Tap changer with an improved monitoring system

Patent metadata

Field	Value
Publication number	US-9697962-B2
Application number	US-201314036742-A
Country	US
Kind code	B2
Filing date	Sep 25, 2013
Priority date	Mar 27, 2011
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

An on-load tap changer is provided having a plurality of modules, each of which is operable to change taps in a transformer winding. The tap changer includes a motor connected to rotate at least one shaft. The at least one shaft is connected to the tap change modules and is operable upon rotation to cause the tap change modules to each perform a sequence of operations that effectuate a tap change. A multi-turn absolute encoder is connected to the at least one shaft. A monitoring system is connected to the encoder and is operable to determine from the position of the at least one shaft where the tap change modules are in the sequence of operations.

First claim

What is claimed is:

1. An on-load tap changer for making tap changes in a transformer winding, the tap changer comprising
(a.) a tap change module connected to the transformer winding and comprising a bypass switch assembly, a vacuum interrupter assembly and a selector switch assembly;
(b.) a motor connected to rotate at least one shaft, wherein the at least one shaft is connected to the tap change module and is operable upon rotation to cause the tap change module to perform a sequence of operations that effectuate a tap change, the operations comprising actuating the bypass switch assembly, actuating the vacuum interrupter assembly and actuating the selector switch assembly;
(c.) a multi-turn absolute encoder connected to the at least one shaft and operable to determine a position of the at least one shaft; and
(d.) a monitoring system connected to the encoder to receive the position of the at least one shaft and operable to monitor a tap change by determining from the position of the at least one shaft where the tap change module is in the sequence of operations, wherein the monitoring system is operable to monitor the tap change by measuring the time required to perform at least one of the operations and determining that an error has occurred if the at least one of the operations was not timely performed, wherein the monitoring system is further operable to measure the total time required to perform all of the operations, and wherein an error is determined to have occurred if the total time required to perform all of the operations is greater than a predetermined amount of time, and wherein none of the operations are individually timed.

2. An on-load tap changer for making tap changed in a transformer winding, the tap changer comprising:
(a.) a tap change module connected to the transformer winding and comprising a bypass switch assembly, a vacuum interrupter assembly and a selector switch assembly;
(b.) a motor connected to rotate at least one shaft, wherein the at least one shaft is connected to the tap change module and is operable upon rotation to cause the tap change module to perform a sequence of operations that effectuate a tap change, the operations comprising actuating the bypass switch assembly, actuating the vacuum interrupter assembly and actuating the selector switch assembly;
(c.) a multi-turn absolute encoder connected to the at least one shaft and operable to determine a position of the at least one shaft;
(d.) a monitoring system connected to the encoder to receive the position of the at least one shaft and operable to monitor a tap change by determining from the position of the at least one shaft where the tap change module is in the sequence of operations, wherein the monitoring system is operable to monitor the tap change by measuring the time required to perform at least one of the operations and determining that an error has occurred if the at least one of the operations was not timely performed, wherein the monitoring system is further operable to measure current flowing through the vacuum interrupter assembly, and wherein the monitoring system is further operable to monitor the tap change by:
determining whether current through the vacuum interrupter assembly is properly present or absent after at least one of the operations has been completed; and
determining that an error has occurred if current through the vacuum interrupter assembly is not properly present or absent after the at least one of the operations has been completed.

3. The on-load tap changer of claim 2 , wherein the monitoring system is operatively connected to the motor to control the operation of the motor.

4. The on-load tap changer of claim 3 , wherein the selector switch assembly comprises a movable contact, the movable contact moving from being connected to a beginning tap of the transformer winding to being connected to an ending tap of the transformer winding during a tap change, and wherein when the monitoring system determines that an error has occurred, the monitoring system is operable to handle the error by controlling the motor to either continue the tap change and move the movable contact to being connected to the ending tap, or cancel the tap change and move the movable contact back to being connected to the beginning tap, depending on where the tap change module is in the sequence of operations.

5. The on-load tap changer of claim 4 , wherein the monitoring system is operable to handle the error by, after controlling the motor to either continue the tap change or cancel the tap change, cutting off power to the motor.

6. The on-load tap changer of claim 4 , wherein the bypass switch assembly comprises a bypass switch and the vacuum interrupter assembly comprises a vacuum interrupter having a pair of contacts disposed in a vacuum bottle, and wherein the sequence of operations comprises:
(a.) opening the bypass switch;
(b.) after operation (a.), opening the contacts of the vacuum interrupter;
(c.) after operation (b.), moving the movable contact from the beginning tap to the ending tap;
(d.) after operation (c.), closing the contacts of the vacuum interrupter; and
(e.) after operation (d.), closing the bypass switch.

7. The on-load tap changer of claim 6 , wherein if an error is determined to have occurred before operation (d.) has been completed, the monitoring system is operable to cancel the tap change and move the movable contact back to the beginning tap.

8. The on-load tap changer of claim 6 , wherein after operation (a.) and before operation (b.), the monitoring system is operable to determine whether current is flowing through the vacuum interrupter, and if current is not flowing through the vacuum interrupter, the monitoring system is operable to determine that an error has occurred.

9. The on-load tap changer of claim 6 , wherein in monitoring the tap change by the monitoring system, the monitoring system is operable to measure the times required to perform operations (a.), (b.) and (e.), respectively; and
wherein the monitoring system is operable to determine an error has occurred if the time required to perform operation (a.) is greater than a first predetermined amount of time, or if the time required to perform operation (b.) is greater than a second predetermined amount of time, or if the time required to perform operation (c.) is greater than a third predetermined amount of time.

10. The on-load tap changer of claim 1 , wherein the at least one shaft comprises a motor shaft connected by a transmission shaft to the tap change module; and
wherein the encoder is connected to the motor shaft and is operable to determine the position of the motor shaft.

11. The on-load tap changer of claim 1 , wherein the at least one shaft comprises a motor shaft, a transmission shaft connected between the motor shaft and the tap change module, and a first side shaft connected by at least one gear to the transmission shaft so as to rotate therewith; and
wherein the multi-turn absolute encoder is connected to the first side shaft and is operable to determine the position of the first side shaft.

12. An on-load tap changer for making tap changes in a transformer winding, the tap changer comprising:
(a.) a tap change module connected to the transformer winding and comprising a bypass switch assembly, a vacuum interrupter assembly and a selector switch assembly;
(b.) a motor connected to rotate at least one shaft wherein the at least one shaft is connected to the tap change module and is operable upon rotation to cause the tap change module to perform a sequence of operations that effectuate a tap change, the operations comprising actuating the bypass switch assembly,

Assignees

• Teising William James
• Elick Robert Alan
• Abb Schweiz Ag

Inventors

• Teising William James
• Elick Robert Alan

Classifications

• H01H9/0038

  making use of vacuum switches · CPC title

• H01H3/30

  using spring motor · CPC title

• H02J3/00

  Circuit arrangements for AC mains or AC distribution networks · CPC title

• H01H3/54

  Mechanisms for coupling or uncoupling operating parts, driving mechanisms, or contacts · CPC title

• H01H3/605

  making use of a fluid damper · CPC title