KR102250731B1 - Switchboard with switching module for opening and closing capacitors to improve inrush current - Google Patents

Abstract

The present invention relates to a switchboard with a switching module for opening and closing a capacitor to improve an inrush current so as to improve the inrush current occurring when a capacitor installed for reactive power compensation is connected to a power line, and the switchboard includes: a capacitor array including a plurality of capacitor banks connected to a power line between a power source and a load for reactive power compensation; a switching module provided between the power line and the capacitor array to determine whether the capacitor bank and the power line are connected, and including a contactless relay (solid state relay) and a magnetic contactor connected in parallel to each other; and a control unit configured to connect or disconnect the capacitor bank to the power line by sequentially controlling the contactless relay and the magnetic contactor included in the switching module according to the need for reactive power compensation.

Description

Switchboard with switching module for opening and closing capacitors to improve inrush current}

The present invention relates to a switchboard, and more particularly, to a switchboard capable of improving an inrush current generated when opening and closing a capacitor.

Inrush, input surge current, or switch-on surge refers to the maximum instantaneous pressure current that flows temporarily when the electrical equipment is turned on. Since such inrush current has a characteristic that gradually decreases and reaches a steady state after a current corresponding to several times the current flowing normally flows, it may cause problems such as deterioration of the electrical device, deterioration of performance, and poor recognition. In the case of a switchboard, it causes overheating of capacitors used for compensation of reactive power, malfunction of relays, noise generation of transformers and motors, distortion of voltage and current waveforms, and generation of harmonics, and needs to be resolved.

In addition, in a capacitor used for compensation of reactive power, which is generally connected to a switchboard, a switch is included to connect the capacitor to a power line. Such a switch has low conduction loss and uses a relatively inexpensive magnetic contactor (MC, Magnetic Contact), which is turned ON/OFF several times a day. The above-described magnetic contactor has the disadvantage of generating arcs and surges during the OFF operation that blocks the current, and the arc generated at this time causes problems such as fusion of the contact points of the magnetic contactor or occurrence of contact failure, resulting in maintenance costs. there was. In addition, there is a problem in that the opening and closing surge generated at the contact generates harmonics, causing damage to other electronic devices and communication devices, or causing a malfunction.

Korean Registered Patent Publication No. 10-1514748 ("Switchboard with intelligent switching module for opening and closing a capacitor, announcement date 2015.04.24.)

The present invention was conceived to solve the above problems, and an object of a switchboard having a switching module for opening and closing a capacitor for improving inrush current according to the present invention is to be installed for compensation of reactive power in the switchboard. It is to provide a switchboard having a switching module for opening and closing a capacitor for improving the inrush current that can improve the inrush current generated when the capacitor is connected to a power line.

A switchboard having a switching module for opening and closing a capacitor for improving inrush current according to the present invention for solving the above-described problems includes a plurality of capacitor banks connected to a power line between a power source and a load for reactive power compensation. A condenser array that is provided between the power line and the condenser array to determine whether to connect the condenser bank and the power line, but use a solid state relay and a magnetic contactor connected in parallel with each other. And a control unit for connecting or releasing the capacitor bank to the power line by sequentially controlling the contactless relay and the magnetic contactor included in the switching module according to whether or not the included switching module and reactive power compensation are required. It is done.

In addition, when it is determined that the reactive power compensation is necessary, the control unit conducts the contactless relay in an open state, conducts the electromagnetic contactor in an open state, and then opens the contactless relay in an conduction state. do.

In addition, when it is determined that reactive power compensation is not required, the control unit conducts the contactless relay in an open state, opens the magnetic contactor in a conduction state, and then opens the contactless relay in a conduction state. It is done.

In addition, a power supply voltage sensing unit for sensing the voltage of the power source and a capacitor voltage sensing unit for sensing the voltage of the capacitor bank, the control unit, when it is determined that reactive power compensation is required, the power supply voltage sensing unit senses it. When the voltage of the power source and the voltage of the capacitor bank sensed by the capacitor voltage sensing unit are equal to each other, the switching module is controlled and connected to the power line.

In addition, the power supply is a three-phase power supply, the single capacitor bank includes a three-phase connected capacitor, the capacitor voltage sensing unit senses the voltage of each of the three-phase connected capacitors, the switching module is the capacitor It is characterized in that it includes three pairs of contactless relays and magnetic contactors connected for each phase of the bank.

