JPH0564348A - Ground fault phase judging equipment - Google Patents

Abstract

PURPOSE:To provide a ground fault phase judging equipment having high reliability by judging the ground fault phase through pursuing the phase closest to the phase advance of 90 deg. relative to zero phase voltage during ground fault. CONSTITUTION:Ground fault phase voltages Va, Vb and Vc are made the same in phase as zero phase voltage Vo by the phase-shifting processing. And the phase difference between the zero phase voltage Vo and three-phase voltages Va, Vb and Vc or the scalar product is arithmetically processed. And the phase having the least phase difference or the phase practically having the maximum scalar product, and the phase having the lowest level among the three-phase voltages Va, Vb and Vc are selectively judged as the ground fault phase depending on the level of zero phase voltage Vo. By doing this, the arithmetic processing can be simplified, the ground fault phase can be accurately judged even though the phase of zero phase voltage changes due to ground fault resistance during ground fault, and the judgment with high reliability can be made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault phase determining apparatus for determining a ground fault phase of a transmission / distribution line.

[0002]

2. Description of the Related Art As is well known, when a one-line ground fault occurs in an ungrounded total distribution line, the vector of the zero-phase voltage Vo draws a semicircle as shown in FIG. Change. Here, FIG. 7 shows an example of characteristics in the case of determining the ground fault phase. In order to realize this characteristic, conventionally, the phase difference between the reference phase voltage and the zero-phase voltage Vo is calculated, and the ground fault phase is determined by the value of the phase difference.
There is a problem that arithmetic processing is complicated and takes time. Further, in terms of characteristics, since the boundary of the detection range is in contact with both ends of the phase change region of the zero-phase voltage Vo, there is also a disadvantage that a malfunction easily occurs due to an error in the vicinity.

[0003]

As described above, the conventional ground fault phase determination means have problems that the arithmetic processing is complicated and time-consuming, and that the reliability is low.

Therefore, the present invention has been made in consideration of the above circumstances, and the arithmetic processing is simple, and even if the phase of the zero-phase voltage changes due to the ground fault resistance at the time of a ground fault, the ground fault phase is accurately measured. It is an object of the present invention to provide an extremely favorable ground fault phase determination device with high reliability capable of determining the.

[0005]

A ground fault phase determining apparatus according to the present invention is configured such that a zero-phase voltage and its phase depend on a value of a ground fault resistance at the time of a single ground fault of a transmission / distribution line of an ungrounded system or a reactor grounded system. Intended for use in changing systems. Then, phase shifting means for performing phase shifting processing so that the ground-phase phase voltage and the zero-phase voltage are in phase with respect to the zero-phase voltage and the three-phase voltage, and the phase shifting processing by this phase shifting means. The calculation means for calculating the values corresponding to the phase difference between the zero-phase voltage and the phase voltage of the three phases are compared with the calculation results of this calculation means, and the phase having the smallest phase difference with the zero-phase voltage is selected. Comparing means for determining the ground fault phase, determining means for comparing the phase voltages of the three phases to determine the phase with the lowest level as the ground fault phase, and comparing means and determining means according to the level of the zero phase voltage. A selection means for selecting one of the determination results is provided.

Further, the ground fault phase determining apparatus according to the present invention is
In the above object, a phase shift means for performing a phase shift process for the zero-phase voltage and the three-phase phase voltage so that the ground-phase phase voltage and the zero-phase voltage have the same phase, and the phase shift means Computation means for computing the scalar product of the phase-shifted zero-phase voltage and the phase voltage of the three phases respectively, and the computation results of this computation means are compared, and the phase having the substantially maximum value is the ground fault phase. One of the comparing means and the determining means, which compares the phase voltages of the three phases and determines the lowest phase as the ground fault phase, and the comparing means and the determining means according to the level of the zero phase voltage. A selection means for selecting the determination result is provided.

[0007]

According to the above configuration, the phase difference between the zero-phase voltage and the three-phase voltage, which are phase-shifted so that the ground-phase phase voltage and the zero-phase voltage have the same phase, or The scalar product is calculated, and the phase with the smallest phase difference or the phase with the substantially maximum scalar product and the phase with the lowest level among the three phase voltages are determined according to the level of the zero-phase voltage. Since it is selectively judged as the ground fault phase, the calculation process can be simplified and the ground fault phase can be accurately judged even if the phase of the zero-phase voltage changes due to the ground fault resistance during ground fault. Therefore, it is possible to make a highly reliable determination.

