JPH01157228A - Power-saving and regulated voltage feed system - Google Patents

Abstract

PURPOSE:To feed stable voltage, by connecting a capacitor to a space between an incoming end and a load so that the voltage of high tension incoming voltage stepped down so that the voltage of a load end may be turned into safety voltage or higher, cannot to dropped to come to the safety voltage or lower by great current. CONSTITUTION:From a high tension incoming end, via a switch 11, a breaker 14, a voltage regulating transformer 15, a switch 16, and a step-down transformer 18, power is fed to a plurality of loads 23. By the voltage regulating transformer 15, the input voltage of the loads 23 is regulated to be slightly higher than safety voltage. To a space between the loads 23 and the step-down transformer 18, a capacitor 19 is connected. The capacitor 19 is composed of a capacitor 31, a breaker 35, and an arrester 36 connected to the secondary side of a primary side and a secondary side reactors 32, 33 wound on a core with a gap. As a result, the inductive reactances of a line and a transformer in a power demander's yard are cancelled together, and voltage drop due to the starting current of an induction motor is suppressed, and wasteful power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power-saving and stable voltage supply system.

[Conventional technology and its problems]

In general, in-house power demand facilities such as factories and buildings are mainly composed of inductive loads. Therefore, the supply voltage for the load should be set higher than the appropriate voltage for the normal stable load demand, in anticipation of the voltage drop in the line and transformer due to the large starting current of the induction motor, etc. The reality is that failures caused by voltage drops during transients are avoided.

FIG. 2 is a diagram for explaining the concept of such a flexible supply voltage setting, and shows the distribution state of voltage drops due to the power system and lines in the premises of a high-voltage power consumer.

In the figure, 1 is a circuit breaker at the power receiving point of a high-voltage power consumer, 2
is a voltage regulating (!Is voltage) transformer (e.g. 6600
V-6000V), 3 is a high voltage line, 4 is a transformer for converting high voltage to low voltage (for example, 6000 V → 200 or 100 V), 5 is a low voltage line, and 6 is a load. The voltage E on the secondary side of the voltage regulating transformer 20 (hereinafter referred to as power supply voltage) is lowered by the impedance of the line 3.5 and the transformer 4, and is supplied to the load 6. In the figure, e is the voltage drop value during steady operation, and e! indicates the additional voltage drop value due to large current such as the starting current of the induction motor.

Generally, a peak load current such as a starting current of an induction motor has an extremely poor power factor, and the voltage drop at the inductive reactance of the transformer 4 is increased to a greater extent than that caused by a high power factor current, resulting in a large voltage drop rate.

Under such circumstances, according to the general voltage setting described above, the voltage supplied to the load is set to be high in anticipation of the voltage drop value e2. Therefore, the load is operating at a considerable overvoltage compared to the steady load operation. Generally, power consumption is proportional to the square of the voltage, so a considerable amount of power is expected to be wasted.

On the other hand, the capacity of electric motors and other mechanical equipment is set with considerable leeway.

Therefore, even if the output of the motor etc. decreases due to a slight voltage drop, there is still sufficient output margin for the load on the machinery and equipment, and the settings are set so as not to cause any problems to the operation. ing. In this specification, a supply voltage that does not cause any problems is referred to as a safe voltage value.

Taking this into account, it has been demonstrated in many actual sites that even if the supply voltage to the load is reduced by about 10% from the current value, as long as the voltage does not drop below the safe voltage value, the machinery and equipment will function without any problems. However, in the current state, there is no problem in operation with a steady load as mentioned above, but the instantaneous voltage drop in response to a transient sudden large current is much more severe, and the lower voltage side Therefore, if the voltage drops below the safe voltage value, a failure will occur. Therefore, overvoltage operation still cannot be avoided.

On the other hand, the number of loads that require strict voltage quality among power consumers is increasing. In such a case,
Inductive reactance in transformers or lines is undesirable because it causes voltage fluctuations.

The purpose of the present invention is to solve the above-mentioned problems, reduce power consumption by avoiding overvoltage operation, and provide a power-saving and stable voltage supply system that supplies a stable voltage without voltage fluctuations to a load. Our goal is to provide the following.

