JP2564414B2 - Power system accident aspect identification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention calculates the position of an accident point and the accident point resistance when an accident occurs in a power system such as a transmission line or a substation, and determines the cause of the accident. The present invention relates to an accident aspect identification device of a power system for searching.

[Conventional technology]

Conventionally, as this type of device, the fault point locating method using the voltage and current signal of one terminal to which the reactance relay and the line selection relay method, which are the technology of the protective relay method, has been the mainstream, and the fault point resistance is calculated. An accident point locator that simply calculates the position of the accident point (distance from one of the terminals to the accident point) without doing so is shown by Electric Cooperation Research Vol. 41, No. 4 (issued in January 1986). ing.

[Problems to be Solved by the Invention]

However, in the application of the above-mentioned protective relay system technology, since only the voltage and current signals of one terminal are used, there is an error in the reference value depending on the connection status of the power supply and impedance of the other terminal side. May bring.

Also, when measuring a signal, it is conceivable that the error of the instrument transformer may affect the orientation value. Furthermore, since there is no means for calculating the accident point resistance, there is a lack of search information for the cause of the accident.

Therefore, the present invention has been made based on the above circumstances, and provides an accident aspect specifying device of a power system that reduces an accident point locating error and calculates an accident point resistance to estimate an accident cause. To aim.

[Means for solving the problem]

The above-mentioned object is a terminal installed in a specific section of a power system having a plurality of phases, a time-series data collecting means for collecting time-series data of voltage and current signals for each phase detected by the terminal, and time-series data. A voltage equation is created for each phase from the power system, and the fault condition of the power system is composed of a central unit that has the position of the fault point of the power system and a calculation means for identifying the fault condition from the fault point resistance for each fault phase of the power system. In the specific device, the calculating means sets an error term for reducing the measurement error of the time series data in the voltage equation for each phase, sets an objective function that minimizes the sum of squares of the error terms, and sets the objective function for each phase. The characteristic is to reduce the measurement error of the time-series data by transforming the voltage equation of to the partial differential equation and solving it.

[Action]

In the accident aspect specifying device of the power system according to the present invention, the fault point resistance for each fault phase of the power system is calculated, and the error is set after setting the error term for reducing the measurement error in the voltage equation used for the orientation calculation. Therefore, it is possible to reduce the error of accident location.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram showing an embodiment of the present invention. The embodiment of the figure shows a system configuration in a three-phase AC parallel two-line two-terminal system, which is the most basic transmission line configuration. The symbols in the figure and their operation contents will be described. 1L is the transmission line No. 1 and 2L is also the transmission line No. 2, and each is shown as a single line, but in the three-phase AC transmission line, each is constructed by three-phase three-line drawing. The length of the transmission lines 1L and 2L is set to l ₀ (km), and when a fault such as a short circuit or a ground fault occurs on this length, the fault point and fault point resistance are calculated. TR indicates transformers, and although these transformers are not shown, a power source or a load is connected to each. Z _S , Z _R
Are the neutral grounding impedances of the transformers TR and S of the S and R terminals, respectively.

