JPS62261107A - Transformer cooling device - Google Patents

Abstract

PURPOSE:To drive the remaining non-trouble accessories at the number of revolution corresponding to a load current, and to contrive to economize in electric power by a method wherein the number of revolution of the accessories is computed from the detected number of nontrouble accessories and the load current, and an inverter is controlled to obtain said number of revolution. CONSTITUTION:When a part of accessories 3 and 4 are in trouble, a control part 6 detects the trouble by close-circuiting an auxiliary contact point 11c, and an inverter 7 is controlled in such a manner that the number of revolutions of the accessories is set at the value in coincidence with the curved line D indicating the number of accessories in operation. When all the accessories are normal and they are driven at the number of revolutions of the point P on the curved line C indicating the number of accessories in normal operation and also when a part of the accessories is in trouble, its operation is suspended, and the number of accessories in operation is reduced, the load factor on the curved line D moves to the point Q, and the number of revolutions of the accessories is increased. When the load factor of the transformer is changed, the number of revolutions of the accessories changes to the number of revolutions at a point on the curved line D corresponding to the load factor appropriate to the above-mentioned change. As a result, when a part of the accessories is in trouble, the number of revolutions of the non-trouble accessories is increased so that the number of revolutions of the accessories in trouble will be compensated, and the required cooling functioning can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a transformer cooling device, and more specifically, to an induction motor for driving an oil pump and a cooling fan, which are auxiliary equipment of a forced cooling type transformer. The present invention relates to a transformer cooling device that changes the rotation speed according to the load current of the transformer.

[Prior art]

FIG. 3 shows a schematic structure of a cooling device in a conventional oil-feeding air-cooled transformer, and FIG. 4 is a block diagram showing a control circuit of the cooling device in FIG. 3. In the figure, l is a transformer consisting of an iron core (not shown), a coil, and insulating oil as a cooling medium, and four groups of coolers 2 each consisting of a cooler body 2a, an oil pump 3, and a cooling fan 4 are arranged in parallel. be.

The insulating oil in the transformer 1 is circulated between the cooler main body 2a and the inside of the transformer 1 by an oil pump 3, and is circulated by a cooling fan 4.
The transformer 1 is cooled by blowing air into the cooler body 2a and cooling the insulating oil passing through the cooler body 2a.

These oil pump 3 and cooling fan 4 are each driven by an induction motor (hereinafter referred to as a motor)! IA! IJ has been done. The load current of the transformer l is detected by a current detection unit 5 such as a bushing current transformer, and the control unit 6 controls the oil pump 3 and the cooling fan 4 according to the load current detected by the current detection unit 5.
A variable voltage variable frequency inverter 7 (hereinafter referred to as inverter) is controlled to change the rotation speed of the motor of the oil feed pump 3 and the cooling fan 4 corresponding to the load current, or This is done based on a pre-stored value of the output frequency of the inverter corresponding to the number. Also oil pump 3. When the cooling fan 4 fails and stops, a failure detection unit 10 connected thereto detects the failure and excites the tripping coil lla of the failure circuit breaker 11. As a result, the power cutoff contact 11b of the faulty circuit breaker opens, and the auxiliary contact 11c closes, causing the failed oil pump 3. Disconnect only the cooling fan 4 from the power supply 8,
The control unit 6 also performs control to detect a failure in the closing of the auxiliary contact 11c, open the power switches 9a and 9b, and then close the power switch 9C. Through this control, the inverter 7 is disconnected from the power supply 8, and the remaining oil pumps 3 and cooling fans 4 that are not broken are connected to the commercial frequency power supply 8.
It is driven at a constant rotation speed.

Note that an overcurrent breaker 12 is interposed between the power switches 9a, 9c and the power source 8.

By the way, the power loss in the transformer 1 is mainly composed of the tr1 loss, which is proportional to the square of the load current, and the iron tQ generated in the iron core, as shown in Fig. 5 (the horizontal axis is the transformer's power loss). The load factor (ratio of the load current to the rated current) is taken as a coordinate, and the vertical axis is the power loss of the transformer, and the curve A is connected to the iron loss value and is shown as a square characteristic.

On the other hand, the cooling capacity of the cooler 2 is approximately 0.8 to the flow rate of the insulating oil.
The flow rate of this insulating oil is proportional to the 1.0th power, and the flow rate of the insulating oil is approximately proportional to the rotational speed of the motor of the oil feed pump 3, resulting in a cooling characteristic shown by a solid line B in FIG. Therefore, based on these characteristics, the rotation speed of the auxiliary equipment that achieves an appropriate cooling effect for the load current of the transformer 1 is:
It is set in consideration of air blowing, as shown by curve C shown by the square characteristic in FIG. 7, which is shown in coordinates where the vertical axis is the rotational speed of the auxiliary equipment and the horizontal axis is the load factor of the transformer.

