JPH04351415A - Ice-accretion preventer for transmission line - Google Patents

Abstract

PURPOSE:To suppress power loss by suppressing heating of a heating element when a transmission line is not subjected to ice-accretion. CONSTITUTION:A coil 4 is wound around a current transformer 3 in order to take out current for heating a heating element 5. Lead wires 4a, 4b of the coil 4 are connected with the heating element 5. A temperature variant resistor 6 is connected with the lead wires 4a, 4b. Consequently, resistance of the temperature variant resistor 6 decreases upon increase of outer air temperature and the current flowing into the resistor 6 increases whereas the current flowing into the heating element 5 decreases.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an ice-and-snow prevention device in which a heating element is attached to an electric wire and the generated heat is used to melt and fall ice and snow on the electric wire.

0002

2. Description of the Related Art It is known that when there is ice and snow on overhead power transmission lines, if it sticks out like a wing due to wind and snow, it can cause sleet jumping or galloping, which can lead to serious accidents.

On the other hand, depending on the quality of the snow, the snow may rotate and grow around the outer periphery of the electric wire and fall as a snow mass, damaging structures and crops beneath the wire. For example, excessive tension may cause wire breakage, or in the worst case scenario, it may even cause the tower to collapse.

[0004] For this reason, many proposals and attempts have been made to prevent ice and snow from accreting on power transmission lines. However, the reality is that a countermeasure that is effective for all types of snow has not yet been found.

[0005] As shown in Fig. 5, the snow accretion prevention measure by attaching rings 2, 2 at predetermined intervals around the outer circumference of the power transmission line 1 is considered to be relatively reliable among the above proposals. This has been implemented in several actual intervals.

[0006] The original theory of this proposal is that snow is like electric wire 1.
Since the snow should move in the longitudinal direction of the wire 1 along the twisted grooves formed on the outer periphery of the wire 1 as it rotates and grows around the wire 1, installing the ring 2 will prevent the snow from moving. This would prevent it from falling, and it would eventually fall under its own weight.

However, according to the results of field experiments in which ring 2 was actually attached to electric wire 1 in a snowy region and actual observations, it was extremely rare for snowflakes to slide along the twisted grooves; It has been found that it is unreasonable to expect the above-mentioned prevention of icing and snow by installing this.

[0008]

Since it has been confirmed that the ring 2 cannot be expected to prevent the formation of ice and snow, a device as shown in FIG. 2 has been proposed and put into practical use.

As shown in the figure, a current transformer (preferably a split type) 3 is attached to the power transmission line 1, a heating element 5 is connected to the coil 4 as shown in the figure, and the heating element 5 is connected to the wire. It is installed by winding it in the longitudinal direction, and the coil 4 wound around the current transformer
The electric current generated according to the number of turns is used as a power source to cause the heating element 5 to generate heat and melt the snow.If the necessary amount of heat is supplied, ice and snow can be reliably prevented regardless of the snow quality.

However, in the device shown in FIG. 2, the current generated by the current transformer 3 is supplied to the heating element 5 throughout the year, and heat is generated even in the summer, which has nothing to do with ice and snow, for example. As a result, the temperature of the wire increases more than necessary or the power loss increases.

[0011] An object of the present invention is to prevent current from flowing through the heating element in the above-mentioned device except when the outside temperature is low such as when there is snowfall, thereby greatly reducing the temperature rise of the electric wires and unnecessary power loss. The purpose of this invention is to provide an ice and snow prevention device that can reduce the amount of ice and snow.

0012

[Means for Solving the Problems] The present invention provides a method for attaching a current transformer to a power transmission line, and installing a heating element by winding or the like around the outer periphery of the transmission line in the longitudinal direction, and using the current transformer as a power source for the heating element. In a device configured to generate electricity to melt and remove ice and snow on electric wires, a switch that can detect the outside temperature is installed, and when the outside temperature is higher than a predetermined temperature, the switch is activated to cause the heating element to melt. The first point is that the current flow is stopped, and when the temperature is high, the resistance value is low and the temperature is low. The second point is to connect a resistor whose resistance value increases as the temperature decreases, and it is preferable that such a resistor be a thermistor whose resistance value is high until the temperature approaches room temperature and whose resistance value decreases rapidly when the temperature drops below room temperature. It uses semiconductor resistors such as

[0013]

[Function] If you install a switch that senses the temperature and activates when the outside temperature becomes higher than the low temperature that might cause snowfall, the heating element can be activated as mentioned above even though the outside temperature is high. If there is no risk of the current being energized, and if the temperature is above room temperature in parallel to the lead wire connecting the current transformer and the heating element,
Connect a resistor in parallel to the lead wire, which has a very low resistance value and has a characteristic that its resistance value increases rapidly when the outside temperature becomes much lower than room temperature to the point where snowfall is likely to occur. For example, when the outside temperature is high, current flows only to the resistor side with a low resistance value and does not flow to the heating element side, but when the outside temperature becomes very low, the resistance value of the resistors installed in parallel decreases. Since the current increases rapidly, the current does not flow through the resistor but instead flows through the heating element, and the desired heat generation phenomenon begins, thereby exerting the effect of preventing icing and snow formation.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing an embodiment in which an ice and snow prevention device according to the present invention is attached to a power transmission line 1.

A coil 4 is wound N times around the current transformer 3 in order to extract enough current to heat the heating element 5 to the temperature required for snow melting. , 4b are taken out and connected to the heating element 5, respectively, as shown in the figure.

[0017] If a switch capable of sensing the outside temperature is attached to either the lead wire 4a or 4b, and when the outside temperature is higher than a predetermined temperature, the switch is activated and the electricity to the heating element is stopped. By simply setting the switch operating temperature, unnecessary energization to the heating element 5 is cut off when the outside temperature is higher than the set temperature.

However, since such a highly sensitive switch is surprisingly expensive, a similar effect may be achieved using a resistor as described below.

In FIG. 1, 6 is a resistor whose resistance value changes depending on the temperature, which is connected in parallel between lead wires 4a and 4b for such purpose. The resistor 6 is not particularly selected as long as its resistance value changes greatly depending on the outside temperature, but specifically, it is preferable to use a semiconductor resistor such as a thermistor.

FIG. 3 shows the resistance vs. temperature when a thermistor is used as the resistor 6 and the thermistor is made of material, shape, and configuration such that its resistance value is equal to the resistance value of the heating element 5 at 10°C. This shows the characteristic curve. As shown in the figure, when the outside temperature becomes higher than 10° C., the resistance value decreases rapidly, but when the outside temperature becomes lower than that, the resistance value increases rapidly.

FIG. 4 shows an equivalent circuit of the icing and snow prevention device according to the present invention having the configuration shown in FIG.

If the current flowing through the power transmission line 1 is I1, the current obtained by the current transformer 3 is equal to the number of turns N of the coil 4.
It is determined by the number of turns N of the coil, i=I1
/N current is obtained. Therefore, in FIG. 1, the number of turns N of the coil 4 may be selected so that the electric current i capable of melting snow can be obtained by heating the heating element 5 as described above.

When the temperature reaches a low temperature (10° C. or less) at which icing and snow formation occurs, the resistance R1 of the thermistor 6 increases rapidly and becomes much larger than the resistance R2 of the heating element 5, as shown in FIG. 4(a). It has a resistance, R1 > R2, and the current i1 to the thermistor 6 becomes 0. Most of the current I1 /N that uses the current transformer as a power source flows to the heating element 5 side, and the current i2 of the heating element = I1 /N to generate electricity and melt the ice and snow to fall and remove it, thereby preventing ice and snow from accumulating on the power transmission line 1.

On the other hand, if the outside temperature rises and reaches a temperature of 10° C. or higher, where there is no risk of freezing or snow, the resistance of the thermistor 6 will decrease.
As shown in FIG. 3, it decreases rapidly and becomes R1 < R2, so that most of the current i of the current transformer 3 flows to the thermistor 6 side, and a current i i1 comes to flow to the thermist 6 side. As a result, the current i2 0 of the heating element 5
The heat generation will then stop.

On the other hand, the voltage V generated by the transformer 3 is determined by the product of the load resistance and I1/N, as shown in equation 1.

[0026]

[Math 1]

[0027] Note that I1, N, R1, R mentioned here
2, the symbols used in the explanation in FIG. 4 are applied as they are.

Since the current transformer 3 supplies a constant current, the generated voltage is determined by the load resistance, and at high temperatures the load resistance is close to the low resistance of the thermist 6 as explained earlier with reference to FIG. 4(b). Therefore, the voltage generated by the current transformer 3 becomes much lower than when the temperature is low. Therefore, by stopping the heat generation of the heating element 5, power loss in the power transmission line can be greatly reduced.

[0029]

[Effects of the Invention] As described above, according to the present invention, under conditions of high outside temperature other than during snowfall, the heating element stops generating heat,
Since power loss can be reduced and the voltage generated by the current transformer is also lower while heat generation is stopped, the life of the current transformer can be extended, and long-term reliability can be ensured.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing how a device according to the present invention is attached to a power transmission line.

FIG. 2 is an explanatory diagram showing how a conventional device is installed.

FIG. 3 is a diagram showing an example of a resistance-temperature characteristic curve of a thermistor used in the present invention.

4(a) and (b) are equivalent circuit diagrams for explaining the operation of the device according to the present invention shown in FIG. 1; FIG.

FIG. 5 is an explanatory sketch showing a conventional ice-and-snow prevention type electric wire in which a ring is attached to the electric wire.

[Explanation of symbols]

1 Power transmission line 3 Current transformer 4 Coil 4a, 4b Lead wire 5 Heating element

Claims (3)

[Claims] Claim 1: A current transformer is attached to a power transmission line, and a heating element is installed by winding around the longitudinal outer circumference of the transmission line, and the current transformer is used as a power source to energize the heating element and generate heat to form ice and snow on the electric wire. A device configured to melt and remove heat-generating elements is equipped with a switch that can sense the outside temperature, and is configured so that when the outside temperature is higher than a predetermined temperature, the switch is activated and the electricity to the heating element is stopped. A power transmission line ice and snow prevention device. 2. A current transformer is attached to a power transmission line, and a heating element is installed by winding around the longitudinal outer circumference of the transmission line, and the current transformer is used as a power source to cause the heating element to be energized and generate heat to form ice and snow on the electric wire. In the apparatus configured to melt and remove the heat generating element, a resistor is inserted in parallel between the lead wires connected to the heating element, and the resistance value is low when the temperature is high and the resistance value is high when the temperature is low. A power transmission line ice and snow prevention device. 3. The power transmission line icing and snow prevention device according to claim 2, wherein the resistor is a semiconductor resistor such as a thermistor, which has a high resistance value at low temperatures and rapidly decreases near room temperature.