CN104064964B - A kind of method preventing magnetic storm, core pulse from electrical network being endangered - Google Patents

Abstract

The invention discloses a kind of method preventing magnetic storm, core pulse from electrical network being endangered, comprise the following steps: 1) grounded screen of power plant grid side transmission line of electricity neutral point is independent of full factory grounded screen, and keep at a distance with full factory site net；2) main transformer of transformer substation both sides need neutral ground, and its grounded screen ensures the most independent, and keeps at a distance；The present invention changes the mode of independent grounding by the way of being joined directly together by the common ground net of the transformer neutral point in current AC synchronous electrical network with power plant or transformer station into, block the metallicity interface channel of geomagnetic induction current GIC, thus make geomagnetic induction current local absorption, it is to avoid the danger that GIC focuses on release at one and damages.

Description

A method for preventing solar magnetic storms and nuclear pulses from harming power grids

technical field

The invention relates to a method for preventing solar magnetic storms and nuclear pulses from harming power grids.

Background technique

As we all know, power grids are divided into synchronous power grids and asynchronous power grids. A power grid connected by an AC transmission line is a synchronous power grid. If there is no other AC connection line between two power grids connected by a DC transmission line, the two power grids are asynchronous. Of course, if there is no tie line between the two grids, the two grids are of course independent and of course asynchronous. With the development of UHV technology in China, regional power grids are interconnected through UHV AC or DC lines. The power grid connected by UHV AC will constitute a larger-scale AC synchronous power grid, and the security of the synchronous power grid is becoming increasingly important. The reason why my country develops UHV AC and DC networking technologies at the same time actually reflects the concern about the safety of the ultra-large synchronous AC power grid.

Although the power grid has a history of more than 100 years, and all aspects of technology are very mature, but with the expansion of the grid scale, some very complex and difficult to explain problems have emerged, such as solar magnetic storms and geomagnetic induced currents (GIC) The issue of the impact on the power grid has been studied by the State Grid Corporation of China as a major scientific and technological project, but the cause and propagation mechanism of GIC have not been clarified, and no specific solutions have been proposed. If the blackout in the United States in 2000 was a chain event caused by the overload of the key contact line of the power grid, the blackout in Canada and North America in 1984, although 30 years have passed since the incident, and there are many research reports, the cause of the accident has not been concluded. . Only the origin of a series of tripping events was found out, and the zero-sequence protection of a main transformer acted first. The essence of the zero-sequence protection action is that the current of the power grid flowing from the neutral point to the earth suddenly increases. Different from my country's power grid protection concept, Western power grid protection devices have always been simple and reliable. Therefore, it can be said that the sudden increase in zero-sequence current in this accident is certain. As for why the current suddenly increased, there is no in-depth analysis and analysis. reports. However, according to many relevant research data, it was a period of intense sunspot activity that year, and the aurora in Canada and the Arctic region was extremely strong, reflecting the large-scale impact of solar ions on the earth. Although there is a shielding effect of the earth's magnetic field, a large number of ions inevitably still penetrate the earth The magnetic field reaches the earth's surface, and because of the wide coverage and long distance of the power grid, the solar ions absorbed by it must flow through the leakage circuit. Since the solar ions are positively charged, the ion current formed in the power grid has the characteristics of aperiodic and impact, and must leak to the earth through the path with the least impedance, and the neutral point grounding grid is directly grounded. Therefore, the solar magnetic storm The induced current (geomagnetic induction current GIC) flows to the earth through the neutral point of the transformer. The impact mechanism of the pulsed radiation produced by nuclear bombs on the power grid is similar to this.

An indisputable fact that has been ignored by the industry is that the DC resistance between any two grounding grids on a synchronous power grid whose neutral point is directly grounded is actually very small, and its magnitude is the internal resistance of the transmission line conductor and the grounding resistance. The internal resistance of the grid is much smaller than the resistance between any two points in the soil. Therefore, for the solar magnetic storm current, the power grid is actually a metal conductor, and the magnetic storm current must leak at the place with the smallest resistance to the ground.

In fact, there is a deep layer of permafrost in the northern part of Canada, and the electrical conductivity of the permafrost is extremely low. The impact current of the magnetic storm must be transferred to the southern region to find a discharge point. Well, then this is the biggest victim point. Therefore, it can be inferred that the blackouts in Canada and North America in 1984 were probably caused by the zero-sequence current flow protection of key transformers caused by solar magnetic storms.

