CA1147384A - Filter input protection - Google Patents
Filter input protectionInfo
- Publication number
- CA1147384A CA1147384A CA000356610A CA356610A CA1147384A CA 1147384 A CA1147384 A CA 1147384A CA 000356610 A CA000356610 A CA 000356610A CA 356610 A CA356610 A CA 356610A CA 1147384 A CA1147384 A CA 1147384A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- filter
- transmission network
- current
- filter 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
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
Landscapes
- Supply And Distribution Of Alternating Current (AREA)
- Protection Of Static Devices (AREA)
Abstract
ABSTRACT
A system for protecting a transmission network from short circuit conditions at the input of filter circuitry connected to a single phase or a multiple phase transmission network. A signal is produced which corresponds to the current flowing from the transmission network to the filter circuit.
The signal is filtered by a low-pass filter for attenuating its harmonic con-tent and converted into a direct current signal which corresponds in amplitude to the fundamental frequency component of the current flowing to the filter circuit. Means are provided for disconnecting the filter circuit from the transmission network when the amplitude of the direct current signal exceeds a predetermined threshold level.
A system for protecting a transmission network from short circuit conditions at the input of filter circuitry connected to a single phase or a multiple phase transmission network. A signal is produced which corresponds to the current flowing from the transmission network to the filter circuit.
The signal is filtered by a low-pass filter for attenuating its harmonic con-tent and converted into a direct current signal which corresponds in amplitude to the fundamental frequency component of the current flowing to the filter circuit. Means are provided for disconnecting the filter circuit from the transmission network when the amplitude of the direct current signal exceeds a predetermined threshold level.
Description
1~473~3~
Background of the Invention This invention relates to protection systems for filter circuits connected to power transmission networks, and more particularly to systems for protecting filter circuits which are advantageously disconnectable from single phase or multiphase transmission networks.
It is known that a short circuit to ground of any of the phases of a filter clrcuit may cause extremely large current to flow from a power supply network to which the filter circuit is connected, to ground, which may event-ually result in network failure. It is desirable therefore that such currents be detected quickly so that the filter circuit may be disconnected from the network as soon as possible. Such filters are generally tuned so as to resonate at charactersitically harmonic frequencies which are present in the power distribution network and are desired to be drawn off tQ ground. Accord-ingly, it is desirable that the filter not be disconnected from the power distribution network when it draws off large filter currents at the resonant frequencies.
Accordingly, it is an object of this invention to provide an econo-mical system for protecting the input of filter circuits which are connected to single and multiphase power transmisslon networks.
It is a further object of this lnventlon to provide a fllter input protection system~which can distinguish between short~circuit conditions and large filter currents at the resonant frequency of the filter.
It is another object of this inventlon to provlde a filter~input protection system which can be disposed on a bus bar of the power distribution network for determining the current flowing through the filter.
Summary of the Inventio~n ~he foregoing and other problems are alleviated by the invention ~~
~E
: . ~
. , ~73134 which protects the input of one or more filter circuits which are connected to respective bus bars of single phase or multiple phase transmission networks, by disconnecting the filter circuits from the bus bars when a short circuit condition is detected. Circuitry is provided for determining the current flowing through the filter circuit at the fundamental frequency by suppression of the harmonics. A signal is obtained which corresponds to the amplitude of the fundamental frequency component, which signal is rectified and monitored so as not to exceed a predetermined limit. The filter circuit is disconnected from the transmission network when the limit is exceeded.
This invention is based upon the assumption that the current which flows from the transmission network bus bar during a short circuit condition contains a line frequency fundamental component and a spectrum of harmonics.
However, the current which flows through the filter circuit during normal operation contains only an attenuated line frequency fundamental component.
Accordingly, circuitry is provided for suppressing the harmonic frequency components and monitoring only the fundamental frequency component, the am-plitude of which is determinative of whether the current drawn through the filter circuit is the result~ of normal operation or short circuit conditions.
The harmonic frequency components are suppressed by a low-pass filter, which, in one embodiment of the invention, may contain several stages, the output of which advantageously attenuates the harmonic frequency components to a greater degree than the fundamental frequency component. The output signal of the low-pass filter is rectified, illustratively by a full-wave rectification bridge, and conducted directly to a limit indicator. The deletion of filter circuitry electrically disposed between the output of the rectifier and the input of the limit indicator avoids unnecessary delay in the generation of a responsive over-limit indication signal.
