CN204928103U - A device for fast switching between earth return line and metal return line in double twelve-pulse direct current transmission system - Google Patents

Abstract

The utility model relates to a device of earth return wire and metallic return wire quick switching among two twelve pulsating direct current transmission systems for including the two twelve pulsating direct current transmission systems of converter station more than both ends or both ends with the help of direct current line connection, each converter station direct current side includes: the high-low voltage valve group bypass circuit breaker, the neutral bus switch, the metal loop conversion circuit breaker, the metal loop switch and the isolating switch for the metal loop; in the process of rapid switching, when the high-low pressure valve group bypass circuit breaker at the sending end and the receiving end is in a closed state, one path of current flows through the ground return wire, and the other path of current flows through the metal return wire through the high-low pressure valve group bypass circuit breaker; when the metal return line conversion circuit breaker is in an off state, current only passes through the metal return line; when the metal loop of the locking pole is in a closed state by the isolating switch and the metal loop switch of the sending end, and the high-low voltage valve group bypass circuit breaker is in an open state, the current flows to the metal loop again.

Description

A device for fast switching between earth return line and metal return line in double twelve-pulse direct current transmission system

technical field

The utility model belongs to the technical field of electric power electronics, in particular to a device for fast switching between a ground return line and a metal return line in a double-twelve pulsation direct current transmission system.

Background technique

There are many modes of operation for the DC transmission system, including bipolar operation, single pole ground return line operation, and single pole metal return line operation. When one pole of DC is overhauled or fails, the other pole can continue to operate through the single-pole ground loop operation mode, which greatly improves the reliability of the DC transmission system. However, long-term geodetic operation has the following disadvantages:

(1) The DC current flows into the transformer through the neutral point of the AC system transformer, causing the transformer to generate DC bias, which seriously affects the normal operation of the transformer;

(2) Excessive ground current will cause corrosion to metal components and pipelines along the way;

(3) Excessive ground current will affect the ecological environment near the ground electrode.

Therefore, in order to reduce the operating time of the single-pole ground loop mode caused by faults and reduce the impact on the system and ecology, in the event of a fault, the operation mode of the single-pole ground loop automatic transfer to the single-pole metal loop mode is the best choice in the DC transmission system. very important. At the same time, when there is no grounding pole or the grounding pole is unavailable, when a single-pole lockout occurs, the conversion from the single-pole ground return line to the single-pole metal return line must be completed quickly.

The existing earth-to-metal scheme needs to use an isolating switch for the metal return line to form a current path. Due to the slow action speed of the isolating switch, the closing and opening time are in seconds, and it is difficult to realize the rapid connection between the earth return line and the metal return line. convert. During the conversion process, there will be a large ground current, which will have a bad impact on the surrounding power equipment and the ecological environment near the ground electrode. In the case that there is no grounding pole or the grounding pole is unavailable, if the rapid conversion from the earth return line to the metal return line cannot be realized, it will cause double-pole blocking and reduce the reliability and stability of the system.

Utility model content

The purpose of this utility model is to solve the problem of the need to realize the conversion of the earth return line to the metal return line when a single-pole outage occurs in a direct current transmission project, and provides a ground return line and metal return line in a double-twelve pulse direct current transmission system. The method of fast conversion of the loop line is used to improve the system reliability and stability of the DC transmission project and reduce the impact of the ground current on the surrounding power equipment and the ecological environment.

