Auxiliary device for measuring return loss of power line carrier

Abstract

The invention discloses an auxiliary device for measuring power line carrier return loss. The auxiliary device comprises a high-frequency channel return loss measuring circuit, a combined filter return loss measuring circuit, an oscillator and a frequency-selecting level meter, the high-frequency channel return loss measuring circuit is a bridge circuit formed by connecting a measuring circuit with input impedance of a high-frequency channel; the combined filter return loss measuring circuit is a bridge circuit formed by connecting a measuring circuit with the output end of the combined filter; the measuring circuit comprises two resistors R1, a resistor R2 and a switch; one resistor R1 is connected with the resistor R2, and the other resistor R1 can be connected with the input impedance of a high-frequency channel or combined with the input impedance of a filter; one end of an oscillator is detachably connected between the resistor R1 and the resistor R2; and the level meter can be respectively connected between the two resistors R1 and between the resistor R2 and the switch. According to the invention, the difficulty of power line carrier line and equipment return loss measurement work is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of power line carrier return loss measurement, and in particular to a power line carrier return loss measurement auxiliary device. Background Art

[0002] Many power grid lines are affected by cold waves every winter and are prone to ice. During the period of line ice, the power line carrier, as a backup channel for line protection, is an important means to ensure the safety and smooth operation of protection services. The power line carrier circuit consists of a power line carrier machine and a high-frequency channel, in which the high-frequency channel includes a transmission line, a line wave trap (Tr), a coupling capacitor (C), a combined filter (JL) and a high-frequency cable. The power line high-frequency channel needs to be monitored regularly, that is, regular inspections of wave traps, combined equipment, high-frequency cables, high-frequency channel attenuation, and carrier machines (hereinafter referred to as regular inspections). The key contents of the power line carrier channel regular inspection include four parts: measuring the attenuation and return loss of the high-frequency channel, measuring the attenuation and return loss of the combined filter, and judging the quality of the channel and signal transmission. Return loss is a measure of the difference between the nominal output impedance of the high-frequency channel equipment and the actual input impedance of the high-frequency channel, reflecting the degree of adaptation between the actual impedance of the equipment at a certain frequency point and its nominal impedance. At present, the measurement of power line carrier high-frequency channel attenuation is relatively simple, but the return loss measurement is still difficult. Its measurement modes are diverse, the wiring is relatively complex, and the instrument values ​​also need to be converted to obtain the final result. Return loss is a measure of the difference between the nominal output impedance of the high-frequency channel equipment and the actual input impedance of the high-frequency channel, reflecting the degree of adaptation between the actual impedance of the equipment at a certain frequency point and its nominal impedance.

[0003] During field work, the communication operation and maintenance personnel use a high-frequency channel return loss measurement circuit. When measuring, the high-frequency cable needs to be disconnected from the carrier machine on both sides of the high-frequency channel, and the frequency-selective level meter is connected on this side, and the high-frequency cable on the opposite side is terminated with a matching resistor. Since the input impedance of the power line is a complex impedance that changes with frequency, the return loss of the high-frequency channel needs to be measured in the 40-500kHz frequency band with a step size of 10kHz. The input impedance of the current frequency is read from the frequency-selective level meter, and then converted to return loss through a formula.

[0004] This return loss measurement method uses a more complex return loss formula and has more external wiring and connecting devices, making it difficult to measure the return loss of power line carrier lines and equipment. The measurement efficiency is low and it is impossible to ensure the safety and smooth operation of line protection services during icing. Summary of the invention

[0005] The present invention aims to provide a power line carrier return loss measurement auxiliary device, which is applied to the daily maintenance of the power line carrier, reduces the difficulty of the return loss measurement of the power line carrier line and equipment, improves the measurement efficiency, enhances the management level of the power line carrier channel, and further ensures the safety and smoothness of the line protection business during icing.

[0006] To achieve the above-mentioned object, the present invention provides a power line carrier return loss measurement auxiliary device, comprising a high-frequency channel return loss measurement circuit, a combined filter return loss measurement circuit, an oscillator and a frequency selection level meter; the high-frequency channel return loss measurement circuit is a bridge circuit composed of a measurement circuit connected to the input impedance of the high-frequency channel; the combined filter return loss measurement circuit is a bridge circuit composed of a measurement circuit connected to the output end of the combined filter;

[0007] The measuring circuit comprises two R1 resistors, one R2 resistor and a switch; the two R1 resistors are connected, and the R2 resistor is connected to the switch; one R1 resistor is connected to the resistor R2, and the other R1 resistor can be connected to the input impedance of the high-frequency channel or the input impedance of the combined filter; one end of the oscillator is detachably connected between the R1 resistor and the R2 resistor, and the other end of the oscillator is detachably connected between the R1 resistor and the input impedance of the high-frequency channel or the input impedance of the combined filter; the level meter can be respectively connected between the two R1 resistors and between the R2 resistor and the switch.