[0008]

First, FIG. 5 shows a vector locus of the zero-phase voltage Vo and a vector of the phase voltages Va, Vb, and Vc of the three phases A, B, and C at the time of the A-phase ground fault of the ungrounded system. However, as is clear from this figure, the phase relationship between the zero-phase voltage Vo and the grounded A-phase voltage Va is always A-phase voltage Va.
Becomes 90 ° with respect to the zero-phase voltage Vo. Also,
This relationship is the B and C phase voltage V at the time of the B and C phase ground fault.
The phase relationship between b and Vc and the zero-phase voltage Vo is similarly established. Therefore, in this invention, the zero-phase voltage V
The basic principle is to determine the ground fault phase by searching for the phase closest to the phase advance of 90 ° with respect to o.

An embodiment of the present invention based on the above principle will be described below in detail with reference to the drawings.
In FIG. 1, reference numerals 11, 12, 13, and 14 denote input terminals, and the phase voltages Va, Vb, and Vc of the A, B, and C phases, respectively.
And the zero-phase voltage Vo is applied. Since the zero-phase voltage Vo in this case is the one sent from the GPT tertiary winding, the zero-phase voltage V shown in FIGS. 5 and 6 is obtained.
The phase is 180 ° out of phase with that of o.

The phase voltages Va, Vb, Vc and the zero-phase voltage Vo applied to these input terminals 11 to 14 are respectively
It is insulated and stepped down by the auxiliary PTs 15 to 18, noise components are removed in the FLT (filter) circuits 19 to 22, and sampled / held at every 30 ° of the input frequency in the S / H (sample / hold) circuits 23 to 26. After that, the analog multiplexer 27 selectively guides it to an A / D (analog / digital) conversion circuit 28 to convert it into digital data VaD, VbD, VcD, VoD.
The input frequency of the A / D conversion circuit 28 is 50H.
In the case of z, A / D conversion of each input is performed at a cycle of 1.67 ms (600 Hz).

Here, digital data VaD, Vb obtained by A / D converting the phase voltages Va, Vb, Vc and the zero-phase voltage Vo output from the A / D conversion circuit 28 every 30 °.
Taking digital data VaD as an example, D, VcD, and VoD are Va1, Va2, and Va as shown in FIG.
It is a vector quantity in the data group of 3, ... Then, these digital data VaD, VbD, VcD, VoD are
After being respectively latched by the latch circuits 29 to 32, the digital data VaD is supplied to the A-phase phase arithmetic circuit 33 and the A-phase effective value arithmetic circuit 34, and the digital data VbD is B.
The phase / phase arithmetic circuit 35 and the B-phase effective value arithmetic circuit 36 are supplied, the digital data VcD is supplied to the C-phase phase arithmetic circuit 37 and the C-phase effective value arithmetic circuit 38, and the digital data VoD is supplied to the delay circuit 39 and zero. It is supplied to the phase voltage effective value calculation circuit 40.

The delay circuit 39 uses the digital data Vo.
The digital data VoD ′ obtained by delaying D by 90 ° is
It outputs to the B and C phase operation circuits 33, 35 and 37, respectively. As a result, for example, the zero-phase voltage digital data VoD ′ at the time of the A-phase ground fault and the A-phase voltage digital data VaD that is the ground fault phase have the same phase as shown in FIG. It is needless to say that the zero-phase voltage digital data VoD 'and the ground-phase B, C-phase voltage digital data VbD, VcD have the same phase even when the B, C-phase ground fault occurs. Here, the A, B, and C phase operation circuits 33 and 3
Reference numerals 5 and 37 perform the calculations shown in the following equations (1), (2), and (3), respectively, and output the calculation results to the comparison circuit 41.

| VaD |. | VoD '| .cosθa / | VaD | = | VoD' | .cosθa (1) | VbD |. | VoD '| .cosθb / | VbD | = | VoD' | .cosθb ...... (2) | VcD | ・ | VoD '| ・ cosθc / | VcD | = | VoD' | ・ cosθc ...... (3)

However, θa is the zero-phase voltage digital data V
oD ′ is the phase angle between the A-phase voltage digital data VaD, θb is the phase angle between the zero-phase voltage digital data VoD ′ and the B-phase voltage digital data VbD, and θc is the zero-phase voltage digital data VoD ′ and C. Phase voltage digital data V
It is the phase angle with cD. Here, the calculation on the left side of the above equations (1) to (3) is performed by the phase voltage digital data VaD,
The respective scalar products of VbD, VcD and the zero-phase voltage digital data VoD ′ are converted into respective phase voltage digital data Va.
It is divided by D, VbD, and VcD. Since this is because A / D conversion is performed every 30 °, the value 90 ° before can be easily taken out. This is because the scalar product shown in equation (4) can be easily calculated.

| VaD | · | VoD ′ | · cos θa = Va · sin ωt · Vo · sin (ωt + θa) + Va · sin (ωt + 90 °) · Vo · sin (ωt + θa + 90 °) (4)

Comparing the calculated values of the equations (1) to (3), the absolute value | VoD '| of the zero-phase voltage digital data VoD' is common to the three equations, and therefore the ground fault phase is Of the three phase angles θa, θb, and θc, this is the phase closest to 0 °, that is, the phase having the maximum calculated value. For this reason, the comparison circuit 41 uses the calculated values of the above formulas (1) to (3), that is, the A, B, and C phase calculation circuits 33 and 3.
The phase having the maximum value among the respective calculation outputs of 5 and 37 is output as the ground fault phase. FIG. 4 shows that the ground fault phase can be accurately determined with respect to the phase margin of the zero phase voltage Vo when the ground fault phase is thus determined, that is, the theoretical phase of the zero phase voltage Vo. The phase range of the phase voltage Vo is shown.

