JPS58209236A - Signal extracting system - Google Patents

Abstract

PURPOSE:To extract a signal superimposed on a distribution line or the like based on a voltage induced in a coil, by providing the coil contactlessly with a core wire of the distribution line or the like at a location subject to the effect of a magnetic ield produced around the distribution line. CONSTITUTION:The magnetic field H at a distance (r) to the coil 6 is expressed as H=I/2pir [AT/m]. The total magnetic flux phi is expressed as Equation 1, where B=muH [wb/m<2>] is magnetic flux density and (a) is radius of the coil 6 in [m]. Further, a voltage E induced in the coil 6 is expressed in Equation 2, where N is the number of windings of the coil 6. The induced voltage E is in- creased with the coil 6 wound on a ferromagnetic substance 7. Since the relation of E0/E=f0/f is established, where f[Hz] is commercial frequency, f0[Hz] is signal frequency, and E[V], E0[V] are output voltages at respective magnetic field, a signal superimosed is detected on the basis of the induced voltage of the coil 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal extraction method for extracting high frequency signals superimposed on power distribution lines.

Power distribution lines are used as transmission lines. It is well known that signal transmission is performed by superimposing a high frequency signal on the power distribution line. In such a signal transmission method, a method using a capacitor is generally used as a method for extracting the high frequency signal superimposed on the power distribution line. In other words, this method involves connecting the capacitor directly to the core wire of the distribution line. Cover the insulation of the distribution line with electrodes. There is a so-called voltage division method in which a capacitor is connected in series with an impedance connected between the core wire and the ground to output a signal. Among these conventional methods, FIG. 1 shows a method in which a capacitor is directly connected to the core wire of a power distribution line.

In the figure, 1 indicates a distribution line, 2 indicates a coupling capacitor, 3 indicates a matching transformer, and 4 indicates a receiving device. Coupling capacitor 2
is selected to have a high impedance to the current at the grid frequency, but a low impedance to the superimposed high frequency signal, so that the high frequency signal component is supplied to the matching transformer 3 and received. It is input into the device 4.

However, all methods using capacitors have the disadvantage that they must be grounded and that it is impossible to arbitrarily change the extraction location and process quickly. Also,
In the method of connecting capacitors to the core wires of power distribution lines, as the number of capacitors increases, the ground charging current increases, causing malfunctions of protective relays installed in substations.

In view of the above, an object of the present invention is to provide a signal extraction method that can improve workability and supply reliability.

According to the present invention, a coil is provided at a position affected by the magnetic field generated around the distribution line, etc., without contact with the core wire of the distribution line, etc., and the voltage induced in the coil is This is achieved by extracting the signal superimposed on the

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

FIG. 2 shows the relative positional relationship between the power distribution line and the magnetic sensor used in the signal extraction method according to the present invention. In the figure, 5 is a power distribution line, 6 is a coil, and 7 is a ferromagnetic material. In Figure 2, from the front to the back of the paper.

Assuming that a current ICA) is flowing at a frequency f [Hz:], ', the magnetic field H at 2 at a distance r (m) to the coil 6 is from the ampere circuit law.

■ It becomes. Therefore, magnetic flux density B=μHcwb/I′I
'1'], the diameter of the coil 6 is arm], then the total number of magnetic fluxes Φ is Φ=π・a!・B=π・a2@μH. Therefore, the voltage E induced in the coil 6 is as follows, where N is the number of turns of the coil 6. When the coil 6 is wound around the ferromagnetic material 7, a phenomenon in which magnetic flux is attracted to the ferromagnetic material 7 occurs, so that the induced voltage E in equation (3) is lower than in the case of an air-core coil.
becomes larger. Therefore, when extracting the signal superimposed on the distribution line 5, the commercial frequency DHZ], the i frequency f
. [Hz], the output voltage due to each magnetic field is E
[V) and BO[V], from equation (3), the relationship essentially holds true, so the signal frequency f. By selecting an appropriate value for , the superimposed signal can be detected based on the induced voltage of the coil 6, and signal extraction becomes possible.

Furthermore, as shown in FIG. 2, if a capacitor 8 is added in parallel to the coil 6 to provide a four-row resonance condition, only the voltage at the required signal frequency can be extracted with emphasis.

The resonance frequency f at this time is expressed by the following equation.

As described above, according to the present invention, by installing the coil in the magnetic field generated around the distribution line, it is possible to extract the signal without contacting the core wire of the distribution line and without the need for grounding. . FIG. 3 shows an embodiment for installing a coil in a magnetic field around a power distribution line. A coil 6 and a ferromagnetic material 7 are embedded inside the coil 9. With such a configuration, a signal can be extracted by simply hooking the support 9 at any point on the power distribution line. However, the present invention is limited to power distribution lines, and the signal current creates a magnetic field around the line. It can be widely applied to signal transmissions such as those that occur.

[Brief explanation of the drawing]

1N is a configuration diagram showing an example of a conventional signal extraction method, the second factor is a factor showing the relative positional relationship between the magnetic sensor and the power distribution line according to the present invention, and FIG. 3 is a diagram showing the magnetic field around the power distribution line. This is a diagram showing an embodiment for installing the device inside the device. 1.5... Distribution line, 2... Coupling capacitor, 3...
・Coupling device, 4... Receiving device, 6... Coil, 7.
...Ferromagnetic material, 8...Tuning capacitor, 9...Support.

Claims (1)

[Scope of Claims] 1) In a device for extracting a signal superimposed on a distribution line, etc., a position K that is affected by a magnetic field generated around the distribution line, etc. is not in contact with the core wire of the distribution line, etc. A signal extraction method characterized in that a coil is provided in the coil, and the signal is extracted based on a voltage induced in the coil by the magnetic field. 2) % Allowance In the signal extraction method according to claim 1, the coil has a parallel-connected capacitor that provides a resonance condition with respect to the signal frequency, and only the signal component is emphasized by the voltage induced in the coil. A signal extraction method characterized by extracting signals by 3) The signal extraction method according to claim 1 or 2, wherein the coil is embedded in a support made of an insulator that is hooked onto a power distribution line or the like.