JP2003260963A - Rail potential reduction AC feeding circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a rail electric potential from rising even if an AT territory is lengthened in an AT electric current feeding system. <P>SOLUTION: Low resistance grounding is carried out at a CPW point where a protective line and the impedance bond neutral point are connected to each other between the point (AT point) where an automatic transformer (AT) is installed and another AT point. As a result, when an electric train reaches the center between AT points, the maximum potential itself generated in the rail at the position is reduced to approximately one fourth compared with that in the case where any measures such as CPW and grounding are not taken. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field of technology for reducing a rail potential generated when an electric vehicle is running in an autotransformer (AT) feeding system of an electric railway.

[0002]

2. Description of the Related Art In an electric railway, a rail is configured as a return circuit and an electric car current flows, so that a rail potential is generated due to a characteristic impedance of the rail and a load current. FIG. 7 shows a simplest diagram of the direct feeding system composed of only the trolley wire and the rail. (A) Hakiden system diagram,
(B) is a rail current distribution map, and (c) is a rail potential distribution map. The electric car 11 is fed from the substation 10 via the trolley wire 2 and returns to the substation 10 via the rail 3. Substation 10
Is the point O, the position of the electric vehicle 11 is the point Q (load point), and the distance from the point O to the point Q is l ₁ , the rail current I _{x at the} point x from the point O is the mathematical formula 1 It is represented by.

[0003]

[Equation 1]

FIG. 7 (b) shows the current distribution represented by the equation (1). The rail potential is obtained by multiplying the rail current by the characteristic impedance Z ₀ of the rail. Since n ₀ I in Expression 1 is a component that flows by the electromagnetic induction action of the electric line current I, it does not contribute to the rail potential at all. Therefore, the rail potential V x at the point _x is as shown in Expression 2.

[0005]

[Equation 2]

The rail potential V _{Q at the} point Q (load point) where the electric vehicle 11 is present can be obtained by substituting x = l ₁ in the equation 2, and as a result, the equation 3 becomes the highest.

[0007]

[Equation 3]

On the other hand, rail potential V _O of the O point is the location of the substation 10 is because it is sufficient substituting x = 0 in Equation 2, the result is as shown in Equation 4.

[0009]

[Equation 4]

Comparing this with the potential at the load point in Equation 3, it can be seen that the magnitude is the same and the polarity is reversed. FIG. 7C shows this. FIG. 8 shows the case of the AT feeding system. In the AT feeding system, the load current I flowing through the electric vehicle 11 is an autotransformer before and after the traveling direction (hereinafter referred to as AT
Also, the distribution of the rail potential is different from that in the case of the direct feeding system. However, for example, the electric car 11 has a center Q between ATs (distance l ₂ ) as shown in FIG. 8A. rail potential is the same as the feeding circuit system directly instead of l ₁ of equation 3 at the point Q by substituting l _2/2 is expressed by equation 5 when you are in point.

[0011]

[Equation 5]

The value of the above equation 5 is the CPW connecting the rail 3 and the protection line (also referred to as PW) 7 in FIG. 8A.
Although it is a value when there is no 8, since the rail is normally connected to the protective line through the impedance bond at the center point between AT and AT, the value is reduced to about 70% of the value of Expression 6. On the other hand, the rail potential at the AT position, that is, at the P point and the R point when the electric vehicle 11 is at the Q point as shown in (a), is that the load current I is shunted toward the front and rear ATs and flows to the rail. , And the shunt effect on PW7, load point (Q
The value is about half or less with the opposite polarity compared to the rail potential of (dot). The rail potential in such a state is shown in FIG.
It becomes like (b).

The above rail potential value does not cause any practical problem in the conventional line because the load current is small. On the other hand, in the Shinkansen, since the load current is large, the rail potential may be high immediately after passing the train, but the Shinkansen Special Law prohibits general entry and does not perform maintenance work during business hours. Therefore, no problem has occurred. From the above, no particular rail potential suppression measures have been implemented in conventional general sections.

[0014]

However, in the AT feeder circuit to be constructed in the future, the AT interval becomes long,
Since a long section exceeding 15 km is assumed,
There is a problem that the rail potential becomes higher and a high voltage is applied to the insulating pad between the rail and the sleeper, which is used for electrically insulating the track circuit of the signal, and the life is shortened.

