Hydraulic device for a hydraulic drive for a high-tension circuit-breaker

A hydraulic device for a hydraulic drive for a high-voltage circuit-breaker includes a drive piston for a movable contact piece having two piston sides being in connection with a high-pressure reservoir in a closed condition and being acted upon by high-pressure fluid on both sides. For circuit-breaking, a switch-over valve releases a path to a low-pressure space for the fluid in the space with the larger piston area. At least one circuit-closing pilot valve and circuit-breaking pilot valve activate the switch-over valve. A settable delay volume for the fluid is connected in parallel with at least the at least one circuit-breaking pilot valve.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a hydraulic device for a hydraulic drive for a 
high-voltage or high-tension circuit-breaker, including a drive piston for 
a movable contact piece having two piston sides being in connection with a 
high-pressure reservoir in a closed condition and being acted upon by 
high-pressure fluid on both sides, a switch-over valve releasing a path to 
the low-pressure space for the fluid in the space with the larger piston 
area, for the purpose of circuit-breaking, and at least one 
circuit-closing pilot valve and circuit-breaking pilot valve for 
activating the switch-over valve. 
The movable contact piece of a high-voltage circuit-breaker, in particular 
an SF.sub.6 gas-isolated circuit-breaker, is connected to the drive piston 
of a drive piston cylinder configuration. The drive piston is actuated by 
a hydraulic configuration for opening and closing the circuit-breaker. For 
that purpose, the two spaces on either side of the working piston are 
acted upon by a fluid at high pressure. The pressure is provided by a 
hydraulic reservoir which can be configured as a gas reservoir or a spring 
reservoir. The piston area in the first space is larger than that in the 
second space because the piston rod is connected to the piston in the 
latter space. Both spaces of the drive piston and cylinder configuration 
are connected to a switch-over valve which releases a path for the 
high-pressure hydraulic fluid into a low-pressure volume. 
The switch-over valve is activated hydraulically by means of pilot valves 
which have to be actuated electromagnetically, with circuit-breaking pilot 
valves and circuit-closing pilot valves being normally provided to suit 
the desired switching sequence. An OFF-ON-OFF switching sequence can be 
achieved with two circuit-breaking pilot valves and one circuit-closing 
pilot valve. 
It is known that high-voltage circuit-breakers can only extinguish the 
current to be interrupted on transition through zero current. However, 
where a short-circuit current has to be switched off, a decaying direct 
current proportion is superimposed on the alternating current proportion 
and the switching capability of the circuit-breaker becomes greater as the 
direct current proportion decays. 
In some cases, particularly for switch gears in the U.S.A., a delaying 
electrical relay is connected into the breaker circuit so as to permit an 
increase in the circuit-breaking power. However, for reliability reasons, 
circuit-breakers should be opened directly without additional possible 
fault elements, such as circuit-breaking relays. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the invention to provide a hydraulic device 
for a hydraulic drive for a high-voltage circuit-breaker, which overcomes 
the hereinafore-mentioned disadvantages of the heretofore-known devices of 
this general type, which has a circuit-breaking delay and in which the 
circuit-breaker is opened by direct means. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, in a hydraulic drive for a high-voltage 
circuit-breaker having a contact piece being movable between open and 
closed conditions, a drive piston for the movable contact piece having a 
side with a larger piston area disposed in one space and side with a 
smaller piston area disposed in another space, a hydraulic device for the 
hydraulic drive, comprising a high-pressure reservoir being in connection 
with the two piston sides in the closed condition for acting upon both 
sides with high-pressure fluid; a low-pressure space; a switch-over valve 
releasing a path to the low-pressure space for the fluid in the space with 
the larger piston area for circuit-breaking; at least one circuit-closing 
pilot valve and circuit-breaking pilot valve for activating the 
switch-over valve; and a settable delay volume for the fluid being 
connected in parallel with at least the at least one circuit-breaking 
pilot valve. 
According to the invention, therefore, a delay volume for the fluid is 
connected in parallel with the at least one circuit-breaking pilot valve. 
Due to the delay volume, the pressure drop in the conduit between the 
circuit-breaking pilot valve and the hydraulic control side of the 
switch-over valve is delayed so that the mechanical circuit-breaking time 
of the circuit-breaker is lengthened. 