CB is a circuit breaker and is usually installed for each three-phase AC phase. The CT is a current transformer, which is used to incorporate information on the current flowing through the transmission line into the system of the present invention, and is provided for each phase. The PT is a transformer, and is for taking in voltage information of each terminal of the transmission line. In this embodiment, the transformer PT is arranged to measure the bus voltage of each terminal, but it is installed on the transmission line side of the circuit breaker CB, that is, on the line side that can detect the voltage at the same point as the current transformer CT. If a transformer is provided, it is convenient to use it because the applied voltage information of the line can always be input regardless of whether the circuit breaker CB is opened or closed.
These voltage signals are taken in for each phase of each terminal. 100 and 200
Are terminals provided at the S terminal and the R terminal, respectively, and have a memory unit capable of storing the voltage and current signals of the terminal itself, the open / close state signal of the circuit breaker CB, and the like. It is composed of signal input units 110 and 210 having a function of converting a waveform of a commercial frequency into digital amounts by sampling every 30 degrees, and transmitting devices 150 and 250 capable of transmitting and receiving signals between both terminals. 310 is a data transmission line,
It is for transmitting information of the S terminal and the R terminal, and for example, a telephone line, a microwave line, an optical communication line or the like can be used. Reference numeral 500 denotes a central device, which is a part for calculating the position of the accident point and the accident point resistance, which are the calculation purposes in the present invention. Information such as voltage and current signals of the S terminal and R terminal, an open / closed state signal of the circuit breaker, etc. is input to the central device 500, and the result of the above arithmetic processing is output to a control station or a power feeding command station. 320 is a data transmission line, and the central unit 500
It is used to output the results of arithmetic processing in, or to transmit the settling constants from the control station, the power supply command station, etc., and the signals for monitoring whether or not there is an abnormality in the equipment. As will be described later, the voltage and current signals used in the present invention are converted into a complex number format based on the time-series sample values synchronized with each terminal and used for the calculation as the values of the real number part and the imaginary number part.
The signal input units 110 and 210 shown in the figure may convert the input signals into complex numbers and then transmit the signals in the complex number format to the central unit 500 using the transmission units 150 and 250. Alternatively, any one terminal, for example, the S terminal side, may collect an instantaneous sample value of the signal of each terminal, convert the signal into a complex number format in the central device 500, and perform necessary calculation. Further, the signal input units 110 and 210 may perform digital conversion of independent levels for the phenomena of the ground fault and the short-circuit fault according to the system configuration. For example, in the neutral point resistance grounding system, the ground fault current is at a relatively low level compared to the short circuit current. Therefore, when the signal input full scale is set lower than that for short circuit and the signal is input by digital conversion. Quantization noise can be reduced.

Next, a specific example of the calculation method will be shown. First, a constraint matrix is created based on the voltage and current signals at each terminal. FIG. 2 shows each phase of the three-phase AC parallel two-line power transmission line shown in FIG. In FIG. 2, 1L of the 1st line shown in FIG. 1 is indicated by phase Nos. 1, 2, 3 and 2L of the 2nd line by phases Nos. 4, 5, and 6. The voltage signals V ₁ , V ₂ ... V _{12 of} the S and R terminals and the current signals I ₁ , I _2, ... I ₁₂ are shown by subscripts so as to correspond to the phase order. l ₀ indicates the line length (km) from the S terminal to the R terminal. k is the distance to the accident point, and is shown by the ratio of the line length l ₀ to 1 with the S terminal as the base point, and k = 0, when the S terminal near end accident.
R = near end accident k = 1, mid-point accident k = 0.5
It is expressed as. R ₁ , R ₂ ... R ₆ , R _E are the accident point resistances of each phase, and R _E is the common accident point resistance of the accident phase. E ₁ , E ₆ , ... E ₁₂ are also related to the voltage drop of the line of each phase not shown. Is represented by

_{However, Z 11, Z 12 ... Z} 66 is 1km per impedance between the transmission line phase, between each phase, as shown in FIG. 3 consists impedance Matricaria try a symmetric, here to simplify the description Has a uniform distribution constant over the span of l ₀ (km). In the equation (1), the voltage signals V ₁ , V ₂ ... V
₁₂ and current signals I ₁ , I ₂ , ... I ₁₂ , impedance Z ₁₁ , Z ₁₂ … Z
₆₆ is a complex number, and E ₁ , E ₂ ... E ₁₂ are also plural primes. The current flowing through the fault point resistance R _E shown in I _E, it is _{I E = I 1 + I 2} + ... + I 12 ... (2).

In Fig. 2, voltage equation of each phase of each terminal Holds.

