JPH08149688A - Harmonic current and voltage monitor/alarm - Google Patents

Abstract

PURPOSE: To resume operation of a load facility by opening the load facility or stopping the operation thereof when the current distortion of the load facility exceeds a set limit value and resetting the contact when the voltage distortion of the bus is within a predetermined ratio of a value during operation thereby reclosing the contact automatically. CONSTITUTION: Voltage and current are taken in from an instrument current transformers 3, 4 for a load circuit and a bus 2 in order to measure the current distortion and voltage distortion, respectively, at a current measuring section and a voltage measuring section. The current distortion is then compared, at a current comparing section, with a limit value being set at a current setting section and the contacts at contact operating section and holding section are operated and held if the limit value is exceeded. If the measurement of voltage distortion is lower than the limit value, the contacts are released to reset a load 1 automatically. Consequently, reclosing ad reoperation are carried out reliably and a power machine can be protected surely against harmonic trouble.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic current / voltage monitor / alarm device used in power receiving equipment and the like.

[0002]

2. Description of the Related Art Recently, with the spread of harmonic generating loads such as inverters, voltage distortion of a power distribution system has increased, and damage to power equipment due to harmonics has increased. There are many cases in which phase-advancing capacitor equipment is subject to obstacles, and due to the increase in the inflow of harmonic currents into the phase-advancing capacitor circuit, cases such as overheating / burning of the series reactor and dielectric breakdown of the capacitor are increasing.

As one of the measures against the above, the current distortion rate or the harmonic current component of the phase advancing capacitor circuit is detected and monitored, and when the limit value is exceeded, an alarm is issued and the phase advancing capacitor facility is opened. Is being done.

Further, in order to suppress the outflow amount of the harmonic current from the load generating the harmonic to the power supply side, the current of the power converter such as the inverter is monitored to generate the harmonic current exceeding the limit value. When it does, it is also stopped.

[0005]

In the above-mentioned prior art, if the phase advancing capacitor circuit is opened or the power converter is stopped by the operation of the harmonic current monitoring alarm device, the subsequent current detection is impossible. Therefore, there is a drawback that it is not possible to judge whether or not to restart or restart the operation after that.

FIG. 4 shows an example in which a harmonic current monitoring alarm device is applied to a conventional phase advancing capacitor circuit. In the figure, 11 is a phase advancing capacitor, 12 is a series reactor, 6 is a switch, and 30 is a switch. This is a harmonic current monitoring and alarm device. This device detects the current in the phase advancing capacitor circuit by the current transformer 4 for the instrument, and when the harmonic current amount increases and the phase advancing capacitor circuit becomes overloaded, an alarm is issued. A control signal is issued to open the switch 6.

In the above device, when the switch is opened due to the operation of the harmonic current monitoring and warning device, the current in the phase advance capacitor circuit becomes zero, and the subsequent harmonic condition cannot be monitored. Therefore, whether or not the switch 6 can be turned on again causes a problem that must be left to a human judgment.

In addition to the above current detection, the voltage distortion of the bus bar 2 is measured and monitored, and if the voltage distortion exceeds the limit value, the switch is opened to stop the circuit equipment so that the voltage distortion falls below a predetermined value. If this happens, there is also a method to restore operation by reclosing the switch, but the relationship between the permissible current and voltage distortion varies depending on the load equipment's rating and characteristics, and it is difficult to accurately predict it. It cannot be a device.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a harmonic current / voltage monitoring and alarming device which is reliable in operation and is capable of automatically returning a circuit. Is.

That is, from the instrument current transformer 3 of the load circuit and the instrument transformer 4 of the bus 2 to which the load circuit is connected,
The current and voltage are taken in, and the current measuring unit 51 and the voltage measuring unit 50 measure the current distortion and the voltage distortion, respectively, and the current distortion is set in advance by the current setting unit 56 and the current distortion limit value and the current comparison unit 53A. In comparison, if the limit value is exceeded, the contacts of the contact operating unit 58 and the contact holding unit 59 are operated and held.

The voltage distortion at the time of contact operation is stored in the voltage storage section 54, and the voltage distortion limit value is set by the voltage setting section 55 based on this voltage distortion, and the measured voltage distortion value is the voltage comparison section 53B. In comparison with this voltage distortion limit set value, if the voltage distortion becomes less than or equal to this limit set value, a function is provided to automatically restore the load by releasing the above contact holding.

