Description:TECHNICAL FIELD
[0001] The present disclosure, in general, relates to Optical Current Transformers. More particularly, the present disclosure relates to the construction of high voltage Optical Current Transformer and the guiding-cum-sealing arrangement for protecting the optical fiber of Optical Current Transformer (OCT) while using in EHV (extra-high voltage) and UHV (Ultra-high voltage) class substations. In addition, the present disclosure also includes the various components and modules developed for a “high voltage free-standing” OCT construction suitable for air-insulated substations (AIS).
BACKGROUND/PRIOR ART OF THE INVENTION
[0002] 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.
[0003] Current Transformers (CT) plays an important role in high voltage substations for metering of power and protection and control applications. Optical CTs are a new superior variant of the conventional magnetic core type CTs and offers considerable technical advantages. Major technical advantages of Optical CT over conventional CTs include high dynamic current sensing range with no saturation problem, no requirement of oil or paper insulation, can be used for both ac and dc application, high bandwidth, less weight, and compact size, etc. Optical CTs apart from metering and protection enables the implementation of digital process bus technology in HV substations which is required for the implementation of “Digital Substation”.
[0004] Optical Current Transformers (OCT) are non-conventional current transformers that use polarized light to deduce the precise magnitude of a current flowing in a primary conductor in high voltage substations. OCTs are a relatively new product for power transmission utilities, and their utilization in actual HV switchyards, for current sensing, has increased during the last one decade. Apart from various other technical advantages of OCTs, the simplified high voltage design/engineering of OCTs with no requirement of paper and oil insulation has interested the global power transmission utilities to adopt this fiber optic technology and OCT product in their substations.
[0005] As the OCTs are made up of optical components & fiber and it does not require any bulk insulation, they are considerably lighter in weight and compact in size, as compared to conventional magnetic core-based current transformers. But, even though the OCT does not require oil or paper insulation, designing them for high voltage installations is challenging, as the optical components and fiber used are very delicate and fragile. OCT requires a special/novel construction of high voltage components based on the configuration/mounting arrangement designed by the manufacturer. Broadly, various components of the Optical CTs are a) fiber optic sensing module at HV side, b) HV support insulation, shields, and other mechanical components and c) Opto-electronics unit installed at LV (ground) side.
[0006] Various inventions and patents cover the different optical techniques and technologies developed for optical current sensing. These techniques are based on a Faraday effect which is implemented using either a polarimetry or interferometry approach.
[0007] One of the prior art related to this field of technologies covers the invention of the Fiber Optic Current Sensor. This document discloses several methods of increasing the sensitivity of the in-line and Sagnac loop type current sensors. In the first aspect of this prior art, an optimally spun birefringent fiber is disclosed. This allows a circular state of polarization to be well maintained throughout a long length of bent fiber so that the number of turns of sensing fiber around the current-carrying wire can be increased to a large number.
[0008] The another prior art mentions the development of fiber optic current sensor with spun fiber and temperature compensation. This invention relates to fiber-optic current sensor with strongly birefringent spun fiber.
[0009] The another prior art describes a method and apparatus for measuring current in a high voltage (HV) current carrier and generates a low voltage signal proportional to the current in the HV carrier and applies this signal to an integrated-optic voltage sensor located in the HV environment adjacent to the HV current carrier to produce a modulated optical signal representative of the current being measured.
[0010] Most of the patents cover the manufacturing of a fiber embedded in an insulator for different applications. The another prior art mentions the invention of optical fiber built-in type composite insulator and a method of producing the same. This prior art relates to the optical fiber embedded insulator which is mainly used in detection systems for finding fault points at electric power transmission lines and substations.
[0011] The another prior art relates to this field of invention provides an electrical insulator equipped with optical fibers inside and is used to serve as an insulating support member for an outdoor high voltage installation.
[0012] The another prior art refers to the invention of embeddable fiber optic connector and associated method. The application covered under the patent is fiber optic sensors used to measure structural conditions in structural parts viz. strain, temperature, pressure, acceleration, etc.
