JPH0769380B2 - Fault location method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is a fault for identifying a fault point according to a zero-phase current and a zero-phase voltage generated in a system when a one-line ground fault occurs in the system. Regarding point orientation method.

(Prior Art) Conventionally, the fault point in a transmission system with two parallel lines is detected by detecting a zero-phase current flowing through each line by a fault point evaluation device provided at the substation at the power source end of the system and based on these points. A fault point locating method for identifying a fault point is adopted.

FIG. 5 is a three-terminal system diagram for explaining the conventional orientation method. In the figure, 1 is a three-phase AC power source grounded by a neutral point grounding resistor 2, and the output voltage from this power source 1 is
After being boosted at the power source end substation A, power is transmitted to the non-power end substation C by the two-line power transmission line. In these two-line transmission lines, another transmission line is branched in the middle of the system, and this branch transmission line is connected to an intermediate substation B installed at a short distance from the two-line system. Further, on the load side of each line of the power source substation A, a fault point locator FL1 that takes in a zero-phase current from each line is provided.

Now, in FIG. 5, when a one-line ground fault occurs at the point G ₂ on the first line between the power source substation A and the intermediate substation B, as shown in the same figure, as shown in FIG. Zero-phase current ₀₂ from the power line end substation A to the intermediate substation B, and zero-phase current from the power line substation A to the fault point G _2
01 , and further, the zero-phase current ₀₂ flows from the intermediate substation B toward the fault point G ₂ . At this time, the orientation device FL1 measures the zero-phase currents ₀₁ and ₀₂ .

Then, the specification of the failure point can be calculated by the simple equivalent circuit of FIG. As shown in the figure, the unit length is 1 as the distance between the power source end substation A and the intermediate substation B, and the distance from the intermediate substation B to the fault point G ₂ (reference value) is l ₂ and the zero phase of the line Assuming that the impedance is ₀ per unit distance, there is a relation of ₀ (1-l ₂ ) ₀₁ = ₀ (1 + l ₂ ) ₀₂ between ₀₁ , ₀₂ , l ₂ and ₀ , so the orientation value l ₂ is Therefore, the fault point G ₂ can be located.

(Problems to be solved by the invention) However, as shown in FIG. 7, when a 1-line ground fault occurs at a point G ₁ between the intermediate substation B and the non-power-source substation C, the Between the end substation A and the intermediate substation B, zero-phase currents ₀₁ and ₀₂ flow from the power end substation A to the intermediate substation B on the fault line and the healthy line, respectively, and the intermediate substation B And the non-power-source substation C, a zero-phase current ₀₂ flows from the intermediate substation B to the non-power-end substation C in a sound line, and the fault line G from the intermediate substation B to the fault point G ₁ in toward the zero-phase current _01, the zero-phase current ₀₂ flows from the non-power end substation C to fault point G _1. At this time, the orienting device FL1 measures the zero-phase currents ₀₁ and ₀₂ at the power-source substation A as in the case of the ground fault between the power-source substation A and the intermediate substation B described above. Become.

However, since the zero-phase impedance of the system viewed from the locator FL1 is the same in the fault line and the healthy line because the system is closed in the intermediate substation B, ₀₁ = ₀₂ is always obtained.

Therefore, when the position of the fault point G ₁ is measured by the locator FL1 based on the zero-phase currents ₀₁ and ₀₂ , the distance between the non-power end substation C and the intermediate substation B is set to unit length 1,
If the distance from the intermediate substation B to the fault point G ₁ is l ₁ , Therefore, there is always a problem that the orientation result of almost 100% is obtained, and the orientation of the failure point cannot be determined by the orientation device FL1.

The present invention has been proposed in order to solve the above problems, and an object thereof is to provide an intermediate substation B between a power source end substation A and a non-power end substation C of a parallel two-line system. Provided is a fault point locating method capable of accurately locating a fault point even if a one-line ground fault occurs between the intermediate substation B and the non-power source substation C in the three-terminal system To do.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, a zero-phase current and a zero-phase voltage are taken from a grid in a non-power-source substation, and the zero-phase voltage and the power-supply phase voltage of the grid Calculate the zero-phase voltage generation rate that is the ratio of, the zero-phase voltage generation rate, the zero-phase current, and based on the maximum zero-phase current that is the zero-phase current at the time of complete ground fault pre-set, The one-line ground fault point is specified by calculating the ratio of the distance from the non-power source substation to the intermediate substation and the distance from the non-power source substation to the fault point.

(Operation) When a one-line ground fault occurs between the intermediate substation and the non-power-end substation of the grid, zero-phase current flows from the intermediate substation toward the fault point and a healthy line A zero-phase current flowing from the intermediate substation toward the non-power-source substation flows into the fault point through the non-power-end substation. In addition,
A zero-phase voltage is generated at the ground fault point, but this zero-phase voltage is approximately measured at the non-power source substation.

