JPS60183815A - Overvoltage protecting device of thyristor valve - Google Patents

Abstract

PURPOSE:To attain small size and light weight and to improve the reliability by providing a gapless arrestor in parallel with each thyristor via an impedance in a thyristor valve where thyristors having a self-trigger function to a forward voltage are connected in series or in series and parallel for the plural number. CONSTITUTION:As the thyristors, n-set of free thyristors having self-trigger function (VBO) and each thyristor and a gapless arrestor are connected via the impedance. The protection level (VAr) of each gapless arrestor is set lower than the voltage (VBO) of each VBO free thyristor subject to VBO. Moreover, the impedance (Z) 5 is decided so as to establish the following equation, where I1 is the minimum running current flowing to the thyristor valve; VBO=VAr+(I1XZ). If an overvoltage is applied to the thyristor valve, the gapless arrestors 3-1- 3-n are operated in series to the overvoltage applied to the entire thyristor valve so as to protect the VBO free thyristors from the overvoltage.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to overvoltage protection for thyristor valves used in DC power transmission, etc., and particularly relates to overvoltage protection for thyristor valves used in DC power transmission, etc. This article relates to an overvoltage protection method for thyrisk valves using

[Background of the Invention and its Problems] In recent years, VBO free thyristors that can protect against forward overvoltage by self-ignition have been developed and are on the verge of being put into practical use.

The VBO free thyristor has a predetermined voltage applied in the forward direction (here, VB
(referred to as O), it is possible to fire normally without sustaining any damage without supplying a Goo1-pulse.

There are several overvoltage protection methods for υiristor valves, but
The method of connecting a capless arrester in parallel to individual thyristors connected in series can suppress the dynamic overvoltage of each thyristor, and also allows the arrester to be standardized for the rated voltage of the thyristor, regardless of the device rating. There are advantages.

FIG. 2 is a simplified schematic diagram of a thyristor valve employing this overvoltage protection method. 1-1 to 1-n are thyristors connected in series, and 2 is dV/'dt.

Old/dt suppression reactor, 3-1. , 3-n is a Gats breath arrester. In reality, each thyristor has
A voltage divider circuit, a goo-1 circuit, etc. are connected, but are omitted here. As the gapless arresters 3-1 to 3-n, zinc oxide nonlinear resistors or the like are used. By setting the protection level of this thyristor valve, the non-repetitive off-voltage or non-repetitive reverse voltage of the thyristor
The gapless arrester has a lower protection level.

When a forward or reverse overvoltage is applied to such a thyristor valve, the gapless arrester 3 -1.3-+1 is activated and protection is provided.

Furthermore, when the thyristor valve is turned on, the turn-on delay time (td) of each thyristor varies, so there is a possibility that an overvoltage will be applied to the thyristor with a large td. This overvoltage (called turn-on overvoltage) is VTH
If exceeded, the thyristor will be damaged, but
In this protection method, a gapless arrester connected in parallel with the thyristor operates and the thyristor is protected.

In this way, this one-step method can suppress not only the overvoltage applied to the entire thyristor valve but also the overvoltage applied to each of the thyristors connected in series.

However, such conventional protection systems have the following drawbacks. In other words, in the unlikely event that a gate pulse is not input to a specific thyristor due to a failure in the pulse transmission system, the main circuit current (for DC power transmission converter In the case of a thyristor valve, a direct current (direct current) will flow. It is possible to design a gapless arrester to withstand the extremely large amount of energy consumed by such a continuous current by connecting gapless arresters in parallel, but the number of connections becomes large and is impractical. On the other hand, if the gapless arrester only has the ability to absorb ordinary, single-shot surge energy, the energy of the main circuit current may cause thermal runaway, which may even lead to an explosion.

In order to prevent such problems, it is necessary to install a device that detects heat generation of the gapless arrester and short-circuits between the terminals of the gapless arrester when the main circuit current flows through each gapless arrester. Such a device is large in size and weight, and not only greatly exceeds the size and weight of a thyristor valve, but also causes a short circuit if it is activated, so it is equivalent to reducing the number of thyristors in series by one. The remaining Si risk will increase the voltage stress of other components.

[Object of the Invention] The object of the present invention is to eliminate such conventional drawbacks and to obtain a small, compact, and highly reliable overvoltage protection system for a thyristor valve.