Therefore, as described above, the control section 6 is stored in advance with the characteristics shown by the solid line C in FIG. 7, and the auxiliary equipment is driven by the voltage of the desired frequency converted by the inverter.

In addition, the voltage ■ supplied to the auxiliary equipment is the frequency F that drives the auxiliary equipment.
It is converted in the inverter 7 so that V/F is constant or V/F'' is constant.

By controlling the rotation speed of the auxiliary equipment in this way,
The power supplied to the auxiliary equipment is approximately the second to third power of the frequency, and operation is performed with significantly reduced power consumption.

[Problem that the invention seeks to solve]

In the conventional transformer cooling device described above, when an auxiliary machine fails, it is disconnected from the power supply and only the auxiliary machines that are not in trouble are driven by commercial frequency voltage. Therefore, while the failure occurs, the auxiliary equipment is operated at a constant rotational speed that is not related to the load current, so there is a problem that the power consumption is wasted.

The present invention provides transformer cooling that allows the remaining non-faulty auxiliary equipment to be driven at a rotation speed commensurate with the load current even when an auxiliary equipment fails, thereby saving power for constantly operating the auxiliary equipment. The purpose is to provide equipment.

Means for Solving Problem c] The transformer cooling device of the present invention includes a current detection section for load current;
A failure detection unit that detects failures in auxiliary equipment and non-faults detected by the failure detection unit? The controller includes a control unit that determines the rotation speed of the auxiliary machine from the number of iR machines and the load current detected by the current detection unit, and controls the inverter to obtain the rotation speed.

[Effect]

The rotational speed of the auxiliary machine is controlled by an inverter and varies in response to the detected load current, thereby preventing unnecessary auxiliary machine operation. If an auxiliary machine breaks down during operation, the auxiliary machine is operated at a rotation speed according to the load current, based on the relationship between the load current and the rotation speed of the supplementary machine, which corresponds to the number of auxiliary machines that are not broken. Therefore, even if some of the auxiliary machines fail, unnecessary auxiliary machine operation is prevented and the auxiliary machine power is saved in the same way as when no auxiliary machines are out of order.

〔Example〕

The present invention will be described in detail below with reference to drawings showing embodiments thereof.

FIG. 1 is a schematic structural diagram of an oil-feeding air-cooled transformer equipped with a transformer cooling device according to the present invention, and FIG. 2 is a block diagram showing the configuration of a transformer cooling circuit according to the present invention.

In FIGS. 1 and 2, 1 is a transformer consisting of an iron core (not shown), a coil, insulating oil as a cooling medium, etc.
This transformer 1 is driven by a cooling 3 main body 2a and a motor on its side, respectively. Four groups of coolers 2, each equipped with an oil pump 3 and a cooling fan 4, are arranged in parallel. The oil pump 3 transfers the insulating oil in the transformer 1 to the cooler body 2.
The cooling fan 4 blows air into the cooler main body 2a to cool the insulating oil flowing through the cooler main body 2a, and cools the transformer 1 by supplying the oil and cooling the transformer 1. Cooling.

5 is a current detection unit for detecting the load current of the transformer l, and the detected load current is input to the control unit 6.

The control unit 6 controls the load current and the rotational speed of the auxiliary equipment (
(or the output frequency of the inverter) or a relational expression for calculating the rotation speed of the auxiliary equipment corresponding to the load current.

In addition, the control unit 6 uses the load current detected by the current detection unit 5,
Inverter control means 6b calculates the number of revolutions of the auxiliary machine (or output frequency of the inverter) according to the number of operating auxiliary machines and the content stored in the storage means 6a, and controls the inverter to obtain this number of revolutions. There is.

Each of the energizing circuits of the oil pump 3 and the cooling fan 4 has a circuit that detects failures of these auxiliary devices by the respective energizing currents.
I detectors 10 are respectively provided, and when the failure detectors 10 detect a failure, the failure fIi! ! ! The tripping coil lla of the disconnector 11 is excited to open the power cutoff contact 11b to disconnect the failed auxiliary machine from the power supply 8, and at the same time close the auxiliary contact 11c. Further, the opening/closing operation signals of the auxiliary contacts 11c in each fault circuit breaker 11 are input to the control section 6, respectively.

That is, the control unit 6 individually detects the breaking operations of the plurality of faulty circuit breakers 11.

