JP2945300B2 - How to measure the impedance of the cable end - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EBG (end box gas terminal, hereinafter referred to as E) connected to a terminal of a power cable.
BG).

[0002]

2. Description of the Related Art When a cable is connected to a GIS (gas insulated line, hereinafter referred to as GIS), an EBG filled with an insulating gas is provided at the end of the cable. May be required. Conventionally, there is no effective method for obtaining the impedance of the EBG, and the impedance is usually calculated from design specifications and the like.

[0003]

SUMMARY OF THE INVENTION
Since the impedance of BG was obtained from the calculation,
Unlike the state where the cable is actually connected to the EBG, there is a problem that the error is large. The present invention has been made in order to solve the above-described problems of the related art,
An object of the present invention is to obtain an EBG impedance in a state where an EBG is connected to a power cable more accurately.

[0004]

According to the present invention, there is provided a method for measuring the impedance of a cable terminal provided with an EBG, comprising the steps of: attaching a first electrode to a cable surface with an insulating tube interposed therebetween; A first voltage generated between the first electrodes when a simulation pulse is directly injected into a conductor of a line is detected, and a simulation pulse is indirectly transmitted from a second electrode attached to a cable surface with an insulating tube interposed therebetween. And a second voltage generated between the first electrodes when injecting is injected, and an impedance of a cable terminal portion is obtained based on the first voltage and the second voltage.

[0005]

[Function] When the line is under construction and the EBG is not attached to the end of the cable, or after the completion of the line construction and power is not being applied to the line, the cable conductor is directly used or an earth switch is used. Thus, a simulation pulse can be injected into the cable conductor.

Accordingly, in the present invention, a simulated pulse generator is connected between a cable conductor and an insulating cylinder provided near a cable end portion during construction or when power is not being applied after completion of construction. Inject a simulated pulse. And
A first voltage generated between first electrodes attached to the cable with the insulating tube interposed therebetween is detected. The first voltage is expressed by the following equation (3) consisting of the surge impedance of the cable, the impedance between the cable sheath and the ground, the impedance of the EBG, the impedance between the EBG and the ground, and the current injected from the simulated pulse generator. 1) or
It can be expressed by (4).

Next, a simulated pulse having the same magnitude as the simulated pulse is injected from the simulated pulse generator through a second electrode attached to the cable with the insulating tube interposed therebetween, and the cable is inserted with the insulating tube interposed therebetween. A second voltage generated between the first electrodes attached to the first and second electrodes is detected. Similarly, the second voltage includes the surge impedance of the cable, the impedance between the sheath and the ground of the cable, the impedance of the EBG, the impedance between the EBG and the ground, and the current injected from the simulated pulse generator. It can be expressed by the following equation (2).

Therefore, using the above equations (1) and (2) or (4) and equation (2), the impedance between the sheath of the cable and the ground, the impedance between the EBG and the ground, and the injection from the simulated pulse generator are used. By erasing the generated current, the surge impedance of the cable, the first voltage and the second voltage, and E
The relationship with the impedance of the BG can be obtained. Here, since the surge impedance of the cable is known,
From the first voltage and the second voltage, the following equations (3) and (5)
The EBG impedance can be obtained from the equation.

According to the present invention, since the impedance of the EBG is obtained as described above, the impedance of the EBG when the EBG is connected to the end of the power cable can be obtained more accurately.

[0010]

Embodiments of the present invention will be described below. (1) Example 1 FIGS. 1 and 2 are diagrams showing an example of measuring the impedance of an EBG by injecting a simulation pulse between an upper metal fitting of an insulating cylinder and a conductor in the present invention.

FIG. 1 (a) shows a structure in which a simulated pulse is directly injected into a cable conductor, 1 is a cable conductor, 2
, A cable shield; 3, an insulating cylinder provided near the cable end; and 4, an EBG. Reference numeral 11 denotes a simulation pulse generator. The output of the simulation pulse generator 11 is connected to the cable conductor and the upper metal fitting of the insulating cylinder 3. Reference numeral 12 denotes a signal detector, and 12a denotes a pair of electrodes attached to the cable surface. The electrode 12a is connected to the signal detector 12.

FIG. 1B is an equivalent circuit of FIG. 1A, and symbols used in FIG. 1A correspond to the following values in FIG. Zc: Surge impedance of cable Zs: Impedance between cable sheath and ground Zg: Impedance of EBG3 Zs': Impedance between sheath of EBG3 and ground I: Current injected from simulated pulse generator 11 Va: Signal detector 12 FIG. 2A shows a configuration in which a simulation pulse is indirectly injected through an electrode, 11 is a simulation pulse generator,
The simulated pulse generator 11 is connected to a pair of electrodes 11a attached to the cable surface.

FIG. 2B is an equivalent circuit of FIG. 2A. In FIG. 2B, a voltage Vb is a detection signal voltage detected by the signal detector 12, and other symbols are those of FIG.
This is the same as that shown in FIG. FIG.
1A and 1B, the current I injected from the simulated pulse generator 11 corresponds to the simulated pulse generator 1 shown in FIGS.
It is the same value as the current injected from 1.

Next, the measurement of the impedance of the EBG in this embodiment will be described. When the line is under construction and the EBG is not attached to the end of the cable, or after the completion of the line construction and power is not being applied to the line, the simulated pulse generator 1 is attached to the cable conductor and the upper fitting of the insulating tube 3.
1 is connected, and a simulated pulse I is injected into the cable conductor.

