JPH03153007A - Snow-melting apparatus utilizing waste heat of oil-filled electric apparatus - Google Patents

Abstract

PURPOSE:To melt snow on the surface of a road without using a fuel or a burning installation by a constitution wherein a waste heat of an oil-filled electric apparatus such as a transformer or the like is guided, through a heat exchanger, to a heat-radiating means for snow-melting use which has been buried and installed under the surface of the road and it is discharged to the surface of the road. CONSTITUTION:A radiator circulation system is constituted of the following route: a transformer tank 1 housing a transformer main body e.g. a tank 10 an outgoing oil-conducting pipe 11 a radiator 13 a non-return valve 14 a return oil-conducting pipe 12 the tank 10. An insulating oil is circulated by natural convection. A primary fluid circulation system is constituted of the following: the tank 10 the outgoing oil-conducting pipe 11 a pipe 16 a primary flow passage 15a of a heat exchanger 15 a pipe 17 a pump 3 a pipe 19 the return oil-conducting pipe 12 the tank 10. The oil is circulated forcibly by means of the pump 3. At this time, a flow of the radiator circulation system is shut off. When a pump 4 is operated, a secondary fluid flows in the following 1 i route: the pump 4 a pipe 22 branch pipes Pa1 to Pan valves (Va1...Van) heat-radiating means (M1...Mn) for snow-melting use valves (Vb1...Vbn) branch pipes Pb1 to Pbn a pipe 23 a secondary flow passage 15b of the heat exchanger 15 the secondary fluid pump 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a snow melting device that utilizes waste heat from oil-filled electrical equipment such as oil-filled transformers and oil-filled paddles.

[Conventional technology] In electrical facilities such as substations installed in snowy areas,
If there is snow on the roads within the facility, it will hinder the movement of personnel and inspection equipment during maintenance inspections and accident recovery work. Therefore, it is necessary to perform snow removal work, but it is troublesome to perform snow removal work every time a periodic inspection is performed. Particularly in the event of an emergency such as an accident, it is necessary to carry out recovery in the shortest possible time, but if snow removal is performed prior to recovery work, it will take a long time for recovery to occur, causing inconvenience. Therefore, in electrical facilities such as substations, it is preferable to keep roads cleared of snow at all times. Generally, methods for removing snow include manual methods and methods using snowplows, but these methods require a large number of workers, take a long time, and are inefficient. Especially these days, most of the substations are unmanned, so these snow removal methods cannot be adopted.

Therefore, in order to solve these problems, the installation of snow melting devices in electrical facilities such as substations to prevent snow from accumulating on the roads is being considered.

Snow melting devices are of the heating wire type, which heats the road surface and melts snow by burying a resistance heating wire under the road surface and energizing the resistance heating wire, and the other uses a heated fluid (usually a mixture of water and antifreeze). A fluid heating system that melts snow by burying a snow-melting heat dissipation means under the road surface and dissipating the heat of the fluid passing through the internal flow channel of the heat dissipation means into the ground. There is also known a water sprinkling method that melts snow by spraying water on the road.

[Problem to be solved by the invention] Of the above methods, the most commonly adopted method for melting snow on roads is the heating wire method, but this method requires a considerable amount of electricity and is therefore not maintained. Expenses will increase. The benefits of snow melting are widespread on arterial roads with heavy vehicle traffic and on sidewalks with many passersby, so cost balance can be maintained even if the heating line method, which has high maintenance costs, is adopted, but substations In areas with extremely low traffic volume, such as hallways within the campus,
Snow melting methods are unsuitable because of their high maintenance costs.

In addition, conventional snow melting systems using fluid heating systems use boilers that use petroleum-based fuel to heat the fluid, which increases maintenance costs and makes them unsuitable for snow melting systems on roads with low traffic volume. there were.

Furthermore, sprinkler-type snow melting equipment often requires energy for heating, as it is necessary to heat the water to a certain degree before sprinkling water, unless underground water at a temperature that allows snow melting can be used directly. , high maintenance costs are inevitable. In addition, sprinkler-type snow melting equipment sprinkles a large amount of water on roads, so it is not only unsuitable for roads that are mainly used for pedestrian traffic, such as roads inside substations, but also in areas with severe cold. This method cannot be adopted because the water that has been drained would freeze on the road surface and be dangerous.

By the way, electrical facilities such as substations are equipped with oil-filled electrical equipment such as oil-filled transformers and oil-filled paddles, and these electrical equipment constantly generate heat.

In order to operate electrical equipment without trouble, it is necessary to dissipate the heat generated to the outside and maintain the temperature of the equipment below a predetermined value. Conventionally, waste heat from these devices was discarded into the outside air through a radiator, but in recent years various proposals have been made for effectively utilizing this waste heat.

For example, Japanese Unexamined Patent Publication No. 60-62103 discloses a proposal to utilize waste heat from oil-filled electrical equipment for hot water supply equipment. Furthermore, Japanese Patent Laid-Open No. 59-80916 proposes a method of recovering waste heat from a transformer or the like via a heat pump and using it as a heat source for an absorption refrigerator. Furthermore, in April 1989, the monthly magazine OHM published by Ohmsha was published in the April 1989 issue (V
OL, 76/No. 4) i: indicates that waste heat from transformers and reactors is used as hot water in the cooling system of electrical equipment in underground substations.

However, all of the previously proposed waste heat utilization from oil-filled electrical equipment requires that the hot water supply equipment, air conditioning area, etc. be located near the transformer, and its application is limited to transformers installed inside buildings in urban areas. . Therefore, conventionally proposed methods of utilizing waste heat from electrical equipment cannot be applied to electrical equipment in electrical facilities installed in unmanned substations and the like.

Furthermore, because oil-filled electrical equipment such as transformers must maintain high reliability over long periods of time, the upper limit of the allowable temperature rise of insulating oil is set at a relatively low temperature of around 55°C. There is. Therefore, even if waste heat from a transformer or the like is supplied to a water heater, hot water at a temperature that high cannot be obtained. Moreover, the temperature of electrical equipment is not constant, but fluctuates significantly as the load fluctuates, so equipment that needs to obtain a temperature within a certain range, such as water heaters and air conditioners, is a waste of oil-filled electrical equipment. It is not necessarily suitable as a device that utilizes heat.

The object of the present invention is to provide a snow melting device that utilizes the waste heat of oil-filled electrical equipment, which works ideally as a consumption source for effectively utilizing the waste heat of oil-filled electrical equipment, and which enables continued operation with low maintenance costs. It is about providing.

[Means for Solving the Problems] Appropriate as a device that utilizes waste heat from oil-filled electrical equipment is a device that has a relatively low operating temperature and is not affected by large temperature fluctuations. Snow melting equipment does not require very high temperatures and can tolerate large temperature fluctuations, making it an ideal source of waste heat consumption for oil-filled electrical equipment. Furthermore, when using waste heat from oil-filled electrical equipment, consideration must be given to not impairing the reliability of the electrical equipment.

The present invention focuses on these points and provides a snow melting device that utilizes waste heat from oil-filled electrical equipment. A heat exchanger having a secondary flow path for flowing heat exchange between both flow paths, and a primary fluid connected in series to the primary flow path and the secondary flow path of the heat exchanger, respectively. a pump and a secondary fluid pump, and a second fluid having an internal flow path for passing the secondary fluid and passing through the internal flow path.
The snow melting heat dissipation means dissipates the heat of the next fluid to the outside.

Both ends of the series circuit between the primary flow path of the heat exchanger and the primary fluid pump are connected to the tank of the oil-filled electrical equipment equipped with a radiator, so that when the primary fluid pump is operated, the inside of the tank of the oil-filled electrical equipment is A primary fluid circulation system is configured to circulate insulating oil through the primary flow path of the heat exchanger.

The heat radiating means for snow melting is connected to the secondary flow path of the heat exchanger via a secondary fluid pump, and the heat radiating means for snow melting is connected to the secondary flow path and the secondary flow path of the heat exchanger.
A secondary fluid circulation system is constituted by the secondary fluid pump.

A valve that prevents backflow of insulating oil within the radiator is connected in series to the radiator of the oil-filled electrical equipment, and a series circuit between the primary flow path of the heat exchanger and the primary fluid pump is connected in series to the radiator of the oil-filled electrical equipment. connected in parallel to the series circuit of the valve and the valve.

A plurality of the snow melting heat radiating means are usually provided, and the plurality of snow melting heat radiating means are connected in parallel to each other.

As the valve connected to the radiator, it is preferable to use a check valve that automatically closes when the pressure on the inlet side becomes lower than the pressure on the outlet side.
The solenoid valve may be closed when the primary fluid pump is operated.

As the secondary fluid, a mixture of water and antifreeze may be used.

When automatically controlling the above-mentioned primary fluid pump and secondary fluid pump, as shown in FIG. A snowfall detector 2 for detecting the presence or absence of snowfall, and a control device 5 for controlling the primary fluid pump 3 and the secondary fluid pump 4 using the oil temperature detected by these detectors and the presence or absence of snowfall as control conditions are provided.

The control device 5 includes a primary fluid pump control means 6 and a secondary fluid pump control means 7. Here, the primary fluid pump control means 6 operates the primary fluid pump when the oil temperature detected by the oil temperature detector 1 is less than the set maximum temperature set lower than the allowable upper limit value, and the oil temperature is increased. The primary fluid pump is controlled to stop the primary fluid pump when the temperature exceeds a set maximum temperature. Further, the secondary fluid pump control means 7 operates the secondary fluid pump when snowfall is detected by the snowfall detector and the oil temperature is less than the set maximum temperature, so that the oil temperature becomes equal to or higher than the set maximum temperature. When snowfall is not detected, the secondary fluid pump is operated to stop the oil when the oil temperature reaches a predetermined temperature range that is lower than the set maximum temperature. The secondary fluid pump is stopped when the temperature falls below a predetermined temperature set on the lower side of the warm temperature range, and the secondary fluid pump is stopped when the oil temperature reaches or exceeds the set maximum temperature with no snowfall detected. The secondary fluid pump is controlled to stop operation of the fluid pump.

