JP2006050696A - Underground line accident section judging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately judge an underground accident section of an underground transmission line by a single-core cable. <P>SOLUTION: An accident section judging device includes a group 1a of current transformers which are attached to each phase in the vicinity of one termination of a power cable, a first photocurrent sensor 5a which uses their residual circuit currents as measured currents, a group 1b of current transformers which are attached to each phase at the other termination, and a second photocurrent sensor 5b which uses their residual circuit currents as measured currents. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for detecting an accident section in a power transmission line. In particular, the present invention relates to an apparatus for detecting an accident in an underground line section in a transmission line in which an overhead line section and an underground line section are mixed.

Transmission lines are divided into overhead transmission lines and underground transmission lines. Overhead power transmission lines are designed to carry electric power in the air by laying electric wires on steel towers, wooden pillars, concrete pillars, and the like. On the other hand, underground transmission lines are used to carry electric power underground by laying power cables in caves. Transmission line accidents occur due to factors such as lightning, birds and beasts, wind and rain, and equipment deterioration in overhead power transmission lines, and insulation breakdown of power transmission equipment due to factors such as human error and equipment deterioration in underground power transmission lines.
When such a transmission line accident occurs, early recovery of the equipment by early detection of the accident point is required, but because the transmission line equipment is laid for a long distance, the detection of the accident point is not easy. There are many cases. In particular, in underground transmission lines, since power cables are laid underground, it is often more difficult to find an accident point.
In view of this, a transmission line accident section determination apparatus has been put into practical use, in which various sensors are attached to a power transmission facility, and in which section of the transmission line an accident has occurred.

As a device that attaches a photocurrent sensor to the end of the power cable of the underground transmission line and detects a ground fault in the underground transmission line section using the current information detected by these photoelectric current sensors, Magazine B, Vol. 112, No. 10, Development of Optical ZCT and Application to 66 kV Underground Branch Transmission Line Accident Section Discrimination ”P885 shows an underground section fault section determination apparatus as shown in FIG.
In FIG. 4, reference numeral 21 denotes a power cable for the underground power transmission line connected to the overhead power transmission line 31. Reference numerals 5a and 5b are photocurrent sensors attached so that the power cable 21 circulates in three phases in the vicinity of the connection portion with the overhead power transmission line, and by the zero-phase current flowing to the attachment point using the Faraday effect. The incident light is converted and output to the light intensity depending on the magnitude of the generated magnetic field.
A light source 3a emits an optical signal to be input to the photocurrent sensor 5a. Reference numeral 4a denotes an optical fiber that transmits an optical signal emitted from the light source 3a to the photocurrent sensor 5a. Reference numeral 6a denotes an optical fiber that transmits an optical signal output from the photocurrent sensor 5a to the photoelectric converter 7a. A photoelectric converter 7a photoelectrically converts the optical signal output of the first photocurrent sensor received through the optical fiber 6a and outputs a predetermined AC voltage signal.
Thereby, the zero phase current detected by the photocurrent sensor 5a can be output as an AC voltage signal.
A light source 3b emits an optical signal to be input to the photocurrent sensor 5b. Reference numeral 4b denotes an optical fiber that transmits an optical signal emitted from the light source 3b to the photocurrent sensor 5b. Reference numeral 6b denotes an optical fiber that transmits an optical signal output from the photocurrent sensor 5b to the photoelectric converter 7b. A photoelectric converter 7b photoelectrically converts the optical signal output of the second photocurrent sensor received through the optical fiber 6b and outputs a predetermined AC voltage signal.
Thereby, the zero phase current detected by the photocurrent sensor 5b can be output as an AC voltage signal.
8 is sandwiched between the photocurrent sensor 5a and the photocurrent sensor 5b using the AC voltage signal from the photoelectric converters 7a and 7b, that is, the magnitude and phase of the zero-phase current detected by the photocurrent sensors 5a and 5b. It is the determination part which determines the presence or absence of the ground fault in the underground line section.

