JP3128584B2 - Ground fault line detection method and ground fault line cutoff method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ground fault line detection method for detecting a ground fault line when any ground fault occurs in a power system, and this method. The present invention relates to a ground fault line disconnection method in a case where a plurality of ground fault lines are detected.

[Prior Art] When a ground fault occurs in any line of a power system, conventionally, when a ground fault is detected by a ground fault relay, the line is cut off in a predetermined order, thereby causing an accident. The line was to be detected.

However, when the lines are cut off in a predetermined order as described above, there is a problem that a healthy line other than the accident line is cut off.

In order to solve such a problem, as disclosed in Japanese Patent Publication No. 59-194631, a zero-phase voltage of a bus and a zero-phase current of each line branched from the bus are detected, and before and after a ground fault occurs. The change in the zero-phase voltage of the bus and the change in the zero-phase current before and after the occurrence of ground fault for each line are calculated, and the phase difference between the change in the zero-phase voltage and the change in the zero-phase current in each line is calculated. A method for detecting a ground fault line based on the ground fault is disclosed. In the method disclosed herein, a sampling signal having a frequency that is twice the frequency of the power system is generated, and the zero-phase voltage and the zero-phase current are held each time the sampling signal is generated, so that the zero-phase voltage becomes a predetermined value. When the value is greater than or equal to
The amount of change between zero-sequence voltages having different hold times and the amount of change between zero-phase currents for each line are calculated.

[Problems to be Solved by the Invention] According to the method disclosed in the above publication, even if there is an imbalance in the ground capacity for each phase in each line, a ground fault line can be detected relatively accurately. Can be.

However, according to the known method disclosed in the above publication, when the zero-phase component temporarily increases due to a disturbance element such as an intermittent ground fault, the temporarily increased zero-phase component is removed. Since the residual zero-phase data is used, the amount of change in the zero-phase voltage before and after the detection, which is calculated when a zero-phase voltage equal to or higher than a predetermined value is detected, may be inappropriate. .

Further, according to the known method as described above, if a ground fault occurs on two or more lines, the detected lines must be shut down in a predetermined order, and the lines on which a serious accident has occurred. It may take some time to shut off the traffic.

The present invention has been made in view of such circumstances, and detects a zero-phase voltage of a bus and a zero-phase current of each line branched from the bus to detect a change in the zero-phase voltage before and after the occurrence of a ground fault and each of the zero-phase currents. A ground fault for calculating a change in the zero-phase current before and after the occurrence of a ground fault for each line, and detecting a ground fault line based on the phase difference between the change in the zero-phase voltage and the change in the zero-phase current in each line. In the line detection method, when a zero-phase voltage equal to or greater than a predetermined value is detected, even if the zero-phase component temporarily increases due to a disturbance element such as an intermittent ground fault before detection, the detection is almost accurately performed. It is an object of the present invention to provide a ground fault line detection method capable of accurately detecting a ground fault line by obtaining a change amount of the preceding and following zero phases.

Another object of the present invention is to provide a ground fault line disconnection method capable of sequentially disconnecting from a line having a large accident level in the case of a multiple accident in which a plurality of lines are detected by the above method. .

[Means for Solving the Problems] The ground fault line detection method according to the first invention, in order to achieve the above object, measures the zero-sequence voltage and each zero-sequence current at predetermined intervals,
The data of the measured zero-sequence voltage and the measured zero-sequence current are input to the digital low-pass filter, and the result is (constant M × data of the previous output of the digital low-pass filter + data of the measured zero-sequence voltage and the measured zero-sequence current). / (Constant M + 1), and compares the measured zero-phase voltage with the starting settling voltage for each phase. As a result of the comparison, when the measured zero-phase voltage is equal to or more than the starting settling voltage, Hold the output of the digital low-pass filter, and after this hold, calculate the difference between the measured zero-sequence voltage data and the hold output of the digital low-pass filter that receives this data as the change in the zero-sequence voltage before and after the ground fault occurs And the difference between the measured zero-sequence current data in each line and the hold output of the digital low-pass filter to which this data was input is the zero-sequence before and after the ground fault occurs. Calculated as a change in current.

