JPH025468Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a protection device for a disconnector in which a residual current remains, such as a disconnector in a DC feeding system, and particularly for a system in which a static disconnector is provided. This invention relates to a protection device for a disconnector.

The breaking current of a disconnector in a DC power supply system will be explained using an example of an equivalent circuit shown in FIG. The own substation converter CNV ₁ outputs voltage when under constant voltage control, and the no-load voltage (a = 30°) is
The waveform will be as shown in Figure a. The connection between the converter CNV ₁ and the disconnector DS is represented by a constant current source i due to the leakage current in its disconnected state. disconnector
Ripple current bypass capacitors C ₁ and C ₂ are present on both electrode sides of DS. The feeder line connected to the disconnector DS has an overhead line inductance L and is connected to the converter CNV ₂ of the adjacent substation, and there is also a capacitor C ₃ typified by a bypass capacitor on the adjacent substation side. The output voltage waveform of converter CNV ₂ is as shown in FIG. 2b at the disconnector DS position.

Therefore, when the disconnector DS is disconnected, a current i shown in FIG. 2c flows through the disconnector DS. That is, charging current I _p and leakage current i flow from converter CNV ₁ to capacitor C ₂ , and reverse current i _r flows from the adjacent substation through inductance L to capacitor C ₁ . This current is the allowable current (1
Although the disconnection current is designed to be less than the allowable current, it may cause the disconnector to malfunction. That is, since the disconnector DS does not have an arc extinguishing chamber, an arc occurs between the electrodes due to a current exceeding the allowable current or disconnection, leading to an electrode burnout accident.

In particular, those that use a static type as the shear breaker, use thyristors and their like as the shear breaker element.
Leakage current through the CR snubber circuit and commutation circuit is large, and the steady-state operating current in the feeding system is several thousand amperes, so the number of parallel thyristor elements increases, resulting in a large leakage current and the disconnector. Easy to cause burnout accidents.

Figure 3 shows only one circuit of a static type circuit breaker.
In addition to the main thyristor TH _1, the commutation circuit includes a commutation capacitor C ₁ , an auxiliary thyristor TH ₂ and a diode D ₁ , and a snubber circuit for the main thyristor TH ₁ includes a resistor R ₁ and a capacitor C ₂ .
The main thyristor's cutting action is controlled by the auxiliary thyristor.
The charge of the capacitor C ₁ , previously charged to the polarity shown by igniting TH ₂ , is transferred to the diode D ₁ −
A discharge is caused in the loop of the auxiliary thyristor _TH2 , and the main thyristor _TH1 is reverse biased for a period longer than its turn-off time to turn off the main thyristor _TH1 . Auxiliary thyristor TH ₂ is a commutating capacitor
The voltage polarity of _C1 is reversed and turned off. In such a short circuit, main thyristor TH ₁ is in the off state and its leakage current flows to the disconnect switch DS side, ripple current flows to the snubber circuit, and the sum of these leakage currents is the sum of the leakage currents of the individual parallel main thyristors. increases as

SUMMARY OF THE INVENTION An object of the present invention is to provide a protection device which ensures that the disconnection operation of a disconnector is performed at a current below its allowable limit.

The present invention is characterized in that the current in the disconnector circuit conductor is detected at an acceptable or disconnection current level, and based on this detection output, it is determined whether or not the disconnector can be disconnected, and the operation is controlled. Additionally, it features a shingle break current detector that can detect shingle break current with higher accuracy than conventional current transformers. Further, the present invention is characterized in that the determination of whether or not the disconnector can be operated is made based on the detection output of the disconnection current based on the average value of the detected current.

Hereinafter, the protection device of the present invention will be explained in detail.

First, as the protection device of the present invention, a detector capable of detecting electric circuit conductor current is prepared. As this current detector, a shunt type is generally known, which is composed of a shaft resistor and an amplifier that detects and amplifies the voltage of this resistor. However, in a DC feeding system, the current is several thousand amperes (4,000 to 10,000 amperes) at steady state.
Since it is necessary to detect a current of about 1 ampere during a disconnection operation from a flowing electric path, current detection using the shunt method is inconvenient. In other words, when detecting a current of about 1 ampere using the shunt method, if the shunt resistance value is designed so that the shunt resistance detection voltage is 5mv/1A in order to cover the error caused by the offset current change of the amplifier, the shaft resistance will change when a steady current is applied. losses will increase. For this reason, it is difficult to manufacture the shunt resistor itself, and it is not practical.

Therefore, the protective device of the present invention uses magnetic current detection as a break-out current detector, and this detector is magnetically saturated with steady-state operating current, and accurately detects the allowable break-out current level. Eliminating losses.

