JPH0613584Y2 - Ground fault phase discrimination relay device - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> In this invention, a ground fault phase detection angle range is set in advance, and a ground fault zero phase voltage in a distribution system is detected by a zero phase voltage detector. The present invention relates to a ground fault phase discrimination relay device that determines which phase of a power distribution system has a ground fault fault according to a detected angle range in which a ground fault zero-phase voltage appears.

<Prior Art> Conventionally, as a device for detecting a ground fault in a distribution system, as shown in the block diagram of FIG. 4, an instrument transformer (hereinafter abbreviated as GPT) (1) ′ and a ground fault are used. Phase discrimination unit (8) ′
And the ground fault phase discriminating unit (8) 'determines the phase of the zero-phase voltage detected by GPT (1)', and performs the ground fault phase determination only within the preset detection angle range. A phase discrimination relay device is known.

Hereinafter, this conventional example will be described with reference to the principle diagram of FIG.

First, the zero-phase voltage o at the time of a one-line ground fault (A-phase ground fault) in an ungrounded distribution line is o = −a / {1 + Rg (1 / Rn + j3ωC)} ... [I: (A-phase ground fault) Given in.

However, Rg: Fault resistance (Ω) Rn: System-side conversion value of GPT third-order current limiting resistance 3C: Total ground capacitance (F) of the bank, Ea: Phase voltage At this time, Rn is sufficiently large and can be ignored. The formula [I] is as shown in the formula [II] below.

o = −a / {1 + j3ωCRg} ... [II] where 1 / 3ωC = Xc is set o = −a / {1 + j (Rg / Xc)} where Rg / Xc = γ is set = −a / (1 + jγ) ... [III] is obtained.

By modifying the above formula [III], the following formula is obtained.

o = Voc + jVos = {− 1 / (1 + γ ² ) + jγ (1 + γ ² )} a {However, Voc and Vos represent the real part and imaginary part of o, respectively. Here, it is assumed that a is a reference vector of size Ea. Then, when divided into a real part and an imaginary part, Voc = −Ea / (1 + γ ² ), Vos = γEa / (1 + γ ² ).

Therefore, Voc ² + Vos ² = (1 + γ ² ) Ea ² / (1 + γ ² ) ² = Ea ² / (1 + γ ² ) = − VocEa Therefore, (Voc + Ea / 2) ² + Vos ² = (Ea / 2) ² or more, The locus of o when γ (= Rg / Xc) changes is a semicircle in Fig. 5 (a), and the locus of -o is a dotted line.

FIG. 5 (b) shows the locus of the zero-phase voltage −o at the time of the one-line ground fault, for each phase. The diagonal lines indicate the detected angle range of each phase. That is, the A-phase ground fault detection angle range is such that the delay is 90 ° to 30 ° with respect to a.

As is clear from the equations of Voc and Vos shown above, γ
As (= Rg / Xc) becomes larger (that is, the degree of ground fault becomes smaller), the zero-phase voltage -o becomes a (or b, c).
It can be seen that the origin is approached more along the semicircle. Here, γ (= Rg / Xc) is large because Rg is large,
That is, if the degree of ground fault is small (fine ground fault), or Xc
Is small, that is, the ground capacity of the bank is large.

As can be seen from FIG. 5 (b), the phase of the zero-phase voltage −o changes within the range of 0 ° to 90 ° with respect to a, b, or c.

<Problems to be Solved by the Invention> In the ground fault phase discrimination relay device described above, when the zero phase voltage −o is small, that is, in the case of a fine ground fault, the phase angle of the zero phase voltage −o is a single phase. With the voltage component a as a reference, the position approaches the position with a delay of 90 °. -O is delayed by 90
When approaching 0 °, the zero-phase voltage is
90 ° to 30 °), the detection angle range β
It is difficult to determine whether it appears in (progress 150 ° ~ advance 270 °).

Therefore, the above-mentioned ground fault phase discrimination relay device has a problem that it is difficult to accurately detect the ground fault phase with respect to a minute zero-phase voltage.