[Function] In the above device, when the primary fluid pump is stopped, insulating oil circulates from the tank of the electrical equipment through the radiator and backflow prevention valve, and the heat of the insulating oil is dissipated through the radiator. be done. This is no different from the normal operating condition of electrical equipment.

When the primary fluid pump is operated, the insulating oil in the tank of the electrical equipment flows through the primary flow path of the heat exchanger and the primary fluid pump. At this time, the valve connected in series to the radiator is closed, so the insulating oil does not flow inside the radiator, and the cooling effect of the insulating oil by the radiator stops. When the secondary fluid pump is operated while the primary fluid pump is operating, heat exchange occurs between the primary fluid (insulating oil) and the secondary fluid, cooling the insulating oil and Next, the temperature of the fluid is increased. Since the secondary fluid flows through the snow melting means, heat is radiated from the snow melting means, and if there is snow, the snow is melted.

Snow melting means is installed under the road surface, and when there is no snow,
When the secondary fluid pump and the secondary fluid pump are operated, the heat of the secondary fluid will be dissipated into the ground through the snow melting means. If this state continues, heat will accumulate in the ground beneath the road surface, allowing snow to melt quickly in the event of snowfall.

When the primary fluid pump is operating and the secondary fluid pump is stopped, there is almost no heat exchange between the primary fluid and the secondary fluid, and at this time, the insulating oil is not cooled by the radiator. Therefore, the insulating oil is hardly cooled and circulates through a circulation system consisting of an electrical equipment tank, a heat exchanger, and a primary fluid pump. In this state, heat storage in oil operation occurs, and the heat generated from the electrical equipment body is stored in the insulating oil. When the temperature of the insulating oil is low, performing this kind of thermal storage operation in oil in preparation for snow melting will raise the temperature of the insulating oil and store thermal energy for snow melting in case it snows. be able to. In this case, it is natural that it is necessary to prevent the temperature of the insulating oil from exceeding the allowable upper limit temperature of the electrical equipment. In reality, it is preferable to perform this heat storage operation only during the snowy season and when the temperature of the insulating oil of the electrical equipment is considerably lower than the allowable upper limit temperature (below the set temperature).

In addition, if a control device is installed that controls the primary fluid pump and secondary fluid pump using two control conditions: oil temperature and the presence or absence of snow, each of the above operations will be automatically selected depending on the situation at that time. can do.

That is, when there is snowfall, both the primary fluid pump and the secondary fluid pump are operated to melt the snow, and when there is no snowfall, the secondary fluid pump is operated or stopped depending on the oil temperature. When there is no snowfall and the oil temperature is lower than the set maximum temperature, the primary fluid pump is operated. When the oil temperature is within a predetermined temperature range that is lower than the set maximum temperature, the secondary fluid pump is operated together with the primary fluid pump, and an underground heat storage operation is performed in which heat is stored underground. When the oil temperature falls below a preset temperature range, the secondary fluid pump is stopped and only the primary fluid pump is operated to store heat in the insulating oil in the electrical equipment tank. will be held.

Furthermore, regardless of whether or not there is snowfall, when the oil temperature exceeds the set maximum temperature, both the primary fluid pump and the secondary fluid pump are stopped, and the electrical equipment is operated normally.

In this way, if you switch to cooling using a reliable radiator when the oil temperature exceeds the set maximum temperature and operate the electrical equipment, the oil temperature can be reliably lowered. The reliability of the equipment will not be compromised in any way.

[Example] The present invention will be described in detail below with reference to the accompanying drawings.

The electrical equipment used as a heat source in the present invention may be any oil-filled electrical equipment such as an oil-filled transformer or an oil-filled paddle, but in the following description, it is assumed that the electrical equipment used as a heat source is a transformer.

FIG. 1 schematically shows an embodiment of the present invention, in which reference numeral 10 denotes a transformer tank containing a transformer main body (not shown). A sending oil guide pipe 11 and a return oil guiding pipe 12 are drawn out from the upper and lower parts of the transformer tank 10, respectively, and one end of a radiator 13 is connected to the sending oil guide pipe 11. The other end of the radiator 13 is connected to the return oil pipe 12 via a check valve 14 . In this example, tank 10 → delivery oil pipe 11 → radiator 13 → check valve 14 → return oil pipe 12
→The path of the tank 10 constitutes a radiator circulation system. Circulation of the insulating oil in this system is performed by natural convection of the insulating oil caused by the temperature difference between the upper and lower sides of the radiator 13.

15 is a heat exchanger having a primary flow path 15a and a secondary flow path 15b, and one end of the primary flow path 15a of this heat exchanger is connected to the pipe 1.
6 and is connected to the delivery oil guide pipe 11 through the primary flow path 15a.
The other end is connected to the inlet side of the primary fluid pump 3 through a pipe 17. The outlet side of the primary fluid pump 3 is the piping 19
It is connected to the return oil pipe 12 through. In this example, tank 10 → oil delivery pipe 11 → piping 16 → heat exchanger 15
The primary flow path 15a → piping 17 → primary fluid pump 3 → piping 19 → return oil pipe 12 → tank 10 constitutes a primary fluid circulation system using insulating oil as the primary fluid. The circulation of the insulating oil in this circulation system is forced circulation by the pump 3.

