JP6872862B2 - Train radio system - Google Patents

Description

The present disclosure relates to a lightning arrester and a train radio system equipped with the arrester, and relates to a technique for protecting a protected object from an excessive current such as a lightning surge current.

In recent years, lightning damage (damage caused by lightning surge current) has been on the rise due to the effects of abnormal weather and the like, and there is an increasing need to take lightning countermeasures with lightning arresters for wireless repeaters as well. The wireless repeater is a power superimposition device that separates the superimposed wireless signal and the AC power supply, a transformer that converts the voltage value of the AC power supply, a signal amplifier that amplifies the wireless signal, and the AC power supply and the wireless signal again. It is provided with a power superimposing device for superimposing. Therefore, in a wireless repeater in which lightning countermeasures are not taken, there is a possibility that each of the above components may be damaged by a lightning surge current.

For example, Patent Document 1 discloses a lightning arrester that protects an AC power source by using MOV (Metal Oxide Varistor).

Japanese Patent No. 5278846

However, the technique disclosed in Patent Document 1 cannot be directly applied to a wireless repeater. In other words, MOV has a large capacitance and attenuates high-frequency signals even during normal operation (when no lightning surge current is generated due to lightning strikes), so radio signals, which are high-frequency signals, are appropriately relayed by a repeater. Can not do it.

The present disclosure has been made in view of such a situation, and provides a technique for protecting all the components of a radio repeater used in a train radio system from lightning damage.

In order to solve the above problems, the lightning arrester according to the present disclosure is a lightning arrester for protecting a protected object from an excessive current, and includes an inner conductor and an outer conductor for propagating a signal input to the protected object, and first. The switching element of the above, the second switching element, and the ground terminal are provided. Here, the first switching element and the second switching element are connected in series between the inner conductor and the outer conductor. Further, the operating voltage of each of the first switching element and the second switching element is set to be larger than the voltage value of the power supply included in the signal propagating in the inner conductor and the outer conductor. Further, the capacitance of the first switching element is smaller than the capacitance of the second switching element. Further, the combined capacitance of the first switching element and the second switching element is set to the capacitance at which the signal input in the normal state propagates through the inner conductor and the outer conductor without any trouble in attenuation. There is.

Further features relating to this disclosure will become apparent from the description herein and the accompanying drawings. In addition, the aspects of the present disclosure are achieved and realized by the combination of elements and various elements, the detailed description below, and the aspects of the appended claims.

It should be understood that the description herein is merely a exemplary example and is not intended to limit the claims or applications of the present disclosure in any way.

According to the present disclosure, all the components of the radio repeater used in the train radio system can be protected from lightning damage.

It is a figure which shows the schematic configuration example of a train radio system 1. It is a figure which shows the internal structure example of a wireless repeater 3. It is a figure which shows the configuration example around the wireless repeater 3 which installed the lightning arrester 6 by this embodiment. It is a figure which shows the appearance structure of the lightning arrester 6 by this embodiment. It is a figure which shows the circuit structure of the lightning arrester 6 by this embodiment. It is a figure which shows the discharge path of the lightning surge current during the operation of the lightning arrester 6 by this embodiment.

The present disclosure relates to a "coaxial lightning arrester for a train radio system" and a "train radio system equipped with this lightning arrester" for protecting a radio repeater in a train radio system from an excessive current such as a lightning surge current. In the lightning arrester, the inner conductor and the outer conductor have a coaxial configuration, and two switching elements (for example, MOV and GDT) are connected in series between the inner conductor and the outer conductor. Also, the outer conductor is grounded. The lightning arrester is inserted into each of the front stage (input side) and the rear stage (output side) of each radio repeater in the train radio system. Then, when the excessive current flows into the lightning arrester, the two switching elements operate and become in a low resistance state, so that the excessive current is transmitted from the inner conductor to the outer conductor and discharged to the ground. By doing so, it becomes possible to protect the wireless repeater to be protected from lightning damage. In the present embodiment described below, the lightning arrester is inserted into the front stage and the rear stage of the wireless repeater, respectively.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the attached drawings, functionally the same elements may be displayed with the same number. The accompanying drawings show specific embodiments and implementation examples in accordance with the principles of the present disclosure, but these are for the purpose of understanding the present disclosure and in order to interpret the present disclosure in a limited manner. Not used.

In this embodiment, the description is given in sufficient detail for those skilled in the art to implement the present disclosure, but other implementations and embodiments are also possible and do not deviate from the scope and spirit of the technical idea of the present disclosure. It is necessary to understand that it is possible to change the structure / structure and replace various elements. Therefore, the following description should not be construed as limited to this.

