Safety device for a power transformer, and related power transformer using such a safety device

Patent metadata

Field	Value
Publication number	US-9728357-B2
Application number	US-201514596697-A
Country	US
Kind code	B2
Filing date	Jan 14, 2015
Priority date	Jul 20, 2012
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

A safety device is disclosed for a power transformer containing a cooling liquid, and can include a shaped body having an inner chamber which is suitable to be at least partially immersed in cooling liquid and inside which gas can accumulate; a first floating element and a second floating element suitable to be at least partially immersed in and moved by cooling liquid; and a switch suitable to be actuated by the first floating element when the gas accumulated is such that the level of the cooling liquid in the inner chamber reaches a predetermined first threshold level and by the second floating element when the gas accumulated is such that the level of the cooling liquid in the inner chamber reaches a lower predetermined second threshold level, respectively. The first and second floating elements can be mounted on and move linearly relative to one or more corresponding guiding supports.

First claim

The invention claimed is:

1. A safety device suitable to be associated with a power transformer containing a cooling liquid, the safety device comprising:
a shaped body having an inner chamber configured to be at least partially immersed in cooling liquid and inside which gas can accumulate;
a first floating element and a second floating element configured to be at least partially immersed in and moved by cooling liquid;
switching means for actuation by said first floating element when the gas accumulated is such that a level of cooling liquid in the inner chamber reaches a predetermined first threshold level, and by said second floating element when the gas accumulated is such that the level of said cooling liquid in the inner chamber reaches a lower predetermined second threshold level, respectively; and
wherein said first floating element and said second floating element are mounted on and are configured to move linearly along a reference axis relative to one or more corresponding guiding supports.

2. The safety device according to claim 1 , wherein said first floating element and said second floating element are mounted both on and configured to move linearly relative to a common guide support.

3. The safety device according to claim 1 , wherein said switching means comprise:
a first magnetic switch, wherein at least one first magnet is placed on and is configured to move solidly with said first floating element so as to activate said first magnetic switch when the first floating element reaches a position corresponding to said predetermined first threshold level.

4. The safety device according to claim 3 , wherein said switching means comprise:
a second magnetic switch, wherein at least one second magnet is placed on and is configured to move solidly with said second floating element so as to activate said second magnetic switch when the second floating element reaches a position corresponding to said predetermined second threshold level.

5. The safety device according to claim 1 , comprising:
a stopper suitable to interact with and stop said first floating element when the first floating element reaches a position corresponding to said predetermined first threshold level.

6. The safety device according to claim 1 , comprising:
a transducer having a cursor configured to be at least partially immersed in and moved by movements of said cooling liquid, said transducer being arranged to output signals indicative of an actual position of the cursor to an associated electronic unit.

7. The safety device according to claim 6 , wherein said second floating element is mounted on and configured to solidly move with said cursor.

8. The safety device according to claim 6 , wherein said transducer comprises:
a shaped body forming a common guide support as the guiding supports.

9. The safety device according to claim 6 , wherein said transducer comprises:
a potentiometer.

10. The safety device according to claim 1 , comprises:
a further movable element configured to be at least partially immersed in and moved by said cooling liquid, said further movable element being arranged to detect if an actual flow rate of said cooling liquid exceeds a predetermined third threshold and to actuate an associated switch suitable to disconnect an electric power connection to be used for feeding a power transformer.

11. A power transformer comprising:
a tank at least partially filled with a cooling liquid; and
at least one safety device according to claim 1 configured for operation by the cooling liquid.

12. The safety device according to claim 2 , wherein said switching means comprise:
a first magnetic switch, wherein at least one first magnet is placed on and is configured to move solidly with said first floating element so as to activate said first magnetic switch when the first floating element reaches a position corresponding to said predetermined first threshold level.

13. The safety device according to claim 12 , wherein said switching means comprise:
a second magnetic switch, wherein at least one second magnet is placed on and is configured to move solidly with said second floating element so as to activate said second magnetic switch when the second floating element reaches a position corresponding to said predetermined second threshold level.

14. The safety device according to claim 13 , comprising:
a stopper suitable to interact with and stop said first floating element when the first floating element reaches a position corresponding to said predetermined first threshold level.

15. The safety device according to claim 14 , comprising:
a transducer having a cursor configured to be at least partially immersed in and moved by movements of said cooling liquid, said transducer being arranged to output signals indicative of an actual position of the cursor to the associated electronic unit.

16. The safety device according to claim 15 , wherein said second floating element is mounted on and configured to solidly move with said cursor.

17. The safety device according to claim 15 , wherein said transducer comprises:
a shaped body forming said common guide support.

18. The safety device according to claim 15 , wherein said transducer comprises:
a potentiometer.

19. The safety device according to claim 15 , comprises:
a further movable element configured to be at least partially immersed in and moved by said cooling liquid, said further movable element being arranged to detect if an actual flow rate of said cooling liquid exceeds a predetermined third threshold and to actuate an associated switch suitable to disconnect an electric power connection to be used for feeding a power transformer.

20. A power transformer comprising:
a tank at least partially filled with a cooling liquid; and
at least one safety device according to claim 15 configured for operation by the cooling liquid.

Assignees

• Abb Technology Ag
• Abb Schweiz Ag

Inventors

• Tonin Andrea
• Carollo Carlo
• Manco Giuseppe Leonardo

Classifications

• H01F2027/404

  Protective devices specially adapted for fluid filled transformers · CPC title

• H01H33/555 Primary

  Protective arrangements responsive to abnormal fluid pressure, liquid level or liquid displacement, e.g. Buchholz relays (circuits H02H5/08; specially adapted for transformers H01F27/402) · CPC title

• H02H5/08

  responsive to abnormal fluid pressure, liquid level or liquid displacement, e.g. Buchholz relays · CPC title

• H01H36/02

  actuated by movement of a float carrying a magnet · CPC title

• H01H35/40

  actuated by devices allowing continual flow of fluid, e.g. vane · CPC title