JPS619350A - Orienting method of fault point for coaxial cable feeder circuit - Google Patents

Abstract

PURPOSE:To make an accurate orientation attainable, by measuring an electric current of a coaxial cable and a voltage between both inner and outer conductors at the power source side, while metering the current of a connecting line between each rail at both ends of the cable and the cable outer conductor and thereby orienting a fault point. CONSTITUTION:In the case where a coaxial cable itself goes something wrong with a short, if both inner and outer conductors are short-circuited at a spot Sc distant away as far as lc from P1, a fault current Is flows out of a substation, while voltage Vc at the P1 point drops to some extent as compared with its normal time. And, impedance Z of up to the fault point inside the coaxial cable is proportioned to the distance lc so that impedance Zc of the coaxial cable in time of its normal state is set down as an already-known datum, so the lc is findable but the fault point is shorted by an arc, eliminating the error, whereby reactance X for a takeout portion from the impedance is calculated by a circuit M. Next, if a trolley line and a rail are short-circuited at a track, power is fed to a fault point SF from P2 as well just like from the P1 whereby a distance lF up to the fault point is calculated by a current I2 out of a current I1 and the P2 at a circuit N.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for locating a fault point in a coaxial cable feeding circuit in which a coaxial cable and an overhead contact line are connected in parallel.

In the feeding circuit of AC electric railways, when an AT feeding circuit is applied to a narrow tunnel etc., it may not be possible to maintain sufficient insulation distance between the AT feeding wires, and in that case, a coaxial cable feeding circuit is used as the feeder type. was developed. Figure 1 shows the coaxial cable feeding circuit, where CC is the inner conductor A and the outer conductor B.
Since the coaxial inner conductor A and outer conductor B are close to each other, and the mutual impedance between the two conductors is large, the round trip line impedance between the inner conductor and the outer conductor is significantly smaller than the round trip line impedance between the contact wire T and the rail R. .

For this reason, as shown in Figure 1, current 1 is supplied to the electric car directly from the substation SS through the contact wire and rail, and at the same time, it is supplied via a coaxial cable to the contact wire farther away than the electric car Car. Electricity fiIz will also be supplied from the rail.

Due to the special characteristics of such a coaxial cable feeding circuit, it is expected that there are two types of failures: a short circuit between the inner conductor and the outer conductor of the coaxial cable, and a short circuit between the contact wire and the rail.

In the above-mentioned feeding circuit, the inner conductor of the coaxial cable is connected in parallel with the contact wire, so it needs to have the same insulation strength as the contact wire, but the outer conductor is connected in parallel with the rail, so it requires insulation. The strength may be low.

By the way, in general, when a failure occurs in a power feeding circuit, it is very important to accurately detect the point of failure in terms of shortening the recovery time from the failure, and the above-mentioned coaxial cable feeding circuit is no exception.

However, since coaxial cable feeding circuits have not yet been implemented, a method for locating fault points for the feeding circuits has not yet been established. Therefore, as coaxial cable feeding circuits have recently become a reality, it has become urgent to establish a method for locating their failure points.

In view of this, the present invention provides a new and useful failure point π locating method that takes into account the special characteristics of coaxial cable feeding circuits.

Next, the orientation method of the present invention will be explained based on the drawings. Second
The figure shows the basic configuration for implementing the orientation method of the present invention.

As mentioned above, failures in the coaxial cable feeding circuit include:
There are two possible causes: a short-circuit between the inner and outer conductors of the coaxial cable, and a short-circuit between the contact wire and the rail on the overhead contact line. Therefore, it is necessary to be able to locate the fault point no matter which of these two faults occurs. Therefore, first, we will explain separately the method for locating the fault point when the coaxial cable itself has caused a short-circuit fault, and the method for locating the fault point when the short-circuit fault has occurred on the electric train line. Method of locating a fault point in the event of a fault Figure 3 shows a method of locating a fault point in the case of a fault occurring within a coaxial cable.

When the inner conductor and the outer conductor are short-circuited at a point Sc that is L away from the left end P1 of the coaxial cable, a fault current ■s flows from the substation, and the voltage ■c at 11 points decreases compared to when it is healthy.

, ν The fault current Is flowing from the substation is separated into a current IC flowing directly from point 11 to the fault point and a current ■C' flowing from the right end P2 of the coaxial cable to the fault point through the contact wire and rail.

Coaxial cables are generally laid within a number of lines, but because the inner conductor and outer conductor are close to each other, the mutual impedance between the side conductors is large, and the currents flowing through the inner conductor and outer conductor are almost equal, so it is not practical. , the mutual impedance between the coaxial cable and the contact wire and rail is negligible. That is, the impedance of the coaxial cable and the impedance of the overhead contact line made up of the contact wire trail can be considered independently. Therefore, the impedance ZC when the inner conductor and outer conductor of a coaxial cable are short-circuited is given by the unit length: ZA is the self-impedance of the inner conductor, ZB is the self-impedance of the outer conductor. Satari Zc = ZA+ ZB-2ZAB・・・・・・・・・
......It is represented by (1).

In addition, if the reciprocating impedance of the trolley line is Zllt'i, the self-impedance of the contact wire is ZT + the self-impedance of the rail is Zftl), and the mutual impedance between the trolley wire and the rail is Z・IR, then ZF per degree length is
= ZT+ ZR-2ZTR・・・・・・・・・・・・
It is expressed as (2).

Therefore, the impedance from point 11 to the failure point is: ■) Calculated from the voltage Vc and current Ic at point P0, Z=■
9/1o=Zctc...song/song (3), which is proportional to the distance tC to the failure point.