Background of the Invention This invention relates to protection systems for filter circuits connected to power transmission networks, and more particularly to systems for protecting filter circuits which are advantageously disconnectable from single phase or multiphase transmission networks.
It is known that a short circuit to ground of any of the phases of a filter clrcuit may cause extremely large current to flow from a power supply network to which the filter circuit is connected, to ground, which may event-ually result in network failure. It is desirable therefore that such currents be detected quickly so that the filter circuit may be disconnected from the network as soon as possible. Such filters are generally tuned so as to resonate at charactersitically harmonic frequencies which are present in the power distribution network and are desired to be drawn off tQ ground. Accord-ingly, it is desirable that the filter not be disconnected from the power distribution network when it draws off large filter currents at the resonant frequencies.
Accordingly, it is an object of this invention to provide an econo-mical system for protecting the input of filter circuits which are connected to single and multiphase power transmisslon networks.
It is a further object of this lnventlon to provide a fllter input protection system~which can distinguish between short~circuit conditions and large filter currents at the resonant frequency of the filter.
It is another object of this inventlon to provlde a filter~input protection system which can be disposed on a bus bar of the power distribution network for determining the current flowing through the filter.
Summary of the Inventio~n ~he foregoing and other problems are alleviated by the invention ~~
~E
: . ~
. , ~73134 which protects the input of one or more filter circuits which are connected to respective bus bars of single phase or multiple phase transmission networks, by disconnecting the filter circuits from the bus bars when a short circuit condition is detected. Circuitry is provided for determining the current flowing through the filter circuit at the fundamental frequency by suppression of the harmonics. A signal is obtained which corresponds to the amplitude of the fundamental frequency component, which signal is rectified and monitored so as not to exceed a predetermined limit. The filter circuit is disconnected from the transmission network when the limit is exceeded.
This invention is based upon the assumption that the current which flows from the transmission network bus bar during a short circuit condition contains a line frequency fundamental component and a spectrum of harmonics.
However, the current which flows through the filter circuit during normal operation contains only an attenuated line frequency fundamental component.
Accordingly, circuitry is provided for suppressing the harmonic frequency components and monitoring only the fundamental frequency component, the am-plitude of which is determinative of whether the current drawn through the filter circuit is the result~ of normal operation or short circuit conditions.
The harmonic frequency components are suppressed by a low-pass filter, which, in one embodiment of the invention, may contain several stages, the output of which advantageously attenuates the harmonic frequency components to a greater degree than the fundamental frequency component. The output signal of the low-pass filter is rectified, illustratively by a full-wave rectification bridge, and conducted directly to a limit indicator. The deletion of filter circuitry electrically disposed between the output of the rectifier and the input of the limit indicator avoids unnecessary delay in the generation of a responsive over-limit indication signal.
- 2 -
3~3~
Thus~ in accordance with a broad aspect of the invention, there is provided a system for protecting a transmission network from over-current conditions at an input of a filter circuit connected to the transmission net-work CF~iRACTERIZED IN TF~T there are provided a. detector means for generating a first signal corresponding to a current flowing through a connection between the filter circuit and the transmission network, b. harmonic suppression means connected to said detector means for attenuating the harmonic content in said first signal and producing a second signal which is responsive to a fundamental Erequency component in said first signal, c. rectification means connected to said harmonic suppression means for producing a direct current signal which corresponds to the amplitude of said second signal, d. limit monitoring means connected to said rectification means for producing a third signal when a predetermined response threshold is ex-ceeded by said direct current signal, and e. switching means for disconnecting the Eilter circuit from the transmission network in response to said third signal.
-2a-738~
In one embodiment of the invention, a current transformer is disposed about a conductor which connects a filter circuit to a respective one of the buses of the transmission network. The output of the current transformer pro-duces a signal which corresponds to the current flowing through the conductor, and consequently, the filter circuit. The output signal of the current trans-former is conducted to a low-pass filter which, as previously mentioned, sup-presses the harmonic content of the signal with respect to the line frequency fundamental. The output of the low-pass filter is conducted to a rectifier circuit which produces a direct current signal, the amplitude of which is largely responsive to the amplitude of the line frequency fundamental component in the filter current. The unfiltered output signal of the rectifier circuit is conducted to a limit Indicator which may have a response threshold corres-ponding to a filter circuit line frequency fundamental current component which is at least twice the amplitude of the filter circuit current during normal operation.
