JP2969468B2 - Disconnection detection method for zero-phase input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention detects a disconnection of a zero-phase component input device such as a ground-type instrument transformer or a zero-phase current transformer provided for detecting a ground fault. On how to do.

[Prior Art] Conventionally, whether or not this kind of zero-phase component input device is disconnected is known by inspecting individual devices, for example, by performing a periodic check. Was common.

[Problems to be Solved by the Invention] However, if it is only possible to know whether or not the zero-phase component input device is disconnected when the individual is inspected, the zero-phase component input device is disconnected. As a result, the ground fault accident detection work proceeds, and there is a possibility that the state where accurate detection is not performed continues.

The present invention has been made in view of the above-described accident, and detects a disconnection of the zero-phase component input device in accordance with the detection of the ground fault, thereby continuing the state in which the detection is performed while the disconnection occurs. It is an object of the present invention to provide a method for detecting a disconnection of a zero-phase component input device that can minimize time.

[Means for Solving the Problems] A method for detecting a disconnection of a zero-phase component input device according to a first invention for achieving the above object is to detect a ground fault in a power system in which a plurality of lines are branched from a bus. A method for detecting a disconnection of a zero-phase component input device provided in the system, wherein when a ground fault is detected, a residual component calculated from an output of a grounded type instrument transformer connected to a bus is corrected. The phase voltage is equal to or less than the estimated zero-phase voltage at the time of the occurrence of the ground fault desired to be detected when the ground capacitance is set to the maximum estimated value, and is calculated from the output of the zero-phase current transformer connected to each line. A disconnection detection signal is output when the largest zero-phase current of the zero-phase currents whose residuals have been corrected is greater than or equal to the estimated zero-phase current at the time of the complete ground fault at least when the ground capacitance is set to the minimum estimated value. It is characterized by generating.

A method for detecting a disconnection of a zero-phase component input device according to a second aspect of the present invention, which achieves the above object, comprises a zero-phase component input device provided for detecting a ground fault in a power system in which a plurality of lines are branched from a bus. A method for detecting disconnection of a device, comprising detecting a ground fault line, correcting a residual before the detected ground fault line has a zero-phase voltage equal to or greater than a first set value, and detecting a residual ground fault line before the break. Is zero or less, the zero-phase voltage corrected for the residual after the detection ground fault line is cut off is sufficiently smaller than the first set value. It is characterized in that a disconnection detection signal is generated when the value becomes equal to or less than a third set value indicating the return to normal.

To achieve the above object, a method for detecting a disconnection of a zero-phase component input device according to a third aspect of the present invention is a zero-phase component input device provided for detecting a ground fault in a power system in which a plurality of lines are branched from a bus. A method for detecting disconnection of equipment, wherein a ground fault line is detected, and the largest zero-phase current among zero-phase currents of at least residual lines calculated from the output of a zero-phase current transformer among the detected lines is corrected. Is greater than or equal to the fourth set value, and when the vector addition value of the detected zero-phase currents of all the lines is larger than the fifth set value, a disconnection detection signal is generated.

[Operation] According to the first aspect of the present invention, even when the zero-phase voltage, which should have been output, is not output when the ground fault to be detected occurs, the capacitance to ground is the smallest. Since the corrected zero-phase current generated at the time of the complete ground fault is measured, it is possible to detect the disconnection of the grounded type instrument transformer at least at the time when the complete ground fault occurs.

According to the second invention, although the zero-phase current corrected for the residual before the cut-off is equal to or less than the second set value, the line is cut off. When the zero-sequence voltage, which has been equal to or greater than the value, has become equal to or less than the third set value indicating the restoration of soundness, it is detected that the zero-phase current transformer of the line in which the ground fault has occurred has broken.

