JPH10174293A - Opening/closing circuit of capacitor for improvement of power factor in cooperative operation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the optimum release and remake of every capacitor unit by providing an auxiliary relay with a voltage adjusting means which lowers the application voltage to the second given specified voltage or under, when the voltage on low voltage side drops to the first given voltage. SOLUTION: To an opening and closing circuit 100a, an auxiliary relay 74 and a means 75 to adjust the application voltage to the auxiliary relay 74 are connected in series, in parallel with an exciting coil 73. Then, when the voltage on low voltage side of an in-line transformer drops to 80% or under of the rated voltage, the auxiliary relay 74 is energized, and a contact 74a is opened, but when the voltage of the self power generation system recovers to 80% or over of the rated voltage, the voltage above specified operation voltage is applied to the auxiliary relay 74, so the contact 74a is closed. Hereby, an opening delay type timer relay 76 once de-energized is biased, and the contact 76a is kept closed, so an exciting coil 73 is biased again, and an opening/closing switch 61 is turned on, and a capacitor C1 for improvement of power factor is turned on again. As a result, the optimum release and the remake of very capacitor unit can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching circuit for a power factor improving capacitor in a system for interconnecting a commercial power system and a private generator.

[0002]

2. Description of the Related Art Recently, customers have been equipped with private power generation facilities,
There is a tendency to increase the number of cases of interconnecting operation with the commercial power system, but from the viewpoint of effective use of electric power and prevention of harmonic outflow, a power factor improving capacitor facility is installed on the secondary side (low voltage side) of the on-premise transformer. The operation is performed such that the power factor at the power receiving point approaches 1 as much as possible.

In such a system operation, when a disturbance such as a short circuit accident or an instantaneous voltage drop occurs on the side of the commercial power supply system, the consumer operates the private power generation equipment separately from the commercial power supply system, and with respect to an important load, In some cases, an operation method in which the power supply from the private power generation equipment is continued is employed. According to this method, the power supply to the load can be performed without interruption, so that the reliability of the power supply is significantly improved.

[0004]

However, when the power system fluctuates, a transient phenomenon such as amplification of residual voltage in the premises due to the power factor improving capacitor may occur, whereby the protection relay for grid connection operates reliably. Conventionally, an undervoltage relay that operates at a speed of 85 to 80% of the rated voltage at high speed (about 0.1 to 0.2 seconds) is installed at the receiving point, and a protection relay for grid connection is provided. Before operation, the capacitor is opened at high speed to ensure that the protection relay for system interconnection is operated.

On the other hand, recently, there has been proposed a system in which a power factor improving capacitor is installed on the low voltage side of the premises, also as a harmonic countermeasure aiming at suppressing harmonic components generated from a load,
It is also recommended in the guidelines. FIG. 7 shows a circuit configuration of an interconnected operation system of this type, wherein 1 is a commercial power supply, 2 is a power receiving circuit breaker, 3 is a power receiving transformer, 41 and 42 are local (low-voltage) transformers, and 5 is a system. The private-use generators G, C1, and C2 that are connected to each other are power factor improving capacitors connected in parallel to the load 1 and the load 2 on the low voltage side, respectively, and 61 and 62 are open / close of the respective power factor improving capacitors C1 and C2. 7 is a high-speed undervoltage relay installed at the receiving point A, 8 is a protection relay for linking the system also installed at the receiving point A, and 10 and 11 are switching circuits for opening and closing the opening and closing switches 61 and 62, respectively. It is.

In this system, an electromagnetic switch is generally used for the on / off switches 61 and 62 of the power factor improving capacitors C1 and C2, and a low-voltage transformer 41 is used as a control power supply for driving the electromagnetic switch. , 42 is used as it is, and is not automatically opened unless the voltage drops to about 50% of the steady state, so that the capacitor is forcibly applied by the output of the high-speed undervoltage relay 7 installed at the receiving point A. Open to the public.

FIG. 8 shows an example of such a conventionally known switching circuit for a power factor improving capacitor.