The characteristic shown in FIG. 4 is 1/2 of the phase voltage phase angle between the ground fault phase and the lead and lag phases.
Since there is a minimum of 30 °, it is sufficient to consider that the deviation of the actual phase of the zero-phase voltage Vo from the theoretical value is about 10 ° even if it is large. However, the above (1) to (3)
In the calculation by the formula, the zero phase voltage Vo and each phase voltage V
The scalar product of a, Vb, and Vc is the phase voltage Va,
Since it is divided by Vb and Vc, an accurate ground fault phase determination cannot be performed due to an error in the range where the phase voltage near the complete ground fault becomes extremely small.

Countermeasures in this case will be described below.
When the zero-phase voltage Vo exceeds 50% of the value at the time of a complete ground fault, the phase voltages Va, Vb, Vc of the ground fault phase become the minimum, so that the A, B, C phase effective value calculation circuit 34, 36,3
At 8, the effective values of the phase voltages Va, Vb, and Vc of the A, B, and C phases are calculated, and the phase whose effective value is minimized by the comparison circuit 42 is output as the ground fault phase.

On the other hand, the digital data Vo of the zero-phase voltage Vo
The effective value of D is calculated in the zero-phase voltage effective value calculation circuit 40, and is supplied to the positive input terminal + of the comparison circuit 43. The comparison circuit 43 is supplied with the reference value 44 at its negative input terminal −, outputs a logic “1” when the value at the positive input terminal + becomes larger than the reference value 44, and otherwise outputs a logic “0”. Is output.

Here, the reference value 44 is determined based on the phase of the zero phase voltage Vo and the phase voltages Va, Vb and Vc, or the value of the phase voltages Va, Vb and Vc. Is for determining which value of the zero-phase voltage Vo should be switched, and it is desirable to set the values so that the errors due to the respective means are approximately the same. It becomes about 80 to 95% of the voltage Vo.

The output of the comparison circuit 43 is supplied to the gate circuits 45 to 50. When the output is a logic "1", that is, when the zero-phase voltage Vo is larger than the reference value 44, the gate is output. The gates of the circuits 45 to 47 are opened, and the ground fault phase determination output of the comparison circuit 42 that determines the phase in which the phase voltages Va, Vb, Vc are the minimum is the A, B, C phase ground fault determination. It is output to the output terminals 51 to 53. Further, when the output of the comparison circuit 43 is a logic “0”, that is, when the zero-phase voltage Vo is a value smaller than the reference value 44, the gate circuits 48 to 48.
The gate of 50 is opened, and the zero-phase voltage digital data VoD
The ground fault phase determination output of the comparison circuit 41 that determines the phase of the phase voltages Va, Vb, Vc of the phase closest to ‘A’ is A,
It is output to the B and C phase ground fault determination output terminals 51 to 53. As described above, accurate ground fault phase determination can be performed over the entire range of the ground fault voltage.

Here, the zero phase voltage Vo and the ground fault phase voltage V
As a means for making a, Vb, and Vc in phase,
There are means for delaying the phase voltages Va, Vb, Vc by 270 ° and means for delaying both the zero-phase voltage Vo and the phase voltages Va, Vb, Vc.

Further, as another means for determining the ground fault phase, the A, B and C phase operation circuits 33, 35 and 37 are respectively represented by the following equations (5), (6) and (7). It is also possible to perform calculation.

| VaD | · | VoD ′ | · cos θa …… (5) | VbD | · | VoD ′ | · cos θb …… (6) | VcD | · | VoD ′ | · cos θc …… (7)

The above equations (5) to (7) are expressed by the above (1) to
The left side of the equation (3) is the phase voltage digital data VaD, Vb.
It is a value when it is not divided by D and VcD, that is, zero phase voltage digital data VoD ′ and each phase voltage digital data VaD,
It is a scalar product of VbD and VcD. According to such calculation, the zero-phase voltage Vo is 3 ^{1/2 of} that at the time of a complete ground fault. Since the ground fault phase shows the maximum value at / 2 or less, by setting the reference value 44 to about 70% of that in the case of a complete ground fault, accurate ground fault phase determination can be performed over the entire range of the zero phase voltage Vo. it can.