According to the third invention, the magnitude of the vector addition value of the detected zero-sequence currents of all the lines is larger than the fifth set value, and the zero is obtained by removing the residual in the line determined to be the ground fault line. When the largest zero-phase current among the phase currents is equal to or larger than the fourth set value, a ground fault occurs on the line side instead of the bus side, and the zero-phase current transformer connected to a line other than the ground fault line. Detect that the device is disconnected.

[Embodiment] Hereinafter, the present invention will be described as a zero-phase component input device as a grounded-type instrument transformer GPT and zero-phase current transformers ZCT1 to ZCT12 provided in a power system S as shown in FIG.

The grounding type transformer GPT is connected to the bus M, while the zero-phase current transformers ZCT1 to ZCT12 are connected to the first line F1 branched from the bus M.
To the twelfth line F12.

In this power system S, a ground fault line can be selected based on the zero-phase components input from the ground-type instrument transformer GPT and the zero-phase current transformers ZCT1 to 12, that is, the zero-phase voltage and the zero-phase current of each line. It has become. The choice of this ground fault line is
This is done as follows.

That is, first, the zero-sequence voltage and each zero-sequence current are detected at predetermined intervals, and the measured zero-sequence voltage and the measured zero-sequence current are input to the digital low-pass filter, and the ground fault voltage reaches the start settling voltage. , The output of each digital low-pass filter at that time is held. Next, the difference between the measured zero-sequence voltage and the hold value of the digital low-pass filter output to which the measured zero-sequence voltage is input is calculated as a change in the zero-sequence voltage before and after the occurrence of a ground fault, and the measured zero-sequence voltage in each line is calculated. The difference between the phase current and the hold value of the digital low-pass filter output to which the measured zero-phase current is input is calculated as the change in the zero-phase current before and after the occurrence of the ground fault, and the calculated change in the zero-phase voltage and the zero-phase current are calculated. The ground fault line is selected based on the phase difference of the change. That is, for example, if the phase of the change in the zero-phase current is within + 180 ° with respect to the phase of the change in the zero-phase voltage, the line is selected as a healthy line, and if the phase is within -180 °, the ground line is selected.

However, the selection of the ground fault line may be performed using other known means (for example, a means disclosed in Japanese Patent Publication No. 59-194631) instead of the above means.

In this power system S, when the ground fault line is selected as described above, the line is sequentially cut off from the line determined to be the ground fault line, in which the absolute value of the zero-phase current is large. When the line does not return to the ground line, the lines that are not determined to be ground fault lines are disconnected in order of increasing absolute value of the zero-phase current.

Now, in the system S as shown in FIG. 1, for example, when the voltage of the bus M is 6600 V and the primary
Next winding ratio The primary / secondary winding ratio of the zero-phase current transformers ZCT1 to 12 is 1.5 / 200, the current limiting resistance of the grounding type transformer GPT is 50Ω, and the capacitance of the system and each line to the ground is balanced. Is assumed to be 1/12 of the system ground capacitance,
Zero-phase currents of the zero-phase current transformers ZCT1 to ZCT12 at the time of complete ground fault, that is, zero-sequence currents in which residuals are corrected (hereinafter referred to as corrected zero-phase currents) The effective value of the current is 8.90 mA, and the ground capacitance is estimated at 7 μF.
Zero-phase voltage corrected for the tertiary voltage of the ground-type instrument transformer GPT at the time of a 00Ω ground fault, that is, the residual (hereinafter, corrected zero-phase voltage)
Is 2.31V. Here, the ground capacity of 0.3 μF is the minimum guess value of the ground capacity, and 7 μF is the maximum guess value of the ground capacity. 6000Ω is the magnitude of the ground fault resistance that is desired to be detected when the ground fault line is detected.

Under these conditions, the effective value of the corrected zero-sequence voltage is 2V
Below, if the effective value of the largest corrected zero-phase current is 8 mA or more, a disconnection detection signal is generated on the assumption that the ground-type instrument transformer GPT has a disconnection. That is, when a complete ground fault occurs, even though the corrected zero-phase current that occurs is detected even if the ground capacitance is the minimum guess value,
If the corrected zero-sequence voltage is smaller than the corrected zero-sequence voltage that occurs when the ground capacity is the maximum guess value during a 6000 Ω ground fault, it is determined that the ground-type instrument transformer GPT has an open circuit. .