In order to achieve the above purpose, the solution proposed by the utility model is to provide a device for fast switching between the earth return line and the metal return line in the double-twelve pulsation direct current transmission system, which is used to include two ends or two ends connected by means of a direct current line In the above double-twelve-pulse direct current transmission system of the converter station, the direct current side of each converter station includes: the high and low voltage of the first pole connected in series between the metal return line of the first pole of the earth return line The valve group bypass circuit breaker and the neutral bus switch of pole 1; the high and low voltage valve group bypass circuit breaker of pole 2 and the neutral bus of pole 2 connected in series between the metal return line of pole 2 of the earth return line switch; the metal return line transfer circuit breaker, set on the earth return line; the metal return line changeover circuit breaker, set between the metal return line changeover circuit breaker and the neutral bus switch of pole one and the neutral bus switch of pole two; There is an isolating switch for the metal circuit of pole one, and the metal circuit switch is connected to the metal return line of pole one through the isolating switch for the metal circuit of pole one; The switch is connected to the metal return line of the second pole with an isolating switch through the metal circuit of the second pole; wherein, during the rapid conversion process between the earth return line and the metal return line, when the high and low pressure valve groups at the sending end and the receiving end are bypassed and disconnected The device is in the closed state, so that one current flows through the earth return line, and the other current flows through the metal return line through the high and low voltage valve group bypass circuit breaker; when the metal return line conversion circuit breaker is in the open state, the current Only through the metal return line; when the isolating switch for the metal circuit of the blocking pole and the metal circuit switch at the sending end are in the closed state, and the bypass circuit breaker of the high and low voltage valve group is in the open state, so that the current passes through the blocking pole After the said metal loop of the sending end is switched by an isolating switch and said metal loop of the sending end, it flows to the metal loop.

As a preferred solution, the direct current transmission system refers to a double twelve-pulse UHV direct current transmission system.

The utility model takes into account the characteristics of the UHV DC transmission system. With the help of the original high and low voltage valve group bypass switch of the UHV DC transmission, through simple operation steps, the rapid conversion of the earth return line to the metal return line is realized, and the direct current is greatly reduced. Inflow time.

The utility model utilizes the existing DC high-speed switch to perform rapid ground-to-metal operation without increasing equipment investment, which can greatly reduce the time for DC current to enter the ground and reduce the impact on surrounding facilities. At the same time, when there is no grounding pole or the grounding pole is unavailable, it can improve the reliability of the system, reduce the probability of bipolar blocking, and increase the stability of the system.

Description of drawings

Fig. 1 is a schematic diagram of the operation flow of the method for fast conversion of the earth return line and the metal return line in the dual-twelve pulsating direct current transmission system of the present invention;

Fig. 2 is the schematic diagram of the current path after the unipolar fault is blocked in the dual-twelve pulsating direct current transmission system of the present invention;

Fig. 3 is a schematic diagram of the current path after the bypass circuit breakers of the high and low voltage valve groups of the two stations in the dual-twelve pulsating direct current transmission system of the present invention are closed;

Fig. 4 is a schematic diagram of the current path after the metal loop conversion circuit breaker is disconnected in the double-twelve pulsating direct current transmission system of the present invention;

Fig. 5 is a schematic diagram of the final current path after all the conversions from the earth return line to the metal return line in the dual-twelve pulsating direct current transmission system of the present invention are completed.

Detailed ways

The following will describe in detail a device for fast switching between earth loops and metal loops in a double-twelve pulsation direct current transmission system proposed by the present invention with reference to the accompanying drawings and specific embodiments.

This embodiment is aimed at the double-twelve-pulse UHVDC power transmission system. The DC power transmission system includes two ends connected by means of a DC line and converter stations above both ends. The DC side of each converter station includes a neutral bus switch HSNBS, Metal circuit breaker MRTB, metal circuit isolation switch, metal circuit switch MRS and high and low pressure valve group bypass circuit breaker BPS, etc.

In order to realize the rapid conversion from the earth return line to the metal return line, the direct current transmission system of the utility model adopts the following steps:

S01, when single-pole blocking occurs due to failure or maintenance (in this embodiment, pole one is blocked, that is, pole one is the blocking pole), the DC current passes through the neutral bus switch HSNBS, the metal return transfer circuit breaker MRTB and The grounding electrode line (the grounding electrode line is the earth return line) is finally connected to the ground, as shown in Figure 2; at this time, it is necessary to judge whether the fast conversion between the earth return line and the metal return line is allowed, and if it is allowed, enter the fast conversion process;

S02, disconnect the incoming circuit breakers of the converter transformer at the sending end and the receiving end (not shown);

