JPH0729712Y2 - Surge protector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a surge protection device applied to protect electrical equipment connected to a line from high voltage surge such as lightning.

[Prior Art] FIG. 3 is a diagram showing an example of a conventional surge protection device for protecting electric equipment such as a communication device connected to a line from a high voltage surge such as lightning. In FIG. 3, 31 is a single ground 35
Line side security device, 32 is a power supply side security device that is independently grounded 36, 33 is an electric device such as a communication device that is independently grounded 37, and this electric device 33 is a line side security device 31 and a power supply side It is connected between the line 34 and the power source through the security device 32. A high-voltage surge such as lightning that enters through the line 34 or the like is discharged to the ground 38 through the ground 35 by the operation of the line-side security device 31, so the electric device 33 is protected from a high-voltage surge such as lightning.

However, in FIG. 3, when the line-side protection device 31 operates due to a high voltage surge such as lightning and a current flows into the ground 35, the ground potential of the line-side protection device 31 rises (V = i × R).
Therefore, the line 34 has this rising potential and the line side protection device 31
Is applied to the residual voltage of. It should be noted that i is a current flowing into the ground 35, and R is a ground resistance of the ground 35. Therefore, the voltage of the above sum is applied between the line side protection device 31 and the electric device 33 grounded to the ground 37 different from the line side security device 31. When the ground resistance R is high and the lightning surge current (inflow current i) is large, the rising voltage of the ground potential is also high, and the line side protection device 31
There is a case where a high voltage is applied between the ground 35 and an electric device 33 connected to another ground 37, and the electric device 33 cannot be protected. In this way, when grounding at two or more points, it is necessary for the electric device to have sufficient withstand voltage against the potential difference between the ground electrodes.

In order to solve the above-mentioned problems, it is also known that all grounds are single-point grounds, as shown in FIG. 4, for example. In FIG. 4, the same parts as those shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. 39 indicates one-point grounding. In FIG. 4, even if the grounding of the line-side protection device 31 rises in potential due to an abnormal voltage, the single-point grounding 39 causes electrical equipment to operate.
Since 31 also rises to the same potential, no voltage is applied between the line 34 and the electric device 31.

[Problems to be Solved by the Invention] As described above, when the line side protection device, the power supply side protection device and the electric device are individually grounded as shown in FIG. There is a problem that the electric potential difference increases and it becomes impossible to protect the electric equipment, and the electric equipment needs to have a sufficient withstand voltage.

Further, as shown in FIG. 4, if all the grounds are grounded at one point, the above problems can be solved,
The single-point grounding has a problem that the electric equipment is easily affected by noise from the power supply side or a ground fault, or that the single-point grounding may be inconvenient for facility operation.

An object of the present invention is to provide a surge protection device capable of solving the above conventional problems.

[Means for Solving the Problems] A surge protection device according to the present invention is (1) an electric device connected between a line and a power supply via a line-side protection device and a power-supply-side protection device that are each grounded independently. In the surge protection device, the ground terminal of the electric device is connected to the ground terminal of the line-side protection device for single-point grounding, and when there is an abnormality between the ground terminals of the line-side protection device and the power-side protection device. It is characterized in that a protection element is connected to make the potential between the respective grounds equal to each other.

(2) In a surge protector for an electric device grounded between a line and a power supply via a line-side security device and a power-source-side security device, which are grounded independently of each other, the ground terminal of a casing of the electric device is Connecting to the ground terminal of the line-side safety device for single-point grounding, and conducting between the ground terminals of the line-side safety device and the power-source side safety device in an abnormal condition to make the potential between the grounds equal 1 is connected, and a second protection element is connected between the electric circuit of the electric device and the grounding terminal of the casing in an abnormal state to make the potential between the grounds equal. It is characterized by

[Operation] According to the present invention, (1) In the case where the ground terminal of the electric device is connected to the ground terminal of the line-side security device for single-point grounding, the ground terminal of the line-side security device and the power-side security device By inserting a protective element that conducts at the time of abnormality, for example, a lightning arrester between the grounding terminal and discharging the lightning arrester at the time of abnormality to make the potential between the grounds equal, it is possible to eliminate the above conventional problems. it can.

(2) If the ground terminal of the casing of the electric device is connected to the ground terminal of the line-side safety device to make a single-point ground, it is between the ground terminal of the line-side protective device and the ground terminal of the power-side protective device. A first protection element that conducts in an abnormal state, for example, a first lightning arrester is inserted, and a second protection element that conducts in an abnormal state between the electric circuit of the electric device and the ground terminal of the housing, for example, , By inserting the second lightning arrester,
At the time of abnormality, the first and second lightning arresters are discharged to make the potential between the grounds equal, thereby eliminating the above-mentioned conventional problems.