[0008] Particularly, the high-frequency channel return loss measurement circuit and the combined filter return loss measurement circuit are simplified into the same circuit.

[0009] In particular, the power line carrier return loss measurement auxiliary device is fixed in the device box, and a plurality of connection ports are arranged at the upper end of the device box. The connection heads are inserted into different connection ports, and a frequency-selective level meter and an oscillator are used to realize a plurality of connection modes.

[0010] Particularly, the wiring modes are a wiring mode for measuring high-frequency channel return loss, a wiring mode for measuring combined filter working attenuation, and a wiring mode for measuring combined filter return loss.

[0011] Particularly, the output end of the combined filter is connected with a load impedance and a coupling capacitor in series.

[0012] Particularly, the load impedance is between 300-400 ohms.

[0013] Particularly, the coupling capacitor has a value between 5000 and 10000 pico-farads.

[0014] Particularly, the input impedance of the high frequency channel is 75 ohms.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention designs an auxiliary circuit for measuring return loss of a power line carrier. The circuit has external resistors and connecting wires built into the device, and adds a bridge circuit to simplify the formula calculation of the return loss. The result can be read by a simple calculation during the measurement process, and the external wiring and connecting devices can also be reduced.

[0017] 2. The present invention integrates the designed circuit in the device box. By inserting the wiring heads into different wiring holes of the measuring box, cooperating with the oscillator and the frequency selection table, three measurement functions of high-frequency channel return loss, combined filter working attenuation, and combined filter return loss can be completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0019] Figure 1 A schematic diagram of an embodiment of the present invention applied to a power line carrier circuit;

[0020] Figure 2 A schematic diagram of a high-frequency channel return loss measurement circuit used in an embodiment of the present invention compared with the prior art;

[0021] Figure 3 A schematic diagram of an attenuation measurement circuit using a combined filter in an embodiment of the present invention compared with the prior art;

[0022] Figure 4 A schematic diagram of a return loss measurement circuit using a combined filter in an embodiment of the present invention compared with the prior art;

[0023] Figure 5 This is a circuit diagram for measuring high-frequency channel return loss according to an embodiment of the present invention;

[0024] Figure 6 This is a circuit diagram for measuring filter return loss in combination with an embodiment of the present invention;

[0025] Figure 7 This is an internal circuit diagram of a power line carrier return loss measurement auxiliary device according to an embodiment of the present invention.

[0026] Figure 8 This is an appearance diagram of a power line carrier return loss measurement auxiliary device according to an embodiment of the present invention.

[0027] In the figure: 1-line wave blocker, 2-coupling capacitor, 3-combined filter, 4-high frequency cable, 5-power line carrier, 6-frequency selection level meter. DETAILED DESCRIPTION

[0028] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Many power grid lines are affected by cold waves every winter and are covered with ice. During the period of line icing, the power line carrier, as a backup channel for line protection, is an important means to ensure the safety and smooth operation of protection services. Figure 1 As shown, the power line carrier circuit is composed of a power line carrier machine 5 and a high-frequency channel, wherein the high-frequency channel includes a transmission line, a line wave blocker 1, a coupling capacitor 2, a combined filter 3 and a high-frequency cable 4.

[0032] In field work, the high-frequency channel return loss measurement circuit currently used by communication operation and maintenance personnel is as follows: Figure 2 shown.

[0033] When measuring, the high-frequency cable needs to be disconnected from the carrier machine on both sides of the high-frequency channel, and the frequency-selective level meter 6 is connected to this side, and the high-frequency cable on the opposite side is terminated with a 75Ω matching resistor. Since the input impedance of the power line is a complex impedance that changes with frequency, the return loss of the high-frequency channel needs to be measured in the 40-500kHz frequency band with a step size of 10kHz. The input impedance of the current frequency is read from the frequency-selective level meter and then converted to return loss using formula (1). Formula (1) is:

[0034]

[0035] The circuit diagram for measuring the working attenuation of the combined filter is as follows Figure 3 As shown. When measuring, the high-frequency cable and line side need to be disconnected from the combined filter, the cable side of the combined filter is connected to the oscillator, and the line side is connected to the frequency-selective level meter. The working attenuation of the combined filter is within the 40-500kHz frequency band, and the measurement is performed in steps of 10kHz. The oscillator sends 0db 75 ohms, and the power of the current frequency is read from the frequency-selective level meter.

[0036] The circuit diagram for measuring the return loss of the combined filter is as follows Figure 4 As shown. When measuring, the high-frequency cable and line side need to be disconnected from the combined filter, the cable side needs to be connected to the frequency-selective level meter, and the line side needs to be connected to the equivalent coupling capacitor simulation component and the nominal impedance of the combined filter line side. The return loss needs to be measured in the 40-500kHz frequency band with a step size of 10kHz. The input impedance of the current frequency is read from the frequency-selective level meter and then converted to the return loss using formula (1).

[0037] The embodiment of the present invention is a power line carrier return loss measurement auxiliary device that can integrate three wiring modes, including a high-frequency channel return loss measurement circuit, a combined filter return loss measurement circuit, an oscillator, and a frequency selection level meter. The high-frequency channel return loss measurement circuit is a bridge circuit composed of a measurement circuit connected to the input impedance of the high-frequency channel. The combined filter return loss measurement circuit is a bridge circuit composed of a measurement circuit connected to the output end of the combined filter.

[0038] The measuring circuit includes two R1 resistors, one R2 resistor, and a switch; the two R1 resistors are connected, and the R2 resistor is connected to the switch; one R1 resistor is connected to the resistor R2, and the other R1 resistor can be connected to the input impedance of the high-frequency channel or the input impedance of the combined filter; one end of the oscillator can be detachably connected between the R1 resistor and the R2 resistor, and the other end of the oscillator can be detachably connected between the R1 resistor and the input impedance of the high-frequency channel or the input impedance of the combined filter. The level meter can be connected between the two R1 resistors and between the R2 resistor and the switch.

[0039] In order to simplify the calculation formula of return loss during the measurement process, refer to the laboratory circuit diagram of return loss. The high-frequency channel return loss measurement circuit diagram is as follows: Figure 5 As shown, the circuit diagram of the filter return loss measurement is shown in Figure 6 shown.

[0040] As can be seen from the figure, the measurement circuit is a bridge circuit composed of two R1 resistors, an R2 resistor and the input impedance of the high-frequency channel / combined filter. The balanced output oscillator (internal resistance Ri=0) is connected to the B and D points of the bridge. The A and C points of the bridge are connected to an indirect level meter. The high-frequency cable / combined filter input end is connected to the switch K, and the combined filter output end is connected to the load impedance Rf=R3. The value of R3 should be between 300-400 ohms. Change the frequency of the oscillator, and measure the corresponding levels P1 and P2 when the switch K is opened and closed. This is the return loss: Aw=P1-P2. In addition, the external circuit for measuring the working attenuation of the combined filter is also provided in the power line carrier return loss measurement auxiliary device, that is, the external circuits required for the three measurement functions are integrated in the device. Therefore, the internal circuit diagram of the power line carrier return loss measurement auxiliary device is designed, as shown in the figure. Figure 7 shown.

[0041] As can be seen from the figure, the internal circuit of the auxiliary device mainly includes capacitors, resistors, connecting wires and other devices. This circuit builds external resistors and connecting wires into the device, and adds a bridge circuit to simplify the calculation formula of return loss. The designed circuit is then fixed in the device box, and 11 wiring ports such as X1, X2, and X3 are set on the upper end of the device box. The high-frequency channel characteristic impedance R is 75 ohms, and the value of the resistor R1 combined with the filter characteristic impedance should be between 300-400 ohms; the value of the coupling capacitor C should be between 5000-10000 picofarads. The appearance of the device is as follows Figure 8 shown.

[0042] Insert the wiring head into different wiring ports, and cooperate with the frequency selection table and oscillator to realize three wiring modes, namely, the wiring mode for measuring the return loss of the high-frequency channel, the wiring mode for measuring the working attenuation of the combined filter, and the wiring mode for measuring the return loss of the combined filter, that is, the following three measurement functions are completed:

[0043] (1) Measure the high-frequency channel return loss: (on the opposite side) the core wire and shielding layer of the high-frequency cable are connected to the connection ports X10 and X11. On this side: the shielding layer and core wire of the oscillator are connected to ports X1 and X2 respectively; the shielding layer and core wire of the frequency selector are connected to ports X3 and X4 respectively; the shielding layer of the high-frequency cable is connected to port X5; adjust the oscillator and the frequency selector to the same frequency, the oscillator sends 0db75 ohms, the frequency selector selects 75 ohms and 25Hz, and reads the frequency selector reading P1 at this time; the core wire of the high-frequency cable is connected to port X6, and the frequency selector reading P2 is read at this time; P1-P2 is the value of the high-frequency channel return loss.