The check valve 14 is a swing-type check valve that opens and closes based on the relationship between gravity and back pressure acting on a valve body (not shown), and normally opens due to the force of gravity acting on the valve body to release heat from the tank 10. An oil flow is generated in the radiator circulation system returning into the tank 10 through the vessel 13 and the check valve 14. When the primary fluid pump 3 is operated, the check valve 14 closes due to back pressure acting on the valve body of the check valve 14 (pressure acting from the bottom to the top of the check valve in FIG. 1). An oil flow is generated through the next fluid circulation system. At this time, tank 10 → oil delivery pipe 11 → radiator 1
3→Check valve 14→Return oil guide pipe 12→No oil flow occurs in the radiator circulation system of tank 10.

As described above, in the device according to the present invention, when oil flow is occurring in the primary fluid circulation system, the oil flow in the radiator circulation system is blocked, and when no oil flow is occurring in the primary fluid circulation system, the heat radiation is interrupted. Oil flow is occurring in the vessel circulation system.

Furthermore, when an oil flow is generated in the radiator circulation system, the primary fluid circulation system is not closed by a valve or the like, so a slight oil flow will occur through this primary fluid circulation system.
This oil flow is minute compared to the oil flow in the radiator circulation system.

Secondary fluid pumps 4 are connected in series to the secondary flow path 15b of the heat exchanger 15, and n pieces (n is 2 or more) are connected in parallel to the series circuit of the secondary flow path 15b and the secondary fluid pump. (an integer of ) snow melting heat dissipation means M1 to M11 are connected.

More specifically, the inlet side of the secondary fluid pump 4 is connected to one end of the secondary flow path 15b, and the piping 22 is connected to the outlet side of the pump. Each of the n branch pipes Pal to Pan branched from the middle of this pipe 22 has a valve V.
It is connected to one end of the snow melting heat radiation means Ml-Mn through at to Van.

A pipe 23 is connected to the other end of the secondary flow path 15b, and branch pipes Pb1-Pbn branched from this pipe 23 pass through valves Vbl to vb11, respectively, and are connected to snow melting heat dissipation means Ml-M.
connected to the other end of n.

Each of the snow melting heat dissipation means has a secondary fluid flow path therein, and is buried at a predetermined interval under the road surface of the substation premises. In FIG. 1, the part shown within the broken line frame indicated by the symbol GL is the part installed under the road surface.

The illustrated snow melting heat dissipation means Ml-Mn are known as snow melting tube blocks, and each snow melting tube block is formed into a spiral shape with a pair of thermally conductive tubes arranged in parallel, and is located at the center of the spiral. It has a structure in which the ends are interconnected. In other words, in each snow melting tube block,
The outbound side (the side connected to piping 22) and the return side (the side connected to piping 23)
The two sides (the side connected to the side) are arranged in pairs so that the outbound side and the inbound side flow in opposite directions. By creating countercurrent flows in this way, it is possible to equalize the temperature distribution on the road surface.

The number of heat dissipation means for snow melting is appropriately determined depending on the amount of waste heat from the transformer, the snow melting area, the shape of the road surface, etc.

When the secondary fluid pump 4 is operated, the secondary fluid flows through the secondary fluid pump 4 → piping 22 → branch pipes Pal~Pan → valve (V
al,...Van)→Heat dissipation means for snow melting (Ml.

-0-Mn) →Valve (Vbl, -Vbn)
→ Branch pipe Pbl.

~Pbn-piping 23 → secondary flow path 15b of heat exchanger 15 →
It flows through the path of the secondary fluid pump 4.

As mentioned above, the valves Val,...Van, Vbl,
... By providing Vbn, it is possible to selectively melt snow at each part of the road surface where the snow melting heat dissipation means is embedded by opening and closing these valves.

In this embodiment, a secondary fluid circulation system is constituted by the secondary flow path 15b, the secondary fluid pump 4, the piping 22.23, and the snow melting heat radiation means M1 to Mn.

Operational control for accumulating or releasing waste heat from the transformer is performed by a control device 5.

This control device uses the temperature of insulating oil (oil temperature) detected by an oil temperature detector 1 attached to a tank 10 and the presence or absence of snowfall detected by a snowfall detector 2 as control conditions.
The primary fluid pump 3 and the secondary fluid pump 4 are controlled. The oil temperature detector 1 provides two types of signals to the control device 5, the details of which will be described later.

The snowfall detector 2 has a plurality of electrodes on an insulating plate surface that receives snowfall (or precipitation), and changes in the resistance value between the plurality of electrodes (when moisture adheres to the plate surface, there is a bridge between the electrodes due to moisture). The circuit has a circuit that detects moisture adhering to the board surface, and a circuit that detects the temperature at that time. This is a well-known device that determines that it is snowing when moisture is detected at a temperature (normally set at 1℃ to 3℃), and this snowfall detector 2 continuously outputs a signal until the snowfall stops. is sent to the control device 5.

A control device 5 receives a signal from an oil temperature detector 1 and a snowfall detector 2.
The primary fluid pump 3 and the secondary fluid pump 4 are automatically operated and stopped based on signals from the controller.

In addition to performing the automatic operation described above, the control device 5 has a function of switching the operation mode to manual operation, automatic operation using a time switch, etc., the details of which will be described later.

An oil sump servator 25 is attached to the tank 10, and a secondary fluid conservator 26 is attached to the secondary fluid circulation system (piping 23 in the illustrated example). It is designed to absorb changes in fluid volume.

The secondary fluid injected into the secondary fluid circulation system is a mixture of water and antifreeze. For example, propylene glycol (or ethylene glycol may be used) is suitable as the antifreeze, and the freezing temperature decreases as the proportion of propylene glycol added increases.

The mixing rate of antifreeze should be set at an appropriate value so that the secondary fluid does not freeze even at the lowest temperature expected at the location where the transformer is installed. .

5 and 6 are flowcharts showing the control algorithm of the control device 5, FIG. 5 shows the operation modes that can be selected by the selection switch provided in the control device, and FIG. 6 shows the automatic operation mode by the selection switch. The control algorithm when is selected is shown.

First, referring to FIG. 5, "manual", "automatic J" and "warm season" each indicate the switching position of a selection switch consisting of a three-point changeover switch. Here, "manual" indicates the position to be switched to when performing manual operation, and "automatic" indicates the position to be switched to when performing automatic operation with oil temperature and presence of snowfall as control conditions at the end of the stage.

In addition, "Warm season J" indicates the position to be switched to when automatic operation is performed by a timer during periods other than the end of the season.In addition, during the end of the season, a corresponding margin should be provided based on the average value of the first snow and last snow in the area where the transformer is installed. It is reasonable to anticipate and make assumptions.

The operation switch SW1 shown in FIG. 5 is a manual operation switch for the primary fluid pump 3, and by manually closing this switch, the primary fluid pump can be operated. Further, the operation switch SW2 is a switch for manually operating the secondary fluid pump 4, and the secondary fluid pump 4 can be operated by closing this switch SW2.

The time switch is used to operate the secondary fluid pump for a short time every predetermined period (for example, one week).
The secondary fluid pump 4 is closed for a certain period of time every predetermined period.
issues a command to operate for a certain period of time.

During the warm season when there is no snowfall, the selection switch is switched to "warm season". In this case, the secondary fluid pump 4 is operated every time the time switch is closed, and the secondary fluid pump 4 is stopped when the time switch is opened. The time switch is closed for a certain amount of time every week, for example. Since the rotating parts of the secondary fluid pump are in contact with water, if the pump is stopped for a long period of time, it may rust and cause problems in rotation.

Furthermore, if the secondary fluid circulation system is stopped for a long period of time, scale may accumulate in the secondary flow path of the heat exchanger 15 and its performance may deteriorate. By operating the secondary fluid pump at regular intervals using the time switch as described above, these problems can be prevented from occurring.

Further, in a state where the selection switch is switched to "warm season", the secondary fluid pump can be operated as desired by operating the operation switch SW2. That is, the secondary fluid pump 4 can be operated by closing the operation switch SW2, and the pump 4 can be stopped by opening the switch SW2.

Since the primary fluid pump 3 is submerged in oil and there is no risk of rust, the operating switch SWI for manually operating the primary fluid pump is kept open during the warm season.

Next, the operation when the selection switch is changed to "manual" will be explained. This "manual J" position is the position selected when the primary fluid pump and secondary fluid pump are manually operated by human judgment. For example, in the final stage, when automatic operation is selected, The primary fluid pump 3 and the secondary fluid pump 4 are automatically operated using the temperature and the presence or absence of snowfall as control conditions, but depending on the situation, it may be desired to continue operating the pumps 3 and 4. For example, there may be no snowfall but the road is frozen. This "manual" mode is selected when there is a concern.

When the "manual" mode is selected by the selection switch, the primary fluid pump 3 can be operated by closing the operation switch SWl, and the secondary fluid pump 4 can be operated by closing the operation switch SW2. Can be done.

Next, when the "automatic operation" mode is selected by the selection switch, automatic operation is performed using the oil temperature and the presence or absence of snow as control conditions. In this automatic operation, a sequencer is used to realize the primary fluid pump control means and the secondary fluid pump control means by a program created according to the control algorithm shown in FIG.

In this automatic operation mode, the following in-oil heat storage operation and
Underground heat storage operation and snow melting operation are automatically performed.

(A) Heat storage operation in oil This is an operation for storing heat in the transformer tank in preparation for snowfall when there is no snowfall. In this operating state, the primary fluid pump 3 is operated and the secondary fluid pump 4 is stopped.

At this time, the check valve 14 closes to stop the oil flow within the radiator 13, so that heat is not radiated through the radiator 13.