[0008] The low voltage transformer 41 is provided in the power receiving circuit of the interconnection system.
(See FIG. 7) on the low voltage side (for example, 210 V)
A series reactor L1, a power factor improving capacitor C1, and an opening / closing switch 61 thereof are connected in series via a (no-fuse breaker) 60 in parallel with a local load (not shown).

The switching circuit of the power factor improving capacitor C1 will be described. The switching circuit 10 uses a low-voltage side as a control power source, and includes a normally closed contact (b contact) 71 and a normally open contact (a
A contact 72) and an exciting coil 73 of the on / off switch 61 are connected in series, and a self-holding normally-open delay contact 73a that is closed after the exciting coil 73 is energized is connected in parallel with the normally-open contact 72. It is connected.

During system interconnection, when a power factor control circuit (not shown) outputs a "turn on" command for a power factor improving capacitor, the normally open contact 72 is closed, thereby energizing the exciting coil 73. You. As a result, the open / close switch 61 is closed, and the power factor improving capacitor C1 is turned on. At the same time, the delay contact 73a is closed,
Even if the command is not output and the normally open contact 72 is opened again, the exciting coil 73 is continuously energized by the delay contact 73a, and the open / close switch 61 is kept closed.

When an instantaneous voltage drop occurs on the commercial power supply system side, this is detected by a high-speed undervoltage relay 7 connected to a power receiving point A (see FIG. 7), and is detected by 0.1 to 0.2. An "open" command for the power factor improving capacitor C1 is output in a time period of about seconds. As a result, the normally closed contact 71 is opened and the exciting coil 73 is deenergized, so that the open / close switch 61 is opened, and immediately thereafter, the self-holding delay contact 73a is also opened.

In order to separate the power factor improving capacitor C1 and the reactor L1 as described above, a sequence for the separation is required, and in order to execute such a sequence, a capacitor is installed at each location. The control circuit is complicated because the control wiring is connected between the low-voltage board where the capacitor open / close switch, that is, the electromagnetic switch is installed, and the power receiving board placed near the power receiving point. There is.

On the other hand, if the power factor improving capacitor is disconnected when the private power generation equipment is separated and operated, the operating power factor of the private power generator rapidly decreases from a steady operation point of about 0.95 to 0.8 or less. Because of this, the reactive power burden of the generator increases, the automatic voltage regulator (AVR) of the generator cannot follow, the voltage of the generator drops, and the undervoltage relay (70% of the rated voltage, (Approximately 2-3 seconds) and the generator may trip.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been described in an interconnected operation system of a commercial power supply system and a private power generation facility, in which a control is provided between a power factor improving capacitor installed on a low voltage side and a power receiving point. It is an object of the present invention to provide a power factor improving capacitor switching circuit that does not require wiring and a control circuit for the capacitor and that can be optimally released and reconnected for each capacitor unit using an inexpensive relay.

[0015]

According to one aspect of the present invention, a commercial power supply system and a private power generation system are connected to each other to improve the power factor on the low voltage side of a private transformer. A capacitor is installed, and disconnects the power factor improving capacitor when the low voltage side output voltage of the private transformer drops to a first predetermined voltage equal to or lower than a rated voltage when the commercial power supply system is shaken, and In an interconnection operation system in which a private power generation facility is separated and operated by a system interconnection protection relay, an excitation coil for turning on / off an on / off switch of a power factor improvement capacitor installed on a low voltage side, and the excitation coil First and second contacts connected in series and opened and closed based on a power factor control command, and a third contact connected in parallel with the first contact.
And the low voltage side voltage of the private transformer is the first voltage.
An auxiliary relay that is deenergized by applying a second predetermined voltage lower than the first voltage when the predetermined voltage is reached, and when the low-voltage side voltage of the in-plant transformer falls to or below the first predetermined voltage. And an applied voltage adjusting means for reducing an applied voltage so that a voltage equal to or lower than the second predetermined voltage is applied to the auxiliary relay.