Equation (3) includes complex numbers, but the unknowns are k, which indicates the position of the accident point, and the accident point resistances R ₁ , R ₂ ... R ₆ , R _E of each phase, which are scalar quantities. The crossover length l ₀ and the line impedance matrix Z ₁₁ , Z ₁₂ ... Z ₆₆ are values peculiar to the line to be identified as the accident aspect and can be input in advance as settling values. l ₀ is a scalar quantity and Z ₁₁ , Z ₁₂ … Z ₆₆ are complex numbers. Further, the voltages V ₁ , V ₂ ... V ₁₂ are complex numbers, and the measured values and currents I ₁ , I ₂ ... I
_{12 is} also a complex number and is a measured value. Since there are eight unknowns, the position k of the accident point and the accident point resistances R ₁ , R ₂ ... R ₆ , R _E necessary for identifying the accident aspect can be obtained by directly solving the equation (3). Also, addition of these values which can be calculated for each time section, the voltage, the current value of the measurement time time t Distant, unknown respectively _{k (t), k 1 (} t) ... and independently k _{E (t)} Alternatively, all the measured values can be solved as simultaneous equations in the same manner as the equation (3). The position of the accident point is assumed to be constant during one accident and k does not change.
Only R ₁ , R ₂ ... R _E may be solved as unknowns independent for each time section. In addition, assuming that the average value of the position k ( _t ) of the accident point calculated at each time section is k, and substituting for the unknown k, the resistance R ₁ ( _t ), R ₂ ( _t ) of the accident point for each time section…
A method of recalculating R _E ( _t ) may be used. Although the method of directly solving the equation (3) has been described above, since each equation of the equation (3) uses the measured values of the voltage and current signals, it is conceivable that the measurement error may be included.

Hereinafter, an example of the arithmetic processing method for reducing the influence of the measurement error will be described. Equation (3) is expressed as a simultaneous equation in which a complex number equation is separated for a real time part and an imaginary number part for a certain one-time cross section. You can put 24 simultaneous equations like this. However, X _1r , X _1i , and X _12i are error terms of each equation. The subscript r indicates the real part and i indicates the imaginary part. The following symbols are expressed in the same way. However, in equation (4), if all phases are in an accident, the accident point resistances R ₁ , R ₂ ... R _E
However, when there is a phase without an accident, the resistance at the accident point is infinite and the sum current of both terminals becomes zero, which causes a problem in solving the simultaneous equations.

In the present invention, the equation (4) is modified to far.

In the equation (5), U _1r , U _1i , U _2i ... U _6i , U _Er , U _Ei are correction terms. When the correction term U _1r is combined with the term of R ₁ (I ₁ + I ₇ ) _r , when an accident occurs in phase No. ₁ , R ₁ (I ₁ +
Enable the section I _{7) r,} to excisional for example U _1r = 0 as to invalidate the U _1r. If phase No. 1 is considered to be sound, conversely, the term of R ₁ (I ₁ + I ₇ ) _r is invalidated and the term of U _1r is used as an unknown. The same applies to the other phases. That is, the accident phase uses the term of resistance R, and the sound phase uses the correction term U. The same applies to the term of the fault point resistance R _E of the respective phases common ground fault, using the section section and U _E of R _E in conflicting requirements. Equation (5) is solved by the above method. By the way, the error terms X _1r , X _1i
When X _12i is considered to be a random value, the objective function to solve equation (5) is calculated by the method of least squares. Then, the solution of the equation (5) under the condition that the sum of squares Q of the error terms is minimized is obtained.

There are various conceivable quadratic programming methods for solving the above-mentioned constraint equation (5) and objective function (6), but in the present invention, the partial differential method described below is used as an example. It is used.

That is, the objective function of equation (6) is defined by variables k, R ₁ , R ₂
… The value differentiated by R _E The condition is satisfied. However, for the sound phase, the correction term U is used instead of the accident point resistance R as described above. The coefficient of the correction term U is 1.

For example, the partial differential equation with the position k of the accident point as a variable is You can put it.

Since ▲ X ² _1r ▼, ▲ X ² _1i ▼, ... ▲ X ² _12i ▼ in equation (8) can be obtained from each equation in equation (5),
Equation (8) can be solved. Also, the accident point resistances R ₁ , R ₂
… The partial differential equation by R _E also sets the variable k in Eq. (8) to R ₁ , R ₂ ,.
Required by switching to R _E. Therefore,
The solution of the variable satisfying the equation (7) is obtained. Of course, the constraint condition equation (5) is a linear equation, and the partial differential equation (7) is also a linear equation, and a solution can be easily obtained by using a computer.

