JPH0562308B2 - - Google Patents

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 by determining the time difference between the surge voltage that has traveled straight from the fault and reaching both ends of the power transmission line. There are two methods: one method detects the inductance component up to the fault point using the fundamental frequency components of the sending end voltage and current at the time of a fault occurrence, and uses 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. Furthermore, in either method, the line constant is assumed to be constant over the entire section, so if the line constant differs for each predetermined section, an error will occur in the location result.

[Purpose of the invention]

The present invention was made against this technical background, and its purpose is to have a simple configuration, to be able to accurately locate the fault point even in the case of intermittent faults, and to be able to adjust the line constant for each predetermined section. An object of the present invention is to provide a fault point locating method for a power transmission system that can accurately locate fault points even in different cases.

[Summary of the invention]

The present invention detects instantaneous values of voltage and current at predetermined gauge observation points of a power transmission system when a failure occurs,
This detected value is linearly converted by integrating it in a predetermined integration width, and the distance to the fault point is determined from this converted value, the instantaneous values of voltage and current, and the known line constant, and the distance to the fault point is To calculate the fault section, temporarily set a fault section that is thought to include the fault point, set one end of the section as the orientation starting point, and calculate the track constant from the orientation observation point to the orientation starting point and the temporarily set fault section. It is determined whether or not the oriented distance obtained by substituting the track constant is within the provisionally set fault area, and if it is within the fault area, the position of the oriented distance obtained at this time is determined as the fault point, and the fault area is determined. If it is outside the range, the provisional failure section is reset and the failure point is located.

〔Example〕

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

First, the principle of the present invention will be explained. Figure 1 is a diagram showing an equivalent circuit of an AC power transmission system.
Transmission voltage v(t) from is applied to fault point x via line resistance r and line inductance L, and current i(t) flows through fault point resistance R _f . Note that Z _p is the internal impedance of the AC source 1 and will be ignored below.

Since this equivalent circuit has an LR series circuit configuration, if a ground fault occurs at the fault point x via the fault point resistance R _f , the sending end voltage v(t) can be expressed by the following differential equation. can.

v(t)=(r+R _f )・i(t)+Ldi(t)/dt…(1) If R=r+R _f , then v(t)=R・i(t)+Ldi(t)/dt…( 2) Therefore, when formula (2) is linearly transformed for a finite time width [t-T, t], ∫ ^t _tT v(τ)e ^-s( 〓 ^-t+T) dτ=R∫ ^t _tT i (τ)e ^-s(
〓 ^-t+T) dτ＋L∫ ^t _tT di(τ)／dτe ^-s( 〓 ^-t+T) dτ…(3
) becomes.

The integral of the second term on the right-hand side is obtained by integrating by parts∫ ^t _tT di(τ)／dτe ^-s( 〓 ^-t+T) dτ＝[i(τ)e ^-s(
〓 ^-t+T) 〕 ^t _tT −∫ ^t _tT i(τ)(−s)e ^-s( 〓 ^-t+T) dτ＝i(t)e ^-st −i(t−T)＋S∫ ^t _tT i(τ)e ^-s( 〓 ^-t+T) dτ…(4) Therefore, by substituting equation (4) into equation (3), we get ∫ ^t _tT v(τ)e ^-s( 〓 ^-t+T) dτ＝R∫ ^t _tT i(τ)e ^-s(
〓 ^-t+T) dτ +L{S∫ ^t _tT i(τ)e ^-s( 〓 ^-t+T) dτ−i(t−T
)+i(t)e ^-sT }...(5).

Here, V(s, t)=∫ ^t _tT v(τ)e ^-s( 〓 ^-t+T) dτ …(6) I(s, t)=∫ ^t _tT i(τ)e ^-s( 〓 ^-t+T) dτ …(7) Then, equation (5) can be expressed as follows.