In accordance with another feature of the invention, it is, of course, 
possible to connect the delay volumes of both circuit-breaking pilot 
valves in parallel so that a delay takes place both with circuit-breaking 
using the first circuit-breaking pilot valve and with circuit-breaking 
using the second circuit-breaking pilot valve. 
If, in addition, the delay volume is simultaneously connected in parallel 
with the circuit-closing pilot valve, the delay volume is again filled 
with hydraulic fluid during the circuit-closing procedure. 
It is self-evident that it is possible to set the delay volume so that the 
delay time is adjustable. 
In accordance with a further feature of the invention, the delay volume is 
located in a piston/cylinder configuration. 
In accordance with an added feature of the invention, the piston/cylinder 
configuration has a piston with a larger piston area bounding a cylinder 
space and a smaller piston area bounding a connecting space, the pilot 
valves have inlets and outlets, and the inlets of the circuit-breaking 
pilot valves and the outlet of the circuit-closing pilot valve are 
connected to the cylinder space being bounded by the larger piston area. 
In accordance with an additional feature of the invention, the inlet of the 
circuit-closing pilot valve is connected to the connecting space bounding 
the smaller piston area. 
In accordance with yet another feature of the invention, the 
piston/cylinder configuration includes a compensation space being sealed 
between the cylinder space bounding the larger piston area and the 
connecting space bounding the smaller piston area, the compensation space 
being connected to the low-pressure container. 
In accordance with a concomitant feature of the invention, there is 
provided a contact surface for the piston being associated with the 
cylinder space, the contact surface being adjustable for adjusting a path 
traversed by the piston. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
hydraulic device for a hydraulic drive for a high-voltage circuit-breaker, 
it is nevertheless not intended to be limited to the details shown, since 
various modifications and structural changes may be made therein without 
departing from the spirit of the invention and within the scope and range 
of equivalents of the claims. 
The construction and method of operation of the invention, however, 
together with additional objects and advantages thereof will be best 
understood from the following description of specific embodiments when 
read in connection with the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the single figure of the drawing in detail, there is seen 
an electrical high-voltage circuit-breaker 10, which can be an 
encapsulated, SF.sub.6 gas-isolated high-voltage circuit-breaker, that has 
a movable contact piece 11 which is connected to a piston rod 12 having a 
piston 13 which is guided in such a way that it can reciprocate in a 
piston/cylinder configuration 14. 
The piston 13 divides a space or chamber within the piston/cylinder 
configuration 14 into a first space or chamber 16 and a second space or 
chamber 15. The second space 15 is located where the piston rod 12 is 
connected to the piston 13, so that the piston area there is the smaller 
piston area. 
A fluid conduit 17 opens into the second space 15 and a fluid reservoir 18, 
which is a spring reservoir provided with a spring 20, is connected 
through a supply conduit 19 to the fluid conduit 17. The spring 20 is 
located on a side of a reservoir piston 22 facing away from a fluid space 
or chamber 21. A conduit 24, which opens into a low-pressure conduit 25 
that leads to a low-pressure container or fluid sump 26, is connected to a 
spring space or chamber 23 which accommodates the spring 20. In the space 
23, there is an excess pressure valve 27 which releases a path of a 
conduit 29 when the piston 22 meets a valve control element 28 in the case 
of an excess pressure. The conduit 29 is connected to the low-pressure 
conduit 25 through the excess pressure valve 27 so that the excess 
pressure is reduced to permissible values when the excess pressure valve 
27 responds. The conduit 29 opens into the space 21. A pressure drain 
screw 30 is disposed in parallel with the spring reservoir 18 between the 
conduit 17 and the conduit 25. 
A pump 31, which is driven by a motor 32, is located between the fluid 
conduit 17 and the low-pressure conduit 25. A non-return valve 33 is 
located between the pump 31 and the fluid conduit 17 and only permits 
passage of fluid from the pump 31 into the fluid conduit 17 in order to 
fill the fluid reservoir 18. A filter configuration 34 is located before 
the pump 31, as viewed in the flow direction. The pump 31 sucks fluid from 
the low-pressure container or fluid sump 26. 
A further fluid conduit 35, which is connected to a first connection 36 of 
a switch-over valve 37, opens into the first space 16. A second connection 
38 of the switch-over valve 37 is connected to the fluid conduit 17 by 
means of a third fluid conduit 39. An adjustable throttle 40 is located 
within the third fluid conduit 39. A low-pressure fluid conduit 42, in 
which there is a throttle 43 and which leads to the fluid sump 26, is 
connected to a third connection 41 of the switch-over valve. 
First and second circuit-breaking pilot valves 44, 45, having inlets 46 and 
47 which are connected in parallel, and having outlets which are connected 
to a fourth fluid conduit 48, are connected to the low-pressure fluid 
conduit 42. The outlets of the first and second circuit-breaking pilot 
valves 44, 45 are connected on one hand to a hydraulic control side 49 of 
the switchover valve 37, and on the other hand to a delay volume 50. A 
circuit-closing pilot valve 51, which is also connected to the conduit 48 
on one side, has another side which is connected to the fluid conduit 17 
that leads towards the space 21 of the reservoir 18. A fifth fluid conduit 
52, which is connected to the delay volume 50, is connected between the 
non-return valve 33 and another inlet of the circuit-closing pilot valve 
51. The inlet 47 of the valve 45, like the inlet 46 of the valve 44, is 
likewise connected to the delay volume 50 through a sixth fluid conduit 
53. 
The delay volume 50 is in a piston/cylinder configuration having a cylinder 
space or chamber 54 and a piston 55 which is guided within the space and 
on which a piston rod 56 is disposed that enters a connecting space or 
chamber 57. The piston is guided in such a away that it can move within 
the cylinder space 54 with a peripheral seal 58 fitted between them, and 
the piston rod is guided in such a way that it can move within the 
connecting space 57 with a seal 59 fitted between them. 
The conduit 52 opens into the connecting space 57, the conduit 53 opens 
into a compensation space or chamber 62 between the seal 58 and the seal 
59, and the conduit 48 opens into the cylinder space 54. 
A free path t over which the piston 55 can be moved back and forth within 
the cylinder space 54 is limited by means of a screw 60 which acts as a 
stop. The volume content of the delay volume 50 can therefore be set or 
adjusted so that the delay time of the pressure drop can also be adjusted. 
The mode of operation of the configuration is as follows: 
With the circuit-breaker closed, as is shown in the figure, the piston 13 
of the drive piston/cylinder configuration 14 is located in its upper 
position in the figure where, if the system is unpressurized, it is held 
stationary by a locking device 61 having a locking rod 62 which can engage 
in a groove 63 on the piston rod 12. If the circuit has to be broken, an 
electromagnet 44a or 4a of the valve 44 or 45 is excited so that the 
conduit 48 is connected to the low-pressure container 26. A drain cock 64 
is located on the fluid sump 26. The pressure drop generated by these 
means is slowed down by the fluid quantity located within the cylinder 
space 54 so that the switching of the switchover valve 37 is delayed to 
correspond with this slower pressure change. As soon as the valve 37 has 
been switched over, the space 16 of the working piston/cylinder 
configuration is relieved through the conduit 35 and the conduit 42, 
likewise to the low-pressure container. The throttle 43 is used to delay 
or control the draining of the fluid. Due to a brief activation of an 
electromagnet system 51a of the circuit-closing pilot valve 51, pressure 
fluid is supplied from the reservoir 18 through the fluid conduit 17 to 
the hydraulic control side 49 of the switch-over valve 37, and the piston 
55 is also moved into the position shown in the figure. The switch-over 
valve 37 is switched over into the position shown in the figure so that 
pressure fluid passes from the energy reservoir 18 into the space 16. Due 
to the resultant pressure force caused by the different piston area, the 
circuit-breaker 10 is brought into the closed position. In order to break 
the circuit again, the electromagnet system 44a or 45a of the second 
circuit-breaking pilot valve 44 or 45 is actuated briefly so that the 
hydraulic control side of the switch-over valve 37 is activated. In the 
same manner, the pressure drop is again slowed down by the delay volume 50 
so that the switching of the switchover valve 37 takes place with a delay. 
Due to this, a path is released to the low-pressure container 26 for the 
space 16 within the drive piston/cylinder configuration, so that the 
piston 13, together with the movable contact piece 11, moves into the open 
position. 
If the fluid quantity located within the energy reservoir 18, and therefore 
the pressure present in it, have fallen below a certain value, the motor 
32, which drives the pump 31, is activated so that fluid filtered by the 
filter 34 is conveyed from the low-pressure container into the reservoir 
18 through the non-return valve 33, the conduit 17 and the conduit 19.