US 3860314 A
A terminal block adapter for connecting and disconnecting active current curcuits without danger of open circuiting current devices or loss of continuity to external devices.
Description (OCR text may contain errors)
United States Patent 11 1 Vandiveer et a1.
[ Jan. 14, 1975 CURRENT CIRCUIT TERMINAL BLOCK ADAPTER  Inventors: Paul R. Vandiveer, 312 N. 60th St.; Elbert Wayne Young, 1414 34th St., Apt. 124, both of Phoenix, Ariz. 85018  Filed: July 20, 1973 21 Appl. No.: 381,274
 U.S. Cl 339/18 R, 339/19, 339/198,
 Int. Cl H01r 9/00, H01r 29/00  Field of Search 339/17-19, 339/198, 176, 263, 272, 217, 269; 200/158;
 References Cited UNITED STATES PATENTS 2,145,744 1/1939 Whitney 339/198 R X 3,146,055 8/1964 Linn 339/198 P X 3,177,457 4/1965 Croghan 339/198 P X 3,417,192 12/1968 Elm 339/198 X 3,760,330 9/1973 Bennett et a1..... 339/18 R R1 1,397 1/1894 Sanche 339/269 X Primary ExaminerRoy D. Frazier Assistant Examiner-Terrell P. Lewis Attorney, Agent, or Firm-Cahill, Sutton & Thomas  ABSTRACT A terminal block adapter for connecting and disconnecting active current curcuits without danger of open circuiting current devices or loss of continuity to external devices.
4 Clainis, 4 Drawing Figures CURRENT CIRCUIT TERMINAL BLOCK ADAPTER sensing elements to current transformers, which appa- The present invention relates to terminal blocks, and 7 more particularly, to shunting devices for use in conjunction with current transformers.
In the field of electrical power transmission, means must be provided to reduce the magnitude of current flowing through the power lines. To a level that can be safely and economically handled by switchboard devices such as wattmeters, ammeters and protective relay equipment. By using current transformers, a relative current can be obtained whose magnitude is in the range of readily available equipment.
Usually the current transformers, whether driving an instrument or a relay, are permanently affixed to the power lines conveying electrical power to or from a sub-station. The leads from these current transformers are brought to a terminal block on a switchboard panel. The terminal block permits relatively easy connection or disconnection of the relays or instruments and their respective current transformers.
The nature of a current transformer is such that the leads thereof must always be in closed circuit. If the leads are open circuited, the voltage across the secondary winding will rapidly increase, possibly causing a breakdown of the insulation and destruction of the current transformer.
Various terminal blocks and devices have been developed in the past for use in power sub-stations. U.S. Pat. No. 2,125,256, discloses a detachable terminal board. Spring loaded elements are used to effect an electrical connection between an existing threaded stud and the post of the detachable terminal board. The
.spring loaded electrical contact engaging the threads of the stud, is an unexceptable engineering practice for several reasons. First, the surface contact between the spring and the ridges of the threads is very small. The small surface area will tend to provide a high current density with the attendant danger of burning and corrosion. Secondly, the amount of physical contact is primarily dependent upon the force exerted by the spring. As the resiliency of the spring will diminish over a period of time and be further degraded by high temperatures, the effectiveness of the electrical connection will be of a short term duration. U.S. Pat. No. 1,946,889, shows a terminal board having a shunting bar disposed thereacross. A coil spring extends upwardly from each of the bus bars of the terminal block generally in vertical alignment with the shorting bar. A connecting pin interconnects the shorting bar with one of the bus bars, whereby a plurality of connecting pins may be used to electrically interconnect two or more of the bus bars. Other U.S. Patents generally related to the present invention include, U.S. Pat. Nos. 2,129,524; 2,407,372; 2,756,399; 3,193,794; and 3,594,710.
It is therefore a primary object of the present invention to provide a terminal block adapter for current transformers, which adapter permits the shorting of the secondary winding of a current transformer prior to connection or disconnection of a current sensing element.
Another object of the present invention is to provide apparatus useable in conjunction with presently widely used terminal blocks to permit the shorting of two or more bus bars within the terminal block.
Yet another object of the present invention is to provide apparatus for assisting in the connection of current ratusissnnmtibl w thp x ziistin q p Still another object of the present invention is to i'o vide apparatus for preventing damage to current transformers when current sensing elements are switched from one current transformer source to another.
A further object of the present invention is to provide a low cost modification to existing terminalblocks, which modification permits the shorting of connected current transformers prior to the insertion or removal of current sensing elements.
A still further object of the present invention is to provide apparatus for shorting current transformers, which apparatus is adaptable to any one of the existing presently used terminal blocks.
A yet further object of the present invention is to provide a low cost terminal block specially adapted for use with current transformers.
These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds.
The present invention may be described with more clarity and specificity with reference to the following drawings, in which:
FIG. 1 illustrates a representative electrical power circuit incorporating the present invention.
