JPH10215506A - Structure for preventing dew condensation in enclosed distribution panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make enable prevention of dew condensation at desired places inside an enclosed distribution panel, without providing a space heater of large capacity. SOLUTION: This structure prevents dew condensation, not by raising temperature in an entire area inside an enclosed distribution panel, but by increasing the surface temperature of a molded insulator 4 supporting a charged part. To do this, a current is caused to flow from a screen electrode power supply 2 to a screen electrode 5, built in the molded insulator 4 via screen electrode switches 3. In this instance, the output voltage of the screen electrode power supply 2 is adjusted or the output current is suppressed, so that the current can be minimal for requirements. In addition, the housing of the enclosed distribution panel is constituted of metal plates using a heat insulating material, and only the molded insulator 4 among inside devices are heated by similar means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dew-prevention structure for a closed switchboard which prevents condensation from forming inside the switchboard and threatening insulation.

[0002]

2. Description of the Related Art FIG. 3 is a structural view showing a conventional example of the inside of a closed switchboard, and shows only the devices related to the present invention among the devices housed in the closed switchboard.
Since the closed switchboard 10 is generally installed outdoors, the switchboard 10 is exposed to a large temperature change, and the internal temperature fluctuates depending on whether the closed switchboard 10 is operating. Therefore, a temperature difference is generated between the outside and the inside of the closed switchboard 10, and if the water vapor contained in the air becomes saturated due to the temperature difference, moisture condenses on the low temperature portion of the internal equipment. This is so-called condensation. Moisture threatens the insulation of electrical equipment and can cause major accidents. In particular, if dew condensation occurs on the molded insulator 4 supporting the charged part such as the conductor 6, a large accident such as grounding occurs, and the operation of the closed switchboard 10 cannot be continued. It must be prevented from occurring. Therefore, conventionally, in order to raise the internal temperature of the closed switchboard 10 to such a degree that dew condensation does not occur, an electric heater is installed inside the switchboard, and the electric heater is energized as necessary.
This electric heater is called a space heater 11. In addition,
In FIG. 3, reference numeral 8 denotes a mounting plate for fixing the molded insulator 4.

[0003]

However, in order to raise the entire internal space of the closed switchboard 10 to a desired temperature, a large-capacity space heater 11 has conventionally been installed. This large-capacity space heater 11 is a closed switchboard 10
The internal temperature of the closed switchboard 10 is raised indiscriminately, including the temperature of the inside of the closed switchboard 10, including the devices that may cause dew condensation. Therefore, there is a disadvantage that the space heater 11 occupies a large space and its power consumption is increased.

In some cases, there is no space for installing the space heater 11 inside the closed switchboard 10, and when the space heater 11 is installed in a narrow space, the temperature of equipment and structures near the space heater 11 is reduced. May be higher than necessary. Accordingly, it is an object of the present invention to prevent dew condensation from occurring at a desired location inside a closed switchboard without installing a large-capacity space heater.

[0005]

In order to achieve the above object, a dew-prevention structure for a closed switchboard according to the present invention is provided by a first invention, in which a shielded electrode of a molded insulator installed inside a closed switchboard is provided. Then, a current flows from the shield electrode power supply via the shield electrode switch to generate heat in the shield electrode to prevent dew condensation.

According to a second aspect of the present invention, a cover portion of a closed switchboard is formed of a composite material in which a metal plate and a heat insulating material are bonded to each other, and a shield electrode of a molded insulator provided inside the closed switchboard is connected to a shield electrode. A current is supplied from a power supply via a shield electrode switch to generate heat in the shield electrode to prevent dew condensation. A third invention is the first invention or the second invention.
The shield electrode power supply in the invention of the present invention adjusts the output current to maintain the temperature of the shield electrode or the surface temperature of the molded insulator at a predetermined value to prevent condensation.

