JP3305815B2 - Power cable fault point detection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a temperature distribution in a longitudinal direction of a power cable and detecting a fault point of the power cable based on the measurement. The present invention relates to a power cable fault point detection method and device for eliminating erroneous detection.

[0002]

2. Description of the Related Art In a power cable, when an impact voltage due to a lightning strike is applied, an insulator constituting the power cable is deteriorated, or the power cable is damaged due to an external injury, the damaged portion of the power cable is damaged. A so-called ground fault (failure) may occur in which a large current flows through the grounding system due to dielectric breakdown, and the power cable is severely damaged. For example, as shown in FIG.
Although the cable 1 is laid in the tunnel 62, a large current flows through the grounding system due to a ground fault, which may cause heavy damage.

[0003] In the electric station 63, the occurrence of a failure is detected by monitoring the system current, and when a failure occurs, the relay and the like are automatically shut off. Further, the location where the failure occurs is also detected. This is called fault location. The Murray loop method or the pulse radar method is used for locating a fault point. The Murray loop method is based on the principle of the bridge, and uses the core of the failed cable as one side of the bridge to measure the resistance up to the failure point. The pulse radar method captures reflection of an electric pulse from a failure point.

[0004] In recent years, a large number of optical fibers are arranged in or on a power cable, the broken position of the optical fiber broken by the arc energy generated at the time of the ground fault is measured by the OTDR method, and the fault point is located from the broken point. There is a way to do that.

An optical fiber is laid along a power cable, and a temperature distribution in a longitudinal direction of the optical fiber is measured by using a temperature distribution measuring device. A method of locating a failure point by detecting a failure has been considered.

[0006]

In the Murray loop method or the pulse radar method, a measuring device cannot be installed until it is known that a failure has occurred. Therefore, it takes time to locate a failure point after a failure has occurred. . In addition, the location accuracy of the fault location is poor, and it is necessary to perform a cyclic inspection after the location has been performed to determine the fault location. Therefore, when these methods are used, failure recovery is delayed.

In the method of detecting the broken position of the optical fiber by the OTDR method, if the ground fault energy is small, the orientation cannot be performed because the optical fiber is not broken. Also,
When the direction in which the ground fault occurs is a direction in which the optical fiber is not disposed, the influence of the ground fault energy on the optical fiber is small. Also in this case, since the optical fiber does not break, orientation cannot be performed. It is necessary to arrange as many optical fibers as possible in a power cable in order to locate a fault without being influenced by the ground fault direction or ground fault energy, but this is practically difficult.

[0008] The method of locating a fault from the longitudinal temperature distribution is superior to the above-mentioned method. However, the temperature rise caused by a ground fault and other temperature fluctuations, such as a change in air temperature in a sinus road, It is difficult to distinguish from a temperature change or the like due to the ventilation fan operation, and if it is worse, an erroneous part may be located as a failure point.

It is an object of the present invention to solve the above-mentioned problems and to provide a power cable fault point detecting method and apparatus for eliminating erroneous detection due to factors other than a fault.

[0010]

According to the present invention, an optical fiber is laid along a power cable or a sinus or a conduit in which the power cable is laid. In the power cable failure point detection method of measuring the temperature distribution in the longitudinal direction of the optical fiber from the backscattered light distribution from the incident light from one end and detecting the failure point of the power cable from the temperature distribution, the measured temperature information is Hold, and extract a point at which the temperature difference with respect to the past average temperature is larger than a predetermined amount as a failure candidate point.
Temperature rise time due to other factors
A candidate point shorter than the intermediate point is detected as a failure point .

In order to extract the above-mentioned fault candidate points, a trip signal of a power cable is first received, a temperature distribution is measured immediately after receiving the trip signal, and a change amount of the temperature distribution before and after the trip signal is received is obtained. You may do so.