<Outline configuration of train radio system>
FIG. 1 is a diagram showing a schematic configuration example of a train radio system 1. In FIG. 1, the Shinkansen is taken as an example, but it can also be applied to conventional trains.

The train radio system 1 provides an LCX (Leaky Coaxial cable) between the Shinkansen 5 and the base station (for example, a data server or a client device may be connected upstream of the base station) 2. The communication is realized by using LCX4, which is a leaky coaxial cable having an antenna function, which is a system for communicating by using. As an example, the train radio system 1 includes a base station 2 that outputs a radio signal, and a plurality of radio repeaters 3 that are connected to the LCX4 and are arranged at a fixed distance. Since the leakage coaxial cable LCX4 is installed along the rail of the Shinkansen 5, the Shinkansen 5 can appropriately acquire a radio signal from the LCX4 and transmit information to the LCX4. A mobile station device (for example, a wireless communication device) or the like is mounted on the Shinkansen 5.

The reason why the plurality of radio repeaters 3 are arranged at regular distance intervals is that the radio signals are attenuated while being transmitted via the LCX4, and therefore the attenuated radio signals are amplified by each radio repeater 3. is there.

A superimposed signal generated by superimposing the above radio signal (for example, a high frequency signal in the 400 MHz band) and a power source for driving the wireless repeater 3 (for example, an AC power source of 400 to 430 V) is transmitted to the LCX4. Will be done.

In the train radio system 1, for example, by using a digital communication method, it is possible to increase the number of radio lines and improve the transmission speed even within the same frequency band as the conventional analog system. ing.

<About the internal configuration of the wireless repeater and the effect of lightning surge current>
FIG. 2 is a diagram showing an example of the internal configuration of the wireless repeater 3. The wireless repeater 3 includes two power superimposing devices 32, a transformer 33, and a signal amplifier 34 in the wireless repeater housing 31, and the wireless repeater housing 31 is installed on the ground.

The power superimposition device 32 on the signal input side separates the superimposition signal transmitted in the LCX4 into an AC power supply and a wireless signal. The transformer 33 converts the voltage value of the AC power supply obtained by separating the superimposed signals by the power superimposing device 32 (stepping down to the operating voltage of the signal amplifier 34), supplies the voltage to the signal amplifier 34, and supplies the electric power on the signal output side. The AC power supply obtained separately is supplied to the superimposition device 32 as it is. The signal amplifier 34 amplifies and outputs the radio signal separated by the power superimposing device 32 on the signal input side. The power superimposition device 32 on the output side superimposes the radio signal amplified by the signal amplifier 34 and the AC power supply supplied from the transformer 33 again and outputs the power to the LCX4.

When the wireless repeater 3 having such a configuration is not provided with lightning countermeasures, the following three routes are conceivable for the lightning surge current to enter the wireless repeater 3.
i) A lightning surge current flows through the communication line of the wireless repeater 3. In this case, the damaged devices are the power superimposition 32 and the signal amplifier 34.
ii) A lightning surge current flows through the power supply line of the wireless repeater 3. In this case, the damaged devices are the power superimposition 32, the transformer 33, and the signal amplifier 34.
iii) Dielectric breakdown occurs between the power superimposing device 32 and the housing grounding 35, and a lightning surge current flows from the power superimposing device 32 to the housing grounding 35. In this case, the device to be damaged is the power superimposition device 32.

Since the polarity of lightning is both positive and negative, there are cases where a lightning surge current invades from the ground and escapes to LCX4.

In the above case, if no lightning countermeasures are taken against the wireless repeater 3, the wireless repeater 3 is damaged and must be replaced. The number of replacements and replacement work of the wireless repeater 3 will be enormous, the operation of the Shinkansen 5 will be hindered, and the financial damage may be extremely large.

Therefore, as proposed in the embodiment of the present disclosure, lightning arresters are installed on the input side and the output side of each wireless repeater 3 to prevent the intrusion of lightning surge current.

<Wireless repeater with lightning arrester>
FIG. 3 is a diagram showing a configuration example around the wireless repeater 3 in which the lightning arrester 6 according to the present embodiment is installed. Since the configuration and operation of the wireless repeater 3 have been described above, they will be omitted here.

As shown in FIG. 3, the lightning arrester 6 according to the present embodiment is installed (inserted) on each of the signal input side and the signal output side of the wireless repeater 3. When the lightning arrester 6 is attached to the wireless repeater 3, the intrusion of the lightning surge current generated by the lightning strike on the LCX4 into the wireless repeater 3 is blocked by the lightning arrester 6 and discharged to the ground via the lightning arrester 6. To.