[0013] Yet another prior arts mention the development of composite electrical insulator including an electrical optical fiber sensor. The integrated sensor measures the stresses of mechanical and thermal origin acting on the insulator while it is in operation. It is constituted by an optical fiber having a Bragg grating implanted on it.
[0014] None of the cited prior arts focusses on the complete construction of high voltage Optical Current Transformer and the technique of protecting the optical fiber of high voltage Optical Current Transformer.
[0015] The present disclosure provides the complete construction of high voltage Optical Current Transformer and the optical fiber guiding-cum-sealing arrangement for protecting the Optical Current Transformer (OCT) while using in EHV (extra-high voltage) and UHV (Ultra-high voltage) class substations.
OBJECTS OF THE DISCLOSURE
[0016] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0017] An object of the present disclosure is to provide a high voltage optical current transformer and a guiding and sealing arrangement for the same, which serves the purpose effectively.
[0018] It is a general or primary object of the present disclosure to provide the complete construction of a high voltage Optical Current Transformer.
[0019] It is another object of the present disclosure to develop a bottom support structure for the free standing design of OCT.
[0020] It is yet another object of the present disclosure to provide the optical fiber guiding-cum-sealing arrangement for protecting the Optical Current Transformer (OCT) while using in EHV (extra-high voltage) and UHV (Ultra-high voltage) class substations.
[0021] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
SUMMARY OF THE INVENTION
[0022] This summary is provided to introduce concepts related to the construction of the high voltage Optical Current Transformer. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor it is intended to be used to limit the scope of the claimed subject matter.
[0023] In an embodiment, the present disclosure provides a high Voltage optical Current transformer comprising an insulator, a high voltage side module connected to the top end of the insulator, a low voltage side module connected to the bottom end of the insulator, a fiber embedded inside the insulator that built up the connection between the high voltage submodule and the low voltage submodule, and free-standing support modules, wherein the free-standing supporting module further store the fiber and route it out of the Optical CT for further connection.
[0024] In an aspect, the present disclosure provides the high Voltage optical Current transformer in which the said high voltage side module comprising an HV flange fixed on the top end of the insulator, a sensor head supported on the HV flange, a conductor mounted over the HV flange through two supports, at least two detachable corona ribs attached on both sides of the HV flange in a downward direction, and one corona ring provided at the base of the HV side module, wherein the corona ring along with the detachable corona ribs are attached to the HV flange through an arrangement.
[0025] In an aspect, the present disclosure provides the high Voltage optical Current transformer in which the said low voltage side module comprising an LV flange sealing the bottom end of the insulator, a plurality of guide connected to the LV flange for bolting the flange to the insulator during assembly, at least two detachable corona ribs attached on both sides of the LV flange in an upward direction and one corona ring provided at the top of the LV side module, wherein the corona ring along with the detachable corona ribs are attached to the LV flange through an arrangement.
[0026] In an aspect the present disclosure provides the high Voltage optical Current transformer in which the free-standing support module comprising a support flange on which the LV flange connected to the insulator is mounted, a seal 1 provided between the LV flange and the support flange, a bolting plate is provided at the bottom of the free-standing support module, at least four stiffeners are provided at top and bottom of the free-standing support module, wherein the first ends of the top stiffener are connected to the support flange plate and the bottom ends of the top stiffener are connected at the middle side plates of the free-standing support module, wherein first ends of the bottom stiffener are connected to the bolting plate and the bottom ends of the bottom stiffener are connected at the side plates of the free-standing support module, a fiber holder is provided to support the fiber coming out of the LV flange, and a fiber exit is provided to the back plate of free-standing support module for routing the fiber out of OCT.
[0027] In an embodiment, the present disclosure provides a guiding and sealing arrangement for optical CT at HV module comprising a sensor head welded at the top of the HV flange providing the robust top side hermitic sealing, seal 1 provided at the mid of the HV flange, a seal 2 provided at the mid of the HV flange below the seal 1,and a seal 3 provided at both the sides of the bottom end of the HV flange to seal the interface between the insulator and the sensor head.
[0028] In an aspect, the present disclosure provides the guiding and sealing arrangement in which the said sensor head comprises various optical components and delicate optical fiber.
