Description:TECHNICAL FIELD
[0001] The present disclosure, in general, relates to a safety equipment. More particularly, this invention relates to a protective device for an electrical equipment or a transformer to limit the effects of blasting due to pressure building inside the oil type current transformer.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention.
[0003] Electric power is the most common form of energy that can be generated, transmitted and utilized for different segments of Society. Power after generation has to be transmitted to the users through many sub-stations. It is important to protect the different equipment that are associated with power transmission against different types of fault. During fault conditions, the voltage and current of the transmission system becomes unstable (transient) and can reach a value higher than the rated values of the system. These faults normally appear for a very short time before the protection system gets activated and the equipment are isolated. However, sometimes these short time over voltage and current can make the system unstable and damage the equipment and cause damages to the other equipment in the neighborhood. On such events, it is important to protect the equipment from damaging even at the cost of isolating the equipment.
[0004] A current transformer is connected in series with the sub-station equipment (transformer) at the input and output terminals as shown in figure 1. The sole objective is the current transformer sense the current in the power transmission line and generate appropriate signals for metering and protection. A current transformer (CT) is not designed to sense the voltage. But it will be subjected to the voltage appearing on the line. A Voltage transformer (VT) is connected between the line and ground. The very basic purpose is to sense the voltage of the transmission lines of the sub-station.
[0005] Technical problem: During system disturbance, the voltage of the transmission line becomes unstable. It could be very high, it could be fluctuating (increase and decrease very quickly); then the insulation provided in the current transformer and Voltage transformer gets more stressed. The stressed insulation will give rise to different types of abnormalities in the form of discharges, arc, spark inside the CT and VT which is fully submerged in oil. These abnormalities will generate heat and gas inside the current transformer and that will increase the pressure inside. With increase in pressure inside the insulator housing of the CT / VT could break / blast.
[0006] The breakage endangers the power flow, since it will break the line conductor connected to the system equipment (Transformer) . This activity results in a high sudden stress on the connected power equipment leading to damage of the CT /VT and their insulator. The insulator is basically porcelain material. When it breaks under blasting condition, fragmented pieces of porcelain are thrown off in different direction at a very high speed randomly and could damage the other equipment in its vicinity and may even harm people working around. The breakage of the insulation will cause gushing out of hot oil inside the CT/VT. The oil splash owing to breakage of housing insulator of the CT/VT in the sub-station could burn the other equipments as well as man power nearby, thus endanger the surroundings. If the hot oil falls on any electrically charged conductor like capacitor, cables, wirings, bushing terminals or live conductor of the transmission line, it could cause fire incident which will be causing to catastrophic damage to the sub-station.
[0007] Technical Solution: Accordingly, there is a need to reduce the effect of the failure of Current Transformer and Voltage Transformer in the event of any abnormal situation.
OBJECTS OF THE DISCLOSURE
[0008] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0009] It is a general object of the present disclosure is to reduce the effect of blasting of CT/VT and protect other healthy equipments installed nearby.
[0010] It is another object of the present disclosure is to provide a way of creating a safe working environment inside the sub-station.
[0011] It is another object of the present disclosure is to provide a device for reducing the occurrence of fire hazard in the substation due to the hot oil resulting from blasting of CT/VT.
[0012] 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
[0013] This summary is provided to introduce concepts related to provide protection to current transformers and voltage transformers which are regularly used in electric sub-stations for power generation and transmission. 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 is it intended to be used to limit the scope of the claimed subject matter.
[0014] In an embodiment, the present disclosure relates to a protection device for a power transformer of a substation, comprising of a plurality current transformers of three phases present between the power transformer and the transmission line having a plurality of primary and secondary windings, a plurality voltage transformers of three-phases connected between the three phase line and the ground having a plurality of primary and secondary windings, an insulation provided between the plurality of primary and secondary windings existing in the current transformer and the voltage transformer and is a jacket to cover the periphery of the electrical equipment that is wrapped around the insulation within a safe insulating radial gap.
[0015] In an aspect, the Current Transformer and power transformer are connected in series with the incoming and outgoing transmission line.
[0016] In an aspect, the primary winding of the Current Transformer runs through the inner diameter of the ring core of the current transformer.
[0017] In an aspect, one end of the secondary winding of the Voltage Transformer is connected to the transmission line and the other end is connected to the ground.
[0018] In an aspect, wherein the insulation consists of large number of composite layers of cellulose paper wound over each other covering the current transformer.
[0019] In aspect, the jacket is made of FRP (Fiber Reinforced Plastic) material.
[0020] In aspect, at least one jacket is located onto at least one transformer of one phase.
[0021] 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.
[0022] 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.
[0023] 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 DRAWINGS
[0024] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0025] FIG. 1 illustrate the toroidal ring core of current transformer.
[0026] FIG. 2 illustrates the mounting arrangement of the jacket around insulation.
[0027] FIG. 3 illustrates the transformer assembled with jacket around Insulation
[0028] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter.
DETAILED DESCRIPTION
[0029] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein 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 scope of the present disclosure as defined by the appended claims.