V(s, t)=RI(s, t)+L{SI(s, t)−i(
t-T) + i(t)e ^-sT }...(8) Therefore, from equations (6) to (8), if we fix t-T=t _p and let t→∞, then From equation 6), V(s)=∫ ^∞ _tp v(τ)e ^s( 〓 ^-to) dτ From equation (7), I(s)=∫ ^∞ _tp v(τ)e ^s( 〓 ^{-to )} dτ From equation (8), V(s)=RI(s)+L{SI(s)−i(t _p )}. 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 L is obtained by eliminating the R term including the fault point resistance R _f from equation (8), and the distance to the fault point is calculated by dividing this L by the inductance l 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. .

Specifically, if t=t ₁ , t ₂ , then V(s, t ₁ )=RI(s, t ₁ )+L{SI(s,
t ₁ )−i(t ₁ −T)+i(t ₁ )e ^−sT }…(9) V(s, t ₂ )=RI(s, t ₂ )+L{SI(s,
_t2 )-i( _t2 -T)+i( _t2 )e ^-sT }...(10) Two equations are obtained. Therefore, equation (9) x I
(s, t ₂ ) - Equation (10) x I (s, t ₁ ) If we eliminate the R term from these equations, the inductance L
is L=V(s, t ₁ )・I(s, t ₂ )−V(s, t ₂ )
・I(s, t ₁ )/{-i(t ₁ -T)+i(t ₁ )e ^-sT }I
(s, t ₂ )−{−i(t ₂ −T)+i(t ₂ )e ^−sT }I(s
, t ₁ )...(11).

On the other hand, in equation (8), t is fixed and the real number S is S
= S ₁ , S ₂ , V (s ₁ , t) = RI (s ₁ , t) + L{S ₁ T (s ₁
, t)-i(t-T)+i(t)e ^-s ₁ ^T }...(12) V(s ₂ , t)=RI(s ₂ , t)+L{S ₂ I(s ₂
, t)-i(t-T)+i(t)e ^-s ₂ ^T }...(13) Two equations are obtained.

Therefore, Equation (12) x I (s ₂ , t) - Equation (13) x I (s ₁
,
Eliminating the R term _from these equations as t), _the inductance L _becomes
t)・I(s ₁ , t)/{S ₁ I(s ₁ , t)−i(t−T)
+i(t)e ^-s ₁ ^T }・I(s ₂ , t) −{S ₂ I(s ₂ , t)-i(t-T)+i(t)
e ^-s2T }・I(s ₁ , t)...(14).

Therefore, by dividing the inductance L obtained by performing the calculations shown in equations (11) and (14) by the inductance per unit length l [H/m], up to the failure point x The distance D [m] can be found. In this case, the current i(t) handled in equation (11) is as shown in Figure 2, and similarly, the current i(t) in equation (14) is as shown in Figure 3. becomes.

By the way, in equations (11) and (14), V(s,
t) and I(s, t) can be easily calculated based on the instantaneous values of voltage and current as shown in equations (6) and (7). As an example, a method of calculating from voltage and current data sampled at regular intervals will be described below. As shown in Fig. 4, the voltage v(t) in one sampling period [tk, tk+ ₁ ]
When approximated by a straight line, it can be expressed as v(t)≒vk+(vk+ ₁ −vk/Δt)(t−tk) (15).

However, vk: sampling link value at time tk, vk+1: sampling value at time tk+ ₁ =tk+Δt, Δt: sampling interval.

Then, the integral value multiplied by e ^-sT in n consecutive sampling intervals [O, T] can be calculated as follows.

∫ ^T _O v(t)e ^sT dt≒ _N 〓 ^k=1 ∫ ^tk+1 _tk v(t)e ^-sT dt= _N 〓 〓 ^k=1 ∫ ^tk+1 _tk {vk+(vk+1−vk/△t )(t-tk)}e
^sT dt _N 〓 〓 ^k=1 {(vk/s+vk+1-vk/s ² △t)(e ^-stk −e ^-stk+
1 ) - (vk+1-vk/s)e ^-stk+1 }...(16) Therefore, by providing a calculation means that performs the above calculation, it is possible to calculate the distance D to the failure point x. can.

