JPS6122265A - System for locating trouble point of transmission system - Google Patents

Abstract

PURPOSE:To make it possible to locate even intermittent trouble with good accuracy, by simple constitution such that instantaneous values are calculated from the voltage and current at a transmission terminal by polynomial approximation and integrated to obtain a linear conversion value while the distance up to a trouble point is calculated by said linear conversion value, the instantaneous values and a line constant. CONSTITUTION:The voltage and current at a transmission terminal are sampled to be detected by detection parts 10, 11 and instantaneous values are calculated by a four-dimensional liner approximation circuit. These values are integrated for a time of an integration width T by the integration circuits 120, 121 of a linear conversion part 12 and converted to linear values by operation circuits 122, 123 to be inputted to multipliers 134, 135 and an adder 136. A current value I is inputted to the operation circuit 130 of a locating operation part 13 to calculate differences I1, I2 between times t1, t1-T and times t2, t2-T while these differences I1, I2 are multiplied into a lenear conversion value I by multipliers 131, 132 to be inputted to an adder 133. The outputs of the adders 136, 133 are inputted to a divider 137 to calculate inductance L when trouble is generated and, further, by using inductance per unit length, the distance up to a trouble point is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a fault point locating method for locating the distance from a power transmission end to a fault point in a power transmission system.

[Technical background]

When a fault such as a ground fault occurs in a power transmission line, the fault location method is used to locate the fault point. There is a method of locating by time difference, and a method of detecting the inductance component up to the fault point based on the fundamental frequency components of the sending end voltage and current at the time of fault occurrence, and using this to locate the distance from the sending end to the fault point.

However, the former method requires surge detectors at both ends of the power transmission line, making it expensive, and has the drawback that the surge voltage is distorted by the inductance component of the power transmission line, resulting in a large location error. Furthermore, the latter method has a drawback in that it is not possible to locate the fault point in principle for intermittent faults such as intermittent faults caused by high resistance.

[Purpose of the invention]

The present invention was made against this technical background, and its purpose is to provide a fault point locating method for power transmission systems that has a simple configuration and can accurately locate fault points even in the case of intermittent faults. It is about providing.

[Summary of the invention]

This F181 samples the voltage and current at the sending end when a fault occurs, approximates the instantaneous values of the voltage and current using the sampled values, performs linear conversion by integrating the instantaneous values in a predetermined integral width, and performs linear conversion. Conversion value and voltage,
The distance to the fault point is determined from the instantaneous value of the current and the known line constant, and the instantaneous values of the voltage and current are approximated by polynomials to further reduce errors in the linear approximation. .

〔Example〕

Hereinafter, the present invention will be explained in detail based on examples.

First, the principle of the present invention will be explained. FIG. 1 is a diagram showing an equivalent circuit of an AC power transmission system. Transmission voltage v (t) from AC source 1 is applied to fault point X via line resistance r and line inductance L, and current i (t) flows to the fault A resistor Rf. Note that zo is the internal impedance of the AC source 1 and will be ignored below.

This equivalent circuit has an LR series circuit configuration.If a ground fault occurs at the fault point (2) for a finite time span (t-T, t)
When the equation is linearly transformed, it becomes.

Since the integral of the second term on the right-hand side is = i (t)e -'' -1(t-T) by partial integration, substituting it into the equation (4) and the equation (3) yields.

Jinkode, Then, equation (5) can be expressed as follows.

V(s, t) E"' RI (B+ t)+L(S
I (s, tl -i (t-T) publication (t)e)...
...(8) Therefore, from equations (6) 2 to (8), t
If we fix -'l'=t0 and t-+U, then from equation (6), V (a) -f″v(τ)e131
−to)dτ1゜th (from equation 9, I(8)=/″v(T)e −@(T
-*Q) d rFrom equation (8), V(s)=R
I(a)+L(SI(a)-1(to)). This means the Laplace transform of equation (2).

The present invention utilizes the transformation formula (8) obtained by taking a finite integral width T, rather than the Laplace transform whose integral width is infinite.

That is, the inductance Le is obtained by eliminating the R term including the fault point resistance Rf'fr from equation (8), and the distance to the fault point is calculated by dividing this L by the inductance t of unit length.

