CA1231774A - Direct current circuit breaker - Google Patents
Direct current circuit breakerInfo
- Publication number
- CA1231774A CA1231774A CA000451036A CA451036A CA1231774A CA 1231774 A CA1231774 A CA 1231774A CA 000451036 A CA000451036 A CA 000451036A CA 451036 A CA451036 A CA 451036A CA 1231774 A CA1231774 A CA 1231774A
- Authority
- CA
- Canada
- Prior art keywords
- current
- gas
- circuit breaker
- arc
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
- H01H33/02—Details
- H01H33/04—Means for extinguishing or preventing arc between current-carrying parts
- H01H33/22—Selection of fluids for arc-extinguishing
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
- H01H33/02—Details
- H01H33/59—Circuit arrangements not adapted to a particular application of the switch and not otherwise provided for, e.g. for ensuring operation of the switch at a predetermined point in the ac cycle
- H01H33/596—Circuit arrangements not adapted to a particular application of the switch and not otherwise provided for, e.g. for ensuring operation of the switch at a predetermined point in the ac cycle for interrupting dc
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Circuit Breakers (AREA)
- Driving Mechanisms And Operating Circuits Of Arc-Extinguishing High-Tension Switches (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A d.c. circuit breaker comprises in parallel with a cir-cuit breaker section a current commutating auxiliary circuit for-med by a capacitance and/or an inductance. A gas mixture consist-ing essentially of an SF6 gas and nitrogen or of an SF6 gas and air is used as an arc-extinguishing and insulating medium for said breaker section.
A d.c. circuit breaker comprises in parallel with a cir-cuit breaker section a current commutating auxiliary circuit for-med by a capacitance and/or an inductance. A gas mixture consist-ing essentially of an SF6 gas and nitrogen or of an SF6 gas and air is used as an arc-extinguishing and insulating medium for said breaker section.
Description
:~.Z~3~ 7'7~
This invention relates to a direct current circuit breaker and, more particularly, ta a dir~ct current circuit breaker in which the current is commutated by its own action at the time of current interruption and in which unstable arc characteristics are utilized for establishing current zero point or zero crossing for breaking the circuit.
In the accompanying drawings:-Fig. 1 is a diagrammatic view showing the constructionof the conventional circuit breaker of the type in which the current is commutated spontaneously at the time of current inter-ruption;
Fig. 2 is a chart showing the voltage and current characteristics with time in the circuit breaker shown in Fig. l;
and Fig. 3 is a diagrammatic view showing the construction of the current breaker according to an embodiment of the present invention.
The prior-art construction of the current breaker of the above described type is shown in the wiring circuit of Fig. 1, wherein a direct current source 1 indicated conveniently as a voltage source is connected to a resistance 2 and an inductance 3 proper to the transmission line for providing a direct current system. To this system is connected a current breaker unit 4 com-prised of a current breaker section 5 adapted for breaking the circuit, a capacitor 6 and a surge absorber 7 formed by metal oxide resistor. The capacitor 6 is connected in parallel with the section 5 and used for current commutation.
With the direct current I flowing through the current breaker section 5 of the unit 4 when the section 5 starts its circuit breaking operation~ that is, its contacts start to be separated from each other, an arc is generated between the contacts of the section 5 and the direct current then flows through the arc.
~ ~3~Lt7~
It is well-known that, ~or a ce.rtain current range, -the relation between the stead~-sta~,e arc ~roltage es and the skeady-state arc current is through a variety of gases may be approximated by the Eollowing formula:
- la -.il 2~3~7"~
e i ~ = n (] ) where a and n are positive constants with ~ being usually between zeron (0) and unity (1.0).
On the other hand, the arc produced in the circuit shown in Fig. l and having the characeristics represented by the formula ~1) becomes unstable on the condition that L < ~ e C - ~ (2) where ~ represents a thermal time eonstant of the arc 7 C a capacitance of the capacitor 6, I a d.c. current and es a steady-state arc voltager with ~ being as defined in the equation (1). When the condition given by the equation (2) is satisfied, the arc produced in the circuit breaker section 5 becomes unstable.