In the above analysis, the grounding method of the neutral point becomes the key to the problem. It is precisely because the neutral points of the high and low voltage sides of the transformer are connected together through the grounding grid that the grounding grid of the large power grid has a metallic interconnection. For DC transmission lines, when single-stage operation occurs, one pole is the overhead line and the other pole is the ground grid. Because there is a gradient voltage between the grounding grid and the surrounding soil, the current flows in the grounding grid and the surrounding soil. If this DC current corridor is close to the substation, a large DC current must flow into the grounding grid of the substation and continue through the AC line. spread far. This phenomenon was also reported in the commissioning report of my country's first DC transmission line. Some papers have reported that when the DC transmission system of Yueling Nuclear Power Station is in single-stage operation, the noise of the main transformer of the plant increases greatly, and the neutral point current reaches 30A. In fact, due to the high design standard of the grounding grid of nuclear power plants and close proximity to the sea, the grounding effect is naturally good, which naturally causes part of the DC component in the power grid to flow to the ground through this point. The direct phenomenon of the neutral point current flowing through the transformer winding is that the transformer noise increases. The DC current flows through the transformer, which will increase the noise and shorten the life of the transformer, or damage the winding insulation and cause major accidents.

Therefore, the above analysis shows that the grounding method of the neutral point of the main transformer of the directly grounded AC power grid plays an important role in the solar magnetic storm disaster, the single-stage operation of DC power transmission, and the negative effects on the power grid when the nuclear bomb explodes. The present invention is exactly a solution that proposes at the above problems.

Contents of the invention

In order to solve the above problems, the present invention proposes a method for preventing solar magnetic storms and nuclear pulses from harming the power grid. The method directly connects the neutral point of the transformer in the current AC synchronous power grid with the public grounding grid of the power plant or substation Changing to an independent grounding method blocks the metallic connection channel of the geomagnetic induction current (GIC), thus allowing the geomagnetic induction current to be absorbed locally, avoiding the danger of damage caused by the concentrated release of the GIC.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for preventing solar magnetic storms and nuclear pulses from harming power grids, comprising the following steps:

1) The grounding grid at the neutral point of the transmission line on the power grid side of the power plant is independent of the grounding grid of the whole plant, and keeps a distance from the grounding grid of the whole plant;

2) If the neutral point grounding is required on both sides of the main transformer of the substation, the grounding grids shall be independent and keep a distance.

In the step (1), the specific method is: the grounding grid at the neutral point of the power grid side transmission line of the power plant is independent of the grounding grid of the whole plant, and is an independent grounding body buried in the soil, and there is no metal connection with the public grounding grid of the power plant. Connection, the distance between the two is more than 10 meters, and the characteristic parameters of the independent grounding body meet the current national standards.

Described step (2), its specific method is: the two sides of substation main transformer need neutral point grounding, its grounding network is independent respectively, and both are the independent grounding bodies buried in the soil, the distance between the two is More than 10 meters.

The working principle of the present invention is: divide the entire power grid from a large metal body into a section of isolated metal body, the non-periodic impact current on the power grid in one region will never spread to other regions, so it will not form a global Sexual large current, there is no harm of inrush current.

The beneficial effects of the present invention are:

1. The viewpoint that the AC synchronous power grid proposed by the present invention constitutes a large metal conductor through the interconnection of the neutral point grounding grid explains the reason why the geomagnetic induction current flows in a large range, and also explains that the unipolar operation of the DC transmission line is serious to the AC power grid The cause of the impact.

2. The independent method of the neutral point grounding grid proposed by the present invention has solved the difficult problem that the geomagnetic induction current spreads in a large scale by the ground grid-overhead wire (or cable) in the power grid;

3. The independent method of the neutral point grounding grid proposed by the present invention reduces the impact of DC unipolar operation on the AC grid

Description of drawings

Fig. 1 is the independent grounding diagram of the neutral point of each link of the transmission line of the present invention;

Fig. 2 is a schematic diagram of non-independent grounding of the neutral point of each link of the transmission line of the present invention;

Fig. 3 is a schematic illustration illustrating the propagation of the magnetic storm induced current through the neutral point connection of the main transformer in the present invention.

Among them, 1. Generator; 2. Step-up transformer; 3. Transmission line; 4. Main transformer of substation.

detailed description:

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

At present, the neutral point grounding method of domestic and foreign power grids adopts the method shown in Figure 2. According to this connection method, the lines in a synchronous power grid, the main transformer winding, the metal grounding grid, the main transformer windings of each power station, and the grounding grid of the power station are all connected together. That is to say, the entire power grid is actually a metal conductor. When solar ions hit the power grid in a certain area, this positive potential, non-periodic, and DC charge must spread to the rest of the large metal body of the power grid, and which Where the soil has high electrical conductivity and fast diffusion, the neutral point current will be large wherever the grounding effect is. Therefore, the neutral point current is the largest in the place with the best grounding effect, and the damage is also the most serious. Judging from the current distribution of power stations and power sources in my country, the neutral point current is the largest in nuclear power plants, power stations near the sea, and places with underground metal deposits. Therefore, the distribution of metal deposits across the country can also be drawn by detecting the neutral point current. A new method is provided for the field of prospecting.

