JPH10260744A - Overvoltage protector for reactive power compensator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the voltage increase of power distribution system generated in the case of disconnection from the power distribution system through the main switch of reactive power compensator (SVC), the increase of voltage inside the SVC and the insulation breakdown of main switch or the like. SOLUTION: This device is provided with a reactive power detecting means for detecting the quantity of generated reactive power and a thyristor phase control circuit 17 for turning the quantity of generated reactive power just before the open of main switch 10 to 0 (KVAR) corresponding to a signal from an auxiliary contact linked with the main switch 10 and while suppressing the voltage fluctuation of power distribution system in the case of disconnecting the power distribution system of SVC through the main switch 10, by continuously generating the gate point arc pulse of thyristor 4 with the same phase even after the open of main switch 10, electrostatic energy residual inside the SVC is safely discharged so that the voltage increase of power distribution system or SVC inside and the insulation breakdown of main switch can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overvoltage protection device for a reactive power compensator provided for adjusting reactive power and stabilizing voltage of a distribution system.

[0002]

2. Description of the Related Art Conventionally, as an overvoltage protection device for preventing breakage due to overvoltage in order to open a reactive power compensator from a bus of a distribution system by a main switch, Japanese Patent Laid-Open No. 5-43211 is disclosed.
JP, JP-A-5-143183, JP-A-7-2
An apparatus disclosed in, for example, Japanese Patent No. 36225 is used.

[0003] These devices will be described below with reference to FIGS.
This will be described with reference to FIG. First, as shown in FIG. 9 (Japanese Unexamined Patent Application Publication No. 5-43211), the first conventional example is a thyristor 4 that is closed between the two electrodes of the thyristor 4 at the same time when the main switch 10 is opened and is opened after a lapse of a predetermined time. Is provided.

[0004] The configuration of the first conventional example is such that when a thyristor control reactor TCR of a reactive power compensator (SVC) and a filter FC are connected in parallel to a bus 3 of a power distribution system via a common main switch 10. When the main switch 10 is opened,
A thyristor overvoltage protection circuit that protects the thyristor 4 from overvoltage generated by resonance generated in the SVC by energy stored in the phase advance capacitor 6 in the filter FC is disclosed.

A second prior art example is shown in FIG.
No. 43183), a parallel capacitor 12 for reducing the parallel resonance frequency of the SVC is provided in parallel with the thyristor control reactor TCR.

According to the configuration of the second conventional example, when the thyristor control reactor TCR of the SVC and the filter FC are connected in parallel to the bus 3 of the distribution system via the common main switch 10, the main switch 10 is opened. Sometimes, the peak value of the overvoltage due to the parallel resonance generated by the energy stored in the phase advance capacitor 6 in the filter FC is suppressed, and the thyristor 4 is protected from the overvoltage.

Further, a third conventional example is shown in FIG.
As shown in JP-A-236225), the disconnection sequence at the time of overvoltage detection is disconnected by the circuit breaker 14 first using the filter FC, and after the disconnection is completed, the supply of the firing pulse to the thyristor control reactor TCR is stopped. After the current of the control reactor TCR becomes 0, the thyristor control reactor TCR is disconnected by the circuit breaker 13.

According to the configuration of the third conventional example, when the SVC is disconnected from the bus of the distribution system when an overvoltage occurs in the bus of the system, the firing pulse of the thyristor control reactor TCR for supplying the delayed phase is stopped first. Because of the need to
This prevents the reduction in overvoltage that is promoted by the phase-advancing capacitor in the SVC filter FC that is opened thereafter.

[0009]

Conventionally, when an SVC is opened by a switch, first, it is necessary to halve system voltage fluctuations when the SVC is disconnected from a power distribution system.

Second, it is necessary to safely discharge the energy of the capacitor inside the SVC to protect the SVC internal equipment from overvoltage.

Third, it is necessary to reduce the breaking capacity of the switch. The means disclosed in FIGS. 9 to 11 has been used to solve any of the above three problems.

However, in the first conventional example, the main switch 10
However, there are problems such as the fact that a sufficient breaking capacity for the phase-advancing capacitor 6 is required and that the protection switch 11 of the thyristor 4 is of a mechanical type, so that its reliability is low.

In the second conventional example, the main switch 10 requires a sufficient breaking capacity for the phase-advancing capacitor 6 and only the peak of the overvoltage is suppressed, but the overvoltage itself is not suppressed. And other issues.