[Means for solving problems]

The present invention is a power-saving and stable voltage supply system that reduces the power consumption of high-voltage power consumers and supplies a stable voltage with no fluctuations to the load, and provides a set supply where the voltage at the load end is higher than the safe voltage value. a voltage step-down device that steps down the received voltage so that the voltage is the same as the current voltage;
It has a capacitor device provided in the electric path from the power receiving end to the load end.

[Effect]

The principle of the present invention will be explained with reference to FIG. Third
The figure corresponds to FIG. 2 and shows the power system and voltage drop distribution in the premises of a high voltage consumer. In FIG. 3, the same elements as in FIG. 2 are designated by the same reference numbers.

According to the present invention, the capacitor device 7 is provided in the electric path between the power receiving end and the load end, and the inductive reactance of the line 3.5 and the inductive reactance of the transformer 4 are offset by the capacitive reactance of the capacitor. The voltage drop due to these inductive reactances is compensated for. This is the concept of the so-called series capacitor compensation method, but the series capacitor compensation method has the problem that if the series capacitor causes an open failure due to element destruction, power cannot be supplied to the load. In the case of the present invention, the power supply can be continued even if the capacitor causes an open failure.

As described above, the capacitor device 7 cancels out the inductive reactance of the high voltage line 3, transformer 4, and low voltage line 5, and the voltage drop becomes only the voltage drop due to the resistance. In the figure, e,
indicates a voltage drop value during steady operation, and e4 indicates an additional voltage drop value due to a large current such as the starting current of an induction motor. The voltage drop due to the inductive reactance of the line 3.5 and the transformer 4 can be compensated immediately for any value of load current by using a capacitor device, so the voltage drop value e4 is equal to the voltage drop value e2 in Fig. 2. It can be made much smaller than the .

Therefore, even when the supply voltage to the load, , the problem of overvoltage supply to the load mentioned above is solved. As a result, unnecessary power demand is removed, and power can be used with appropriate power savings.

Further, according to the present invention, since the inductive reactance of the line and the transformer is canceled by the capacitor device, it is possible to supply a stable voltage to the load without voltage fluctuations due to inductive reactance.

〔Example〕

The present invention will be explained in detail below.

FIG. 1 shows a power-saving and stable voltage supply system for a high-voltage power consumer's premises, which is an embodiment of the present invention.

In the figure, 11 is a switch, 12 is an instrument switching switch, 13 is a voltmeter for measuring the receiving voltage, 14 is a circuit breaker, 15 is a voltage adjustment transformer, 16 is a switch, 18 is a transformer, and 19 is a Capacitor device, 20 is an instrument switching switch, 21 is a voltmeter for measuring load voltage, 22 is a circuit breaker (or knife switch)
, 23 is a load including an induction motor and the like.

The voltage regulating transformer 15 is a transformer that steps down the received voltage, and is set so that the voltage supplied to the load 23 is slightly higher than a safe voltage value. Transformer 18 is a transformer that reduces high voltage to low voltage. In this embodiment, 2 of the transformer 18
Although the capacitor device 19 is installed on the next side, it may be installed on the primary side.

The voltage regulating transformer 15 can adopt any of a fixed tap type, a no-voltage tap switching type, and an on-load tap switching type.

Figure 4 shows (a) to (c) using an autotransformer.
Fixed tap method, no-voltage tap switching method, and on-load tap switching method are shown.

In the fixed tap method shown in FIG. 4(a), for example, 6600
The tap is fixed to step down V to 6000V.

In the no-voltage tap switching method shown in Figure 4(b), the receiving voltage (
Load 2
Tap switching is performed in a no-voltage state so as to maintain the supply voltage to 3 constant. In this case, the reception voltage is detected by the voltmeter 13.

The on-load tap switching method shown in Figure 4 (C) is the switch ■~
It has a reactor to switch taps. In this case, the receiving voltage is detected by the voltmeter 13, and the load voltage is detected by the voltmeter 21.

The table below shows an example of switch operation for tap switching at load.

Next, the capacitor device 19 in this embodiment will be explained in detail.

FIG. 5 shows the basic configuration of the capacitor device.