Further, when an electric train runs on one line in an AT feeder circuit composed of an upper line and a lower line in the future and the other line goes into the track site to perform work, the high potential of the rail causes various dangers. There is a problem with it.

In view of the above problems, an object of the present invention is to provide means for suppressing an increase in rail potential in the AT feeding system.

[0017]

The present invention has the following means for achieving the above object. The first configuration of the present invention is to set the feeding voltage of the substation higher than the power line voltage and to install the autotransformer (A
An AT feeding circuit that lowers the rail line voltage by T) and supplies electric power to the electric car.
A rail potential reducing AC feeding circuit having a grounding circuit for grounding a neutral point of an impedance bond at a TW point and a CPW point connecting a rail and a protection line (PW) at the middle thereof.

According to a second structure of the present invention, in the first structure, an elevated leg rebar is used in an elevated section and a tunnel rebar or a roadbed rebar is used in a tunnel section as a ground electrode of a ground circuit. A rail potential reducing AC feeding circuit characterized by: A third configuration of the present invention is the rail potential reducing AC feeding circuit according to the first configuration, wherein an embedded ground wire is used as a ground electrode of the ground circuit.

In a fourth structure of the present invention, in the first, second or third structure, in a section in which the DC electric railway is parallel, in order to prevent electrolytic corrosion, an impedance bond neutral point and a ground electrode. A rail potential reducing AC feeding circuit characterized in that a series resonance circuit composed of a capacitor and a reactor is provided between and.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION For simplification of description, consider a rail potential when a rail is grounded near a substation in a direct feeding system as shown in FIG. FIG. 1A is a diagram showing a feeder system. The position of the substation 10 is O, the position of the electric vehicle 11 is P (load point), and the distance between O and P is l ₁ . The load current flowing through the electric vehicle 11 is I.
(B) is a figure which shows the electric current distribution of a rail, (c) is a figure which shows a rail electric potential distribution.

Now, near the O point, at the Q point at the distance a, the rail 3
Consider the case where is grounded via the grounding resistance R _g . In this case, the current attenuated through the admittance of the rail 3 transmits and reflects at point Q. In FIG. 1, when the current flows from the right side of the Q point, the impedance Z viewed from the Q point is that the characteristic impedance Z ₀ of the rail on the left side of the Q point and the ground resistance R _g are in parallel, so It becomes like 6.

[0022]

[Equation 6]

The characteristic impedance Z ₀ of the rail is from the point Q to the right, and impedance mismatching occurs at the point Q, so that part of the current wave traveling from the right is reflected. The reflection coefficient m is given by Equation 7.

[0024]

[Equation 7]

At the position O of the substation 10, the current wave traveling to the left is-(1-n ₀ ) I / 2 from the substation 10 and the current wave (1-n ₀ ) Iexp (-from the P point. γl ₁ ) / 2, and therefore the current wave I _Q arriving at the Q point from the right side is expressed by Equation 8.

[0026]

[Equation 8]

Next, a current wave I reflected at point Q and traveling to the right
_QR is obtained by multiplying the current wave I _Q in Equation 8 by the reflection coefficient m, and thus is represented by Equation 9.

[0028]

[Equation 9]

Therefore, the rail current I _a obtained by combining the respective current waves I _Q and I _QR at the point _Q is expressed by the formula 10 when the right direction of the current is expressed as positive.

[0030]

[Equation 10]

Next, the voltage V _{a at the} point Q is obtained by multiplying the current by the characteristic impedance Z ₀ . However, since the voltage has the same direction regardless of the current flow direction, the sign of the current traveling to the left is +. Therefore, it becomes like Formula 11.

[0032]

[Equation 11]

When the ground is completely grounded at the point Q, that is, when the ground is made at R _g = 0, the reflection coefficient m is m = -1 from the formula 7, and therefore the formula 1
From 1, V _a becomes 0. On the contrary, when the point Q is not grounded at all, that is, R _g = ∞, the reflection coefficient m is
Since = 0, the voltage V _{a at the} point Q is expressed by Expression 12 from Expression 11.

[0034]

[Equation 12]

As described above, it can be seen that the rail potential at the ground point Q becomes lower as the ground resistance R _g becomes smaller, and V _a = 0 at R _g = 0. That is, the rail has resistance R _g
If it is grounded at, the rail potential can be suppressed. However, as shown in (c) of FIG.
The reduction effect decreases as the distance from the point increases, and the maximum voltage is obtained at the load point. Therefore, in order to reduce the rail potential over the entire feeder circuit, multi-point grounding in which the rail is grounded every several kilometers is effective.