In accordance with a further embodiment of the invention, first and second current ~ransformers may be arranged at the network bus bar from either side of the filter circuit branch-off. The output signals of such current transformers are conducted to a comparator circuit for forming a signal which ., corresponds to the filter current. This arrangement is particularly ad-vantageous in situations where it is not feasible or desirable to attach a current transformer to the filter branch. Additionally, this arrangement may be further advantageous in situations where current transformers are already available at the transmission network bus bars.
~rief Description of the Drawings Comprehension of the in~ention is facilitated by reading the follow-ing detailed description in conjunction with the annexed drawings in which:
' .
~731~4 Figure 1 is a representation of one embodiment of the invention which is shown partly in schematic form and partly in block and line form; and Pigure 2 is a representation of a further embodiment of the invention which is also shown partly in schematic form and partly in block and line form.
Detailed Description Figure 1 depicts an embodiment of a filter input protection system in accordance with the invention which is connected to a three-phase trans-mission network bus bar, having the phases RST. Each of the filters contains a capacitor C and an inductor L, and is connected to a respective one of the network buses RST by means of switching arrangement 1. Generally, the capaci-tor C and inductor L are tuned to the frequency of a characteristic harmonic, each such filter circuit being grounded at a neutral point, as shown. In one embodiment of the invention, each capaCitOT C may be a battery of capacitors which are connected in series. Each conductor which connects a fllter circuit to its respectively associated bus RST of the network, contains a current transformer, which is respectively identlf~d as 2R, 2S or 2T. Since the filters and the protection circuitry associated therewith are all similarly constructed, only the~monitoring systems associated with phase R wlll be explained m detail. ~oreover, the numerical~data contained in the following 2a descrlption will relate to a 50 Hz~three-phase netwoTk. Persons of ordinary skill in the art can coDvert such data by known methods to enable operation of the invention at different line frequencies. The disclosed numerical data are provided for purposes of illustration and should not be construed to limit the scope of the invention. ~ ~
If a short circuit Fonditlon occurs between the conductor which con-nects the filter circuit to the~switching arrangement, and ground, or if ca-pacitor C were to fail, high current would flow from bus bar R to ground,
Thus~ in accordance with a broad aspect of the invention, there is provided a system for protecting a transmission network from over-current conditions at an input of a filter circuit connected to the transmission net-work CF~iRACTERIZED IN TF~T there are provided a. detector means for generating a first signal corresponding to a current flowing through a connection between the filter circuit and the transmission network, b. harmonic suppression means connected to said detector means for attenuating the harmonic content in said first signal and producing a second signal which is responsive to a fundamental Erequency component in said first signal, c. rectification means connected to said harmonic suppression means for producing a direct current signal which corresponds to the amplitude of said second signal, d. limit monitoring means connected to said rectification means for producing a third signal when a predetermined response threshold is ex-ceeded by said direct current signal, and e. switching means for disconnecting the Eilter circuit from the transmission network in response to said third signal.
-2a-738~
In one embodiment of the invention, a current transformer is disposed about a conductor which connects a filter circuit to a respective one of the buses of the transmission network. The output of the current transformer pro-duces a signal which corresponds to the current flowing through the conductor, and consequently, the filter circuit. The output signal of the current trans-former is conducted to a low-pass filter which, as previously mentioned, sup-presses the harmonic content of the signal with respect to the line frequency fundamental. The output of the low-pass filter is conducted to a rectifier circuit which produces a direct current signal, the amplitude of which is largely responsive to the amplitude of the line frequency fundamental component in the filter current. The unfiltered output signal of the rectifier circuit is conducted to a limit Indicator which may have a response threshold corres-ponding to a filter circuit line frequency fundamental current component which is at least twice the amplitude of the filter circuit current during normal operation.
In accordance with a further embodiment of the invention, first and second current ~ransformers may be arranged at the network bus bar from either side of the filter circuit branch-off. The output signals of such current transformers are conducted to a comparator circuit for forming a signal which ., corresponds to the filter current. This arrangement is particularly ad-vantageous in situations where it is not feasible or desirable to attach a current transformer to the filter branch. Additionally, this arrangement may be further advantageous in situations where current transformers are already available at the transmission network bus bars.
~rief Description of the Drawings Comprehension of the in~ention is facilitated by reading the follow-ing detailed description in conjunction with the annexed drawings in which:
' .
~731~4 Figure 1 is a representation of one embodiment of the invention which is shown partly in schematic form and partly in block and line form; and Pigure 2 is a representation of a further embodiment of the invention which is also shown partly in schematic form and partly in block and line form.
Detailed Description Figure 1 depicts an embodiment of a filter input protection system in accordance with the invention which is connected to a three-phase trans-mission network bus bar, having the phases RST. Each of the filters contains a capacitor C and an inductor L, and is connected to a respective one of the network buses RST by means of switching arrangement 1. Generally, the capaci-tor C and inductor L are tuned to the frequency of a characteristic harmonic, each such filter circuit being grounded at a neutral point, as shown. In one embodiment of the invention, each capaCitOT C may be a battery of capacitors which are connected in series. Each conductor which connects a fllter circuit to its respectively associated bus RST of the network, contains a current transformer, which is respectively identlf~d as 2R, 2S or 2T. Since the filters and the protection circuitry associated therewith are all similarly constructed, only the~monitoring systems associated with phase R wlll be explained m detail. ~oreover, the numerical~data contained in the following 2a descrlption will relate to a 50 Hz~three-phase netwoTk. Persons of ordinary skill in the art can coDvert such data by known methods to enable operation of the invention at different line frequencies. The disclosed numerical data are provided for purposes of illustration and should not be construed to limit the scope of the invention. ~ ~
If a short circuit Fonditlon occurs between the conductor which con-nects the filter circuit to the~switching arrangement, and ground, or if ca-pacitor C were to fail, high current would flow from bus bar R to ground,
- 4 -.
. '' ' , :
738~
possibly resulting in damage to the transmission network. Moreover, if ad-ditional filter arrangements are connected to bus bar R at other locations in the network, which additional filters are tuned, illustratively, to the fre-quencies of other harmonics, such filter circuits would also discharge via the short circuit to ground. Thus, it is essential that the short circuit condition or the damaged capacitor be disconnected from the bus bar as quickly as possible.
Each of the filter circuits is connected to a respectively associated one of evaluation circuits 6R, 6S, and 6T, by a respective current transfo-rmer 2R, 2S, and 2T. Each current transformer converts the filter current flowing through its respective conductor into an equivalent voltage across a load ; (not shown), which is designed so as to handle several times the nominal cur-rent. In one embodiment of this invention, the current transformers are each followed by an associated electronic amplifier ~not shown), which is connected as a voltage follower for decoupling the voltage at the transmission network bus bar from the respective evaluation circuit.
, A measurement voltage which is produced at the output of current transformer 2R is conducted to evaluation circuit 6R. As indicated, similarly constructed evaluation circuits 6S and 6T are assigned to the other phases.
:
In this embodiment of the invention, evaluation circuit 6R contains a three-stage low-pass filtPr having stages 3a~ 3b and 3c. The output of low~pass filter stage 3c is conducted to a rectifier Gircuit 4 which, in one embodiment of the invention, produces at its output a full-wave rectified direct current signal corresponding in amplitude to the output of low-pass filter stage 3c.
Illustratively, if the three-phase transmission network bus bar is supplied by a twelve-pulse converter circuit, in which the 11th and 13th, as well as the 23rd and 25th harmonics occur as characteristic harmonics, the time con~
. '' ' , :
738~
possibly resulting in damage to the transmission network. Moreover, if ad-ditional filter arrangements are connected to bus bar R at other locations in the network, which additional filters are tuned, illustratively, to the fre-quencies of other harmonics, such filter circuits would also discharge via the short circuit to ground. Thus, it is essential that the short circuit condition or the damaged capacitor be disconnected from the bus bar as quickly as possible.
Each of the filter circuits is connected to a respectively associated one of evaluation circuits 6R, 6S, and 6T, by a respective current transfo-rmer 2R, 2S, and 2T. Each current transformer converts the filter current flowing through its respective conductor into an equivalent voltage across a load ; (not shown), which is designed so as to handle several times the nominal cur-rent. In one embodiment of this invention, the current transformers are each followed by an associated electronic amplifier ~not shown), which is connected as a voltage follower for decoupling the voltage at the transmission network bus bar from the respective evaluation circuit.