The connection between the cable conductor and the output of the simulation pulse generator 11 can be made by the following method. When the EBG is not attached during the construction of the track, as shown in FIG. 4A, the output of the simulated pulse generator 11 is directly connected to the cable conductor at the end of the cable. If power is not applied after the construction of the track, and there is an available earth switch near the EBG, this is used.

That is, as shown in FIG.
When the earth switch 13 is provided near G and the earth switch can be opened,
The earth switch is opened, and the output of the simulated pulse generator 11 is connected to the conductor-side contact of the earth switch. If there is an exposed portion of the cable conductor near the EBG, the output of the simulation pulse generator is directly connected to the exposed portion.

When the simulation pulse is injected from the simulation pulse generator 11 as described above, the detection voltage Va detected by the signal detector 12 is calculated from the equivalent circuit of FIG.
Equation (1) is obtained. Va = {(Zs + Zs ') ZgI} / (Zc + Zg + Zs + Zs') (1) Next, as shown in FIG. 2, a model is formed on a pair of electrodes 11a attached to the surface of the cable with the insulating tube 3 interposed therebetween. The pulse generator 11 is connected, and the simulation pulse I is injected.

At this time, the detection voltage Vb detected by the signal detector 12 is calculated by the following equation (2) from the equivalent circuit of FIG.
It looks like an expression. Vb = {(Zs + Zs ') (Zc + Zg) I} / (Zc + Zg + Zs + Zs') (2) From the above equations (1) and (2), the impedance of the EBG is obtained as the following equation (3). Zg = Va Zc / (Vb-Va) (3) Since the surge impedance Zc of the cable is known in the above equation (3), the EBG of the EBG is determined by the voltage Va obtained from FIG. 1 and the voltage Vb obtained from FIG. The impedance Zg can be determined. (2) Embodiment 2 FIG. 3 is a diagram showing an embodiment of measuring the impedance of the EBG by injecting a simulation pulse between the lower metal fitting of the insulating cylinder and the conductor in the present invention.

FIG. 3 (a) shows the configuration of FIG. 1 except that the output of the simulation pulse generator 11 is connected to the lower metal fitting of the insulating tube 3.
The same components as those shown in FIG. 1 are denoted by the same reference numerals. FIG. 3B is an equivalent circuit of FIG. 3A. Va ′ used in FIG. 3A is a detection signal voltage detected by the signal detector 12, and other symbols are those in FIG. 1B. Is the same as that shown in FIG.

Next, the measurement of the impedance of the EBG in this embodiment will be described. As in the first embodiment, when the line is under construction and the EBG is not attached to the end of the cable, or after the construction of the line is completed and power is not applied to the line, the cable conductor is connected using an earth switch or the like. Then, the output of the simulation pulse generator 11 is connected to the lower metal fitting of the insulating cylinder 3 and the simulation pulse I is injected into the cable conductor.

When a simulated pulse is injected from the simulated pulse generator 11 as described above, the detection voltage Va ′ detected by the signal detector 12 is calculated from the equivalent circuit shown in FIG.
Equation (4) is obtained. Va '= {(Zs + Zs') ZcI} / (Zc + Zg + Zs + Zs') (4) Next, as shown in FIG. 2, a pair of electrodes attached to the surface of the cable with the insulating tube 3 interposed therebetween. The simulation pulse generator 11 is connected to 11a, and the simulation pulse I is injected.

At this time, the detection voltage Vb detected by the signal detector 12 is given by the above equation (2). From the above equations (4) and (2), the impedance of the EBG is obtained as in the following equation (5). Zg = (Vb-Va ') Zc / Va' (5) In the above equation (5), since the surge impedance Zc of the cable is known, the voltage Va 'obtained from FIG. 3 and the voltage Vb obtained from FIG. , EBG can be determined.

[0023]

As described above, according to the present invention, when a simulated pulse is directly injected into a conductor of a cable line, the first voltage generated between the first electrodes sandwiching the insulating cylinder is detected. And detecting a second voltage generated between the first electrodes when a simulation pulse is indirectly injected from a second electrode attached to the cable surface with the insulating tube interposed therebetween, and detecting the first voltage. And the second voltage, the impedance of the EBG is obtained, so that the impedance of the EBG when the EBG is connected to the end portion of the power cable is compared with the case where the impedance of the EBG is calculated from the design specifications and the like.
It is possible to obtain more accurately.

[Brief description of the drawings]

FIG. 1 is a diagram showing a case where a simulation pulse is directly injected between a conductor and an upper part of an insulating cylinder.

FIG. 2 is a diagram showing a case where a simulation pulse is indirectly injected into electrodes sandwiching an insulating cylinder.

FIG. 3 is a diagram showing a case where a simulation pulse is directly injected between a conductor and a lower metal fitting of an insulating cylinder.

FIG. 4 is a diagram illustrating a method of injecting a simulation pulse into a cable conductor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable conductor 2 Cable shielding 3 Insulating cylinder 4 EBG 11 Simulated pulse generator 11a Electrode 12 Signal detector 12a Electrode 13 Earth switch

Claims (1)

(57) [Claims] In the method for measuring the impedance of a cable end provided with an end box gas terminal, a first electrode is attached to a cable with an insulating tube interposed therebetween, and a simulated pulse is directly injected into a conductor of the cable line. A first voltage generated between the first electrodes is detected, and a voltage generated between the first electrodes when a simulation pulse is indirectly injected from a second electrode attached to a cable with an insulating tube interposed therebetween. A method for measuring the impedance of a cable terminal, comprising: detecting a second voltage; and obtaining an impedance of an end box gas terminal based on the first voltage and the second voltage.