JPH0694779A - Measurement of current distribution of transmission line - Google Patents

Abstract

PURPOSE:To confirm that the data detected at the same time by respective current sensors are ones detected at the same time in the measurement of the current distribution of a transmission line. CONSTITUTION:Data transmission devices LS and current sensors B are provided to a transmission line at two or more places. The current sensors B detect currents of the suspended OPGW of a pylon and convert the detected currents to digital data to send the same to the corresponding data transmission devices. The most upstream data transmission device LSI sends synchronizing data showing data collecting timing to the downstream data transmission device. The downstream transmission device collects local sensor data in response to the synchronizing data and adds said data to the sensor data of the upstream data transmission device to further transmit the same to the downstream data transmission device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power distribution line current distribution measuring method for detecting a faulty section of a power transmission line, and more particularly to a current distribution measuring method capable of synchronizing collected data. .

[0002]

2. Description of the Related Art Conventionally, as an accident section detection system, a plurality of current detection sensors are attached to an optical fiber composite overhead ground wire (hereinafter referred to as OPGW) of an overhead power transmission line, the current flowing through the OPGW is measured, and it is analogized. A system has been put into practical use in which, after / digital conversion, it is converted into an optical signal and sent to a transmission device, and a plurality of sensor data are multiplexed by the transmission device and transmitted to a central device. An example of such a system is described in "Practical Use of Maintenance Information System for Ultra High Voltage Transmission Line Using SM Optical Fiber", Hitachi Cable, January 1990 issue.

FIG. 10 is a block diagram showing a conventional current distribution measuring system. With reference to FIG. 10, the current distribution measuring system includes current sensors B1 to Bn provided at a plurality of positions of a power transmission line, data transmission devices LS1 to LSn provided corresponding to the current sensors B1 to Bn, and a central device. A
Including and

The current sensors B1 to Bn are provided in each steel tower for suspending a power transmission line, detect the current of an overhead ground wire, convert the detected current into digital data, and connect it by an optical fiber 2. To the data transmission devices LS1 to LSn.

Each of the data transmission devices LS1 to LSn receives the digital data from the corresponding current sensor and sends it to the optical fiber in the OPGW 1 at a predetermined timing. The downstream data transmission device to which the data is transmitted is
The received data is transferred to the data transmission device further downstream. The transmission device LSn is coupled to the central device A by OPGW1.

The central unit A collects the data sequentially transferred through the OPGW 1, measures the current distribution of the power transmission line, and detects the faulty section based on the measured data.

FIG. 11 is a diagram showing a connection configuration among the OPGW 1, the current sensor B and the data transmission device LS shown in FIG.

Referring to FIG. 11, OPGW 1 has a plurality of optical fibers 2 built in a normal overhead ground wire GW. This OPGW 1 is connected to the junction box 3 after passing through the current sensor B. The connection box 3 divides the OPGW 1 into an overhead ground wire GW made of a metal wire and an optical fiber 2. The divided optical fiber 2 is connected to the data transmission device LS. The optical fiber 2 from the data transmission device LS is the OPGW on the downstream side.
1 and the optical fiber 2 of 1.

FIG. 12 is a block diagram showing the configuration of the current sensor B shown in FIG. With reference to FIG. 12, the current sensor B includes a current transformer CT that detects a current flowing through the overhead ground wire GW, an amplifier circuit 4 that amplifies the detected current, and a rectifier circuit that full-wave rectifies the amplified current. 5, and an A / D converter 6 for A / D converting the full-wave rectified current,
Compressor 7 for compressing A / D converted digital data
And an optical / electrical converter 8 for converting the output of the compressor 7 into an optical signal.
Including and

The operation of the current sensor B shown in FIG. 12 will be described. First, the current flowing through the overhead ground wire GW is detected by the current transformer CT. The detected current is the amplification circuit 4
Is amplified so that it falls within the scale range of the A / D converter 6, and full-wave rectified by the rectifier circuit 5. The full-wave rectified current is converted into digital data by the A / D converter 6 and then compressed by the compressor 7. The compressed data is converted into an optical signal by the optical / electrical converter 8 and sent to the optical fiber 2. The optical fiber 2 is an optical / electrical converter 8
The current data (digital data) converted by is supplied to the data transmission device LS. The current data given to the data transmission device LS is sent to the OPGW 1 connected to the output side of the connection box 3 (FIG. 11) via the optical fiber 2.