FIG. 4 shows the circuit configuration of the present invention. In the figure, a magnetic circuit for magnetomotive force generated by the conductor current is formed with an iron core 2, with a conductor 1 constituting a disconnector circuit as the primary side, and a Hall element 3 is arranged in the gap of the iron core 2. A current source (not shown) that flows in a direction perpendicular to the direction of the magnetic field is connected to 3, and a voltage proportional to the current in conductor 1 is applied to Hall element 3.
Take it out. This Hall generator is designed to have a small saturation amperage so that the magnetic circuit is saturated when the current flowing through the conductor 1 is higher than the allowable current of the disconnector. Ensures sex. Furthermore, since the magnetic circuit is saturated when a steady current is applied, a coercive force remains in the iron core 2 of the magnetic circuit even after the shield breaker is tripped, and this coercive force affects the shield current detection. Therefore, the iron core 2 is made of a permalloy-based material that is not easily affected by temperature changes, for example, 45% nickel permalloy, and a Hall generator is used in which the coercive force of the iron core 2 is sufficiently small compared to the magnetomotive force of a minute current.

Since the output voltage of the Hall element 3 has a waveform having spikes as shown in FIG. 2c, a low-pass filter 5 is provided in series with the sense amplifier 4, and the average value thereof is detected as the disconnection current of the disconnector. For example, the disconnection operation is the period in which the spike current Ip flows as shown in Figure 2c.
Comparing tip and the period ti during which leakage current i flows, tip
<<ti, and since the period during which the spike current Ip flows is extremely short, there is no problem in taking the average value of the current waveform as the shearing current. The average value output of the low-pass filter 5 is passed through the absolute value circuit 6, so that its polarity is aligned, and the current i and the reverse current in Fig. 2c are
The comparator 7 detects that any polarity current of i _r is below the allowable disconnection current of the disconnector. Comparator 7
When the output of the absolute value circuit 6 is smaller than the allowable current value set in , the relay 8 is energized.
The contact is closed to allow the disconnection operation coil 9 of the disconnector to operate. Conversely, when the current flowing through the disconnector is larger than its allowable disconnection current, relay 8
to prevent disconnection switch operation. 10 is a switch equivalently indicating a disconnector operation command.

Therefore, the protective device according to the present invention detects the conductor current of the circuit with a Hall generator, sets the saturation of the magnetic circuit to a low current level, and reduces the coercive force of the magnetic circuit at a steady operating current. Since this is a detection method, there is no loss in steady-state operating current, and short-circuit current can be detected with high accuracy. Furthermore, since it uses a magnetic circuit for detection, it is easy to insulate from the primary conductor and can be configured into a small Hall generator. In addition, the determination circuit that determines whether or not a disconnection operation is possible from the output of the Hall generator is
Since the judgment is made from the average value, there is no need for a means to measure the current-carrying time ratio between the peak current (spike current) and the minimum current, and the judgment can be made in accordance with the disconnection characteristics of the disconnector without complicating the judgment circuit configuration. .

[Brief explanation of the drawing]

Figure 1 is an equivalent circuit to explain disconnector disconnection current waveforms in a DC feeding system, Figure 2 is a waveform diagram to explain disconnector disconnection current waveforms, and Figure 3 is a static type circuit. FIG. 4 is a circuit configuration diagram showing an embodiment of the present invention. 1... Electric circuit conductor, 2... Iron core, 3... Hall element, 4... Sense amplifier, 5... Low pass filter, 6... Absolute value circuit, 7... Comparator, 8... Relay, 9... Disconnector operation coil, DS...disconnector.

Claims (1)

[Scope of utility model registration request] In a disconnector that is inserted in series with a static type disconnector in a DC feeder line, the circuit conductor of the disconnector is used as the primary side and is saturated at a current level that is higher than the allowable disconnection current of the disconnector. A magnetic circuit whose coercive force is sufficiently smaller than the magnetomotive force caused by the magnetic circuit, a Hall element provided in the gap of this magnetic circuit to obtain a voltage output proportional to the magnetomotive force of the magnetic circuit, and a Hall element that amplifies the output voltage of the Hall element. a sense amplifier, a low-pass filter that obtains an average value output by suppressing the spike current of the conductor included in the output of this sense amplifier, an absolute value circuit that aligns the output polarity of this low-pass filter, and this absolute value. A comparator that determines from the output of the circuit whether or not the current is below the allowable or disconnection current of the disconnector, and when the comparator has a determination output that is below the allowable or disconnection current, the disconnection operation of the disconnector is permitted. A protection device for a disconnector, comprising a relay circuit.