JPS59230175A - Spotting method of short-circuited point of three-phase high-voltage distribution line - Google Patents

Abstract

PURPOSE:To spot a short-circuit with high precision even in case of the short-circuiting of the whole line regardless whether in a balanced or an unbalanced state by deciding on a positive-phase voltage and a positive-phase current from three line voltages and line currents based upon measured values and arithmetic values, and further calculating a specific virtual phase voltage and calculating reactance from the result. CONSTITUTION:Two line voltages and line currents of three-phase high-voltage distribution lines R, S, and T are measured through transformers CT1-CT4 and current transformers PT1-PT4 and applied to a CPU through an A/D converter ADC to determine three line voltages and line currents. Then, the positive-phase voltage and positive-phase current are calculated by a symmetric coordinate method from those voltages and currents, and the reactance is calculated from the positive-phase current and the virtual phase voltage obtained by dividing the positive-phase voltage by three and delaying the phase by pi/6 (Rad). This reactance is divided by the reactance of the line per unit length to perform spotting from a power transmission side to the short-circuited point P with high precision even in case of the short-circuiting of the whole line regardless of whether in the balanced and unbalanced states.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for locating a short-circuit point in a three-phase high-voltage power distribution line when all three phases are short-circuited, regardless of whether it is a balanced or unbalanced short-circuit.

Generally, in a single-phase line, when a short-circuit accident occurs, the distance to the short-circuit point can be determined by measuring the reactance portion of the impedance viewed from the power transmission side to the short-circuit point. This is calculated from the power transmission side by assuming that the line length from the power transmission side to the short-circuit fault point is l (m), the impedance per unit length of one phase of the line is Zo=R-1-jwL1, and the short-circuit resistance at the fault point is Rg. The impedance Z when looking at the short circuit point is
Z −ZO・ l+Rg −R@l+Rg 10 jwL
Since it is expressed as IIl, if we measure the reactance jwL @l: which is not related to the size of Rg, then by determining the reactance per unit member (known quantity), the distance to the short circuit point m1ffl l is the size of Rg. This is because it is required regardless of the circumstances.

By the way, when locating the short-circuit point of a three-phase high-voltage distribution line, the above-mentioned single-phase short-circuit point locating method can be used in principle, but if two three-phase wires are in metal contact and this two wires are in contact with other wires, When an unbalanced short circuit occurs, such as a short circuit between two lines due to arc discharge, the single-phase short circuit point locating method described above has the disadvantage that the short circuit point cannot be accurately located. This is because in the case of an unbalanced short circuit in a three-phase high 1F distribution line, if you want to accurately locate it, there is a core that determines the neutral point potential of the short circuit point, but if there is a failure situation (unbalanced short circuit This is because it is impossible to find the positive (1 (g) neutral point voltage) unless you know the state of

On the other hand, there is currently a technology as a short-circuit point locating device for three-phase high-voltage distribution lines, which is shown in the Publication J (53-4:z3"J). Detect the wires of each phase at 3 and 3. However,
This method is applicable only when two phases of the foil are short-circuited or when there is a balanced short-circuit.

Kibatsu Q1 has this advantage, and when all lines of a three-phase high-voltage distribution line are short-circuited, it is possible to locate the short-circuit point with extremely high accuracy, regardless of whether it is a balanced or unbalanced short-circuit. It provides a location method.

Thus, the method of the present invention includes an instrument transformer that divides and extracts at least two line voltages on the power transmission side of a three-phase high-voltage distribution line, and a voltage transformer that divides and extracts at least two line currents.
3 line voltages and line currents are obtained directly or indirectly by calculation from these transformers and current transformers, and then from these three line voltages and line currents. Find the positive sequence voltage and positive sequence current using the symmetric coordinate method, and multiply the 1F411 voltage by 1/ and change the phase by π/
6 (rad) The virtual phase voltage is calculated with a delay, and the short circuit point is determined by calculating the actance i from this virtual phase voltage and current. is taken to be 'verbatim'.

According to the method of the present invention, it is possible to locate the short circuit point with high accuracy by squeezing regardless of the unbalanced short circuit. It is difficult to add h7.

Next, an embodiment of the method of the present invention will be explained based on the drawings. FIG. 1 shows an apparatus N for carrying out the method of the invention, R,
S, T are three-phase high voltage distribution lines, P is short circuit point, PTI.

PT2 is a potential transformer provided on the power transmission side of the distribution line, CT2 is a potential current transformer.

The transformers PTI and PT2 divide the line voltage of the three-phase high voltage distribution line and output the divided voltage. The current transformers CTI and CT2 divide the line current and output it. In the illustrated example, two pressure transformers and two current transformers are used, and the system is of a two-line type. The calculation for locating the short-circuit point P requires the total line voltage and the total line current, but the reason why only two line voltages and line currents are obtained is that the remaining line voltage and line current are calculated. This is because the current can be determined by vectorial calculation. However, it is of course possible to directly extract the entire line voltage and current by using three transformers and current transformers.

PT3. PT4. CT3. CT4 is Kamikoki P T 1
.

PS2. The line type 1f3 taken out by CTt and CT2 is a transformer and current transformer that further divides and divides the line current.

IF is the interface circuit Fk'r, A I-) C is this interface circuit yx, the divided voltage value of the line voltage applied through F is an A/D converter that converts the separated end of the line current into digital, and the CPU is , A/l) This is a computer that calculates the reactance of the line based on the digital signal from the converter. This computer's calculations!
' This is done according to the flowchart shown in Figure S2. That is, first, the line voltage VR8, vs'r from the A/D converter
, when signals corresponding to the line currents IR+IS are added, these data are organized and the remaining line-to-line type vector calculations are performed from these data.