The present invention has been made in view of the above problems, and a ground fault phase discrimination relay capable of accurately discriminating the ground fault phase even when the zero-phase voltage generated at the time of a ground fault in a distribution line is minute. The purpose is to provide a device.

<Means for Solving the Problem> In order to achieve the above-mentioned object, the ground fault phase discrimination relay device of the present invention has the above-mentioned detection angle according to the magnitude of the ground fault zero-phase voltage detected by the zero-phase voltage detector. Phase shift means for shifting the range or the phase of the ground fault zero-phase voltage.

<Operation> In the ground fault phase discrimination relay device having the above configuration, the detection angle range of the ground fault phase is set in advance corresponding to each phase, and the ground fault zero phase voltage detected by the zero phase voltage detector is detected. When determining which phase of the distribution system has a ground fault by the detected angle range, the phase shifter shifts the detected angle range according to the magnitude of the detected zero-phase voltage. Therefore, the ground fault phase can be discriminated by detecting in which phase of the shifted detection angle range the zero-phase voltage appears.

The ground fault phase can also be discriminated by fixing the detection angle range and shifting the zero-phase voltage.

Therefore, compared with the fixed setting of the detection angle range at the time of the ground fault as in the conventional example, the detection angle range changes according to the magnitude of the zero-phase voltage, which increases the phase discrimination margin and stabilizes. In addition, the phase can be reliably determined without erroneous detection.

<Embodiment> An embodiment of a ground fault phase discrimination relay device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the hardware of this embodiment. This ground fault phase discrimination relay device is a sample hold circuit (hereinafter referred to as a sample hold circuit) for sampling a zero phase voltage which is an analog signal output from GTP (1) at a predetermined cycle. , Simply called S / H circuit)
(2), an analog / digital converter for converting the sampled zero-phase voltage into digital data (hereinafter, simply referred to as an A / D converter) (3), and transferred from the A / D converter. A data memory (4) for temporarily storing digital data, and a control program (monitor program) for storing the preset zero-phase voltage detection angle range for each phase and controlling each of the above parts Read-only memory that stores (hereinafter simply referred to as ROM)
(5), and a CPU (9) incorporating each of a comparison unit (6), a phase shift unit (7), and a ground fault phase discrimination unit (8) described later.

To explain the CPU (9) in more detail, the comparison unit (6) is configured so that the zero-phase voltage -o output from the GPT (1).
Of the absolute value | Vo | of the zero-phase voltage −o is smaller than a preset threshold Vs, the voltage (phase) of the “LO” level (phase) is compared. The shift command signal) is output, and if it is larger, the "HI" level voltage (a signal indicating that the phase is not shifted) is output.

Next, the phase shift unit (7) shifts the detection angle range in accordance with the comparison determination signal output from the comparison unit (6), and is a zero stored in advance in the ROM (5) for each phase. Phase angle detection angle range α, β, γ {for example, A based on Ea
The phase detection angle range is α (delay 90 ° to advance 30 °), the B phase detection angle range is β (advance 150 ° to advance 270 °), and the C phase detection angle range is γ (advance 30 ° to advance 150 °). ))} Is shifted by a predetermined angle (for example, a delay of 30 °).

The ground fault phase discriminator (8) detects the detected angle range α, β, γ, or the detected angle obtained by shifting the digital data of the zero phase voltage previously stored in the data memory (4) by the phase shifter. The ground fault phase is discriminated depending on which phase of the range appears, and the discrimination result is output.

Next, the operation of the ground fault discrimination relay device configured as described above will be described with reference to the phase characteristic diagram of FIG.

First, the zero-phase voltage −o detected by GPT (1) is
It is sampled in the S / H circuit (2), converted into digital data in the A / D converter (3), transferred to the data memory (4) and stored therein. The CPU (9) accesses the data memory (4) and reads the digitally converted data.

Then, the comparison unit (6) compares the magnitude of the absolute value | Vo | of the zero-phase voltage −o with a preset threshold value,
The comparison determination signal (signal level "1" or "0") is output.

