METHOD AND APPARATUS FOR MITIGATION OF DYNAMIC OVERVOLTAGE

• US 20100053830A1
• Filed: 02/26/2008
• Published: 03/04/2010
• Est. Priority Date: 02/27/2007
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited
• Original Assignee: ABB Technology AG (ABB Limited)
• Inventors: Dickmander, David, Daniel, John, Bjorklund, Hans, Andersson, Ulf
• Granted Patent: US 8,411,400 B2
• Time in Patent Office: Days
• US Class Current: 361/91.100
• CPC Class Codes: G05F 1/00 Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
• CPC Class Codes: H02H 3/023 by short-circuiting
• CPC Class Codes: H02H 7/04 for transformers

Abstract

A method and apparatus for mitigating dynamic overvoltage (DOV) in an AC network. A distribution and power transformer has its primary connected to the high voltage bus of the network and its secondary connected to a switching device. Upon the occurrence of a condition known to cause a DOV and the DOV a control system cause the switching device to change from a nonconductive mode to a conductive mode in less than the time for one cycle of the operating frequency of the AC network. This change in switching device conduction places a short circuit across the transformer secondary.

Claims

1. An apparatus for mitigating in less than the time for one cycle of a predetermined operating frequency of an AC network a short term dynamic overvoltage on said AC network, said apparatus comprising:

a distribution and power transformer having a primary connected to a high voltage bus and a secondary connected to a switching device that can switch from a nonconductive mode to a conductive mode within a time that is less than the time for one cycle of said network predetermined operating frequency;

a system connected to said switching device, said system capable of detecting the occurrence of a condition known to cause a dynamic overvoltage on said AC network and the occurrence of a dynamic overvoltage on said AC network and causing said switching device to change in less than said time for one cycle of said predetermined operating frequency from said nonconductive mode to said conductive mode to thereby short circuit said transformer secondary when both said occurrence of a condition known to cause a dynamic overvoltage on said AC network and the occurrence of a dynamic overvoltage on said AC network are detected at the same time.

2. The apparatus of claim 1 wherein said system comprises a control system connected to said switching device;

and

said apparatus further comprises a detector for detecting both the occurrence of a condition known to cause a dynamic overvoltage on said AC network and the occurrence of a dynamic overvoltage on said AC network, said detector providing a signal to said control system upon detecting both of said occurrences, said control system responsive to said signal to cause said switching device to change in less than said time for one cycle of said predetermined operating frequency from said nonconductive mode to said conductive mode to thereby short circuit said transformer secondary.

3. The apparatus of claim 2 wherein said detector further comprises:

a first detector for detecting the occurrence of a condition known to cause a dynamic overvoltage on said AC network and providing a signal indicative thereof to said control system; and

a second detector for detecting the occurrence of a dynamic overvoltage on said AC network and providing a signal indicative thereof to said control system;

said control system responsive when said signal indicative of the occurrence of said dynamic overvoltage condition and signal indicative of the occurrence of said dynamic overvoltage occurrence are both present to cause said switching device to change from said nonconductive mode to said conductive mode.

4. A method for mitigating in less than the time for one cycle of a predetermined operating frequency of an AC network a short term dynamic overvoltage on said AC network, said method comprising:

detecting the occurrence of a condition known to cause a dynamic overvoltage on said AC network and the occurrence of a dynamic overvoltage on said AC network; and

causing a switching device connected to the secondary of a transformer whose primary is connected to said AC network to change in less than the time for one cycle of said predetermined operating frequency from a nonconductive mode to a conductive mode to thereby short circuit said transformer secondary when both said occurrence of a condition known to cause a dynamic overvoltage on said AC network and the occurrence of a dynamic overvoltage on said AC network are detected at the same time.

5. The method of claim 4 further comprising:

providing a signal to a control system connected to said switching device when both the occurrence of a condition known to cause a dynamic overvoltage on said AC network and the occurrence of a dynamic overvoltage on said AC network are determined; and

using said signal to cause said short circuit within a time that is less than the time for one cycle of said network predetermined operating frequency the secondary of a transformer whose primary is connected to said power network.

6. The method of claim 5 further comprising:

providing a first signal to said control system when the occurrence of a condition known to cause a dynamic overvoltage on said AC network;

providing a second signal to said control system when a dynamic overvoltage occurs on said AC network;

using said first and second signals to short circuit said transformer secondary.