Next, find the positive sequence voltage ■, and then the total line current IR
Similarly, find the positive sequence current ■ from +IS+IT. I=' (IB + alB + a21T)
-(2) Next, from the positive phase voltage V, the virtual phase voltage E
, find. This calculation is performed based on the following equation.

Here, El is referred to as a virtual phase voltage because the positive phase type 1 "V
Regard l as the line voltage and use that voltage to find the phase voltage.

The question is whether it is substituted into equation (3), which is the equation that FIG. 3 shows the vector relationship between El and V, and the vector relationship between the line voltage and line current described above.

The reactance X is calculated by the following equation, where θ is the relationship between El and 1. as shown in FIG. is the phase difference angle with The actance X calculated in this manner is stored as data, is digitally displayed by a display circuit, and is sent to the outside as a display signal. By dividing this displayed reactance by the reactance of the line per unit length, the distance l from the power transmission side to the short circuit point P can be determined, that is, the short circuit point can be located.

By the way, as mentioned above, there has not been sufficient theoretical proof that short-circuit point location can be performed with high precision by the Hokki calculation. However, what can be said is that even if an unbalanced short circuit occurs, by calculating the positive sequence voltage v1 and positive sequence current I from the line voltage and line current, the line voltage and line voltage equivalent to those in a balanced short circuit can be obtained. It is converted into electric current. Since the virtual phase voltage E1 is obtained from the positive phase voltage V1 and converted to the fourth voltage of one phase, the subsequent calculations for obtaining the actance are performed by a circuit equivalent to a single-phase circuit.

Therefore, it is considered that a simple calculation method can be used to locate the short circuit point with high accuracy regardless of whether it is an unbalanced short circuit or a balanced short circuit.

Next, various kinds of fruit ng' that support the high brightness of the method of the present invention.
f. Give an example.

<(1) Balanced short-circuit test> Since it is extremely difficult to test using the three-phase high-voltage distribution line itself, a simulated circuit as shown in Figure 4 was constructed. In this simulated circuit, a lumped resistance R1 and a lumped inductance L are used, which correspond to the resistance and inductance per unit length of the line.

Their values, line voltage, frequency '#:, etc. are shown in the table below. In addition, in the table below, the number in parentheses in the mark 1 (ζ instruction column) is the average value of the mark 14' IJ actance pushed into the R, S, and T phases, and the value of mark Zl- indicates this average value. So? (This is Sudda-bori.) The location value indicates the value determined by the method of the present invention. Therefore, the closer this location value is to the standard indication, the higher the accuracy.

Multiplier setting 5xll+-2Ω setting <(2) Unbalanced short circuit test l> The test circuit is the same as in Figure 4, but the test was performed when the line constant and short circuit resistance of the distribution line were set as shown in Figure 5. did. A short circuit resistance of 2Ω is a line voltage of 6fi (IOV,
Power supply % impedance 10% (1o ++ oKVA
), this corresponds to an arc drop of approximately 600V.

Multiplier setting 5X10-2 setting <(3) Unbalanced short circuit test 2> The test was conducted using the circuit shown in FIG. 6 instead of the circuit shown in FIG. 4XIJ5. γ=2 under the same conditions as in Figure 5
2 corresponds to 4 (1 hit) for an arc drop of about 120 QV.

Multiplier setting 5×10 Setting <(4) Simulation of short circuit point aJf> @7 In the circuit shown in figure, LR, EB+ ET+Za+ Zl
) + ZC + Zl + Z2 + Z3 are input into the computer, and the computer knee cv
RB, VST.

VTR+'R1'S+IT was calculated, and based on these values, calculations were performed according to the method of the present invention to obtain reactance X. Here, Za, Zt)lZo
is the impedance of the transformer on the power transmission side, ZI + Z2
, Z3 is a composite impedance of the impedance of each line and the short-circuit resistance Rg. In case of balanced short circuit, Zl""
Z2 "' Z3. Furthermore, as input data, ER
':3Fl 10 Vl 01Es=3f11 (lV
1240°, Hr=38111Vt120°, za=
Zb = zo = o -4-j4.4Ω was common to all simulations.

In addition, the reactance X column of the table lists the value obtained by calculating the method of the present invention using a computer.

(Continued on next page, blank space) Based on the results in the top 1 queen table, this is the official release! Method 14 was developed to be able to locate short-circuit points on three-phase high-voltage distribution lines with extremely high precision, with a location error within 0.5%.

[Brief explanation of the drawing]

FIG. 1 shows a first apparatus for carrying out the method of the invention;
2 is a flowchart of the computer shown in FIG. 1, FIG. 3 is a vector diagram showing the calculation process of the method of the present invention, and FIG. Fig. 6 is a diagram showing the simulated circuit used for t, @Fig. 6 is a diagram showing a circuit with different conditions for the distribution line in the circuit of Fig. 4,
The figure is a circuit diagram used for a simulation in which the short-circuit point is constant.

Claims (1)

[Claims] An instrument transformer that divides and takes out at least two line voltages on the transmission side of a three-phase high-voltage distribution line - 1 An instrument current transformer that divides and outputs at least two line currents, and these transformers , obtain the three line voltages and line currents directly or indirectly by calculation from the current transformer, and then calculate the positive sequence voltage and positive sequence current from these three line voltages and line currents using the symmetric coordinate method. Then, calculate the virtual phase voltage by multiplying the positive sequence voltage by 1Δ and delaying its phase by π/6 (rad), calculate the accurance between this virtual phase voltage and the positive sequence current, and detect the short circuit. A method for locating short-circuit points in a three-phase high-voltage distribution line, characterized in that point locating is performed.