JPS636834B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting short-circuit fault points in overhead distribution lines.

As a recent trend, as part of efforts to improve the reliability of power distribution equipment, high-voltage power distribution lines are being coated, and this has greatly contributed to the reduction of power line-related accidents. However, when two or more wires are flashed near the insulator due to a lightning strike, it progresses to a different-phase ground fault, and as a result, coated insulated wires are more likely to break than bare wires, and they are more susceptible to wire breakage. The duration of the accident is short, and the disconnection causes the conductor to dig into the insulator at the disconnected surface. Therefore, even if a broken power distribution line falls to the ground, the substation protection relay may not be expected to operate, and even if it operates, there are cases in which power is successfully retransmitted.

In order to prevent this, in recent years, distribution line relays with different-phase ground fault detection have been installed at substation distribution line outlets. Action of the relay takes measures to stop the reclosing, while
Once the broken line is discovered, power is immediately transmitted to healthy sections and repair work is carried out, but it takes a considerable amount of time to discover the point of the fault.

Therefore, an object of the present invention is to provide a method that can quickly and accurately detect short-circuit and disconnection accidents caused by lightning damage or the like in overhead distribution lines.

The principle of the present invention is that the line short-circuit current is a function of the line impedance determined by the line configuration and distance, so it is possible to determine the relationship between the distance from the substation and the short-circuit current in advance. Based on that. In other words, line short-circuit current is detected in the main distribution line, compared with a high-voltage line short-circuit current distribution map created in advance, etc., the distance section to the fault point is determined, and the status of each branch line corresponding to that position is determined to be short-circuited. Individual detection is performed using a current passing indicator. Specifically, upon receiving notification of an accident, we rush to the installation point of the short-circuit current indicator, check the current value and short-circuit phase, and draw a high-voltage line short-circuit current distribution diagram (as shown in Figure 4). (details will be described later),
By determining the area where a short-circuit accident will occur from the drawing, the short-circuit current passage indicator is sequentially tracked from the power supply side at the predicted accident occurrence location.

That is, the short-circuit accident point detection method for an overhead power distribution line according to the present invention includes a short-circuit current indicator provided on the main line of the overhead power distribution line and a short-circuit current passing indicator provided in the branch line thereof, and the short-circuit current indicator includes: has a first display section that displays a short-circuit current value depending on the distance from the reference point to the fault point, and a second display section that displays the phase in which the fault point occurs, and the short-circuit current passing indicator is compatible. has a third display section that displays when a predetermined overcurrent flows in the branch line, and displays a short circuit current value according to the distance of the main line and the branch line to the fault point based on line parameters. Prepare a current distribution diagram calculated in advance, and when the first display section displays a short circuit current value, determine the distance to the accident point by referring to the current distribution diagram based on the current value, and Second
Then, the line where the accident occurred and its phase are identified from among the main lines or branch lines located at the distance determined based on the display state of the third display section.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of a method for detecting a short circuit current fault point according to an embodiment of the present invention. In Figure 1, SS is a substation, Lm is a distribution main line, Lb ₁ , Lb ₂ ,
Lb ₃ ...... is the distribution branch line. The trunk line referred to here is the main part of the distribution line from the substation to the demand area. Further, a branch line is a branch-like portion of a distribution line that branches off from a main line.
SA is a short circuit current indicator (hereinafter referred to as an indicator)
It is attached to the main line Lm, and its electrical connection can be shown in Figure 2. Special CTs (insulators with a built-in current transformer that do not magnetically saturate within a predetermined operating range and provide an output voltage precisely proportional to the input current) ICT ₁ to _{ICT 3} are used as short-circuit current detection means, and their output coils are Make a Y connection and display the meter.
SA input terminals 1S, 2S, 3S, L and cables
Connected via CA ₁ . P ₁ and P ₂ are display meters
This is the SA power supply terminal. Display meter SA is current transformer ICT ₁
~ Obtain the detection output from ICT ₃ , and if a short-circuit current higher than the set value flows for a specified time, the current value is digitally displayed using Magsign MS ₁ (a well-known mechanical display mechanism made by electromagnetic action). In addition to displaying (effective value display), it also clearly indicates the energized phase using Magsign MS ₂ , and has the function of automatic and manual recovery after a certain period of time after the line voltage is restored. Then, after the display, no response is made to the short circuit current that occurs again during the recovery operation. The explanation will be continued with reference to FIG. 1 again. SI ₁₁ , SI ₁₂ , SI ₁₃ , SI ₂ ,
SI ₃ is a short-circuit current passage indicator (hereinafter referred to as a passage indicator), one or more of which is attached to each branch line Lb ₁ , Lb ₂ , Lb ₃ , and its electrical connection is with the indicator SA. You can think of it in the same way. If the number of passage indicators attached to each branch line Lb ₁ , Lb ₂ , Lb ₃ increases, it will become easier to detect the accident point. The configuration can be considered as if a passing indicator SI was installed in place of the indicator SA in FIG. 2. And its function is a current transformer
When the detection output from ICT ₁ to _{ICT 3} is obtained and a short-circuit current exceeding the set value flows for a specified time, the display section will be activated and will display the passing of the short-circuit current, and will also display a signal for a certain period of time after the line voltage is restored. It has an automatic return function.