, A measurement voltage which is produced at the output of current transformer 2R is conducted to evaluation circuit 6R. As indicated, similarly constructed evaluation circuits 6S and 6T are assigned to the other phases.
:
In this embodiment of the invention, evaluation circuit 6R contains a three-stage low-pass filtPr having stages 3a~ 3b and 3c. The output of low~pass filter stage 3c is conducted to a rectifier Gircuit 4 which, in one embodiment of the invention, produces at its output a full-wave rectified direct current signal corresponding in amplitude to the output of low-pass filter stage 3c.
Illustratively, if the three-phase transmission network bus bar is supplied by a twelve-pulse converter circuit, in which the 11th and 13th, as well as the 23rd and 25th harmonics occur as characteristic harmonics, the time con~
- 5 -~ , stant of low-pass filter stage 3a is chosen to be 0.23 milliseconds, and the time constant of low-pass filter stages 3b and 3c may be 2.7 milliseconds each. In embodiments of the invention which utilize such design parameters in the low-pass filter arrangement, the 11th and 13th harmonics are suppressed to less than 1% of the input, while the amplitude of the fundamental frequency component is reduced by only approximately 50%.
The unsmooth output signal of rectifier circuit 4 is conducted to limit indicator 5. The response threshold of limit indicator 5 is illustra-tively preselected at three times the nominal current. The output signal of the limit indicator 5 in each evaluation circuit is conducted to control system 7, which is of a known type and controls the sta~e of the switches in switching arrangement 1, and corresponding indicators ~not sho~n~. Thus, an output signal from any one of limit indicators 5 will cause control system 7 to open all of the switches in switching arrangement 1, thereby disconnecting the filter circuits from the transmission network.
Figure 2 teaches a filter input protection system in which system components ~nd subsystems which have analogous correspondence to those des-cribed with respect to the embodiment of Figure 1, are correspondingly iden-tified. Referring once again to the circuit structure associated with phase R, two current transformers 8a and 8b are disposed on transmission network bus bar R on either side of the associated filter branch. The output signal of each current transformer is conducted to a respective input of a comparator 9. The output signal of comparator 9, which corresponds to the amplitude of the filter current flowing through the filter branch, is conducted to eval-uation circuit 6R which has been described above with respect to Figure 1.
In this embodiment of the invention, a similar arrangement of current trans-formers and an associated comparator are provided for each of the additional - ~147;38~
phases S and T. This embodiment of the invention which provides two current transformers disposed on each bus bar provides the further advantage that the sections of the bus bar disposed between the current transformers are included in the filter input protection.
Although the inventive concept disclosed herein has been described in terms of specific embodiments and applications, other applications and embodiments will be obvious to persons skilled in the pertinent art without departing from the scope of the invention. The drawings and description of specific embodiments of the invention in this disclosure are illustrative of applications of the invention and should not be construed to limit the scope thereof.
:`
~' :
The unsmooth output signal of rectifier circuit 4 is conducted to limit indicator 5. The response threshold of limit indicator 5 is illustra-tively preselected at three times the nominal current. The output signal of the limit indicator 5 in each evaluation circuit is conducted to control system 7, which is of a known type and controls the sta~e of the switches in switching arrangement 1, and corresponding indicators ~not sho~n~. Thus, an output signal from any one of limit indicators 5 will cause control system 7 to open all of the switches in switching arrangement 1, thereby disconnecting the filter circuits from the transmission network.
Figure 2 teaches a filter input protection system in which system components ~nd subsystems which have analogous correspondence to those des-cribed with respect to the embodiment of Figure 1, are correspondingly iden-tified. Referring once again to the circuit structure associated with phase R, two current transformers 8a and 8b are disposed on transmission network bus bar R on either side of the associated filter branch. The output signal of each current transformer is conducted to a respective input of a comparator 9. The output signal of comparator 9, which corresponds to the amplitude of the filter current flowing through the filter branch, is conducted to eval-uation circuit 6R which has been described above with respect to Figure 1.
