JPH0222604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting flash faults in power transmission towers caused by lightning strikes.

In recent years, as the demand for electricity has increased, power transmission lines have become larger and more trunk-lined, and due to social demands, power transmission routes have become limited to mountainous regions. As a result, lightning strikes are more likely to occur, and there is a concern that a single accident could lead to a large-scale power outage, making lightning protection an important issue. As one measure against lightning, a ground wire has traditionally been placed above power lines, but this serves as a lightning rod, and when a lightning strike is likely to occur,
It actively guides lightning towards it and causes it to strike. This prevents lightning from striking the power line itself.

However, since there is a limit to the grounding resistance of a steel tower, when a large lightning current flows, an abnormally high voltage is generated in the tower, and a lightning surge current flows into the power line beyond the insulation capacity of the insulator. A flashback occurs. In addition, when the shielding effect of the ground wire is not effective and the power line is struck directly by lightning, the potential of the power line increases significantly.
At this time, the insulator's insulating capacity is exceeded and a flash fault occurs, causing current to flow into the tower (earth). These flashover accidents often occur when the insulator that provides insulation is jumped over, and as a result, the insulator that comes into contact with the discharge path is often damaged. Flash accidents only last a short time, but
Once such a discharge path is created, a "follow-on current" occurs in which the current being transmitted flows into the ground along the discharge path, tripping relays at the substation and causing power outages. In addition, the time from the occurrence of follow-on current to activation of the relay (power outage) is several cycles (approximately 0.1 seconds).
That's about it.

Not all lightning strikes on power transmission lines will cause a power outage, and a power outage will only occur when the following current occurs. Therefore, in order to recover from a power outage early, it is necessary to prevent flash faults from occurring. It is necessary to detect the steel tower as soon as possible.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a detection device for a steel tower that has suffered a flash fault, as set forth in the claims, which detects a steel tower that has suffered a flash fault in a reliable and inexpensive manner.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Figure 1 shows the accidental steel tower 1 and the non-accidental steel tower 2 next to it.
The direction of follow-on flow 3 is shown. In other words, if a flash fault occurs in a specific insulator 4 of the accident tower 1, the follow-on current 3 enters the tower arm from the tower 5 and is split up and down, with some flowing into the ground through the tower pedestal, and the rest flowing into the ground through the tower pedestal. It flows from the top to ground line 6. The trailing stream 3 flowing into the ground wire 6 is further divided into left and right halves at the top of the tower, and flows into the adjacent non-accident steel tower 2.
In the non-accident steel tower 2, there are two types: one that flows from the ground wire 6 into the support 5 and flows into the ground, and the other that flows further through the ground wire 6 toward the neighboring steel tower.

Since the follow-on stream 3 is an alternating current, its polarity alternates, but what can be said about the follow-on stream 3 at the accident tower 1 and the non-accident tower 2 is that the phase of the follow-on stream 3 flowing to the ground wire 6 is such that on both sides of the tower top, While the direction is opposite in the accident steel tower 1, the direction is the same in the non-accident steel tower 2.

The phase of the trailing current 3 flowing to the column 5 between the uppermost arm 7 and the tower top is upward (towards the top) in the accidental steel tower 1, whereas it is downward (toward the ground) in the non-accidental steel tower 2.

Therefore, in the case of , it is possible to prevent an accident by determining whether the phases of the trailing stream 3 flowing to the ground wire 6 match or are almost in opposite phases on both sides of the tower top, which is the branching point of the trailing stream 3. Since the steel tower 1 and the non-accidental steel tower 2 can be distinguished, the accidental steel tower 1 can be detected.

In addition, in the case of , the 5 parts of the support near the top of the tower,
The accidental steel tower 1 can be similarly detected by determining the direction of the trailing current 3 flowing to the portion of the column 5 near the tower foot. However, in this case, since there are usually four tower legs, the subsequent flow will be divided into each tower leg.