[0036]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a conceptual diagram of multipoint grounding in an AT feeding circuit. The rail has a closed section where only one train can enter, and this is called a track circuit. Considering the detection of rail breakage, the conductors connected in parallel to the track circuit 5 need at least two track circuits, and considering the margin, three track circuits or more are required.

That is, the rail 3 is connected in parallel,
The protection line 7 for detecting the insulator line of the electric railway is separated by three or more track circuits and is connected to the neutral point of the impedance bond 4 of the rail 3 by the CPW 8. Similarly, grounding the impedance bond 4 of the rail 3 forms a parallel circuit with the track circuit 5, so that it is necessary to separate the track circuit 5 by at least three track circuits as in the CPW 8.

Therefore, the rail impedance bond 4
It is not always necessary to ground CP at the CPW location, but in practice grounding at the CPW location will reduce the parallel locations of the track circuit, and will be easier to implement. Further, for example, when the CPW8 and the grounding position are at the same position, the position is generally one AT position and one position in the middle of the AT position, but if the AT interval becomes long, the track circuit condition is allowed. If so, two or three locations are possible.

FIG. 3 is a diagram showing the relationship between the AT feeding circuit, the position (load point) of the electric vehicle, and the rail potential at that position. (A) is a feeding system diagram. (B) is (a)
The position of the electric vehicle 11 in the feeding system and the rail potential at that position are shown. (A) A, B, C, ... showing the position on the rail 3 and (b) A, B, C, on the horizontal axis.
Corresponds to.

The solid curve in (b) is the CPW in (a)
8 shows a change in rail potential in the case where 8 and the ground circuit 9 are not provided at all. The rail potential at the point where the electric car is at the point A, that is, AT1, is the lowest, and as the electric vehicle moves to the right, the rail potential at the position of the electric car rises, and at the point B, that is, AT1 and AT1. It becomes the maximum at the intermediate point of, and becomes the rail potential of the above-mentioned formula 5. Intermediate point (point B)
After passing, the curve decreases in a substantially symmetrical curve, and becomes the minimum at point C which is the position of AT1. This is the same as the potential at point A.

After passing point C, it begins to rise again, and the next A
It becomes maximum at the midpoint between the position of T1 (point F). here,
Since the distance to the intermediate point is longer than the distance from the point A to the point B, the maximum value at the intermediate point is larger than the value at the point B, as can be seen from Equation 5. When passing through the intermediate point, the curve is almost symmetrical and drops to point F.

Next, the potentials when the points A to F are connected to the protection line 7 by the CPW 8 are as shown by the dotted curve below the solid curve. In this case, the curves are dented at the points B, D, and E, and the maximum value is reduced to about 70% as compared with the case where no countermeasure is taken (in the case of the solid curve).

Further, when each of the points A to F is grounded by the grounding circuit 9, a dotted curve further below is obtained, and the rail potential differs depending on the circuit conditions, but it is about 4 minutes compared to the case without any countermeasure. Reduced to 1 or less. By thus grounding the rail at multiple points, the rail potential can be reduced.

Further, since it is possible to reduce the rail potential by lowering the impedance of the rail circuit, it is conceivable to implement a cross bond connecting the rails of the upper and lower lines in the double-track section. FIG. 4 shows an example of a cross bond between rails on upper and lower lines in a double track section. This is an AT as shown in FIG.
When the feeder circuits are provided in parallel with each other in the upper and lower lines, the points A, C, and F are connected to each other, and the ground circuit 9 is commonly used.

Further, the smaller the ground circuit resistance R _{g at} each ground point, the greater the potential reduction effect. As an example of such a ground electrode, it is conceivable to use the reinforcing bar of the elevated leg in the elevated section, or to use the tunnel reinforcing bar or the roadbed reinforcing bar in the tunnel section. In these cases,
A low resistance ground electrode of 1 to several Ω can be obtained. FIG. 5 shows an example of a reinforcing bar used as a ground electrode. (A) is an example of utilizing the reinforcing bar of an elevated leg. The conductor of the insulated wire is welded to the reinforcing bar in the underground part of the elevated leg by brass brazing to form the ground electrode. (B) is a case of the tunnel section, and the tunnel reinforcing bars or the roadbed reinforcing bars stretched in the ground of the roadbed are used as the ground electrode as in (a). Also, it may be connected to a buried ground wire that provides a sufficiently low ground resistance.