In the conventional apparatus described above, it is necessary to attach photocurrent sensors to both ends of the underground line section. In the case of a triplex type CV cable used at 77 kV or less and a three-core type OF cable used at 154 kV or less, the cable diameter is about several tens of centimeters. It is possible to circulate the power cable in three phases at once with the sensor. On the other hand, in the case of a single-core type OF cable or CV cable used in a 154 kV or 275 kV system, when connecting to an overhead power transmission line with a ground branch system, the cable spacing of each phase is about 3 m in the 154 kV system and in the 275 kV system The photocurrent sensor that is about 5 m and very large according to the insulation class needs to have a very large diameter of about 6 m in the former and about 10 m in the latter. However, it is difficult to make this technically and economically. Therefore, the conventional device can be applied only to underground transmission lines in which Triplex CV cables and 3-core OF cables are laid, and is applicable to underground transmission lines in 154 kV systems and 275 kV systems in which single-core cables are laid. There was a problem that could not be done.
As a workaround to this problem, a small-diameter photocurrent sensor is attached to each phase, transmitted to the determination unit side for each phase via an optical fiber, photoelectrically converted, and then added to three phases to add a zero-phase current However, there is a problem that a photocurrent sensor, an optical fiber transmission line, and a photoelectric converter are required for each phase, resulting in a high cost.
In addition, the conventional apparatus requires a pair of photocurrent sensors installed at both ends of the underground line section for each line and corresponding optical fiber transmission lines. A current sensor and an optical fiber transmission line are required, and the cost is also a problem.

  In the underground line fault section determination device according to the first aspect of the present invention, the current flowing through the first current transformer installed near one end of the underground power transmission line and the residual circuit of the first current transformer is obtained. A first photocurrent sensor as a current to be measured, a first light source that generates an optical signal to be input to the first photocurrent sensor, and an optical signal emitted from the first light source A first optical fiber for transmitting to the photocurrent sensor, a second optical fiber for transmitting an optical signal output from the first photocurrent sensor, and the second optical fiber. A first photoelectric converter that photoelectrically converts the optical signal output of the first photocurrent sensor received and outputs a predetermined AC voltage signal, and is attached in the vicinity of the other end of the underground transmission line. The current flowing through the second current transformer and the residual circuit of the second current transformer is the current to be measured. A second photocurrent sensor; a second light source that generates an optical signal to be input to the second photocurrent sensor; and an optical signal emitted from the second light source to the second photocurrent sensor. A third optical fiber for transmitting; a fourth optical fiber for transmitting an optical signal output from the second photocurrent sensor; and the first optical fiber received via the fourth optical fiber. A second photoelectric converter that photoelectrically converts an optical signal output of the two photocurrent sensors and outputs a predetermined AC voltage signal; an output of the first photoelectric converter; and an output of the second photoelectric converter; And a determination unit for detecting a ground fault occurring in the underground transmission line portion.

  In the underground line accident section determining device according to the invention of claim 2, in the underground line accident section determining apparatus according to claim 1, by inputting the residual circuit of the first current transformer multiple times, A first photocurrent sensor for measuring current; and a second photocurrent sensor for measuring current by inputting the residual circuit of the second current transformer group in a plurality of times.

  In the underground line accident section determination device according to the third aspect of the present invention, in the underground line accident section determination apparatus according to the first or second aspect, each of the ground lines in the vicinity of one end portion of the plurality of underground transmission lines. A first photocurrent sensor that makes a current to be measured by circulating around the first current transformer group attached to the middle power transmission line and the respective remaining circuit groups of the first current transformer group at once. And the second current transformer group attached to each underground power transmission line in the vicinity of the other terminal portion of the plurality of underground power transmission lines, and the respective remaining circuit groups of the second current transformer group And a second photocurrent sensor for making a current to be measured.

As described above, according to the present invention, it is possible to detect a ground fault section with low accuracy and high accuracy with respect to an underground transmission line of a single-core cable having a wide interphase spacing.
In addition, it is possible to detect a ground fault section with a single line of photocurrent sensor and optical fiber transmission line without any practical problems even for a plurality of underground transmission lines of two or more lines, which is highly cost-effective. The device can be configured.

  Three examples will be described below in comparison with the claims.