(3) Since all grounds are not grounded by one-point grounding, it is possible to prevent electric equipment from being affected by noise and ground fault caused by one-point grounding, and to eliminate conventional disadvantages in facility operation.

[Embodiment] FIG. 1 is a view showing an embodiment of the present invention, in which 1 is a line side protection device which is independently grounded 5, 2 is a power supply side security device which is independently grounded 6, and 3 is a ground terminal Reference numeral 7 is an electric device such as a communication device which is grounded 5 by a one-point ground together with the ground terminal of the trackside security device 1. The electric device 3 is connected to the line 4 and the power source via the trackside security device 1 and the power supply side security device 2. Is connected between and. 8 is a ground, 10 is a protective element connected between the ground terminal of the line-side protection device 1 and the ground terminal of the power-supply-side protection device 2, and conducting in an abnormal state to equalize the potential between the ground terminals, for example, It is a lightning arrester.

In FIG. 1, an abnormal voltage that enters the electric device 3 from the line 4 side or the power supply side is grounded 5 or ground 6 by the line side security device 1 or the power supply side security device 2.
As a result, the electric device 3 is discharged to the ground 8, so that the electric device 3 is protected from surges such as these abnormal voltages. In this case, since the electric device 3 and the power supply side protection device 2 are grounded separately, a potential difference occurs between the ground terminal 7 of the electric device 3 and the ground terminal of the power supply side protection device 2 when a surge occurs. However, when this potential difference exceeds a predetermined value, the lightning arrester 10 discharges and makes each of these ground terminals equipotential, so that the electric device 3 can be protected from this potential difference.

FIG. 2 is a diagram showing another embodiment of the present invention, in which the same parts as those shown in FIG.

2 is different from that shown in FIG.
The electric device shown in FIG. 2 has an electric circuit 9 and a housing 3'that accommodates the electric circuit 9. Between the electric circuit 9 and the ground terminal of the housing 3 ', there is continuity in an abnormal state and each ground terminal is connected. A protection element for making the potential between them equipotential, for example, a lightning arrester 11 is connected, and other configurations and operations are the same as those described with reference to FIG.

The embodiment shown in FIG. 2 is an embodiment in which the line side protection device 1, the power supply side protection device 2, the electric circuit 9 of the electric device, and the ground terminals of the housing 3'are not configured to have the same potential, respectively. Is. In this case, when a surge occurs, a potential difference is generated between the ground terminals, but when the potential difference exceeds a predetermined value, the lightning arresters 10 and 11 are discharged and the ground terminals are set to the same potential, respectively. The electric circuit 9 of the electric device can be protected from these potential differences.

In addition, in FIG. 1 and FIG. 2, lightning arresters 10 and 11
Since they do not operate normally and each ground terminal is grounded, it is possible to eliminate the inconvenience in facility operation and reduce the influence of noise or the like generated between each device.

[Advantages of the Invention] According to the present invention, in the event of an abnormality, the ground terminals can be electrically connected to make them equipotential, so that it is possible to protect electrical equipment when the ground potential rises due to the occurrence of a surge. Since it is not necessary to ground all the grounding terminals by one-point grounding as in the conventional case, it is possible to prevent the electric equipment from being affected by noise, ground fault, etc. due to one-point grounding. In addition, the inconvenience of facility operation associated with single-point grounding is eliminated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention, FIG. 2 is a diagram showing a configuration of another embodiment of the present invention, FIG. 3 and FIG.
Each of the figures is a diagram showing a conventional example. DESCRIPTION OF SYMBOLS 1 ... Line side security device, 2 ... Power source side security device, 3 ... Electrical equipment, 3 '... Housing, 9 ... Electrical circuit, 10, 11 ... Lightning arrester.

Claims (2)

[Scope of utility model registration request] 1. A surge protection device for an electric device connected between a line and a power source via a line-side security device and a power-source-side security device, which are grounded independently of each other, and a ground terminal of the electric device is connected to the line. The protective element is connected to the ground terminal of the side protection device for single-point grounding, and is electrically connected between the ground terminals of the line-side protection device and the power-side protection device in an abnormal state to make the potential between the grounds equipotential. Surge protection device characterized by connecting with. 2. A surge protection device for an electric device connected between a line and a power supply via a line-side protection device and a power-supply-side protection device, which are grounded independently, respectively, in a ground terminal of a casing of the electric device. Is connected to the ground terminal of the line-side safety device to establish a single-point ground, and the line-side protective device and the power-side protective device are electrically connected to each other in an abnormal state between the ground terminals to make the potential between the grounds equal. A second protection element which is connected to the first protection element and which is electrically connected between the electric circuit of the electric device and the ground terminal of the casing in an abnormal state to make the potential between the grounds equal. A surge protector characterized by being connected.