In another aspect of the present invention, the commercial power supply system and the private power generation facility are connected to each other, and a power factor improving capacitor is installed on the low voltage side of the private transformer. When the low-voltage output voltage of the on-premise transformer drops to a first predetermined voltage that is equal to or lower than the rated voltage, the power factor improving capacitor is disconnected, and the commercial power system and the private power generation equipment are separated and separated by a system interconnection protection relay. In an interconnected operation system configured to operate, an excitation coil for turning on / off an open / close switch of a power factor improvement capacitor installed on a low voltage side, and an excitation coil connected in series with the excitation coil, based on a power factor control command. A first and a second contact connected in series to be opened and closed, and a second lower than the first predetermined voltage when a low-voltage side of the in-plant transformer becomes the first predetermined voltage. An auxiliary relay constant voltage is de-energized is applied, a third that is closed when the auxiliary relay is energized
And an open-delay timer relay and its open-delay contact connected in series with the third contact, and the auxiliary when the low-voltage side voltage of the private transformer falls below the first predetermined voltage. An applied voltage adjusting means for lowering an applied voltage so that a voltage equal to or lower than the second predetermined voltage is applied to the relay; and a series connection series of the third contact and the open delay contact is connected to the first contact. A contact is connected in parallel, the auxiliary relay and the applied voltage adjusting means are connected in series, and this series connection is connected in parallel to a series connection of the third contact and the open delay timer relay. It is a thing.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a switching circuit for a power factor improving capacitor according to the present invention, in which the same reference numerals as those in FIG. 8 denote the same components.

The circuit configuration of the switching circuit 100a includes a power factor improving capacitor C1 connected in parallel with a load (not shown).
, A series connection row of the reactor L1 and the on / off switch 61, a normally connected contact 71, a normally open contact 72, a series connection row of the exciting coil 73 of the on / off switch 61, and a parallel with the normally open contact 72. Is connected to a normally-open contact 74a for self-holding, and furthermore, an auxiliary relay (R
1) 74 and means 75 for adjusting the voltage applied to the auxiliary relay 74 are connected in series. When the auxiliary relay 74 is excited, the normally open contact 74a is closed. One end of each of the exciting coil 73 and the auxiliary relay 74 is connected.

FIG. 2A or FIG. 2B shows a specific configuration of the applied voltage adjusting means 75 of the switching circuit.

FIG. 2A shows an example in which the applied voltage adjusting means 75 is constituted by a silicon dropper D comprising a plurality of silicon rectifiers. Since the silicon dropper D can secure a voltage drop of 0.7 V in one stage, in consideration of the voltage at which the auxiliary relay 74 is turned off, the necessary number of silicon droppers are connected in series as shown to adjust the applied voltage. What is necessary is just to make the voltage part to drop by means 75. For example, the auxiliary relay 74 is turned on (energized) at a rated voltage of 210 V at 60% of the rated voltage, that is, at 126 V or more, and is turned on at 50 V of the rated voltage.
When an auxiliary relay having a hysteresis characteristic that is turned off (disabled) at a voltage of 105% or less, that is, is turned off (disabled) below 80% of the rated voltage (for example, 210 V), that is, 168 V or less, the on / off switch of FIG. At this time, when the auxiliary relay 74 is opened,
May be made to be 105 V or less. For example, to apply 103 V, 1
As can be seen from 68V-103V = 65V, the applied voltage adjusting means 75, that is, the silicon dropper D connected in series
Is 65 V. Therefore,
It suffices to connect 65 silicon rectifiers of 65 V / 0.7 / 93 in series.

FIG. 2B shows an example in which the applied voltage adjusting means 75 is composed of a resistor.

As in the example of FIG. 2A, when the voltage of the commercial power supply system drops to 80% of the rated voltage (for example, 210 V), that is, 168 V or less, the voltage applied to the auxiliary relay 74 becomes 105 V or less. The resistance value of the resistor R may be determined as described above.

Next, the operation of the switching circuit shown in FIG. 1 will be described with reference to FIG.

FIG. 3 shows changes in the voltage of the commercial power supply system and the voltage applied to the auxiliary relay 74, and the states of the auxiliary relay, the exciting coil, and each contact.