In this embodiment of the invention, a similar arrangement of current trans-formers and an associated comparator are provided for each of the additional - ~147;38~
phases S and T. This embodiment of the invention which provides two current transformers disposed on each bus bar provides the further advantage that the sections of the bus bar disposed between the current transformers are included in the filter input protection.
Although the inventive concept disclosed herein has been described in terms of specific embodiments and applications, other applications and embodiments will be obvious to persons skilled in the pertinent art without departing from the scope of the invention. The drawings and description of specific embodiments of the invention in this disclosure are illustrative of applications of the invention and should not be construed to limit the scope thereof.
:`
~' :
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A system for protecting a transmission network from over-current conditions at an input of a filter circuit connected to the transmission net-work CHARACTERIZED IN THAT there are provided a. detector means for generating a first signal corresponding to a current flowing through a connection between the filter circuit and the transmission network, b. harmonic suppression means connected to said detector means for attenuating the harmonic content in said first signal and producing a second signal which is responsive to a fundamental frequency component in said first signal, c. rectification means connected to said harmonic suppression means for producing a direct current signal which corresponds to the amplitude of said second signal, d. limit monitoring means connected to said rectification means for producing a third signal when a predetermined response threshold is exceeded by said direct current signal, and e. switching means for disconnecting the filter circuit from the transmission network in response to said third signal.
2. The system of claim 1 in which said detector means comprises a cur-rent transformer and said harmonic suppression means comprises a low-pass filter.
3. The system of claim 2 in which said rectification means comprises a full-wave rectifier circuit and said predetermined response threshold of said limit monitoring means corresponds to at least twice the magnitude of a pre-determined nominal current flowing through said connection between the filter circuit and the transmission circuit.
4. The system of claim 1 in which said detector means comprises:
a. first and second current transformers, each disposed on a bus of the transmission network, on either side of the connection between the filter circuit and the transmission network, each for producing a signal corresponding to a respective current flowing through said bus, and b. comparator means connected to said first and second current transformers for producing a signal which corresponds to the difference between the signals produced by said first and second current transformers.
a. first and second current transformers, each disposed on a bus of the transmission network, on either side of the connection between the filter circuit and the transmission network, each for producing a signal corresponding to a respective current flowing through said bus, and b. comparator means connected to said first and second current transformers for producing a signal which corresponds to the difference between the signals produced by said first and second current transformers.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2929757.2 | 1979-07-23 | ||
| DE19792929757 DE2929757A1 (en) | 1979-07-23 | 1979-07-23 | FILTER INPUT PROTECTION |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1147384A true CA1147384A (en) | 1983-05-31 |
Family
ID=6076502
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000356610A Expired CA1147384A (en) | 1979-07-23 | 1980-07-21 | Filter input protection |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0022952A1 (en) |
| JP (1) | JPS5619335A (en) |
| CA (1) | CA1147384A (en) |
| DE (1) | DE2929757A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112242693A (en) * | 2020-09-25 | 2021-01-19 | 中国直升机设计研究所 | Direct current bus bar short-circuit protection device and method |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU1286392A (en) * | 1992-03-12 | 1992-09-10 | Togami Electric Mfg. Co., Ltd. | Downed conductor automatic detecting device |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2451353C2 (en) * | 1974-10-29 | 1976-08-19 | Siemens AG, 1000 Berlin und 8000 München | Protection circuitry for a high voltage capacitor block |
| US4104687A (en) * | 1976-11-24 | 1978-08-01 | S&C Electric Company | Device for detecting unbalanced conditions in a polyphase equipment bank |
| GB2008345B (en) * | 1977-11-14 | 1982-08-18 | Multilin Inc | Method of and apparatus for monitoring polyphase currents |
-
1979
- 1979-07-23 DE DE19792929757 patent/DE2929757A1/en not_active Withdrawn
-
1980
- 1980-06-30 EP EP80103709A patent/EP0022952A1/en not_active Ceased
- 1980-07-21 CA CA000356610A patent/CA1147384A/en not_active Expired
- 1980-07-23 JP JP10106080A patent/JPS5619335A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112242693A (en) * | 2020-09-25 | 2021-01-19 | 中国直升机设计研究所 | Direct current bus bar short-circuit protection device and method |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2929757A1 (en) | 1981-02-12 |
| JPS5619335A (en) | 1981-02-24 |
| EP0022952A1 (en) | 1981-01-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |