WO2012089235A1

WO2012089235A1 - Oil level indicator with electronic output

Info

Publication number: WO2012089235A1
Application number: PCT/EP2010/070757
Authority: WO
Inventors: Carlo Carollo; Andrea Tonin; Moreno Giovanni DALLA VECCHIA
Original assignee: Abb Technology Ag
Priority date: 2010-12-27
Filing date: 2010-12-27
Publication date: 2012-07-05
Also published as: EP2659240A1; CN103270398A

Abstract

An oil level indicator comprising a float connected to a rod which are suitable to move within an oil filled vessel of an associated power equipment; a magnet is connected to the rod, and a magnetic sensor is provided in front of the magnet 6 for detecting a change or variation of the magnetic field provided by the magnet when the float 1 and the rod 2 move due to a change of the oil level inside the vessel. The magnetic sensor comprises a microchip set inside an electronic board (7) for giving a digital output indicative of the change of oil level inside the vessel.

Description

OIL LEVEL INDICATOR WITH ELECTRONIC OUTPUT

The present invention relates to an oil level indicator for oil-filled electrical power equipment.

More particularly, the invention relates to an oil level indicator with a digital signal that can be remotely transmitted.

The present invention relates also to a power transformer comprising such an oil level indicator.

Electric power equipments containing insulating oil, such as transformers and the like, usually include an oil filled expansion vessel, which is provided in order to compensate the unavoidable alterations in the volume of oil, that are created inside the equipments, due to sudden changes in temperature.

The oil filled expansion vessel or conservator is also supplied with air previously treated in a special dryer for eliminating or drastically reducing the humidity and in order to measure the correct values of the breakdown voltage.

The insulating or cooling oil flows within the oil filled expansion vessel during heating up of the electrical power apparatus and returns from the vessel to the electrical power apparatus as the temperature drops and consequently the oil contracts.

Usually an oil level indicator is also used to measure the oil level in the oil filled expansion vessel and particularly in the oil filled transformer conservator.

Said oil level indicator is provided for checking that the transformer is well filled and also to prevent oil leakages, in case of an oil increasing and overcoming a maximum level.

In case of oil decreasing, the indicator is also able to show that a minimum level has been reached, so as to prevent that the windings are without oil. With reference to the enclosed drawings, in figure 1 a traditional oil level indicator is shown, in which a float 1 is normally operatively connected to a float rod 2; in operation, the movements of the float 1 within the oil filled transformer conservator 3 due to variations of the oil level are converted into a rotation of the float rod 2.

The float rod 2 is in turn connected with a gauge disk of an electric power equipment, such as a transformer 4, by means of a magnetic joint for safety reasons; moreover, the gauge disk operates the movement in a display 5 to provide to the user a clear visualization of the oil level indication.

Usually the magnetic joint is realized by the magnetic coupling of two sets of magnets, each set comprising for example two magnets.

A first set of magnets is positioned inside the conservator 3 and is operatively coupled to the float rod 2; the second set of magnets is instead positioned outside the conservator 3 together with and operatively coupled to the gauge disk.

In this way, for every variation in the level of the liquid (oil), there is a corresponding rotation of the magnetic joint and a consequent variation of the indication on a dial of the gauge disk occurs.

The display 5 is also closed with a screen-printed disk having an indicator which rides on or over a scale and reference marks corresponding to the levels that the oil should reach at fixed temperatures.

There are normally some switches to indicate the minimum and the maximum level in the transformer conservator 3.

A further type of oil level indicator for electrical power equipments is also known, which produces a continuous analog electric signal as a measure of the degree of the vessel filling.

Said oil level indicator is provided with an indicator shaft, which is placed in a display part of the unit and which is connected with a potentiometer, so that the measured state of filling of the conservator is converted into an angular displacement of the shaft of the potentiometer, thus supplying an analog signal representing the liquid (oil) level.

Said known oil level indicators has however some drawbacks, among which the major drawback is constituted by the fact that a direct visualization of the indicator is always needed; in other words, the oil level indicator of an oil filled conservator of electrical power equipments cannot be verified by an operator from a remote position, but only staying in front of it.

This is a serious problem mainly in case the electrical power equipment is employed in a huge implant that requires a careful and constant check by an operator.

In particular, said drawback also causes an increase of operation costs and it is a severe obstacle to a lean manufacturing.

Furthermore, it also causes an impediment to the safety of the implant, because in emergency circumstances a person should be in proximity of the danger to notice the situation and communicate it to the workmen. An important aim of the present invention is therefore to provide an oil level indicator for oil filled electrical power equipments with an electronic output.

Another aim of the present invention is to provide an oil level indicator for oil filled electrical power equipments that is more reliable and efficient than the equivalent of a known type oil level indicator.

A further aim of the present invention is to provide an oil level indicator for oil filled electrical power equipments making it possible to monitor the safety conditions of the power equipment in a more effective measure than the ones known to the state of the art.

Moreover, an additional aim of the present invention is to realize an oil level indicator for oil filled electrical power equipments, which allows a simplified construction and lower manufacturing costs, with respect to the prior art.

These and other aims are achieved through the implementation of an oil level indicator for oil filled electrical power equipments according to the enclosed claim 1 .

Other technical details of the oil level indicator for oil filled electrical power equipments, which is the subject of the present invention, are set forth in the respective dependent claims.

Advantageously, the oil level indicator according to the invention enables accurate measurements of oil level in oil filled transformer conservators and, indirectly, increases the degree of safety in electrical power plants, while maintaining a high level of functional efficiency of the equipments involved.

The oil level indicator of the present invention is also easy to manufacture and requires low manufacturing costs with respect to the prior art.

The aims and advantages mentioned above will appear more evident from the following description, referring to a preferred embodiment of the invention, that is given for an exemplifying but not limiting purpose, and to the attached drawings, in which:

- figure 1 is a partially perspective view of a known oil level indicator used to measure the oil level in oil filled transformer conservators, and

- figure 2 is a partially section view of a portion of an oil level indicator with electronic output for oil filled transformer conservators, according to the present invention;

- figure 3 shows an exemplary power transformer comprising an oil level indicator according to the present invention; - figure 4 is a sketch schematically representing the oil level indicator according to the invention.

In the following description, components of the oil level indicator according to the invention which are the same or similar to components illustrated in the known indicator of figure 1 will be referred to with the same reference numerals for the sake of simplicity.

Further, the oil level indicator according to the invention will be hereinafter described by making particular reference to its use with a conservator of power transformer without intending in any way to limit its possible scope and field of application.

Figure 3 shows an exemplary power transformer 100 comprising a tank 10 housing the active parts of the transformer, e.g. the magnetic core and windings, and an oil-filled conservator 3.

An oil level indicator is operatively associated to the conservator 3, and as above discussed, it includes a float rod 2 which converts the movements of an associated float 1 within the oil filled transformer conservator 3 into a movement, e.g. a rotation, of an indicator of a signalling dial or disk 8. For the sake of simplicity, in figures 1 -2 there is illustrated only a wall of the conservator 3 which is operatively coupled to the float rod 2.

In the exemplary embodiment illustrated in figure 3, the signalling dial or disk 8 is in turn covered by a display 5 and is positioned on the opposite side of the wall of the conservator 3 with respect to the float rod 2.

The components of the oil-level indicator according to the invention which are positioned inside the conservator 3, e.g. the float 1 and float road 2, are operatively coupled to the components of the indicator itself which are positioned outside the conservator 3, e.g. the signalling dial or disk 8, preferably by a magnetic coupling; as previously described, also in the oil level indicator of figure 3 such magnetic coupling can be realized for instance by means of two sets of magnets, each set comprising for example two magnets.

A first set of magnets is positioned inside the conservator 3 and is operatively coupled to the float rod 2; the second set of magnets is instead positioned outside the conservator 3 together with and operatively coupled to the disk 8.

Advantageoulsy, in the oil level indicator according to the invention, the part of the magnetic joint that is positioned outside the body of the conservator 3 is connected to an additional magnet 6, which is placed in front of an electronic board or unit 7. Such an electronic board or unit 7, is for instance a microprocessor based circuit which is suitable to output digital signals according to solutions readily available for those skilled in the art and therefore not described herein in details.

For every variation in the level of the liquid (oil), there is a corresponding rotation of the magnetic joint and a consequent rotation of the magnet 6 thus modifying the associated magnetic field.

In the electronic board 7 there is a magnetic sensor 9, which is suitable for detecting variations of the magnetic field created by the magnet 6 and hence for detecting the position of the magnet 6 itself.

This means that it is possible to have a digital information of the oil level in the conservator.

In a preferred embodiment of the present invention, the magnetic sensor able to detect the position of the magnet 6 fixed in the magnetic joint consists of a special microchip which is sensitive to magnetic fields, and in particular to the rotation of an existing magnetic field; this electronic sensor 9 is fitted inside the electronic board 7, preferably facing the magnet 6 and being able to detect the position of the magnet 6.

Such a microchip can be for example the model number AS5040 marketed by Austriamicrosystem; obviously, other similar devices or sensors can be successfully applied.

When a variation in the level of the oil occurs inside the conservator 3, there is a corresponding rotation of the magnet 6, which changes the magnetic field in front of the magnetic sensor 9 and the magnetic sensor 9 gives a proportional digital output; the digital output can also be advantageously remotely transmitted.

Consequently the magnetic sensor 9 becomes a transducer of the float rod 2 position and therefore of the float 1 position in the oil filled transformer conservator 3.

Hence, according to the present invention, an oil level digital value can be thus remotely transmitted, so that said value can be checked in a safer location and can also be continuously controlled, in a reliable and efficient way, by an operator.

In addition, an actual indication of the oil level is always available, even at a remote location; therefore, operators in a remote location have the chance to know in advance if the oil level is approaching dangerous levels. Clearly, such remote indication can be used in alternative or preferably in addition to the local indication provided by the signalling dial or disk 8. The characteristics of the oil level indicator, which is the object of the present invention, are therefore clear from the above description, as well as the related advantages.

Such results are achieved also by means of a very simple structure and can be applied in principle to any type of electrical equipments, especially in power transformers.

Hence another object of the present invention encompasses a power transformer comprising at least one oil level indicator of the type previously described and as defined in the appended claims.

Finally, it is evident that numerous variations can be made to the oil level indicator with electronic output of the present invention, without leaving from the principles of novelty inherent the inventive idea, as it is manifest that, in practical implementation of the invention, materials, shapes and size of the details illustrated may be any, according to requirements, and the same may be replaced with others technically equivalent.

For example, the local disk or dial can be prevented or can be replaced by any other equivalent local indicator of level and the coupling between the components which are positioned inside the conservator and those placed outside can be realized differently from a magnetic way, provided it is in line with functionality required and safety rules.

Claims

1 . Oil level indicator with electronic output for oil filled electrical power equipments, the oil level indicator comprising a float (1 ) connected to a rod (2) which are suitable to move within an oil filled vessel or conservator (3) of an associated power equipment, characterized in that it comprises:

- a magnet (6) which is operatively coupled to said rod (2) so as to move when said rod (2) moves following a displacement of said float (1 ) caused by a change of the oil level; and

- a magnetic sensor (9) which is operatively associated to said magnet (6) for detecting a change or variation of the magnetic field provided by said magnet (6) when said float (1 ) is displaced, said magnetic sensor (9) thus being a transducer of said float (1 ) position.

2. Oil level indicator according to claim 1 , characterized in that it comprises an electronic board (7) for giving a digital output, said electronic board being operatively coupled to said magnetic sensor (9).

3. Oil level indicator according to claim 1 or 2, characterized in that said magnetic sensor (9) consists or comprises a microchip (9) positioned in front of said magnet (6).

4. Oil level indicator according to one or more of the previous claims, characterized in that said microchip is set on said electronic board (7).

5. Oil level indicator according to one or more of the previous claims, characterized in that it comprises a local oil level indicator (8) which is operatively coupled to said rod (2).

6. Oil level indicator according to one or more of the previous claims, characterized in that said digital output is proportional to the variation of said magnetic field and to the movement of said rod (2).

7. Oil level indicator according to one or more of the previous claims characterized in that said electronic board is arranged so as to transmit remotely said digital output.

8. Oil level indicator to one or more of the previous claims characterized it comprises a magnetic joint to which said magnet (6) and said rod (2) are operatively connected to.

9. Power transformer comprising at least one oil level indicator according to one or more of the previous claims.