[0044] (2) Measure the working attenuation of the combined filter: the shielding layer and core wire of the oscillator are connected to the shielding layer of the high-frequency cable of the combined filter and port X10 respectively; the core wire of the high-frequency cable of the combined filter is connected to port X11; the line-side ground terminal and line-side port of the combined filter are connected to the device ports X7 and X9 respectively; the shielding layer and core wire of the frequency selector are connected to the line-side ground terminal of the combined filter and device port X8 respectively; the oscillator is selected to be 0db, 75 ohms, and the frequency selector is selected to be infinite and 25Hz. The reading P4 of the frequency selector is the channel loss of the combined filter.

[0045] (3) Measure the return loss of the combined filter: the shield layer and core wire of the oscillator are connected to the device ports X1 and X2 respectively; the shield layer and core wire of the frequency selector are connected to the device ports X3 and X4 respectively; the ground terminal and line side of the combined filter are connected to the device ports X7 and X9 respectively; the shield layer of the high-frequency cable of the combined filter is connected to the device port X5; at this time, adjust the oscillator and the frequency selector to the same frequency, so that the oscillator sends 0db 75 ohms, the frequency selector selects 75 ohms 25Hz, and the frequency selector reads the frequency selector reading P5 at this time; the high-frequency cable core wire of the combined filter is connected to the device port X6, and the frequency selector reading P6 at this time is read; P5-P6 is the return loss value of the combined filter.

[0046] The original power line carrier measurement used many connecting wires and devices, and the wiring was complicated. At the same time, the original return loss measurement result was the value of characteristic impedance. The power line carrier return loss measurement auxiliary device integrates three wiring modes, which can reduce the devices and connecting wires used in power line carrier measurement, simplify the return loss formula calculation, and directly obtain the return loss value through simple calculation during the measurement process, so as to quickly judge the quality of the power line carrier channel and equipment.

[0047] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A power line carrier return loss measurement auxiliary device, characterized in that: It includes a high-frequency channel return loss measurement circuit, a combined filter return loss measurement circuit, an oscillator and a frequency selection level meter; the high-frequency channel return loss measurement circuit is a bridge circuit composed of a measurement circuit connected to the input impedance of the high-frequency channel; the combined filter return loss measurement circuit is a bridge circuit composed of a measurement circuit connected to the output end of the combined filter; The measuring circuit comprises two R1 resistors, one R2 resistor and a switch; the two R1 resistors are connected, and the R2 resistor is connected to the switch; one R1 resistor is connected to the resistor R2, and the other R1 resistor can be connected to the input impedance of the high-frequency channel or the input impedance of the combined filter; one end of the oscillator is detachably connected between the R1 resistor and the R2 resistor, and the other end of the oscillator is detachably connected between the R1 resistor and the input impedance of the high-frequency channel or the input impedance of the combined filter; the level meter can be respectively connected between the two R1 resistors and between the R2 resistor and the switch.

2. The power line carrier return loss measurement auxiliary device according to claim 1, characterized in that: The high-frequency channel return loss measurement circuit and the combined filter return loss measurement circuit are simplified into the same circuit.

3. The power line carrier return loss measurement auxiliary device according to claim 1, characterized in that: The power line carrier return loss measurement auxiliary device is fixed in the device box. Several wiring ports are arranged on the upper end of the device box. The wiring heads are inserted into different wiring ports, and several wiring modes are realized by cooperating with the frequency-selective level meter and the oscillator.

4. The power line carrier return loss measurement auxiliary device according to claim 1, characterized in that: The wiring modes include a wiring mode for measuring high-frequency channel return loss, a wiring mode for measuring combined filter working attenuation, and a wiring mode for measuring combined filter return loss.

5. The power line carrier return loss measurement auxiliary device according to claim 1, characterized in that: The output end of the combined filter is connected with a load impedance and a coupling capacitor in series.

6. The power line carrier return loss measurement auxiliary device according to claim 1, characterized in that: The load impedance is between 300-400 ohms.

7. The power line carrier return loss measurement auxiliary device according to claim 1, characterized in that: The coupling capacitor has a value between 5000 and 10000 pico-farads.

8. The power line carrier return loss measurement auxiliary device according to claim 1, characterized in that: The input impedance of the high frequency channel is 75 ohms.

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