Here, the fault point locating device provided in the non-power source substation takes in the zero-phase current and the zero-phase voltage, and generates a zero-phase voltage which is a ratio of the zero-phase voltage and the power-source phase voltage in the orientation calculation section. The rate is calculated, and a predetermined calculation is performed from the zero-phase voltage generation rate, the zero-phase current, and the maximum zero-phase current which is a unique value in the system and which is a fault current at the time of complete ground fault that can be set in advance. Then, when the distance from the non-power-end substation to the intermediate substation is taken as the unit length, the distance from the non-power-end substation to the one-line ground fault point is located and the fault point is specified.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

First, FIG. 1 is a statistical diagram showing a three-terminal power transmission system. In the figure, 1 is a three-phase AC power supply, and this power supply 1 is grounded by a neutral point grounding resistance 2 whose value is Re. The power source 1 is connected to a power source end substation A, and two power transmission lines are drawn from the power source end substation A. A non-power-end substation C is provided at the end of the power transmission line. Between the power-source substation A and the non-power-end substation C, the corresponding phase of each line is short-circuited to form two lines. An intermediate substation B for branching the other line is set at a short distance from the two lines. Further, the non-power source substation C is provided with a fault point locating device FL2 for locating a fault point by detecting a zero-phase current and a zero-phase voltage.

Now, in the system shown in FIG. ₁ , it is assumed that a one-line ground fault occurs at a point G ₁ on the first line between the intermediate substation B and the non-power end substation C. Then, the fault current (zero-phase current) is from the fault point G ₁ to the ground, and from the ground to the neutral point ground resistance 2
Through to the neutral point of the power supply 1. At this time, the fault current is approximated by the current _NGR flowing through the neutral point grounding resistor 2.

Here, the zero-phase current flowing through the fault line (first line) between the power source end substation A and the intermediate substation B is ₀₂ , and the intermediate substation B is
The zero-phase current flowing from the intermediate substation B to the fault point G ₁ is the fault line between the intermediate substation B and the non-power end substation C, and the healthy line between the intermediate substation B and the non-power end substation C is ₀₃ . After flowing through
The zero-phase current flowing from the non-power source substation C toward the fault point G ₁ on the fault line is designated as ₀₄ . In addition, non-power end substation C
When the unit length is 1 and the distance between the intermediate substation B and the intermediate substation B is l ₁ , the distance from the non-power end substation C to the fault point (reference value) is ₁ , and the zero-phase impedance per unit distance of the system is ₀ .

At this time, the zero-phase current ₀₃ causes a voltage drop _{(1-l 1) 0 ·} 03 in the fault line between the intermediate substation B and fault point G _1, the zero-phase current _04, the sound channel intermediate Substation B
Since causes each voltage drop _{(1 + l 1) 0 ·} 04 to between the and the non-power end substation C and during fault line with non-power end substation C and fault point _{G 1, | 03 |: |} 04 | = (1 + l ₁ ) :( 1−l ₁ ).

That is, the relationship of ₀ (1-l ₁ ) ₀₃ = ₀ (1 + l ₁ ) ₀₄ (1) is established between ₀₃ , ₀₄ , and l ₁ .

On the other hand, as is clear from Fig. 1, the relationship of ₀₃ + ₀₄ = ₀₁ + ₀₂ = _NGR (2) holds.

By the way, in the high resistance grounding system, the neutral point grounding resistance 2
Since the value Re of is larger than the impedance of the transmission line, 1
Since the fault current _NGR at the time of the line ground fault can be regarded as a constant value irrespective of the fault point, the orientation value l ₁ is calculated by the equations (1) and (2) as follows. It is represented by.

Therefore, if the fault current _NGR of the system is calculated in advance and this calculated value is used as a set value, the reference value l ₁ can be obtained only by measuring the zero-phase current _04. The distance to the fault point G ₁ can be easily located.

Figure 2 shows this graphically.
The l ₁ as a horizontal axis, are expressed as the longitudinal axis ₀₄ of the magnitude I ₀₄ the taking respectively.

Now, in the 1-wire ground fault that occurs in the actual system, the fault point G ₁
May have a high impedance fault point resistance. This is because the transmission line is incompletely grounded with a high resistance material such as trees, and the steel tower also has a resistance of several tens of ohms.

This fault point resistance may be as large as the resistance ground fault Re of the neutral point grounding resistor 2, and the fault current in this case
_NGR , ₀₃ , and ₀₄ are smaller than in the case of complete ground fault.

