AU2016100323A4 - Compact secondary substation - Google Patents

Abstract

A Compact Secondary Substation (CSS) (200) comprises an enclosure (205) comprising a roof (210) and a floor (220), wherein the roof (210) and the floor (220) are substantially parallel to each other. The enclosure further comprises a first compartment (230) and a second compartment (240), separated by a partition wall (235) and provided between the roof (210) and the floor (220). The first compartment (230) houses a distribution transformer and the second compartment (240) houses a switchgear. The CSS includes a duct (250) attached to an end of the switchgear, wherein the duct (250) comprises a first angular wall (310) forming a first obtuse angle (260) with the roof (210) in clockwise direction, a second angular wall (320) forming a second obtuse angle (270) with the floor (220) in anticlockwise direction and two lateral walls (330) substantially perpendicular to each of the first angular wall (310) and the second angular wall (320), wherein each of the first angular wall (310) and the second angular wall (320) are extending from the switchgear up to the partition wall (235). The CSS further includes an opening (255) provided at the partition wall (235) and between the first angular wall (310) and the second angular wall (320). The duct (250) is configured to receive flue gases from the switchgear during an event of an electrical arc and guide the flue gases into the first compartment (230) through the opening (255). I'aJ OcN

Description

FIELD OF INVENTION [0001] The present invention relates generally to a Compact Secondary Substation (CSS) and more specifically to a CSS capable of safely handling an event of an internal arc. BACKGROUND OF THE INVENTION [0002] A CSS is an electrical apparatus which converts medium voltage power of an electrical power distribution system into low voltage power for public supply. A CSS comprises an enclosure (typically metal) divided into a plurality of compartments corresponding to a plurality of equipment. Such a design helps in isolation of faults occurring in an equipment form other equipment in other corresponding compartments. The plurality of equipment includes, but are not limited to, Medium Voltage (MV) switchgear, distribution transformers, Low Voltage (LV) switchboards, connectors and auxiliary equipment etc. [0003] The equipment comprised within the MV switchgear is generally insulated with air or an insulating gas (typically SF 6 ). Similarly equipment in other compartments may be insulated with air or the insulating gas. At the time of an electrical failure in any of the compartments, an internal arc may be generated. The internal arc may lead to heating of air (or the insulating gas) resulting in generation of flue gases. The generation of flue gases may further lead to overpressure in the compartment which may cause components of the equipment to be forcefully ejected into air. The release of flue gases or the forceful ejection of components pose a physical threat to the operators and the general public in proximity of the CSS. Thus it is essential for the CSS to be able to handle an event of the internal arc. [0004] One way of handling the event of the internal arc is to release the flue gases via a duct into the compartment housing the distribution transformer, where the flue 1 gases can expand and cool down. However, the duct may provide a backpressure which may further increase the overall pressure inside the compartment, causing damage to the enclosure. Moreover the heat from the flue gases may damage the equipment corresponding to the distribution transformer. Therefore there is a need for an improved CSS that is capable of safely handling the event of the internal arc. SUMMARY OF INVENTION [0005] An aspect of the present invention provides a Compact Secondary Substation (CSS). The CSS comprises an enclosure. The enclosure further comprises a roof and a floor, wherein the roof and the floor are substantially parallel to each other. The enclosure further comprises a first compartment and a second compartment, separated by a partition wall and provided between the roof and the floor, wherein the first compartment houses a distribution transformer and the second compartment houses a switchgear. [0006] The CSS further comprises a duct attached to an end of the switchgear, wherein the duct comprises a first angular wall forming a first obtuse angle with the roof in clockwise direction, a second angular wall forming a second obtuse angle with the floor in anticlockwise direction and two lateral walls substantially perpendicular to each of the first angular wall and the second angular wall, wherein each of the first angular wall and the second angular wall are extending from the switchgear up to the partition wall. The CSS also comprises an opening provided at the partition wall and between the first angular wall and the second angular wall. Wherein the duct is configured to receive flue gases from the switchgear during an event of an electrical arc and guide the flue gases into the first compartment through the opening. [0007] In accordance with the aspect, the opening may be bound by two substantially parallel plates provided at the partition wall. Further a cooling means configured to 2 receive heat from the flue gases may be provided at the opening. Further the cooling means may comprise a plurality of fins stacked substantially parallel to each other. Moreover the cooling means may be attached to the two lateral walls. BRIEF DESCRIPTION OF DRAWINGS [0008] The subject matter of the present invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in attached drawings in which: [0009] Fig. 1 is a side view of a Compact Secondary Substation (CSS), in accordance with prior art. [0010] Fig. 2 illustrates an exemplary CSS in accordance with various embodiments of the present invention; [0011] Fig. 3 is a perspective view of a duct for receiving flue gases, in accordance with various embodiments of the present invention; [0012] Fig. 4a is a perspective view of the duct along with a cooling means attached to the duct, in accordance with various embodiments of the present invention; [0013] Fig. 4b illustrates the cooling means comprising a plurality of fins stacked substantially parallel to each other, in accordance with various embodiments of the present invention. DETAILED DESCRIPTION [0014] In the following detailed description, reference is made to accompanying drawings that form a part hereof, and in which is shown by way of illustration 3 specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense. [0015] Fig. 1 illustrates a Compact Secondary Substation (CSS) 100 in accordance with prior art. The CSS 100 includes