Abstract:
A plug for ease of alignment of a temperature probe or sensor inside a duct of a transformer winding is provided. The plug is shaped for secure placement into a duct or passage of a transformer winding without requiring any adhering material. The insertion of the plug into the duct or passage brings the temperature probe into contact with the desired point along the transformer winding being thermally monitored.

Description:
FIELD OF INVENTION 
       [0001]    The present application is directed to a plug for aligning a temperature sensor within a transformer coil winding. 
       BACKGROUND  
       [0002]    Transformers generate significant heat during operation. The temperature of the transformer windings may be monitored to control the operation of the transformer within a certain temperature range, as high operating temperatures are known to cause fault conditions in transformers. Temperature probes are typically used to monitor the temperature of transformer coil windings along predetermined points on the coil windings. Known methods of placing temperature probes within coil windings involve gluing or otherwise adhering the probes to the desired position along the coil winding to be monitored. 
       SUMMARY  
       [0003]    A plug for aligning a temperature tube in a transformer winding has a body having generally elliptical first and second end portions, respectively. The first end portion has a larger diameter than the second end portion and the first end portion gradually tapers over the length of the body to the second end portion. The body has a through-hole disposed therein and the through-hole extends from the first end portion to the second end portion. The body is adapted to engage with a temperature probe having a generally cylindrical shape. 
         [0004]    A method of positioning a temperature probe within a transformer winding, comprising:
       a. providing a plug having first and second ends, the second end having an outer diameter smaller than an outer diameter of the first end;   b. inserting a temperature probe into a through-hole of the plug so that the probe extends through and partially outside of the plug first and second ends; and   c. inserting the second end of the plug into a duct or passage of a transformer winding so that the temperature probe contacts the portion of the transformer winding to be monitored.       
 
         [0008]    A method for cooling a transformer, comprising:
       a. providing a temperature probe and plug;   b. inserting said temperature probe into said plug so that said probe extends through and partially outside of said plug;   c. inserting said plug into a duct or passage of a transformer winding so that said temperature probe contacts the portion of the transformer winding to be monitored;   d. electrically connecting said temperature probe to a voltage measuring device;   e. electrically connecting said voltage-measuring device to a temperature monitor; and   f. programming said temperature monitor so that fans are activated when a predetermined temperature threshold is reached.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    In the accompanying drawings, structural embodiments are illustrated that, together with the detailed description provided below, describe exemplary embodiments of a self-aligning temperature plug for a dry-type transformer. One of ordinary skill in the art will appreciate that a component may be designed as multiple components or that multiple components may be designed as a single component. 
           [0016]    Further, in the accompanying drawings and description that follow, like parts are indicated throughout the drawings and written description with the same reference numerals, respectively. The figures are not drawn to scale and the proportions of certain parts have been exaggerated for convenience of illustration. 
           [0017]      FIG. 1  is an isometric view of a self-aligning temperature plug embodied in accordance with the present invention; 
           [0018]      FIG. 2  is perspective view of the temperature plug inserted within a duct of a vacuum cast transformer coil winding; and 
           [0019]      FIG. 3  is a perspective view of the temperature plug inserted within a passage formed by at least one spacer in an open wound transformer coil winding. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    A plug  10  for aligning a temperature sensor in a coil winding  70  of a dry-type transformer is depicted in  FIG. 1 . The plug  10  may be used with a vacuum-cast coil, open wound coil or any other type of coil winding  70  suitable for the application. The plug  10  is formed from a room temperature vulcanizing (RTV) silicone rubber material and is adapted to receive a temperature tube  50  or probe as shown in  FIG. 2 . An exemplary RTV silicone rubber material utilized in forming the plug  10  is Silastic® RTV silicone rubber base used in conjunction with a Silastic® M-3 silicone rubber curing agent, available from Dow Corning Corporation of Midland, Mich. A finished plug  10  formed from the RTV silicone rubber material has a temperature withstand of 220 degrees Celsius during the operation of the transformer. 
         [0021]    The plug  10  is formed by pouring the RTV silicone rubber material into a two-piece mold having the desired shape to form the plug  10 . The curing agent is added and the RTV silicone rubber material is cured at room temperature for about four to about 24 hours. Alternatively, the mold containing the silicone rubber material and curing agent may be baked in an oven for about an hour at 100 degrees Celsius to hasten the curing process. 
         [0022]    The plug  10  has a body  30  and generally elliptical first and second end portions  20 ,  40 . The first end portion  20  has opposing sides upon which a flat portion  25  is disposed. The flat portion  25  begins at a top surface of the first end portion  20  and extends about 1.5 inches or about halfway along the body  30  of the plug  10 . 
         [0023]    The plug  10  is tapered from the first end portion  20  having an outer diameter of about 1.063 inches to the second end portion having an outer diameter of about 0.75 inches. A through-hole  35  extends through the body  30  from the first end portion  20  to the second end portion  40  of the plug  10 . The temperature tube  50 , when fully inserted in the plug  10 , extends completely through the through-hole  35 . The tube  50  also extends beyond the plug  10  first and second end portions  40 . The temperature tube  50  is formed from polytetrafluoroethylene, such as is sold under the trademark Teflon®. 
