JPH0119561Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a protection system for protecting communications and other electrical equipment, including power equipment, from abnormal high voltages generated by lightning strikes, etc. To provide a protection system with improved protection performance.

Generally, wireless relay stations and the like are built at high places such as mountain tops with good views from the viewpoint of radio wave propagation. Therefore, the chance of being struck by lightning is extremely high.

Although various studies have been carried out regarding lightning phenomena, its essence has not yet been fully elucidated. In addition to a direct lightning strike called a lightning strike, lightning strikes can occur when the electric charge in a thundercloud is temporarily extinguished due to discharge, for example, the electric charge of the opposite polarity to the thundercloud induced on a power transmission line becomes a free electric charge. Induced lightning is known as a type of lightning that propagates along railroad tracks as a traveling wave.

Currently, protective measures against such lightning strikes are mainly based on data based on experience and safety standards established from economic considerations.

FIG. 1 is a block diagram showing a conventional protection system for power equipment, etc. against abnormally high voltage. In the drawing, 1 is a steel tower, 2 is a lightning rod, 3 is a parabolic antenna, 4 is a waveguide, 5 is a communication device including power supply equipment, 6 is a shield transformer, 7 is a power distribution transformer, 8A and 8B are high voltage arresters, 9 is a high voltage grounding member, 10A and 10B are low voltage lightning arresters, 11 is a second class grounding member for low voltage, 12A and 12B are varistors, 13 is a lightning rod grounding member, L1 to L3 are power supply side wiring, and LA is a lightning rod side wiring. Shows the ground wiring,
Also, P is the ground point of lightning rod 2, and Q is low voltage lightning arrester 1.
Connection point between 0A and 10B ground wiring LA, S is the ground point on the secondary side of the distribution transformer 7, T is the ground point of the high voltage lightning arresters 8A and 8B, VS1 and VS2 are the distribution transformer 7 and the shield transformer 6, respectively. Surge voltages I1 to I6 entering from the power transmission line side respectively indicate abnormal currents generated by abnormally high voltages.

In a normal state in which no abnormally high voltage is generated, a high voltage such as 6600V at a commercial frequency is supplied from the wiring L1 to the primary side of the power distribution transformer 7. Then, voltage conversion is performed by this power distribution transformer 7, and 100V or 200V is applied to the secondary side.
A low voltage such as is generated. This low voltage is supplied from the wiring L2 through the shield transformer 6 and the wiring L3 to the communication device 5 including the power supply equipment to operate the device.

On the other hand, if an abnormally high voltage is generated in the high voltage side wiring L1 due to induced lightning or a direct lightning strike on a high voltage distribution line from a substation, etc., if the voltage is below a certain value, the high voltage Although the lightning arresters 8A and 8B are not operated, the surge voltage VS1 is electrostatically transferred to their secondary side through the stray capacitance of the power distribution transformer 7.

The shield layer of the shield transformer 6 acts to shield this surge voltage VS1, and the communication device 5 and the like connected to the secondary side of the shield transformer 6 are protected.

In addition, when the abnormal high voltage exceeds a certain value, the surge voltage VS1 transfers electrostatically through the distribution transformer 7, and the high voltage arresters 8A and 8B operate, causing the lightning current to flow from the high voltage grounding member 9 as shown in I1. discharged to the earth. Therefore, an increase in the ground potential due to the current I1 flowing into the high-voltage grounding member 9 enters the low-voltage wiring L2 from the grounding point S on the secondary side of the power distribution transformer 7.

Such surge voltage VS1 and the like are first shielded by the shield layer of the shield transformer 6.
Second, when the surge voltage VS1, etc. is higher than the impulse discharge starting voltage of the low-voltage arresters 10A and 10B, it is discharged by these arresters 10A and 10B and flows from the lightning rod grounding member 13 to the ground.

Furthermore, the surge voltage VS2 that has entered the shield transformer 6 is processed by the varistors 12A and 12B.
Similarly, the light is discharged from the lightning rod grounding member 13 to the ground.