a switchgear compartment 110 containing a medium voltage switchgear filled with SF 6 gas. The switchgear compartment 110 also contains a plurality of cable boxes 120. Each cable box is for receiving incoming cables from a corresponding power source. The CSS also includes a transformer compartment 130, housing a distribution transformer. A duct 140 with two straight walls 150 has been attached to the switchgear and the plurality of cable boxes 120 within the CSS 100. When an electrical fault happens, an arc is generated in the switchgear compartment 110 leading to generation of flue gases. The flue gases are received by the duct 140 and guided to the transformer compartment 130 through an opening 160. The flow path 170 illustrates the flow of flue gases from the switchgear compartment 110 into the transformer compartment 130. [0016] However due to presence of the two straight walls 150, a major amount of the flue gases will be reflected back into switchgear compartment 110. The reflection of flue gases causes a high backpressure to be generated in the switchgear compartment 110. Moreover, a relatively small size of the opening 160 also contributes in generation of backpressure. The back pressure causes a condition of overpressure to develop in the switchgear compartment 110. The overpressure may cause a plurality of components in the switchgear compartment 110 to be forcefully ejected into air, posing physical threat to the personnel in switchgear compartment. Further the overpressure may cause damage to the switchgear compartment 110. Moreover 4 relatively smaller volume inside the duct 140 does not allow the gases to expand and cool down sufficiently. These issues have been addressed in the present invention. This is further elaborated in discussion of the subsequent figures. [0017] Fig. 2 illustrates an exemplary CSS 200 in accordance with various embodiments of the present invention. The CSS 200 comprises an enclosure 205 having a roof 210 and a floor 220. The enclosure 205 is be segregated into a first compartment 230 and a second compartment 240 provided between the roof 210 and the floor 220. The first compartment 230 and the second compartment 240 are separated by a partition wall 235. Additionally the first compartment 230 contains a distribution transformer and the second compartment 240 contains a switchgear. A duct 250 has been attached to the switchgear for receiving flue gases from the switchgear in an event of an internal arc during an electrical fault. [0018] Fig. 3 illustrates the duct 250 for receiving flue gases from the switchgear, in accordance with various embodiments of the present invention. The duct 250 includes a first angular wall 310 extending from the switchgear up to the partition wall 235. The first angular wall 310 has been oriented to form a first obtuse angle 260 with the roof 210 in clockwise direction. Additionally the duct 250 also includes a second angular wall 320 extending from the switchgear up to the partition wall 235. The second angular wall 320 has been oriented to form a second obtuse angle 270 with the floor 220 in anticlockwise direction. The duct 250 also includes two lateral walls 330, with each of the two lateral walls 330 being perpendicular to each of the first angular wall 310 and the second angular wall 320. An opening 255 has been provided at the partition wall 235, between the points 252 and 254 at which the first angular wall 310 and the second angular wall 320 meet the partition wall 235 respectively. [0019] The duct 250 receives the flue gases from the switchgear in the event of the internal arc and guides the flue gases into the first compartment 230 through the 5 opening 255. The flow path 280 illustrates the flow of flue gases from the second compartment 240 into the first compartment 230. In accordance with various embodiments, the duct 250 is bound by two substantially parallel plates 340, such that, one plate is provided at each of the first angular wall 310 and the second angular wall 320. Additionally, in accordance with various embodiments, two additional plates are provided at the two lateral walls, such that, the two additional plates are substantially perpendicular to each of the two substantially parallel plates 340. The two substantially parallel plates 340 (and the two additional plates) assist in guiding the flue gases into the first compartment 230. In accordance with various embodiments, a cooling means 400 is provided at the opening 255 for receiving heat from the flue gases while the flue gases are being guided into the first compartment 230. [0020] Fig. 4a illustrates the duct 250 with the cooling means 400 attached to the duct 250. In accordance with various embodiments, the cooling means 400 is attached to the two lateral walls 330. The attachment may be a non-removable attachment (for e.g., welding, brazing and soldering etc.) or a removable attachment by means of fasteners (for e.g., nut and bolts, screws and rivets etc.) [0021] Fig. 4b illustrates the cooling means 400 in accordance with various embodiments of the invention, including a plurality of fins 410 stacked substantially parallel to each other. The plurality of fins 410 are made up of a conducting material (for e.g., copper, aluminum etc.). In accordance with various embodiments, the plurality of fins 410 lose heat to the surrounding air by means of convection, or lose heat to a fluid channel by means of conduction. Further, in accordance with various embodiments, the cooling means 400 is a heat exchanger with a fluid (e.g., air, water, oil etc.) flowing through a plurality of tubes of conducting material (for e.g., copper, aluminum), the tubes being configured to receive heat from the flue gases. Additionally, in other embodiments, the cooling means 400 includes means of 6 introducing fresh air (for e.g., by means of a compressed air jet or by means of induction etc.) into the flue gases for reducing the temperature of the flue gases. [0022] The angular shape of the walls, as per the present invention, provide a larger initial volume for gases to expand and cool down, as compared to duct with straight walls of the prior art. Moreover the orientation of the angular walls avoid reflection of gases into a switchgear compartment, thus overcoming the condition of excessive overpressure inside the switchgear compartment. The duct (of the present invention) also allows for a greater opening area to be provided for release of flue gases. A cooling means provided at the opening substantially decreases the temperature of the flue gases before the flue gases are released into the transformer compartment, thus preventing the equipment in the transformer compartment from damage due to heated flue gases. 7