FIG. 1 shows an example of an embodiment in which the underground accident section determining device of the invention of claim 1 is applied to one underground transmission line.
In FIG. 1, reference numeral 21 denotes a power cable for an underground transmission line connected to an overhead transmission line 31. 1a is an instrument current transformer attached near the terminal part of the underground transmission line 21, and the secondary side is star-connected to constitute a residual circuit. Reference numeral 1b denotes a current transformer for an instrument attached to the other end of the underground power transmission line 21, and the secondary side is star-connected to constitute a residual circuit. Reference numeral 5a denotes a photocurrent sensor attached around the remaining circuit of the current transformer 1a. Reference numeral 5b denotes a photocurrent sensor attached around the remaining circuit of the current transformer 1b. The photocurrent sensors 5a and 5b use the Faraday effect to convert incident light into light intensity depending on the magnitude of the magnetic field generated by the zero-phase current flowing through the attachment point, and output it.
A light source 3a emits an optical signal to be input to the photocurrent sensor 5a. Reference numeral 4a denotes an optical fiber that transmits an optical signal emitted from the light source 3a to the photocurrent sensor 5a. Reference numeral 6a denotes an optical fiber that transmits an optical signal output from the photocurrent sensor 5a to the photoelectric converter 7a. 7a is a photoelectric converter that converts the optical signal output of the photocurrent sensor received through the optical fiber 6a into a predetermined AC voltage signal.
As a result, the zero-phase current flowing in the residual circuit of the instrument current transformer 1a detected by the photocurrent sensor 5a can be output as a predetermined AC voltage signal.
A light source 3b emits an optical signal to be input to the photocurrent sensor 5b. Reference numeral 4b denotes an optical fiber that transmits an optical signal emitted from the light source 3b to the photocurrent sensor 5b. Reference numeral 6b denotes an optical fiber that transmits an optical signal output from the photocurrent sensor 5b to the photoelectric converter 7b. A photoelectric converter 7b converts the optical signal output of the photocurrent sensor 5b received through the optical fiber 6b into a predetermined AC voltage signal.
As a result, the zero-phase current flowing in the residual circuit of the instrument current transformer 1b detected by the photocurrent sensor 5b can be output as a predetermined AC voltage signal.
8 is an underground voltage sandwiched between the photocurrent sensor 5a and the photocurrent sensor 5b using the AC voltage signal from the photoelectric converters 7a and 7b, that is, the zero-phase current information detected by the photocurrent sensors 5a and 5b. It is a determination part which determines the presence or absence of the ground fault accident of a area.

  Since the photocurrent sensor detects the accident current (zero-phase current) flowing in the underground transmission line as the current flowing in the secondary side residual circuit of the instrument transformer attached to the underground transmission line, It is possible to determine a fault zone using a small-diameter photocurrent sensor even in underground transmission lines laid at large interphase intervals.

FIG. 2 is an example of an embodiment in which the underground accident section determination device of the invention of claim 2 is applied to one underground transmission line.
In FIG. 2, reference numeral 5a denotes a photocurrent sensor that amplifies the magnetic field generated by the zero-phase current and inputs the measured current of the photocurrent sensor by rotating the residual circuit of the instrument current transformer 1a a plurality of times and inputting it. is there. Similarly, 5b is a photocurrent sensor in which the residual circuit of the instrument current transformer 1b is circulated a plurality of times and input, and the magnetic field generated by the zero-phase current is amplified and used as a current to be measured by the photocurrent sensor. is there.
Moreover, since the other structure is comprised similarly to FIG. 1, the same code | symbol is attached | subjected about the same part and the overlapping description is abbreviate | omitted.

According to the first aspect of the present invention, there is provided an underground current fault section determination apparatus in which a current transformer for an instrument is attached to a single-core cable, and the residual circuit current on the secondary side is used as a measurement target of the photocurrent sensor. This makes it possible to determine the accident section even in underground transmission lines where cables are laid at wide intervals. However, since the residual circuit current on the secondary side of the instrument current transformer is reduced to the reciprocal of the current transformation ratio compared to the fault current (zero phase current) on the grid side, the photocurrent sensor has a very small current. Must be measured with high accuracy. For example, when an instrument current transformer having a current transformation ratio of 400/5 is used, the fault current of 400 A is 5 A in the residual circuit, so the photocurrent sensor needs to measure a small current of about 5 A. The invention of claim 2 solves this problem and amplifies the generated magnetic field by rotating the residual circuit current a plurality of times to obtain the current to be measured of the photocurrent sensor. This enables highly accurate current measurement.
Further, the number of circulations can be changed according to the current transformation ratio, and the current transformers for instruments having different current transformation ratios can be handled by a common photocurrent sensor.

FIG. 3 shows an example of an embodiment in which the underground accident section determination device of the invention of claim 3 is applied to two underground transmission lines.
In FIG. 3, reference numeral 21 denotes a first underground transmission line connected to the first overhead transmission line 31. Reference numeral 22 denotes a second underground transmission line connected to the second overhead transmission line 32.
1 a is a first current transformer for an instrument attached near one terminal portion of the first underground transmission line 21. Reference numeral 1b denotes a second instrument current transformer attached near the other end of the first underground transmission line 21. Reference numeral 2a denotes a third current transformer for measuring instrument attached in the vicinity of one end portion of the second underground transmission line 22. Reference numeral 2b denotes a fourth instrument current transformer attached in the vicinity of the other end portion of the second underground transmission line 22.
5a circulates the residual circuit of the first instrument current transformer 1a and the residual circuit of the third instrument current transformer 2a in a lump so that the residual circuit of the first instrument current transformer 1a It is the 1st photocurrent sensor which makes the measured current the vector addition current of the electric current which flows and the electric current which flows into the residual circuit of the 3rd current transformer 2a.
5b circulates the residual circuit of the second instrumental current transformer 1b and the residual circuit of the fourth instrumental current transformer 2b in a lump so that the residual circuit of the second instrumental current transformer 1b It is the 2nd photocurrent sensor which makes the measured current the vector addition current of the current which flows and the current which flows into the residual circuit of the 4th current transformer 2b.

  Circulating the respective residual circuits of the instrument current transformers 1a and 2a like the photocurrent sensor 5a collectively to generate a current to be measured is generated by the current flowing through the residual circuit of the instrument current transformer 1a. The Faraday effect is caused to act by a magnetic field obtained by magnetically adding the magnetic field and the magnetic field generated by the current flowing in the residual circuit of the instrument current transformer 2a. Thereby, the vector combined current of the residual circuit current of the instrument current transformer 1a and the residual circuit current of the instrument current transformer 2a, that is, the zero-phase current flowing in the first underground transmission line 21 and the second underground The vector combined current of the zero-phase current flowing through the power transmission line 22 can be detected by a single photocurrent sensor. On the other hand, considering that the zero-phase current hardly flows in a healthy state and that it is very rare that a ground fault in the underground transmission line occurs at the same time, by detecting the vector combined current, In the event of a ground fault occurring in any of the two underground transmission lines, the zero-phase current at that time can be detected by a single photocurrent sensor. That is, in order to detect an accident on underground transmission lines for two lines, the conventional apparatus requires two units, but according to the invention of claim 3, one unit is possible. Furthermore, it is also possible to detect the ground fault current of a plurality of lines with a single photocurrent sensor by adding vectors, and to detect a fault section occurring in a plurality of underground power transmission lines with a single device. Therefore, an apparatus with very high cost merit can be realized.

It is explanatory drawing which shows an example of embodiment of the underground line accident area determination apparatus of invention of Claim 1. It is explanatory drawing which shows an example of embodiment of the underground line accident area determination apparatus of invention of Claim 2. It is explanatory drawing which shows an example of embodiment of the underground line accident area determination apparatus of invention of Claim 3. It is explanatory drawing of the conventional underground line accident area determination apparatus.

Explanation of symbols

1a, 1b, 2a, 2b Current transformer 3a, 3b Light emitting part 4a, 4b, 6a, 6b Optical fiber 5a, 5b Photocurrent sensor 7a, 7b Photoelectric converter 8 Judgment part 9 Output 10 Power supply 11 Judgment device 21, 22 Underground transmission line 31, 32 Overhead transmission line

Claims (3)

A first current transformer attached in the vicinity of one end of the underground transmission line;
A first photocurrent sensor having a current to be measured as a current flowing in a residual circuit of the first current transformer;
A first light source for generating an optical signal for input to the first photocurrent sensor;
A first optical fiber for transmitting an optical signal emitted by the first light source to the first photocurrent sensor;
A second optical fiber for transmitting an optical signal output from the first photocurrent sensor;
A first photoelectric converter that photoelectrically converts an optical signal output of the first photocurrent sensor received through the second optical fiber and outputs a predetermined AC voltage signal;
A second current transformer attached near the other end of the underground transmission line;
A second photocurrent sensor having a current to be measured which is a current flowing in a residual circuit of the second current transformer;
A second light source for generating an optical signal for input to the second photocurrent sensor;
A third optical fiber for transmitting an optical signal emitted by the second light source to the second photocurrent sensor;
A fourth optical fiber for transmitting an optical signal output from the second photocurrent sensor;
A second photoelectric converter that photoelectrically converts an optical signal output of the second photocurrent sensor received through the fourth optical fiber and outputs a predetermined AC voltage signal;
A determination unit for detecting a ground fault occurring in an underground transmission line portion from the output of the first photoelectric converter and the output of the second photoelectric converter;
An underground accident section determination device characterized by comprising: In the underground line accident section determination device according to claim 1,
A first photocurrent sensor to be a current to be measured by inputting the residual circuit of the first current transformer in a plurality of times, and
A second photocurrent sensor for making a current to be measured by inputting the residual circuit of the second current transformer group in a plurality of rounds; and
An underground accident section determination device characterized by comprising: In the underground line accident section determination device according to claim 1 and claim 2,
The first current transformer group attached to each underground transmission line in the vicinity of one end portion of the plurality of underground transmission lines;
A first photocurrent sensor to be a current to be measured by collectively circulating each residual circuit group of the first current transformer group; and
The second current transformer group attached to each underground transmission line in the vicinity of the other end of the plurality of underground transmission lines;
A second photocurrent sensor to be a current to be measured by collectively circulating each residual circuit group of the second current transformer group; and
An underground accident section determination device characterized by comprising:

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