         [0024]    The plug  10  is adapted for insertion in a duct  54  or passage between windings or layers of windings formed from copper or aluminum sheet, wire, strips, or foils in a transformer coil  70 . The plug  10  may be inserted lengthwise or widthwise depending on the size and configuration of the duct  54  or passage  66 . The plug  10  is inserted in generally oblong duct  54  formed of a glass fiber-reinforced plastic (GFRP) tube or a passage  66  formed by one or more spacers  62 , the spacers  62  comprising long rods typically formed in a rod, dog-bone shape, or elliptical shape. In one embodiment, the ducts  54  and spacers are formed from a pultruded GFRP. 
         [0025]    The method for installing the plug  10  in a transformer coil winding  70  includes inserting the temperature tube into the through-hole  35  of the plug  10  so that a predetermined length of the temperature tube  50  is in contact with the portion of the transformer winding being measured. The temperature tube  50  is fully engaged with the plug  10  when the temperature tube  50  is passed through the through-hole  35  beginning at the first end portion  20  of the plug  10 , the tube  50  extends through the through-hole  35  completely, and when a majority of the temperature tube  50  extends outside of the second end portion  40  of the plug  10 . Installing the plug  10  in a transformer winding  70  involves placing the plug  10  into the duct  54 , passage  66 , or in between windings or layers of windings by hand or by using a tool, if necessary, to apply pressure to the first end portion  20  of the plug  10  and thereby seat the plug  10  within the duct  54 , passage  66 , or windings. 
         [0026]    Referring now to a low voltage coil  60  depicted in  FIG. 2 , the plug  10  having the temperature tube  50  fully seated in the through-hole  35 , is wedged into the duct  54  by hand, and may further be turned 90 degrees with respect to a horizontal axis of the duct  54  and depending on the configuration of the duct  54 . As the plug  10  is wedged into the duct  54  or passage, the tube  50  is brought into contact with the desired point for temperature measurement along the transformer winding  70 . 
         [0027]    The insertion depth of the plug  10  is about 3 to 4 inches below a top, outer surface  60  of the transformer winding  70 . The insertion depth of the temperature tube  50  once inserted into the plug  10  is from about 6 inches to about 7 inches as measured from a top, outer surface of the transformer winding  70 . It should be understood that the insertion depth for the plug  10  and temperature tube  50  may vary depending on the application, size of the coils, transformer output rating and desired measurement point along the length of the coil. 
         [0028]    Referring now to  FIG. 3 , a transformer core  80  surrounded by low voltage coil  70  is depicted having passages  66  formed by the at least one spacer  62 . In the same manner of installation as with the duct  54  installation, the plug  10  is wedged into the passage  66  by hand and may further be turned 90 degrees with respect to a horizontal axis of the passage and depending on the configuration of the passage  66 . The tapered contour of the plug  10  along the length of the plug  10  retains the plug in a snug fit inside a transformer coil winding  70 , duct  54 , or passage  66 . 
         [0029]    The plug  10  is typically used in a low voltage coil winding  70 , however, in certain embodiments the plug  10  is used with a high voltage coil winding. The high voltage coil winding may be concentrically mounted to, disposed around or otherwise surround the low voltage coil winding  70 . Alternatively, the high voltage coil winding may be located inside the low voltage coil winding  70  depending upon the transformer design and application. 
         [0030]    A cooling system for the transformer utilizes the plug  10  and temperature probe  50 . The plug  10  has the temperature probe  50  inserted inside the plug  10 . The temperature probe  50  is further attached or electrically connected to a voltage measuring device, such as a thermocouple. The voltage measuring device is further electrically connected to a temperature monitor. The voltage measuring device measures the voltage present in the desired location of the coil winding  70 , duct  54 , or passage  66 . The voltage measurement or reading is converted by the temperature monitor and used to cycle fans on and off that cool the transformer to a preset temperature or temperature range. Alternatively, fans may be activated when the temperature measurement or reading at a predetermined location along the transformer winding reaches or exceeds a temperature setting or threshold in the temperature monitor. 
         [0031]    The fans may be positioned at each phase of the transformer, below an outer surface at the bottom of each coil winding  70 , or above an outer surface at the top of each coil winding  70 . When the fans are positioned above each coil winding, the air is directed downward through into each coil winding  70 . When the fans are positioned below each coil winding  70 , the air generated by the fans is directed upward into each coil winding  70 . Alternatively, a transformer having a triangular-shaped core may have a single fan directed above or below one of the vertices of the triangular-shaped core, or a fan directing air into one of the vertices of the core from below or above the triangular-shaped core. 
         [0032]    While the present application illustrates various embodiments, and while these embodiments have been described in some detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative embodiments, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant&#39;s general inventive concept.