In addition, as a function of the passage indicator handled in the present invention,
It is not necessary to limit the display only to the passing of the short circuit current, and a short circuit phase display function may be added in the same manner as the display meter.

FIG. 3A shows the first circuit configuration of the display SA.
The detection output from current transformers ICT ₁ to _{ICT 3} is output from transformer 10.
The output becomes the input to the AC amplifier circuit 11,1.
2 input. The output of the amplifier circuit 12 becomes the input of the level detection circuit 13, and its output is given to an AND circuit 14 and an OR circuit 15. AND circuit 1
The output of 4 is input to the energizing circuit of the phase indicator 16,
The output of OR circuit 15 is the timer 17 and AND circuit 1
8 and the output of the AND circuit 18 is input to the timer 19.

On the other hand, the output of the amplifier circuit 11 is inputted via a rectifier circuit 20 to a peak hold circuit 21 that reads the peak of the current value, and its output is given to a voltage frequency conversion circuit 22 and a lower limit comparator 23. The current value is converted into a frequency signal by the voltage frequency conversion circuit 22, and integrated and decoded by the counting decoding circuit 24 to become an energizing signal for the current value display section 25. The output of the lower limit comparator 23 is sent to the AND circuits 14 and 18. It is configured to be given.

A predetermined voltage is taken out from a pole transformer 26 as a power source for each of the above circuits, and a constant voltage is supplied to each circuit via a rectifier circuit 27 and a constant voltage circuit 28.

Now, if an accident occurs at point a of the branch line Lb ₁ and the output of the peak hold circuit 21 is a value that operates the lower limit comparator 23, one of the phase display sections 16 will be in the display state, and the current display section 25 will be in the display state. The displayed value is the short-circuit current value determined by the line impedance between the substation SS and the fault point a.

Moreover, FIG. 3B shows a second circuit configuration of the display SA. The detection outputs from the current transformers ICT ₁ to _{ICT 3} are given to the transformer 29 and converted into direct current by the rectifier circuit 30 .

This output becomes an input to level detection circuits 31 and 32 and a maximum value discrimination circuit 38. If the level detection circuit receives an input of a predetermined level or higher in any of the three phases, 1, 2, or 3, the OR circuit 35 outputs the signal and inputs the signal to the integrator circuit 36. If the signal continues for a certain period of time or longer, the output is output. arise.

This output gives a control signal to the AND circuit 33 and a sampling start signal to the peak hold circuit 39, and is further input to the integrating circuit 37 in the next stage, and after a certain period of time, an output is obtained and a sampling cancellation signal is given. , simultaneously instructs the A/D converter 40 to start conversion.

The level detector 31 outputs an output when there is an input of a predetermined level or higher, and provides an input to the AND circuit 33 . The input of this AND circuit generates an output only when the output of the integration circuit 36, the level detector 31, and the A/D conversion end signal are applied simultaneously, and this output gives an energizing signal to the phase display section 34, Displays the short circuit current passing phase.

The maximum value discrimination circuit 38 outputs the maximum value of each phase and supplies it to the peak hold circuit, and only for a time determined by the time constant of the integration circuit 37, opens the gate of the peak hold circuit and holds the maximum level within that time. is supplied to an analog-to-digital converter 40, converted into a digital value by a command from the integrating circuit 37, and supplied to a current value display section 42 via a decoder 41, thereby digitally displaying the maximum short circuit current value. This phase display section 34 and current value display section 42
is displayed for a certain period of time determined by the timer 43,
For example, it will automatically return after 3 hours.

As the operating power source for each of these circuits, as in FIG. 3A, a predetermined voltage is taken out from a pole transformer 44, and a constant voltage is supplied to each circuit via a rectifier circuit 45 and a constant voltage circuit 46.