[0030] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0032] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0033] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0034] The present invention relates to a device of protecting the electrical equipment of a substation. The electrical equipment comprises of a current transformer with a primary and secondary winding, a voltage transformer with a primary and secondary winding, an insulation provided between the primary and secondary winding and a protection device which is a jacket to cover the whole electrical equipment around its circumference and is specifically wrapped around an insulator.
[0035] Referring to Fig. 1 and 2, current transformers (CT) are provided in a sub-station before and after the power transformer and are connected to each phase of the transformers. Therefore, each transformer has 6 current transformers and 6 voltage transformers. Current transformer is located between the equipment (transformer) and the transmission line. They are connected in series with the incoming and outgoing transmission line. The primary current transformer sees a voltage corresponding to the potential of the transmission line (33 kV or 66 kV or 132 kV or 220 kV or 400 kV or even higher).
[0036] The primary winding of the current transformer (connected to the transmission line) runs through the inner diameter of the ring core of the CT. The ring core is made of silicon steel rolled into a toroidal ring form. The ring core develops magnetization owing to the running of the primary line conductor of the current transformer through it.
[0037] The voltage transformers (VT) are connected between the transmission line and the ground. The high voltage is the primary winding of VT that is connected to the transmission line (33 kV or 66 kV or 132 kV or 220 kV or 400 kV or even higher). The other end of the high voltage winding is at ground potential. There is also a secondary low voltage winding in which low voltage is developed on the principle of voltage transfer of CVT (Capacitive Voltage Transformer) or EMVT (Electro Magnetic Voltage Transformer).
[0038] In both the cases of CT and VT, there exists a large potential (voltage) difference between two or more points owing to their voltage levels. High volume of insulation is provided between the high voltage locations and low voltage locations. The primary and secondary windings which also have a very large potential difference between them are also to be isolated electrically by virtue of the insulation 201 between them.
[0039] Referring to Fig. 2, the insulation 201 comprises of large number of composite layers of cellulose paper wound over each other covering the CT primary conductor and also the core of the current transformer.
[0040] Referring to Fig. 2 and 3, a jacket 202 is provided around the periphery of the equipment. The jacket 202 restricts the oil gushing out randomly from the CT/VT in the event of Blasting. The jacket 202 also prevents the fragmented pieces of porcelain insulator to be thrown out.
[0041] Therefore, by providing the jacket 202 around the equipment (CT / VT), the damaging effects of the equipment are restricted thereby enhancing safety and protection to human as well as other machinery in the vicinity of the equipment (CT/VT). The jacket 202 is to be placed above the base of the tank, around the insulation 201 keeping a radial gap around the insulator 201. So, in the event of bursting of the insulator 201, the oil and pieces of the insulator 201 get restricted into the jacket 202 and not go out of the jacket 202.
[0042] Moreover, the dust and populating particle that normally settle over the insulation 201 (by virtue of wind flow) and effect the surface resistance of insulation 201 which reduces effecting voltage distribution pattern across insulation 201 during normal working. This voltage distribution pattern over the surface of the insulator gets improved by virtue of jacketing around the insulation 201.
[0043] The jacket 202 is weather resistant and also provides adequate mechanical strength to carry out long life service. It is made up of Fiber Reinforced Plastic material. The jackets 202 of 3 different phases can also be painted in 3 different colors for easy identification and demarcation.
[0044] With the present device and method for providing protection over an electrical equipment, the following technical advantages are obtained.
[0045] The jacket helps in restricting the oil gushing out from the CT/VT in the event of Blasting.
[0046] The device makes the sub-station safe while working and monitoring.
[0047] The device removes un-wanted risk of injury to human during maintenance.
[0048] The device reduces the occurrence of fire hazard caused by hot oil from blasting of CT/VT.
[0049] This arrangement improves the voltage distribution pattern over the surface of the insulator of the CT/VT
[0050] 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:We claim:
1. A protection device for a power transformer of a substation, comprising of:
a plurality current transformer of three-phases located between the power transformer and the transmission line having a plurality of primary and secondary windings;
a plurality voltage transformers of three-phases connected between the line and the ground having a plurality of placement before and after the primary and secondary windings;
an insulation 201 provided between the plurality of primary and secondary windings existing in the current transformer and the voltage transformer,
characterized in that
the protection device is a jacket 202 covering the periphery of the electrical equipment that is wrapped around the insulation 201 within a radial open air gap.
2. The protection device as claimed in claim 1, wherein the current transformer and power transformer are connected in series with the incoming and outgoing transmission line.
3. The protection device as claimed in claim 1, wherein the primary winding of the current transformer runs through the inner diameter of the ring core of the current transformer.
4. The protection device as claimed in claim 1, wherein one end of the secondary winding of the voltage transformer is connected to the transmission line and the other end is connected to the ground.
5. The protection device as claimed in claim 1, wherein the insulation 201 consists of large number of composite layers of cellulose paper wound over each other covering the current transformer.
6. The protection device as claimed in claim 1, wherein the jacket 202 is preferably made of FRP (Fiber Reinforced Plastic) material.
7. The protection device as claimed in claim 1, wherein at least one jacket is located onto Current Transformer of one phase