[0029] In an aspect, the present disclosure provides the guiding and sealing arrangement in which seal 1 is implemented by a silicone-based sealant.
[0030] In an aspect, the present disclosure provides the guiding and sealing arrangement in which seal 2 is implemented by a resin epoxy-based sealant.
[0031] In an embodiment, the present disclosure provides a guiding and sealing arrangement of optical CT at LV module comprising an adapter plug mounted on the LV flange through screws, a seal 1 is provided on both the sides of the LV flange for providing the connection between the adapter plug and the LV flange, a seal 2 is provided on both the extreme sides of the LV flange for sealing the interface between the LV flange and the insulator, a seal 3 and a seal 5 for hermetically sealing the adapter plug over the LV flange; a seal 4 is provided to hold and hermetically seal the fiber in the adapter plug, and a gas coupling port is provided to fill nitrogen gas inside the insulator.
[0032] 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.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0033] 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 methods that are consistent with the subject matter as claimed herein, wherein:
[0034] Figure 1 illustrates the General Construction of OCT with various modules and components.
[0035] Figure 2 illustrates the OCT HV side construction of modules.
[0036] Figure 3 illustrates the OCT LV side construction of modules.
[0037] Figure 4 illustrates the OCT base support for enabling free-standing design in HV substations.
[0038] Figure 5 illustrates the guiding and sealing arrangement at the HV end of OCT.
[0039] Figure 6 illustrates the guiding and sealing arrangement at the LV end of OCT.
DETAILED DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
[0040] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0041] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0042] Generally, the Optical Current transformers are a type of non-conventional instrument transformers that uses light to precisely measure the current flowing in a conductor. They are generally used in high voltage substations for metering and protection applications. Mainly, the delicate optical fibers and optical components are used in Optical CTs at high voltage side in any climatic condition. But, due to extremely harsh substation environment, the high voltage design and optical fiber guiding and sealing construction is critical for 365 days X 24 Hours operation of the optical CT in the switchyard.
[0043] The present disclosure provides the HV construction of various components and fiber guiding-cum-sealing arrangement in Optical CT. The proposed HV components and the solutions offered in the present disclosure can be used to manufacture and assemble a high voltage optical CT with modular freestanding construction suitable for any voltage class substation.
[0044] Figure 1 shows the construction of free-standing OCT and various modules. The HV side modules [01] are always maintained at high voltage as they are connected to a high voltage conductor/transmission line in an HV substation. To support the HV side modules of Optical CT an insulator [05] is used. The insulator [05] provides the required arcing distance as per the substation voltage class and the electrical creepage as per the requirement. The output fiber [04] from HV side modules [01] is routed and guided through the insulator [05].
[0045] The LV side modules [02] receives the fiber [04] and guides it out of the insulator [05]. The construction of the HV side modules [01] and LV side modules [02] is such that they ensure optimum sealing of the delicate fiber [04] inside the insulator [05]. The HV side modules [01] and LV side modules [02] are also used to optimize the distribution of electric field lines produced due to the high voltage connection. A free-standing support modules [03] are designed to support/mount the HV side modules [01], LV side modules [02], and insulator [05] with fiber [04] in a substation. The free-standing support modules [03] have the provision to store the fiber [04] and route it out of the Optical CT for further connection to its opto-electronics unit.
[0046] Figure 2 depicts the proposed HV side modules [01] and components of Optical CT. The HV flange [09] supports the sensor head [06] through direct welding which provides good strength and leak-proof construction. The HV flange [09] has the provision to be fixed on the insulator [05]. The conductor [07] is used for connection to the sub-station primary HV conductor for measuring the current flowing. For mounting of the conductor [07], two supports [08] are used. The material of the support [08] is Stainless Steel (SS-304) to meet the required strength to withstand the “short circuit forces” which are expected during any fault condition in sub-station.
[0047] The corona ring [11] is designed to reduce the corona discharge generated due to the high voltage connection. For mounting of the corona ring [11], detachable corona ribs [10] are developed. The corona ring [11] and the corona rib [10] assembly is mounted to the HV flange [09] using an arrangement. The overall arrangement is implemented in such a way that various components of the HV side modules of the optical CT can be installed and dismantled easily. This makes the erection of optical CTs at the site quite easy with the less required effort.