In addition, the capacitor is a three-phase delta-connected capacitor, and when it is determined that reactive power compensation is required, the control unit controls the switching module connected to a delta-connected capacitor of one of the three-phase Telta-connected capacitors to control the corresponding phase. When the line voltage of the remaining phases sensed by the capacitor voltage sensing unit is the same as the line voltage of each of the remaining phases sensed by the power voltage sensing unit based on the conducted phase, the remaining phases It characterized in that the contactless relay and the electromagnetic contactor connected to the sequentially conducting.

In addition, the switching module is connected in series with the solid-state relay, maintains a conduction state in a normal state, and an auxiliary contact that is opened when a short failure of the solid-state relay connected in series and the auxiliary contact is opened, an alarm It characterized in that it further comprises an alarm unit for transmitting a signal.

According to the switchboard provided with a switching module for opening and closing a capacitor for improving inrush current according to the present invention as described above, a contactless relay and an electromagnetic contactor are formed by using a contactless relay and an electromagnetic contactor connected in parallel with each other in the switching module. By sequentially conducting and opening the contactless relay afterwards, the occurrence of arc and surge voltage that occurred during switching using only the existing magnetic contactor can be prevented, thereby improving the durability of the switchboard according to the present invention, and enabling continuous operation. There is an effect.

In addition, according to the present invention, since the control unit sequentially conducts the contactless relay and the magnetic contactor included in the switching unit at the same time when the voltage of the capacitor and the voltage of the system are the same, not only when the capacitor is completely discharged, but also Even when a residual charge is present, transient phenomena such as an inrush current and a bus instantaneous voltage drop due to the occurrence of the inrush current can be suppressed, such as overvoltage in the CT secondary circuit.

1 is a schematic diagram of a switchboard having a switching module for opening and closing a capacitor for improving inrush current according to a first embodiment of the present invention.
FIG. 2 is a partially enlarged view of FIG. 1;
3 is a switching signal for each of a contactless relay and an electromagnetic contactor included in a switching module of a switchboard having a switching module for opening and closing a capacitor for improving inrush current according to the first embodiment of the present invention.
4 is a switching signal according to a voltage of a capacitor and a voltage of a power source included in a capacitor bank of a switchboard having a switching module for opening and closing a capacitor for improving inrush current according to the first embodiment of the present invention.
5 is a schematic diagram of a switchboard including a switching module for opening and closing a capacitor for improving inrush current according to a second embodiment of the present invention.

Hereinafter, a preferred embodiment of a switchboard including a switching module for opening and closing a capacitor for improving inrush current according to the present invention will be described in detail with reference to the accompanying drawings.

1 schematically shows a switchboard having a switching module for opening and closing a capacitor for improving inrush current according to a first embodiment of the present invention.

As shown in FIG. 1, a switchboard having a switching module for opening and closing a capacitor for improving inrush current according to the first embodiment of the present invention includes a capacitor array 100, a first switching module 210, and a second switching. It may include a module 220 and a control unit (not shown).

As shown in FIG. 1, the capacitor array 100 is connected to a power line 30 connecting between the power supply 10 and the load 20 to compensate for reactive power. The capacitor array 100 of the present invention may include a plurality of capacitor banks, and in this embodiment, two capacitor banks, that is, a first capacitor bank 110 and a second capacitor bank 120 may be included. The first capacitor bank 110 and the second capacitor bank 120 may be connected to the power line 30 in parallel with each other. However, the present invention does not limit the number of capacitor banks included in the capacitor array 100 to two, and there may be an embodiment of a capacitor array including a single capacitor or three or more capacitor banks as needed.

In this embodiment, as the power supply 10 is three-phase, a single capacitor bank may include three capacitors to correspond to each phase. As shown in FIG. 1, in this embodiment, three capacitors may be delta-connected.

The first switching module 210 and the second switching module 220 are provided between each of the first capacitor bank 110 and the second capacitor bank 120 and the power line 30 included in the capacitor array 100. , Decide whether to connect each capacitor bank. As described above, in this embodiment, as the power supply 10 is a three-phase power source, the switching module may also include three switches for each phase.

FIG. 2 shows in more detail the first switching module and the second switching module shown in FIG. 1 of the present invention.

As shown in FIG. 2, among switches included in a single switching module and connected to each phase, only a single switch is connected to one phase, and a solid state relay and a magnetic contactor are connected to the other two phases. Can be connected in parallel with each other.