In addition, the reason for installing the short-circuit current indicator as explained above on the distribution main line is that in recent years, remote monitoring systems for distribution substations have become commonplace, and the short-circuit current display meter has the function of collecting and displaying the short-circuit current of all distribution lines up to the control center. As it has become difficult to install short-circuit currents, on-site maintenance organizations are installing them on distribution main lines in locations that are easy to inspect, in an effort to detect short-circuit currents at an early stage. A method may be adopted in which the short-circuit current is ascertained at the power station and the short-circuit current is reported to the power distribution maintenance organization.

On the other hand, in addition to the display of the short-circuit current value on the current display section mentioned above, near the fault point a, a short-circuit current exceeding the rated load current flows through the passage indicators SI ₁₁ and SI ₁₂ on the power supply side, and the display section is activated and displays that fact. Therefore, after a short-circuit accident occurs, the display meter
The current value of SA is compared with the high-voltage line short-circuit current distribution map created in advance including branch lines Lb ₁ , Lb ₂ , Lb _{3 .} . . to determine the distance to the fault point, and the display status of the passing indicator located at that distance is determined. By investigating the
Accident points can be accurately discovered.

Referring to FIG. 4, one specific example of a high voltage line short-circuit current distribution map prepared in advance is shown. The same reference numerals as in FIG. 1 are used here to indicate the same parts as shown in FIG. According to this short-circuit current distribution map, a two-phase short-circuit current division line 2S and a three-phase short-circuit current division line 3S are shown, and the short-circuit current values in these sections are, for example, 4KA, 2KA, and 1KA, respectively.
It is shown as Therefore, the short circuit current indicator SA
The distance section to the fault point is determined based on the current display, and the overcurrent passage indicator SI located within that section confirms whether or not the overcurrent has passed. In conjunction with this determination, the accident point can be reliably detected.

As explained above, according to the exploration method of the present invention, the distance section and accident phase to the accident point are determined by the display meter installed on the distribution main line, and the display meter installed at the position corresponding to the determined distance section is The accident point is discovered based on the state of the passing indicator, and the accident point can be searched quickly and accurately.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a method for searching for a short circuit fault point according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of the electrical connection of the short circuit current indicator. FIGS. 3A and 3B are explanatory diagrams of two electric circuit configurations of the short-circuit current indicator. FIG. 4 is an explanatory diagram of a high voltage line short circuit current distribution diagram. Explanation of symbols SS...Substation, Lm...Distribution main line,
Lb ₁ , Lb ₂ , Lb ₃ ...Distribution branch line, SA...Short circuit current indicator, SI ₁₁ , SI ₁₂ , SI ₁₃ , SI ₂ , SI ₃ ...Short circuit current indicator, ICT ₁ , ICT ₂ , ICT ₃ ...Special CT (insulator with built-in current transformer), CA ₁ ...cable, MS ₁ ...current value display,
MS ₂ ...Phase discrimination display section, 10...Transformer, 11, 12
...AC amplifier circuit, 13...Level detection circuit, 14...
AND circuit, 15...OR circuit, 16...phase indicator, 1
7... Timer, 18... AND circuit, 19... Timer, 20... Rectifier circuit, 21... Peak hold circuit, 22... Voltage frequency conversion circuit, 23... Lower limit comparator, 24... Counting decoding circuit, 25... Current value display section, 26... Transformer, 27... Rectifier circuit, 28...
Constant voltage circuit, 29...Transformer, 30...Amplification and rectification circuit, 31, 32...Level detection circuit, 33...AND
Circuit, 34... Phase display section, 35... OR circuit, 36,
37... Integrating circuit, 38... Maximum value discrimination circuit, 39...
Peak hold circuit, 40...A/D conversion circuit, 4
DESCRIPTION OF SYMBOLS 1... Decoder, 42... Current value display part, 43... Timer, 44... Transformer, 45... Rectifier circuit, 46... Constant voltage circuit.

Claims (1)

[Scope of Claims] 1. A short-circuit current indicator provided on the main line of an overhead distribution line and a short-circuit current passing indicator provided on its branch line, wherein the short-circuit current indicator measures the distance from the reference point to the fault point. The short-circuit current passage indicator has a first display section that displays a short-circuit current value depending on A current distribution diagram is prepared in which short-circuit current values are calculated in advance based on line parameters according to distances of the main line and the branch line to the accident point. , when the first display unit displays the short circuit current value, determine the distance to the accident point by referring to the current distribution diagram based on the current value, and
and a short-circuit accident point detection method for an overhead power distribution line, characterized in that the fault line and its phase are identified from among the main lines or branch lines located at a distance determined based on the display state of the third display unit.