In this case, there are two ways to use equation (8). One is to find the inductance L from two simultaneous equations obtained by fixing the real number S and taking two times t, and the other is a similar method using two real numbers S while fixing the time t. be.

Specifically, if 1Ct=t, t, then the following two equations are obtained: (10). Therefore, equation (9)×I(
a, t, ) - (10) Equation XI (a, t, ) If the R term is eliminated from these equations, the inductance L becomes...

On the other hand, in equation (8), t is fixed and the real number StS=
S, , S, then V(8I, t)-RI (8+, t)+L (S
t I (BI, j) - 1 (t - T) + 1 (t) e ~"
T) ”' (12) V(a,,t)=RI(a,,t
)+-L(S, I(s,,t)-i(t-T)+1(t
)e−”T) ”・(13) Two equations are obtained.

Therefore, if the R term is eliminated from these equations as Equation (12) XI (a,, t) - Equation (13) xI (s+-t), the inductance becomes.

Therefore, by dividing the inductance L obtained by performing the calculations shown in equations (11) and (14) by the inductance per unit length (A I: H/m), the distance up to the failure point distance DCm) can be found. In this case, the current 1(t
) is as shown in FIG. 2, and similarly, the current i (t) in equation (w) is as shown in FIG.

By the way, in equation (n) and equation (14), V(
'*t) BI (a, t) is a voltage sampled at regular intervals.

It is obtained by linear approximation of the current sample value.

That is, as shown in FIG. 4, the voltage V (t) in one sampling period (hc, tk+x:
By approximating all straight lines, vk+I Vk v(t) * vk+ (, t) (t tk)
It can be expressed as ``'' (15).

However, the sampling value at the time of Vk i tk, Vk+1
; tk+1"tk+△ is the O-F link value at the time,
Δt: sampling interval.

However, this blood relation approximation has a problem in that the approximation error increases when the previous sample value is compared, and the error in locating the failure point also increases.

Therefore, in the present invention, voltage v (t) e current i (t)
is calculated by approximating it using a polynomial.

That is, voltage v (t), current 1(t) t-function f
Then, the function f is calculated by an m-th degree polynomial regarding t, as shown in the following equation (16).

Here, k is the sample position (0) as shown in Figure 5.
(c) Fully expressed, ak...& is fk-1+f
It can be determined from m+1 function values (values of f) including k.

For example, when m = = 4, if we take the origin of time as shown in Figure 6, we get 'ke'k...
Kl( can be found.

At this time, by substituting the value of equation (16) into , an approximate value of the instantaneous value of the voltage at any time can be obtained.

The same applies to current. In addition, maki m = 2, m
The same holds true even when c:3.

Therefore, the distance to the failure point X can be calculated by providing a calculation means that performs the calculations described above. Furthermore, even if the AC voltage v(t) shown in Figure 7(a) is intermittently grounded at the fault point X and the current l(r) is as shown in Figure 7(b), the integral Width Tt - AC voltage v
By setting the period to about 1/4 of (t), the distance to the failure point X can be calculated by obtaining a linearly converted value of the current i (tJ) as shown in FIG. 7(C).

FIG. 8 is a proof diagram showing an embodiment of the failure point locating device based on the principle explained above, in which the sending end voltage v (t)
and a detection unit 10°11 that detects current i (t) e, a linear conversion unit 12 that performs fc linear conversion calculation as shown in equations (9) and (10), and The transmission end voltage v (tJ and current i (t) are each detected by a detection unit 10.11, and further sampled at a predetermined period. .

Then, the sample values v(t)' and 1(j)' are converted into digital values V(t)' and I(t)', and then are converted into integral widths T by the integrating circuits 120 and 121 of the linear converter 12.
is integrated over . The integral value of Jin is calculated by the calculation circuit 122.123.
The linear value V(
a.

i+), V(s, tt), I(a, tt)s
Ha, tt).

On the other hand, the digitized current value Ht)' is input to the calculation circuit 160 of the orientation calculation section 16, where the time t and (
tt-'r) and t, and it,-'r) value 11 = (1(t,)e-" 1(tt T) )
−I, = (i(t,)e−1(tt−′rt)) are obtained.