In a state where the low-voltage side V ₀ of the private transformer is at or near the rated voltage (at least 80% of the rated voltage), at time t ₁ , a power factor control circuit (not shown) supplies a power factor improving capacitor When the "ON" command is output for a short time, the normally open contact 72 is closed. As a result, the exciting coil 73 is energized, so that the open / close switch 61 is turned on, and the power factor improving capacitor C1 is turned on. In this state, since the supply voltage V ₀ from the commercial power supply system is also applied to the series circuit of the applied voltage adjusting means 75 and the auxiliary relay 74, the voltage drop by the applied voltage adjusting means 75 is applied to the auxiliary relay 74. (For example, 65V)
A voltage V ₇₄ (for example, 145 V) that is subtracted by only V is applied. Since the applied voltage V ₇₄ is, of course, a value equal to or higher than the operating voltage (for example, 126 V) of the auxiliary relay 74, the auxiliary relay 74 is energized, and as a result, the normally open contact 74a is closed. This is a self-holding function. Even if the normally-open contact 72 is opened immediately thereafter, the excitation coil 73 is continuously energized by the self-holding function of the normally-open contact 74a, so that the open / close switch 61 is kept on. Is done.

At time t ₂ , the low voltage side voltage V ₀ of the private transformer is 80% of the rated voltage (for example, 210 V).
Thereafter, when the voltage drops to, for example, 165 V, the voltage drop by the applied voltage adjusting means 75 is reduced to, for example, 65 as described above.
If the voltage is set to V, the voltage applied to the auxiliary relay 74 becomes 100 V, so that the auxiliary relay 74 is deenergized. As a result, the normally open contact 74a that has been closed is opened, whereby the exciting coil 73 is deenergized and the open / close switch 61 is turned off. That is, the power factor improving capacitor C
1 is released.

According to the present embodiment, as can be seen from the above circuit operation, the auxiliary relay is simply used without using the high-speed undervoltage relay 7 installed at the power receiving point A (see FIG. 7) as in the prior art. With only inexpensive circuit elements such as 74, its contact 74a and the applied voltage adjusting means 75, the power factor improving capacitor can be reliably disconnected when the voltage of the power supply system drops to about 80% of the rated voltage.

Next, another embodiment of a switching circuit for a power factor improving capacitor according to the present invention will be described with reference to FIG.

In the second embodiment shown in FIG. 4, when the self-generating system voltage recovers within a short time after the separation operation, the power factor improving capacitor is re-input to share the reactive power of the private power generation. It is intended to prevent the private generator from tripping by reducing it.

The circuit configuration of the switching circuit according to this embodiment is basically the same as that of the first embodiment shown in FIG. 1, but an open delay timer relay (R2).
A normally open contact 7 for self-holding
4a and the configuration of the applied voltage adjusting means are new. The open delay type timer relay 76 is a timer relay of a type that, when deenergized, opens its contact 76a with a delay of a certain time (for example, 3 seconds).

The new applied voltage adjusting means 75 'is shown in FIG.
As shown in (a) and (b), the basic configuration is shown in FIG.
It is the same as that shown in (a) and (b) except that 30% of the total voltage drop by the applied voltage adjusting means.
In order to bypass a portion corresponding to%, a normally closed contact 74b of the auxiliary relay 74 is provided. That is, as shown in FIG. 5A, in the example in which the applied voltage adjusting means is constituted by a silicon dropper, 70% of the total voltage drop.
% With silicon dropper D1 and the remaining 30%
And the normally closed contact 74b of the auxiliary relay 74 is connected in parallel with the latter.

As shown in FIG. 5B, in the example in which the applied voltage adjusting means is constituted by a resistor, 7% of the total voltage drop is used.
0% is assigned to the resistor R1, and the remaining 30% is assigned to the resistor R2. The normally closed contact 74b of the auxiliary relay 74 is connected in parallel with the latter.

