power terminal during the transition of at least one leg from the first tap to the second tap without causing short circuit between two taps;

wherein the processing unit is further configured to:
generate the tap change signal to move the at least one leg from the first tap to the second tap when a condition for tap changing is met;
generate activation signals for the semiconductor switches when the tap change signal is generated; and
generate a plurality of deactivation signals for the mechanical switches of the at least one leg coupled with the first tap when a condition for tap changing is met.

2. The system of claim 1 , further comprising a leg driving system configured to receive the tap change signal from the processing unit and causing the at least one leg to move in the direction of the second tap.

3. The system of claim 1 , wherein the processing unit is further configured to:
generate a first deactivation signal for the semiconductor switches that are coupled to a first leg from the plurality of legs that is changing position from the first tap towards the second tap before the first leg is decoupled from the first tap;
generate a second deactivation signal for one or more of the plurality of semiconductor switches coupled to a second leg once the first leg is coupled with the second tap;
generate a first activation signal for the mechanical switch that couples the first leg to the power terminal when the first leg is coupled with the second tap;
generate a second activation signal for the remaining mechanical switches that couple the plurality of legs to the power terminal; and
generate a third deactivation signal for the plurality of semiconductor switches.

4. The system of claim 1 further comprising at least one snubbing device that is coupled in parallel to the plurality of semiconductor switches.

5. The system of claim 1 , wherein the semiconductor switches comprise a bidirectional switch or a unidirectional switch.

6. The system of claim 1 , wherein the semiconductor switches comprise at least one of a MOSFET, IGBT, and IGCT.

7. The system of claim 1 , wherein the on-load tap changer comprises a rotary tap selection mechanism.

8. The system of claim 1 , wherein the on-load tap changer comprises a linear tap selection mechanism.

9. A method for operating an on-load tap changer, the method comprising:
activating a plurality of semiconductor switches coupled to at least one of a plurality of legs on one end and a power terminal on the other end when a condition for tap changing is met, wherein the at least one leg is electrically coupled to a first tap of a plurality of taps of the on-load tap changer;
deactivating one or more mechanical switches that are placed in parallel to the plurality of semiconductor switches and are coupled to the at least one of the plurality of legs on one end and the power terminal on the other end;
moving the at least one of the plurality of legs from the first tap towards a second tap;
selectively activating and deactivating the plurality of semiconductor switches such that the semiconductor switches that are coupled to a moving leg that is in electrical contact with at least one tap are in an active state and the semiconductor switches that are coupled to a moving leg that is not in electrical contact with any tap are in a deactivated state; and
activating the one or more mechanical switches which are coupled to the at least one of the plurality of legs that is in electrical contact with the second tap.

10. The method of claim 9 , further comprising:
generating a plurality of activation signals for the plurality of semiconductor switches when the condition for tap changing is met; and
generating deactivation signals for the mechanical switches when the condition for tap changing is met.

11. The method of claim 10 , wherein selectively activating and deactivating further comprises:
generating a first deactivation signal for the semiconductor switches that are coupled to a first leg from the plurality of legs that is changing position from the first tap towards the second tap before the first leg is decoupled from the first tap;
generating a second deactivation signal for one or more of the plurality of semiconductor switches coupled to a second leg once the first leg is coupled with the second tap;
generating a first activation signal for the mechanical switch that couples the first leg to the power terminal when the first leg is coupled with the second tap;
generating a second activation signal for the remaining mechanical switches that couple the plurality of legs to the power terminal; and
generating a third deactivation signal for the plurality of semiconductor switches.

12. The method of claim 10 , wherein selectively activating and deactivating further comprises:
generating a first activation signal for one or more of the plurality of semiconductor switches that are coupled to a first leg from the plurality of legs when the first leg is coupled to the second tap;
generating a first deactivation signal for one or more of the plurality of semiconductor switches coupled to a second leg once the first leg is coupled with the second tap, wherein the second leg is coupled to the first tap; and
generating a second activation signal for the mechanical switch that couples the first leg to the power terminal.

13. The method of claim 12 , further comprising generating a second deactivation signal for the plurality of semiconductor switches.

Assignees

• Gen Electric

Inventors

• Wijekoon Piniwan Thiwanka Bandara
• Baerthlein Eva-Maria
• Schramm Simon Herbert
• Schroeder Stefan
• Panosyan Ara
• Gupta Rohit Kumar

Classifications

• H01H2009/546

  the static switching means being triggered by the voltage over the mechanical switch contacts · CPC title

• H01F29/04

  having provision for tap-changing without interrupting the load current · CPC title

• H01H9/542 Primary

  Contacts shunted by static switch means · CPC title

• H01H9/0016

  Contact arrangements for tap changers · CPC title

• H01H9/0027

  Operating mechanisms · CPC title