When the DC electric railway is parallel to the feeding circuit of the AC electric railway in close proximity, if it is directly grounded, the DC current is shunted to the rail of the AC feeding circuit, which causes electrolytic corrosion. Therefore, as shown in FIG. 6, it is sufficient to ground the rail through a series resonance circuit 15 which is composed of a series circuit of a capacitor 13 and a reactor 14 and which cuts a direct current and has a reduced impedance with respect to an alternating current.

At this time, if the feeding frequency is f hertz, the capacitance of the capacitor 13 is C farad, and the inductance of the reactor 14 is L henry, the values of C and L are given by Equation 13
You can choose to satisfy.

[0048]

[Equation 13]

[0049]

As described above, the rail potential reducing AC feeding circuit according to the present invention has the CP at the AT position and the CP in the middle thereof.
Since the neutral point of the impedance bond is grounded at the W point, the rail potential can be reduced, and as a result, the AT interval can be extended, and in the double-track section composed of the upper and lower lines. , Even if the rails of the upper and lower lines are cross-bonded at the CPW point, the rail potential is low, so there is an advantage that the work on the other line is possible even if the electric car is running on one line. .

[Brief description of drawings]

FIG. 1 is a diagram showing a feeding system, a rail current distribution, and a rail potential distribution in a direct feeding system.

FIG. 2 is a conceptual diagram of multipoint grounding in an AT feeding circuit.

FIG. 3 is a diagram showing a relationship between an AT feeding circuit and a rail potential at a position (load point) of an electric vehicle.

FIG. 4 is a diagram showing an example of a cross bond between rails of upper and lower lines in a double-track section.

FIG. 5 is a diagram showing an example of a ground electrode.

FIG. 6 is a diagram showing an example in which a series resonance circuit for preventing electrolytic corrosion is inserted in a ground circuit from a neutral point of an impedance bond.

FIG. 7 is a diagram showing a feeding system of a direct feeding system, a rail current distribution, and a rail potential distribution.

FIG. 8 is a diagram showing a rail potential distribution when an AT feeding system and an electric vehicle are located in the center between ATs.

[Explanation of symbols]

1 autotransformer (AT) 2 trolley wire 3 rails 4 impedance bond 5 track circuits 6 electric wire 7 Protection line (PW) 8 CPW 9 Ground circuit 10 substation 11 electric cars 12 cross bond 13 capacitors 14 Reactor 15 Series resonance circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasushi Hisami             38-8, Hikarimachi, Kokubunji, Tokyo 38 Foundation             Corporate Railway Technical Research Institute (72) Inventor Yoshinobu Yoshinobu             1-1-1, Shibaura, Minato-ku, Tokyo Stock market             Company Toshiba (72) Inventor Takao Masuyama             1-1-1, Shibaura, Minato-ku, Tokyo Stock market             Company Toshiba

Claims (4)

[Claims] 1. The electric power supply voltage for a substation is set to be higher than an electric line voltage, and is stepped down to an electric line voltage by an autotransformer (AT) installed at a predetermined distance along a line to supply electric power to an electric car. An AT feeding circuit for supplying, characterized by having a ground circuit for grounding a neutral point of an impedance bond at an AT location and a CPW location connecting a rail and a protection line (PW) in the middle of the AT location in order to reduce a rail potential. AC power supply circuit to reduce rail potential. 2. The rail potential reducing AC coil according to claim 1, wherein an elevated leg rebar is used in an elevated section and a tunnel reinforcing bar or a roadbed reinforcing bar is used in a tunnel section as a ground electrode of a ground circuit. Electric circuit. 3. The rail potential reducing AC feeding circuit according to claim 1, wherein a buried ground wire is used as a ground electrode of the ground circuit. 4. A series resonance circuit including a capacitor and a reactor is provided between a neutral point of an impedance bond and a ground electrode in order to prevent electrolytic corrosion in a section where a DC electric railway runs in parallel. A rail potential reducing AC feeding circuit according to claim 1, claim 2 or claim 3.