FEED-THROUGH DEVICE FOR INTERFACING FIBR- BRAGG-GRATING (FBG) SENSORS INSTALLED IN TURBO GENERATOR TO OUTSIDE MONITORING SYSTEM

FIELD OF INVENTION:

[001] The present invention relates to an arrangement for interfacing the FBG sensors installed inside the electrical machines- turbo-generator (TG), hydro-generator or large–size motors to outside monitoring system. The invention relates to a customized FEED-THROUGH/ interfacing device for direct connection of sensor cables inside the casing and to monitoring system which is outside to a turbo generator casing.

[002] In particular, the present invention provides an arrangement for inter-connecting/ interfacing the fibre-optic FBG sensors cables with the outside measuring/monitoring device/system by a customized device called FEED-THROUGH. The FBG probes are installed on the overhangs of a turbogenerator for measuring vibration/temperature/dynamic strain as per requirement.

BACKGROUND OF INVENTION/PRIOR ART:

[003] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[004] End winding vibration monitoring (EVM) of a turbo generator in operation is very important for trouble-free operation of a turbogenerator. The sensors/ accelerometers employed for monitoring are piezoelectric and fibre-optic types. Nowadays, state-of-art Fibre-Optic(FO) type are widely used. These are different types utilizing various optical phenomenon.

[005] The FBG sensor i.e. FIBR- BRAGG-GRATING sensor which reflects a wavelength of light that shifts in response to variations in vibration/ temperature/strain.

[006] FBGs (FIBR- BRAGG-GRATING sensor) are constructed by using holographic interference or a phase mask to expose a short length of photosensitive fiber to a periodic distribution of light intensity. The refractive index of the fiber is permanently altered according to the intensity of light it is exposed to. The resulting periodic variation in the refractive index is called a fiber Bragg grating. When a broad-spectrum light beam is sent to an FBG, reflections from each segment of alternating refractive index interfere constructively only for a specific wavelength of light, called the Bragg wavelength. This effectively causes the FBG to reflect a specific frequency of light while transmitting all others. Because the Bragg wavelength is a function of the spacing between the gratings, FBGs can be manufactured with various Bragg wavelengths, which enables different FBGs to reflect unique wavelengths of light.

[007] These FBGs are installed on turbogenerator overhangs at specific bar joints for the monitoring of vibration. The output cables of the sensor is routed through water-header/ overhang basket and brought to an opening on the casing. The subject invention FEED-THROUGH device at this point, bolted on casing, interfaces the sensor cables with the outside monitoring system. While facilitating the inter-connections, the feed-through prevents hydrogen leakage. The pressurised hydrogen gas inside the casing is used for cooling the turbogenerator stator and rotor.

[008] The existing feed-throughs are commercially available in different shapes and sizes. However, they cannot be directly used due to limitation of connection points and limitation of opening space available on the turbogenerator casing.

[009] The invented customized feed-through addresses these limitations along with other factors, and can be directly installed/ bolted occupying minimum available space. Hence, the present invention has been introduced.

OBJECTS OF THE INVENTION:

[0010] It is primary object of the invention to provide Feed-through device for interfacing the fibr-bragg-grating (FBG) sensors installed in the turbo generator to outside monitoring system.

[0011] It is the general object and purpose of present invention to provide a FEED THROUGH device to couple/interface the FBG sensors installed inside a turbogenerator to outside monitoring system without any light signal loss.

[0012] Another object of the invention is to provide FEED THROUGH device without any hydrogen leakage/ pressure drop, which also can sustain temperature rise up to 90°C without any adverse reaction on the running of the machine.

[0013] Still further object of the invention is to provide FEED THROUGH device, which occupies minimum space.

[0014] Still another object of the invention is to provide FEED THROUGH device, which facilitates coupling and handling.

[0015] Still one another object of the invention is to provide FEED THROUGH device, which is sturdy, economical and environmental friendly.

[0016] Yet one another object of the invention is to provide FEED THROUGH device, in which number of probes/ channels can be varied depending upon the requirements.

