JPS5933809A - Transformer cooling apparatus - Google Patents

Abstract

PURPOSE:To eliminate the insertion loss of a variable-frequency inverter and contrive an improvement in efficiency, by a method wherein a cooler is driven by the variable-frequency inverter when a transformer is in a light load condition thereby to reduce the auxiliary loss and is directly driven by a commercial frequency power source when the transformer is in a load condition near its rated load. CONSTITUTION:With an electromagnetic contactor 8 opened, electromagnetic contactors 13 and a no-fuse breaker 9 are closed to connect a cooler 2 to a variable-frequency inverter 12. Any change in output frequency of the inverter 12 changes the revolution numbers of oil transfer pump motors 3 and fan motors 4, resulting in changes in oil transfer rate and air-supply rate. Consequently, the cooling capacity and auxiliary loss of the cooler 2 change. On the basis of a signal detected by a detection unit 5, an arithmetic control unit 1 obtains a required cooling capacity in accordance with the load condition of the transformer. The electromagnetic contactors 8 and 13 in combination constitute a selector circuit for selectively changing over between a commercial frequency power source 10 and the variable-frequency inverter 12. When the transformer is in a load condition near its rated load and the insertion loss of the variable- frequency exceeds the auxiliary loss reducing effect offered by the control of revolution number of the cooler, the selector circuit changes over to the commercial frequency power source to drive the transformer directly by the commercial frequency power source.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling system for a forced cooling type transformer, such as an oil supply air-cooled type, and particularly relates to a cooling system for a forced cooling type transformer such as an oil supply air-cooled type. This invention relates to an improvement in a cooler operation control method to reduce the

Figure 1 is a configuration diagram centered on the cooling system of a conventional oil-feeding air-cooled transformer. Oil pump and motor (
(hereinafter referred to as oil pump motor), (4) is a ventilation fan and motor (hereinafter referred to as fan motor), (5) is a detection unit that detects the operating state of the transformer, and (7) is a detection unit (5). The oil pump motor (
3) and the fan motor (4) power circuit with an electromagnetic contactor (8).
), (9) is a no-use circuit breaker that opens and closes the power supply for the entire cooling system, and (6) is a control unit (7).
), an electromagnetic welder (8), a cooler control panel that houses the No. 7 use circuit breaker (9), etc., and a commercial frequency power source.

The oil pump motor (3) and fan motor (4) are induction motors, and the detection signal of the detection unit (5) is generally the transformer load current and/or temperature. There is.

FIG. 2 is a block diagram showing the main parts of the cooling device shown in FIG. 1, and shows a case where four coolers are connected. In Figures 1 and 2, among the connection edges between devices and devices, solid lines indicate power lines, dashed lines indicate signal lines, and dash-dotted lines indicate control lines to electromagnetic contactors, and the same applies to the following figures. .

A conventional oil-feeding, air-cooled transformer is constructed as described above, and the cooling device is selected so that the temperature of the transformer is below a specified temperature rise limit under rated load conditions. Follow me,
Under light load conditions, where the load on the transformer is lower than the rated load,
The loss generated by the transformer is reduced compared to the rated load state, and even if some coolers are stopped, the transformer can operate below the specified temperature rise limit, reducing auxiliary equipment loss. . For this reason, the number of operating coolers is controlled according to the operating state of the transformer detected by the detection unit (5).

Figures 3 and 4 show examples of conventional cooler operation control methods. In the method shown in Figure 3, the load current detected by the detection unit (5) falls into any of the preset current categories. The control unit (7) determines whether there is one, and closes the electromagnetic contactor (8) of a predetermined cooler (2) corresponding to the corresponding category to control the number of operating coolers. Furthermore, in the method shown in Fig. 4, the detection section (5
) to detect the transformer temperature and perform similar operation control. In this case, the auxiliary equipment loss of the entire cooling system is proportional to the number of operating coolers, and the auxiliary equipment loss can be reduced compared to the rated operation.

However, in recent years, from the viewpoint of energy conservation, there has been a demand for further reduction of auxiliary loss in transformers.

An object of the present invention is to provide a cooling device that can further reduce auxiliary equipment loss and increase operating efficiency as compared to the above-mentioned control methods as an operation control method for a transformer cooler.

FIG. 5 is a block diagram showing the main parts of a cooling device according to an embodiment of the present invention, and shows a case in which four (or four groups) of coolers are connected. In Figure 5, (2) to (5)
, (8) to 00 are the same as in FIG.
) and the variable voltage cylinder Ij that supplies the fan motor (4)
L-loss inverter (hereinafter referred to as variable frequency inverter), αυ
is the oil pump motor (
3) and an arithmetic control unit that determines the drive frequency of the fan motor (4) and outputs the command signal to the variable frequency inverter @, and an electromagnetic contactor that opens and closes the variable frequency inverter (6) up to α3t.

In the cooling device configured as above, electromagnetic contact @
(8), close the electromagnetic contactor t)I and the no-use circuit breaker (9), connect the cooler (2) to the variable frequency impark, and change the output frequency of the variable frequency inverter (2). , oil pump motor (3) and fan motor (4)
) changes, and the amount of oil and air blown changes, so the cooling capacity of the cooler (2) and the auxiliary equipment loss change. 6th
The figure and Fig. 7 show an example of the relationship between the driving power frequency i of the oil pump motor (3) and the 7-arm motor (4), the cooling capacity of the cooler, and the auxiliary equipment loss. While the shaft power of the fan changes in proportion to the 8th power of the rotation speed, changes in cooling capacity are generally slower than changes in auxiliary equipment loss, so changes in the cooling capacity of the entire cooling system are Oil pump motor (3) and 7 motor (4) E
If this is done by changing the cooling capacity, the auxiliary equipment loss will be lower even with the same cooling capacity, compared to the conventional case of changing the number of operating coolers. Therefore, based on M″8 detected by the detection unit (5), the required cooling capacity according to the load condition of the transformer is determined in the arithmetic and control unit αη, and the corresponding oil pump motor (3) and fan motor are If the output frequency of the variable frequency inverter 0 is controlled so as to obtain the rotation speed (4), the compensation loss can be further reduced compared to the conventional cooling device.

In addition, in FIG. 5, the electromagnetic contactors (8) and 03 are switching circuits for selectively switching the driving power source of the cooler (2) to either the commercial frequency power source 00 or the variable frequency inverter α, and the rated frequency The aim is to improve efficiency in the vicinity. In other words, in the vicinity of the rated frequency, within the range where the insertion loss of the variable frequency inverter exceeds the auxiliary equipment loss reduction effect by controlling the rotation speed of the cooler, it is advantageous to switch to the commercial power source and drive directly with the commercial power source. Furthermore, the capacity of the variable frequency inverter can also be reduced. Furthermore, even when a failure occurs in the variable frequency inverter @, it is possible to switch to commercial power and continue operating the cooler.

However, the commercial power supply 0υ from the variable frequency inverter (6)
When switching to the oil pump motor (3) or fan motor (4), if the output frequency of the variable frequency inverter (2) differs from the commercial frequency, or if the frequencies match but the phases differ, Excessive current may flow and damage the oil pump motor, fan motor, variable frequency inverter, etc. Therefore, when switching the power supply of the cooler from the variable frequency inverter (6) to the commercial power supply 0υ, or conversely from the commercial power supply 0υ to the variable frequency inverter @, the oil pump motor (3) and the )
It is necessary to stop it once and then restart it.

FIG. 8 is a block diagram of a cooling system showing another embodiment of the present invention. When the oil pump motor is temporarily stopped in order to switch the power supply of the cooler, the cooling oil flow in the windings and core of the transformer is stopped. This is effective when the insulation is likely to deteriorate due to overheating of the windings or core. That is, this embodiment makes it possible to switch the power supply of the cooler without completely stopping the flow of cooling oil inside the transformer.

FIG. 8 shows a case where the cooler and the variable frequency inverter are each configured in two groups. In Figure 8, (3) to (5)
) and (9) ~ 0υ are the same as in Figure 5, and (2
a) and (2b) are a cooler group composed of one or more coolers, (12a) and (12b) are variable frequency inverters, and (8a), (8b), (18a) and (18b) are It is an electromagnetic contactor.

In the cooling device configured as described above, the No. 7 use circuit breaker (9), the electromagnetic contactors (18a), (18b) are closed, the electromagnetic contactors (8a), (8b) are opened, and the cooler ( 2) as a variable frequency converter (x2a), (t2b)
When switching the circuit from a state where the circuit is driven by the commercial frequency power supply 00 to direct drive by the commercial frequency power supply 00, the electromagnetic contactor (18a) connected to one of the two groups of variable frequency inverters, for example, the variable frequency inverter (12a). Open circuit and cooler n
After the oil pump motor (3) and fan motor (4) in (2a) have stopped, the electromagnetic contactor (8a) is closed and the cooler group (2a) is started with the commercial frequency power supply, and then the same If you switch the power supply of the cooler group (2b) from the variable frequency inverter (12b) to the commercial frequency power supply OQ according to the procedure,
The cooler groups (2a) and (2b) do not stop at the same time, thus preventing a temperature rise due to loss of cooling oil flow inside the transformer main body, and improving reliability of transformer operation.

In the above other embodiments, the case where the cooler and the variable frequency inverter are configured in two groups has been described, but even when the cooler and the variable frequency inverter are configured in any number of groups of three or more, switching between the variable frequency inverter and the commercial power source can be performed. A similar effect can be expected by not performing this in all groups at the same time.

Furthermore, although the above embodiment describes an oil-feeding air-cooled transformer, the present invention can be similarly applied to an oil-feeding self-cooling type or a cooling method using another cooling medium, such as an oil-feeding water-cooled transformer. You can expect good results.

As explained above, the present invention provides a transformer cooling device that includes a variable frequency inverter, a detection section that detects the operating state of the transformer, and an output frequency of the variable frequency inverter according to the operating state of the transformer detected by the detection section. The control unit is equipped with a switching circuit that switches the drive power source of the cooler to either a variable frequency inverter or a commercial frequency power source under predetermined conditions, so the cooler is driven by the variable frequency inverter under light load conditions. In addition, when the load is close to the rated load, the variable frequency inverter is disconnected and driven directly by commercial power, which eliminates the variable frequency inverter's insertion loss and improves efficiency. be able to.

In addition, in the above transformer cooling system, the cooler and the variable frequency inverter are configured in multiple groups, and by providing a time difference so that switching between the variable frequency inverter and the commercial power source is not performed between multiple groups, when switching the power source of the cooler, It is possible to prevent temperature rise due to loss of cooling oil flow inside the transformer body.

[Brief explanation of drawings]

Figure 1 is a block diagram of the cooling system of a conventional oil-feeding air-cooled transformer, Figure 2 is a block diagram of the cooling system of Figure 1, and Figures 3 and 4 are of a conventional cooling system. A diagram showing an example of operation control conditions, FIG. 5 is a block diagram of a cooling device showing an embodiment of the present invention, and FIGS. 6 and 7 respectively show the W of the cooler, the power frequency, and the cooling capacity of the cooler. FIG. 8 is a block diagram of a cooling device showing another embodiment of the present invention. In the figure, (1) is the transformer body, (2) is the cooler body, (2a) and (2b) are the cooler group, (3) is the oil pump motor, (4) is the fan motor, and (5) is the Detection unit (s)
, (8a), (8b) are electromagnetic contactors, (9) is a no-use circuit breaker, qo is a commercial frequency power supply, OI) is an arithmetic control unit, 02, (i2a), (x2b) is a variable frequency inverter, 03, (18a), (18b)
, is an electromagnetic contactor. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Makoto Kuzuno - Figure 3 01112In - 1)) King) Gamemi t M qga 1 & 2, Figure 4 OTI T2 □ 5 star degree Figure 5 Figure 6 Figure 8 Figure 1

Claims (2)

[Claims] (1) A cooler that forcibly circulates the cooling medium of the transformer using an induction @motor, a detection unit that detects the operating state of the transformer,
A calculation control unit that determines the driving frequency to be supplied to the induction motor according to the signal from the detection unit and generates a frequency command signal, and converts the commercial frequency power source into variable frequency power based on the command signal from the calculation control. a variable voltage variable frequency inverter that converts the induction lightning and drives the induction lightning machine at variable speed; and a power source for driving the induction motor is switched to either the variable voltage variable frequency inverter or the commercial frequency power source depending on the operating state of the transformer. Transformer cooling system with switching circuit. (2) A cooler that forcibly circulates the cooling medium of the transformer using an induction type UJ machine, a detection unit that detects the operating state of the transformer, and a drive that supplies the induction motor to the induction motor in response to a signal from this detection unit. an arithmetic control section that determines the frequency and generates a frequency command signal; a variable voltage variable frequency inverse conversion that converts a commercial frequency power source into variable frequency power based on the command signal from this arithmetic control section and drives the induction motor at variable speeds; a switching circuit for switching the driving power source of the induction motor to either a variable voltage variable frequency inverter or a commercial frequency power source using a driving state board of a transformer; A transformer cooling device characterized in that the converter is constituted by at least two or more units, and the variable voltage variable frequency inverter and the commercial frequency power source are switched at a time difference between the units.