JP2569811B2 - Method of locating accident points on underground transmission lines - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for locating a ground fault point on an underground transmission line.

[Related Art] An increase in demand for electric energy necessitates a stable supply of electric power, and technologies relating to reliability of underground power transmission lines such as cables are being developed. Similarly, in the case of a catastrophic accident, it is necessary to quickly locate the fault and take appropriate recovery work. In addition, as an accident in an underground transmission line, a ground fault accident in which a conductor and a sheath are short-circuited due to insulation breakdown is typical.

FIG. 3 shows a conventional cable accident section locating method. 3
Current transformers to cross-bond wires 9,10,11 connecting metal sheaths 13,4 separated by insulation joints IJ of phase underground cables 1,2,3 and metal sheaths 5,6,7,8 of phase By installing 12, the current flowing through the sheath during a ground fault was detected. Then, the fault point localization was performed by comparing the magnitude phase of the sheath current for each adjacent section.

In addition to the detection method using the CT, a detection method using an optical magnetic field sensor has been put to practical use. This method is a method in which a magnetic field due to a large current at the time of a ground fault is attached to a cable connection portion.

[Problems to be Solved by the Invention] However, since the CT and the optical magnetic field sensor are installed at each joint, the accident point can be located only on a joint basis, and the installation work is difficult because the CT is large and heavy. In addition, there is a problem that when the electrical signal from the CT is converted into an optical signal, an increase in the size of the system is inevitable.

An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art,
It is an object of the present invention to provide a method capable of densely locating a ground fault accident section.

[Means for Solving the Problems] To achieve the above object, the invention according to claim 1 is
An accident point locating method, in which a sensor is installed in a trough with a pressure-release presser lid that stores power cables, and the sensor detects the opening operation of the pressure-release presser lid that occurs in the event of a ground fault, etc.
As a sensor, a pair of optical fibers are installed on both sides of the pressure release cover, facing each other, and when a ground fault occurs, the pressure release cover passes between the pair of optical fibers and shields light to locate the accident point. This is a method of locating an accident point on an underground transmission line.

According to a second aspect of the present invention, there is provided an accident point locating method in which a sensor is installed in a trough having a pressure relief cover for accommodating a power cable, and the sensor detects an opening operation of the pressure relief cover which occurs at the time of a ground fault. As a sensor, one optical fiber is fixed to the right and left sides of the pressure release cover, and when a ground fault occurs, the optical fiber is disconnected by opening the pressure release cover, and the flow of light in the optical fiber This is a method for locating an accident point on an underground transmission line by locating the accident point.

[Operation] An underground cable that supplies large power in an urban area has a high voltage, and when a cable accident occurs, a large current flows between the high-voltage conductor and the metal sheath with an arc phenomenon. Since this energy is instantaneously generated, a pressure wave accompanied by a shock wave is generated around the cable accident. This pressure wave is released by releasing the presser lids provided at various places for the cable storage troughs to prevent damage to the trough itself.After the disappearance of the accident current, the presser lids return to their original state, and the trough is deprived of oxygen. To prevent cable burning.

Such an important cable for transmitting large power is often stored in a trough with a presser cover, and a cable accident involves opening the trough presser lid. Can be detected. In other words, the pressure wave associated with the cable accident propagates at the speed of sound, the pressure wave reaches the presser lid near the accident point quickly and opens the presser lid, and the adjacent presser lid opens with a delay of the propagation time, Since the pressure wave becomes smaller as the distance increases, the presser lid does not open. Therefore, it can be seen that there is an accident point near the position where the operation of the presser lid occurred earliest.

[Embodiment] Hereinafter, the present invention will be described with reference to FIG.

Pressure releasing holes 18 are attached to the upper surface of the FRP trough 13 at 1.5 m intervals, and a rubber pressing lid 14 having a size larger than the pressure releasing holes 18 is fixed thereon by a pressing plate 15. A pair of optical fibers 17, 17 are installed facing each other on the upper surface of an optical fiber fixing base 19 installed on the left and right side surfaces of the holding cover 14. Normally, light is in a conductive (ON) state. Such facilities are installed at arbitrary intervals in the longitudinal direction of the trough 13.

