Patent Application
20080129309
The present invention relates the to technical field of the control of the operating status of electrical systems consisting, for example, of meshes including loads arranged in series, with specific reference to public and airport lighting systems.
In the field of lighting, different types of lamps are known, such as low or high pressure, mercury vapours, incandescence, halides, and so on, wherein the emitted light flow depends on the intensity of the electrical current circulating therein; as a consequence, outdoor or public lighting systems, for example, require the connection of the corresponding electrical loads in a series, with circulation of a same current in each of them, to allow as even as possible lighting of the environment, that is, of the road surface.
Public lighting systems, in particular, generally have a considerable size, which requires the installation, on each lamp powered by a relevant current transformer, of auxiliary devices capable of communicating the proper operating condition of the lamp itself to a control unit, placed at the same power supply apparatus; besides integrating more additional functions, such devices operate, in short circuit condition, for example a branch located in parallel to the lamp, thus preventing the onset of dangerous overvoltages at the terminals of the latter in the event of breakage. The “communication” between each auxiliary device and the control unit, for example, through the so-called line carrier system, which allow the use of the same power line as a means for the transmission of information signals; in this way the control unit, through the power supply line and according to the so-called polling technique, polls each device individually, which makes the operating status of the associated lamp known. In this way it is possible to know, with a time delay depending on the number of loads present in the system, when and which lamp is out of order, thus allowing the replacement thereof.
At present, electrical systems of a certain size and number of loads, exhibit considerable disadvantages when one or more ground failures occur, both for detecting the current to ground, sometimes not sensed by the relevant apparatus (such as circuits with branched loads) and for the exact location of the failure point or points. In circuits with loads in series, in particular, the failed triggering of the operating means for disconnecting the system could pose a serious hazard for the safety of the nearby people (direct contact with parts connected to a voltage source).
To detect a ground failure, some power supply sources are provided with additional equipment which sets a “direct” potential difference at the line conductors; in operating conditions, therefore, an alternating current circulates in the power circuit, obtained by the sum of a sinusoidal power supply current and a direct component. In the event of a ground failure, a part of the direct current closes along a circuit that includes the additional equipment, provided with an amperometer and referred to ground, the ground itself and a portion of power supply conductor up to the failure point.
However, such detection technique cannot provide any information regarding the exact ground failure point.
To make things worse, it is noted that no effective techniques or methods are known for the prompt detection of the exact failure point, so the resulting problems can sometimes be unacceptable: in the event of a failure, in fact, the engineers move from one point of the system to the other, each time insulating portions of the circuit and carrying out, for example, resistance measurements by bridge methods; as it can be easily understood, such operations require much time for detecting the failure point. As a possible consequence thereof, this could bring to the manufacture of systems with an insulation degree, for example, higher than what required by the specific regulations.
The object of the present invention is to propose a method for detecting and locating a ground failure in an electrical line, which should allow detecting and locating in a short time any ground failure in an electrical circuit consisting of loads connected in series with one another or branched from a power supply line.
The above object is achieved, in accordance with the contents of the claims, by a method for detecting and locating a ground failure in an electrical line to which there are connected electrical loads powered by a power supply and control apparatus, each electrical load consisting of a load element and of an auxiliary device, electrically connected to each other, characterised in that it provides for:
According to a variation thereof, the method provides for:
The features of the invention, not appearing from the aforesaid, will appear more clearly from the following description, in accordance with the claims and with reference to the annexed drawing tables, wherein:
With reference to the annexed drawing tables, reference numeral 1 denotes a power supply and control apparatus, intended for powering an electrical circuit L consisting of a plurality of electrical loads C1, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn which, in the example shown in
The power supply and control apparatus 1, besides powering said electrical circuits, is capable of communicating on the same electrical circuit L and for example, by means of conveyed waves, with the auxiliary devices D1, . . . , Di, Di+1, Di+2, . . . , Dj, Dj+1, . . . , Dn according to the modes as described in the following. The description of the method refers, for example, to any two adjacent electrical loads Ci and Ci+1, hereinafter respectively referred to as first and second electrical load Ci, Ci+1, as well as the elements forming them and the signals they generate, for higher clarity of description. The method of the present invention provides for:
Based on the method described above, it is clear that each auxiliary device, such as the second device Di+1, associated to the second load Ci+1, communicates with the auxiliary devices Di+2 and Di of the adjacent loads, for example with a periodical frequency.
In the light of the above, the subject method provides for the first and the second information signal Inf(i+1,(i)), Inf(i,(i+1)), sent to the power supply and control apparatus 1 for example with periodical frequency, to contain at least a portion respectively of the first and second control signals S(i,i+1), S(i+1,i); in this way, the power supply and control apparatus 1 can check, after analysing the above information signals, the presence of any generic ground failures between the electrical loads Ci and Ci+1. As an alternative, such analysis of the first and second control signal S(i,i+1), S(i+1,i) can be carried out during the reception of the latter respectively by the second and first auxiliary device Di+1, Di; in the event of a failure between said first and second electrical load Ci, Ci+1, the associated auxiliary devices Di+1, Di respectively send a second and a first information signals Inf(i,(i+1)), Inf(i+1,(i)) to the power supply and control apparatus 1, which is therefore informed of the presence of the failure between the electrical loads.
The signals circulating on the electrical line L, for example the control signals S(i,i+1), S(i+1,i), contain an identification code that differentiates them from the others, allowing their recognition by the auxiliary devices that receive them. Said first control signal S(i,i+1), for example is recognised, acquired and optionally processed by the auxiliary devices of the loads adjacent the first electrical load Ci, thanks to such identification code, whereas it is ignored by all the others auxiliary devices.
