JPS6142218A - Directivity ground-fault indicator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Part 1 of the Invention (Field of Industrial Application)] This invention relates to a directional ground fault indicating device attached to a power distribution line.

(Prior art) The currently widely used ground fault detection method is to detect zero-sequence voltage and zero-sequence current, and to compare the phases of the zero-sequence voltage and zero-sequence current. There is something that has this.

(Problems to be Solved by the Invention) This type of ground fault detection device requires a grounding transformer and a zero-sequence voltage detection capacitor, which increases the size and cost of the entire device.

When an oscilloscope is taken for various types of ground faults, namely, a complete resistance ground fault, an insulator ground fault, and a cable ground fault, the results are as shown in FIG. From these results, in the case of a ground fault through an electric wire or an insulator, the ground fault voltage and ground fault current always contain high frequency components. Furthermore, even in the case of a complete resistance ground fault, arcing is usually accompanied.
In the case of this arc ground fault, the ground fault voltage and ground fault current always contain high frequency components.

Structure of the Invention (Means for Solving the Problems) This invention attempts to solve the above problems by using the high frequency that accompanies the occurrence of the above-mentioned arc ground fault, etc. The fault detection device includes a ground fault signal detection circuit installed in each phase, a high frequency filter connected to the ground fault signal detection circuit that removes the fundamental wave component and leaves the high frequency component, and detects when a ground fault occurs on the power supply side. In this case, approximately the same fault current flows from the load side to the power supply side in each phase, so the level of the output signal of each phase obtained through each high frequency filter is compared to determine if a ground fault is occurring on the power supply side. If a one-phase ground fault occurs on the load side, the fault current will flow from the power supply side to the load side only in the ground fault phase, and the fault current will flow from the load side to the power supply side in the other two phases. Since the fault current flows in the ground fault phase and the level of the fault current in the ground fault phase is higher than the other two phases, the levels of the output signals of each phase obtained through the respective high frequency filters are compared to detect the ground fault fault. The gist of the system is to provide an indicator that displays a directional ground fault using a level determination circuit that determines whether a ground fault has occurred on the load side.

(Function) With the above configuration, when a ground fault occurs in any one phase of the distribution line, the ground fault signal is input to the high frequency filter via the ground fault signal detection circuit provided for each phase, and the high frequency filter The fundamental wave is removed.The signal from which the fundamental wave has been removed by the high-frequency filter in the ground fault phase is compared with the level of the output signal of the other phase using a level judgment circuit, and the result is displayed on the display to display the directional ground fault. Do the following.

In other words, when a ground fault occurs on the power supply side, approximately equal fault currents flow in each phase from the θ front side to the power supply side.

Therefore, since the levels of each phase are approximately equal, the same level determination circuit determines that a ground fault has occurred on the power supply side,
Directional ground fault indication is provided on the display.

On the other hand, if a ground fault occurs on the load side of the distribution line, the fault current will flow from the power supply side to the load side only in the ground fault phase, and the other two phases will flow from the load side to the N source side. A larger fault current flows through the ground fault phase than the other two phases. Therefore, the level judgment circuit judges the signal level of each phase, and since the level of the ground fault phase is higher than the other two phases, it judges that a ground fault has occurred on the load side. Provides ground fault indication with

(Embodiment) An embodiment embodying the present invention will be described below with reference to FIGS. 1 to 5.

A current transformer M1 as a ground fault signal detection circuit is attached to the insulated wires U, V, and W of each phase. A high frequency filter 2 for absorbing fundamental waves is connected to each current transformer 1, and a rectifier circuit 3 is connected to the high frequency filter 2. The rectifier circuit 3 converts the input signal from alternating current to direct current.

A level determination circuit 4 common to each phase is connected to the rectifier circuit 3, and the same level determination circuit 4 determines the level of the DC signal of each phase inputted via the rectifier circuit 3.

Based on the determination signal outputted from the level determination circuit 4,
The display 5 operates to display. In other words, when a ground fault occurs on the power supply side (see Figures 4 and 5), fault currents approximately equal to each other flow in each phase from the load side to the power supply side, so the level judgment circuit 4 determines that a ground fault has occurred on the power supply side, and outputs a determination signal to the display 5.

J3, 6 in the figure is the main transformer of the distribution substation.