FIG. 3 shows a zero-phase equivalent circuit in such an incomplete ground fault. Here, ₀ is the zero-phase voltage at the fault point, is the phase voltage, R _f is the fault point resistance, and the transmission line impedance is smaller than the neutral point ground resistance 2 (Re), so it is ignored. . With this equivalent circuit, the zero-phase voltage at fault point G _{1
0 is} a _{0 = Re · NGR = -R f} · NGR ... (4). Further, the zero-phase voltage ₀ generated at the fault point G ₁ can be regarded as substantially equal to the zero-phase voltage measured by the locator FL2 provided in the non-power source substation C. Therefore, when an incomplete ground fault occurs in the system, that is, when the fault point resistance R _f exists, the orientation value l ₁ is Becomes Here, the zero-phase voltage ₀ and the zero-phase current ₀₄ are measurable amounts, and Re is a known fixed amount, so the orientation distance l
₁ can be obtained by the equation (5).

Furthermore, when the numerator and denominator of equation (5) are divided by the power supply voltage, Becomes

Here, _TNGR is the maximum zero-phase current that _{grounds the} fault point G ₁ when the fault point resistance R _f is 0, and the ratio between the zero-phase voltage ₀ and the power supply phase voltage is η (zero-phase voltage occurrence rate). Then, formula (6)
Is Can be expressed as _TNGR is a constant value peculiar to a known pre- _settable system, and the zero-phase voltage generation rate η and the zero-phase current ₀₄ are measurable amounts. Therefore, the orientation distance l ₁ is the same as in the case of the equation (5). , (7) can be obtained.

FIG. 4 is a block diagram of the orientation device FL2 realized based on the equation (7). In the figure, 5 is the orientation calculation unit of the orientation device FL2 provided in the non-power source end substation C.
Is a measurement input section 6 having a current transformer 7 and an instrument transformer 8.
Therefore, the zero-phase current ₀₄ and the zero-phase voltage ₀ can be input. In addition, the orientation calculation unit 6 has a maximum zero-phase current in advance.
A settling unit 9 for _{setting TNGR} is connected.

In the orientation device FL2 shown in FIG. 4, as is already clear, the zero-phase current ₀₄ , the zero-phase voltage _0, and the maximum zero-phase current _TNGR , which is the fault current at the time of complete ground fault, are _taken into the orientation calculation unit 5, The zero-phase voltage generation rate η which is a ratio of the zero-phase voltage ₀ to the power-source phase voltage is calculated, and from the zero-phase voltage generation rate η and the zero-phase current ₀₄ and the maximum zero-phase current _TNGR , an expression ( 7) From substation C to intermediate substation B
The distance l ₁ from the non-power source substation C to the one-line ground fault point when the distance to is the unit length is determined and output, and the fault point G ₁ is specified.

(Effects of the Invention) As described in detail above, the present invention provides an orientation device at a non-power-source substation to calculate an orientation distance, and provides a zero-phase current of a healthy phase and a zero-phase voltage of a ground fault point. Taking equal zero-phase voltage into the orientation device, and calculating the zero-phase voltage generation rate that is the ratio of the zero-phase voltage and the power-source phase voltage, the zero-phase voltage generation rate, the zero-phase current and in the system Since it was decided to locate the fault point from the maximum zero-phase current, which is the fault current at the time of complete ground fault, which is a unique value, it was a parallel two-line system and between the power source substation and the non-power source substation. In a three-terminal transmission system having an intermediate substation for short-circuiting the corresponding phase of each line to branch another line from each line,
This has the effect of enabling highly accurate fault location.

[Brief description of drawings]

FIG. 1 is a three-terminal power transmission system diagram for explaining an embodiment of the present invention, FIG. 2 is a graph showing the orientation principle, FIG. 3 is a zero-phase equivalent circuit diagram at the time of incomplete ground fault, and FIG. FIG. 5 is a block diagram of a fault point locating device for carrying out the present invention, FIG. 5 is a power transmission system diagram for explaining a conventional technique, and FIGS. 6 and 7 are also zero-phase equivalent circuit diagrams. 1 ... Three-phase AC power supply, 2 ... Neutral point grounding resistance FL2 ... Fault point locator 5 ... Orientation calculation section, 6 ... Measurement input section 9 ... Setting section

Claims (1)

[Claims] 1. A parallel two-line system for short-circuiting a corresponding phase of each line between a power-source substation and a non-power-end substation to branch another line from each line. In a three-terminal power transmission system having an intermediate substation, the zero-phase current and the zero-phase voltage are taken from the system at the non-power-source substation, and the zero-phase voltage generation rate that is the ratio of the zero-phase voltage and the power-source phase voltage of the system. Based on this zero-phase voltage generation rate, the zero-phase current, and the maximum zero-phase current that is the zero-phase current at the time of a complete ground fault that has been set in advance, The fault characterized by calculating the ratio of the distance from the non-power-source substation to the intermediate substation and the distance from the non-power-source substation to the fault point by the formula Point orientation method.