[0011]

In the above-mentioned conventional fault zone detection system, all current data (current waveform) are sent to the central unit, but their sampling times are not constant. Therefore, the current values received by the central device at the same time are not always the current values at the same time.

For this reason, for example, when an accident occurrence point such as a ground fault accident or a short-circuit accident in a transmission line is to be detected based on the collected current waveform distribution, the current value of each detected current waveform is usually detected. And the phase is used to make a judgment operation. However, the sampling is discrete and the same time is not maintained. For this reason, for example, although the actual current flowing through the OPGW 1 has the same phase between the current sensors B1 and B2, the central device A has a phase difference of n times the sampling interval (n is an integer). It may be recognized as such and may cause a mistake in the determination of the accident section.

The present invention has been made in order to solve such a problem of the conventional technique, and can recognize that the data detected by the respective current sensors at the same time are of the same time. An object of the present invention is to provide a method for measuring current distribution in a transmission line.

[0014]

According to the invention of claim 1 for achieving the above object, a plurality of current sensors are provided at a plurality of positions of a power transmission line, each of which detects a current flowing through the power transmission line, and a plurality of current sensors. A plurality of data transmission devices provided corresponding to each of the data transmission devices, each data transmission device including data from an upstream data transmission device and digital data obtained by sampling and A / D converting a signal from the corresponding current sensor. To a downstream data transmission device, in a current distribution measuring system such as measuring the current distribution of the power transmission line in the central station provided in the most downstream, the most upstream data transmission device of the plurality of data transmission device, A synchronization signal indicating the timing of data collection is generated and transmitted to the downstream data transmission device, and each data transmission device after the most upstream data transmission device has the most upstream data transmission device. A sampling signal is generated by correcting the synchronization signal indicating the timing of data collection based on the transmission delay time from the device to the data transmission device, and the signal from the current sensor is sampled based on the generated sampling signal. It is characterized in that it is converted into digital data and the data from the upstream data transmission device and the sampled data are transferred to the downstream data transmission device.

According to a second aspect of the present invention, the most upstream data transmission apparatus generates synchronization information including a synchronization signal indicating the timing of data collection and information indicating the order of data collection. Each subsequent data transmission device generates a sampling signal by correcting the synchronization signal indicating the timing of data collection based on the transmission delay time from the most upstream data transmission device to the data transmission device, and the generated sampling signal. The signal from the current sensor is sampled and converted into digital data based on the above, and the data from the upstream data transmission device, the sampled data, and the information indicating the data collection order are transferred to the downstream data transmission device. Is the way.

Further, in the invention of claim 3, the current sensor is coupled to a corresponding data transmission device via an optical fiber transmission line, and the corresponding data transmission device digitally outputs a current flowing through the power transmission line to the current sensor. In this method, a sampling signal for converting into data is given through the optical fiber transmission line.

Further, in the invention of claim 4, the current sensor and the corresponding data transmission device are coupled by an optical fiber,
The current sensor samples a current flowing through a power transmission line at a time interval smaller than a sampling signal interval for data collection of the data transmission device, and sends the sample to the data transmission device via the optical fiber transmission line to perform the data transmission. The device adopts, of the data sampled by the current sensor, the data input at the timing closest to the sampling signal for collecting the data, and transfers the data to the upstream data transmission device.

[0018]

According to the invention of claim 1, in all the data transmission devices, sampling can be performed at the time when the transmission delay time is corrected from the same synchronization signal, and the current value at the same time can be sampled in synchronization. Thereby, the central office can recognize the current data detected by each current sensor at the same time as that at the same time.

However, in the first aspect of the invention, even when each data transmission device can sample at the same time, there is a possibility that the data transmission timing of each data transmission device may be shifted.

According to the second aspect of the present invention, since the synchronization information includes the information indicating the collection order of the data, the data transmission device which has received this information has the information indicating the collection order in the current data from the current sensor. Is added for transmission. By doing this, in the central device, even if multiple pieces of data sampled synchronously are transmitted (received)
Even if the time is different, it can be recognized as the data of the same time.

According to the third aspect of the invention, since the data transmission device sends the synchronization signal to the current sensor, the current sensor can sample the current detected based on the synchronization signal. As a result, even when sampling is performed on the side of the current sensor and output as digital data, sampling can be performed in synchronization with another current sensor.

