JPH0727599B2 - Synchronous method of measurement information at different points - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synchronizing different-point measurement information for synchronizing each piece of information independently measured at different points and using it for processing of development analysis and characteristic comprehension.

[Prior art]

A plurality of pieces of measurement information measured at different points are used for monitoring the state of the electric system and for protection control. Although this measurement information changes when a failure or the like occurs in the target system, not only the measurement information when the change occurs but also the measurement information after the change may be needed. For example, in the fault location, the value of the ongoing fault is used as the measurement information. For this reason, conventionally, the measurement information measured at different points is collected at one location and used for the processing of development analysis and characteristic grasp.

[Problems to be Solved by the Invention]

However, according to such a method, since the start phase of each sampling is different, the measurement information at each point is not synchronized, and thus there is a problem in accuracy of development analysis and characteristic grasp. Especially in fault location, since the measurement information measured at each terminal of the system is a vector quantity, it is necessary to synchronize the measurement information at each point when performing vector calculation. When the synchronous sampling method is used to achieve simultaneity between measurement information, a synchronous signal transmission / reception circuit is required, and in the asynchronous sampling method, a phase correction circuit for sampling data by instantaneous failure detection is required.
There was a drawback that the hardware increased and the cost increased. In view of the above, the present invention sets the measured values at different points to 1
It is necessary to provide a synchronization method for different-point measurement information that enables the same relation in time, that is, the same treatment as that of synchronized measurement, when the data are collected and used at one place or multiple different places. It is an issue.

[Means for Solving the Problems]

A terminal device is installed at each terminal of a power transmission system composed of three or more terminals, and each terminal device measures the voltage value and current value of its own terminal asynchronously at a constant cycle. In the one that transmits the value to one place and performs the development analysis of the system and the process of grasping the characteristics, the voltage drop per unit length of the transmission system between each terminal and the branch,
The voltage of each terminal is calculated using the voltage value of each terminal and the distance between each terminal and the branch, the phase difference of each voltage of the calculated branch is calculated, and each phase difference is used. The voltage values and current values measured by each terminal device are synchronized with each other.

[Action]

Using the voltage drop per unit length of the transmission system between each terminal and the branch, the voltage value of each terminal, and the distance between each terminal and the branch, the voltage of each branch as seen from each terminal is calculated. If found, the phases of the respective voltages should be the same, so by obtaining the phase difference of the respective voltages, synchronization can be achieved using this phase difference.