This current difference Il, 1. Of these, ■ is input to the multiplier 1311C, where it is multiplied by the linear conversion value I(a, tl) output from the arithmetic circuit 123, and then input to the adder 136. In addition, the current difference ■ is input to the multiplier 162, where the linear conversion value x(stt
t) and then input to the adder 166. As a result, the adder 163 outputs the value of the calculation result indicated by the denominator of equation (11). 1 On the other hand, the linear conversion value v(L ”r ) e V(as tt) of the voltage output from the arithmetic circuit 122 is calculated by the multiplier 13
4 and 165, where the linear conversion value of the current I
(a, tt)*I(s, tt) and then input to the adder 166. As a result, the adder 166 outputs the value of the calculation result indicated by the numerator of equation (n). Thereafter, the output of the adder 166 is input as the dividend, and the output of the adder 163 is input as the divisor to the divider 137. As a result, the inductance L at the time of the next failure occurrence is determined by equation (U). The inductance L obtained in this way is divided by the inductance per unit length t (H/m ) K. As a result, the distance to the failure point X is calculated.

FIG. 9 is a block diagram showing an embodiment of a fourth-order linear approximation circuit that performs the calculation shown in equation (18), and is
A memory 15 is provided for storing sample values fo-fN of voltage f (t) (or current) at intervals of Δ at tNVc, time t, and sample values '-1'-2m 'N+1 before and after tN, Further, N fourth-order linear approximation circuits 20-1 to 20-N are provided corresponding to the N sample values f and -fN, respectively, and the instantaneous voltage value fs(t) at time t0 is the sample value '1'. m '6 m
' -ILf-s ' is input to the e circuit 20-1, and is determined by executing the calculation shown in equation (16) here. Similarly, the instantaneous value of the voltage at time tN is determined by the (16th) sample value in circuits 20-2 to 20-N.
) and is obtained by K by performing the following calculation. The instantaneous voltage values ft (t) to fN(t) at times 1o-1N thus obtained are input to the adder 60 and integrated. As a result, the instantaneous value of the voltage v (t) at an arbitrary time can be obtained as shown in equation (18).

Note that the configuration can be further simplified by performing such calculations using a microcomputer or the like.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is only necessary to place voltage and current detectors only at the power transmission end, and by using existing transformers and current transformers, it is extremely simple and economical. Fault points can be located by configuration. Furthermore, since linear conversion processing is performed using integration, the fault point can be located with high accuracy even if harmonic components are included in the voltage or current. Furthermore, by appropriately setting the integration time span, the fault point can be correctly located even in the case of intermittent faults. In particular, since polynomials are used to perform linear approximation of voltage and current, it is possible to suppress orientation errors due to linear approximation errors, and it has extremely revolutionary effects such as dramatically improving orientation accuracy. can get.

[Brief explanation of the drawing]

Figure 1 is an equivalent circuit diagram of an AC power transmission system, Figures 2 to 7 are diagrams showing current and voltage to explain linear conversion processing, and Figure 8 is an implementation of a failure point locating system to which the present invention is applied. A block diagram showing an example, FIG. 9 shows voltage. FIG. 2 is a block diagram showing an example of a circuit that performs polynomial approximation of current. 1... AC source, 10.11... Detection unit, 12...
Linear conversion unit, 16... Orientation calculation unit, 15... ME7, 20-1 to 20-N... Fourth-order linear approximation circuit. Ward ~ 2＼ Yamakushin 1 亼

Claims (1)

[Claims] A detection means for detecting voltage and current at the transmission end, sampling the detected voltage and current at a predetermined period, and integrating the sampled values over a predetermined time width to obtain linear approximations of the voltage and current, and calculating the linear approximation of the voltage and current. A fault point locating method for a power transmission system, comprising calculation means for determining the distance to a fault point using an approximate value and a known line constant per unit length, wherein the instantaneous values of voltage and current are calculated using polynomials based on the sample values. A fault point locating method for a power transmission system, characterized in that a calculation means for calculating an approximation is provided, and the linear approximation value is obtained by integrating instantaneous values of voltage and current calculated by the calculation means.