JPH0560065B2 - - 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. One method is to locate based on the time difference, and the other is to detect the inductance component up to the fault point using the fundamental frequency components of the sending end voltage and current at the time of fault occurrence, and use this to locate the distance from the sending end to the fault point. be.

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 locate fault points with high accuracy even in the case of intermittent faults. It's about doing.

[Summary of the invention]

The present invention linearly converts the instantaneous values of voltage and current at the sending end at the time of occurrence of a fault by integrating them in a predetermined integral width, and uses this converted value, the instantaneous values of voltage and current, and known line constants to reach the fault point. It is designed to find the distance between.

〔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.
The transmission voltage v(t) from is applied to the fault point x via line resistance r and line inductance L,
A current i(t) flows through the fault point resistor Rf. In addition, Zo
is the internal impedance of the AC source 1.

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 Rf, the sending end voltage v(t) can be expressed by the following differential equation. .

v(t)=(r+Rf)・i(t)+Ldi(t)/dt...
…(1) If R=r+Rf, then v(t)=R・i(t)+Ldi(t)/dt...(2) Here, the second equation for the finite time width [t-T, t] After linear transformation, ∫ ^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, substituting equation (4) into equation (3), ∫ ^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{S′I(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→∞, From equation (6), V(s)=∫ ^∞ _tp v(τ)e ^-s( 〓 ^-to) d
τ 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 commutative equation (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 Rf from equation (8), and the distance to the fault point is calculated by dividing this L by the inductance 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( _t1 )e ^-sT }...(9) V(s, _t2 )=RI(s, _t2 )+L{SI(s, _t2 )-i(
t ₂
-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 )/{−i(t ₁ −T)+
i(t ₁ )e ^-sT }I(s, t ₂ )-V(s, t ₂ )・I(s,
t ₁ )/−{−i(t ₂ −T)+i(t ₂ )e ^−sT }I(s, t ₁
)...(11) becomes.

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 I (s ₁ , t) − i
(t-T)+i(t)e ^-s1T } ...(12) V( _s2 ,t)=RI( _s2 ,t)+L{ _S2I ( _s2 ,t)-i
(t-T)+i(t)e ^-s2T }...(13) Two equations are obtained.

Therefore, equation (12) x I (S ₂ , t) - equation (13) x I
Eliminating the R term from these equations as (s ₁ , t), the inductance L is: L=V(s ₁ ,t)・I(s ₂ ,t)−V(s ₂ ,t)
・I(s ₁ , t)/{S ₁ I(s ₁ , t)−i(t−T)+i
(t) e ^-s1T }・I(s ₂ , t)……(14) −{S ₂ I(s ₂ , t)−i(t−T)+i(t)
e ^-s2T }・I(s ₁ , t).

Therefore, by dividing the inductance L obtained by performing the calculations shown in equations (11) and (14) by the inductance per unit length [H/m], the distance up to the failure point x is calculated. The distance D [m] can be determined. 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
(t) becomes as shown in FIG.

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, when voltage v(t) is linearly approximated in one sampling period [tk, tk+1], v(t)≒Vk+(vk+1−vk/Δt) (t−tk) ……(15) It can be expressed as

however, vk: sampling value at tk, vk+1: tk+1=sampling value at tk+Δt, Δt: sampling interval It is.

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/Δk )(t-tk)}e ^-
st dt = _N 〓 〓 ^K=1 {(vk/s+vk+1-vk/s ² Δt)(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 present invention provides F( _s , t _p )=∫ ^to+T _tp f(t)e ^-s(t-to) dt By the conversion formula shown as The integration start time or real number is determined, and the distance D to the failure point x is calculated using this linear conversion value. Therefore, the AC voltage v shown in FIG.
(t) is intermittently grounded at the fault point x, and the current i(t)
Even if the current i(t) is as shown in Fig. 5b, by setting the integral width T to about 1/4 cycle of the AC voltage v(t), the current i(t) is as shown in Fig. 5c.
The distance D to the failure point x can be calculated by obtaining the linearly converted value of .

FIG. 6 is a block diagram showing an embodiment of the failure point locating device based on the principle explained above, and includes detection sections 10 and 11 for detecting the sending end voltage v(t) and current i(t), and A linear conversion section 12 that performs the linear conversion calculation shown in equations (9) and (10);
It is composed of a location calculation unit 13 that calculates the inductance L by performing the location calculation shown in the formula, and the power transmission end voltage v(t) and current i(t) are detected by the detection units 10 and 1.
1, and further sampled at a predetermined period. And the sample value v
(t)' and i(t)' are converted into digital values V(t)' and I(t)', and then integrated over an integration width T in integration circuits 120 and 121 of the linear conversion section 12. This integral value is led to arithmetic circuits ₁₂₂ and 123, where the linear value V( _s ,
t ₁ ), V (s, t ₂ ), I (s, t ₁ ), and 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 respectively 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 13
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 added to the adder 1
33. As a result, the adder 133
outputs the value of the operation 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 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 1
The output of 36 is input as a dividend, and the output of adder 133 is input as a divisor to a divider 137. 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 thus obtained is divided by the inductance per unit length [H/m]. As a result, the distance to the failure point x is calculated.

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. The configuration can locate the point of failure. 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 width, extremely innovative effects such as the ability to correctly locate the failure point even in the case of intermittent failures can be obtained.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. Detection means for detecting voltage and current at the power transmission end, and instantaneous values of the detected voltage and current as f(t),
Integration width is T, arbitrary real number is S, integration start time is t _p
Based on F(s,t _p )=∫ ^to+T _tp f(t)e ^-s(t-to) dt, the real number S and the integration width T are fixed, and the integration start time t _p is set to 2. a first calculation means for linearly converting the voltage and current in the integral width T at different times; A power transmission system failure point locating method for locating a distance from a power transmission end to a failure point, the method comprising: a second calculation means for calculating a distance to a failure point based on a line constant; 2. Detection means for detecting voltage and current at the power transmission end, and instantaneous values of the detected voltage and current as f(t),
Integration width is T, arbitrary real number is S, integration start time is t _p
Based on F(s,t _p )=∫ ^to+T _tp f(t)e ^-s(t-to) dt, fix the integration start time t _p and the integration width T, and set the real number S to 2. The first step is to linearly convert the voltage and current in the integral width T when they are set to two or more different values.
and a second calculation means that calculates the distance to the failure point from the calculation results of the calculation means of the electric power 1, the instantaneous values f(t) of voltage and current, and known line constants, A fault location method for power transmission systems that locates the distance from the edge to the fault point.