[0048] Figure 3 depicts the LV side modules [02] and components of Optical CT. The LV Flange [13] is made of lightweight metallic material that is designed to seal the insulator [05] at the bottom LV side. The corona ribs [10] are fastened to the LV flange [13] using appropriate hardware. The Corona ring [11] is designed to optimize the electric field line distribution and is connected using the corona ribs [10]. The guide [12] connected to the LV flange [13] are used to bolt the flange to the insulator [05] during assembly. This helps in easy handling and protecting the delicate fiber [04] during assembly of Optical CT.
[0049] Figure 4 shows the OCT base support module [03] for free-standing design in HV substations. This module supports the Optical CTs insulator [05] along with the HV and LV side modules. The LV Flange [13] which is connected to the insulator [05] is mounted on the support flange [24] using suitable hardware. There is a sealing arrangement implemented using seal 1 [29] between the LV flange [13] and the support flange [24] for preventing any moisture ingress inside the support module. The support module carries the total weight of the Optical CT along with the weight of clamps and connectors connected at the HV side for installing in HV substations. To provide optimum strength to these modules, stiffeners [25] are welded inside the support enclosure. The fiber [04] which comes out of the LV flange is supported using a fiber holder [26] arrangement implemented inside the base support module. Fiber [04] is routed to the installed opto-electronics unit at the ground side, through the fiber exit [28] port provided at the backside of the base support module. A bolting plate [27] is provided at the bottom side of the base support. This bolting plate is used to mount the OCT on the support structures provide at the switchyard.
[0050] Figure 5 shows the guiding and sealing arrangement of Optical CT on the HV side. The sensor head [06] welded to the top flange provides the robust top side hermitic seal design. This arrangement is mounted on top of the insulator [05]. The sensor head [06] consists of various optical components and delicate optical fiber [04]. The fiber [04] comes out of seal 1 [14] and seal 2 [15] into the insulator [05].
[0051] Both these seals provide hermetic sealing and are implemented in such a way that the delicate fiber is not damaged due to the seals. Seal 1 [14] is implemented by using silicone-based sealant and seal 2 [15] is implemented using resin epoxy-based sealant. Both these seals have been tested under various simulated climatic/temperature conditions and their performance is found excellent. Seal 3 [16] is provided to seal the interface between the insulator [05] and the sensor head [06].
[0052] Figure 6 shows the guiding and sealing arrangement of Optical CT on the LV side. The developed LV flange [13] is used for a) Sealing Optical CT insulator [05] at LV side b) Fiber [04] optic patch cord feed-through arrangement c) Mounting of corona ribs [10] and corona ring [11] d) Installing the gas coupling port [23]. The adapter plug [17] is made of lightweight metallic material and is used to guide the fiber [04] out of the insulator [05] from the LV side of Optical CT. The adapter plug [17] is filled with resin epoxy seal 4 [21] to hold and hermetically seal the fiber [04]. The adapter plug [17] is pushed against seal 3 [20] and seal 5 [22] to have a firm hermetic sealing.
[0053] Two seals are used here to have a redundancy in case one of the seals fails. Further, the adapter plug [17] has a provision to securely mount it on the LV flange [13] using screws. Seal 1[18] is designed between the adapter plug [17] and the LV flange [13]. A gas coupling port [23] is used to fill nitrogen gas inside the insulator [05] to maintain positive pressure and an inert atmosphere. Seal 2[19] is used for sealing the interface between the LV flange [13] and the insulator [05].
[0054] Thus, with the construction and the guiding and sealing arrangement of Optical CT described in the present disclosure, various technical problems of the state of the art are resolved. Also, although a number of exemplary method options are described herein, those skilled in the art can appreciate that the construction of high voltage Optical Current Transformer and the guiding-cum-sealing arrangement for the Optical Current Transformer (OCT) while using in EHV (extra-high voltage) and UHV (Ultra-high voltage) class substations, without deviating from the scope of the subject matter of the present disclosure.