[0007] A fourth invention is the first invention or the second invention.
The shield electrode switch of the invention is turned on when the closed switchboard is stopped to supply current to the shield electrode to generate heat, but is turned off during operation of the closed switchboard to cut off current to the shield electrode.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The presence of moisture has a great effect on the insulation of electrical equipment. In particular, if moisture adheres to the insulator that insulates between the charged part and the earth, or the insulator that insulates between the phases of the charged part, the insulation performance is reduced, and a large accident such as grounding or short-circuit between phases may occur. It is necessary to avoid the formation of dew on the surface of these insulators.

By the way, as an insulator for supporting the charging portion,
In recent years, instead of insulators, molded insulators made of synthetic resin such as epoxy resin with good insulation performance have been frequently used to form desired shapes, and these molded insulators often contain shield electrodes. Many. The shield electrode is made of a conductive material such as a braided wire obtained by braiding an aluminum foil or a copper wire in a net shape, and one end thereof is grounded.

Therefore, in the first invention, a shield electrode power supply is connected via a shield electrode switch to the other end of the shield electrode which is housed in the molded insulator and one end of which is grounded, and a current flows. The heat generated by this current raises the surface temperature of the molded insulator, thereby avoiding the formation of dew on the surface of the molded insulator in which the insulation performance is to be avoided most in the closed switchboard.

According to a second aspect of the present invention, a cover of a closed switchboard is formed by using a material formed by laminating a metal plate and a heat insulating material,
A shield electrode power supply is connected via a shield electrode switch to a shield electrode provided inside a molded insulator installed in the closed switchboard, and a current flows. The heat generated by this current raises the surface temperature of the molded insulator, thereby avoiding the formation of dew on the molded insulator, which is the most likely to prevent the insulation performance inside the closed switchboard from deteriorating.

According to a third aspect of the present invention, in the first or second aspect, the surface temperature of the molded insulator is adjusted appropriately by appropriately adjusting the current flowing from the shield electrode power supply to the shield electrode so as to prevent dew formation on the molded insulator. Keep at the value. The fourth invention is the first invention
Alternatively, in the second invention, the shield electrode switch provided between the shield electrode power supply and the shield electrode is controlled to be turned on when the closed switchboard is stopped and turned off during operation of the closed switchboard. .

[0013]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In the circuit of the first embodiment shown in FIG. 1, a shield electrode 5 is provided inside a molded insulator 4 (a cross section is shown), and is grounded via a shield terminal 5B.
The conductor 6 penetrates the molded insulator 4, and the molded insulator 4 is attached to the mounting plate 8. Therefore, the conductor 6 serving as a charging unit and the mounting plate 8 are insulated by the molded insulator 4. If condensation forms on the surface of the molded insulator 4, the conductor 6
Then, the current leaks to the mounting plate 8 along the surface of the molded insulating material 4, resulting in a grounding accident.

Therefore, the shield electrode 5 is provided with a shield terminal 5A on the opposite side of the ground-side shield terminal 5B, and a current flows from the shield electrode power supply 2 to the shield electrode 5 via the shield electrode switch 3. Since the shield electrode 5 is made of an aluminum foil or a braided wire obtained by braiding a copper wire in a net shape, it generates heat when a current flows. If the surface temperature of the molded insulator 4 is raised by this heat generation, dew condensation can be prevented.

FIG. 2 is a structural view showing a second embodiment of the present invention, and shows a structure of a metal plate constituting a jacket of the closed switchboard 10. As shown in FIG. The jacket of the closed switchboard 10 is made of a strong, inexpensive, and easy-to-process steel plate. However, since the steel sheet has good heat conduction, the difference between the inside and outside temperatures of the closed switchboard 10 cannot be blocked. Therefore, if the jacket of the closed switchboard 10 is formed by using a plate having a sandwich structure with the heat insulating material 20 interposed between the two steel plates 21 and 22, the closed switchboard 1
The difference between the inside and outside temperatures of 0 can be cut off. Therefore, in the present invention, the shield of the closed switchboard 10 is formed using the material shown in FIG. 2, and the shield electrode 5 of the molded insulator 4 for supporting the conductor 6 housed therein is provided with the shield electrode switch 3. A heating current is supplied from the shield electrode power supply 2 via the
reference). In addition, since the jacket of the closed switchboard 10 only needs to be able to hinder heat transfer, for example, only the heat insulating material 20 is stuck to the steel plate 21, and the configuration in which the steel plate 22 is omitted may be used.