By using the harmonic current / voltage monitoring alarm device 5 having such a function, when the load is a phase-advancing capacitor facility, if the current distortion exceeds the set limit value, the operation of this device causes When it is opened, the series reactor and capacitor are prevented from overheating / burning and dielectric breakdown, and if the bus voltage distortion is reduced to a level that does not cause a problem, they can be automatically re-closed.

In the case of a power converter in which the load generates harmonics, if the current distortion exceeds a set limit value, the operation of this device causes the operation to be stopped or the output to be reduced, and the power supply side of excessive harmonic currents. To prevent the voltage distortion of the bus bar from increasing excessively. If the bus voltage distortion drops to a level that does not cause a problem, automatic restart is possible.

As the current distortion and the voltage distortion, it is convenient to use the current distortion rate and the voltage distortion rate for those in which the fundamental wave current does not largely change, such as a phase advancing capacitor. It is preferable to use the total current distortion rate and the total voltage distortion rate. However, if resonance at a specific harmonic order is a concern, it may be better to use the distortion rate at the specific harmonic order. In addition, in devices and equipment including power converters, the fundamental wave current fluctuates depending on the load, so it is rational to manage the flowing out harmonic current based on the absolute value of the harmonic current. The harmonic current value is preferably used as the current distortion.

[0015]

As described above, the harmonic current / voltage monitoring alarm device of the present invention operates when the current distortion of the load equipment exceeds the set limit value, and opens or stops the operation of the load equipment. When the voltage distortion of the connected bus bar falls below a certain ratio from the value during the operation, the contact is restored and automatically re-closed to restart the operation of the load equipment.

[0016]

Embodiment 1 An embodiment of the present invention will be described with reference to FIGS. FIG. 3A shows an embodiment of the present invention in a phase advancing capacitor circuit, 11 is a phase advancing capacitor, 12 is a series reactor, 6 is a switch, 5 is a harmonic current / voltage monitoring alarm device of the present invention, 3 Is an instrument current transformer, and 4 is an instrument transformer.

FIG. 2 is an internal block diagram of the harmonic current / voltage monitoring alarm device 5 of the present invention, in which the secondary current of the instrument current transformer 3 is input to the current measuring unit 51 to cause current distortion. Is constantly measured and compared with the limit value preset by the current value setting unit 56 and the current comparison unit 53A, and when the current distortion exceeds the set limit value, a signal is sent to the contact operation unit 58. While operating the contact, the contact holding unit 59 continues to hold the contact.

The secondary voltage of the voltage transformer 4 is the voltage measuring unit 5
0, the voltage distortion is constantly measured, and the voltage distortion at the time of contact operation is stored in the voltage storage unit 54. Here, a value obtained by multiplying this voltage distortion value by a fixed ratio (for example, 50%) is set as the voltage. It is set by the unit 55. This voltage setting value and the voltage distortion constantly measured by the voltage measuring section 50 are compared by the voltage comparing section 53B, and when the voltage distortion falls below the voltage setting value, a signal is sent to the contact holding release section 59. Then, the contact is returned to the initial state. The values of the current distortion and the voltage distortion measured in real time can be displayed and monitored on the voltage / current display unit 52.

As described above, due to the series of operations of the harmonic current / voltage monitoring device, the phase advancing capacitor is opened by this contact signal when the current distortion exceeds the set limit, and the voltage distortion is more constant than during this operation. If it decreases at a rate of, it can be re-closed by restoring the contact.

In this case, the distortion factor may be used as the current distortion and the voltage distortion, or the harmonic current value and the harmonic voltage value may be used as the absolute values. Further, as the distortion rate, the harmonic current value, and the harmonic voltage value, only specific orders may be used, or the total distortion rate, the harmonic combined current value, and the harmonic combined voltage value may be used.

[0021]

Second Embodiment FIG. 3B shows an embodiment of the present invention in the case where a load having a power converter such as an inverter is connected to a bus bar.

In FIG. 3B, 21 is a load having a power converter such as a thyristor, 22 is a gate block circuit, and the other circuit configuration is the same as that of the first embodiment.