FIG. 4 is a calculation flow chart showing an embodiment of the calculation method of the present invention using a digital computer. In the figure, step 40 is for setting the system data. The value of line length l ₀ , line impedance matrix
Z ₁₁ , Z _12, ... Z ₆₆ , and other data such as the output format of the calculation result, which can be input as preset values necessary for the calculation processing, are set. Step 41 represents an accident detection and data collection step. The accident detection is for detecting the occurrence of an accident in the target system of the accident aspect specifying device, and may be, for example, a direction distance relay or a current differential type carrier relay used as a system protection relay. When an accident is detected by accident detection, each terminal voltage and current signal is transformed into digital data by sampling synchronized with each terminal and collected. At least data will be collected from the time the accident occurs until the accident is cleared. When collecting data at each terminal, depending on the short-circuit capacity of the power system, the neutral point grounding resistor current, etc., there may be a ground fault with a relatively small fault current and a short-circuit fault with a relatively large fault current. There is also a method of preparing a plurality of data groups with different levels per bit for digital conversion. The same applies to the digital conversion of the voltage signal. Step 42 is for determining the type of accident, and is used as information for determining whether the short-circuit accident or the ground fault has occurred and selecting the use destination of the data collected in the previous step 41. Step 43 shows a data selection process, in which the data necessary for the arithmetic processing is selected and fetched from the collected data in accordance with the accident type determined in the previous step. Step 44 is a line voltage matrix creation process. Based on the data input through each of the above steps, the known equations are substituted into the simultaneous equations (5) to create the voltage equation matrix. .

Of course, since the data used here is expressed in the real part and the imaginary part, a reference vector is set in advance based on the voltage and current signals obtained by sampling synchronized at each terminal, and On the other hand, the real part and the imaginary part of each complex signal are separated to form the equation (5). The data of the real number part and the imaginary number part may be created in step 41 or step 44 in FIG. In step 44, 1
An example of creating the voltage equation matrix of equation (5) at the time of sampling is shown, which is an example of a method of obtaining a solution at each one time cross section. Step 45 is for performing an accident phase discrimination calculation. As the accident phase discrimination calculation means,
The sum of the current signals at both terminals is obtained for each phase, and when the value exceeds a predetermined determination level I _P , it is determined that the phase is an accident within the section of the length l ₀ . This is an accident phase determination method based on the current differential method of a protection relay to which Kirchhoff's first law is applied. Here, the judgment level I _P is a settling value for preventing erroneous judgment for errors in current signal measurement, charging in the section of length l ₀ , and other noise, and is determined according to the magnitude of the passing current. It may be the same as the protection relay of the comparison differential system in which the judgment level I _P can be changed. Further, the current differential input signal for judging the accident phase may be either a sample value itself, that is, a judgment based on an instantaneous value, a judgment in a complex number format, or a judgment of the real part and the imaginary part individually. Alternatively, it may be based on the matching condition or the OR condition of the above determination method. In addition, the level of the current I _E flowing through the common resistance R _E shown in FIG. 2 is determined to determine whether a ground fault has occurred. The level judgment value of the current I _E is also used to prevent misjudgment, like the judgment level I _{P of} each phase. Step 46 is the position k of the accident point, the accident point resistance of the accident phase R ₁ , R ₂ … R
The values k ( _t ), R ₁ ( _t ), R ₂ ( _t ) ... R at one time t of _E
This is a step of calculating _E ( _t ). At step 46,
According to the accident phase discrimination determined in step 45, the terms of each accident point resistance R ₁ , R ₂ ... R _E and the correction terms U ₁ , U ₂ ... U _E described in equation (5)
After performing the valid / invalid processing for the item of (7)
As described in the equations and the equation (8), the unknowns are obtained by converting the equation (5) into the partial differential equation. However, if the line is disconnected from the system from the circuit breaker switching status signal, this is excluded from the simultaneous equations of the voltage equation.
The result calculated in step 46 becomes a solution for each sampling value, and the accident aspect can be specified in chronological order. However, it is conceivable that the influence of the measurement error differs for each sample value. For example, the position k of the accident point occurring in the power system may be fixed and only the resistance of the accident point may change. Therefore, it is inconvenient for the position k of the accident point to change for each sample value. For this reason, the correction calculation is performed in steps 47 and 48 as the second calculation step. Step
At 47, the average value of the position k ( _t ) of the accident point at each sampling time calculated at step 46 is calculated. After that, assuming that the position of the accident point is at the average value,
Step 48 calculation starts. In step 48, by making the position k of the accident point known with an average value, the re-establishment of the accident point resistances R ₁ ( _t ), R ₂ ( _t ) ... R _E ( _t ) at each restart time is performed. Calculate. Step 49 is a step for outputting the calculation result described above. Here, the measured voltage and current signals of each terminal and the calculation result are output to a control station, a substation, a power supply command station, or the like that requires the data. It also controls data storage. As described above, the calculation flow of FIG. 4 is continued every time a system fault occurs until the fault is cleared.