Now, when a ground fault or the like occurs, the pressure in the trough 13 rises rapidly, and the pressure pushes up the presser lid 14 through the pressure release hole 18 (20). At this time, a pair of opposing optical fibers 17, 17
The presser cover 14 passes through the space, and is shielded (light OFF). After a certain period of time, the pressure in the trough 13 decreases, and the light returns to the conductive state (light ON) again. This situation is shown in FIG.
In the figure, A, B and C indicate arbitrary points in the longitudinal direction of the sinus (in the order of A, B and C). Now, when the ground fault occurs at point B near the light T = T ₁ is OF
Becomes F. After a while, T = T ₂ (T ₂ > T ₁ )
, The light is turned off, and a distribution diagram as shown in the figure is obtained. If the number of detection points is increased, the tendency becomes more remarkable, and the ground fault point can be located. That is, by detecting the occurrence of an accident in the vicinity of the operation of any of the presser lids 14, or detecting the time difference between the operations of the plurality of presser lids 14, and in the vicinity of the presser lid 14 that operated fastest. It is located when there is an accident point.

Also, instead of opposing a pair of optical fibers 17, 17,
One optical fiber may be fixed to the left and right side surfaces of the holding cover 14, the optical fiber may be disconnected by the opening operation 20 of the holding cover 14, and the flow of light in the optical fiber may be detected. In this case, if one optical fiber is applied to each presser lid, the accident point can be known from the occurrence of the light interruption or the time difference of the light interruption occurrence. In addition, if one common optical fiber is applied to a plurality of (including the entire number of) cover lids, the occurrence of an accident can be known only by the occurrence of light interruption. Note that the position of the break in the optical fiber can be easily measured by measuring the distance from the incident end to the end due to the break using a normal optical pulse time domain reflectometer (OTDR) technique.

[Effects of the Invention] As described above, the present invention has the following effects.

(1) The ground fault section can be accurately and densely (1.5m minimum).

(2) The ground fault locating section can be arbitrarily determined for each pressure release lid.

(3) Since the ground fault accident section can be densely located, restoration work can be performed in a short time.

(4) Since the equipment used in the present invention has a simple structure, it is lightweight and inexpensive.

(5) Since signal detection is performed by an optical signal, there is no possibility of malfunction due to no electromagnetic induction.

[Brief description of the drawings]

FIG. 1 shows an apparatus used in the present invention, in which (a) is a plan view, (b) is a transverse sectional view, (c) is a longitudinal sectional view, and FIG. 2 is an explanatory view showing the operation of the present invention. FIG. 3 is an explanatory view showing a conventional example. 1: 3 phase underground cable 1 phase, 2: 3 phase underground cable 2 phase, 3: 3 phase underground cable 3 phase, 4 to 8: metal sheath, 9 to 11: cross bond wire, 12: current transformer , 13: FRP trough, 14: presser cover, 15: presser plate, 16: opposing optical fiber (sensor), 17: optical cable, 18: release hole, 19: fixed base, 20: presser cover in case of ground fault Open operation.

Claims (2)

(57) [Claims] 1. An accident point locating method in which a sensor is installed in a trough with a pressure-release presser lid that houses a power cable, and the opening operation of the pressure-release presser lid that occurs at the time of a ground fault is detected by the sensor. As described above, a pair of optical fibers are installed on both sides of the pressure-release press cover so as to face each other, and when a ground fault occurs, the pressure-release press cover passes between the pair of optical fibers and blocks light, thereby causing an accident. A method for locating an accident on an underground transmission line. 2. An accident point locating method in which a sensor is installed in a trough with a pressure-release presser lid for accommodating a power cable, and an opening operation of the pressure-release presser lid that occurs at the time of a ground fault is detected by the sensor. As described above, one optical fiber is fixed to the left and right side surfaces of the pressure-release press cover, and when a ground fault occurs, the pressure-release press cover is opened to disconnect the optical fiber, and the light in the optical fiber A method for locating an accident point on an underground transmission line by locating the accident point by interrupting the flow.