Next, the circuit operation of the switching circuit in this embodiment will be described with reference to FIG. When the steady-state operation is performed in a state where the low-voltage side V ₀ of the private transformer is close to the rated voltage (for example, 210 V), at time t ₁ , the power factor control circuit outputs a “turn-on” command for the power factor improving capacitor C 1. Then, the normally open contact 72 is closed. As a result, since the exciting coil 73 is energized, the open / close switch 61 is turned on, and the power factor improving capacitor C1 is turned on.
Since the open delay timer relay 76 is also energized, its open delay contact 76a is closed. Thereby, the auxiliary relay 74
And the normally open contact 74a is closed.

Assuming that the low-voltage of the private transformer drops to, for example, 80% or less of the rated voltage at time t ₂ , the auxiliary relay 74 is deenergized as described in the first embodiment. The contact 74a is opened. As a result, the open delayed timer relay 76 is de-energized, its open delay contact 76a should be opened without opening immediately, for example, at time t ₄ after three seconds. However,
At time t ₃ (for example, two seconds after time t ₂ ) before that,
Assuming that the private power generation system voltage has recovered to, for example, 80% or more of the rated voltage by the separated operation of the private power generation equipment, the delay relay 76a is still closed at that time, so that the auxiliary relay 74 has a voltage higher than the specified operating voltage. Is applied, and is energized to close the contact 74a. Remains thereby temporarily de-energized to open delayed timer relay 76 is to be energized at this time, the delay contact 76a of going to be opened at time t ₄ has been closed without being opened In. As a result, the exciting coil 73 is energized again,
As a result, the open / close switch 61 is turned on, and the power factor improving capacitor C1 is turned on again. That once detached power factor improving capacitor C1 is re-charged with 80% recovery of the supply voltage V _0. As a result, the reactive power borne by the private generator 5 (see FIG. 7) is reduced, and the possibility of a trip due to a voltage drop can be prevented. However, in this case, the time period of the normally closed contact 71 is longer than the time period of the auxiliary relay 74.

When the applied voltage adjusting means 75 'as in the present embodiment is used, the normally closed contact 74b is closed when the auxiliary relay 74 is deenergized. 30% (approximately 20 V) is bypassed and the voltage applied to the auxiliary relay 74 is as shown in FIG.
2A, the auxiliary relay 74 is energized at a lower recovery voltage than when the applied voltage adjusting means having the configuration shown in FIGS. 2A and 2B is used. Thus, the voltage recovery of 80% or more enables the power factor improving capacitor to be turned on again.

[0037]

As described above, according to the present invention,
Electromagnetic switching generally used to open and close the power factor improving capacitor when installing a power factor improving capacitor that also has harmonic countermeasures on the low voltage side of the premises in the interconnection operation system between the commercial power system and the private power generation equipment The power factor improving capacitor can be disconnected by a simple control circuit without using a high-speed expensive under-voltage relay at the receiving point using a simple control circuit. Therefore, as in the past, there is no need to exchange special control between the low-voltage board installed with the capacitor open / close switch, that is, the electromagnetic switch installed at each location of the power receiving equipment, and the power board installed near the power receiving point. This eliminates the need for control wiring.

After the private power generator is once disconnected from the commercial power supply system when the system is shaken, when the private power system voltage recovers within a short period of time, a power factor improving capacitor having almost the required capacity is automatically re-input. As a result, a large amount of reactive power is not imposed on the private generator, so that a trip due to a decrease in the generator voltage is eliminated, which greatly contributes to stable operation of the generator.

[Brief description of the drawings]

FIG. 1 shows a circuit configuration of an embodiment of a switching circuit for a power factor improving capacitor according to the present invention.

FIGS. 2A and 2B show a specific configuration of an applied voltage adjusting means in the switching circuit shown in FIG.

FIG. 3 is a diagram illustrating the operation of the switching circuit for the power factor improving capacitor shown in FIG. 1;

FIG. 4 shows a circuit configuration of another embodiment of the switching circuit of the power factor improving capacitor according to the present invention.

5A and 5B show another specific configuration of the applied voltage adjusting means in the switching circuit shown in FIG.

FIG. 6 is a diagram for explaining the operation of the switching circuit for the power factor improving capacitor shown in FIG. 4;

FIG. 7 shows a circuit configuration of an interconnection operation system between a commercial power supply system and a private power generation facility, in which a power factor improving capacitor is connected to a low voltage side.