Further, in the power transmission and distribution system with the reactance grounded, the relationship between the zero-phase voltage and the phase voltage at the time of the one-line ground fault is shown by the example of the A-phase ground fault as shown in FIG. Regarding the phase relationship with the ground fault phase voltage Va, the A phase voltage Va is always delayed by 90 ° with respect to the zero phase voltage Vo. From this, even in the case of reactance grounding, if the zero-phase voltage Vo and the ground fault phase-phase voltage are phase-shifted so as to have the same phase, the same effect can be obtained using the same means as the above-mentioned embodiment. .. The present invention is not limited to the above embodiment,
In addition, various modifications can be made without departing from the scope of the invention.

[0027]

As described in detail above, according to the present invention,
A highly reliable ground fault phase determination device that is simple in calculation processing and that can accurately determine the ground fault phase even if the phase of the zero-phase voltage changes due to the ground fault resistance during a ground fault. Can be provided.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of a ground fault phase determination apparatus according to the present invention.

FIG. 2 is a diagram showing details of phase voltage digital data VaD of the same embodiment.

FIG. 3 is a diagram shown for explaining that the ground fault phase voltage and the zero-phase voltage digital data VoD ′ in the embodiment have the same phase.

FIG. 4 is a diagram for explaining the phase margin of the zero-phase voltage Vo in the same embodiment.

FIG. 5 is a diagram for explaining the basic principle of the present invention.

FIG. 6 is a diagram showing a change in zero-phase voltage Vo due to a ground point resistance.

FIG. 7 is a diagram showing a conventional ground fault phase determination characteristic.

FIG. 8 is a diagram shown for explaining a phase relationship between a ground fault phase voltage and a zero phase voltage in a reactor grounding system.

[Explanation of symbols]

11-14 ... Input terminal, 15-18 ... Auxiliary PT, 19-
22 ... FLT circuit, 23-26 ... S / H circuit, 27 ... Analog multiplexer, 28 ... A / D conversion circuit, 29 ...
32 ... Latch circuit, 33 ... A phase calculation circuit, 34 ... A
Phase effective value calculation circuit, 35 ... B Phase phase calculation circuit, 36 ... B
Phase effective value calculation circuit, 37 ... C Phase phase calculation circuit, 38 ... C
Phase effective value arithmetic circuit, 39 ... Delay circuit, 40 ... Zero phase voltage effective value arithmetic circuit, 41-43 ... Comparison circuit, 44 ... Reference value,
45 to 50 ... Gate circuit, 51 ... A phase ground fault determination output terminal, 52 ... B phase ground fault determination output terminal, 53 ... C phase ground fault determination output terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Ishibashi 2-2-1 Miyauchi, Tagajo City, Miyagi Prefecture Tohoku Electric Manufacturing Co., Ltd. (72) Inventor Kiichi Shiraishi 2-2-1 Miyauchi, Tagajo City, Miyagi Prefecture Tohoku Electric Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A ground fault phase determination device used in a system in which a zero-phase voltage and its phase change depending on the value of the ground fault resistance when a ground fault occurs in a non-grounded or reactor grounded transmission / distribution line. Phase-shifting means for performing phase-shifting processing so that the ground-phase phase voltage and the zero-phase voltage have the same phase with respect to the zero-phase voltage and the three-phase voltage, and the phase-shifting processing is performed by this phase-shifting means. Computation means for computing a value corresponding to the phase difference between the zero-phase voltage and the three-phase voltage and the computation results of this computation means are compared to determine the phase with the smallest phase difference from the zero-phase voltage. A comparing means for judging a ground fault phase, a judging means for comparing the phase voltages of the three phases and judging a phase having the lowest level as a ground fault phase, a comparing means for judging the phase of the zero phase voltage, Selection means for selecting one of the determination results of the determination means. And a ground fault phase determination device. 2. A ground fault phase determination device used in a system in which a zero-phase voltage and its phase change according to the value of the ground fault resistance when a ground fault occurs in a transmission / distribution line of an ungrounded system or a reactor grounded system. Phase-shifting means for performing phase-shifting processing so that the ground-phase phase voltage and the zero-phase voltage have the same phase with respect to the zero-phase voltage and the three-phase voltage, and the phase-shifting processing is performed by this phase-shifting means. Computation means for computing the scalar product of the zero-phase voltage and the phase voltage of the three phases, respectively, and comparison means for comparing the computation results of this computation means and determining the phase that is substantially the maximum value as the ground fault phase. And a determination means for comparing the phase voltages of the three phases to determine the lowest phase as a ground fault phase, and a determination result of one of the comparison means and the determination means according to the level of the zero-phase voltage. 2. A ground fault phase determination device comprising: a selection unit that selects the.