The current supplied by the shield electrode power supply 2 (see FIG. 1) does not need to be a large current as long as a temperature rise that does not cause condensation on the surface of the molded insulator 4 can be obtained.
Therefore, for example, a current limiting resistor (not shown) may be provided on the output side of the shield electrode power supply 2, and the output voltage of the shield electrode power supply 2 may be reduced to the extent that a desired current can be obtained.
Further, the outside air temperature of the closed switchboard 10 is detected by a temperature sensor (not shown), and the shield electrode 5 corresponding to the outside air temperature is detected.
Electrode power supply 2 configured to change the current supplied to the
You can also

The switch operation circuit 7 turns the shield electrode switch 3 on and off. If a signal corresponding to the operation / stop of the closed switchboard 10 is input to the switch operation circuit 7, the switchboard 10 is stopped. Only, a current for heating can be supplied to the shield electrode 5.

[0018]

According to the conventional closed switchboard, the internal temperature is raised by the space heater, so that the temperature of the electric equipment which may cause trouble due to dew condensation and the electric equipment which does not hinder the condensation can be collectively controlled. Was rising. Therefore, a large-capacity space heater is required, which not only increases the power consumption of the space heater, but also makes it difficult to secure a place for installing the space heater, and excessively increases the temperature of equipment near the space heater. However, in the present invention, it is considered that dew condensation occurs on equipment which may cause a serious accident due to dew condensation, mainly on the molded insulator supporting the charged portion, and the shield electrode provided in the molded insulator is used for the purpose. The structure is such that a large current space heater is not required, and the effect of securing the installation space and avoiding the problem of locally high temperature can be obtained. Also, the effect that the electric power required for heating is greatly reduced as compared with the related art can be obtained.

Further, if the outer cover of the closed switchboard is made of a material having a large heat insulating effect, and only the molded insulator among the electric equipment inside is heated by energizing the shield electrode as described above, the heating power can be further increased. The effect that can be reduced is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a structural diagram showing a second embodiment of the present invention.

FIG. 3 is a structural diagram showing a conventional example of the inside of a closed switchboard;

[Explanation of symbols]

 2 Shield electrode power supply 3 Shield electrode switch 4 Molded insulator 5 Shield electrode 5A Shield terminal 5B Shield terminal 6 Conductor 7 Switch operation circuit 8 Mounting plate 10 Closed switchboard 11 Space heater 20 Insulation material 21 Steel plate 22 Steel plate

Claims (4)

[Claims] 1. A closed switchboard provided with a shield electrode and provided with a molded insulator for insulating a charged portion, comprising: a shield electrode power supply for supplying a current to a shield electrode of the molded insulator; A structure for preventing condensation on a closed switchboard, comprising a shield electrode switch for opening and closing a current flowing to the shield electrode. 2. A closed switchboard in which a molded insulator for insulating a charged portion provided with a shield electrode is provided, wherein a jacket portion of the closed switchboard is made of a composite material in which a metal plate and a heat insulating material are bonded. A shield electrode power supply for supplying a current to a shield electrode of the molded insulator; and a shield electrode switch for opening and closing a current flowing from the shield electrode power supply to the shield electrode. Construction. 3. The dew-prevention structure for a closed switchboard according to claim 1, wherein said shield electrode power supply has an output so that a temperature of said shield electrode or a surface temperature of said molded insulator becomes a predetermined value. A dew-prevention structure for a closed switchboard, characterized in that the current can be adjusted. 4. The dew condensation prevention structure for a closed switchboard according to claim 1, wherein the shield electrode switch is turned on when the closed switchboard is stopped and turned off during operation. Condensation prevention structure of closed switchboard.