As described above, both when determining the direction of the trailing current 3 flowing to the ground wire 6 and when determining the direction of the trailing current 3 flowing to the support column 5, the flow of trailing current 3 on both sides of the branch part where the trailing current 3 branches off when a flash fault occurs. By determining the direction of the accident steel tower 1, it is possible to detect the accidental steel tower 1.

Next, the means for determining the phase direction of the follow-on flow 3 is
The above case will be explained.

As shown in FIG. 2, one current transformer 8, 8' having the same characteristics is attached to the ground wire 6 on both sides of the head of the column 5 so as to sandwich the tower portion thereof. A load resistance R _L is connected between the output terminals A, B, a, and b of each current transformer 8, 8', and a follow-on current 3 flowing to the ground wire 6
is taken out as a secondary current to each output terminal A, B, a, b. Now, the output terminals B of each current transformer 8, 8'
If b is taken as the reference level, the waveforms of the secondary currents appearing at the output terminals A and b in the accidental tower 1 have almost opposite phases (180 degree phase difference), as shown in FIG. On the other hand, in the non-accident steel tower 2, the phases match as shown in FIG.

The follow-on current 3 mentioned above often has some direct current component superimposed on it, but basically it consists of an alternating current component at a commercial frequency of 50 or 60 Hz, and after it lasts for several cycles, it is It is shut off by the operation of . In addition, the size of the follow-on current depends on the power transmission capacity, the tower, the grounding resistance of the ground wire, etc.
It is 100A to several 10KA. In addition, the current transformer 8,
It is desirable that the core of the core 8' can be divided so that it can be easily attached around the ground wire 6.

Determination of whether the phases of the secondary currents match or do not match is determined by a determination device (circuit) using an appropriate logic IC, etc.; To prevent intrusion, malfunctions, and electrical damage, conduct the work on the ground at an appropriate distance from the tower. Therefore, the secondary current of the current transformers 8, 8' is converted into an optical signal by a light emitting diode 12 serving as a light emitting means, and an optical fiber 9 with one end facing the light emitting diode 12 is interposed to provide a light receiving means (not shown). It is desirable to transmit the information to the discriminating device 10 having the following. Figure 5 shows the above secondary current I as an optical signal i.
(See Fig. 6) and sends the signal to the discrimination device 10 via the optical fiber 9. The optical signal i is rectified and sent to the optical fiber 9 via the optical connector 13. In FIG. 5, 16 is a discharge gap element, 14 is a bidirectional Zener diode, and 15 is a current limiting resistor.

As described above, the present invention detects the direction of the follow-on current using a simple structure in which current transformers are installed on both sides of the branch part of the follow-on flow in the steel tower where the flash fault occurs, and determines the direction of the follow-on flow. By determining whether the phases of the secondary currents are the same or substantially opposite, it is possible to quickly detect an accidental tower.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the direction of the following current, FIG. 2 is a circuit diagram of the following current detection device, FIGS. 3 and 4 are output waveform diagrams of the above detection device, and FIG. 5 is a diagram of the device of the present invention. The circuit diagram, FIG. 6, is an input/output waveform diagram of FIG. The numbers used in the diagram are 1...accident tower, 2...
Non-accident steel tower, 3... Follow-up, 5... Support, 6... Ground wire, 8, 8'... Current transformer, 9... Optical fiber, 1
0...discrimination device, 12...indicates a light emitting diode.

Claims (1)

[Claims] 1. Two current transformers with the same characteristics are installed on the overhead ground wire so as to sandwich the head of the support, and the phases of the two waveforms detected by the two current transformers are 1. A detection device for a steel tower in a flash fault, characterized by comprising a discriminating device for discriminating whether the phases match or are substantially opposite in phase. 2. The detection device for a steel tower in a flash fault according to claim 1, wherein the current transformer has a light emitting means, the discrimination device has a light receiving means, and an optical fiber is interposed between the light emitting means and the light receiving means.