The capacitor device includes a reactor 30 and a capacitor 31. A primary winding 32 of the reactor 30 is inserted into the low voltage line 25, and a capacitor 31 is connected to the secondary winding 33. By inserting the capacitor through the reactor in this way, the shortcomings of the conventional series capacitor compensation method are improved, and even though the voltage drop cannot be compensated for when the capacitor 31 fails (open or short circuit), it The supply can be continued m times.

As described above, simply connecting a capacitor to the secondary side of the reactor 30 will induce a large voltage on the secondary side of the reactor when a large current flows, such as when starting a large-capacity induction motor. If this exceeds the insulation resistance of the capacitor 31, there is a risk that the capacitor will be destroyed. Therefore, it is necessary to provide appropriate protection measures during actual use.

FIG. 6 shows an example of a capacitor device with protection means. This capacitor device uses a reactor with a gap 34 as a reactor, and a circuit breaker 3 is connected in parallel to the capacitor 31.
5 and an arrester (lightning arrester) 36 are provided. According to this capacitor device, the primary winding 32 of the reactor 34
When a large current flows through the secondary winding 33 and a high voltage is generated in the secondary winding 33, the arrester 36 is discharged or the circuit breaker 35 is closed to prevent an open or short circuit from occurring in the capacitor 31. . If these protection functions do not work properly and an open failure occurs in the capacitor 31, the secondary side of the beam handle 34 will be in an open state. In such a case, in the case of a normal glue handle without a gap, the iron core will become magnetically saturated and a sharp wave voltage will be generated, which will threaten the insulation of power equipment and lead to an extremely dangerous situation. However, since the reactor has a structure in which a gap is provided in a part of the reactor to increase magnetic resistance, magnetic saturation does not occur even with any current conduction, and the generation of the above-mentioned sharp wave voltage can be prevented.

FIG. 7 shows another example of a capacitor arrangement with more complex protection means. In this capacitor device, a reactor 30 is provided with a tertiary winding 37, and a manual switch 38 and an electromagnetic switch 39 for short-circuiting the tertiary winding are connected to the tertiary winding.

On the other hand, the neutral point of the secondary winding 33 of the reactor 30 is grounded, and the voltage detection circuit 40 is connected between the neutral point and a suitable tap. Further, an arrester (lightning arrester) 41 is provided in parallel with the capacitor 31. Further, a current transformer 42 is provided in series with the capacitor 31, and a current transformer 43 is provided in series with the arrester 41.

The electromagnetic switch 39 is controlled by an electromagnetic switch control circuit 44, to which the outputs of the voltage detection circuit 40 and current transformers 42 and 43 are input.

In such a capacitor device, when the capacitor 31 is operated normally, both the manual switch 38 and the electromagnetic switch 39 are kept open.

When the capacitor 31 is not activated, if the manual switch 38 is closed, a current based on the induced electromotive force flows through the tertiary winding 37 to generate magnetic flux, and this magnetic flux is transferred to the primary winding 32.
cancels the generated magnetic flux. Therefore, the secondary side circuit of the reactor 30 does not work, and when viewed from an equivalent circuit, the capacitor 31 is in the same state as if it were short-circuited.

1 of the reactor 30 when the manual switch 38 is in the open state.
When a large current flows through the secondary winding 32, the voltage induced in the secondary winding 33 increases. The voltage detection circuit 40 detects this induced voltage and sends it to the control circuit 44. The control circuit 44 controls the electromagnetic switch 39 to close when the induced voltage exceeds a predetermined value. When the electromagnetic switch 39 is closed, similar to the operation when the manual switch 38 is closed, no induced voltage is generated in the secondary winding 33, and therefore the capacitor 31 can be protected from destruction due to high voltage.

This capacitor device provides double protection in case the voltage detection circuit 44 does not operate normally. That is, when a high voltage is applied to the capacitor 31, the arrester 41 discharges it to lower the voltage, and the current transformer 43 detects the discharge current and sends it to the control circuit 44 to close the electromagnetic switch 39. . Also, capacitor 3
1 causes a short circuit failure for some reason, the current transformer 42 detects the short circuit current, sends it to the control circuit 44, and closes the electromagnetic switch 39. As a result, as described above, the secondary circuit of the reactor 30 no longer functions electrically, so it is essentially the same as disconnecting the faulty capacitor 31 from the circuit.