The commercial frequency power source 8 is connected to the power cutoff contact 11b of each fault circuit breaker 11 via the overcurrent circuit breaker 12, the power switch 9a, the inverter 7, and the power switch 59b. A connection point between the overcurrent cutoff ri12 and the power switch 9a,
A power switch 9C is connected between the connection point between the power switch 9b and the power cutoff contact 11c.

In the transformer cooling device configured in this way, the control unit 6 controls the power switches 9a and 9b to close and the power switch 9C to open, and the impark control means 6b of the control unit 6 controls the impark. 7, the auxiliary equipment is driven at a required rotation speed, and the transformer 1 is cooled by oil supply and air cooling.

When all the auxiliary machines are normal, the transformer 31 is cooled by a cooling effect corresponding to the load.

By the way, when some of the auxiliary machines fail, the control unit 6 detects the failure by closing the auxiliary contact 11c. The relationship between the load factor and the rotational speed of the auxiliary devices currently stored in the storage means 6a for the number of remaining auxiliary devices is the curve shown by the broken line in FIG. If the rotational speed of the auxiliary machine is below the value indicated by the load factor (corresponding to the capacity), the control unit 6 controls the inverter 7 to set the rotational speed of the auxiliary machine to a value that follows this curve. This maintains the same cooling capacity as before the auxiliary equipment failed.

Now, if all the auxiliary machines are normal and are being operated at the rotation speed of point P on curve C, some of them? When #IJIl fails and the operation is stopped and the number of units in operation is reduced, the number of rotations of the auxiliary equipment is increased by moving to point Q on the curve with the same load factor. When the load factor of the transformer changes, the rotation speed at a point on the curve changes in accordance with the corresponding load factor. In this manner, when a part of the auxiliary equipment breaks down, the number of rotations of the non-faulty auxiliary equipment is increased to compensate for the number of revolutions corresponding to the failure, thereby obtaining the same cooling effect. In addition, the rotational speed of the auxiliary equipment changes continuously according to the load factor, regardless of the failure of the auxiliary equipment.

Therefore, even when some of the auxiliary machines are out of order, the rotational speed of the non-faulty auxiliary machines is increased, and operation can be performed with reduced power consumption even when some of the auxiliary machines are out of order.

Note that the control unit 6 also performs control to open the power switches 9a and 9b and close the power switch 9c, but in this case, the auxiliary equipment is driven by the commercial frequency power source 8 at a constant rotation speed. become.

〔effect〕

As described in detail above (according to the present invention, even if an auxiliary machine fails and the number of auxiliary machines in operation decreases, the rotation speed of the auxiliary machine is changed to the load current corresponding to the number of operating auxiliary machines that are not in trouble). In addition, the auxiliary equipment is always operated at a rotation speed commensurate with the load current of the transformer, regardless of whether or not there is a failure in the cooler, which has the excellent effect of constantly saving the power supplied to operate the auxiliary equipment. .

[Brief explanation of drawings]

FIG. 1 is a schematic structural diagram of an oil-feed air-cooled transformer equipped with a transformer cooling device according to the present invention, FIG. 2 is a block diagram showing an electric circuit of the transformer cooling device of the present invention, and FIG. A schematic structural diagram of a conventional oil-feeding air-cooled transformer, Figure 4 is a schematic diagram showing the electric circuit of a conventional transformer cooling system, and Figure 5 shows the relationship between the transformer load factor and power loss. Figure 6 is a graph showing the relationship between oil pump rotation speed and cooling capacity, and Figure 7 is a graph showing the relationship between the transformer load factor and ? It is a graph showing the relationship with the rotation speed of the 'ili machine. 1...Transformer 2...Cooler 3...Oil pump (Jili machine) 4...Cooling fan (auxiliary equipment) 5...
- Current detection section 6... Control section 7... Variable voltage variable frequency inverter 10... Fault detection section 11... Fault circuit breaker Note that in the drawings, the same reference numerals indicate the same or equivalent parts. Samurai Akira Applicant Mitsubishi Electric Co., Ltd. Agent Patent Attorney Masuo Oiwa and 2 others l・-Transformer? ...Cold #11! Figure 1 Figure 2

Claims (1)

[Claims] 1. The number of rotations of a plurality of auxiliary machines driven by an induction motor,
In a transformer cooling device that is controlled by an inverter according to the load of the transformer, a current detection section that detects the load current of the transformer, a failure detection section that detects a failure of the auxiliary equipment, and an output of the failure detection section are provided. a control unit that determines the rotational speed of the auxiliary equipment corresponding to the required cooling capacity from the number of non-faulty auxiliary equipment detected and the load current detected by the current detection unit, and controls the inverter to obtain this rotational speed; A transformer cooling device characterized by comprising: