JPH04359402A - Lighting arrester - Google Patents

Abstract

PURPOSE:To obtain a lightning arrester, which provides the facilitated detection of a degradation of elements, without increasing the size thereof by connecting a thermal switch in series with a nonlinear resistor, wherein a contact of the switch opens by heat emitted from the nonlinear resistor. CONSTITUTION:In a lightning arrester with a nonlinear resistor 2 being incorporated in an insulating vessel 1, a thermal switch 3 is connected in series with the nonlinear resistor 2, wherein a contact of the resistor opens by heat emitted from the resistor. For instance, a required number of elements, each element chiefly being composed of an zinc oxide, are stacked up in the insulating vessel 1 of an insulator, and the thermal switch 3, being made of a thermal ferrite, is connected in series with the elements 2. Employed as the thermal switch 3 is a general purpose component which enters a closed state at normal temperatures, but an opened state at high temperatures of 80 to 130 deg.C, and this switch is arranged so as to be thermally connected with the elements 2. Closures are disposed on the top and bottom of the insulating vessel 1 so that the elements 2 and the thermal switch 3 are hermetically sealed therein, and the top and bottom of the lightning arrester are electrically connected with a line and the ground, respectively.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning arrester equipped with a voltage-current nonlinear resistor, and more particularly to a lightning arrester that allows easy deterioration diagnosis.

0002

2. Description of the Related Art Lightning arresters equipped with voltage-current nonlinear resistors (hereinafter referred to as elements) containing zinc oxide as a main component are widely used as overvoltage protection devices for equipment.

[0003] The elements housed in such a lightning arrester are constantly under the stress of the system voltage, and therefore tend to deteriorate when used for a long period of time. When the element deteriorates, the insulation resistance decreases, potentially leading to a ground fault, and in such a state, supply to the power system may be disrupted. Furthermore, when a lightning arrester in a power distribution system malfunctions, it is difficult to locate the faulty lightning arrester because the ground fault current is small, requiring a great deal of time and cost.

[0004] To avoid such a situation, conventionally, a lightning arrester has been used in which a device for measuring the leakage current, which increases as the element deteriorates, is connected to the lightning arrester so that the condition can be monitored.

[0005]

However, if a detection device for measuring the leakage current of the lightning arrester and determining its level is connected, the lightning arrester becomes large in size. Furthermore, in the case of a built-in lightning arrester used in a power distribution system, a detection device must also be built into the device, making installation difficult due to space constraints. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lightning arrester in which deterioration of elements can be easily detected without increasing the size of the lightning arrester. [Structure of the invention]

[0006]

[Means for Solving the Problems] In order to achieve the above object, in the present invention, in a lightning arrester in which a non-linear resistor is housed in an insulating container, a contact is made to the non-linear resistor by the heat generated by the non-linear resistor. To provide a lightning arrester characterized in that heat-sensitive switches that open are connected in series.

[0007]

[Operation] When the elements of the lightning arrester deteriorate, the leakage current increases and the temperature of the element rises. This temperature rise causes the closed heat-sensitive switch to open, causing corona discharge inside the arrester. Since electromagnetic noise is generated due to this corona discharge, this electromagnetic noise can be detected from the outside without contact.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. A required number of elements 2 whose main component is zinc oxide are stacked and housed in an insulator container 1, and a heat-sensitive switch 3 made of, for example, heat-sensitive ferrite is connected in series with the elements 2. The thermosensitive switch 3 is also thermally connected to the element 2 (indicated by a dotted line in FIG. 1). Lids are disposed on the top and bottom of the insulating container 1 to seal the element 2 and the heat-sensitive switch 3, and electrically connect the top and bottom ends of the lightning arrester to the line and the ground, respectively.

[0009] The heat-sensitive switch may be a general-purpose product that is closed at room temperature and opened at high temperatures of, for example, 80 to 130°C. The leakage current of the lightning arrester is less than a few mA during normal operation.
Even in abnormal conditions, the current is several tens of mA or less. Therefore, the heat-sensitive switch may be of a small size and a small capacity, for example, about 1 cm in diameter and 3 cm in length. Next, the effect will be explained.

When the element 2 is functioning normally, the heat-sensitive switch 3 remains closed because the heat generated from the element 2 is very small. On the other hand, as the element 2 deteriorates, leakage current increases, the element 2 generates heat, and the temperature rises. As the temperature rises, the heat-sensitive switch 3 changes from a closed state to an open state. Since the element 2 that has deteriorated and caused thermal runaway behaves as a high dielectric material with a relative permittivity of 500 to 1000, its impedance to alternating current is much larger than the impedance of the gap of the thermal switch 3. Therefore, most of the system voltage is applied to the gap of the heat-sensitive switch 3, and as shown in FIG. 2, discharge occurs every cycle when the voltage rises. Since electromagnetic noise is generated by this corona discharge, the electromagnetic noise can be easily detected using an external detection device.

According to this embodiment, the heat-sensitive switch 3 may be of small size and small capacity, and the deterioration of the element 2 can be detected from the outside without contact. The electromagnetic noise detection device may be any device that can detect noise at a certain frequency, such as a corona meter or a noise meter. In this way, deterioration diagnosis can be easily performed without increasing the size of the lightning arrester, thereby improving the space efficiency of the lightning arrester. Furthermore, early replacement of deteriorated lightning arresters becomes easier, resulting in improved supply reliability and reduced maintenance costs.

0012

As described above, according to the present invention, by connecting a heat-sensitive switch in series to a lightning arrester element, it is possible to provide a lightning arrester that can be easily diagnosed for deterioration without increasing its size.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a lightning arrester showing an embodiment of the present invention.

FIG. 2 is a diagram of voltage and current waveforms when a lightning arrester element deteriorates.

[Explanation of symbols]

1...Insulating container, 2...Element, 3...Heat-sensitive switch.

Claims (1)

[Claims] 1. A lightning arrester in which a non-linear resistor is housed in an insulating container, characterized in that a heat-sensitive switch whose contacts open due to heat generated by the non-linear resistor is connected in series to the non-linear resistor. .