S1, close the high and low voltage valve group bypass circuit breakers at the sending end and the receiving end, so that one current flows through the ground electrode line, and the other current flows through the high and low voltage valve group bypass circuit breaker BPS at pole one through the DC Pole line (the DC pole line is the metal return line, which is simply marked as "pole line" in the drawings); in other words, the DC current is redistributed between the ground pole line and the DC pole line, as shown in Figure 3 shown;

S2, disconnecting the metal return transfer circuit breaker MRTB, so that the current only passes through the DC pole line; The high and low pressure valve group bypass circuit breaker BPS flows to the DC pole line of pole one to complete the rapid conversion from the earth return line to the metal return line, as shown in Figure 4;

S3, closing the isolating switch for the metal circuit of pole one, and closing the metal circuit switch at the sending end, so that the current flows through the isolating switch for the metal circuit of the blocking pole and the metal circuit switch at the sending end, DC polar line;

S4, disconnect the high and low voltage valve group bypass circuit breaker of pole one, at this time, the DC current flows to the DC pole line of the blocking pole through the neutral bus switch HSNBS, the metal circuit switch MRS and the isolating switch for the metal circuit of the blocking pole in sequence . It should be understood that at this time, it is also necessary to disconnect the isolating switch of the bypass circuit breaker of the high and low pressure valve group and the metal circuit transfer circuit breaker. So far, the conversion from the earth return line to the metal return line has been completed, as shown in Figure 5.

If in other embodiments, the pole 2 is a blocking pole, the method of fast switching between the earth return line and the metal return line is similar, and those skilled in the art can make an analogy based on the spirit of the utility model.

The utility model takes into account the characteristics of the UHV DC transmission system. With the help of the original high and low voltage valve group bypass circuit breaker BPS of the UHV DC transmission, through simple operation steps, the rapid conversion from the earth return line to the metal return line is realized, which greatly reduces the Small direct current into the ground time, reducing the impact on surrounding facilities. At the same time, when there is no grounding pole or the grounding pole is unavailable, it can improve the reliability of the system, reduce the probability of bipolar blocking, and increase the stability of the system.

The above described embodiments are more specific and detailed, but they should not be construed as limiting the patent scope of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the scope of protection of the utility model patent should be based on the appended claims.

Claims (2)

1. the device of Ground return and metallic return rapid translating in two 12 pulsating direct current transmission systems, for comprising described two 12 pulsating direct current transmission systems of the current conversion station at more than the two ends or two ends that connect by DC line, it is characterized in that, described in each, current conversion station DC side comprises:

The height pressure valve group bypass breaker of pole one between the metallic return being connected to the pole one of Ground return, series connection and the neutral bus switch of pole one;

The neutral bus switch of pole two between the metallic return being connected to the pole two of Ground return, series connection height pressure valve group bypass breaker and pole two;

Metallic return conversion circuit breaker, is arranged on Ground return;

Metallic(return) circuit switch, between the neutral bus switch being arranged on metallic return conversion circuit breaker and the neutral bus switch of pole one, pole two;

Be provided with the metallic(return) circuit isolating switch of pole one in pole one, and metallic(return) circuit switch is connected with the metallic return of isolating switch with pole one by the metallic(return) circuit of pole one;

Be provided with the metallic(return) circuit isolating switch of pole two in pole two, and metallic(return) circuit switch is connected with the metallic return of isolating switch with pole two by the metallic(return) circuit of pole two;

Wherein, among Ground return and metallic return fast transition process,

When the described height pressure valve group bypass breaker of sending end and receiving end is at closure state, make a road electric current flow through Ground return, another road electric current flows through metallic return by described height pressure valve group bypass breaker;

When described metallic return conversion circuit breaker is in off-state, make electric current only through metallic return;

When the described metallic(return) circuit isolating switch of locking pole and the described metallic(return) circuit switch of sending end are at closure state, and described height pressure valve group bypass breaker is in off-state, make electric current after the described metallic(return) circuit isolating switch of locking pole and the described metallic(return) circuit switch of sending end, then flow to metallic return.

2. Ground return and the device of metallic return rapid translating in 12 pulsating direct current transmission systems as claimed in claim 1 two, is characterized in that, described DC transmission system refers to that two 12 pulse extra-high voltage DC transmission systems.