[0012] The power cable failure point detecting device is a power cable or a cave where the power cable is laid.
In a power cable fault point detection device having an optical fiber along a pipeline and a temperature distribution measuring device for measuring a temperature distribution in a longitudinal direction of the optical fiber from a backscattered light distribution of light incident from one end of the optical fiber. Extracting means for holding the measured temperature information and extracting the failure candidate points in descending order of the temperature temporal change amount, and the temperature at the extracted candidate points.
Time-sequential data arranged in chronological order and ground faults in advance
Compared to the time-lapse data that sets the temperature change that occurs,
Check whether it has the characteristics of fault occurs, and those
Pre-ground fault with longitudinal temperature distribution data including the candidate point
Therefore, the distribution data that sets the longitudinal temperature distribution that occurs
To determine if it has the characteristics of a ground fault.
Check and distribution data even when comparing with time-lapse data.
The candidate point is a failure point
Failure point detecting means for detecting the candidate point thus determined as a failure point.

[0013]

According to the above arrangement, the temperature distribution in the longitudinal direction of the optical fiber is detected. If the temperature distribution changes over time, the amount of change over time in the temperature along the optical fiber can be known. If the temperature difference with respect to the past average temperature at a certain point is larger than a predetermined amount, there is a possibility that a failure has occurred at that point, and this is extracted as a failure candidate point. At the candidate point, the temperature rise time at that point is examined. Since the rise in temperature at the time of ground fault rises faster than the rise in temperature due to other factors, if the rise in temperature at a candidate point is faster, it can be determined that this candidate point is a failure point. In addition, since the temperature rise that occurs during a ground fault occurs more locally than the temperature rise due to other factors, if the temperature rise appears in a narrow range before and after the candidate point, the candidate point is determined to be a failure point. Can be. A reliable orientation can be obtained by using each orientation result in combination. For example, candidate points are narrowed down to one point by orientation based on temperature change, and confirmation is performed by orientation based on temperature distribution.

If a trip signal generated in the power cable at the time of the ground fault is received, it is known that a ground fault has occurred somewhere in the power cable upon receiving the trip signal. If the temperature distribution is measured from this point, the temperature change before and after the ground fault can be captured, so that the candidate points can be extracted and the fault points can be located quickly and accurately.

The extraction of candidate points may be performed in descending order of the temporal change in temperature . In order to locate a failure point from a temporal change in temperature at the candidate point, a temperature change caused by a ground fault or its characteristic amount is set in advance as temporal data, and an actual measurement value is compared with temporal data. Good. In order to locate a failure point from the temperature distribution before and after the candidate point, a temperature distribution generated by a ground fault or its characteristic amount is set in advance as distribution data, and the measured value and the distribution data may be compared. A reliable orientation can be obtained by using each orientation result in combination. For example, only when the orientation based on the temperature change coincides with the orientation based on the temperature distribution, the candidate point is regarded as a failure point.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, the power cable fault point detection system is mainly laid along the power cable 1 or cable laying facilities such as a cave, a pipe, etc., for detecting a temperature distribution. An optical fiber 2 for transmitting light, a temperature distribution measuring device 3 for measuring a temperature distribution in a longitudinal direction based on detection light from the optical fiber 2, a power cable 1 when a ground fault occurs
A trigger signal generator 4 for detecting a trip signal flowing through the apparatus and generating a trigger signal for starting the location, and a fault point locating device 5 for locating a fault point based on the measured temperature distribution.

In this embodiment, the power cable has three conductors, and three-phase power is supplied from the power supply unit. The optical fiber 2 and the temperature distribution measuring device 3 may be known ones. The trigger signal generator 4 is configured as a receiving means for receiving a trip signal of the power cable 1 from a CT (current conversion coil) 6 attached to a conductor of each phase. Also, a trigger signal can be generated to reset the temperature distribution measuring device 3 and restart the measurement.

The specific operation of the present system will be described.