[Summary of the Invention] The present invention provides a safe overvoltage protection system that uses a VBO free thyristor as a thyristor and connects a thyristor and a gapless arrester via an impedance, without providing a special explosion-proof device for the gapless arrester. It has a built-in overvoltage protection system for Iristor valves.

[Embodiment of the Invention] An embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows an embodiment of the present invention, in which the same numbers as in FIG. 2 indicate the same parts. 4-1.4-n are 11 VBo free thyristors connected in series. 5-1, 5-(1
+, /2) is a resistor or an n/2 impedance consisting of a parallel circuit of a resistor and a capacitor, and is inserted between the parallel-connected gapless arrester such as the VBO freezer resistor.

Setting of the protection level of such a thyristor valve will be explained with reference to FIG. FIG. 4 shows the constant level maintained by the thyristor valve of the present invention, where the vertical axis shows the voltage and the horizontal axis shows the current. The protection level (VAr) of each kitotsubu breath arrester is VBO free thyristor is VBO
Voltage (VBO) J: Set low. Further, assuming that the minimum operating current flowing through the thyristor valve is 11, the impedance 5 is determined by J, which satisfies the following equation.

VBOVAr −1−< I s X Z ) −(1
) where Z is the impedance of impedance 5 [
Ω] When an overvoltage is applied to such a thyristor valve, the thyristor valve arrester 3-1.3-n operates in series) against the overvoltage applied to the entire thyristor valve, and V[
30 Free Cyrisk to protect against overvoltage. Also VB
If the dynamic voltage imbalance of the O free thyristor is large, the capless arrester connected in parallel with the VBO free thyristor to which the overvoltage is applied operates to protect the VBO free thyristor. In this case, since the impedance 5 is connected in series with the gapless arrester 3, the protection level increases by the voltage drop. If the overvoltage is in the forward direction, this increase is not a problem because the VBO free-circuit will self-ignite, but if the overvoltage is in the reverse direction, it becomes a problem. On the other hand, focusing on the fact that the dynamic imbalance is extremely rapid in terms of time, if we create a parallel circuit of a resistor and a capacitor with an impedance of 5, the capacitor will have a low impedance for high frequencies. , it is possible to reduce the above-mentioned increase in Kiyoshi A level.

Furthermore, VBO Freezer Lister 4-1, 4. -n, there is only one (consider the case where no turn Δ is performed and all the remaining VBO Freezer resistors are turned on. Main circuit °
Current flows through the gapless arrester and impedance connected in parallel with the VBO freezer resistor that did not turn on. At this time, the voltage applied to the VBO free thyristor becomes (1) on the right side, which is higher than the VBO voltage, so the BO free thyristor turns on by itself. Therefore, after that, 11? The main circuit current does not flow to the Tsuburasu arrestor, but all flows through the VBO free thyristor.
Gapless arresters do not run away with heat.

In addition, as an example of the present invention, the impedance 5 is set to VB
Although we have shown the case in which the O-free thyristor and the gapless arrester are connected at every other connection point, it is clear that the effect will be the same even if the connection point is connected to all the connection points.

[Effects of the Invention] According to the present invention, thermal runaway can be prevented without installing a special short-circuiting device for the break arrester, even in a situation where damage occurs. Thyristor valves are smaller and lighter than conventional ones, and the number of series-connected thyristors can be effectively used. It can be made into a high quality raw material.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of VBO Free 1 Noislisk, Fig. 2 is a simplified circuit diagram of a conventional J Ilisk valve, Fig. 3 is a simplified circuit diagram of a thyristor valve according to an embodiment of the present invention, and Fig. 4 is a simplified circuit diagram of a conventional J Ilisk valve. 1 is a protection coordination curve of a thyristor valve for detailed explanation of the invention; 4-1.4-n...VBO Freezerista, J'1
．． 3n...Gapless arrester, 5-1゜5-(T
I/2)...impedance. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (2)

[Claims] (1) In a thyrisk valve in which a plurality of thyristors having a self-ignition function in response to a forward voltage are connected in series or in series-parallel, a gapless arrester is provided in parallel with each thyristor in parallel via an impedance. i
Thyristor valve overvoltage protection device with ff. (2) The overvoltage protection device for a silicate valve as set forth in claim 1, wherein the impedance is a parallel circuit consisting of a resistor and an electric conductor.