According to another aspect of the present invention, the current sensor samples the current flowing through the power transmission line at a finer interval than the interval of the sampling signal for data collection of the data transmission device and sends it to the data transmission device for data transmission. In the device, of the digital data received from the current sensor, the data input at the timing closest to the sampling signal for data collection is adopted, so it is not necessary to send the sampling signal to the current sensor. ,
The synchronization error can be minimized.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a current distribution detecting system for carrying out a method for measuring a current distribution of a power transmission line according to the present invention. FIG. 2 is a diagram showing a format of a transmission frame transmitted to the OPGW 1 shown in FIG.

The current distribution detection system shown in FIG.
Although the connection configuration is similar to that of the current distribution detection system shown in FIG. 0, the configuration and operation of each of the data transmission devices LS1 to LSn are different, and a transmission frame having a format as shown in FIG. 2 is sent to the OPGW 1.

Referring to FIG. 2, the transmission frame used in the system shown in FIG. 1 includes a synchronization slot 20 and data slots 21 to 2n set corresponding to data transmission devices LS1 to LSn. In the sync slot 20,
Contains synchronization data. Data slots 21-2
The data sampled by the corresponding data transmission devices LS1 to LSn is stored in n.

Referring again to FIG. 1, the most upstream data transmission device LS1 is the downstream data transmission device LS2.
A synchronization signal is generated as information indicating the timing of data collection for LSn, the synchronization signal is converted into an optical signal, and the optical signal is sent to OPGW1. For this reason, the data transmission device LS1 is referred to as an activation station. In the transmission frame F1 (FIG. 1) sent from the activation station, the synchronization data is stored at the head, and the data transmission device LS is placed in the next data slot 21.
1 own data is stored.

The data transmission device LS2 receives the synchronization data included in the transmission frame F1 transmitted from the activation station LS1 and collects data based on the sampling signal corrected for the propagation delay time. Here, the propagation delay time is
The light propagation time T1 (T1 = L / V) determined by the distance L of the optical fiber in the OPGW1 connected between the starting station LS1 and the downstream data transmission device and the speed of light V in the optical fiber, and the transmission device specific The transmission delay time T2 (assuming that the delay per station is t is T2 = t × (n−1)). Therefore, the data transmission device LS2 receives the synchronization data and performs data sampling of its own station.
Time T = T1 corresponding to these preset delay times
By correcting + T2 from the sampling time interval and performing sampling, sampling can be performed at the same time as the starting station.

If the synchronous data is data promised in the system so as to indicate that it is synchronous data, its format (data length, content, position in frame, etc.) is not specified. It may be promised to consider the data of station L1 itself to be synchronization data.

As described above, each data transmission device L
Since S1 to LSn sequentially add the data of its own station, for example, the transmission frame Fn-1 input to the data transmission device LSn is the synchronization data, Ln, as shown in FIG.
The data of S1, the data of LS2, ... The data of LSn-1 are stored in order.

FIG. 3 is a block diagram of the data transmission device shown in FIG. The plurality of data transmission devices LS2 to LSn have the same configuration, one configuration of which is shown in FIG. 3, and LS is given as a representative number.

Referring to FIG. 3, this data transmission device LS
Is an optical / electrical conversion unit 10 connected to the optical fibers of the upstream and downstream OPGWs 1, a transmission data extraction unit 11 for extracting current data from the photoelectrically converted electric signal, and a photoelectrically converted electric signal. A sync signal detection unit 12 that detects a sync signal and generates a sampling signal with a corrected transmission delay time, a sampling circuit 13, and a transmission data multiplexing unit 14 are included.

In operation, the optical / electrical conversion unit 10 converts the data input from the upstream data transmission device into an electric signal and supplies it to the transmission data extraction unit 11. The transmission data extraction unit 11 extracts the data of all upstream data transmission devices from the electric signal converted by the optical / electrical conversion unit 10. The extracted data is given to the transmission data multiplexing unit 14. The synchronization signal detector 12 detects a synchronization signal from the signal extracted by the transmission data extractor 11. The synchronization signal detector 12 corrects the propagation time T1 and the propagation delay time T2 peculiar to the transmission device to generate a sampling signal. The sampling circuit 13 samples the sensor signal from the current sensor B in response to the sampling signal generated by the synchronization signal detector 13. The sampled sensor data is transferred to the transmission data multiplexing unit 14
Given to. The transmission data multiplexing unit 14 adds the sensor data from the sampling circuit 13 to the upstream sensor data extracted by the transmission data extracting unit 11 and gives it to the photoelectric conversion unit 10. The optical / electrical converter 10 converts the electric signal from the transmission data multiplexer 14 into an optical signal and transmits the optical signal to a downstream transmission device.