If a ground fault occurs on the load side (see Figures 2 and 3), only the ground fault phase will be transferred from the power supply side to the load side.
fff current flows, a fault current flows in the other two phases from the load side to the power supply side, and a larger fault current flows in the ground fault phase than in the other two phases. Therefore, the level determination circuit 4 determines that the ground fault is the load. The judgment signal is sent to the display 5.
Output to.

The operation of the directional ground fault detection device configured as described above will be explained.

Now, if a ground fault occurs on the M source side, each phase will flow from the load side to the power source side with a fault current that is approximately equal to each other (Iu =
lv=1w) flows (see FIGS. 4 and 5). The current transformer 1 of the insulated wires U, V, and W of each phase is
The i current is detected, and the fundamental wave of the secondary current at that time is removed by the high frequency filter 2. The high frequency component from which the fundamental wave has been removed is converted from alternating current to direct current by the rectifier circuit 3.

Then, the level determination circuit 4 determines the level of the DC signal of each phase input through the rectifier circuit 3, and determines that a ground fault has occurred on the power supply side since the levels of each phase are approximately equal. , the display 5 displays a ground fault with directionality.

On the other hand, if, for example, a ground fault occurs on the load side of the distribution line W (see Figures 2 and 3), only the ground fault phase W will cause the fault Ill current to flow from the power supply side to the load side. In the other two phases, a fault current flows from the load side to the power supply side, and in the ground fault phase, a larger fault current flows than in the other two phases (IW>lu
, IV). The current transformers 1 of the insulated wires t, t, v, and w of each phase detect the fault current flowing at that time, and
The fundamental wave of the first current is removed by the high frequency filter 2. The convex frequency component from which the fundamental wave has been removed is converted from alternating current to direct current by the rectifier circuit 3.

Then, the level judgment circuit 4 judges the level of the DC signal of each phase input through the rectifier circuit 3, and since the level of the ground fault phase is higher than the other two phases, the ground fault fault has occurred on the load side. It is determined that a ground fault has occurred, and the display 5 displays a ground fault with directionality.

Note that the present invention is not limited to the above-mentioned embodiments, and can be arbitrarily modified without departing from the spirit of the present invention.

Effects of the Invention As detailed above, this invention does not require a grounding transformer or a zero-phase voltage detection capacitor, and only requires a ground fault signal detection circuit and a level judgment circuit, making the entire device smaller, lighter, and lighter. It is possible to reduce costs, and it is also possible to determine the ground fault phase.As a result, by installing this directional ground fault detection device at key points on the distribution line, the time required to locate the fault point can be shortened. 〒It has an excellent effect that is very effective in the old days.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of an embodiment embodying this invention.
Figure 2 is an explanatory diagram when a ground fault occurs on the load side, and Figure 3 shows the fault current flowing through each distribution line in Figure 2.
Explanatory diagram, Figure 4 is an explanatory diagram when a ground fault occurs on the power supply side,
Figure 5 is an explanatory diagram showing the amount of fault current flowing through each distribution line in the same way as in Figure 4, and Figure 6 shows each phase when various ground faults occur in the distribution line, and when it is normal. voltage, the voltage at the ground fault point. This is an oscilloscope of ground fault current and ground fault voltage. DESCRIPTION OF SYMBOLS 1... Current transformer, 2... High frequency filter, 3... Rectifier circuit, 4... Level determination circuit, 5... Display device.

Claims (1)

[Claims] 1. A ground fault signal detection circuit provided for each phase, a high frequency filter connected to the ground fault signal detection circuit that removes a fundamental wave component and leaves a high frequency component, and a ground fault signal detection circuit that removes a fundamental wave component and leaves a high frequency component. If a fault occurs on the power supply side, approximately the same fault current will flow in each phase from the load side to the power supply side. Therefore, the level of the output signal of each phase obtained through each high frequency filter is compared to detect a ground fault. It is determined that a fault has occurred on the power supply side, and if a ground fault in one phase occurs on the load side, the fault current flows from the power supply side to the load side only in the ground fault phase, and the load does not flow in the other two phases. Since the fault current flows from the side to the power supply side and the level of the fault current in the ground fault phase is higher than the other two phases, the levels of the output signals of each phase obtained through each of the high frequency filters are compared. What is claimed is: 1. A directional ground fault display device comprising: a level determination circuit that determines whether a ground fault has occurred on the load side; and a directional ground fault display.