FIG. 5 shows an embodiment relating to the system configuration of the present invention. This figure shows an example of the system configuration on the S terminal side described in FIG. 1, which is a collection of the terminal 100 and the central device 500 of FIG. 1 and serves as a master station for other terminals. It is a thing. In FIG. 5, the same symbols as in FIG. 1 indicate the same items as in FIG. 1, respectively. The symbols and operation contents of FIG. 5 will be described below. Reference numeral 400 indicates the master station part of the S terminal system. The master station 400 has, in addition to the signal input section of its own terminal, transmission and reception of signals from other terminals, an accident aspect identification calculation function which is a central device, and a display function. The contents of the master station system 400 will be further described. 111 is an A / D converter, which converts the voltage of the S terminal, the current signal, and the open / close state signal of the circuit breaker CB into a digital amount and fetches it. A / D converter 1
Although 11 has been described above, a plurality of configurations in which conversion levels are changed for short-circuit accidents or ground fault accidents may be adopted. Reference numeral 112 is an oscillogram, which is used for recording and displaying signals input by the master station 400. Reference numeral 113 is a protection relay device for the transmission lines 1L, 2L, and in some cases, shares an input signal with the system of the present invention, and is for using the judgment result of the protection relay device 113 for accident aspect identification calculation. . For example,
The determination result of the protective relay device 113 can be used as an input signal for determining the accident phase, short circuit, ground fault, and the like. Reference numeral 114 denotes a memory, which is used to store input signals, received signal data, transmitted signal data, and the like. 115 is a data processing unit. The data processing unit 115 performs, for the signal data collected from each terminal, data conversion in a complex number format, fault detection regarding the presence or absence of a system fault, and the like. Only when a system fault is detected, the signal from the other terminal is transmitted so that the master station can collect data. 151 is a converter that performs signal format conversion, for example, converting a unipolar format to a bipolar format signal
It is a U / B converter. Reference numeral 152 is a B / U converter that performs inverse conversion with 151. Reference numeral 153 is a signal terminal, which performs channel distribution on the data transmission path. Reference numeral 154 denotes a carrier device, which is an interface device for performing data transmission with each counter terminal. Reference numeral 511 is a computer that executes an accident aspect specifying calculation according to the present invention. The computer 511 executes the solution of the equation (5) according to the calculation flow of FIG. 512 is an output of the calculation result, or an auxiliary computer for monitoring the system. 513 is a CRT display for displaying a screen. A line printer 514 records data. Reference numeral 321 is a data transmission modem that connects the master station 400 to the control station, the power supply command station, or the like. The modem 321 can also be a small-scale device in units of one telephone line, such as when transmitting only the calculation result of the master station 400. 322
Is a carrier device, which is an interface of a data transmission system.

FIG. 6 shows a system configuration example corresponding to the terminal 200 of the R terminal shown in FIG. The same symbols as those shown in FIG. 1 or FIG. 5 indicate equivalents. 211
Is an A / D converter, which converts the voltage of the R terminal, the current signal, and the switching status signal of the circuit breaker CB into a digital amount and takes them in. It is the same as the A / D converter of FIG. 111. Is. 214
Is a memory and is used to store input signals, received signal data, transmission data, and the like. A data processing unit 215 performs addressing of transmission and reception data, editing of data, and monitoring of data. It may be the same as the data processing unit 115 in FIG. 251 is unipolar,
It is a bipolar signal converter and a U / B converter. 252 is a bipolar / unipolar signal converter, which is a B / U converter. 2
53 is a signal terminal. Reference numeral 254 is a transfer device. Data transmission is performed via the signal terminal 253, the carrier device 254, and the transmission path 310 in response to a data transmission request from the S terminal, with the S terminal serving as a master station.

