JPH0221399A - Synchronizing system for measuring information in different spots - Google Patents

Abstract

PURPOSE:To make hardware such as a synchronizing signal transmitting and receiving circuit and a phase difference correcting circuit unnecessary by obtaining a synchronization by an operation using only collected data instead of obtaining the synchronization by the hardware. CONSTITUTION:When the voltage of a branch P is respectively obtained from respective terminals A-C using each amount of voltage drop per unit length of the transmission system between each of the respective terminals A-C and a branch P, the voltage values of the respective terminals A-C, and distances LA-LC between the respective terminals A-C and the branch P, the phases of the respectively obtained voltages are to be equal. Thereupon, the synchronization can be obtained by obtaining the respective phase differences between the respective voltages and using the phase differences. Thus, the synchronizing signal transmitting and receiving circuit and the phase correcting circuit for sampling data can be made unnecessary.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for synchronizing information measured at different points for synchronizing each piece of information independently measured at different points and using the information for analyzing phenomena and understanding characteristics.

[Conventional technology]

Multiple pieces of measurement information measured at different locations are used to monitor the status of power systems and for protection control. This measurement information changes when a failure or the like occurs in the target system, but not only the measurement information at the time of the change, but also the measurement information after the change is sometimes required. For example, when locating a failure point, values during a continuing failure are used as measurement information. For this purpose, conventionally, measurement information measured at different points was
It is collected at certain locations and used for processing phenomena analysis and characterizing.

[Problem to be solved by the invention]

However, according to this method, since the starting phase of each sampling is different, the measurement information at each point is not synchronized, and therefore there is a problem in the accuracy of phenomenon analysis and characteristic understanding. Particularly in fault point 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 calculations. When using the synchronous sampling method to ensure simultaneity between measurement information, a synchronous signal transmission/reception circuit is required, while the asynchronous sampling method requires a phase correction circuit for sampled data by detecting instantaneous failures.
The drawback is that the hardware increases, which increases costs. In view of the above, the present invention has developed a system in which each measurement value at a particular point is
To provide a method for synchronizing measurement information at different points, which makes it possible to treat each relationship as being the same in time, that is, equivalent to synchronous measurement, when the information is collected at one location or at multiple different locations. Take it as a challenge.

[Means to solve the problem]

A terminal device is installed at each terminal of a power transmission system composed of multiple terminals of three or more, and each terminal device measures the voltage and current values of its own terminal asynchronously and at regular intervals, and calculates these voltage values and current. In systems where values are transmitted to one location for processing such as system phenomenon analysis and characteristic understanding, the voltage drop per unit length of the power transmission system between each terminal and branch,
Using the voltage value of each terminal and the distance between each terminal and the branch, find the voltage of the branch as seen from each terminal, find the phase difference of each voltage of the found branch, and calculate the phase difference. synchronize the voltage and current values measured by each terminal device.

[For use]

Using the voltage drop per unit length of the power transmission system between each terminal and branch, the voltage value of each terminal, and the distance between each terminal and branch, calculate the voltage of the branch as seen from each terminal. When determined, the phases of the respective voltages should be equal, so by determining the phase difference between the respective voltages, synchronization can be achieved using this phase difference.

[Embodiments of the invention]