In the ground fault line interruption method according to the second invention, the method of the first invention, that is, the zero-phase voltage of the bus and the zero-phase current of each line branched from the bus are measured at predetermined intervals, and the measured zero-phase current is measured. The data of the voltage and the measured zero-sequence current are input to the digital low-pass filter, and (constant M × data of the previous digital low-pass filter output + measured zero-sequence voltage and measured zero-sequence current data) / (constant M + 1 ), The measured zero-sequence voltage is compared with the starting settling voltage for each phase, and as a result of the comparison, when the measured zero-sequence voltage is equal to or more than the starting settling voltage, each digital low-pass filter at that time is determined. After this hold, the difference between the measured zero-sequence voltage data and the hold output of the digital low-pass filter to which this data was input is defined as the change in the zero-sequence voltage before and after the occurrence of the ground fault. And the difference between the data of the measured zero-sequence current in each line and the hold output of the digital low-pass filter to which this data was input was detected as a change in the zero-sequence current before and after the occurrence of the ground fault. When there are a plurality of lines, the lines are disconnected in the order of the absolute value of the change between the measured zero-sequence current and the residual zero-sequence current.

[Operation] According to the ground fault line detection method according to the first aspect of the present invention, a difference occurs between the output of the digital low-pass filter and the output of the digital low-pass filter when the measured zero-phase component rises sharply due to the attenuation characteristic of the digital low-pass filter. Here, the output of the digital low-pass filter is represented by an arithmetic expression of (constant M × data of previous digital low-pass filter output + data of measured zero-sequence voltage and measured zero-sequence current) / (constant M + 1). As described above, the measured zero-sequence voltage reaches the predetermined value by setting the attenuation characteristic appropriately using the data of the measured zero-sequence voltage and the measured zero-sequence current and the data of the output of the previous digital low-pass filter. The output of the digital low-pass filter at a point in time can be very close to the value at the rise of the measured zero-sequence current. Therefore, the difference between the measured zero-phase data and the output of the digital low-pass filter to which this data is input is very close to the zero-phase component that has increased due to ground fault.

According to the ground fault line blocking method according to the second invention, when multiple accidents occur, the line is cut off from the line with a large accident level, so that the line with a light accident level does not need to be shut down unnecessarily.

[Embodiment] Hereinafter, a ground fault detection method according to the present invention will be described in the case where a ground fault has occurred in a power system S schematically shown in FIG.

The power system S has twelve lines from a first line F1 to a twelfth line F12 branched from the bus M on the secondary side of the transformer T. Each line F1-F12 has a zero-phase current transformer ZCT1-Z
CT12 is provided. Further, a transformer GPT for a grounded instrument capable of extracting a zero-phase voltage of the bus M is connected to the secondary side of the transformer T. The above zero-phase current transformers ZCT1 to ZCT12
And the tertiary output of the ground-type instrument transformer GPT are input to the digital type distribution line ground fault selection control relay device 1.

The relay device 1 includes a zero-phase voltage of the bus M output from the ground-type instrument transformer GPT and the zero-phase current transformers ZCT1 to ZCT1.
Based on the zero-phase current of each of the lines F1 to F12 output from 2, a ground fault line is selected as follows.

The relay device 1 first measures the input zero-phase voltage and each zero-phase current at predetermined intervals, for example, every 200 msec.

The data of the measured zero-sequence voltage and each measured zero-sequence current (hereinafter referred to as the measured zero-sequence component) are A / D
After the conversion, they are input to the digital low-pass filters 11. These digital low-pass filters 11 have outputs Y [n] of (MY [n-1] + X [n]) /
(M + 1). here,
Y [n-1] is the previous output value of these digital low-pass filters 11..., And X [n] is the data for the measured zero phase. M is a constant, which is obtained as a function of the time constant of the digital filter 11. The output Y [n] of the digital low-pass filters 11...
If the measured zero-phase component X [n] rises sharply at t1, it rises with a much gentler gradient.

On the other hand, the measured zero-phase voltage of the measured zero-phase component is subjected to A / D conversion, and then input to the comparator 12. This comparator
Reference numeral 12 compares the input measured zero-sequence voltage value with a start set value for each phase. This startup set value is
For example, an empirical value is set to operate for a 6000 ohm single line ground fault. In this case, the absolute value of the measured zero-sequence voltage may be compared with the start set value, but if the coordinate data of the measured zero-sequence voltage is compared with the start set value, the phase angle can be compared. This is more preferable because it is possible to avoid line interruption due to an increased zero-phase voltage due to causes other than a ground fault.

Next, as a result of comparing the measured zero-sequence voltage and the start set value in the comparator 12 as described above, if the measured zero-sequence voltage has reached the start set voltage, the digital low-pass filter 11 Are held by the hold circuits 13. Referring to FIG. 2, when the data of the start set value (A) and the data of the measured zero-sequence voltage value X [nx] are compared at time t2, the start set value (A)
If ≦ measured zero-phase voltage value X [nx], at this time t2, outputs Y [nx] of all digital low-pass filters 11.
Are held in the hold circuits 13. All outputs Y [nx] held at time t2 in this manner are values at the time of the rising of the zero phase, which has started to rise due to the occurrence of the ground fault, that is, the ground fault, by appropriately selecting the above constant M. It can be approximated to the residual zero-phase component before the accident occurred. Therefore, the output Y [nx] can be regarded as substantially a residual zero-phase component (hereinafter, the output Y [nx] is referred to as a calculated residual zero-phase component).

Therefore, next, the data of the measured zero-phase component X [nx] and the output Y [nx] held by the holding circuit 13 corresponding to the digital low-pass filter 11 to which the data of the measured zero-phase component X [nx] are inputted. By calculating the difference, a change in the zero-phase voltage of the bus before and after the occurrence of the ground fault and a change in the zero-phase current of each line can be obtained. In this case, the measured zero-phase component X [nx]
The calculation of the difference between this data and the output Y [nx] is performed after a predetermined time after the hold by providing a timer. If the measured zero-phase voltage falls below the start set value within this predetermined time, the data of the measured zero-phase component X [nx] and the output Y
The calculation of the difference of [nx] is not performed, and the held output Y
A new Y [n] is calculated using [nx] as the previous output value.

If the measured zero-sequence voltage is still equal to or greater than the start settling value after the predetermined time and the difference between the data of the measured zero-sequence X [nx] and the output Y [nx] is calculated, A ground fault line is detected based on the obtained phase difference of the change of the zero-phase current of each line with respect to the change of the zero-phase voltage. In this example,
In the coordinate data Xv, Yv of the measured zero-sequence voltage, the coordinate data Xvo, Yvo of the calculated residual zero-sequence voltage, the coordinate data Xi, Yi of the measured zero-sequence voltage, and the coordinate data Xio, Yio of the calculated residual zero-sequence current, Xv−Xvo) (Yi−Yio) <(Xi−Xio) (Yv−Yv
o), that is, as shown in FIGS. 3A and 3B, the phase angle of the change Io of the zero-phase current is in the range of -180 ° with respect to the phase angle of the change Vo of the zero-phase voltage. An existing line is detected as a ground fault line. On the other hand, as shown in FIG. 3C, a line in which the phase angle of the change Io of the zero-phase current is in the range of + 180 ° with respect to the phase angle Vo of the change of the zero-phase voltage is regarded as a healthy line.

As described above, if a ground fault line is detected, even if a change occurs in the zero-phase component due to a disturbance such as an intermittent ground fault before a ground fault to be detected is generated, It is possible to obtain an accurate change of the zero phase before and after the occurrence of the ground fault without any influence.

Next, a description will be given of a ground fault line blocking method for blocking a plurality of ground fault lines detected as described above.

When there are multiple ground fault lines detected as described above,
In the ground fault line interrupting method according to the present invention, the plurality of ground fault lines are sequentially interrupted, for example, every two seconds from a line having a large absolute value of the change in the zero-phase current. That is, in the case of FIGS. 3A and 3B, the line corresponding to FIG. 3A in which the absolute value of the change Io of the zero-phase current is large is cut off before the line corresponding to FIG. 3B. As a result, a circuit having a small ground fault resistance and causing a serious accident is cut off first.

By blocking one line as described above,
If the measured zero-sequence voltage falls below the startup settling voltage,
The hold for each output Y [nx] performed at t2 is released, and these outputs Y [nx] are output to the digital low-pass filter 11.
.. As a previous output value Y [n-1].
[N] is calculated. Therefore, a line that does not need to be cut off is not unnecessarily cut off.

If the measured zero-sequence voltage has reached the start-up set value even though all of the detection ground fault lines have been shut off in the above procedure, the change in the zero-phase current in circuits other than the detection ground fault line The line with the largest absolute value is cut off.

In the above method, the means for holding the output Y [n] of the digital low-pass filter, that is, the means for selecting the starting time, is not necessarily the means for setting the starting set value as described above. Other means may be used, such as based on the gradient of the change in phase voltage.

According to the first aspect of the present invention, an output very close to the residual zero-phase component before the occurrence of the ground fault is obtained without being affected by disturbances such as intermittent ground faults. Since the increased zero-phase component can be detected, there is an effect that the ground fault line can be accurately detected based on the detected zero-phase component.

According to the second aspect of the present invention, when a ground fault has occurred in a plurality of lines, it is possible to cut off from the line in which the ground fault having a large accident level has occurred. The effect is that it can be limited to the limit.

[Brief description of the drawings]

FIG. 1 is a schematic power system diagram for explaining the method of the invention, and FIG.
3A to 3C are vector diagrams of a change in a zero-sequence voltage and a change in a zero-sequence current.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Yamaguchi 3-14-40 Senrioka, Settsu-shi, Osaka Higashi Koseiki Co., Ltd. (72) Inventor Tadashi Nakao 3-14-40 Senrioka, Settsu-shi, Osaka Higashi Within Kosei Seiki Co., Ltd. (72) Inventor Minoru Hiyoshi 3--14-40 Senrioka, Settsu-shi, Osaka Toko Kosei Seiki Co., Ltd. (56) References JP-A-59-194631 (JP, A) JP-A-2- 96668 (JP, A) JP-A-62-81925 (JP, A) JP-A-1-202120 (JP, A) JP-A-5-76132 (JP, A) JP-A-62-236322 (JP, A) JP-A-1-264530 (JP, A) JP-A-4-79718 (JP, A) JP-A-2-202119 (JP, A) JP-A-1-127332 (JP, U) (Int.Cl. ⁷ , DB name) H02H 7/26 G01R 31/08 H02H 3/00-3/44

Claims (2)

(57) [Claims] 1. A zero-phase voltage of a bus and a zero-phase current of each line branched from the bus are detected, and a change in the zero-phase voltage before and after a ground fault occurs and a zero-phase voltage before and after a ground fault occurs for each line. A ground fault line detection method of calculating a change in current and detecting a ground fault line based on a phase difference between the change in the zero-phase voltage and a change in the zero-phase current in each line. Each zero-sequence current is measured at predetermined intervals, and the data of these measured zero-sequence voltage and measured zero-sequence current are input to the digital low-pass filter. (Constant M × data of previous digital low-pass filter output + measurement An output operation of (zero-phase voltage and measured zero-phase current data) / (constant M + 1) is performed, and the measured zero-phase voltage is compared with the starting settling voltage for each phase. As a result of the comparison, the measured zero-phase voltage is started. When the voltage is higher than the settling voltage, The output of each digital low-pass filter at this time is held, and after this hold, the difference between the measured zero-sequence voltage data and the hold output of the digital low-pass filter that receives this data is calculated as the change in the zero-sequence voltage before and after the ground fault occurs. And calculating the difference between the measured zero-sequence current data in each line and the hold output of the digital low-pass filter to which the data is input as a change in the zero-sequence current before and after the occurrence of a ground fault. Ground fault line detection method. 2. A zero-phase voltage of a bus and a zero-phase current of each line branched from the bus are measured at predetermined intervals, and the data of the measured zero-phase voltage and measured zero-phase current are input to a digital low-pass filter. , (Constant M × data of previous digital low-pass filter output + data of measured zero-sequence voltage and measured zero-sequence current) / (constant M + 1), and the measured zero-sequence voltage is calculated for each phase. When the measured zero-sequence voltage is equal to or higher than the start settling voltage, the output of each digital low-pass filter at that time is held, and after this hold, the measured zero-sequence voltage data and The difference between the input data and the hold output of the digital low-pass filter is calculated as the change in the zero-sequence voltage before and after the occurrence of the ground fault. If there are multiple ground fault lines detected by calculating the difference between the data and the hold output of the digital low-pass filter that inputs this data as the change in the zero-phase current before and after the occurrence of the ground fault, the measured zero-phase current And a line in which the absolute value of the change of the residual zero-sequence current is interrupted in order.