8 shows a circuit configuration of an example of a switching circuit for a power factor improving capacitor in the system shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Commercial power supply 2, 60 Circuit breaker 3 High-voltage power receiving transformer 41, 42 Low-voltage power receiving transformer 5 Private generator 61 Power factor improving capacitor on / off switch 71, 74b Normally closed contact 72, 74a Normally open contact 73 Excitation coil 74 Auxiliary relay 75 Applied voltage adjusting means 76 Open delay type timer relay 76a Open delay contact 100a, 100b Switching circuit L1 Series reactor C1 Power factor improving capacitor

Claims (7)

[Claims] 1. A commercial power system and a private power generation system are connected to each other, a power factor improving capacitor is installed on a low voltage side of a private transformer, and a low-voltage output of the private transformer is provided when the commercial power system shakes. When the voltage drops to a first predetermined voltage that is equal to or lower than the rated voltage, the power factor improving capacitor is disconnected, and the commercial power supply system and the in-house power generation equipment are separated by a system connection protection relay so as to operate separately. In an operation system, an excitation coil for turning on / off an open / close switch of a power factor improving capacitor installed on a low voltage side, and a series-connected excitation coil connected in series with the excitation coil and opened / closed based on a power factor control command. A first contact and a second contact, and a third contact connected in parallel with the first contact,
An auxiliary relay that is deenergized by applying a second predetermined voltage lower than the first voltage when the low-voltage side of the private transformer becomes the first predetermined voltage; and a low-voltage side of the private transformer. And an applied voltage adjusting means for decreasing an applied voltage so that a voltage equal to or less than the second predetermined voltage is applied to the auxiliary relay when the voltage of the auxiliary relay drops below the first predetermined voltage. Switching circuit for the power factor improvement capacitor in system operation. 2. The apparatus according to claim 1, wherein said applied voltage adjusting means comprises a plurality of silicon droppers connected in series.
The switching circuit for the power factor improving capacitor described in (1). 3. The switching circuit for a power factor improving capacitor according to claim 1, wherein said applied voltage adjusting means comprises a resistor. 4. A commercial power supply system and a private power generation facility are connected to each other, a power factor improving capacitor is installed on a low voltage side of the private transformer, and a low voltage output of the private transformer is provided when the commercial power supply is shaken. When the voltage drops to a first predetermined voltage that is equal to or lower than the rated voltage, the power factor improving capacitor is disconnected, and the commercial power supply system and the in-house power generation equipment are separated by a system connection protection relay so as to operate separately. In the operating system, an exciting coil for turning on / off a switch of a power factor improving capacitor installed on a low voltage side is connected in series with the exciting coil and opened / closed based on a power factor control command. A first and a second contact; and a second predetermined voltage lower than the first predetermined voltage is applied and deenergized when a low-voltage side voltage of the private transformer becomes the first predetermined voltage. An auxiliary relay; a third contact that is closed when the auxiliary relay is energized; an open-delay timer relay connected in series with the third contact; and an open-delay contact thereof; When the low voltage side voltage drops to the first predetermined voltage or less, the application voltage adjusting means for lowering the applied voltage so that a voltage equal to or less than the second predetermined voltage is applied to the auxiliary relay; A series connection line of the third contact and the open delay contact is connected in parallel with the first contact, the auxiliary relay and the applied voltage adjusting means are connected in series, and the third contact is opened with the third contact. A switching circuit for a power factor improving capacitor in an interconnection operation, wherein the switching circuit is connected in parallel to a series connection series with a delay timer relay. 5. The power factor improving capacitor switching circuit according to claim 4, wherein said applied voltage adjusting means comprises a plurality of silicon droppers connected in series. 6. The power factor improving capacitor switching circuit according to claim 4, wherein said applied voltage adjusting means comprises a resistor. 7. The applied voltage adjusting means is provided with a contact for bypassing a part of a circuit element constituting the applied voltage adjusting means when the auxiliary relay is deenergized. 7. The switching circuit for a power factor improving capacitor according to any one of 6.