Examples of the invention

FIG. 2 shows an equivalent circuit per unit length of each phase of an asymmetric three-phase circuit in a three-terminal system, one line, Z _aa , Z _bb ,
Z _cc is the self-impedance of each phase per unit length, Z _ab ,
Z _bc and Z _ca represent the in-line mutual impedance per unit length between the ab phase, the bc phase, and the ca phase. Here, the current flowing in the a, b, and c phases measured at the A terminal, B terminal, and C terminal is
If I _a ^A , I _b ^A , I _c ^A , I _a ^B , I _b ^B , I _c ^B , I _a ^C , I _b ^C , I _c ^C , then from the A terminal, B terminal and C terminal by each current. Each voltage drop per unit length of each phase up to the fault point can be expressed as follows. Here, assuming an a-phase one-line ground fault and assuming the fault point resistance to be R _F , the equivalent circuit diagram at that time is as shown in FIG. However, the distance between A terminal and branch P is L ^A , B terminal to branch P
Distance L ^B between, and distance L ^C between the C terminal-branched P, fault point is between the branch P and A terminals, as the distance .alpha.L ^A from A terminal (where 0 <α <1) There is. When considering the a phase, the potential V _a ^P of the branch P viewed from each terminal is expressed as follows. (From terminal A) V _a ^P = V _a ^A −L ^A V _aa ^A …… (4) (From terminal B) V _a ^P ＝ V _a ^B −L ^B V _aa ^B …… (5) (From terminal C) ) V _a ^P = V _a ^C −L ^C V _aa ^C (6) Equation (4) = (5) Equation = (6) Equation (6) when there is no failure and is sound. On the other hand, when a failure occurs in the section AP as shown in FIG. 1, since this failure is an a-phase 1-line ground failure, equation (4) ≠ (5) = equation (6). , B, C terminals have the same potential of the branch P. Since the voltage value, the current value, and the impedance value used in the above calculation are vector quantities, the potentials of the equations (4) to (6) are calculated.
V _a ^P also becomes a vector value and has magnitude and phase. The magnitude and phase of the potential V _a ^P of the branch P seen from each terminal are Then, from the equation (5) = the equation (6), | V _a ^PB | = | V _a ^PC | (8) θ _a ^PB = θ _a ^PC (9) However, since the sampling data is not synchronized with the data between each terminal, the actual calculated data is ^│V _a ^PB │ = │V _a ^PC │ (10) θ _a ^PB ≠ θ _a ^PC ... (11) Here, focusing on the phase, the phase difference Δθ _a ^BC due to the non-synchronization of sampling is represented by Δθ _a ^BC = θ _a ^PB −θ _a ^PC (12). Therefore, it is possible to synchronize the B terminal and the C terminal by using this Δθ _a ^BC . For example, assuming that the current value flowing from the branch point P to the fault point F is I _a ^P , I _a ^P is represented by the vector sum of the current I _a ^B flowing from the B terminal and the current I _a ^C flowing from the C terminal, and therefore the position When the current values of the B and C terminals are synchronized using the phase difference Δθ _a ^BC ,
It looks like this: ^{_{| I a P | ∠φ a P}} = | i a B | ∠φ a P + | I a C | ∠ (φ a C + Δ
φ _a ^BC ) ... (13) However, in the equation (13), φ _a ^P and φ _a ^C represent the measurement phase of each current value. Therefore, considering the terminal B as a reference, the voltage and current values at the branch point can be expressed by equations (5) and (13). Similarly, when a B-phase or C-phase fault, a two-line short circuit, or a two-line ground fault, attention can be paid to each fault phase to synchronize the sound sections. In this way, the three-terminal system can be reduced to a two-terminal system (the voltage and current values at the branch P point can be obtained). Method, the two terminals can be synchronized with each other, so that all three terminals can be synchronized with each other if necessary. Furthermore, it is clear that the same thing can be done by using the sound phase instead of the failure phase when there is a sound phase other than the three-wire short circuit. In this way, the collected asynchronous data between terminals can be synchronized by collecting the data in one place and performing the calculation. In the above description, the three-terminal system one line is described, but the three-terminal system parallel two lines can be handled similarly. FIG. 3 shows an equivalent circuit diagram per unit length regarding a phase of an asymmetrical three-phase line in a three-terminal system parallel two-line. In the figure, Z _aa , Z _bb , and Z _cc are the self-impedances of each phase per unit length of the 1L line, and Z _ab and Z _ca are the mutual impedances per unit length between the ab and ca phases of the 1L line.
_aa ′, Z _ab ′, and Z _ca ′ indicate the line impedance between the a phase of the 1L line and each phase of the 2L line. In addition, here 1L
In order to explain the a-phase failure of the line, the mutual impedance of the other phases and the line-to-line mutual impedance are omitted. Here, a, b, c of 1L line and 2L line measured at A, B, C terminals
The currents flowing in the phases are I _a ^A , I _b ^A , I _c ^A , I _a ^B ,
I _b ^B , I _c ^B , I _a ^C , I _b ^C , I _c ^C , I _2a ^A , I _2b ^A , I _2c ^A , I _2a ^B , I
_2b ^B , I _2c ^B , I _2a ^C , I _2b ^C , I _2c ^C
Voltage drop per unit length of 1L line a phase from terminal, B terminal and C terminal to fault point V _aa ′ ^A , V _aa ′ ^B , V _aa ′ ^C
Can be expressed as follows. The other phases can be similarly expressed. Here, assuming an a-phase 1-line ground fault between sections AP and assuming the fault point resistance to be R _F , synchronization can be performed in the same manner as the above-described 3-terminal 1-line.

According to the present invention, not the synchronization by the hardware but the synchronization by the operation using only the collected data is performed. Therefore, the hardware such as the synchronization signal transmitting / receiving circuit and the phase difference correction circuit can be realized. It becomes unnecessary and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram in the case of a phase 1 wire ground fault, and FIG.
Equivalent circuit diagram per unit length of each phase of asymmetric three-phase circuit in one line of terminal system, Fig. 3 is equivalent circuit diagram per unit length of each phase of asymmetric three-phase circuit in three-terminal system parallel two line Z _aa , Z _bb , Z _cc ... self impedance, Z _ab , Z _bc , Z _ca ...
Mutual impedance in line, Z _aa ′, Z _ab ′, Z _ca ′ ... Mutual impedance between lines, L ^A ... Distance between terminal A and branch P,
L ^B ... B terminal-branch P distance, L ^C ... C terminal-branch P distance.

Claims (1)

[Claims] 1. A terminal device is installed at each terminal of a power transmission system composed of three or more terminals, and each terminal device measures the voltage value and current value of its own terminal asynchronously at a constant cycle. In the case of transmitting the voltage value and current value of 1 to one place to analyze the phenomenon of the system and grasp the characteristics, etc., the voltage drop per unit length of the transmission system between each terminal and the branch, Using the voltage value of the terminal and the distance between each terminal and the branch, the voltage of the branch seen from each terminal is obtained, and the phase difference of each voltage of the obtained branch is obtained,
A method of synchronizing different-point measurement information, characterized in that voltage values and current values measured by each terminal device are synchronized using the phase difference.