Next, when a disconnection has occurred in any of the zero-phase current transformers ZCT1 to ZCT, the disconnection is detected as follows.

First, as shown in FIG. 2A, the disconnected zero-phase current transformer ZCT1
If the ground fault occurs in the line F1 having the line, the corrected zero-phase voltage before the line F1 is cut off is equal to or more than the first set value and the line
The corrected zero-sequence current before the cutoff of F1 is equal to or less than the second set value, and the zero-sequence voltage corrected for the residual after the cutoff of the line F1 is equal to or less than the third set value indicating the return to normal. When it becomes, a disconnection detection signal is generated. That is, a certain line F1
As a result, the corrected zero-sequence voltage becomes equal to or less than the third set value, and therefore, although the line F1 is determined to be the ground fault line, the corrected zero-phase current before the line F1 is cut off is equal to or less than the third set value. If the set value has not reached 2, the zero-phase current transformer ZCT1 provided in the line F1 is assumed to be disconnected, and a disconnection detection signal is generated. In this case, the second set value for the corrected zero-sequence current before interruption is estimated to be generated at the ground fault to be detected, that is, at 6000Ω ground fault in this embodiment when the ground capacity is the minimum guess value. The value can be set to a value smaller than the corrected zero-phase current 3.84 mA, for example, 3 mA. In addition, the first set value for the corrected zero-sequence voltage before cutoff is a value larger than the corrected zero-sequence voltage 47.53 V which is estimated to be generated at a 6000Ω ground fault to be detected when the ground capacitance is the minimum guess value. For example, it can be set to 55V.

Next, as shown in FIG. 2B, the disconnected zero-phase current transformer ZCT1
When a ground fault occurs in the line F2 other than the line having the ground fault, the largest correction zero calculated from the output of the zero-phase current transformer among the lines determined to be the ground fault line by the above-described ground fault line selecting means. A disconnection detection signal is generated when the phase current is greater than or equal to the fourth set value and the vector addition value of the detected zero-phase currents of all the lines is larger than the fifth set value. That is, when the vector addition value of the detected zero-phase current does not become 0, as shown in FIG. 2B, the line F2 other than the line having the disconnected zero-phase current transformer ZCT1
In addition to the case where a ground fault has occurred, as shown in FIG. 2C, a case where a ground fault has occurred on the bus M side without a disconnected zero-phase current transformer can be considered. However, in the case of FIG. 2C, only a current flows in each line according to the capacitance of the line to the ground. Therefore, if the largest corrected zero-sequence current is larger than the corrected zero-sequence current caused by the capacitance to ground, which is expected when the zero-phase current transformer is not disconnected, As shown in Figure 2B, it can be considered that a ground fault has occurred in the line F1 where the largest corrected zero-sequence current is flowing, and that the zero-phase current transformer ZCT2 in the other line F2 is disconnected. it can. In this case, the fourth set value for the largest corrected zero-sequence current is set to be 3.84 mA or less, which is the calculated zero-sequence current when a ground fault of 6000Ω to be detected occurs when the ground capacitance is the minimum estimated value. Preferably, it may be set to a higher value, for example, 50 mA, depending on the accuracy of the device itself. The fifth set value of the detected zero-sequence current with respect to the vector addition value may be smaller than the largest corrected zero-sequence current, and may be, for example, 10% of the corrected zero-sequence current in accordance with the error of the entire apparatus. .

By doing so, the disconnection that occurs in the zero-phase component input device in the power system S as shown in FIG. 1, that is, the ground-type instrument transformer GPT or the zero-phase current transformers ZCT1 to ZCT12 is detected. be able to. When any of the disconnections is detected, a countermeasure such as driving a display unit such as an LED or outputting recording data is performed.