The sensor signal supplied to the sampling circuit 13 includes various data such as the current flowing through the power transmission line and the ambient temperature in addition to the current data flowing through the OPGW 1.

FIG. 4 is a block diagram showing a second embodiment of the present invention. The difference between the current distribution measurement system shown in FIG. 4 and the current distribution measurement system shown in FIG. 1 is that the central device A and the most upstream data transmission device LS1 are connected by an optical fiber 2 to make one cycle of data. It is taking.

The central unit A shown in FIG. 4 generates a synchronizing signal, puts it on the transmission frame, and sends it to the optical fiber 2.

Since the subsequent operation is the same as that of the first embodiment, its explanation is omitted. In the first embodiment, when the sampling is synchronized and the obtained data is placed on the transmission frame for transmission, the data sampled synchronously by all the data transmission devices LS are placed on the same transmission frame and transmitted. If possible, they can arrive at the central device A at the same time and can be treated as the same time data. But,
It is conceivable that the data transmission frame may be different for each data transmission device.

Therefore, as a third embodiment, consider a system in which, when the starting station sends out the synchronization data, in addition to the data representing the synchronization, the data representing the order of the data, for example, a numerical value that increases in order.

FIG. 5 is a block diagram showing a third embodiment of the present invention. FIG. 6 is a diagram showing a format of a transmission frame used in the current distribution measuring system shown in FIG.

The current distribution measuring system shown in FIG. 5 and FIG.
Although the system has the same connection configuration as the current distribution measuring system shown in (1), it differs in that the format of the transmission frame sent to the OPGW 1 by each data transmission device includes a frame number.

Referring to FIG. 6, (a) shows a sync slot 20, which is composed of sync data and a frame number. (B) shows the data slots 21 to 2
Each of the data slots 21 to 2n is composed of the data of the corresponding transmission device and the data frame number used for sampling the data.

Referring again to FIG. 5, the activation station LS1 generates a numerical value corresponding to the synchronization data and frame number. The number starts from 0 and increases by 1 for each transmission of the transmission frame. The generated synchronizing signal and the numerical value are converted into an optical signal, which is sent as synchronizing data and a frame number on the same frame. The transmission frame transmitted from the activation station LS1 has the format configuration of F1 in FIG.

The data transmission device LS2 adds the data and frame number of its own station to the data from the data transmission device LS1 and gives it to the data transmission device LS3. The transmission frame transmitted from the data transmission device LS2 has the format of F2 in FIG.

As described above, since the frame numbers are assigned to the synchronous data and the data of each data transmission device, the central device A is added even if the data transmission device has a different frame. It can be recognized based on the frame number whether the data is sampled at the same time.

This is done by the data transmission devices LS2 and LS3.
An example will be described in which the data sampled at the same time and the data sampled at the same time differ. In FIG. 5, when the data added by the data transmission device LS3 is the previous frame "0", the central device A indicates the frame added to the data of the LS3 in the transmitted transmission frame. By referring to the number (numerical value 0), it can be recognized that the data of the data transmission device LS3 is the data sampled at the immediately preceding time.

In the first to third embodiments, the data transmission device LS can perform sampling in synchronization, but as shown in FIGS. 1, 4 and 5, the current sensor B3 is the current transformer CT. When the current detected in (1) is sampled (that is, A / D converted) and transmitted as digital optical data, the same time property of the data cannot be maintained.

Therefore, a method of maintaining the same time is shown in the fourth embodiment. FIG. 7 is a block diagram showing a fourth embodiment of the present invention. Referring to FIG. 7, data transmission device LS3
Is provided with an optical multiplexer / demultiplexer 9a, and the current sensor B3 is provided with an optical multiplexer / demultiplexer 9b. Optical multiplexers / demultiplexers 9a and 9b
And are coupled by the optical fiber transmission line 2. The data transmission device LS3 outputs a synchronization signal of wavelength λ1 for sampling, and the current sensor B3 outputs wavelength λ2.
The sensor data of is output. Optical multiplexer / demultiplexer 9a and 9
In b, the optical signal of the wavelength λ1 and the optical signal of the wavelength λ2 are wavelength-multiplexed and transmitted bidirectionally.

FIG. 8 is a block diagram of the current sensor B3 shown in FIG. The difference between the current sensor B3 shown in FIG. 8 and the current sensor shown in FIG. 12 is that the optical / electrical converter 8 is optically coupled to the optical multiplexer / demultiplexer 9b and is A / D converted in synchronization with the optical signal of wavelength λ1. That is, the sampling timing of the container 6 is controlled.

The operation of the system shown in FIGS. 7 and 8 will be described. First, the synchronization signal of wavelength λ1 output from the data transmission device LS3 is given to the current sensor B3 through the optical multiplexer / demultiplexer 9a, the optical fiber transmission line 3, and the optical multiplexer / demultiplexer 9b. The optical / electrical converter 8 of the current sensor B3 has a wavelength λ
The sync signal of 1 is converted into an electric signal and given to the A / D converter 6. The A / D converter 6 A / D converts the analog signal detected by the current transformer CT and further amplified and rectified in response to the synchronization signal from the optical / electrical converter 8.
The compressor 7 compresses the A / D converted data to generate sensor data. The sensor data is converted into sensor data of wavelength λ2 by the optical / electrical converter 8 and then the optical multiplexer / demultiplexer 9 is used.
given to b. The optical multiplexer / demultiplexer 9b is a data transmission device L.
The optical signal of wavelength λ1 sent from S3 and the sensor data of wavelength λ2 from the optical / electrical converter 8 are branched. Wavelength λ
The sensor data of No. 2 is given to the data transmission device LS3.

As described above, since the current sensor B3 and the data transmission device LS3 can be synchronized with each other, even if sampling is performed in the current sensor, the same time property of the data detected by the current transformer CT can be obtained. To be kept.

In the embodiments shown in FIGS. 7 and 8, the optical fiber transmission line has one core and the sensor data and the synchronizing signal are bidirectionally transmitted by wavelength multiplexing. Alternatively, the synchronization signal and the sensor data may be separately transmitted by using two cores.

FIG. 9 is a block diagram showing the fifth embodiment of the present invention. The current distribution measuring method shown in FIG.
Similar to the method of measuring the current distribution, the case where the current sensor B3 performs sampling is taken as an example. Referring to FIG. 9, current sensor B3 and data transmission device LS3 are coupled by optical fiber transmission line 3. The current sensor B3 is
The detection current is sampled at a period smaller than the sampling period for data transmission of the data transmission device LS3. Data C1 sampled in this fine cycle
C10 is given to the data transmission device LS3 through the optical fiber transmission line 3.

The data transmission device LS3 is a data transmission device LS3 among the sampled data C1 to C10.
The data closest to the synchronous sampling time for the data transmission in the above is adopted, and the adopted data is added to the data from the upstream data transmission device and transmitted to the downstream data transmission device.

A more specific description will be given. For example, when the data collection period is 1 ms interval (that is, the sampling interval and the data transmission interval in the data transmission device are 1 ms), if the sampling period in the current sensor B is also 1 ms, the sampling is performed in the sampling period of the data transmission device. Since it cannot be synchronized with, the error of 1 ms at maximum is included. However, the current sensor B performs sampling at intervals of 0.1 ms and transmits it to the data transmission device LS, and the data transmission device LS outputs the data closest to the synchronous sampling time of data collection among the sampling data at intervals of 0.1 ms. adopt. By doing so,
The sampling error can be within 0.1 ms.

Further, it is not necessary to perform bidirectional transmission using the optical multiplexer / demultiplexer as shown in FIG.

[0055]

According to the first and second aspects of the present invention, information of a plurality of current sensors attached to a power transmission line can be sampled in synchronization and an accurate current distribution at the same time can be obtained. It is possible to detect the faulty section of the power transmission line more accurately than before.

According to the third aspect of the present invention, by sending a synchronizing signal from the data transmission device to the current sensor, the current sensor can sample the detected current in synchronization with the data transmission device. Even when digital data is sent to the data transmission device, the same time property is maintained.

According to the fourth aspect of the present invention, the current sensor samples the detected current at a finer interval than the data collection timing of the data transmission device, and the data transmission device
Since the data closest to the synchronous sampling time is adopted among the data sampled at fine intervals, there is an effect that the bidirectional transmission means as in the invention of claim 3 is unnecessary.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a current distribution measuring method of a power transmission line according to the present invention.

FIG. 2 is a diagram showing a format of a transmission frame transmitted to the overhead ground wire shown in FIG.

3 is a block diagram of the data transmission device shown in FIG. 1. FIG.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram showing a third embodiment of the present invention.

6 is a diagram showing a transmission frame used in the current distribution measuring system shown in FIG.

FIG. 7 is a block diagram showing a fourth embodiment of the present invention.

8 is a block diagram of a current sensor B3 shown in FIG. 7.

FIG. 9 is a block diagram showing a fifth embodiment of the present invention.

FIG. 10 is a block diagram showing a conventional power distribution line current distribution measuring system.

11 is a diagram showing a connection configuration among the OPGW 1, the current sensor B, and the data transmission device LS shown in FIG.

12 is a block diagram of the current sensor shown in FIG.

[Explanation of symbols]

 1 OPGW 2 Optical fiber transmission line 3 Central device B1 to Bn Current sensor LS1 to LSn Data transmission device F1, F2, Fn-1 Transmission frame 20 Synchronization slot 21 to 2n Data slot

Claims (4)

[Claims] 1. A data transmission device, comprising: current sensors provided at a plurality of positions of a power transmission line, each of which detects a current flowing through the power transmission line; and a plurality of data transmission devices provided corresponding to the plurality of current sensors. The device sends the data from the upstream data transmission device and the digital data obtained by sampling and A / D converting the signal from the corresponding current sensor to the downstream data transmission device, and sends it to the central station provided at the most downstream. In a current distribution measuring system for measuring the current distribution of an electric wire, the most upstream data transmission device of the plurality of data transmission devices generates a synchronization signal indicating the timing of data collection, and the downstream data transmission device Each data transmission device after the most upstream data transmission device is based on the transmission delay time from the most upstream data transmission device to the data transmission device. A sampling signal is generated by correcting the synchronization signal indicating the timing of data collection, and a signal from the current sensor is sampled based on the generated sampling signal to be converted into digital data. And the sampled digital data are transferred to a downstream data transmission device. 2. A data transmission device comprising: current sensors provided at a plurality of positions of a power transmission line, each of which detects a current flowing through the power transmission line; and a plurality of data transmission devices provided corresponding to the plurality of current sensors. The device sends data from the upstream data transmission device and digital data obtained by sampling and A / D converting the signal from the corresponding current sensor to the downstream data transmission device, and sends it to the central station provided at the most downstream. In a current distribution measuring system for measuring a current distribution of an electric wire, the most upstream data transmission device of the plurality of data transmission devices includes a synchronization signal indicating a data collection timing and information indicating a data collection order. The synchronization information is generated and transmitted to the downstream data transmission device, and each data transmission device after the most upstream data transmission device is transferred from the most upstream data transmission device. A sampling signal is generated by correcting a synchronization signal indicating a timing of data collection based on a transmission delay time to the data transmission device, and a signal from the current sensor is sampled based on the generated sampling signal to obtain digital data. And the data from the upstream data transmission device and the information indicating the collection order contained in the sampled digital data and the synchronization information are transferred to the downstream data transmission device. Distribution measurement method. 3. A data transmission device, comprising: current sensors provided at a plurality of positions of a power transmission line, each of which detects a current flowing through the power transmission line; and a plurality of data transmission devices provided corresponding to the plurality of current sensors. The device sends the data from the upstream data transmission device and the digital data from the corresponding current sensor to the downstream data transmission device, and the current for measuring the current distribution of the transmission line at the central station provided at the most downstream side. In the distribution measurement system, each of the plurality of current sensors is coupled to a corresponding data transmission device via an optical fiber transmission line, and the corresponding data transmission device converts the current flowing through the power transmission line into digital data. A method for measuring a current distribution in a power transmission line, wherein a sampling signal is applied to a current sensor through the optical fiber transmission line. 4. A power transmission line is provided at a plurality of locations, each of which detects a current flowing through the power transmission line, the current sensor, and a plurality of data transmission devices provided corresponding to the plurality of current sensors. The transmission device sends the data from the upstream data transmission device and the digital data from the corresponding current sensor to the downstream data transmission device, and measures the current distribution of the power transmission line in the central station provided in the most downstream. In the current distribution measuring system, the current sensor and the corresponding data transmission device are coupled by an optical fiber transmission line, and each of the current sensors collects the current flowing through the detected power transmission line to collect the data of the data transmission device. The sampling signal is sampled at intervals smaller than the time interval of the sampling signal and sent to the data transmission device via the optical fiber transmission line, The device adopts the data input at the timing closest to the sampling signal for the data collection of the data sampled by the current sensor, and transmits the data to the downstream data transmission device. Current distribution measurement method.