That is, the output signal of the harmonic current / voltage monitoring alarm device 5 is transmitted to the gate block circuit 22,
Turn on / off the gate signal circuit of power converters such as thyristors
0FF is performed to stop the load and control the operation. Example 1
Similarly, when the current distortion (in this case, the amount of harmonic current) exceeds the set limit value, a signal is transmitted to the gate block circuit 22 to stop the operation of the power converter 21 and the voltage distortion during the above operation. If the value falls below a certain rate, the gate block is released and the load operation can be resumed.

[0024]

As described above, according to the present invention, it is possible to detect the current distortion of the load equipment such as the phase advancing capacitor equipment and the power converter, and to surely open or stop the load at the set limit value. At the same time, when the bus voltage distortion at this time drops below a certain rate, the load can be automatically restarted or restarted, so that reliable harmonic interference prevention or excessive harmonic current can be prevented. Can be prevented.

Compared with conventional monitoring of harmonic current only,
It will be possible to perform restarting and restarting reliably, and it will be possible to more reliably prevent harmonic interference of power equipment compared to monitoring only harmonic voltage, which will be of great industrial and practical value. is there.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a circuit to which a harmonic current / voltage monitoring alarm device of the present invention is applied.

FIG. 2 is an internal configuration diagram of a harmonic current / voltage monitoring alarm device of the present invention.

FIG. 3A is a circuit configuration diagram of a phase advancing capacitor circuit according to the first embodiment of the present invention. FIG. 3 (B) shows
It is a circuit block diagram of the load circuit which has a power converter, such as a thyristor, of Example 2 of this invention.

FIG. 4 is an example of an application circuit of a conventional harmonic current monitoring and warning device.

[Explanation of symbols]

 Power conversion consisting of 1, load 2, bus bar 3, current transformer for instrument 4, transformer for instrument 5, harmonic current / voltage monitoring alarm device 6, switch 11, phase advancing capacitor 12, series reactor 21, thyristor, etc. Load 22 having a device, gate block circuit 30, harmonic current monitoring alarm device 50, voltage measuring unit 51, current measuring unit 52, voltage / current display unit 53A, current comparing unit 53B, voltage comparing unit 54, voltage storage unit 55 , Voltage setting unit 56, current setting unit 57, contact holding release unit 58, contact operating unit 59, contact holding unit T1, voltage input end T2, current input end T3, control signal output end

Front Page Continuation (72) Inventor Kenji Morisada 4th floor Uehara Building, 3rd floor, Uehara Building, 191, Nakabori Town

Claims (3)

[Claims] 1. A load (1) connected to a bus (2), a current transformer (3) for an instrument, a transformer (4) for an instrument, a harmonic current / voltage monitoring alarm device (5) and a switch. A harmonic current / voltage monitoring alarm device used in a system composed of (6), wherein a load (1) is connected to a bus bar (2) connected to an AC power source via a switch (6). , A load current detection instrument current transformer (3) and a bus voltage detection instrument transformer (4), and the harmonic current / voltage monitoring alarm device (5) is the above instrument current transformer. From (3) and the transformer for an instrument (4), current and voltage are taken into the current measuring unit (51) and the voltage measuring unit (50), and the current distortion rate of the load current and the voltage distortion rate of the bus voltage are measured, The current distortion rate is compared with the limit value preset in the current setting section (56) and the current comparison section (53A) to determine the set limit value. In other words, a voltage storage unit (54) that has a contact operation unit (58) that operates and a contact holding unit (59) that holds the operated signal contact, and that stores the busbar voltage distortion rate during the contact operation, It has a voltage setting unit (55) that automatically sets the limit value of the voltage distortion rate by this stored voltage, and compares the set limit value and the voltage distortion rate of the bus voltage with the voltage comparison unit (53B). A harmonic current / voltage monitoring and alarm device having a contact releasing section (57) for releasing the contact holding when the distortion rate of the bus voltage becomes equal to or lower than the set limit value. 2. A load-advancing capacitor facility (11, 1)
2. The harmonic current / voltage monitoring alarm device according to claim 1, wherein 2) or the load is equipment or equipment (21) including a power converter that generates harmonic current. 3. The current distortion rate and the voltage distortion rate are the current distortion rate and the voltage distortion rate, or the current distortion rate and the voltage distortion rate of a preset specific harmonic order, or absolute values. The harmonic current / voltage monitoring alarm device according to claim 1 or 2, wherein the harmonic current value or the harmonic voltage value is