Claims (5)

1. A Compact Secondary Substation (CSS) , the CSS comprising: an enclosure comprising: a roof and a floor, wherein the roof and the floor are substantially parallel to each other; a first compartment and a second compartment, separated by a partition wall and provided between the roof and the floor, wherein the first compartment houses a distribution transformer and the second compartment houses a switchgear; a duct attached to an end of the switchgear, wherein the duct comprises a first angular wall forming a first obtuse angle with the roof in clockwise direction, a second angular wall forming a second obtuse angle with the floor in anticlockwise direction and two lateral walls substantially perpendicular to each of the first angular wall and the second angular wall, wherein each of the first angular wall and the second angular wall are extending from the switchgear up to the partition wall; and an opening provided at the partition wall and between the first angular wall and the second angular wall; wherein the duct is configured to receive flue gases from the switchgear during an event of an electrical arc and guide the flue gases into the first compartment through the opening.

2. The CSS as claimed in claim 1, wherein the opening is bound by two substantially parallel plates wherein one plate is provided at each of the first angular wall and the second angular wall. 8

3. The CSS as claimed in claim 1, wherein a cooling means configured to receive heat from the flue gases is provided at the opening.

4. The CSS as claimed in claim 3, wherein the cooling means comprises a plurality of fins stacked substantially parallel to each other.

5. The CSS as claimed in claim 3, wherein the cooling means is attached to the two lateral walls. 9