Furthermore, if the reactor 30 is provided with a gap, it is possible to prevent the generation of a sharp wave voltage when the secondary side is opened as described above.

FIG. 8 shows another embodiment of the invention. This embodiment uses a voltage regulator 50 that has the functions of both a voltage step-down device and a capacitor device. Accordingly, the capacitor arrangement 19 of FIG. 1 has been removed, and the rest of the structure is similar to that of FIG. 1, and identical components have been designated with the same reference numerals.

FIG. 9 shows an example of the configuration of the voltage regulator 50.

A switching tap 52 is provided on the excitation side (primary side) of the series transformer 51, and a capacitor 53 is connected to it. Also, tap 5
A switch 54 is provided to enable switching at the time of two loads. In terms of an equivalent circuit, since the capacitor 53 is inserted in series in the electric line, the vA lines 24 and 25 and the transformer 18
The capacitor device functions similarly to the capacitor device of FIG.

In this voltage regulator, if the capacitor 53 fails and the failure is a short-circuit failure, the capacitor does not function, but the device operates normally and can supply power to the load. On the other hand, in the case of an open circuit failure due to element destruction, the series transformer 51 does not function, but power can be supplied to the load with a voltage drop equal to the voltage drop across the secondary winding of the series transformer. Therefore, power can be supplied regardless of a failure of the capacitor 53, allowing safe operation.

Tap switching during load is performed by turning on the switch 54 to short-circuit the capacitor 53, switching the tap 52 during this time, and turning off the switch 54 after switching is completed. This on-load tap switching allows the voltage supplied to the load to be maintained constant, regardless of temporal fluctuations in the received voltage or voltage fluctuations due to increases and decreases in the load on the premises.

According to each of the embodiments described above, as explained in the [Operation] section, the inductive reactance of the high-voltage distribution line 24, the low-voltage distribution line 25, and the transformer 1B is canceled out by the capacitive reactance of the capacitor. Since the voltage drop due to the large starting current of the induction motor is reduced, stable operation is possible without causing any trouble at the time of large current even if a voltage lower than the rated voltage of the load is supplied. therefore,
Power consumption can be reduced by lowering the voltage applied to the load. Furthermore, since there is no voltage fluctuation due to inductive reactance, a stable voltage supply to the load is possible.

〔Effect of the invention〕

As explained above, according to the present invention, the inductive reactance of the line and transformer in the power consumer's premises is offset by the capacitor, so when a large current such as the starting current of an induction motor flows, Since the voltage drop caused by this can be reduced, the voltage supplied to the load can be lowered one step below the current value using a voltage regulator, etc. at the receiving end, and unnecessary power consumption can be suppressed. It becomes possible.

In addition, since the inductive reactance is offset by the capacitive reactance of the capacitor, there is no voltage fluctuation due to inductive reactance (and a stable voltage can be supplied to the load).

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the problems of the prior art, FIG. 3 is a diagram for explaining the present invention in detail, and FIG. The figure is a diagram showing various tap switching systems of the voltage regulating transformer in Figure 1. Figures 5 to 7 are diagrams each showing configuration examples of the capacitor device in Figure 1. FIG. 9, a diagram showing another embodiment of the invention, is a diagram showing an example of the configuration of the voltage regulator shown in FIG. 8. 15... Voltage adjustment transformer 19... Capacitor device 30... Reactor 31, 53... Capacitor 34... Reactor with gap 35... Circuit breaker 36, 41... Arrester 38... Manual switch 39... Electromagnetic switch 40... Voltage detection circuit 44... Electromagnetic switch control circuit Agent Patent attorney Yoshiyuki Iwasa Age → Fig. 2 re female → Fig. 3 (a) (b) (C) Fig. 4 Fig. 5 Fig. 6 Fig. 8

Claims (1)

[Claims] (1) A power-saving and stable voltage supply system that reduces the power consumption of high-voltage power consumers and supplies stable voltage without fluctuation to the load, with a set supply voltage where the voltage at the load end is higher than the safe voltage value. In order to prevent the set supply voltage from falling below the safe voltage value due to a voltage drop due to large current, a step-down device is installed in the electrical path from the power receiving end to the load end. A power saving system with a capacitor device
Stable voltage supply system.