As an alternative, the information signals, in the above example signals Inf(i,(i+1)), Inf(i+1,(i)), can be transmitted by means of electromagnetic waves by said auxiliary devices, in the example Di, Di+1, to the power supply and control apparatus 1.
The above method allows detecting and locating a ground failure in the electrical circuit L also in the case where only one between said first control signal S(i,i+1) and second control signal S(i+1,i) is transmitted between generic auxiliary devices, for example said first and second device Di, Di+1, If for example we consider the transmission of only the first signal S(i,i+1) from the first auxiliary device Di, associated to the first load Ci, to the second auxiliary device Di+1, associated to the second load Ci+1, adjacent the first one, the reception of such first signal S(i,i+1) will cause the consequent transmission, optional or systematic, according to the modes described above, of said first information signal Inf(i+1,(i)).
The power supply and control apparatus 1 comprises electrical loads, connected to the ends of the electrical line L and of which, for simplicity, only the associated auxiliary devices D0 and Dn+1, have been indicated, which add up to said plurality of electrical loads C1, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn, since the control and information signals are managed similarly as described above: in this way it is possible to detect and locate any generic ground failure in any point of the electrical circuit L.
An embodiment variation provides for the connection of said electrical loads C1, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn, branching from the electrical circuit L powered by the power supply and control apparatus 1, as shown in
In this case, the power supply and control apparatus 1 comprises a single electrical load, of which only the associated auxiliary device D0 is indicated, connected branching at the beginning of the electrical line L and belonging to said plurality of electrical loads C1, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn since the control and information signals are managed similarly, as described above.
A possible ground failure on the electrical line L is shown in
It should be noted that the reciprocal communication between adjacent auxiliary devices, and between the latter and the power supply and control apparatus 1, can occur for example by periodic cycles; the lower or higher criticality (lighting system of an airport) of a circuit can be managed by adjusting the cycle time within wide time ranges.
A further embodiment variation is described hereinafter, always with reference to a power supply and control apparatus 1 that powers a plurality of electrical loads C1, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn on an electrical line L, arranged in cascade with each other or branching from the same line; in particular, a generic electrical load and the associated auxiliary device are considered, respectively defined as first electrical load Ci and first auxiliary device Di, for convenience of description. Such variation provides for:
According to what follows from the above remarks, there is a communication, for example of periodic type, between the power supply and control apparatus 1 and any auxiliary device associated to a generic electrical load, belonging to the plurality of electrical loads mentioned above. With reference for example to
By way of an example, if the power supply and control apparatus 1 communicates respectively with the auxiliary devices of loads C1, C2, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn, according to the above method, see
More in general, the location of the portion concerned with a ground failure is made possible by the analysis, by the power supply and control apparatus 1, of the response signals transmitted by the auxiliary devices arranged upstream and downstream of the same failure point.
It is noted that the identification signals sent by the power supply and control apparatus 1 and intended for the corresponding auxiliary devices, can be transmitted by means of conveyed waves (continuous arrow in
The power supply and control apparatus 1 comprises electrical loads, connected to the ends of the electrical line L (of which the relevant auxiliary devices D0, Dn+1 are indicated) which add up to said plurality of electrical loads C1, C2, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn, their operation is similar to what described above.
The subject variation can also be applied if the electrical loads C1, C2, . . . , Ci, Ci+1, Ci+2, . . . , Cj, Cj+1, . . . , Cn are connected branching from the electrical circuit L: this circuit configuration, in particular, is not reported in the annexed tables since what described with reference to the connection of loads in branching (reference to
Finally, always with reference to such variation, both with loads connected in series and branching from said electrical line L, it is possible to provide in each auxiliary device, associated to a corresponding load belonging to said plurality of electrical loads, the possibility of analysing the identification signal it receives, coming from the power supply and control apparatus 1. In the following description, a generic electrical load and the associated auxiliary device are considered, respectively defined as first electrical load Ci and first auxiliary device Di. Such other variation therefore provides for:
In this case, the first analysis is carried out for recognising any alterations of the first identification signal Id(A,i) due to the passage of the latter through a portion concerned by a ground failure; as already mentioned several times, a signal thus altered, transmitted on an electrical line by means of conveyed waves and with frequencies falling within certain ranges, differs from any other anomaly or noise that could occur thereon. The first auxiliary device Di, then, sends the information relating to such first analysis, along with other data for example concerning the operating status of the electrical load associated thereto, to the power supply and control apparatus 1, by means of conveyed waves or by means of electromagnetic waves; the latter, in turn, receives and carries out a second analysis on the first response signal Risp(i,A). In this way, if the first identification signal Id(A,i) has passed on a portion with ground failure and the first response signal Risp(i,A) is sent by means of conveyed waves, for example, said apparatus 1 carries out the second analysis of the last signal in order to check the relevant further alteration besides decoding the associated information contents; this is useful, for example, when a certain time elapses between transmission of the first identification signal Id(A,i) and reception of the response signal Risp(i,A), in order to implement an even more effective control of the electrical line L.
The advantage of the present invention is that it defines a method for detecting and locating a ground failure in an electrical line, which is capable of detecting and locating the failure point in an electrical circuit consisting of loads in cascade with one another, branched from a power supply line or even generally, connected to the line itself; such location, moreover, occurs in very short times, within seconds, considerably shorter than the currently adopted methods.
The detection of the portion concerned with the failure allows the specialised personnel to intervene and remove the portions of cable relating to such circuit portion from the sheath and insert an intact portion of the power supply cable into such sheath.
It is understood that the above is described by way of a non-limiting example and therefore any practical-application variations fall within the scope of protection of the invention, as described above and claimed hereinafter.
| Number | Date | Country | Kind |
|---|---|---|---|
| BO2005A 000023 | Jan 2005 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB06/00070 | 1/18/2006 | WO | 00 | 7/18/2007 |