Further, in the third conventional example, it is necessary that the breaker 13 has a sufficient breaking capacity for the phase advance capacitor 6, that two breakers 13 and 14 are required, and that the voltage of the system bus is reduced. There have been problems such as abrupt fluctuation and a necessity of a complicated disconnection sequence circuit until the thyristor control reactor TCR is disconnected after the filter FC is disconnected.

The present invention solves the above-mentioned problems. Since the SVC is released from the power distribution system, a complicated disconnection sequence is not required, the breaking capacity of the switch can be reduced, and an accident such as re-ignition does not occur. SV that can be opened with one switch
An object of the present invention is to provide a C overvoltage protection device.

[0016]

In order to achieve the above object, the present invention provides a reactive power detecting means for detecting an amount of reactive power generated, and an auxiliary contact interlocked with a signal of the reactive power detecting means and a main switch. , The thyristor gate firing pulse is generated so that the reactive power generation amount before the main switch is opened becomes 0 (KVar), and the same phase continues after the main switch is opened. And a thyristor phase control circuit that continuously generates a gate firing pulse for the thyristor.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With the above configuration, the thyristor phase control circuit cancels the amount of advanced reactive power generated by the phase advance capacitor of the SVC filter and the amount of delayed reactive power generated by the thyristor control reactor to 0 (KVar). In order to control the firing pulse of the thyristor,
When the main switch is opened, an overvoltage is not generated inside the main switch, and the main switch having a small breaking capacity has an operation of reliably opening.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an application to a general SVC, and FIG. 2 shows an application to an SVC with suppressed harmonic output. Since the opening operation is the same for FIGS. 1 and 2, the embodiment will be described with reference to FIG.

In FIG. 1, as reactive power detecting means for detecting the amount of reactive power generated at the installation point of the SVC, there are a current transformer CT, a transformer VT, and a reactive power calculation circuit. 23 and the signal from the auxiliary contact 20 of the main switch 10, the reactive power generation amount of the SVC is reduced to 0.
(KVar). The thyristor 4 includes a thyristor phase control circuit 17 that generates a gate firing pulse of the thyristor 4 and continues to generate a gate firing pulse in the same phase even after the main switch is opened.

FIG. 1 shows a general SVC in which a filter FC of a phase advance capacitor 6 and a series reactor 7 is connected in parallel to a step-down transformer 5 and a thyristor control reactor TCR of the thyristor 4.

FIG. 2 shows an SVC different from that of FIG.
Step-down transformer 5 and reactors L1 and L2 for harmonic absorption
And a thyristor 4 are connected in series, and a filter FC including a series reactor 7 and a phase-advancing capacitor 6 is connected in parallel with the reactor L2 for harmonic absorption and the thyristor 4, so that the harmonic output can be absorbed. Things.

With this configuration, a switch-off signal is transmitted from the auxiliary contact 20 to the thyristor phase control circuit 17 before the main switch 10 is opened. Further, the thyristor phase controller 17 generates a gate firing pulse of the thyristor 4 based on a signal from the reactive power calculation circuit 23 so that the reactive power output of the SVC becomes 0 (KVar). Since the thyristor 4 of the SVC operates at a high speed, the output of the SVC is set to 0 (KVar) before the main switch 10 is opened.
Therefore, the main switch 10 is opened at a current of 0.

Since the thyristor phase control circuit 17 continues to generate gate firing pulses of the same phase even after the main switch 10 is opened, the energy of the phase advance capacitor 6 is discharged by the thyristor 4. .

In this discharge, the discharge voltage has a waveform synchronized with the power supply frequency because the gate firing pulse of the phase control circuit 17 is synchronized with the power supply frequency. This allows
Primary side (power supply side) and secondary side (SVC side) of main switch 10
Is 0 (v).

FIG. 3 shows a main switch 1 not according to the present invention.
8 shows an internal voltage waveform of the SVC when the gate is not fired after the opening of 0. From FIG. 3, the main switch 10
It can be seen that, after the opening of the capacitor, the phase-advancing capacitor 6 has been discharged by a voltage having a higher peak value at a frequency different from the system power supply voltage.

As a result, an excessive voltage is generated between the primary side (power supply side) and the secondary side (SVC side) of the main switch 10 and the secondary side different polarity, as shown in FIGS. 4 and 5. Re-ignition occurs.

