Resistance insertion type circuit-breaker

A high-voltage circuit-breaker comprises a first insulative support column carrying a first current terminal and a pivoting cut-off arm provided with a first contact. An insulative column rotates to maneuver the cut-off arm. A second insulative support column carries a second current terminal and a jaw-type second contact cooperating with the first contact when the circuit-breaker is closed. The pivoting arm rotates about its axis through 90.degree. at the start of an opening maneuver or at the end of a closing maneuver to close the jaw on opening the circuit-breaker and to open the jaw on closing the circuit-breaker. The cut-off arm is extended by a cylindrical assembly containing a resistance and comprising a metal exterior tubular portion connected electrically to the resistance. The tubular portion comes into contact at the end of a circuit-breaker closing maneuver or at the beginning of a circuit-breaker opening maneuver with two pole horns mechanically attached to the second column and electrically connected to the second current terminal. The resistance is then inserted into the circuit of the circuit-breaker via the pole horns and the tubular portion. The resistance is short-circuited when the cut-off arm has rotated 90.degree. therefor about its axis at the end of the closing maneuver.

BACKGROUND OF THE INVENTION 
1 Field of the invention 
The present invention concerns a high-voltage circuit-breaker of the type 
in which a resistance is inserted when the circuit-breaker is closed. 
2. Description of the prior art 
Closing a circuit-breaker produces an inductive or capacitive current in 
the form of an arc which is struck between the mobile contact (blade) and 
the fixed contact (jaw) of the circuit-breaker and which can cause 
relatively serious equipment damage. The same phenomenon occurs when the 
circuit-breaker is closed, except that the current is lower. 
One object of the invention is to provide a mechanism in which, on opening 
or at the end of closing the circuit-breaker, the current is diverted into 
a circuit including a resistance whose function is to reduce the current 
and to dissipate the energy it produces. This mechanism prevents 
destruction of the contact members of the circuit-breaker. 
Another object of the present invention is to provide a reliable and rugged 
insertion mechanism that is easy to maintain, has a moderate unit cost and 
can dissipate large amounts of energy whilst protecting the contact 
members. 
SUMMARY OF THE INVENTION 
The present invention consists in a high-voltage circuit-breaker comprising 
a first insulative support column carrying a first current terminal and a 
pivoting cut-off arm provided with a first contact, an insulative column 
which rotates to maneuver said cut-off arm, a second insulative support 
column carrying a second current terminal and a jaw-type second contact 
cooperating with said first contact when said circuit-breaker is closed, 
said pivoting arm rotating about its axis through 90.degree. at the start 
of an opening maneuver or at the end of a closing maneuver to close said 
jaw on opening the circuit-breaker and to open said jaw on closing the 
circuit-breaker, wherein said cut-off arm is extended by a cylindrical 
assembly containing a resistance and comprising a metal exterior tubular 
portion connected electrically to said resistance, said tubular portion 
coming into contact at the end of a circuit-breaker closing maneuver or at 
the beginning of a circuit-breaker opening maneuver with two pole horns 
mechanically attached to said second column and electrically connected to 
said second current terminal, whereby said resistance is inserted into 
said circuit of said circuit-breaker via said pole horns and said tubular 
portion, thereby permitting said resistance to be short-circuited when 
said cut-off arm has rotated 90.degree. about its axis at the end of a 
closing maneuver. 
The invention will be clearly understood from the following description of 
a preferred embodiment of the invention with reference to the appended 
drawings.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows a high-voltage circuit-breaker closed. A first insulative 
support column 1 supported by a metal structure 2 has a first current 
terminal 3 at its upper end. The circuit-breaker includes a cut-off arm 4 
pivoted at one end for rotation in the plane of FIG. 1 over 90.degree. and 
operated by a mechanism 5 controlled by an insulative column 6 extended by 
an operating rod 7 actuated by a handwheel 8. The mechanism 5, which does 
not constitute part of the present invention, is familiar to the man 
skilled in the art and will not be described in more detail. Suffice to 
say that it enables the cut-off arm 4 to be rotated in the plane of the 
figure, in the direction of the arrow F1, 90.degree. to close the 
circuit-breaker and in the direction of the arrow F2 to open it 90.degree. 
to a vertical upright position on column 1, accompanied by rotation of the 
arm 4 about the axis of the arm to obtain an ice-breaking effect. The 
cut-off arm 4 carries a first contact 9, FIG. 2 cooperating when the 
circuit-breaker is closed with a second contact 14 to be described later. 
The circuit-breaker includes a second insulative column 10 disposed on a 
metal structure 11 and provided in its upper, part with a second current 
terminal 12. This terminal 12 is electrically connected to the second 
electric contact 14 (usually a jaw) mentioned above and which cooperates 
with the contact 9 (blade). 
FIGS. 2 and 3 are views to a larger scale of the end of the cut-off arm 4, 
respectively from the front and from the side. 
The contact 9 is usually a blade ending in a part referred to as the 
hammer. At the end of the closing maneuver the cut-off arm 4 rotates about 
its axis through 90.degree., the effect of which is to break any deposit 
of ice and to close the jaw 14, so ensuring excellent electrical contact 
with the hammer of contact 9. At the maneuver to open the circuit-breaker 
the arm 4 pivots about its axis through 90.degree. to open the jaw 14. 