FIG. 2 illustrates a cross-sectional view of the present invention.
FIG. 3 illustrates an end view of the present invention.
FIG. 4 illustrates an electrical post useable in conjunction with the present invention.
Referring to FIG. 1, there is shown a schematic diagragm of a monitoring circuit for a three phase power line 1. The power line 1 includes three individual lines A, B, and C, which individual lines are representative of the A, B, and C phases connected in a Y configuration. Current transformers are connected to each of the lines, the secondary windings of each being identified by numerals 2, 3 and 4. The current transformers 2, 3, and 4, are directly connected to terminal board 20 at terminals 21, 22, and 23 with the common ground being connected to terminal 24. A second set of terminals 25, 26, 27 and 28 are connected to terminals 21, 22, 23 and 24, respectively, by bus bars (not shown).
A second terminal board 30 includes a first set of terminals 31-34 connected to a second set of terminals 35-38, respectively, by means of a plurality of bus bars (not shown). Similarly, a third terminal block 40 includes a first set of terminals 41-44 connected to a second set of terminals 45-48, respectively, by means of a plurality of bus bars (not shown).
A relay 5, having terminals 5-1, and 5-2, is connected across terminals 25 and 35. Terminal 31 of terminal block 30 is connected to terminal 41 of terminal block 40. Another relay 8 having terminals 8-1, and 8-2, is connected across terminals 45 and 48 of terminal block 40 and is in series with relay 5. Terminal 48, is connected to the common ground of current transformers, via terminals 44, 34, 38, 28 and 24. From this description, it may be understood that relays 5 and 8 may be set to be responsive to a current change within phase A of power lines 1.
Terminal 6-1 of relay 6 is connected to one side of the secondary winding of current transformer 3 through terminals 26 and 22 of terminal block 20. Terminal 6-2 is connected to terminal 9-1 of relay 9 through terminals 36 and 32 in terminal block 30 and terminals 42 and 46 in terminal block 40. Terminal 9-2 of relay 9 is connected to the common ground of current transformers through terminals 48 and 44 in terminal block 40 terminals 34 and 38 in terminal block 30 and terminals 28 and 24 in terminal block 20. Again, it may be understood that relays 6 and 9 are connected in series and are intended to be responsive to any change in current through phase B of power lines 1.
Terminals 7-1 of relay 7 is connected to one side of the secondary winding of current transformer 4 through terminals 27 and 23 in terminal block 20. Terminals 7-2 of relay 7 is connected to terminal -1 of relay 10 through terminals 37, and 33 of terminal block 30 and terminals 43 and 47 of terminal block 40. Terminal 10-2 of relay 10 is connected to the common ground of current transformers through terminals 48 and 44 of terminal'block 40, terminals 34 and 38 of terminal block 30 and terminals 28 and 24 of terminal block 20. Thus, it may be understood that relays 7 and 10 are in series and are intended to be responsive to any current change within phase C of power lines 1.
In accordance with good engineering and maintenance practice, the relays at a sub-station must be periodically removed from the line and maintained and calibrated to insure their continued reliable operation. Alternatively, the relays may be replaced with ammeters of oth e r current responsive elements. As the power line 1 can not normally be de-energized for such operations, the relays and/or ammeters must be disconnected from or connected to an energized current transformer. The nature of current transformers is such that the voltage on the secondary winding will rapidly rise unless a current path is maintained across the secondary winding. The rapid voltage rise may cause failure of the secondary winding insulation resulting in total failure of the current transformer. Thus, it is mandatory that a current path be continously maintained across the secondary winding of the current transformer through a load or by short circuiting the secondary winding.
Referring again to FIG. 1, there is shown an electrical line 11 connected to terminal 21 of terminal block 20 and terminal 31 of terminal block 30. Line 11 shorts out relay 5 thus, relay 5 may be removed from the circuit after installation of line 11 without any danger of open circuiting the secondary winding of current transformer 2.
As will be described in more detail below, the configuration of the terminals of the terminal blocks of the present invention permits the insertion or deletion of shorting lines, such as line 11, without affecting the connections of the existing current sensitive devices placed across the secondary windings of the current transformers. Once the shorting lines have been installed, the current sensitive devices may be removed at will without affecting the electrical connections of the shorting lines.
Referring to FIG. 2, there is shown a cross-sectional view of terminal block 20. The terminal block 20 includes a base 49 having a plurality of walls 50 extending upwardly therefrom to define a plurality of channels 54, which channels are normal to the longitudinal axis of the base. A bus bar 51 is positioned at the bottom of each of these channels and is secured to the base by means of bolts 52 and washers 53. An electrical line may be connected to bus bar 51 by wrapping the electrical line about bolt 52 intermediate washer 53 and the bus bar. A good electrical connection can be effected by tightening bolt 52 to firmly squeeze the electrical line. A plate 55 may be disposed across each of channels 54 and secured to walls 50 by screws 56. The primary purpose of plate 55 is that of affording a place for noting the phase, voltage or electrical element connected to the bus bar within the respective channel. Base 49 may include relatively thick ends or the ends may be made more robust by the addition of end plates 57. The latter may be connected to one another by means of a bolt 58 extending through base 49.