FIG. 7 shows a terminal system such as a control station or a power supply command station for displaying the calculation result or using it as system control information. 600 is the output display shown in FIG. 1,
It is a storage device. Reference numeral 321 is a signal transmission / reception carrier device.
Since the transport device 321 does not always exist in the same building or the same room as the output display and storage device 600,
Blocks are indicated by a one-dot phantom line. 601 is a modem. Reference numeral 602 denotes an arithmetic unit, and a personal computer having a built-in memory capable of storing transmission / reception data may be used. Reference numeral 603 is a device for displaying and storing the calculation result.

The calculation unit 602 collects the results calculated by the master station 400 in Fig. 5 as data and edits the data so that the appearance of the accident can be easily seen from the outside, displays it on the screen, records it on a line printer, and prints it. Data is processed so that it can be recorded on a disk. Display, storage device 60
Reference numeral 3 is for displaying the screen, recording on a line printer, recording on a floppy disk, and the like.

FIG. 8 is an example of screen display contents by the display device shown in FIG. Date of accident occurrence, time, short circuit as an accident type, display of each ground fault phase, display of estimated result of accident cause,
The status of the change in accident point resistance over time, the position of the accident point, and the nearest steel tower as the accident point steel tower are shown with the tower number or symbol. In addition, the system will make it easier for the operator to understand the accident aspect identification result by displaying the accident point illumination in the system.

In addition, these display results can be taken as a hard copy, and data can be transmitted to other power stations and the like as needed.

〔The invention's effect〕

According to the present invention, the voltage and current detection data for each phase of the power system is used, and the fault point resistance for each fault phase of the power system is calculated, and the voltage equation used for the orientation calculation is used. Since an error term for reducing measurement error is set and solved, it is possible to further reduce the error in locating the accident point, thus reducing the labor for maintenance and inspection of the power system.

[Brief description of drawings]

FIG. 1 is an overall system configuration diagram of an accident aspect identification device according to the present invention, FIG. 2 is an explanatory diagram of a calculation method by a two-terminal two-phase parallel two-line transmission line, FIG. 3 is an impedance matrix of a line, and a fourth diagram. Fig. 5 is a calculation flow diagram. Fig. 5 is a system configuration diagram of the master station including data collection and central equipment. Fig. 6 is a configuration diagram of the terminal of the partner terminal. Fig. 7 is an output terminal for displaying and storing the calculation results. FIG. 8 is a system configuration diagram, which is an example of a functional diagram relating to display, storage, and recording of calculation results. Ten
0 …… Terminal, 500 …… Central unit, 600 …… Display of output,
Storage device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Abe 1-1-1, Kokubuncho, Hitachi City, Ibaraki Hitachi Kokubun Plant, Ltd. (72) Inventor Yu Takiguchi 1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture No. 1 Inside the Kokubun Plant of Hitachi, Ltd. (56) References JP-A-58-174863 (JP, A) Proceedings of the 63rd National Congress of the Institute of Electrical Engineers of Japan 1988 [10] 1239 "About Digital Locator for Transmission Line" (Pages 1617 to 1618)

Claims (2)

(57) [Claims] 1. A terminal installed in a specific section of a power system having a plurality of phases, time series data collecting means for collecting time series data of voltage and current signals for each phase detected by the terminal, and It consists of a central unit that creates a voltage equation for each phase from time-series data and has a position of a fault point of the power system and a computing unit that specifies a fault aspect from a fault point resistance of each fault phase of the power system. In the accident aspect specifying device of a power system, the calculating means sets an error term for reducing a measurement error of the time series data in the voltage equation for each phase,
An objective function that minimizes the sum of squares of the error terms is set, and the objective function is transformed by solving the voltage equation for each phase into a partial differential equation to reduce the measurement error of the time series data. Power system accident aspect identification device featuring 2. The power system accident aspect identification device according to claim 1, wherein the computing means detects the voltage and current signals while the power system is interrupted by the power system. An accident aspect specifying device for a power system, wherein the position of an accident point is calculated for each sampling, and the accident aspect is specified by an average value of the calculated accident point positions.