The hammer is extended by a cylindrical assembly 16, FIG. 2, containing a 
resistance designed to be inserted electrically into the circuit of the 
circuit-breaker at the end of the closing maneuver or at the start of the 
opening maneuver. To this end the cylindrical assembly 16 comprises an 
exterior metal tubular portion 16A connected electrically to said 
resistance and cooperating with two pole horns 17 and 18 fixed to the top 
of the column by a bracket 19. 
FIGS. 4 and 5 show that the horn 17 is fixed and that the horn 18 pivots 
about an axle 20. The horn 18 is therefore able to move slightly in the 
direction of the arrow F3 in a plane perpendicular to the plane in which 
the cut-off arm moves. 
The pole horns 17 and 18 are disposed in a common plane perpendicular to 
the plane in which the cut-arm 4 moves and are urged towards each other by 
a spring 21 to ensure good contact with the metal tubular portion 16A. 
FIG. 6 shows the construction of the tubular assembly 16 and its contents. 
Reference will also be made to FIG. 7. 
The cylindrical assembly 16 comprise a metal block 31 into which is screwed 
an insulative rod 32. A sachet of dessicator material 33 is placed in a 
recess in the block 31. A bearing washer 34 ensures good electrical 
contact between a first end of the resistance, formed from a stack of 
resistance elements (wafers) 35, and the block 31. The resistance elements 
are advantageously disks with a center hole fitted over the insulative rod 
32. The block 31 is mechanically secured to the cut-off arm 4, for example 
by metal screws. The block 31 is electrically connected to the first 
contact 9 of the cut-off arm. 
A washer 34A located the other end of the resistance provides a bearing 
surface for a compression spring 37 which, through a ring 38, bears on a 
shoulder on a screwthreaded member 39 screwed to the end of the insulative 
rod 32. The spring 37 applies to the washer 34A a force in the order of 2 
500 Newtons to secure a good electrical contact. 
An insulative tube 40 surrounds the wafers 35. The tube 40 is fixed to the 
block 31 at one end. 
The insulative tube 40 is partially surrounded by a metal tube 41 which is 
screwed a metal cap 42. A grub screw 47 locks up the assembly and 
transfers current between the member 39 and the cap 42. 
O-rings 43, 44, 45 and 46 seal the volume V surrounding the resistance from 
the external environment. 
A valve 48 is used to fill the volume V with sulfur hexafluoride (SF.sub.6) 
or any other dry gas after the air has been extracted. 
A metal braid 49 provides an electrical connection between the resistance 
and the tube 12 via the washer 38, the member 39 and the cap 42. 
As shown in FIGS. 1, 2 and 7, the cylindrical assembly 16 may be partially 
surrounded by an anti-corona sphere 50 attached by means of a tube 51 
disposed coaxially with the cylindrical assembly 16 and screwed by a 
screwthreaded sleeve 52 onto the head of the screw 47. 
The circuit-breaker is completed by a second anti-corona sphere 55 (FIGS. 1 
and 2) and anti-corona rings 56, 57 and 58 (FIGS. 2 and 3). 
The pole horns 17 and 18 are preferably cylindrical and have anti-corona 
half-spheres 17A and 18A at the ends. 
To give a numerical example, for an 800 kV circuit-breaker carrying a 
continuous current of 4 000 A, the resistance must have a value of 500 
ohms and must be capable of dissipating 140 kJ in 4 s. 
The operation of the circuit-breaker will now be described: 
1. Closing of the circuit-breaker 
Assume that the circuit-breaker is initially open and is then closed on an 
inductive or capacitive load. The mechanism 5 is actuated and the cut-off 
arm 4 pivots 90.degree. from its vertical position. The end of cylindrical 
assembly 16 engages against the pole horns 17 and 18. 
When the contact 9 of the mobile arm is approximately 40 cm from the fixed 
contact 14, an arc is struck between the pole horns 17 and 18 and the 
metal portion 16A. The resistance 35 is then inserted into the circuit of 
the circuit-breaker via the horns 17, 18, the arc, the tubular portion 
16A, the tube 40, the cap 42, the member 39, the washer 38, the braid 49 
and the block 31. 
At the end of this maneuver the blade 9 comes into contact with the jaw 14 
and the resistance 35 is short-circuited. The 90.degree. rotation of the 
cut-off arm 4 about the axis of arm 4 breaks any ice that may have been 
deposited on the contacts and ensures an adequate contact pressure. 
2. Opening of the circuit-breaker 
As soon as the pivoting arm has completed its 90.degree. rotation about its 
axis, the main contact of the jaw type second contact 14 opens. The 
current is diverted towards the pole horns 17 and 18 and the resistance 35 
is inserted. 
Because of the presence of the resistance the contact members of the 
circuit-breaker are not subject to the damaging effects of preliminary 
arcing associated with a circuit-breaker opening or closing maneuver in 
the presence of an inductive or capacitive current. 
The invention is simple to implement. Existing circuit-breakers do not need 
major modification to be equipped with the device in accordance with the 
invention. 
The invention is more particularly applicable to high-voltage and 
very-high-voltage circuit-breakers and to grounding circuit-breakers.