Based on the first switching module of FIG. 2, the single switch located at the far left is not related to any switch, but in this embodiment, a mechanical contact switch may be used, and for convenience of explanation, the corresponding phase to which the mechanical contact switch is connected is T-phase. It is called this.

In the first switching module 210 of FIG. 2, the switch located at the center and the right side may further include an auxiliary contact in which the contactless relay and the magnetic contactor are connected in parallel with each other, and the contactless relay and the auxiliary contact are connected in series. The auxiliary contact maintains a conductive state normally, and is opened in case of a short failure of the solid-state relay connected in series with the auxiliary contact, thereby preventing further failure. In addition, the present invention may further include an alarm unit that transmits a signal notifying a failure to the user when the auxiliary contact is opened. The alarm unit may transmit a kind of communication signal to the user, or may transmit a signal in a manner such as audible, visual or tactile sense.

The control unit sequentially controls the contactless relay and the electromagnetic contactor included in the switching module 200 according to whether reactive power compensation is required, and connects or disconnects the capacitor bank 100 to the power line 30.

Hereinafter, a process of connecting the contactless relay and the electromagnetic contactor of the control unit will be described in detail.

When it is determined that reactive power compensation is necessary, the control unit first connects the T-phase switch and then transmits a control signal to the switch connected to the R-phase or S-phase, and the switch connected to the R-phase or S-phase receives a control signal from the control unit. If so, the open solid-state relay as shown in point P1 of FIG. 3 may be first turned on. Since the solid state relay uses a semiconductor, arc and surge do not occur when it is converted from an open state to a conductive state. When the contactless relay is turned on, the control unit transmits a control signal to the magnetic contactor, and changes the magnetic contactor from the open state to the conductive state as in the P2 time point. In this case, in a predetermined section such as W1, the contactless relay and the magnetic contactor can be kept in a conductive state at the same time. After the magnetic contactor is changed to a conductive state, the control unit transmits a control signal to the contactless relay, so that the contactless relay is opened as at the point P3. In other words, in the W2 section, only the magnetic contactor is maintained in a conductive state, so that heat generation when the non-contact relay is conducted for a long time can be prevented.

When it is determined that reactive power compensation is not required, the control unit transmits a control signal to the switch connected to the R-phase or S-phase to conduct the open solid-state relay as shown in point P4 in FIG. Is changed to an open state, and then a control signal is transmitted to the solid state relay to open the solid state relay in a conductive state as at point P6, thereby separating the capacitor array 100 from the power line 30.

As described above, in the method of opening or conducting the first switching module 210, the switching itself is performed in a solid-state relay to ensure safety during switching (prevention of arc and surge voltage generation), while the solid-state relay is used for a short time. It is possible to take advantage of the magnetic contactor with relatively little heat generation by using only the magnetic contactor and using the magnetic contactor for a long time.

However, even if the capacitor array 100 is connected or separated from the power line 30 by using a hybrid switch including a solid-state relay and an electromagnetic contactor connected in parallel with each other in the first switching module 210 as described above, the capacitor Due to the residual charge of the capacitor included in the array 100, the voltage may be non-zero even in the separated state, so when the first switching module 210 is connected, an inrush current is generated, which may cause damage to the surrounding electronic devices. . In order to prevent this, the present embodiment further includes a power voltage sensing unit for sensing a voltage of the power supply 10 and a capacitor voltage sensing unit for sensing a voltage of a capacitor included in a single capacitor bank, and the control unit is a power voltage sensing unit. The switching module 200 may be controlled using information sensed by the and capacitor voltage sensing unit.

In more detail, the power voltage sensing unit senses the voltage of the power supply 10 from the power line 30, the capacitor voltage sensing unit senses the voltage of the capacitor included in the capacitor array 100, and the control unit is the power voltage sensing unit and the capacitor. When the voltage of the power supply 10 sensed by the voltage sensing unit and the voltage of the capacitor are the same, a control signal is applied to the first switching module 210 to conduct the first capacitor bank 110 to the power line 30 ). That is, in the process of connecting the first switching module 210 because the voltage of the power supply 10 sensed by the power voltage sensing unit and the capacitor voltage sensing unit is the same in the control unit, the T phase is After connecting the switch first, the solid-state relay and the magnetic contactor of the switch connected to each of the S-phase and R-phase are sequentially controlled.