To summarize, the principle of the present invention is that when f(t) is the instantaneous value of voltage and current detected at the transmission end when a fault occurs, T is the integration width, S is an arbitrary real number, and _tp is the integration start time, F (s, t _p )= _tp+T 〓 ^to f(t)e ^-s(t-to) dt By the conversion formula shown as The distance D to the fault point x is calculated using the linearly converted values obtained by determining the integration start times or real numbers. Therefore, even if the AC voltage v(t) shown in FIG. 5a is intermittently grounded at the fault point x and the current i(t) is as shown in FIG. 5b, the integral width T By setting the current i(t) to approximately 1/4 period of the AC voltage v(t), it is possible to obtain a linearly converted value of the current i(t) as shown in Figure 5C and calculate the distance D to the fault point x. can.

FIG. 6 is a block diagram showing an embodiment of the failure point locating device based on the principle explained above, in which the detection unit 10 detects the sending end voltage v(t) and the current i(t),
11, a linear conversion unit 12 that performs the linear conversion calculations shown in equations (9) and (10) above, and a location calculation unit 13 that calculates the inductance L by performing the orientation calculations shown in equation 11. The sending end voltage v(t)
and current i(t) are detected by detection units 10 and 11, respectively, and further sampled at a predetermined period.
Then, the sample values v(t)' and i(t)' are converted into digital values V(t)' and I(t)', and then are used in the integration circuits 120 and 121 of the linear conversion section 12 with an integration width T. is integrated between. This integral value is calculated by the calculation circuit 122,1
23, and here the linear values V(s, _{t 1 )} , V(s, _{t 2 )} , I(s, t ₁ ), I(s,
t ₂ ).

On the other hand, the digitized current value I(t)' is input to the calculation circuit 130 of the orientation calculation section 13, where the difference between time t ₁ and (t ₁ -T) and between t ₂ and (t ₂ -T) is calculated. The value of I ₁ = {i (t ₁ ) e ^-sT − i (t ₁ − T)}, I ₂ = {
i
( _t2 )e ^-sT -i( _t2 -T)} are obtained.

Of these current differences I ₁ and I ₂ , I is input to the multiplier 131 , where it is multiplied by the linear conversion value I (s, t ₂ ) output from the arithmetic circuit 123 , and then added to the adder 12
3 is input. Further, the current difference I ₂ is input to the multiplier 132 , where it is multiplied by the linear conversion value I (s, t ₁ ) output from the arithmetic circuit 123 and then input to the adder 133 . As a result, the adder 13
3 outputs the value of the calculation result indicated by the denominator of equation (11).

On the other hand, the linear conversion values V(s, t ₁ ) and V(s, t ₂ ) of the voltage output from the arithmetic circuit 122 are obtained by the multiplier 13.
4 and 135, where they are multiplied by the linearly converted current values I(s, t ₂ ) and I(s, t ₁ ), respectively, and then input to an adder 136. As a result, the adder 136 outputs the value of the calculation result shown by the numerator of equation (11). After this, adder 13
The output of the adder 133 is input to the divider 137 as the dividend and the output of the adder 133 as the divisor. As a result, the inductance L at the time of occurrence of a failure as shown in equation (11) can be determined. The inductance L obtained in this way is the inductance l per unit length.
Divided by [H/m]. As a result, the distance to the failure point x is calculated.

By the way, the above description assumes that the line constants are uniform throughout the entire section of the power transmission system. However, in actual power transmission systems, the types of wires used differ between mountainous areas and urban areas, and line constants are rarely uniform.

In order to accurately locate the fault point even in such a case, the present invention temporarily sets a fault section that is thought to include the fault point when calculating the distance to the fault point, and uses one end of this section as the starting point for locating the fault point. It is determined whether or not the oriented distance obtained by substituting the line constant from the transmission end to the oriented starting point and the line constant of the tentatively set failure section is within the tentatively set fault section, and the fault section is determined as follows. If it is within, the position of the determined distance is determined as the failure point, and if it is outside the failure area, the temporarily set failure area is reset and the failure point is located.

