Electricity: electrical systems and devices – Safety and protection of systems and devices – Feeder protection in distribution networks
Reexamination Certificate
2000-05-22
2003-07-08
Sircus, Brian (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Feeder protection in distribution networks
Reexamination Certificate
active
06590755
ABSTRACT:
The invention relates to an apparatus for electronic monitoring of the supply current of modules connected to a bus, in particular for monitoring the supply current of bus devices of an automation bus system.
Present day automation systems, that is to say control and data transmission systems, generally have a multiplicity of electronic modules which all have to be supplied with electric energy. For this purpose, the individual modules, for example the bus devices, are connected in parallel to a voltage supply by means of a central power supply unit. A short circuit occurring in a bus device, or an overload which occurs can lead to the consequence that the voltage supply collapses, and thus the other connected modules cannot be further supplied with energy either, and therefore fail. The data traffic in the automation bus system fails, and this finally entails a total failure of the system. Fault location, that is to say locating the fault site, is possible only by virtue of the fact that the individual modules are removed from the system and individually checked, something which is very time-consuming.
In order to prevent the total failure of the system, the modules are frequently connected to a voltage supply by segment or section, an individual segment being protected against short circuits with the aid of a fuse or a miniature circuit breaker. However, in this case the feeding power supply unit must be capable of carrying out the isolation of the relevant segment from the supply in a reliable fashion, if required. In some circumstances, however, tripping the fuse can give rise to difficulties as long as the branch to be protected against short circuits is in overload, but no short circuit is yet present.
The object of the invention is thus to provide an apparatus for electronic monitoring of the supply current of modules connected to a bus, which on the one hand, if required, carries out reliable isolation from the supply voltage, and simultaneously maintains the diagnostics capability for the purpose of fault locating.
This object is already achieved by means of an apparatus having the features of claim
1
, and by means of an automation bus system as claimed in claims
15
and
16
.
Advantageous developments of the invention are specified in the subclaims.
In order to be able reliably to detect the occurrence of a fault, that is to say an overload or a short circuit inside a module or a connection between the modules, the apparatus according to the invention comprises a device for detecting the flowing supply current. Furthermore, the apparatus has a device for limiting and/or for disconnecting the supply current, which operates in response to the detected supply current, and thereby ensures that the energy supply for other modules of the automation bus, which are connected in parallel with reference to the supply voltage, does not fail, as a result of which at least a limited operation of the system is maintained, and thus fault diagnosis is also possible despite the occurrence of an overload or a short circuit. If the device for detecting the supply current establishes, for example, an impermissibly increased supply current, the supply current for the module connected downstream of and assigned to the apparatus is disconnected in response thereto, or at least limited.
In this case, according to the invention a module can be an arbitrary component or an arbitrary unit, which can be used to design an automation system.
It is possible for the first time with the aid of the invention for bus segments, in the event of a fault or on start-up, to be connected and disconnected in a noninteracting fashion with full maintenance of the diagnostic function, since owing to the isolation of the module which is, for example, defective or has a defective assigned connecting line, only this one module or a single segment of the system with a plurality of modules is isolated from the supply voltage, while the remainder of the system remains in operation.
In order, on the one hand, further to improve the possibility of diagnosis and, on the other hand, to provide communication between the apparatus according to the invention and the controller of the automation system, the apparatus can be connected to the automation bus. Consequently, the apparatus according to the invention can, for example, be caused to disconnect a module, in particular a bus device, by the controller of the system. This signifies a marked improvement in the reliability of such automation bus systems since, for example, unreliable bus devices which no longer react to the customary control commands can be disconnected via the controller. Furthermore, the controller can retrieve the supply current flowing toward the module at any time, and thus make an early detection of overloads which may be developing, and thereupon initiate the necessary measures before the failure of the bus device or the module.
In order to provide a high flexibility of the apparatus according to the invention for the purpose of adaptation to all conceivable requirements, the parameterization of the disconnection, in particular the tripping current and/or the disconnection characteristic, can be performed manually and/or via the bus. Consequently, it is also possible, for example, for the response of the apparatus according to the invention to the detected supply current or to the detected electric load to be modified during operation of the system, and/or the apparatus can be reset centrally to altered conditions, for example to an exchange of a module with a changed supply voltage requirement.
For the purpose of modifiable setting, the apparatus according to the invention can comprise a storage device in which, for example, the limiting value of the supply current, that is to say the value at which, or in the case of the exceeding of which, the device disconnects the supply current, or the supply current is limited, can be stored as tripping current value. Furthermore, the disconnection characteristic or else minimum, maximum and instantaneous values of the supply current can be stored in the storage device, these values being available, for example, in the case of a diagnosis on the apparatus or, for example, a diagnostic program via the automation bus. In addition, time marks assigned to the respective current values can also be stored for the purpose of detecting a temporal variation in the supply current. Furthermore, these values can also be retrieved by the controller at any time.
In order to support the fault locating, and to provide a simple control possibility, it can be provided to render the denoted supply current values readable by means of a display device on the unit or on a display assigned thereto.
In order to prevent inadvertent reconnection of the supply current, the apparatus is automatically locked after the response of the disconnection or of the limitation, and can be cleared only manually or, depending on the embodiment, also via the bus by means of a reset. This is important, in particular, so that a disconnected module is not reconnected inadvertently, something which could entail consequential damage under some circumstances.
The apparatus according to the invention can advantageously also be set up to detect ground faults.
In order to provide flexible adaptation to all conceivable possibilities of use of the apparatus according to the invention, the apparatus can comprise a power supply unit, in order, for example, to adapt a single-phase or three-phase ac voltage to the dc voltage or dc voltages usually required of a bus device. Consequently, together with the additional feature of the bus connection of the apparatus according to the invention the advantageous result is a power supply unit with bus capability in the case of which individual voltages, or all voltages provided, can be connected or disconnected, for example, by means of the controller via the bus, or else manually. If the bus logic circuit and unit logic circuit (for example sensor system or activator system) of a bus device are supplied separately, it
Behr Thorsten
Grewe Harald
Kitov Zeev
Phoenix Contact GmbH & Co.
Sircus Brian
LandOfFree
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