[0017] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:

[0018] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[0019] According to this invention, there is provided Feed-through device for interfacing of fibr-bragg-grating (FBG) sensors installed in the turbo generator to outside monitoring system comprising a tube (1) accommodating Fibre-Optic cables (6) with couplers (5) on both ends, wherein the tube (1) is having a circular step with groove (3) for fixing O-ring (7) and a threaded section (4) for screwing lock/cap nuts (8).

[0020] The circular step with groove (3) is located at an intermediate position and the threaded section (4) is provided at one outer end of the tube (1).

[0021] The tube (1) includes metallic cylindrical tube (1) having centrally drilled hole housing the couplers (5) on each end of Fibre-optic cables (6) potted by potting material/glue (2) in the centrally drilled hole provide connections without loss of light signals emanating from sensors installed on the turbo-generator overhangs.

[0022] The tube (1) is made of metal including hardened, annealed mild chromium steel.

[0023] The couplers (5) are non-metallic and the O-ring (7) is made of resilient material including rubber.

[0024] The potting material (2) comprises resin-hardner mixture in the ratio of 10:1.

[0025] The device is inserted from inside of the casing and bolted on it, facilitating interfacing the inner sensors’ cables to outside monitoring system.

[0026] The potting (2) of the centrally drilled hole and tightened O-ring fixed in the grove of circular step (3) provide a leak-proof sealing arrangement for the cooling gas of the turbo generator.

[0027] The FEED-THROUGH device can be operated at 5bar pressure and temperature of about 90°C during operation of a turbo generator.

[0028] The FEED-THROUGH device provides direct interface with sensors’s cables, installed on turbo generator stator to outside monitoring system.

[0029] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[0030] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0031] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

[0032] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

Figure 1 illustrates Feed-through device for interfacing the fibr-bragg-grating (FBG) sensors installed in the turbo generator to outside monitoring system according to the present invention.
Figure 2 illustrates the metallic lock-nut/ cap-nut of the present invention.
Figure 3 illustrates the rubber O-ring of the present invention.

[0033] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

[0034] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0035] The present invention makes a disclosure regarding a technology pertaining to an invention on Feed-through device for interfacing the fibr-bragg-grating (FBG) sensors installed in the turbo generator to outside monitoring system.

[0036] The arrangement of the present invention is illustrated in the Fig.-1 to 3 indicating the following components:
1. Metallic Cylindrical Tube
2. Plurality of Potting Material
3. Plurality of Circular Step with groove for O-ring
4. Plurality of Threaded section for nuts
5. Plurality of Non-metallic Couplers
6. Fibre-Optic Cables for coupling
7. Resilient (Rubber) O-ring
8. Lock/Cap Nut

[0037] The Cylindrical solid metallic tube-(1) is machined in such a way that a circular step is formed as shown in Fig.-1. Thus, the tube (1) is having a circular step. Further, a circular groove (3) is provided on one side of step- called outer end. An O-ring (7, Fig.-3) is fitted in the groove (3), wherein the O-ring is made of resilient material including rubber. The depth of the groove (3) is designed in such a way that, almost half of the O-ring (7) thickness is projected outside the groove (3).

[0038] Again, the cylindrical section (1) with circular step is made hollow throughout its length by machining. In the outer end of the cylindrical section (1), threads are provided to a certain length (4) so that at least two nuts can be tightened. The fibre-optic cables (6) as per requirement are cut and drawn through this hollow section, in such a way that sufficient length of the cables on both the ends should be equal or as per specific requirement.

[0039] Thereafter, a potting material (2) or glue is prepared by a mixture of Resin including CY-205 and Hardner including HY-951 in the ratio of for example 10:1. The cylindrical tube (1) with cables (6) is kept vertical while closing the lower end. The glue/ potting material (2) is then poured and allowed to air-dry for at least 3 to 4 hours. Utmost care is taken that no air-bubble is trapped inside the tube while pouring the glue/ potting material (2).

[0040] The materials given above are as example without restricting scope of the invention to the same. Thus, other materials readily apparent to a person skilled in the art are understood to be within purview of the invention.

TESTING:
[0041] After, completely drying the potting material/glue (2), the FEED-Through device of instant invention is subjected to following testing:
1. Light-signal test
2. Air/ Nitrogen pressure test
3. Thermal test

[0042] Light test is performed on each cable. A beam of light is sent from one end of cable and it should be seen at the corresponding end of cable. Thus, it is serially done for each Fibre-Optic cable. This is like a continuity test.

[0043] For Air/ Nitrogen pressure test, a special set up at 8-bar pressure level is rigged-up in order to check leakage of FEED-THROUGH device from potted section.

[0044] Thermal test is carried out at 90°C by heating the FEED-THROUGH assembly and also applying 8-bar pressure for about 48-hours continuously. No air-leakage should be observed.

[0045] After successfully testing, the ends of the fibre-optic cables (6) of FEED THROUGH device are put with insulating couplers (5) by fusion machine.

INSTALLATION OF THE INVENTION:

[0046] The present invention acts as an interface between fibr-bragg-grating (FBG) sensors installed in the turbo generator and outside monitoring system.

[0047] For installation of FEED-THROUGH device depending upon the space available, one simple hole is drilled on Turbine and Exciter End on the casing. The diameter of hole is for example 50mm without restricting scope of the invention to the same. The assembled FEED-THROUGH is inserted from inside the casing through the drilled hole so that outer end should come out of the casing. O-ring [7] is fixed in groove [3] provided. Two nuts are screwed one by one and tightened. The upper nut is locked. Thus, FEED-THROUGH device is remained bolted from outer end on the casing.

[0048] Each fibre-optic cable [6] is coupled with each sensor’s cable through coupler [5] from inside the casing. Corresponding end of the FEED-THROUGH fibre-cables [6] are then coupled with monitoring system’s cables.

ADVANTAGES OF INVENTION:

[0049] The advantage of the present invention is that it provides a direct arrangement for interfacing the sensors installed inside the generator to outside monitoring system. Since, invented FEED-THROUGH device requires Little space thus eliminating the restriction of large space and shape of prior art.

[0050] Another advantage of the present invention is that it provides leak-proof arrangement for interfacing the sensors installed inside the generator to outside monitoring system.

[0051] Another advantage of the present invention is that it provides an arrangement which can be operated at elevated temperature and pressure encountered during operation of a turbogenerator.

[0052] Further advantage of the present invention is that it provides an arrangement and associated method, wherein the sensors can be very easily coupled with the invented device.

[0053] Further advantage of the present invention is that it provides a simple device, economical method of interfacing the installed sensors inside the generator to outside monitoring system.

[0054] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0055] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[0056] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[0057] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[0058] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0059] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0060] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

WE CLAIM:

1. Feed-through device for interfacing of fibr-bragg-grating (FBG) sensors installed in the turbo generator to outside monitoring system comprising:
- a tube (1) accommodating Fibre-Optic cables (6) with couplers (5) on both ends, wherein the tube (1) is having a circular step with groove (3) for fixing O-ring (7) and a threaded section (4) for screwing lock/cap nuts (8).

2. The Feed-through device as claimed in claim 1, wherein the circular step with groove (3) is located at an intermediate position and the threaded section (4) is provided at one outer end of the tube (1).

3. The Feed-through device as claimed in claim 1 or 2, wherein the tube (1) includes metallic cylindrical tube (1) having centrally drilled hole housing the couplers (5) on each end of Fibre-optic cables (6) potted by potting material/glue (2) in the centrally drilled hole, which provide connections without loss of light signals emanating from sensors installed on the turbo-generator overhangs.

4. The FEED-THROUGH device as claimed in claims 1-3, wherein the tube (1) is made of metal including hardened, annealed mild chromium steel.

5. The FEED-THROUGH device as claimed in claims 1-4, wherein the couplers (5) are non-metallic and the O-ring (7) is made of resilient material including rubber.

6. The FEED-THROUGH device as claimed in claims 1-5, wherein the potting material (2) comprises resin-hardner mixture in the ratio of for example 10:1.