The voltage/current characteristics prevailing at this time are shown in ~ig. 2. In this figure, ea represents the voltage across t~.e ter~inals of the breaker section 5, I the d.e. eurrent, ia the current flowing into the breaker section 5 and i the unstabie oscillating current flowing from eapaeitor 6 into the arc.
Since the above described oscillating current has eurrent zero points, the current can be interrupted at the zero crossing points. In other words, it is possible to interrupt the d.c. current when the condition of the equation
This invention relates to a direct current circuit breaker and, more particularly, ta a dir~ct current circuit breaker in which the current is commutated by its own action at the time of current interruption and in which unstable arc characteristics are utilized for establishing current zero point or zero crossing for breaking the circuit.
In the accompanying drawings:-Fig. 1 is a diagrammatic view showing the constructionof the conventional circuit breaker of the type in which the current is commutated spontaneously at the time of current inter-ruption;
Fig. 2 is a chart showing the voltage and current characteristics with time in the circuit breaker shown in Fig. l;
and Fig. 3 is a diagrammatic view showing the construction of the current breaker according to an embodiment of the present invention.
The prior-art construction of the current breaker of the above described type is shown in the wiring circuit of Fig. 1, wherein a direct current source 1 indicated conveniently as a voltage source is connected to a resistance 2 and an inductance 3 proper to the transmission line for providing a direct current system. To this system is connected a current breaker unit 4 com-prised of a current breaker section 5 adapted for breaking the circuit, a capacitor 6 and a surge absorber 7 formed by metal oxide resistor. The capacitor 6 is connected in parallel with the section 5 and used for current commutation.
With the direct current I flowing through the current breaker section 5 of the unit 4 when the section 5 starts its circuit breaking operation~ that is, its contacts start to be separated from each other, an arc is generated between the contacts of the section 5 and the direct current then flows through the arc.
~ ~3~Lt7~
It is well-known that, ~or a ce.rtain current range, -the relation between the stead~-sta~,e arc ~roltage es and the skeady-state arc current is through a variety of gases may be approximated by the Eollowing formula:
- la -.il 2~3~7"~
e i ~ = n (] ) where a and n are positive constants with ~ being usually between zeron (0) and unity (1.0).
On the other hand, the arc produced in the circuit shown in Fig. l and having the characeristics represented by the formula ~1) becomes unstable on the condition that L < ~ e C - ~ (2) where ~ represents a thermal time eonstant of the arc 7 C a capacitance of the capacitor 6, I a d.c. current and es a steady-state arc voltager with ~ being as defined in the equation (1). When the condition given by the equation (2) is satisfied, the arc produced in the circuit breaker section 5 becomes unstable.
The voltage/current characteristics prevailing at this time are shown in ~ig. 2. In this figure, ea represents the voltage across t~.e ter~inals of the breaker section 5, I the d.e. eurrent, ia the current flowing into the breaker section 5 and i the unstabie oscillating current flowing from eapaeitor 6 into the arc.
Since the above described oscillating current has eurrent zero points, the current can be interrupted at the zero crossing points. In other words, it is possible to interrupt the d.c. current when the condition of the equation
(2) is satisfied. By selecting the right side term of the equation (2) to a larger value, the term of the d.c. current I that can be interrupted can also be selected to a larger value for thereby improving the current braking capacity of the current breaker unit.
'7~a In the SF6-gas blowlng type conventiorlal d.c. current breaker, it i5 tile convelltionaL practice Lo :increcse t:he Eorce of gclS
blowing or make use oE a constructlon of an arc-extinguishin~ chambe~
designed Eor extendinq the arc length. ~lowever, since the SF6-gas tends to be llquified under an elevated pressure, a certain limitation is placed on increasing the gas pressure for producing a strong gas blowing force. On the other hand, the overall device tends to be complicated by -the provision of the arc-extinguishing ch~nber.
In view of the foregoing, it is a principal object oE the present invention ot obviate the above described deEiciency of the SF6-gas blowing type d.c. circuit breaker and to provide a d.c. circuit breaker having a higher current breaking capacity. According to the present invention, a gas mixture consisting essentially of -the SF6 gas and air or nitrogen is used and bLown into the arc as an arc-extinguishing and insulating medium for the gas blowing type d.c.
circuit breaker.