Next, when the steel tower 1 or the lightning rod 2 receives a direct lightning strike, a lightning current I6 flows to the lightning rod grounding member 13. The grounding resistance of the lightning rod grounding member 13 is R.
13, the voltage V _P at the ground point P is V _P
=16×R13.

The lightning current I6 varies depending on the lightning situation, but it is extremely large, reaching several tens of KA.

Therefore, when the potential V _P of the earth point P suddenly rises temporarily and that potential is higher than the impulse discharge starting voltage of the low voltage arresters 10A and 10B, the low voltage connected from the earth point P to the primary side of the shield transformer 6 A current like I2 flows toward the lightning arresters 10A and 10B, and the second type grounding member 1 for low voltage
1 is discharged to the earth.

In this case, if the lightning current is large and the potential V _P at the ground point P exceeds the withstand capacity of the low voltage arrester 10A or 10B, the low voltage arrester will be destroyed.

Then, when the low-voltage lightning arresters 10A and 10B are destroyed, the entire potential increase at the ground point P is applied to the shield transformer 6, destroying the shield transformer 6 and the varistors 12A and 12B. There was a drawback in that the voltage was applied to the device 5, which ultimately led to a serious accident in which the communication device 5 was destroyed.

Therefore, the purpose of the protection system for power supply equipment, etc. of this invention is to solve these inconveniences in conventional protection systems and prevent accidents caused by lightning strikes by simply adding a simple circuit.

FIG. 2 is a configuration diagram showing an embodiment of the protection system for power supply equipment, etc. of this invention. The numbers in the drawings are the same as in FIG. 1, and 14A and 14B.
is a capacitor, LB is a low voltage lightning arrester 10A and 10B
The wiring LC is connected between the connection point Q with the ground wiring LA and the ground point S on the secondary side of the distribution transformer 7, and LC is the connection point between the ground point S on the secondary side of the distribution transformer 7 and the high voltage lightning arrester 8A. 8B shows the wiring connected to the ground point T, and I7 shows the current due to the abnormally high voltage flowing through the wiring LB.

As shown in FIG. 2, in the protection system for power equipment, etc. of this invention, the wiring LB connects the connection point Q between the low voltage lightning arrester and the ground wiring LA on the lightning rod side to the secondary terminal of the distribution transformer 7. Connect directly to the ground point S on the side using a conductor like the wiring LB, and connect the varistors 12A and 12B.
The feature is that capacitors 14A and 14B are connected in parallel with each other.

According to the protection system of this invention, even if lightning strikes the steel tower 1 or the lightning rod 2 and the potential of the ground point P suddenly increases, the wiring LA on the ground side of the lightning rod 2
A current I7 flows through the connection point Q to the wiring LB, and is discharged from the grounding point S on the secondary side of the distribution transformer 7 to the low-voltage type 2 grounding member 11, and the potential of the grounding point P suddenly increases. will be lowered to

Therefore, the abnormal high voltage applied to the low-voltage lightning arresters 10A and 10B is suppressed to below their withstand capacity,
Destruction of the low voltage lightning arrester is prevented. Therefore, communication equipment 5 due to lightning strikes on steel tower 1 and lightning rod 2
It is also possible to completely prevent such damage.

In addition, the ground point S on the secondary side of the power distribution transformer 7
and the ground point T of the primary side high voltage surge arresters 8A and 8B.
If the wiring LC shown by the dotted line is used to connect directly between the two and It becomes possible to lower the amount quickly.

Next, the capacitors 14A and 14B connected in parallel to the varistors 12A and 12B provided on the secondary side of the shield transformer 6 will be described.

As already explained with respect to the conventional example shown in FIG.
Electrostatic transfer like VS1, shield transformer 6
When a surge voltage enters the primary side of the communication device 5, the communication device 5 and the like are protected by the low voltage lightning arresters 10A and 10B and the shield transformer 6.

However, when the scale of induced lightning or direct lightning is very large, the surge voltage VS1 is not completely shielded by the shield transformer 6 due to electrostatic imbalance of the shield transformer 6 with respect to the ground, and the surge voltage VS1 is not completely shielded by the shield transformer 6. Invade the next side like VS2.

FIG. 3 is a waveform diagram of the surge voltage generated on the secondary side of the shield transformer 6.

As shown in FIG. 3, the surge voltage VS2 generated by electrostatic transfer in the shield transformer 6 to the secondary side contains extremely high frequency components, especially in the initial stage.

Therefore, if this component is absorbed by capacitors 14A and 14B, varistors 12A and 12B
operation can be stabilized.

FIG. 4 is a voltage waveform diagram showing a surge voltage attenuated by the varistor 12A or 12B and the capacitor 14A or 14B connected in parallel. Note that V _V indicates the operating voltage of the varistor.

Comparing this FIG. 4 with the previous FIG. 3, it can be seen that in FIG. 4 using a capacitor, there is no high frequency component especially in the initial stage, and the varistor operates stably.

As explained in detail above, in the protection system for power equipment, etc. of this invention, the shielding layer of the low-voltage lightning arrester and shield transformer, which were not connected conventionally,
A simple method is to connect the ground side connection point of the varistor etc. and the second class grounding member for low voltage using a conductor, and connect the capacitors 14A and 14B in parallel with the varistors 12A and 12B, respectively. This configuration achieves the excellent practical effect of completely preventing lightning damage to communication and other electrical equipment, including power supply equipment, caused by lightning strikes on lightning rods, steel towers, etc.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional protection system for power supply equipment, etc. against abnormal high voltage, Fig. 2 is a block diagram showing an embodiment of the protection system for power supply equipment, etc. of this invention, and Fig. 3 is a block diagram of a shield transformer. FIG. 4 is a waveform diagram of the surge voltage generated on the secondary side. FIG. 4 is a voltage waveform diagram showing the situation of the surge voltage attenuated by a varistor and a capacitor connected in parallel. In the drawing, 1 is a steel tower, 2 is a lightning rod, 3 is a parabolic antenna, 4 is a waveguide, 5 is a communication device including power supply equipment, 6 is a shield transformer, 7 is a power distribution transformer, 8A and 8B are high voltage arresters, 9 is a high voltage grounding member, 10A and 10B are low voltage lightning arresters, 11
is the second class grounding member for low voltage, 12A and 12B are the varistors, 13 is the grounding member for the lightning rod, 14A and 14B are the capacitors, LA is the grounding wire on the lightning rod side, LB is the grounding wire LA of the low voltage lightning arrester 10A and 10B. Wiring connected between the connection point Q and the ground point S on the secondary side of the power distribution transformer 7 is shown.

Claims (1)

[Scope of utility model registration request] A high-voltage lightning arrester, one end of which is connected to the primary side of the distribution transformer, a high-voltage grounding member connected to the other end of these high-voltage lightning arresters, and a low-voltage lightning arrester connected to the secondary side of the distribution transformer. A second class grounding member, a low-voltage lightning arrester with one end connected to the primary side of the shield transformer, a varistor, one end each connected to the secondary side of the shield transformer, and communication equipment including power supply equipment. an electrical device, a lightning rod, a ground member for the lightning rod, a connection between the lightning rod, the steel tower, and the ground member for the lightning rod, the other end of the low voltage lightning arrester, the shielding layer of the shield transformer, the other end of the varistor, and the In a protection system for power equipment, etc., against abnormal high voltage, which comprises ground wiring connecting between the ground terminal of an electrical device and the ground member for the lightning rod, the low voltage lightning arrester, the shielding layer of the shield transformer, the varistor, etc. A point near the connection point connected to the ground wiring is directly connected to the second type ground member for low voltage by a conductor,
A protection system for power equipment, etc., characterized in that a capacitor is connected in parallel with each of the varistors.