1) When calculated from the voltage Vc and current Ic' at the PI point, Z
'=VC/ic'= (ZF+ZC) 1ZC
tC...(4), the electric train line impedance is added to the coaxial cable impedance, making the equation more complicated than equation (3).

m) Voltage Vc at point pt and fault current from substation (5iI
When calculated from s, it becomes as follows, and m is proportional to the square of the distance tC to the failure point.

From the above, as a method for determining the impedance up to the failure point in the coaxial cable, using the relationship in equation (3) is the most direct directrix, and therefore the accuracy can be easily determined. Since Z obtained from this formula (3) is proportional to the distance tC from the 21st point to the failure point, assuming that the impedance Zc of the coaxial cable when healthy is known, Lc = Z/Zc
・・・・・・・・・・・・(6) Yes, the distance tc to the fault point can be found. However, since the fault point is generally short-circuited by an arc, the fault impedance Z is determined by the arc resistance. is added, increasing impedance and causing errors. In order to eliminate this error, take out the reactance X from the impedance, zC=X/Xo...
The fault point is located by comparing the force with the known reactance XC. However, θ is the voltage at 21 points■
This is the phase difference between the current IC and the current IC. In order to find the fault point distance tc using equation (7), the reactance X must be found. The reactance X shown in equation (7) is X −■0S
in・θ...Song/Song (8)-■ Represented. In FIG. 3, M is a circuit that performs the calculation of equation (8). This circuit is composed of, for example, a microcomputer.

(2) Method for locating a fault point when a short-circuit fault occurs between a contact wire and a rail on an overhead contact line Figure 4 shows a method for locating a fault point when a short-circuit fault occurs on an overhead contact line.

Since the mutual impedance between the inner and outer conductors is large in the above equation (1), the round trip line impedance ZC of the coaxial cable is ZA+ ZB: 2 ZAB ・・・・・・・・・
...A9), and Zc is extremely small, and when compared with the round trip impedance of the electric train line, Zc<<Zy ......0
0), and power is supplied to the failure point SF from the right end P2 of the coaxial cable as well as from the left end P1.

For the current supplied from point 21, I 1 and the current supplied from point 12 2 are the distance from point 21 to the fault point t.
When −p is set, it is expressed as follows. Here, since the relationship described in equation (10) exists, I2 can be approximately set as c. If the ratio of the absolute values of I1 and I2 is Hl, then since t is known, tF can be easily located.

N in FIG. 4 is a circuit that performs the calculation of equation (13). This circuit can be constructed from a microcomputer or the like.

From the above, if a failure occurs in the feeding circuit, (8)
It can be said that by calculating the equation and the α■ equation, it is possible to correctly locate the fault point.

By the way, in this case, two solutions are given, equation (8) and equation (131), so it is necessary to judge which solution locates the correct failure point.However, this judgment is not easy. Therefore, when using the ratio differential type cable failure detection device 87C, which is normally provided in the feeding circuit.
And the distance relay 44F for protecting the feeding circuit 1 in the substation is used to automatically make a judgment. That is, when a failure occurs in the coaxial cable itself, 87C operates, and the operation of 87C causes the calculation of equation (8) to be performed. On the other hand, when a failure occurs in the electric train track, 44F is activated, so the calculation of equation (13) is performed on the condition that 44F' is activated.

Of course, 44F operates even if the coaxial cable itself fails, but 87G operates when the coaxial cable fails, and 87C does not operate when the electric train line fails, so 87
From the operation/non-operation of C, it is possible to determine whether the problem is a coaxial cable failure or a failure of the overhead contact line.

Note that the insertion point of the instrument current transformer CT for detecting the fault current IC may be any lead wire of the side conductor since the same current flows through the internal conductor and the external conductor, but it is important to make the current transformer more economical. Therefore, it is desirable to insert it into the lead wire of an external conductor with low insulation strength. Furthermore, in order to reduce the insulation strength and save money, it is desirable to insert a current transformer for current measurement into the connection line between the rail and the external conductor.

As explained above, according to the present invention, when a failure occurs in a coaxial cable enclosure, the voltage between the internal and external conductors on the power supply side of the coaxial cable and the coaxial cable are reduced. Measure the flowing current and calculate the reactance up to the failure point to locate the failure point of the coaxial cable itself. At both ends of the coaxial cable, measure the current in the connecting wire between the rail and the coaxial cable outer conductor, and Because it calculates the current ratio and locates the point of failure that occurs on the overhead contact line, it is possible to accurately locate the failure point regardless of whether a failure occurs within the coaxial cable or on the overhead contact line. can.

In particular, on the condition that the operation results of the ratio differential type cable failure detection device 87G and the distance deaf relay 44F are used, it is possible to easily identify whether the failure is in the coaxial cable itself or in the electric train line. You can recover from failures more quickly,
This will greatly contribute to ensuring train operation.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a coaxial cable enclosure, Figure 2 is a basic circuit diagram for implementing the method of the present invention, and Figure 3 explains a method for locating a failure point when a failure occurs in a coaxial cable. FIG. 4 is a diagram illustrating a method for locating a fault point when a fault occurs on the electric train tracks. In the figure, W indicates the power supply voltage, and Zo indicates the internal impedance PT of the substation.

Claims (1)

[Claims] In a coaxial cable feeding circuit, when a failure occurs in the feeding circuit, measure the voltage between the internal and external conductors on the power supply side of the coaxial cable and the current flowing through the coaxial cable to calculate the reactance up to the failure point. In addition to locating the failure point of the coaxial cable itself, the current in the connection line between the rail and the coaxial cable outer conductor is measured at both ends of the coaxial cable, and the ratio of the currents at both ends is calculated to determine the failure point that has occurred on the overhead contact line. A method for locating a fault point in a coaxial cable feeding circuit, characterized by locating a point.