In this way, it is possible to prevent the lightning surge current from entering the wireless repeater 3, so that all the components of the wireless repeater 3 can be protected from lightning damage. When the lightning surge current is discharged to the ground, the reception of the superimposed signal (radio signal + AC power supply) by the wireless repeater 3 is also blocked at the same time, but the blocked period is very short (for example,). Since it is about 1 ms), it is not a level that causes problems in train operation.

<Appearance configuration of lightning arrester>
FIG. 4 is a diagram showing an external configuration of the lightning arrester 6 according to the present embodiment. However, some of the internal configurations are shown.

The lightning arrester 6 includes an inner conductor 61, an outer conductor 62, a GDT (Gas Discharge Tube) 63 and a MOV (Metal Oxide Varistor) 64 arranged in series between the inner conductor 61 and the outer conductor 62, and a ground terminal 65. And have.

Since MOV is generally used for the circuit of the lightning arrester installed in the power system, MOV64 is also used for the lightning arrester 6 installed in the LCX4 of the train radio system 1. However, not only the AC power supply but also the high frequency radio signal is superimposed on the LCX4. Since the MOV64 has a large capacitance (generally around 10000 pF) and greatly attenuates the high frequency signal, the circuit of the MOV alone cannot pass a radio signal which is a high frequency signal. Therefore, in the embodiment of the present disclosure, a GDT having a small capacitance (for example, one having a capacitance of 10 pF or less) 63 is connected in series with the MOV64 (the order of connection does not matter) to reduce the overall capacitance (for example, 5 pF or less). By doing so, wireless signals can also be passed.

A coaxial cable for relay is interposed between the LCX 4 and the wireless repeater 3, although not shown. A connector for connection is provided at one end (LCX4 side) and the other end (wireless repeater 3 side) of the coaxial cable for relay, and when the lightning arrester 6 is attached, the coaxial of the lightning arrester 6 is provided. The cable attachment portion is connected to the other end of the coaxial cable for relay, and the wireless repeater attachment portion of the lightning arrester 6 is connected to the coaxial cable attachment portion of the wireless repeater 3.
As described above, the lightning arrester 6 has a configuration that can be easily attached.

Although GDT63 and MOV64 are used in this embodiment, any element having the same properties as GDT63 and MOV64 can be applied. The features of each are shown below.
(1) Features of MOV (i) A switching element that has the property that the electrical resistance drops sharply when a voltage higher than the operating voltage is applied (ii) The operating voltage is AC430V or higher (iii) Prevention of follow-on current Therefore, it has the characteristic that it becomes a constant voltage after operation (iv) It can withstand a large lightning surge current (2) Features of GDT (i) It is a switching element that discharges when a voltage higher than the operating voltage is applied (ii) The operating voltage is AC430V or higher (iii) It has the characteristic of shifting to low resistance (low voltage) after operation (iv) It can withstand a large lightning surge current (v) The capacitance between terminals is very small and high frequency The signal can be propagated without any attenuation hindrance.

<Internal circuit configuration of lightning arrester>
FIG. 5 is a diagram showing a circuit configuration of the lightning arrester 6 according to the present embodiment. The lightning arrester 6 includes an inner conductor 61, an outer conductor 62, a GDT 63, and a MOV 64. The GDT 63 and MOV 64 form a series circuit between the inner conductor 61 and the outer conductor 62. The inner conductor 61 is connected to the LCX4 and the wireless repeater 3. Further, the outer conductor 62 is grounded (via the ground terminal 65).

When the lightning arrester 6 is not operating, that is, when the lightning surge current is not flowing (normal), the voltage value of the AC power supply (for example, AC400V) included in the superimposed signal is the operating voltage of GDT63 and MOV64, respectively. Smaller than Therefore, the GDT 63 and MOV 64 do not operate, and the superimposed signal (radio signal + AC power supply) transmitted by the LCX4 passes through the lightning arrester as it is and is input to the wireless repeater 3.

Further, in the combined capacitance of GDT63 and MOV64, when the lightning arrester 6 is not operating (normal time), a radio signal (for example, a high frequency signal in the 400 MHz band) causes the inner conductor 61 and the outer conductor 62 of the lightning arrester 6 to be used. It must be set to a value that propagates without hindrance to attenuation.