Accordingly, therefore, the present invention provides in a D.C. circuit breaker having a circuit breaker section and a current commutating auxiliary circuit connected in parallel -therewith and constituted by a capacitance and/or an induc-tance, -the improvemen-t comprising:
a buffer type blowing uni-t consisting essentially of a cylinder and a piston and a gas mixture therein consis-ting essentially of an SF6 gas and a further gas taken from the group consisting of nitrogen and air, the further gas being present in an ~mount of 20 to 80 volume percent of the SF6, said cylinder and piston being for blowing the gas mixture into said circuit breaker section for extinguishing -the arc formed therein during circuit breaking.
I'he invention will now be described in more detail, by way of example only, with reference to Fig. 3 of the accompanying drawings introduced above.
Fig. 3 shows an embodiment of the present inven-tion wherein -the same numerals 1 through 7 as those used in Fig. 1 are used to depict the same or corresponding parts. The d.c. breaker unit 7'7~L
~ is comprised of a fixed contact 8, a :movable contact 9 -that may be engaged with or disenaacJed from this .Eixed con-tact, a fl.ow ~uide member 10 placed around these contacts and secured -to said movable contact, a cylinder 11 secured to said flow guide rnember and operable with said movab].e contact, a buffer chamber 13 de~ined between the cylinder and a piston 12 slidable therein, a commutat-ing capacitor 6 in parallel with said fixed and movable contacts, and a surge absorber 7.
In the operation of the d.c. circuit breaker unit 4, when the movable contact 9 is contacted with the fixed contact 8, the unit 4 being thus closed, the totality of the current supplied from the d.c~ system flows through these contacts 8,9. In this state, when the movable contact 9 is pulled towards left in the drawing by an operating mechanism, not shown, the contacts are separated from one another so that an arc is produced between these contacts and the current flows through the arc. Since the arc voltage ea between the contacts is increased with the increase in the distance between the contacts, a current ic given by a formula _ ~ _ ~ 3~L~7'7~-~
de ic = C d.ta (~) flows through capacitor 6. On the other hand, a current ia given by a formular i = I - i (4~
flows through the contacts. As the distance between the contacts is increased so that the arc voltage e is increased to the extent that the condition shown by the above described formular ~2) is satisfied, the arc becomes unstable and the oscillating current is increased in magnitude so as to cross zero points thus providing for a circuit ~reaking operation.
Thus the current ia flowing through the contacts becomes~zero (ia = ) However, the current I is still flowing in the d.c.
system through capacitor 6 so that dt = 1 i = C
resulting in an increased voltage between the contacts. When the voltage between the contacts reaches a thresho~ld voltage V0 of the surge absorber 7, the current flows through the absorber 7 so as to be dissipated as joule's heat.
It is known in general that the value of ~ in equation (1) is higher for an arc blown by nitrogen or air than for an arc blown by SF6. Thus, in the d.c. circuit breaker shown in Fig. 3, a higher value of ~ can be obtained by using a gas mixture consisting essentially of SF6 and nitrcgen o,,n air as an arc blowing medium than in the case of using a gas consisting solely of SF6. Moreover, the marginal or critical temperature at which the above gas mixture is converted into the liquid phase is elevated than i.n the case of the SF6 gas. 'rhus a stronger pressure oE the arc blowing gas may be used, resulting in the stronger arc blowing force and the increase in the magnitude of the ri~ht side term of the Pquation (1).
It should also be noted that, while a higher pressure differential is difEicult to achieve through compression with the aid of a cylinder and a piston such as buffer system a higher pressure differential can be achieved with ease with the aid of such buffer system upon addition of an SF~ gas into these gases, thus enabling the buffer blowing system to be used advantageously in conjunction with the d.c. circuit breaker.
The mixture ratio of nitrogen or air to the SF6-gas may preferably be in the range of 20 to 80 vol. percent of nitrogen or air to the SF6-gas. The lower limit of 20 vol.
percent is set because an increase in the value of ~ or arc voltage may not be increased for lower nitrogen or air contents while the upper limit of 80 vol. percent is set because the buffer operation ceases to be effective for higher nitrogen or air contents.