[0055] Further, it will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.
[0056] Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.
[0057] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

Claims:1. A high Voltage optical Current transformer comprising
an insulator [05];
a high voltage side module [01] connected to the top end of the insulator [05];
a low voltage side module [02] connected to the bottom end of the insulator [05];
a fiber [04] embedded inside the insulator [05] that builds up the connection between the high voltage sub-module [01] and the low voltage sub-module [02]; and
a free-standing support module [03], wherein the free-standing supporting modules [03] store the fiber [04] and route it out of the Optical CT for connection.
2. The high Voltage optical Current transformer as claimed in claim 1, wherein the said high voltage side module [01] comprising
an HV flange [09] placed on the top end of the insulator [05];
a sensor head [06] supported on the HV flange [09];
a conductor [07] mounted over the HV flange [09] through two supports [08];
at least two detachable corona ribs [10] attached on both sides of the HV flange in a downward direction; and
one corona ring [11] provided at the base of the HV side module [01], wherein the corona ring [11] along with the detachable corona ribs [10] are attached to the HV flange through an arrangement.
3. The high Voltage optical Current transformer as claimed in claims 1-2, wherein the said low voltage side module [02] comprising
an LV flange [13] sealing the bottom end of the insulator;
a plurality of guide [12] connected to the LV flange [13] for fastening the flange to the insulator [05] during assembly;
at least two detachable corona ribs [10] attached on both sides of the LV flange in an upward direction; and
one corona ring [11] provided at the top of the LV side module [02], wherein the corona ring [11] along with the detachable corona ribs [10] are attached to the LV flange through an arrangement.
4. The high Voltage optical Current transformer as claimed in claims 1-3, wherein the free-standing support module [03] comprising
a support flange [24] on which the LV flange [13] connected to the insulator [05] is mounted;
a seal 1 [29] provided between the LV flange [13] and the support flange [24];
a bolting plate [27] is provided at the bottom of the free-standing support module [03];
at least four stiffeners are provided at the top and bottom of the free-standing support module [03], wherein the first ends of the top stiffener are connected to the support flange [24] plate and the bottom ends of the top stiffener are connected at the side plates of the free-standing support module [03], wherein first ends of the bottom stiffener are connected to the bolting plate [27] and the bottom ends of the bottom stiffener are connected at the middle side plates of the free-standing support module [03];
a fiber holder [26] is provided to support the fiber coming out of the LV flange [13]; and
a fiber exit is provided to a parting of the fiber coming out of the LV flange [13].
5. A guiding and sealing arrangement of optical CT at HV module [01] comprising
a sensor head [06] welded at the top of the HV flange [09] providing the top side hermitic seal construction;
a seal 1 [14] provided at the mid of the HV flange [09];
a seal 2 [15] provided at the mid of the HV flange [09] below the seal 1[14]; and
a seal 3 [16] provided at both the sides of the bottom end of the HV flange [09] to seal the interface between the insulator [05] and the sensor head [06].
6. The guiding and sealing arrangement as claimed in claim 5, wherein the said sensor head includes optical components and delicate optical fiber [04].
7. The guiding and sealing arrangement as claimed in claims 5-6, wherein the seal 1 [14] is implemented by silicone-based sealant.
8. The guiding and sealing arrangement as claimed in claims 5-7, wherein the seal 2[15] is implemented by resin epoxy-based sealant.
9. A guiding and sealing arrangement of optical CT at LV module [02] comprising
an adapter plug [17] mounted on the LV flange [13] through fasteners;
a seal 1[18] is provided on both the sides of the LV flange for providing the connection between the adapter plug [17] and the LV flange [13];
a seal 2 [19] is provided on both the extreme sides of the LV flange for sealing the interface between the LV flange [13] and the insulator [05];
a seal 3 [20] and a seal 5[22] for hermetically sealing the adapter plug over the LV flange;
a seal 4 [21] is provided to hold and hermetically seal the fiber [04]; and
a gas coupling port is provided to fill nitrogen gas inside the insulator [05].