<Discharge path of lightning surge current during lightning arrester operation>
FIG. 6 is a diagram showing a discharge path of a lightning surge current during the operation of the lightning arrester 6. The lightning surge current propagating through the LCX4 directly penetrates into the internal conductor 61 of the lightning arrester 6. When a lightning surge current is generated, the applied voltage is, for example, 1500 V or more (it becomes equal to or more than the total value of the operating voltages of GDT 63 and MOV 64), so that the switches of GDT 63 and MOV 64 are turned on. When the switches of both elements are turned on, the resistance becomes low, so that a lightning surge current easily flows to the element side. The lightning surge current that has passed through the GDT 63 and MOV 64 is transmitted through the outer conductor 62 and escapes from the outer conductor 62 to the ground (via the ground terminal 65). Since the lightning voltage is applied between the LCX4 and the ground (earth) in the first place, it has the property of escaping to the ground. Therefore, if switching with respect to the ground, the lightning surge current will naturally flow to the ground.

Then, after the lightning surge current is discharged, the lightning arrester 6 is self-recovering because the switches of GDT63 and MOV64 are turned off (return to the high resistance state).

<Summary>
The lightning arrester 6 according to the embodiment of the present disclosure includes an inner conductor 61 and an outer conductor 62 for propagating a superimposed signal input to the wireless repeater, a first switching element (for example, GND63), and a second switching element (for example, GDT63). For example, it includes a MOV64) and a grounding terminal (grounding terminal 65). Here, the inner conductor 61 and the outer conductor 62 are coaxially configured, and the inner conductor of the leakage coaxial cable (LCX4) is connected to the inner conductor 61 of the lightning arrester 6 via the relay coaxial cable, and the outer conductor of the lightning arrester 6 is connected. The outer conductor of the LCX4 is connected to the 62 via a relay coaxial cable. Further, the first switching element and the second switching element are connected in series between the inner conductor 61 and the outer conductor 62 of the lightning arrester 6. Further, the operating voltage of each of the first switching element and the second switching element is defined to be larger than the voltage value of the power supply included in the superimposed signal propagating through the inner conductor 61 and the outer conductor 62 of the lightning arrester 6. Further, the capacitance of the first switching element is smaller than the capacitance of the second switching element. The combined capacitance of the first switching element and the second switching element is set to a capacitance such that the superimposed signal propagates through the inner conductor and the outer conductor without any problem in attenuation under normal conditions. There is. The combined capacitance of the first switching element and the second switching element is preferably 5 pF or less, but this is just an example, and the superimposed signal propagates through the inner conductor and the outer conductor without any problem in attenuation. It may be a capacitance. In the lightning arrester 6 having such a configuration, when an excessive voltage (lightning surge voltage) is applied, the first switching element and the second switching element are turned on, resulting in a low resistance state. Then, the lightning surge current is transmitted from the inner conductor 61 to the outer conductor 62 via the first switching element and the second switching element, and is discharged from the ground terminal to the ground. By doing so, since a lightning surge does not enter the wireless repeater 3, it is possible to take lightning countermeasures for all the components (all devices) in the wireless repeater 3. Further, since the lightning arrester 6 is composed of a coaxial connector, it can be easily attached and detached, and the labor of construction (including maintenance and replacement) can be reduced. Further, in the train radio system, the lightning arrester 6 needs to be installed only at the introduction outlets (input side and output side) of the radio repeater 3, so that the space inside the radio repeater 3 is not squeezed. Can also be expected.

1 Train radio system 2 Base station 3 Radio repeater 4 LCX
5 Shinkansen 6 Lightning arrester 31 Wireless repeater housing 32 Power superimposing unit 33 Transformer 34 Signal amplifier 35 Housing grounding 61 Internal conductor 62 External conductor 63 GDT
64 MOV
65 ground terminal

Claims (1)

A train radio system for communicating radio signals with trains.
With multiple wireless repeaters,
Multiple lightning arresters located on the input side and output side of each wireless repeater,
A leaky coaxial cable connected to the plurality of lightning arresters,
A base station that inputs / outputs a superposed signal generated by superimposing an AC power supply and a wireless signal to the leaky coaxial cable is provided.
The radio signal included in the superimposed signal is communicated between the leaky coaxial cable and the train.
The arrester is arranged to protect the radio repeater from excessive current.
An inner conductor and an outer conductor for propagating a signal input to the wireless repeater, and
The first switching element and
The second switching element and
With a ground terminal,
The first switching element and the second switching element are connected in series between the inner conductor and the outer conductor.
The operating voltage of each of the first switching element and the second switching element is larger than the voltage value of the power supply included in the signal propagating through the inner conductor and the outer conductor.
The capacitance of the first switching element is smaller than the capacitance of the second switching element.
The combined capacitance of the first switching element and the second switching element is set to a capacitance at which the signal propagates through the inner conductor and the outer conductor without any problem in attenuation under normal conditions. Ori,
The combined capacitance of the first switching element and the second switching element is 5 pF or less.
A train radio system in which the operating voltage of the first switching element and the second switching element is AC430V or higher.

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