JPS6233723B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forced cooling type stationary induction electric appliance, and in particular, the number of operating coolers for cooling the stationary induction electric appliance is changed in accordance with load fluctuations of the stationary induction electric appliance having windings and iron cores. The present invention relates to a winding temperature adjustment device suitable for use in forced cooling stationary induction appliances.

It is generally known that electrical equipment generates heat when used, and various cooling methods are provided depending on the type and capacity of the electrical equipment. Among these electric devices, stationary induction electric devices include windings and iron cores, and correspond to transformers and reactors. Here, a description will be given below using a transformer as an example.

FIG. 1 is a block diagram showing the schematic structure of a conventional forced cooling transformer. In FIG. 1, a transformer 1 as a stationary induction electric appliance supports a winding 3 wound around an iron core 2 from upper and lower sides, and upper and lower clamping fittings 4 and 5 for tightening the iron core 2.
The transformer 1 is housed in a tank 7 together with cooling oil 6 as a cooling medium. A plurality of coolers 12 for cooling the cooling oil 6 are connected to the upper and lower headers of the tank 7 via an upper piping 9 and a lower piping 11 equipped with a pump 10 for forcibly circulating the cooling oil 6. Although not shown, the cooler 12 is configured such that a large number of pipes are provided with fins, a fan is provided for forcibly cooling the fins, and the pump 10 is attached. In addition, the cooler 1
There are approximately 10 2nd class seats per tank. Therefore, the same components such as the cooler 12 are given the same reference numerals, and the same systems are given the same suffixes in the description. A bushing 13 is provided on the upper part of the tank 7, and the bushing 13 and wiring 14 are connected from the transformer 1.
Power is supplied to a load (not shown) through the power supply. The wiring 14 is provided with a current transformer (hereinafter referred to as CT) 15.
Load fluctuations can be detected by CT15. The load fluctuation detected by the CT 15 is taken into the control circuit 16, and the
In order to reduce the loss of auxiliary equipment consisting of fans (not shown) for the coolers 12 and 12, the number of operating coolers 12 is changed and controlled based on the operation command 17 from the control circuit 16 according to load fluctuations. It's becoming like that. Note that the operation command 17 is a signal for stopping the operation of the pump 10 and the fan of the cooler 12.

According to the conventional example configured in this way, fluctuations in the load connected to the transformer 1 are detected by the CT 15, this detection signal is taken into the control circuit 16,
The control circuit 16 generates an operation command signal 17 that changes and controls the number of operating coolers 12 (including the pump 10) according to the ratio of load fluctuation to the rating of the transformer 1.
is output to each cooler 12. Cooler 1 like this
When the operation control described in No. 2 is performed, there is a problem in that the winding temperature increases significantly due to a sudden increase in load from a reduced load state. Regarding this issue, the second
This will be explained with reference to the figures.

FIG. 2 is a characteristic diagram showing the relationship between cooling oil and winding temperature with respect to load current, with time t plotted on the horizontal axis.
The vertical axis shows load current I, permissible winding temperature θ _P , winding temperature θ _W and cooling oil temperature θ _O , respectively.

In FIG. 2, the load current I ₁₀ before time t ₁ is
Assuming that the capacity is small compared to the rated capacity of the transformer 1, the number of coolers 12 is reduced to such an extent that the temperature of the winding 3 does not exceed an allowable value. Therefore, the cooling oil temperature is generally higher than the cooling oil temperature in the rated operating state.

At time t ₁ , if the load suddenly increases, CT1
Since the load current _I20 is detected by the cooler 12, the control circuit 16 that has taken in this current value
a, 12b,..., (pump 10a, 10b,...)
drive all at once. However, after this time _t1 , even if all the coolers 12a and 12b are operated at the same time, the time constant of the cooling oil temperature is as long as several hours, so the cooling oil temperature θ _O gradually decreases as shown in the curve A shown in the figure. It only decreases. As a result, the winding temperature θ _W of the winding 3 after time t ₁ rises rapidly as shown by curve B shown in the figure, exceeding the permissible winding temperature θ _P , and the cooling oil temperature θ _O remains constant. The period t ₁ until it drops to the value θ _O1
An inconvenient phenomenon occurs in that the temperature does not fall below the allowable temperature θ _P at ~t ₂ . Therefore, during this period t ₁ to _{t 2} , the winding 3 of the transformer 1 had the disadvantage of being significantly thermally degraded.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to prevent the winding temperature from rising when the load suddenly increases, to prevent thermal deterioration of the winding, and to reduce the number of coolers in operation at low loads. An object of the present invention is to provide a winding temperature regulating device that saves energy.

In order to achieve the above object, the present invention detects the winding temperature based on load fluctuations and detection signals from the cooling medium, or arranges a winding temperature monitor in the cooling medium that generates heat in response to load fluctuations. The temperature of this winding temperature monitor is detected, and if it is determined that the detected winding temperature exceeds the permissible winding temperature, a coolant with a temperature sufficiently lower than this coolant temperature is added to the forcedly circulated coolant. This mixture suppresses the rise in winding temperature.

Embodiments of the present invention will be described below based on the drawings.

FIG. 3 is a configuration diagram showing the main parts of the first embodiment of the winding temperature adjusting device according to the present invention. In FIG. 3, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and explanations thereof will be omitted. The difference between the configuration of the first embodiment shown in FIG. 3 and the configuration shown in FIG. A refrigerant storage tank 18 is provided which can store a predetermined amount of cooling oil 6' as a cooling medium whose temperature is sufficiently lower than the oil temperature of the cooling oil 6 forcedly circulated in the tank 7.
A mixing means 20 is provided for mixing the cooling oil 6' in the forcibly circulated cooling oil 6 when there is a mixing command 101 from the control circuit 100, and the load fluctuation is sent to the control circuit 100 via the CT 15. At the same time, the cooling oil temperature from the temperature sensor 19 attached to the upper part of the tank 7 or near the upper pipe 9 is also taken into the control circuit 100.
0 detects the winding temperature θ _W using the following formula (1) based on the load fluctuation and cooling oil temperature from both detectors,
The main feature is that the mixing command signal 101 can be output when it is determined that the winding temperature θ _W exceeds the permissible winding temperature θ _P.

More specifically, the mixing means 100 is provided with a bypass pipe 21, which is connected to the refrigerant storage tank 18 as shown in the figure, and the connection point between the bypass pipe 21 and the lower pipe 11 is connected to a branch part 22, and a merging section 23, and a branching section 22 is provided with a diverting valve 24. Note that the flow dividing valve 24 is adapted to be driven by a driving device 25.

Further, the control circuit 100 stores the following equation (1) and is capable of calculating the winding temperature θ _W using the load current from the CT 15, the detected temperature from the temperature detector 19, and the equation (1). It's getting old. That is,
The winding temperature θ _W is defined as θ _T which is the ambient temperature of the tank 7, θ _O which is the temperature of the cooling oil in the tank 7, θ _OW which is the temperature of the cooling oil due to the temperature rise of the winding 3, and the temperature of the part of the winding 3. If the temperature margin considering the variation is θ _f , θ _W = (θ _T + θ _O + θ _OW + θ _f )...(1) Here, the cooling oil temperature θ due to the temperature rise of winding 3
_OW is detected by the temperature detector 19, and this temperature θ _OW is, for example, θ _OW =C/√ (however,
C is a constant, and V is the flow rate of the cooling oil 6 flowing through the winding 3. ) is given by Note that θ _T , θ _O ,
Generally, θ _f is given in advance as a constant.

The operation of the first embodiment configured as described above will be explained below with reference to FIG.

In FIG. 2, the operation before time _t1 is the same as the operation in FIG. 1, so it will be omitted, and the operation after time _t1 will be explained. At time _t1 , the load current I is
When I suddenly increases from I ₁₀ to I ₂₀ , the control circuit 100
Based on the detection signal from the CT 15, an operation command 17 is output to operate the cooler 12 (including the pump 10) in the number of units in operation according to the state of the load. Next, the control circuit 100 that receives the cooling oil temperature θ _OW via the temperature detector 19 calculates the winding temperature θ _W using equation (1), and sets this winding temperature θ _W to the preset winding temperature. Compared to the allowable temperature θ _P , the winding temperature θ _W
When it is determined that the temperature exceeds the temperature θ _P , the mixing means 2
A mixing command 101 is output to the drive device 25 of No. 0.
Then, the drive device 25 switches the flow dividing valve 24 to the bypass pipe 21 side, and the refrigerant storage tank 18
The cooling oil 6' inside is mixed with the cooling oil 6 that is being forcedly circulated. In other words, the circulation route is the lower piping 11
branch part 21, bypass piping 21, refrigerant storage tank 1
8, a confluence section 23, a pump 10, and a tank lower header. In this way, since the cooling oil 6' from the refrigerant storage tank 18 is immediately supplied to the winding 3 of the transformer 1, the temperature of the cooling oil 6 decreases as shown by the curve C shown in FIG. Therefore, the winding temperature θ _W becomes like the curve D shown in FIG. 2, and does not exceed the permissible winding temperature θ _P , so that thermal deterioration of the winding 3 can be prevented.
Furthermore, since the winding temperature θ _W can be immediately reduced,
The number of operating coolers 12 during low load can be minimized. Therefore, the number of operating auxiliary machines can be reduced, which has the advantage of saving energy.

FIG. 4 is a configuration diagram showing main parts of a second embodiment of the present invention. The second embodiment shown in FIG.
The difference from the example is that load fluctuations are detected.
The winding temperature monitor 30, which generates heat according to load fluctuations due to the current from the CT 15, is connected to the cooling oil 6 in the tank 7.
The temperature θ _WW of the winding temperature monitor 30 is detected by the temperature detector 19 and taken into the control circuit 100, and the detected temperature θ _WW is the winding temperature θ _W of the winding 3.
This temperature θ _WW is compared with _the permissible winding temperature θ _P by using _the correspondence between There are no changes to other components. Therefore, the same components as in the second embodiment and the first embodiment are given the same reference numerals.
A description of the configuration will be omitted. This second embodiment has the same functions and effects as the first embodiment, and has the advantage that the control circuit 100 is simplified because the calculation of equation (1) is not required.

As a modification of the present invention, the dividing valve 24 of the mixing means 20 may be provided at the confluence section 23 of the lower pipe 17 and the bypass pipe 21, or at both the branch section 22 and the confluence section 23. be.

Next, as another modification, the refrigerant storage tank 18 and the mixing means 20 may be attached to the upper pipe 9. Even in this case, the same effects as in the first and second embodiments described above can be obtained.

Furthermore, as another modification, the refrigerant storage tank 18
In order to increase the cooling effect by mixing the cooling oil 6' from the winding 3 only with the cooling oil of the winding 3,
As shown in the figure, the cooling oil 6 in the upper space of the windings and the cooling oil 6 in the lower space may be separated by a heat-insulating partition plate 31. Such a configuration has the advantage that in addition to increasing the cooling effect, the amount of cooling oil 6' in the cooling storage tank can be reduced.

Note that it is desirable to attach cooling fins to the refrigerant storage tank 18 to lower the temperature of the cooling oil 6'. Of course, the refrigerant storage tank 18 may be cooled by other methods.

FIG. 5 is a configuration diagram showing a third embodiment according to the present invention. This third embodiment differs from the first embodiment in that a heat insulating lower partition plate 32 is provided between the lower part of the winding 3 and the tank 7 as the refrigerant storage tank 18, and the lower part of the refrigerant storage tank 18 is A diversion valve 24 is provided at the connection between the piping 11 and the lower clamping bracket 5, and the flow is opened to the lower clamping bracket 5 side or the lower side of the tank 7 by the diverting valve 24, and the lower clamping bracket 5 are provided with valves 33, 33 at the lower part of the valve 33,
33 is that the mixing means 20 is configured to be opened when the diverter valve 24 is opened to the lower side of the tank 7. Note that the flow dividing valves 32 and 33 are connected to the lower side of the tank 7 by a mixing command 101 from a control circuit 100.

According to the third embodiment, it has the same functions and effects as the first and second embodiments, and also has the advantage that the refrigerant storage tank 18 and the bypass pipe 21 can be omitted. Although the above embodiment has been described using the transformer 1 as an example, it goes without saying that it can be applied to other stationary induction electric appliances.

As described above, according to the present invention, when the winding temperature exceeds the permissible winding temperature, a low temperature cooling medium is mixed with the forcedly circulated cooling medium to suppress the increase in the winding temperature. This has the effect of reducing auxiliary equipment loss and preventing thermal deterioration of the windings of stationary induction appliances.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the schematic structure of a conventional forced cooling transformer, Fig. 2 is a characteristic diagram showing the relationship between load current, winding temperature, and cooling oil, and Fig. 3 is a first embodiment according to the present invention. FIG. 4 is a block diagram showing a second embodiment according to the present invention, and FIG. 5 is a block diagram showing a third embodiment according to the present invention. 1...Transformer, 2...Iron core, 3...Winding, 4 and 5...
Upper and lower fasteners, 6 and 6'...Cooling oil, 7
...Tank, 10...Pump, 12...Cooler, 15...
Instrument current transformer (CT), 18... Refrigerant storage tank, 19...
Temperature detector, 20... Mixing means, 30... Winding temperature monitor, 31 and 32... Upper and lower partition plates.

Claims (1)

[Scope of Claims] 1. Cooling the cooling medium in the upper and lower headers of a tank that accommodates a stationary induction electric appliance having windings and an iron core together with a cooling medium, and forcibly circulating the cooling medium from the upper header to the lower header. A plurality of coolers equipped with pumps are connected to each other, load fluctuations of the stationary induction electric appliance are taken into a control circuit, and the number of operating coolers is controlled by the control circuit based on the load fluctuations. In the winding temperature adjustment device, a refrigerant storage tank stores a predetermined amount of cooling medium, and mixing means mixes the cooling medium in the refrigerant storage tank with the forcedly circulated cooling medium when a mixing command signal is received. , a temperature detector for detecting the coolant temperature near the top of the tank, and the control circuit detects the winding temperature based on the load fluctuation and the coolant temperature from the temperature detector, and detects the winding temperature. A winding temperature adjustment device configured to output a mixing command to the mixing means when it is determined that the temperature exceeds the permissible temperature of the winding. 2. A cooler equipped with a pump that cools the cooling medium and forcibly circulates the cooling medium from the upper header to the lower header, in the upper and lower headers of a tank that houses a stationary induction electric appliance having windings and an iron core together with a cooling medium. In a winding temperature adjustment device, a plurality of coolers are connected, load fluctuations of the stationary induction electric appliances are taken into a control circuit, and the number of operating units of each cooler is controlled by the control circuit based on the load fluctuations. , a refrigerant storage tank for storing a predetermined amount of refrigerant; a mixing means for mixing the refrigerant in the refrigerant storage tank with the forcibly circulated refrigerant when a mixing command signal is received; A winding temperature monitor that generates heat in response to load fluctuations in a cooling medium and a temperature detector that detects the temperature of the winding temperature monitor are provided, and the control circuit is configured to detect whether the temperature from the temperature detector is within the permissible range of the winding. A winding temperature adjustment device configured to output a mixing command to the mixing means when it is determined that the temperature exceeds the temperature.