The operation of this system is roughly divided into two. First, the operation before the failure occurs, and the second operation after the failure occurs.

In a first operation before a failure occurs, the system can monitor the operation status of the power cable facility. In other words, by measuring the temperature of the power cable surface and various power facilities, it is possible to monitor abnormal temperatures during the operation of the transmission line, and to constantly monitor, for example, the detection of a fire in a tunnel. Specifically, the temperature distribution of the transmission line is measured by the temperature distribution measuring device 3, and the measured temperature data of each point of the line is transferred to the fault point locating device 5. The fault point locating device 5 sets an abnormal temperature for each point in advance, and generates a display / warning at a point exceeding the temperature as an abnormal point. In order to detect an abnormality as quickly as possible, it is desirable that the measurement time of the temperature distribution measuring device 3 be as short as possible. In the case of this system, the measurement time is set to several tens of seconds. Further, the fault point locating device 5 obtains an average temperature value of each point based on the transmitted temperature data, and compares the average temperature value with one measured value to detect an abnormal temperature. Do. The reason for using the average temperature value is to reduce the influence of the measurement error of the measured temperature value and accurately detect the abnormal temperature. In this system, the averaging time is set to several tens of minutes to make it much smaller than the daily fluctuation time of the power equipment temperature.

In the second operation when a failure occurs, a trip signal is detected by the trigger signal generator 4.
In this case, as the trigger signal generator 4, it is preferable to use CT6 which can be constituted by simple components. Now, the trigger signal generator 4 inputs the trigger signal to the temperature distribution measuring device 3, and the localization of the fault point is started. The temperature distribution measuring device 3 immediately resets the temperature distribution measurement data in the course of the measurement by the trigger signal and restarts the measurement. Since the ground fault occurrence time and the measurement start time of the temperature distribution measuring device 3 are simultaneous, the temperature rise at the time of the ground fault can be measured more accurately and efficiently.

Next, the operation of the fault locating device 5 will be described.

After receiving the trigger signal, the fault point locating device 5 first checks (1) whether or not the optical fiber is disconnected, and (2) extracts a candidate point of a ground fault point, and (3) From the candidate points, the ground fault point is located based on the temperature rise time and (4) the spread of the temperature rise near the candidate point. If the location cannot be determined, candidate points are re-extracted, and the ground fault point is located by the same processing as in (3) and (4).

Hereinafter, each item will be described.

(1) Detection of breakage point of optical fiber When the optical fiber 2 breaks, the temperature distribution measuring device 3 causes the temperature to fluctuate greatly at points after the breakage point as shown in FIG. A measurement result as shown in FIG. In order to detect this variation, a temperature difference is set in advance (Ta: several tens to several hundred degrees as an example). That is, the temperature difference between each point on the optical fiber 2 before and after the trip signal is generated (the difference between the past average temperature and the present temperature) is determined. When the absolute value of this temperature difference is equal to or greater than the set value Ta, Optical fiber 2
Is determined to be disconnected, and the near end on the temperature distribution measuring device 3 side is located as a ground fault point.

(2) Extraction of Candidate Points When the optical fiber 2 is not disconnected, candidate points as ground fault points are extracted as shown in FIG. For this, a temperature rise value generated at the time of a ground fault is set in advance (Tb: several tens degrees as an example). A point at which the average temperature distribution obtained before the occurrence of the trip signal and the temperature difference after the generation exceeds the set temperature value Tb obtained in (1) above is picked up as a candidate point.
Here, the set temperature value Tb is initially set to several tens of degrees in order to distinguish from a temperature rise due to various factors other than the ground fault. If there is no point exceeding this setting, the set value is gradually lowered, and this is repeated until a candidate point is extracted.
If no candidate point is finally found, a standard is set indicating no candidate point.