That is, assuming that a ground fault has occurred in section f of sections a to f as shown in Fig. 7, one end of section f, Xo, is temporarily set as the orientation starting point, and equation (11) or The calculation shown in equation (14) is performed, and then it is determined whether the inductance L obtained at this time is larger or smaller than the inductance Lo from the power transmission end to the end point of the section e. In other words, the inductance Lo and distance Do to the end point of section e
Since the distance and line type of each section a to e are known, the inductance Lo during this period is compared with the inductance L up to the tentative orientation starting point Xo,
Determine its size. Then, in the case of L<Lo, it is assumed that the faulty section is located closer to the power transmission end side of section f. Also, if the distance of section f is Df and the inductance of unit length is lf, then L>Lo+
In the case of Df·lf, the fault section is assumed to be further away than the section f. However, Lo<L
In the case of <Lo+Df·lf, the failure point is assumed to be within the interval f.

Next, if it is assumed that the failure point does not exist within the section f, the orientation starting point Xo is set to another point and a similar determination is made. but,
In the case of Lo<L<Lo+Df・lf, the distance from the power transmission end to the fault point is calculated by calculating Dx=Do+L−Lo/lf (17).

Note that this calculation is performed using the inductance L component, but since the distance of each section and the inductance per unit length are known, the distance to the failure point may be calculated by converting L into a distance. .

In this case, the following methods are available for setting the orientation starting point Xo.

(1) The starting section is the section that includes the point oriented based on the average value of the track constants of the entire section.

(2) The section closest to the power source will be the departure section.

(3) The section farthest from the power source shall be the departure section.

(4) Sequentially refer to past orientation results.

Method (1) is convenient for locating a fault point with one orientation calculation, and method (4) is convenient for continuous orientation calculations.

On the other hand, if the fault point is near the boundary of the section, the above-described location calculation may be repeated, making it difficult to determine the fault point. In such cases, the failure point may be expressed within a certain range,
It may also be expressed as an average value of the results of a plurality of calculations.

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 alternators, the configuration is extremely simple and economical. The failure point can be located using 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, even if the track constants differ for each predetermined section, as long as the distance and track constants of each section are known, the distance from the gage point observation point can be calculated accurately no matter which section a failure occurs. It is possible to obtain extremely innovative effects in practical use.

[Brief explanation of the drawing]

Figure 1 is an equivalent circuit diagram of an AC power transmission system, Figures 2 to 5
Figure 6 is a diagram showing current and voltage to explain linear conversion processing, Figure 6 is a block diagram showing an embodiment of a fault point locating device to which the present invention is applied, and Figure 7 is a diagram showing a power transmission system with different line constants. FIG. 3 is an equivalent circuit diagram when locating a failure point. 1... AC source, 10, 11... detection unit, 12...
...Linear conversion section, 13... Orientation calculation section.

Claims (1)

[Claims] 1. Voltage and current are detected at predetermined orientation observation points of a power transmission system where line constants differ for each predetermined section, the detected voltage and current are sampled at a predetermined period, and the sampling value and unit length are In a power transmission system fault location method that determines the distance to a fault point based on a known line constant, a linear approximation value of voltage and current is obtained by integrating the sampled value over a predetermined time width,
When calculating the distance to the fault point using the linear approximation value and the line constant, a fault section presumed to be the fault point is temporarily established, one end of this section is set as the orientation starting point, and the orientation observation point is It is determined whether the orientation distance obtained by substituting the track constant from to the orientation starting point and the track constant of the provisionally set failure section is within the provisionally set failure area, and if it is within the failure area, then A fault point locating method for a power transmission system, characterized in that the position of the determined locating distance is determined as a fault point, and if it is outside the fault area, the provisional fault area is reset and the fault point is located. 2. Fault point locating in a power transmission system according to claim 1, wherein the locating starting point is a section including a point locating based on the average value of the line constant of the entire locating section. method. 3. Claim 1, wherein the orientation starting point is a starting section that is closest to a power source.
Fault point location method for power transmission system described in . 4. Claim 1, wherein the orientation starting point is a starting section that is farthest from a power source.
Fault point location method for power transmission system described in . 5. The fault point locating method for a power transmission system according to claim 1, wherein the locating starting point sequentially refers to past locating results.