RU2273955C1 - Device for connecting high frequency communication channels and electric transmission line - Google Patents

Abstract

FIELD: engineering of high-frequency communications along electric power lines, possible use for transmitting dispatch control signals, counter-emergency automatics and relay protection of power objects.

SUBSTANCE: connecting device at input and output has voltage surge protection devices, and consists of first inductiveness coil and adjustment node in the latter parallel relatively to each other. Connecting device additionally includes third protective device in form of power surge limiter. In case of occurrence of dangerous power surge in adjusting node aforementioned third protective device activates and transition process fades due to misalignment and decreased quality of circuit. Also to improve safety first inductiveness coil is utilized as grounding valve and together with capacitor component of power surge limiter connected on the side of device input, forms a parallel oscillation contour. Because resonance frequency of contour is positioned within pass band of device, as a result required value of inductiveness of protective valve is decreased and broadband capacity of connecting device is increased for both transformer and automatic-transformer variants of realization of resistance synchronization means into adjustment node.

EFFECT: improved reliability during operation under conditions of internal transition processes, improved safety and improved broadband capacity of connecting device.

2 cl, 2 dwg

Description

The invention relates to the field of high-frequency communication over wires of power lines (hereinafter “power lines”) and can be used to transmit supervisory control signals, emergency control equipment and relay protection of power facilities.

The connection device for high-frequency communication channels (hereinafter referred to as the connection device) is connected to the power transmission line wires through a communication capacitor and therefore must ensure safety requirements as well as operability after exposure to surge waves arising in the electric network.

The functionality of the attachment device is estimated by its bandwidth.

The known connection device, made in the form of a transformer or autotransformer half-filter of a strip type, is simple and has a minimal number of elements, but has a narrow working strip (Belous B.P., Kulikov V.V., Malyshev A.I. Operation, installation and commissioning high-frequency communication channels along power lines. M: Energy. 1970, p. 237, Fig. 13-20 and 13-25).

In another known connection device, a three-loop bandpass filter circuit is used, in which a surge protection device in the form of a spark gap with a spark gap is installed on the input side of the circuit (Mikutsky G.V., Skitaltsev BC High-frequency communication over power lines. M: Energoatomizdat. 1987, p.223, fig. 8-10).

The disadvantages of this device include the low efficiency of the arresters when exposed to surge waves with a steep front and the lack of safety when using an autotransformer as a means of matching resistances due to the presence of a galvanic connection between input and output circuits in it. Therefore, if the wire of its winding is accidentally broken, the electrical connection between the coupling capacitor and the ground is broken. As a result, the high voltage of the power frequency of the power transmission line passes at the output of the device and enters the communication equipment through the connecting cable, which is dangerous for equipment and maintenance personnel.

The closest technical solution to the claimed (its prototype) is the connection device, made according to the bandpass filter using protective devices against overvoltage without spark gaps. At the same time, an overvoltage limiter is installed on the input terminal side, and a varistor is installed on the output terminal side (S. Shlyakhov. Device for connecting high-frequency communication equipment to the wires of the power line. RF patent No. 2231898 according to application No. 20022132693/09 of 05.12.2002). Thus, a reliable limitation of the amplitude of the overvoltage wave acting from the side of the electric network is achieved. However, the unresolved issue of protecting the device elements from overvoltages caused by transients in the oscillatory circuits inside the bandpass filter circuit. In addition, the circuit with an autotransformer, a means of coordination most often used in practice, is not sufficiently secured.

The objective of the invention is to increase operational reliability in conditions of internal transients, improve security and increase the broadband connection device.

The technical result consists in increasing the electric strength, in providing the functions of a protective inductor and in expanding the working bandwidth.

To achieve this technical result, in the device for connecting high-frequency communication channels to the power line, containing input terminals, the first of which is “linear” for capacitively connecting the power line to the wire, and the second is “grounding”, the first protective cable connected to them surge protection device in the form of surge suppressor, first inductance coil and tuning unit equipped with "cable" and "ground" output terminals and consisting of earthed a resistor matching means, the input circuit of which is connected through the first capacitor to the input “linear” output, and the output circuit, inductively coupled to the input and shunted by the second capacitor, is connected through the third capacitor and the second inductor to the “cable” output terminal a second protective device in the form of a varistor is connected between the output terminals, an additional third surge protective device is introduced in the form of a surge protector connected in parallel to the first capacitor of the tuning unit, and the first inductor is a grounding inductor made of stranded copper wire with a cross section of at least 1 mm, with a resistance of not more than 20 Ohms at the industrial frequency and forming, together with the capacitive component of the first overvoltage protection device, a parallel oscillatory circuit with a resonant frequency located in the passband of the device.

In the tuning node, the resistance matching means is made in the form of a double-winding transformer.

In another embodiment, an autotransformer circuit is used as a means of matching the resistances in the tuning node.

The introduction of a third overvoltage protective device with capacitive and active resistance components allows, after its operation, to reduce overvoltages on the elements of the tuning unit to an acceptable value due to the detuning of the oscillating circuit and a sharp decrease in the quality factor of the tuning circuit, and the grounding inductor creates reliable grounding of the coupling capacitor plate which increases the safety of the device during operation.

In addition, the use of a grounding inductor to create a parallel oscillatory circuit provides additional advantages in reducing the required value of its inductance and, therefore, simplifying the design, as well as expanding the bandwidth of the device without using additional elements for these purposes.

The essence of the invention is illustrated in figures 1 and 2.

Figure 1 presents the electrical circuit diagram of the inventive device, where the matching means is made in the form of a double winding transformer.

Figure 2 presents the electrical schematic diagram of the inventive device, where the matching means is made in the form of an autotransformer.

The connection device contains input “linear” 1 and “grounding” 2 leads to which the first inductance 3 is connected, surge suppressor 4 and tuning unit 5, equipped with output “cable” 6 and grounding 7 conclusions. The matching means 8 is connected by an input circuit 9 to the first capacitor 10 connected in parallel with the third surge protection device 11. The output circuit 12 of the matching means 8 is bridged by the second capacitor 13 and connected through the third capacitor 14 and the second inductor 15 to the “cable” terminal 6. Between output terminals 6 and 7 are connected to the second protective device 16, which serves to protect the communication cable.

The coupling capacitor 17 is not included in the circuit of the attachment device, and Figs. 1 and 2 are shown conditionally to explain its operation.

The surge protection device 11 is made in the form of a surge suppressor based on highly non-linear zinc oxide resistors that sharply change their capacitive and active resistance components depending on the amplitude of the voltage applied to it.

The operation of the device will be considered on the example of figure 1 for two elements: in the case of transmission of high-frequency signals and when exposed to an overvoltage wave from the electrical network.

High-frequency signals from the transmitter through the capacitor 17 and the ground terminal 2 are supplied to the input terminals 1 and 2. The values of the elements of the circuit, consisting of the first inductor 3, the capacitance of the protective device 4 and the tuning unit 5, which includes a parallel connected capacitor 10 and a capacitance protective device 11, the inductance of the windings of the transformer 18, the capacitors 13 and 14, as well as the inductance coils 15, are selected in such a way that they create a low-attenuation bandpass filter at the output terminals 6 and 7 for the operating frequencies of the transmission chica. Thus, the connection device transmits high frequencies of the transmitter, and the current of the forward frequency is shunted through the grounding choke and does not reach the output of the device.

Matching transformer 18 provides galvanic isolation of input and output circuits and creates, if necessary, a phase rotation of the signal by 180 °.

In order to increase safety and increase widebandness, the left inductor 3 is made as a grounding inductor, providing for a current of industrial frequency a guarantee of continuity of connection of the capacitor plate 17 with grounding terminal 3 at a low resistance of 20 Ohms and, in addition, forming parallel with the capacitive component of the overvoltage limiter 4 a circuit with a resonant frequency within the passband of the attachment device. As a result, the inductance is reduced and the structural dimensions of the inductor 3 are reduced relative to traditional ones, and an additional oscillatory circuit makes it possible to expand the passband.

However, for the upper passband, the application of the circuit depicted in FIG. 1 is not always possible due to insufficient coupling coefficient (up to 0.92) between the windings of the air transformer 18. For these cases, a second embodiment of a matching means with an autotransformer 19 is provided (FIG. 2), in which, thanks to the use of a grounding inductor, issues of ensuring safety requirements have also been resolved. An autotransformer has the necessary wideband, but is more difficult to manufacture.

When overvoltage waves are supplied to the input terminals 1 and 2 from the side of the electric network, the protective device 4 is activated and their amplitude is limited to the protective level of the overvoltage limiter.

Further, due to a sharp voltage drop at the input of the tuning unit 5, a transient occurs in it, accompanied by an increase in the voltage on the elements. It acquires an aperiodic or oscillatory character depending on the quality factor of the configuration of the configuration node 5.

When the voltage on the plates of the capacitor 10 reaches the response level of the protective device 11, the capacitive and active components of its resistance are sharply reduced. This causes the detuning of the band-pass filter and a drop in its quality factor. As a result, the transient fades, and the voltage amplitudes on the elements of the tuning unit 5 do not exceed the permissible limits.

Claims (1)

A device for connecting high-frequency communication channels to a power line containing input terminals, the first of which is “linear” for connecting via a communication capacitor to the power line, and the second input terminal is “ground”, the first protective device connected in parallel to them in the form surge suppressor, the first inductor and the tuning unit, equipped with a "cable" and grounding output terminals and consisting of a grounded matching double winding an ansorptor or autotransformer, the input circuit of which is connected through the first capacitor to the input “linear” output, and the output circuit, shunted by the second capacitor, is connected through the third capacitor and the second inductor in series to the “cable” output terminal, while the second is connected between the output terminals a protective device in the form of a varistor, characterized in that a third surge protection device is inserted into the tuning unit, connected in parallel with the first capacitor And the first inductor is grounded inductor made of stranded copper wire cross-section less than 1 mm ^2, with a resistance less than 20 ohms at the mains frequency and forming together with the capacitive component of the first protective device parallel tuned circuit with a resonant frequency placed in the passband devices.

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