In this embodiment, since the power supply 10 is 3-phase and the first capacitor bank 110 is also 3-phase delta-connected, the controller uses the voltage of the R-phase capacitor based on the T phase of the first capacitor bank 110. When the voltage of the S-phase capacitor in (10) is the same as the voltage of the R-phase, and when the voltage of the S-phase capacitor is the same as the voltage of the S-phase of the power supply 10, the switch of the switch module connected to each phase (solid-state relay And an electromagnetic contactor), and this process is shown in FIG. 4. In FIG. 4, the dotted line represents the voltage of each of the R phase and the S phase of the power supply 10, and the solid line represents the voltage of a capacitor connected to each of the R phase and S phase included in the first capacitor bank 110. Before the capacitor bank is connected to the power line 30, the voltage of the capacitor connected to each of the R and S phases of the first capacitor bank 110 is maintained at a constant value, but an input signal (trigger signal) is received from the control unit. After this point, the switch included in the switching module is turned on at the same time as the voltage of each capacitor in the R-phase and S-phase of the capacitor bank and the voltage of each of the R-phase and S-phase of the power supply 10, thus suppressing the inrush current. You can confirm that.

The control unit calculates the power factor using the power supply voltage sensing unit, the capacitor voltage sensing unit, or other sensors that sense the current/voltage on the power line, and determines whether the switching module is operated to compensate for the reactive power according to the calculated power factor. can do.

The present invention is not limited to the above-described embodiments, and the scope of application is diverse, as well as anyone with ordinary knowledge in the field to which the present invention belongs without departing from the gist of the present invention claimed in the claims. Of course, various modifications are possible.

10: power
20: load
30: power line
100: capacitor array
110: first capacitor bank
120: second capacitor bank
210: first switching module
220: second switching module

Claims (7)

A capacitor array including a plurality of capacitor banks connected to a power line between a power source and a load to compensate for reactive power;
A switching module provided between the power line and the capacitor array to determine whether to connect the capacitor bank and the power line, but including a solid state relay and a magnetic contactor connected in parallel with each other ; And
A controller for connecting or releasing the capacitor bank to the power line by sequentially controlling the contactless relay and the magnetic contactor included in the switching module according to whether reactive power compensation is required;
A power supply voltage sensing unit sensing the voltage of the power supply; And
A capacitor voltage sensing unit sensing a voltage of the capacitor bank;
Including,
When it is determined that reactive power compensation is necessary, the control unit controls the switching module when the voltage of the power sensed by the power voltage sensing unit and the voltage of the capacitor bank sensed by the capacitor voltage sensing unit are the same. Connect it to the power line,
The power source is a three-phase power source including first to third phases,
The single capacitor bank contains a three-phase delta-connected capacitor,
The capacitor voltage sensing unit senses the voltage of each of the three-phase connected capacitors,
The switching module includes two pairs of contactless relays and magnetic contactors connected to the first and second phases of the capacitor bank, respectively, and includes an electromagnetic contactor connected to the third phase ((T phase) of the capacitor bank, ,
When it is determined that reactive power compensation is required, the control unit operates an electromagnetic contactor connected to the third phase of the three-phase delta wiring capacitor to conduct the third phase,
The line voltages of the first and second phases sensed by the capacitor voltage sensing unit based on the third phase are the first and second phases sensed by the power voltage sensing unit based on the third phase. When the voltage between the lines of each phase is the same,
A switchboard having a switching module for opening and closing a capacitor, characterized in that the contactless relay connected to each of the first and second phases and the magnetic contactor are sequentially connected to each other.
The method of claim 1,
When it is determined that the reactive power compensation is necessary, the control unit conducts the contactless relay in an open state, conducts the electromagnetic contactor in an open state, and then opens the contactless relay in a conduction state. A switchboard equipped with a switching module for opening and closing.
The method of claim 1,
When it is determined that reactive power compensation is not required, the control unit conducts the contactless relay in an open state, opens the magnetic contactor in an conduction state, and then opens the contactless relay in a conduction state. A switchboard equipped with a switching module for opening and closing a capacitor.
delete delete delete The method of claim 1,
The switching module,
An auxiliary contact connected in series with the solid-state relay, maintaining a conduction state in a normal state, and opened when a short failure occurs in the series-connected solid-state relay; And
An alarm unit for transmitting an alarm signal when the auxiliary contact is opened;
A switchboard having a switching module for opening and closing a capacitor, characterized in that it further comprises.

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