From the foregoing it is seen that the arrangement of the present invention provides a d,c. circuit breaker having a larger current breaking capacity through the use of the gas mixture consisting essentially of SF6 gas and air or nitrogen as the arc-extinguishing and insulating medium.
'7~a In the SF6-gas blowlng type conventiorlal d.c. current breaker, it i5 tile convelltionaL practice Lo :increcse t:he Eorce of gclS
blowing or make use oE a constructlon of an arc-extinguishin~ chambe~
designed Eor extendinq the arc length. ~lowever, since the SF6-gas tends to be llquified under an elevated pressure, a certain limitation is placed on increasing the gas pressure for producing a strong gas blowing force. On the other hand, the overall device tends to be complicated by -the provision of the arc-extinguishing ch~nber.
In view of the foregoing, it is a principal object oE the present invention ot obviate the above described deEiciency of the SF6-gas blowing type d.c. circuit breaker and to provide a d.c. circuit breaker having a higher current breaking capacity. According to the present invention, a gas mixture consisting essentially of -the SF6 gas and air or nitrogen is used and bLown into the arc as an arc-extinguishing and insulating medium for the gas blowing type d.c.
circuit breaker.
Accordingly, therefore, the present invention provides in a D.C. circuit breaker having a circuit breaker section and a current commutating auxiliary circuit connected in parallel -therewith and constituted by a capacitance and/or an induc-tance, -the improvemen-t comprising:
a buffer type blowing uni-t consisting essentially of a cylinder and a piston and a gas mixture therein consis-ting essentially of an SF6 gas and a further gas taken from the group consisting of nitrogen and air, the further gas being present in an ~mount of 20 to 80 volume percent of the SF6, said cylinder and piston being for blowing the gas mixture into said circuit breaker section for extinguishing -the arc formed therein during circuit breaking.
I'he invention will now be described in more detail, by way of example only, with reference to Fig. 3 of the accompanying drawings introduced above.
Fig. 3 shows an embodiment of the present inven-tion wherein -the same numerals 1 through 7 as those used in Fig. 1 are used to depict the same or corresponding parts. The d.c. breaker unit 7'7~L
~ is comprised of a fixed contact 8, a :movable contact 9 -that may be engaged with or disenaacJed from this .Eixed con-tact, a fl.ow ~uide member 10 placed around these contacts and secured -to said movable contact, a cylinder 11 secured to said flow guide rnember and operable with said movab].e contact, a buffer chamber 13 de~ined between the cylinder and a piston 12 slidable therein, a commutat-ing capacitor 6 in parallel with said fixed and movable contacts, and a surge absorber 7.
In the operation of the d.c. circuit breaker unit 4, when the movable contact 9 is contacted with the fixed contact 8, the unit 4 being thus closed, the totality of the current supplied from the d.c~ system flows through these contacts 8,9. In this state, when the movable contact 9 is pulled towards left in the drawing by an operating mechanism, not shown, the contacts are separated from one another so that an arc is produced between these contacts and the current flows through the arc. Since the arc voltage ea between the contacts is increased with the increase in the distance between the contacts, a current ic given by a formula _ ~ _ ~ 3~L~7'7~-~
de ic = C d.ta (~) flows through capacitor 6. On the other hand, a current ia given by a formular i = I - i (4~
flows through the contacts. As the distance between the contacts is increased so that the arc voltage e is increased to the extent that the condition shown by the above described formular ~2) is satisfied, the arc becomes unstable and the oscillating current is increased in magnitude so as to cross zero points thus providing for a circuit ~reaking operation.
Thus the current ia flowing through the contacts becomes~zero (ia = ) However, the current I is still flowing in the d.c.
system through capacitor 6 so that dt = 1 i = C
resulting in an increased voltage between the contacts. When the voltage between the contacts reaches a thresho~ld voltage V0 of the surge absorber 7, the current flows through the absorber 7 so as to be dissipated as joule's heat.