According to our research results, the neutral point grounding network of the main transformer of the 1000MW unit of the third phase project of Shandong Laiwu Power Plant is being transformed according to the scheme shown in Figure 1, including generator 1, step-up transformer 2, and transmission line 3 and substation main transformer4. Once the grounding grid transformation scheme shown in Figure 1 is completed, the entire power grid will be divided into a section of isolated metal bodies by a large metal body, and the non-periodic impulse current on the power grid in one area will never spread to other areas. Therefore, a global large current will not be formed, and there will be no harm of inrush current.

If the solar magnetic storm is a kind of natural disaster unpredictable, then, if there is a nuclear war in the future, the ion shock produced by a small nuclear bomb explosion can completely knock down the current power grid. To limit the damage to a small range, so as not to cause long-distance and large-area surges. Therefore, this method has great practical significance.

The method proposed by the sub-invention can be further described below in conjunction with FIG. 1 .

As shown in Figure 1, G0 is the public grounding network of the power plant, G1 is the neutral point independent grounding network of the main transformer grid side of the power plant step-up station, G2 and G3 are the neutral point grounding network on both sides of the substation, respectively, Of course, according to existing standards, if the low-voltage side is below 110kV, the neutral point does not need to be grounded. In Figure 1, only the Z-phase iron core of the step-up station transformer is connected to G0, but in fact, all three-phase iron cores are connected to G0. In Figure 1, G0, G1, G2, and G3 are independent grounding grids. Although G0 and G1 are close to each other, they can be considered to have no influence on each other electrically due to the separation of soil. Therefore, there is no direct metallic connection between the grid and the power plant. After adopting the independent neutral point grounding network of G1 and G2 in the intermediate transmission line, the intermediate line itself has no metal connection with other power stations at both ends, and the transmission line becomes an electrical island, which completely cuts off the geomagnetic induction current. Propagation channels in the grid.

On the contrary, as shown in Figure 2, the current neutral point grounding method. It can be seen from Figure 2 that the grounding grid G1 of the substation and the grounding grid G0 of the power plant are connected by metal. Therefore, the GIC from the left side of the substation can go directly to the ground grid of the power plant. This also explains why the neutral point current of nuclear power plants is large. Because the grounding resistance of the nuclear power plant grounding grid near the sea is much smaller than that of the inland substation.

As shown in Figure 3, the principle of magnetic storm induced current propagation. Figure 3 simplifies the three-phase line into an equivalent zero-sequence loop. The main grounding network of the substation at the four key contact points on the network, g1 and g2 represent the neutral point grounding network at both ends of a 220 tie line in the power plant at A, and g3 and g4 represent the transformers at both ends of a 220kV load line at B Sex point ground grid. According to the current grounding standard, G1～G4 are actually connected by metal, not only that, because G1 and g1 are also connected, and G3 and g3 are also connected, so the grounding grid g2 at point A and the grounding grid g4 at point B are connected, therefore, the neutral point current on the entire network can flow to the ground through G1~G4 and g1~g4. However, due to the different geological conditions of the grounding grids in various places, the neutral point current cannot be evenly distributed on the eight grounding grids, and the current at the grounding grid with the smallest resistance to the ground must be the largest, and the smaller the resistance to the ground, the more current it flows through. The greater the current, the more the victim of the magnetic storm current.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (2)

1. A method for preventing solar magnetic storms and nuclear pulses from harming electrical grids is characterized in that it may further comprise the steps: 1) The grounding grid at the neutral point of the transmission line on the power grid side of the power plant is independent of the grounding grid of the whole plant, and keeps a distance from the grounding grid of the whole plant; 2) If the neutral point grounding is required on both sides of the main transformer of the substation, the grounding grids shall be independent and keep a distance; It is independent of the grounding grid of the whole plant and is an independent grounding body buried in the soil, and has no metal connection with the public grounding grid of the power plant. The distance between the two is more than 10 meters, and the characteristic parameters of the independent grounding body meet the current national standards. 2. A kind of method for preventing solar magnetic storm and nuclear pulse from harming the power grid as claimed in claim 1, is characterized in that: described step (2), its specific method is: both sides of transformer substation main transformer need neutral point grounding , the grounding grids are independent, and both are independent grounding bodies buried in the soil, and the distance between the two is more than 10 meters.