The phase shift unit (7) shifts the detected angle range by a predetermined angle according to the comparison determination signal from the comparison unit (6).

For example, if the phase A is explained, the comparison judgment signal is "LO".
If it is a voltage of a level, as shown in the phase characteristic diagram of FIG. 2, the detection angle range is phase-shifted within the range of the delayed phase 120 ° and the advanced phase 0 ° with reference to the single-phase voltage component Ea.
Phase shifts of the B and C phases are also set to be delayed by 30 °, and conversely, if the comparison determination signal is the voltage of the “HI” level, the detection angle range is not shifted.

Then, the ground fault phase discriminating section (8) indicates in which phase of the detected angle range α, β, γ the digital data of the zero phase voltage previously stored in the data memory (4) appears. And determine the ground fault phase. The result of this determination is transmitted to the central office to control the disconnection of the distribution system.

Incidentally, FIG. 3 shows an example of a schematic flow chart of the control program (monitor program).

First, the CPU (9) accesses the data memory (4), and the previously stored digital data of the zero-phase voltage −o is stored in the CPU.
Input in (9) (step 1). Next, the comparison unit (6)
The absolute value | Vo | of the zero-phase voltage −o is compared with a preset threshold Vs, and if Vo ≦ Vs, the signal level “0”
"LO" level voltage corresponding to is output. On the contrary,
If Vo ≧ Vs, the “HI” level voltage corresponding to the signal level “1” is output (step 2). Phase shift unit
(7) receives the comparison determination signal from the comparison unit (6), and if YES, shifts the detected angle range by a predetermined angle (step 4). On the contrary, if NO, the preset detection angle range is not shifted (step 3). And the ground fault phase discriminator
(8) determines in which phase of the detection angle range set in (steps 3 and 4) the digital data of the zero-phase voltage previously stored in the data memory (4) appears. Ground fault phase discrimination is performed (step 5).

The ground fault phase discrimination relay device of the present invention has been described above with reference to the embodiment. In this embodiment, the reference phase detection angle range is advanced with respect to the single-phase voltage component a as the reference and the phase is 0 °. (The same phase as the single-phase voltage component Ea) and the lag phase were phase-shifted within the range of 120 °, but this was linearly shifted according to the magnitude of the zero-phase voltage in the case of a fine ground fault. It is possible to
It is also possible to fix the detected angle range and shift the phase of the zero-phase voltage itself.

Needless to say, the single-phase voltage component used as the reference voltage may be a line voltage that remains sound even when a one-line ground fault occurs.

<Effects> As described above, according to the ground fault phase discrimination relay device of the present invention, by shifting the detection angle range according to the magnitude of the zero phase voltage, when the zero phase voltage is small, that is, when there is a slight ground fault. Since it is possible to accurately determine the ground fault phase,
There is a unique effect that erroneous detection can be prevented when a fine ground fault occurs.

[Brief description of drawings]

FIG. 1 is a hardware configuration diagram of an embodiment according to the present invention, FIG. 2 is a phase characteristic diagram after phase shift by a phase shift unit, FIG. 3 is a schematic flowchart of a monitor program, and FIG. , A block diagram showing a conventional example, FIG. 5 (a) is a principle diagram showing a locus of zero-phase voltage o, and FIG. 5 (b) is a circle showing a locus of zero-phase voltage o at the time of a ground fault. A line diagram and a phase characteristic diagram showing a detection angle range. (1) …… GPT, (6) …… Comparison section, (7) …… Phase shift section, (8) …… Ground fault phase discrimination section

Claims (1)

[Scope of utility model registration request] 1. A ground fault phase detection angle range is set in advance for each phase, and a ground fault zero phase voltage in a distribution system is detected by a zero phase voltage detector to detect the ground fault zero phase voltage. In the ground fault phase discrimination relay device that determines which phase of the distribution system has the ground fault fault according to the detected angle range, the magnitude of the ground fault zero phase voltage detected by the zero phase voltage detector is detected. A ground fault phase discrimination relay device comprising a phase shift means for shifting the detected angle range or the zero phase voltage in accordance therewith.