(3) Evaluation of Temporal Characteristics of Temperature at Candidate Point With respect to the candidate point, a time-dependent change in temperature rise is determined, and its rise time is determined. As shown in FIG. 3 (c), the rise time of the temperature rise due to the ground fault is caused by the temperature rise due to other factors (temperature change in the tunnel, temperature fluctuation due to ventilation fan operation, etc.).
Therefore, candidate points are narrowed using this as a criterion.

(4) Evaluation of the spread of the temperature rise in the longitudinal direction including the candidate points (referred to as distance characteristics) For the narrowed candidate points, the temperature in the longitudinal direction including the candidate points
Extent of the temperature rise from the degree distribution (the point at which the temperature rise is happening
Is evaluated ) and confirmed as a ground fault point. As shown in FIG. 3D, the fact that the spread of the temperature rise at the ground fault point is smaller than that due to other factors is used.

Next, another embodiment of the present invention will be described.

As shown in FIG. 2, the fault point detecting device 20
Is an optical fiber 2 and a temperature distribution measuring device 3 similar to FIG.
A temperature holding circuit 21 for holding temperature distribution information measured by the temperature distribution measuring device 3, obtaining a difference of the held temperature distribution information at a predetermined time, and calculating a temperature difference at a point where the difference appears. Temperature difference detection circuit 22 for detecting position and position information, a rearrangement circuit 23 for rearranging position information in descending order of temperature difference, a ground fault condition check circuit 24 for checking a ground fault condition, and an orientation result display device for displaying an orientation result 2
5 is comprised.

The temperature holding circuit 21, the temperature difference detecting circuit 22, and the rearranging circuit 23 are the extracting means 7 for extracting candidate failure points in descending order of the amount of change in temperature. The ground fault condition check circuit 24 compares the temporal change of the temperature at the extracted candidate point with the preset aging data, and compares the temperature distribution before and after the candidate point with the preset distribution data. The failure point detection means 8 detects whether or not the candidate point is a failure point.

In FIG. 2, temperature distribution data at points where the optical fiber 2 is divided in units of 1 m are input every minute.
The temperature holding circuit 21 holds these data in order to detect a temperature change at each point. The temperature difference detection circuit 22 calculates the amount of change in temperature at each point every minute. Since a point with a large temperature difference is likely to be a failure point, the rearranging circuit 2
In step 3, the position information is rearranged in descending order of the temperature difference. As described above, since the number of candidate points is not limited to one, it is necessary to determine the order in which the orientations are performed.

In the ground fault condition check circuit 24, the temperature in the longitudinal direction including the candidate point in the order
Temperature distribution data generated in advance in the longitudinal direction
The distribution is compared with the set distribution data . That is, the longitudinal direction
It is checked whether the characteristic of the ground fault that the spread of the temperature rise is narrow in the temperature distribution of the direction is small . If there is a ground fault characteristic, the temperature data at the candidate point
Time-sequential data arranged in chronological order is generated in advance by ground fault
The temperature change is compared with the set aging data . That is, the data of the candidate points are arranged in time order from the temperature distribution information held by the temperature holding circuit 21. And the candidate point
It is checked whether or not there is a feature at the time of ground fault that the temperature rise is fast . When both the characteristics of the temperature distribution and the characteristics of the temporal change have the characteristics at the time of ground fault,
The orientation result display device 25 displays the orientation result of the fault point.

In the above embodiment, the fault point is always located. However, the fault point may be located after the occurrence of the ground fault is detected by the trip signal. Further, instead of rearranging the points over the entire length of the cable in the rearranging circuit 23, the required number may be rearranged in descending order of the temperature difference.

Next, another embodiment will be described.

In the energy generated at the time of ground fault, not only the heat, that is, the temperature rise due to the arc energy of the ground fault, but also any tension (for example, expansion of the cable connection portion) is applied to the optical fiber laid in the power cable. is there. It is conceivable that microbending occurs in the optical fiber due to the tension, and consequently the transmission loss of the optical fiber changes at the place where the ground fault occurs.