In the above embodiment, the disconnection of the ground-type instrument transformer GPT, the disconnection of the zero-phase current transformer of the faulty line where the ground fault has occurred, and the zero-phase current transformer of the healthy line where the ground fault has not occurred. All disconnections are detected by the detection method according to the invention,
These detection methods can be individually adopted. Only the disconnection of the zero-phase current transformer of the faulty line in which the ground fault has occurred may be detected by the method of the invention, and other disconnections may be detected by a method other than the method of the invention.

[Effects of the Invention] According to claims 1 to 3, the disconnection of the zero-phase component input device is detected in accordance with the detection of the ground fault, so that the duration of the state in which the detection is performed with the disconnection occurring is reduced. It is possible to suppress the influence to a minimum, thereby quickly eliminating the adverse effect on the subsequent ground fault detection.

Put out.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a power system employing a method for detecting disconnection of a zero-phase component input device according to the present invention, and FIG. 2A illustrates a method for detecting disconnection of a zero-phase current transformer in a line in which a ground fault has occurred. FIG. 2B is a circuit diagram illustrating a method for detecting a disconnection of a zero-phase current transformer in a healthy circuit, and FIG. 2C is a circuit diagram illustrating a case of a bus ground fault. GPT …… Transformers for grounded instruments ZCT1 ～ 12 …… Zero-phase current transformers

Continuing on the front page (72) Inventor Hiroaki Yamaguchi 3-14-40 Senrioka, Settsu-shi, Osaka Toko Seiki Co., Ltd. (72) Inventor Tadashi Nakao 3-14-40 Senrioka, Settsu-shi, Osaka Toko Seiki Co., Ltd. In-company (72) Inventor Minoru Hiyoshi 3-14-40 Senrioka, Settsu-shi, Osaka Toko Seiki Co., Ltd. (56) References JP-A-1-77419 (JP, A) JP-A-2-70220 (JP) , A) JP-A-2-188120 (JP, A)

Claims (3)

(57) [Claims] A method for detecting a disconnection of a zero-phase component input device provided for detecting a ground fault in a power system in which a plurality of lines are branched from a bus, comprising the steps of: Zero-phase voltage corrected for the residual calculated from the output of the grounded-type instrument transformer connected to the bus, and detection when the ground capacitance is set to the maximum estimated value. The largest zero-phase current among the zero-phase currents that are equal to or less than the phase voltage and whose residuals are calculated from the output of the zero-phase current transformer connected to each line is the least estimated value of at least the ground capacitance. A disconnection detection method for a zero-phase-sequence input device, wherein a disconnection detection signal is generated when the current is equal to or greater than a trial-calculated zero-phase current at the time of a complete ground-fault accident. 2. A method for detecting a disconnection of a zero-phase component input device provided for detecting a ground fault in a power system in which a plurality of lines are branched from a bus, comprising detecting and detecting a ground fault line. The zero-phase voltage corrected for the residual before the ground fault line is cut off is equal to or greater than the first set value, and the zero-phase current corrected for the residual of the detected ground fault line before cut off is set to the second set value or less, In addition, when the zero-sequence voltage corrected for the residual after the detection ground fault line is cut off is equal to or less than a third set value indicating a healthy restoration sufficiently smaller than the first set value,
A method for detecting a disconnection of a zero-phase component input device, comprising generating a disconnection detection signal. 3. A method for detecting a disconnection of a zero-phase component input device provided for detecting a ground fault in a power system in which a plurality of lines are branched from a bus, comprising: detecting a ground fault line; Among the detected lines, the largest zero-sequence current of the zero-sequence current corrected for the residual calculated from the output of the zero-phase current transformer is equal to or greater than the fourth set value, and the detected zero-sequence of all lines is A disconnection detection method for a zero-phase input device, wherein a disconnection detection signal is generated when a current vector addition value is greater than a fifth set value.