FIG. 6 shows the internal voltage waveform of the SVC when the gate is fired at 0 (KVar) after the main switch 10 is opened according to the present invention. FIG. 6 shows that after the main switch 10 is opened, the phase-advancing capacitor 6 is discharged at the same frequency as the system power supply voltage while the peak value gradually decreases from the voltage before the opening.

As a result, the voltage between the primary side (power supply side) and the secondary side (SVC side) of the main switch 10 becomes 0 (v),
In addition, since the secondary side different polarity voltage becomes lower than before the opening, re-ignition and re-arcing as shown in FIGS. 4 and 5 do not occur.

FIG. 7 shows the internal voltage waveform of the SVC when the operation is performed with the amount of reactive power generated by proceeding through the gate firing after the main switch 10 is opened.

According to FIG. 7, after the main switch 10 is opened, at the same frequency as the system power supply voltage, the peak value once increases sharply from the voltage waveform before the opening and then gradually decreases, and then the discharge of the phase advance capacitor 6 occurs. doing.

As a result, the primary side (power supply side) of the main switch 10
As a result of the generation of an excessive voltage between the secondary side (SVC side) and the secondary side different polarity, re-ignition and re-arcing occur as shown in FIGS.

FIG. 8 shows the internal voltage waveform of the SVC when the gate is fired after the main switch 10 is opened with the amount of delayed reactive power generated. From FIG. 8, after opening the main switch 10,
Discharge of the phase advance capacitor 6 occurs instantaneously.

As a result, no excessive voltage is generated between the primary side (power supply side) and the secondary side (SVC side) of the main switch 10 and the secondary side different polarity, but the thyristor 4 fails due to erroneous firing. Is easy to occur.

The function of preventing the occurrence of overvoltage and 0 (KVar)
As a result, the main switch 10
The main switching device 10 having a low breaking capacity is sufficient.

The output fluctuation of the SVC from the outside only becomes 0 (KVar) immediately before the main switch 10 is opened, and the system voltage fluctuation is small.

Further, since the reactive power detecting means and the phase control circuit 17 are normally provided in the SVC, a complicated disconnection sequence is newly constructed for opening the main switch 10. do not have to.

[0038]

As is apparent from the above description, according to the present invention, an ignition pulse is generated in which the reactive power generation amount before opening the main switch for disconnecting the SVC from the system power supply is 0 (KVar). With the configuration including the phase control circuit that continues to generate the thyristor gate firing pulse in the same phase even after the main switch is opened, the SVC is disconnected from only the single main switch 10 from the SVC system bus 3. It has an excellent effect of completely preventing the occurrence of overvoltage in the distribution system or SVC, using a switch having a low breaking capacity, and realizing an SVC overvoltage protection device with high open reliability. It is.

[Brief description of the drawings]

FIG. 1 is a system circuit diagram illustrating an SVC overvoltage protection device according to a first embodiment of the present invention.

FIG. 2 is a system circuit diagram showing another application example of the embodiment.

FIG. 3 is a voltage waveform diagram inside the SVC when the main switch is opened according to the present invention.

FIG. 4 is a voltage waveform chart showing an example of restriking.

FIG. 5 is a voltage waveform diagram showing an example of the re-arcing.

FIG. 6 is a voltage waveform diagram inside the SVC when the main switch is opened according to the present invention.

FIG. 7 is a voltage waveform diagram inside the SVC of the advanced reactive power not according to the present invention.

FIG. 8 is a voltage waveform diagram inside the SVC of delayed reactive power not according to the present invention.

FIG. 9 is a system circuit diagram of an SVC showing a first conventional example.

FIG. 10 is a system circuit diagram of an SVC showing a second conventional example.

FIG. 11 is a system circuit diagram of an SVC showing a third conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 4 thyristor 5 step-down transformer 6 phase capacitor 7 series reactor 10 main switch 17 thyristor phase control device 20 auxiliary contact 21 instrument current transformer CT (reactive power detection means) 22 instrument transformer VT (reactive power detection means) 23 Reactive Power Calculation Circuit (Reactive Power Detection Means) TCR Thyristor Control Reactor FC Filter

Claims (1)

[Claims] A reactive power detection means for detecting a reactive power generation amount, and a reactive power generation amount before the main switch is opened, based on a signal from the reactive power detection means and a signal from an auxiliary contact linked to the main switch. A thyristor phase control circuit that generates a thyristor gate firing pulse so as to make 0 (KVar) and continues to generate a thyristor gate firing pulse in the same phase even after the main switch is opened. Overvoltage protection device for compensator.