As a result, a change occurs in the transmission loss after the micro-bend occurs. Looking at the transmission loss measurement results shown in FIG. 4, both of the two types of scattered light A and S for obtaining the temperature change. When this is converted into a temperature, the temperature at a point after the ground fault point changes as compared to that at the ground fault point as shown in FIG. In some cases, the temperature decreases as shown in FIG. 5, and in other cases, the temperature increases. Therefore, in the orientation procedure, there are a method based on the absolute value of the temperature value when checking the optical fiber for disconnection, and a method for checking the transmission loss of the optical fiber every time. This method is effective for detecting a ground fault condition where the temperature rise value is small.

[0039]

The present invention exhibits the following excellent effects.

(1) Temperature fluctuations other than the ground fault are distinguished from the temperature fluctuations of the ground fault, and only the ground fault point is accurately located.

(2) Since the fault point can be accurately and instantaneously located, the fault can be quickly recovered.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power cable fault point detection system according to an embodiment of the present invention.

FIG. 2 is a block diagram of a fault point detection device showing another embodiment of the present invention.

FIG. 3 is a graph for explaining the operation of the fault locating device.

FIG. 4 is a graph showing a change in transmission loss due to the occurrence of microbending.

FIG. 5 is a graph showing a temperature distribution measurement result when microbending occurs.

FIG. 6 is an explanatory diagram of a power cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power cable 2 Optical fiber 3 Temperature distribution measuring device 4 Trigger signal generator 5 Fault point locating device 7 Extraction means 8 Fault point detecting means

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shunichi Iida 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Co., Inc. (72) Inventor Mannobu Yokoyama 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Within Electric Power Company (72) Inventor Yasuhiro Miyata 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Within Nippon Electric Cable Co., Ltd. Optro System Research Laboratories (72) Inventor Yoshio Ichi, 5 Hidaka-cho, Hitachi City, Ibaraki Prefecture No.1-1, Nippon Electric Cable Co., Ltd. Optosystem Research Laboratory (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 31/08 H02H 7/26

Claims (3)

(57) [Claims] An optical fiber is laid along a power cable or a sinus or a conduit in which the power cable is laid, light is incident from one end of the optical fiber, and an optical fiber is obtained from the backscattered light distribution. In the power cable fault point detection method of measuring the temperature distribution in the longitudinal direction of the power cable and detecting the fault point of the power cable from the temperature distribution, the measured temperature information is held, and the temperature difference with respect to the past average temperature is larger than a predetermined amount. A point is extracted as a failure candidate point, and the
Temperature rise time due to other factors
A method for detecting a fault point of a power cable, wherein a candidate point shorter than the intermediate point is detected as a fault point. 2. In order to extract the fault candidate point, first, a trip signal of a power cable is received, a temperature distribution is measured immediately after receiving the trip signal, and a change amount of the temperature distribution before and after the trip signal is received. 2. The power cable fault point detection method according to claim 1, wherein 3. An optical fiber along a power cable or a sinus or conduit in which the power cable is laid.
In a power cable failure point detection device having a temperature distribution measurement device that measures the temperature distribution in the longitudinal direction of the optical fiber from the backscattered light distribution of light incident from one end of the optical fiber, the measured temperature information is held. Extraction means for extracting candidate failure points in descending order of time variation of the temperature, and time-lapse data in which temperature data at the extracted candidate points are arranged in time order.
Data and the temperature change caused by a ground fault in advance.
Whether it has the characteristics at the time of ground fault compared with the time data
Is checked, and the temperature in the longitudinal direction including the candidate point is checked.
Cloth data and the longitudinal temperature component generated in advance by ground fault
Compared with the distribution data set with cloth, it has the feature at the time of ground fault
To check if they are
The candidate point in both the comparison and the distribution data
Detect candidate points identified as failure points as failure points
Power cable fault point detecting apparatus characterized by comprising a failure point detecting means that.