Also, since the secondary fluid circulation system is also stopped, heat exchanger 15
Almost no heat exchange takes place. Therefore, much of the waste heat is accumulated in the transformer tank 10, causing the oil temperature to rise. At this time, since the insulating oil is circulated through the primary fluid circulation system by operating the primary fluid pump, the temperature distribution within the tank 10 becomes uniform and the temperature distribution is not biased.

(B) Underground heat storage operation Although there is currently no snowfall, this operation is performed to store the waste heat of the transformer underground under the road surface in preparation for snowfall. Pump 3 and secondary fluid pump 4
are operated together, and the heat exchanger 15 performs heat exchange between the insulating oil and the secondary fluid to raise the temperature of the secondary fluid.

The heat of this secondary fluid is radiated into the ground under the road surface through the snow melting heat radiating means M1 to Mn, and is stored in the ground. This operation raises the temperature of the road surface, so if it snows, it melts quickly.

(C) Snow Melting Operation In this operation performed during snowfall, both the primary fluid pump 3 and the secondary fluid pump 4 are operated. In this case as well, the heat exchanger 15
This causes heat exchange between the insulating oil and the secondary fluid to increase the temperature of the secondary fluid, and the heat of the secondary fluid is radiated into the ground under the road surface through the snow melting heat radiating means M1 to Mn. This increases the temperature of the road surface and melts the snow.

Next, details of the operation in the automatic operation mode will be explained with reference to the flowchart in FIG.

In this automatic operation, the signal from the oil temperature detector 1 and the signal from the snowfall detector 2 are used as control signals.

The oil temperature detector 1 generates a first signal TI that shows a change with hysteresis as shown in FIG. 7 with respect to a change in oil temperature θ, and a first signal TI that shows a change with hysteresis as shown in FIG. A second signal T2 exhibiting a change with a certain hysteresis is generated.

In FIG. 7 and FIG. 8, θ1 is the temperature of the secondary fluid pump 4 when the oil temperature decreases with no snowfall detected.
Temperature (
secondary fluid pump stop judgment reference temperature), which is set to a relatively low value. It is assumed that the secondary fluid pump 4 is stopped when the oil temperature decreases to below this temperature θ1 in a state where snowfall is not detected.

θ2 is a temperature (secondary fluid pump operation judgment reference temperature) that serves as a criterion for determining whether or not to start operation of the secondary fluid pump 4 in the initial state and in the process of increasing oil temperature;
The operation of the secondary fluid pump 4 is assumed to start when the oil temperature reaches this temperature 02 or higher in the initial state and in the process of increasing the oil temperature.

θ3 is a temperature that serves as a reference for determining whether to start or stop the operation of the primary fluid pump and the secondary fluid pump while the oil temperature is decreasing. In the process of decreasing the oil temperature, when the temperature becomes below θ3, the operation of the primary fluid pump 3 is started,
The operation of secondary fluid pumps shall be permitted.

θ4 is the set maximum temperature that serves as the criterion for stopping the operation of the primary fluid pump and secondary fluid pump in the initial state and in the process of increasing oil temperature. The primary fluid pump and secondary fluid pump shall be allowed to operate when the set maximum temperature is less than 04, and the primary fluid pump and secondary fluid pump shall be stopped when the oil temperature reaches the set maximum temperature 64 or higher. shall be taken as a thing.

Here, θ4 is set lower than the upper limit of the allowable temperature of the insulating oil in the transformer. If the upper limit of the allowable temperature of the insulating oil is normally about 55°C, θ4 is set to, for example, the daily average temperature at the end of the period + about 50°C. Further, θ1 is set to about θ4-15°C.

As can be seen from FIGS. 7 and 8, the relationship between θl and θ4 is θl, θ2, θ3<θ4.

The first signal TI generated by the oil temperature detector 1 becomes high level when the oil temperature is 02 or higher in the initial state, and as the oil temperature increases, it becomes high level when the oil temperature reaches 02 or higher. from low level to high level.

Further, in the process of decreasing the oil temperature, the level changes from a high level to a low level when the oil temperature becomes θ1 or less. Figures 6 and 7
In the figure, the state where the signal TI is at a high level is T
1=1, and the state in which the signal T1 is at a low level is defined as T1=0.

In addition, the second signal T2 goes to a high level when the oil temperature is 04 or higher in the initial state, and as the oil temperature increases, it changes from a low level to a high level when the oil temperature reaches 04 or higher. become the level. Further, in the process of decreasing the oil temperature, the signal T2 changes from a high level to a low level when the oil temperature becomes 03 or less. In FIGS. 6 and 8, a state in which the signal T2 is at a high level is defined as T2=1, and a state in which the signal T2 is at a low level is defined as T2=0.

When the selection switch is switched to automatic operation and automatic operation is started, an operation command is issued to the primary fluid pump 3 in step Pi of FIG. 6, and the pump 3 is operated. Next, in step P2, the state of signal TI is determined, and in step P3, it is checked whether snowfall has been detected.

When the signal TI is at a low level (θ<θ2) and when snowfall is not detected, only the primary fluid pump 3 continues to operate (thermal storage operation in oil). Oil temperature rises and θ≧
When θ2 or snowfall is detected by the snowfall detector 2, an operation command is given to the secondary fluid pump 4 in step P4, and the secondary fluid pump 4 is operated. Then, in step P5, the state of signal T2 is determined. When the oil temperature rises to the set maximum temperature 04 or higher and the signal T2 becomes high level, a stop command is issued to the primary fluid pump 3 and the secondary fluid pump 4 in step P6, and these pumps are stopped. Operation will be stopped. In this state, an oil flow is generated through the radiator 13 and steady operation is performed, and the insulating oil is cooled by the radiator 13.

In step P7, the state of the signal T2 is determined,
If the oil temperature exceeds θ3, the primary fluid pump and
Next, keep the fluid pump stopped. When the oil temperature becomes equal to or lower than θ3 due to heat dissipation by the radiator 13, the process returns to step P1, where an operation command is issued to the primary fluid pump 3, and the operation of the pump 3 is restarted.

Primary fluid pump 3 and secondary fluid pump 4 in cold weather
Under conditions in which both transformers are operated, the oil temperature normally decreases (unless the load on the transformer increases). If the oil temperature is less than the set maximum temperature 04 while both the primary fluid pump and the secondary fluid pump are being operated, the signal T2 is at a low level, so the signal T2 is set at a low level.
A determination of the state of l is made. When the signal Tl is at a high level (when θ>θ1), the process returns to step P5.

When the oil temperature falls below θl and the signal TI becomes low level, it is then determined in step P9 whether or not the snowfall detector detects snowfall. As a result, if snowfall is detected, the process returns to step P5 and the operation of the primary fluid pump and secondary fluid pump continues. This state is snow melting operation.

When it is determined in step P9 that snowfall is not detected (θ≦θI and there is no snowfall), a stop command is given to the secondary fluid pump 4 in step PIO, and the operation of the pump is stopped. .

This state is heat storage operation in oil, and heat is stored within the transformer. After performing step PIO, the process returns to step P2 in which the state of signal T1 is determined.

Note that the flowchart showing the control algorithm for automatic driving is not limited to the one shown in FIG. 6, and various modifications are possible. For example, after performing step P5 in FIG. 6, when T2 is at a low level (T2=O), step P5 is repeated again, and steps P8 to PI
O may be omitted. In this way, once the secondary fluid pump 4 starts operating, it continues to operate without stopping unless θ≧θ4, but the control circuit becomes simple.

Also, by incorporating a delay means between step P9 and step P10 in FIG. 6 or within step PIO,
The secondary fluid pump may be stopped after a certain delay time has passed after snowfall is no longer detected in step P9.

If the snowfall rate (the amount of snowfall per hour) is high, the snow will not melt immediately and there is a possibility that residual snow will remain on the road surface even after the snowfall has stopped. Therefore, in order to ensure complete snow melting, it is preferable to continue the snow melting operation for a predetermined period of time even after snowfall is no longer detected, as in the above modification.

Although it is not shown in the flowchart of Fig. 6, if there is an abnormality in the device while it is being operated in an operation mode other than normal operation, it will automatically switch to steady operation mode (primary fluid pump 3 and The secondary fluid pump 4 is stopped and the radiator 1
3), and is fixed to the steady operation mode. In this case, the equipment abnormality includes, for example, cutoff of the control power supply, excessive rise in oil temperature, stoppage of oil flow under the primary fluid pump operation command, stoppage of the flow of secondary fluid under the secondary fluid pump operation command, Lowering of the secondary fluid level in the secondary fluid circulation system (Conservator 2
6), water leakage in the heat exchanger 15, etc.

Although the above description has been made regarding the case where the radiator that cools the insulating oil during steady operation is a self-cooling type, the present invention is not limited to this. For example, as shown in FIG. 2, a forced air cooling type radiator equipped with a blower fan 30 is used, or as shown in FIG. 3, an oil feeding self-cooling type radiator equipped with an oil feeding pump 31 is used. You can also. Also the third
The present invention can also be applied to the case where an oil blowing air cooling type radiator is used, in which the radiator shown in the figure is further provided with a blower fan.

When using a radiator equipped with an oil pump 31 as shown in FIG. 3, it is necessary to prevent insulating oil from flowing toward the heat exchanger 15 when the pump 31 is operating. It is necessary to insert a valve 32 for preventing backflow into the system including the fluid pump 15 and the primary fluid pump 3.

In the example shown in FIG. 3, a valve 14 for preventing backflow provided in series with the radiator 13 and a valve 32 provided in the system on the side of the heat exchanger 15 and the primary fluid pump 3 are opened and closed by electrical signals. A controlled solenoid valve is used. When using a solenoid valve in this way, a step for controlling the solenoid valve is added to the flow showing the control algorithm for automatic operation.

Of course, check valves may be used as the valves 14' and 32 in FIG.

In addition, when using electromagnetic valves as the valve 14' and the valve 32, one pump is installed in the piping 12, serving both as the oil pump 31 for normal operation of the radiator and as the primary fluid pump 3. You can.

[Effects of the Invention] As described above, according to the present invention, there is no need for fuel or combustion equipment for snow melting, and the waste heat of the transformer is guided to the snow melting heat dissipation means buried under the road surface through a heat exchanger to melt the snow on the road surface. Since the snow is discharged at the same time, it is possible to perform road surface snow melting at low operating costs and with high reliability.

Furthermore, according to the invention set forth in claim 6, not only can the pump be operated automatically, but also an in-oil heat storage operation and an underground heat storage operation can be performed to store heat in electrical equipment in preparation for snow melting. This has the advantage that snow can be melted quickly and reliably even when the load factor of the transformer is low and the amount of waste heat is small. Furthermore, when the oil temperature exceeds the set maximum temperature, the pump stops operating and the radiator is allowed to operate steadily, making it possible to effectively utilize waste heat without compromising the reliability of oil-filled electrical equipment. .

[Brief explanation of the drawing]

1 to 3 are schematic configuration diagrams showing different configuration examples of the snow melting device of the present invention, FIG. 4 is a block diagram showing a configuration example of a control device used in the snow melting device according to the present invention, and FIG. The figure is a flowchart showing the operation modes that can be selected by the control device in Fig. 4, Fig. 6 is a flowchart showing the control algorithm when the automatic operation mode is selected by the control device, and Figs. FIG. 3 is a diagram for explaining signals obtained from an oil temperature detector used in an embodiment of the invention. 1...Oil temperature detector, 2...Snowfall detector, 3...1
Secondary fluid pump, 4... Secondary fluid pump, 5... Control device, 13... Heat radiator, 14... Check valve, 15...
- Heat exchanger, M1 to Mn... Heat dissipation means for snow melting. Figure 4 Figure 7 Figure 8

Claims (6)

[Claims] (1) A heat exchanger that has a primary flow path through which a primary fluid flows and a secondary flow path through which a secondary fluid flows, and performs heat exchange between the two flow paths, and the primary flow path and the secondary flow path. A primary fluid pump and a secondary fluid pump each connected in series with the passage, and an internal flow passage through which the secondary fluid passes, and dissipates heat of the secondary fluid passing through the internal passage to the outside. a heat radiating means for snow melting, wherein both ends of a series circuit of the primary flow path of the heat exchanger and the primary fluid pump are connected to a tank of an oil-filled electrical device equipped with a radiator, A primary fluid circulation system is configured to circulate insulating oil in the tank through the primary flow path of the heat exchanger during operation of the fluid pump, and the snow melting heat dissipation means circulates the insulating oil in the tank through the primary flow path of the heat exchanger. 2
A secondary fluid circulation system is configured by the snow melting heat radiating means, the secondary flow path, and the secondary fluid pump, and prevents backflow of the insulating oil within the radiator. A valve is connected in series with the radiator, and a series circuit of the primary flow path of the heat exchanger and the primary fluid pump is connected in parallel with the series circuit of the radiator and the valve. A snow melting device using waste heat from oil-filled electrical equipment. (2) The snow melting device using waste heat from oil-filled electric equipment according to claim 1, wherein a plurality of the snow melting heat radiating means are provided and the plurality of snow melting heat radiating means are connected in parallel to each other. (3) The snow melting device using waste heat from oil-filled electrical equipment according to claim 1 or 2, wherein the valve is a check valve that automatically closes when the pressure on the inlet side becomes lower than the pressure on the outlet side. (4) The snow melting device using waste heat from oil-filled electric equipment according to claim 1, wherein the valve is a solenoid valve that is closed when the primary fluid pump is operated. (5) The snow melting device using waste heat from oil-filled electrical equipment according to any one of claims 1 to 4, wherein the secondary fluid is a mixture of water and antifreeze. (6) an oil temperature detector that detects the oil temperature in the tank of the oil-filled electrical equipment, a snowfall detector that detects the presence or absence of snowfall, and the primary fluid pump using the oil temperature and the presence or absence of snowfall as control conditions. and a control device that controls a secondary fluid pump, the control device operating the primary fluid pump when the oil temperature is lower than a set maximum temperature that is set lower than an allowable upper limit value, and 1. Controlling the primary fluid pump so as to stop the primary fluid pump when the temperature exceeds the set maximum temperature.
a secondary fluid pump control means, operating the secondary fluid pump when the oil temperature is less than the set maximum temperature while snowfall is detected by the snowfall detector, so that the oil temperature is equal to or higher than the set maximum temperature; The secondary fluid pump is stopped when the oil temperature reaches a predetermined temperature range that is lower than the set maximum temperature when the snowfall is not detected. When the secondary fluid pump is operated and the oil temperature falls below a predetermined temperature set on the lower temperature side than the temperature range, the secondary fluid pump is stopped, and the oil temperature is and a secondary fluid pump control means for controlling the secondary fluid pump so as to stop the operation of the secondary fluid pump when the temperature exceeds the set maximum temperature. Any one of 5 to 5
A snow melting device using waste heat from oil-filled electrical equipment described in .