It is known in general that the value of ~ in equation (1) is higher for an arc blown by nitrogen or air than for an arc blown by SF6. Thus, in the d.c. circuit breaker shown in Fig. 3, a higher value of ~ can be obtained by using a gas mixture consisting essentially of SF6 and nitrcgen o,,n air as an arc blowing medium than in the case of using a gas consisting solely of SF6. Moreover, the marginal or critical temperature at which the above gas mixture is converted into the liquid phase is elevated than i.n the case of the SF6 gas. 'rhus a stronger pressure oE the arc blowing gas may be used, resulting in the stronger arc blowing force and the increase in the magnitude of the ri~ht side term of the Pquation (1).
It should also be noted that, while a higher pressure differential is difEicult to achieve through compression with the aid of a cylinder and a piston such as buffer system a higher pressure differential can be achieved with ease with the aid of such buffer system upon addition of an SF~ gas into these gases, thus enabling the buffer blowing system to be used advantageously in conjunction with the d.c. circuit breaker.
The mixture ratio of nitrogen or air to the SF6-gas may preferably be in the range of 20 to 80 vol. percent of nitrogen or air to the SF6-gas. The lower limit of 20 vol.
percent is set because an increase in the value of ~ or arc voltage may not be increased for lower nitrogen or air contents while the upper limit of 80 vol. percent is set because the buffer operation ceases to be effective for higher nitrogen or air contents.
From the foregoing it is seen that the arrangement of the present invention provides a d,c. circuit breaker having a larger current breaking capacity through the use of the gas mixture consisting essentially of SF6 gas and air or nitrogen as the arc-extinguishing and insulating medium.
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a D.C. circuit breaker having a circuit breaker section and a current commutating auxiliary circuit connected in parallel therewith and constituted by a capacitance and/or an inductance, the improvement comprising:
a buffer type blowing unit consisting essentially of a cylinder and a piston and a gas mixture therein consisting essentially of an SF6 gas and a further gas taken from the group consisting of nitrogen and air, the further gas being present in an amount of 20 to 80 volume percent of the SF6, said cylinder and piston being for blowing the gas mixture into said circuit breaker section for extinguishing the arc formed therein during circuit breaking.
a buffer type blowing unit consisting essentially of a cylinder and a piston and a gas mixture therein consisting essentially of an SF6 gas and a further gas taken from the group consisting of nitrogen and air, the further gas being present in an amount of 20 to 80 volume percent of the SF6, said cylinder and piston being for blowing the gas mixture into said circuit breaker section for extinguishing the arc formed therein during circuit breaking.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58245/1983 | 1983-03-31 | ||
| JP5824583A JPS59184414A (en) | 1983-03-31 | 1983-03-31 | Dc breaker |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1231774A true CA1231774A (en) | 1988-01-19 |
Family
ID=13078730
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000451036A Expired CA1231774A (en) | 1983-03-31 | 1984-03-30 | Direct current circuit breaker |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0123889B1 (en) |
| JP (1) | JPS59184414A (en) |
| CA (1) | CA1231774A (en) |
| DE (1) | DE3469824D1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4447391C1 (en) * | 1994-12-23 | 1996-06-05 | Siemens Ag | Vacuum switch |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE512921A (en) * | 1951-07-19 | |||
| US4171474A (en) * | 1977-05-27 | 1979-10-16 | Electric Power Research Institute, Inc. | Current interrupter electrode configuration |
| JPS5736733A (en) * | 1980-08-14 | 1982-02-27 | Tokyo Shibaura Electric Co | |
| JPS5774917A (en) * | 1980-10-25 | 1982-05-11 | Tokyo Shibaura Electric Co | Breaker with parallel resistor |
-
1983
- 1983-03-31 JP JP5824583A patent/JPS59184414A/en active Pending
-
1984
- 1984-03-23 EP EP84103251A patent/EP0123889B1/en not_active Expired
- 1984-03-23 DE DE8484103251T patent/DE3469824D1/en not_active Expired
- 1984-03-30 CA CA000451036A patent/CA1231774A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0123889A1 (en) | 1984-11-07 |
| JPS59184414A (en) | 1984-10-19 |
| EP0123889B1 (en) | 1988-03-09 |
| DE3469824D1 (en) | 1988-04-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |