1. Field of the Invention
The present invention relates to a current-differential relay device capable of detecting a fault in a protected zone.
2. Description of the Related Art
One approach to detecting a fault of a power transmission line within a protected zone is to install a pair of current-differential relay devices respectively in both ends of the power transmission line. In such a system, one current-differential relay device transmits sampling current data obtained by sampling current flowing at one end of the power transmission line to the other current-differential relay device via a predetermined signal transmission line, and receives sampling current data at the other end of the power transmission line from the other current-differential relay device. The one current-differential relay device then calculates a difference in electric current between the sampling current data of current detected by the one current-differential relay device and the sampling current data transmitted from the other current-differential relay device to detect the fault in the protected zone.
As to the data transmission between the current-differential relay devices, each current-differential relay devices performs sampling of phase current data in a cycle of 30 degrees, and one current-differential relay device transmits and receives the sampling current data to and from the other current-differential relay device via a 54-kbps (or 64-kbps) signal transmission line. Then, a difference in electric current between the sampling current data by the one current-differential relay device and the sampling current data by the other current-differential relay device is calculated and it is determined that a fault occurs if the difference is more than a predetermined value. In addition, an unused bit of transmission information is assigned for on/off information (positive or negative data) of the current-differential relay device, thereby enabling the receiving end to determine the failure of transmission or to use it for estimation of device operation information for a protection device for example (see Japanese Patent Application Laid-open No. 2005-176440). This technique is suitable for determining a failure of transmission and for identifying the operation state of the device, as described in JP-A No. 2005-176440.
Although the conventional technique for transmission, as described in JP-A No. 2005-176440 can be applied to determining a failure of transmission and identifying the operation state of the device, it is not suitable for analyzing failure based on information that one current-differential relay device in operation receives from the other current-differential relay device, and for obtaining data for relay device maintenance. Moreover, the analysis based on data obtained by one current-differential relay device in operation from the other current-differential relay device, requires either an operator to go off to the place the other current-differential relay device is installed and to directly obtain the data from the other current-differential relay device, or a remote monitoring control system to be installed in each substation with a connection interface to the current-differential relay devices.
Accordingly, in order to obtain the setting value, states of relay elements, and device input/output signals of the other current-differential relay device for the purpose of analysis in relay operation, every when a fault occurs, the conventional current-differential relay device requires either the operator to go off to the place where the other current-differential relay device is several tens of kilometers far away from the one current-differential relay device, or a specific monitoring control system to be installed in advance. This leads to problems that take long time to properly operate with data analysis and need equipment investment.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to an aspect of the present invention, a current-differential relay device, installed at one end of a power transmission line within a protected zone, includes a transmission data processor for performing a transmitting process that transmits first sampling current data obtained by sampling current flowing the power transmission line at the one end to another current-differential relay device installed at the other end of the power transmission line within the protected zone, through a predetermined signal transmission line, and a receiving process that receives second sampling current data obtained by sampling current flowing the power transmission line at the other end from the another current-differential relay device through the signal transmission line; a differential calculator for calculating a difference in electric current between the first sampling current data and the second sampling current data, the difference being used for detection of an occurrence of fault in the protected zone; and a human-machine interface capable of receiving and presenting information through a display unit. The signal transmission line has a transmission rate of 2048 kbps or higher. The transmission data processor transmits the first sampling current data in a transmission frame used in the signal transmission line, and transmits, using an unused field not for the sampling current data in the transmission frame, display-related data that is output from the human-machine interface.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of a current-differential relay device according to the present invention will be explained below in detail with reference to the accompanying drawings. Note that the invention is not limited to the embodiments.
The first current-differential relay device 101a includes a filter 3, a sample-hold circuit 4, an A/D converter 5, a differential calculator 8, a human-machine interface (HMI) 9, a common component 10, the contact 11, transmission data processors 12a and 12b, a sampling synchronization control processor 13, and optical interface (I/F) 14.
Operation of the current-differential relay devices will be described below. Sampling current data that is input to the first current-differential relay device 101a through the power transmission line L and the current transformer 2a is converted into data to be contained in a predetermined transmission frame through the filter 3, the sample-hold circuit 4, the A/D converter 5, and the transmission data processor 12a, and then transmitted to the second current-differential relay device 101b through the optical interface 14, an optical fiber 15a, an O/E unit (optical-to-electrical converter) 17a, a cable 19a, a multiplexer/demultiplexer 16a, and a signal transmission line (optical fiber) 20.
On the other hand, sampling current data that is detected by the second current-differential relay device 101b and received by the multiplexer/demultiplexer 16a through the optical fiber 20 is input to the transmission data processor 12b through a cable 19c, an E/O unit (electrical-to-optical converter) 18a, an optical fiber 15c, and the optical interface 14. The differential calculator 8 calculates a difference in electric current between the pieces of sampling current data input, that is, the sampling current data detected by the first current-differential relay device 101a and the second current-differential relay device 101b, respectively. The differential calculator 8 also transmits a signal indicating the occurrence of fault to the breaker 7a through the contact 11 if the difference is more than a predetermined value. In response to this signal, the breaker 7a cuts the current flowing the power transmission line L.
The HMI 9 receives transmission data from the second current-differential relay device 101b through the transmission data processor 12b, as shown with arrow A in
In
In
The transmission data S-1 and R-1 are sampling current data obtained by sampling the current in an electric phase angled of 30 degrees, which is the same as the conventional one, and always transmitted from the first current-differential relay device 101a and the second current-differential relay device 101b. Note that these sampling current data are transmitted over a 2048-kbps signal transmission line in place of a 54-kbps or 64-kbps signal transmission line, in the first embodiment.
The transmission frame format conforming to ITU-T G.704 will be briefly described below.
In
In
The transmission data S-3, R-3, and R-4 being the display-related data are transmitted using fields containing no sampling current data (unused fields in the transmission frame format). Since this type of setting value has a lot of information, it is transmitted with a plurality of blocks as one example in the first embodiment.
As described above, the current-differential relay devices use transmission data processor for the 2048-kbps transmission instead of that for the conventional 64-kbps transmission and always transmit the sampling current data in the transmission frame format conforming to ITU-T G.704 standard as shown in
In this way, since the current-differential relay devices according to the first embodiment transmit the display-related data (transmission data items) other than the sampling current data in the transmission frame for transmitting the sampling current data, one current-differential relay device can quickly obtain the display-related data of the other current-differential relay device and improve analysis function, without additional specific monitoring control system and without on-site operation of the other current-differential relay device.
The first current-differential relay device 101a and the second current-differential relay device 101b are connected to each other by a signal transmission line including the optical fibers 15a to 15d, the O/E units (optical-to-electrical converters) 17a and 17b, the E/O units (electrical-to-optical converters) 18a and 18b, the cables 19a to 19d, multiplexers/demultiplexers 16a and 16b, and the optical fiber 20. However, the signal transmission line connecting the first current-differential relay device 101a and the second current-differential relay device 101b is not limited to the above components, and may be provided as a direct connection between the optical interface 14 and the optical fiber 20, for example.
The transmission data S-3, R-3, and R-4 in the first embodiment are contained in unused fields, which are other than fields containing the sampling current data, in the transmission frame format as shown in
In the first embodiment, the sampling current data and the display-related data are transmitted over the 2048-kbps signal transmission line, but it goes without saying that the data can be transmitted over a signal transmission line of more than 2048 kbps.
In
In
The transmission data S-4, R-5, R-6, and R-7 are transmitted, as the display-related data of the first embodiment, using fields containing no sampling current data in the transmission frame format for the sampling current data always transmitted from the first current-differential relay device 101a. Alternatively, the transmission data are transmitted separately in the transmission frame format.
In this way, since the current-differential relay devices according to the second embodiment transmit the display-related data (transmission data items) other than the sampling current data in the transmission frame for transmitting the sampling current data, i.e., a request for transmitting an event log and the event log, one current-differential relay device can quickly obtain the event log of the other current-differential relay device and improve analysis function, without additional specific monitoring control system and without on-site operation of the other current-differential relay device.
As described above, according to the first and the second embodiments, information indicating a setting value and an event log are transmitted, as instruction data generated based on operations of the push button 22 of the front panels 23a and 23b or the personal computers 21a and 21b and response data, in the 2048-kbps transmission frame format as shown in
In contrast, current-differential relay devices according to a third embodiment transmit information indicating relay states of relay elements and device input/output signals to one another, in the 2048-kbps transmission frame format as shown in
In this way, one current-differential current relay device stores therein information indicating relay states of relay elements and device input/output signals of the current-differential current relay device and displays them as necessary, thereby improving analysis function of relay operation upon an occurrence of fault.
Current-differential relay devices according to a fourth embodiment transmit, to one another, measured value information including voltage, current, phase, active power, reactive power, power factor, differential current, suppressor current, and the like, as instruction information and response information of the HMI 9, in the 2048-kbps transmission frame format as shown in
Accordingly, one current-differential relay device allows the measured information of the other current-differential relay device to be displayed as necessary, and it is advantageous to obtain states of the system.
Current-differential relay devices according to a fifth embodiment transmit software version information, as instruction information and response information of the HMI 9, to one another in the 2048-kbps transmission frame format as shown in
Accordingly, one current-differential relay device allows the software version information of the other current-differential relay device to be displayed as necessary, and it is advantageous to management the system.
In current-differential relay devices according to a sixth embodiment, one current-differential relay device sets a setting value of the other current-differential relay device based on operations of the push button 22 of the front panels 23a a d 23b or the personal computers 21a and 21b. In
In
In this way, according to the sixth embodiment, one current-differential relay device transmits the request for setting a setting value in the transmission frame for transmitting the sampling current data to set the setting value on the other current-differential relay device. Accordingly, the one current-differential relay device can quickly set the setting value on the other current-differential relay device and facilitate system management, without additional specific communication medium and without on-site operation of the other current-differential relay device.
In
In the seventh embodiment, the time synchronization is based on the time information obtained from the GPS receiver 51. Alternatively, the current-differential relay devices may use other accurate time, for example, time information provided by a broadcast station or a radio wave clock, and time information input from the front panels 23a and 23b or the personal computers 21a and 21b.
In this way, according to the seventh embodiment, one current-differential relay device transmits the time information used for time synchronization in the transmission frame for transmitting the sampling current data to the other current-differential relay device. Accordingly, the time synchronization between the one current-differential relay device and the other current-differential relay device can be performed easily.
According to the embodiment of the invention, since transmission data (display-related data) other than the sampling current data is transmitted with a transmission frame for transmitting the sampling current data, one current-differential relay device can quickly obtain various data on the other current-differential relay device and improve analysis function in relay operation, without additional specific monitoring control system and without on-site operation of the other current-differential relay device.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
Number | Date | Country | Kind |
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2007-160764 | Jun 2007 | JP | national |
2007-337980 | Dec 2007 | JP | national |