An insulator bar 60 is secured atop end plates 57 and in general vertical alignment with one set of terminals of the terminal block. As shown in FIG. 3, insulator bar 60 is in general vertical alignment with terminals 21. Insulator bar 60 includes a plurality of threaded apertures 61, which apertures positionally conform to channels 54 and are in vertical alignment with a set of terminals (i.e., terminals 21, 22, 23 and 24 as shown in FIG. 1).
Referring particularly to FIG. 4 in conjunction with FIGS. 2 and 3, the adjustable terminals 59 of the present invention will be described in further detail. The adjustable terminal 59 includes a threaded post 63 formed of electrically conductive material and including a head 67 disposed at the upper end thereof. Lower end 68 may be flattened or concave to form a good electrical contact with bolt 52. Threaded post 63 mates with threaded aperture 62 of insulator board 60 to permit selective electrical contact between bolt 52 and the threaded post. A cap 64 having a threaded stud 65 extending therefrom mates with a threaded cavity 69 within the threaded post. Cap 64 may be of electrically non-conductive material and includes a washer 66 disposed at the lower end thereof. Cap 64 may be threaded into or out of threaded post 63 to position washer 66 toward or away from head 67.
Referring momentarily to the schematic shown in FIG. 1, the operation of the adjustable terminal 59 will be described in further detail. It will be assumed that relay 5 is to be temporarily removed from the line for maintena s p s Line 2-1 of the secondary winding of current transformer 2 is connected intermediate washer 53 and bus bar 51 and secured to the bus bar by bolt 52. Threaded post 63 is engaged with threaded aperture 62 and turned until it forms a firm electrical contact with the head of bolt 52. One end of line 11 is wrapped about threaded stud 65 and cap 64 is turned until the end of line 11 is securely disposed intermediate washer 66 and head 67. From this description, it may be understood that one end of line 11 is electrically connected to the bus bar intermediate terminals 21 and 25 of terminal block 20 without disrupting or opening the circuit from terminal block 20 to current transformer 2 or to terminal 5-1 of relay 5.
The other end of line 11 is similarly secured to terminal block 30 at terminal 31. For the reasons discussed above, the electrical continuity intermediate terminal 5-2 of relay 5 and terminal 31 of terminal block 30 are not affected by the addition of line 11 to terminal 31. Relay 5 may now be completely disconnected by removing the line to terminal 25 on terminal block 20 and the line to terminal 35 on terminal block 30 without opening the current transformer secondary circuit.
The above discussion has been primarily directed to the present invention as used in conjunction with the addition or removal of current sensing elements electrically connected to current transformers. It is to be understood, however, that the terminal block of the present invention may be expeditiously used for other purposes and in conjunction with other equipments. In example, the terminal block of the present invention may be used to obtain voltage or current readings across phases without disrupting any existing circuits. Or, the terminal block of the present invention may be used for ancillary measuring devices or power takeoffs.
While the principles of the invention have now been made clear in an illustrative embodiment, there will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, the elements, materials, and components, used in the practice of the invention which are particularly adapted for specific environments and operating requirements without departing from those principles.
1. In an electrical power monitoring and test system for electrical power lines including at least one terminal block for establishing electrical communication between the monitoring and testing apparatus and the power lines, the terminal block including a plurality of parallel channels extending transverse to the longitudinal axis of the terminal block, each of the channels having a set of first and a second electrical terminals disposed therein and a bus bar disposed within each channel for interconnecting each said set of first and second electrical terminals, the improvement comprising:
a. an insulator board extending across the terminal block, said insulator board including a plurality of threaded apertures, each of said apertures being in axial alignment with one of said first electrical terminals of each said set of terminals;
b. an electrically conducting threaded post threadedly engaging each of said threaded apertures, said post being rotatable into and out of electrical contact with the corresponding one of said first electrical terminals; and
c. electrical attachment means for securing an electrical conductor to said post; whereby, each of said posts may selectively electrically engage one of said first electrical terminals of said set of terminals to provide an electrical pick-off without affecting the electrical integrity of the electrical circuit connected to the corresponding one of said set of electrical terminals.
2. The improvement as set forth in claim 1 wherein said insulator board is rigidly secured to the ends of the terminal block.
3. The improvement as set forth in claim 2 wherein said attachment means comprises a. a capped threaded stud;
b. a threaded cavity disposed within said post for re- I ceiving said stud; and
c. retaining means connected to said stud for securing the electrical conductor to said post.
4. The improvement as set forth in claim 3 including an electrically insulated cap secured to said stud; whereby, said stud may be manually threaded into and out of said post without danger of electrical shock.