Figure 2 shows the equivalent circuit per unit length of each phase of an asymmetric three-phase circuit in one line of a three-terminal system.
Z bb * zcc is the self-impedance of each phase per unit length, and Z mb+ Z bt+ Z c@ is the ab phase interval. 9 intra-line mutual impedances per unit length between bc and ca phases are shown. Here, the A terminal. The current flowing in the a, b, and c phases measured at the B and C terminals is ＾Ab”AC＾+ 1 m”+ I k”+ I
cl+I IC+IbC,I. Assuming that C, each voltage drop per unit length of each phase from the A terminal, B terminal, and C terminal to the failure point due to each current can be expressed as follows. Here, assuming an A-phase L-line ground fault, the fault point resistance is R2
Then, the equivalent circuit diagram at that time is as shown in FIG. However, the distance between A terminal and branch P is L^, the distance between B terminal and branch P is L", the distance between C terminal and branch P is LC, and the failure point is between A terminal and branch P. The distance is αL^ from the A terminal (however, α<1). When considering the a phase, the potential v,' of the branch P seen from each terminal is expressed as follows. (A From terminal) V, PV, A-LAV, -------(
4) (From B terminal) ■1 day V, "-L" V
1. ” −−−−−(5) (from C terminal) V, '=V
, C-LcV, , c---(6) When there is no failure and in good condition, equation (4) = equation (5) = equation (6). On the other hand, if a fault occurs in section AP as shown in Figure 1, this fault is an a-phase 1-wire ground fault, so equation (4) ≠ equation (5) = equation (6). , B, and C terminals become equal. Since the voltage value, current value, and impedance value used in the above calculations are vector quantities, the potentials V and P in equations (4) to (6) are also vector values, and have magnitude and phase, as seen from each terminal. If the magnitude and phase of the potential vI of the branch P are, then from equation (5) = equation (6), V, "l = I V, Pcl - - (8) θ
, ``=θ, PC・−・−(9) are established respectively. However, since the data between each terminal is not synchronized in sampling, the data actually calculated is V, ” l = l V, rcl −−−−−0ωθ
1 ■ Ki θ, PC--...01) Here, if we focus on the phase, the phase difference Δθ, IC due to the lack of synchronization in sampling is Δθ1IIC=et, Pa-θ, PC,,-,-,02
). Therefore, using this Δθ1■, the B terminal and C terminal can be synchronized.0For example, if the current values flowing from the branch point P to the fault point F are l and P, then l and P are the currents flowing from the B terminal. ! , ', and the vector sum of the current I- flowing from the C terminal, so if the phase difference Δθ, Ic is used to synchronize the current values of the B and C terminals, the following is obtained. 121kuφ,'=li,"l<φm'+1I-1ku(φ
J+Δθ,'C)−・−・・−031 However, in equation 0, φ, ′, and φ− indicate the measurement phase of each current value. Therefore, considering the B terminal as a reference, the voltage and current values at the branch point can be expressed by equation (5), Q:1. Similarly, in the event of a B-phase or C-phase failure, 2-wire short circuit, or 2-wire ground fault, it is possible to synchronize the healthy sections by focusing on each failed phase. In addition, in this way, a three-terminal system can be reduced to a two-terminal system (the voltage and current values at the branch point P can be determined), and this allows for the "synchronization in fault point location calculation" filed on the same date as the present application. Since the synchronization between two terminals can be performed using the "method", all three terminals can be synchronized if necessary. Furthermore, it is clear that if a healthy phase exists other than a three-wire short circuit, the same thing can be done using the healthy phase instead of the faulty phase. In this way, synchronization can be achieved by collecting the collected terminal-to-terminal asynchronous data in one place and performing calculations. In the above explanation, a three-terminal system with one line has been described, but a three-terminal system with two parallel lines can also be handled in the same way. FIG. 3 shows an equivalent circuit diagram per unit length regarding the a-phase of an asymmetric three-phase line in a three-terminal parallel two-line line. In the figure, Z ma, Z bb + Z EC is 11
Self-impedance of each phase per unit length of line, Za
b+ZCm is the mutual impedance per unit length between the ab and ca phases of the 11 lines, Z amZ ah '
+Z CIR' indicates the line impedance between the a phase of the 11 lines and each phase of the 2L line. Note that in order to explain the a-phase failure of 11 lines, mutual impedances of other phases and mutual impedances between lines are omitted here. Here, 11 lines measured at A, B, and C terminals. The currents flowing in the a, b, and c phases of the 2L line are each 1
, A+ I k”+ I C^+ F”+ 1b”+
rc"1 tm'l lb + IC12m'+ I
! ni'+ I zc^* I! I”+ r tk”+
I IC”+ I 2ac+1 tbc+ I I
C", the voltage drop per unit length of the IL line a phase from the A terminal, B terminal, and C terminal to the failure point F due to each current V am '" + V aa '8Van'
′ can be expressed as follows. Note that other phases can be similarly expressed. Here, assuming an a-phase one-line ground fault between sections AP, and assuming that the fault point resistance is Rr, synchronization can be performed in the same manner as in the three-terminal system one line described above.

【Effect of the invention】

According to the present invention, synchronization is not performed by hardware, but by calculation using only the collected data, which eliminates the need for hardware such as a synchronization signal transmission/reception circuit or a phase difference correction circuit, reducing costs. can be reduced.

[Brief explanation of the drawing]

Figure 1 is an equivalent circuit diagram at the time of an A-phase l line ground fault, and Figure 2 is a 3
The equivalent circuit diagram per unit length of each phase of an asymmetric three-phase circuit in one terminal system circuit. Figure 3 is the equivalent circuit diagram per unit length of each phase of an asymmetric three-phase circuit in two child lines of a three terminal system. Z m□Z bb+ Z ee ”-'Self impedance, Z a b *ZbelzCM-・-Intra-line mutual impedance, Z□Z ah ' + zca ”
- Mutual impedance between lines, l, AA end terminal branch 2
Distance L'' - Distance between terminal 8 and branch P, LC... Distance between terminal C and branch P.

Claims (1)

[Claims] 1) A terminal device is installed at each terminal of a power transmission system composed of multiple terminals of three or more, and each terminal device measures the voltage and current values of its own terminal asynchronously and at regular intervals,
In systems where these voltage and current values are transmitted to one location for processing such as system phenomenon analysis and characterizing, the voltage drop per unit length of the power transmission system between each terminal and branch, Using the voltage value of each terminal and the distance between each terminal and the branch, find the voltage of the branch as seen from each terminal, find the phase difference of each voltage of the found branch, and calculate the phase difference. A method for synchronizing measurement information at different points, characterized by synchronizing voltage values and current values measured by each terminal device.