Converting substation

FIELD: electricity.

SUBSTANCE: invention is used in electric engineering. Converting substation for power plant system connecting to bipolar HVDC transmission line has DC neutral plant ensured with the first DC switches (131, 132) allowing for disconnecting the first current circuit between neutral bus (112) of the first conductor (105) and a neutral bus (111) of the other conductor (104) when substation operates in bipolar mode and switching to single-polar mode of operation, if needed. In order to isolate faulty section in system, current circuit with connecting elements (142, 143) of electrode line to direct current from the said conductor (105) to another one, there are split connection elements (142, 143) available for each electrode line (191, 192). There is a special device to connect each neutral bus to one selected connecting elements of electrode line.

EFFECT: improved reliability of power transmission.

9 cl, 4 dwg

The technical field to which the invention relates

The present invention relates to a Converter substations to connect the system to AC (alternating current) to the bipolar transmission lines HVDC (high voltage direct current), while the substation contains two converters, each of which has side DC (direct current)which is connected on the one hand, respectively to the two conductors of said transmission line on high potential and on the other to the zero bus, to which the conductor installation neutral DC common to the converters grounded to zero potential, and the AC side connected to the said AC system; the installation of a neutral DC has connection element with two electrode lines and the setting made with the first switch, providing the opening of the first circuit, located between the neutral bus of one of the conductor and the neutral bus of another Explorer, in bipolar mode of operation of the substation, for changes in the unipolar mode, the station also includes a control device for controlling the said change from bipolar to unipolar mode of operation, by control of the first-mentioned switch DC for tripping mentioned circuit between the two neutral buses, and the mouth is the service circuit to the above-mentioned connecting element electrode line, for the direction of the electric current from the conductor to the other. This change to a unipolar mode of operation will allow you to isolate the faulty section of the system and switch to the reverse wire.

The level of technology

The invention is not limited to certain levels of the voltages between ground and each of the conductors of the transmission line HVDC (high voltage direct current), but it is particularly applicable to such stresses as above 500 kV, which implies that the transmission line transmits considerable energy, and the transmission system belongs to the transforming substation requires a high level of reliability. The invention is not a limitation of any aggregate levels of electric current passing through the said conductors of the transmission line, but said line preferably nominally designed for electric current above 1 kA.

The generic design of the HVDC transmission system of this type is schematically shown in figure 1. It shows how the transforming substation installed on each end of the line (3) HVDC transmission having two conductors 4, 5, one of which has positive and one negative polarity. System 6, 6' connected to AC Converter stations through transformers 7, 7' for the approach is a corresponding voltage level of the system DC. The AC system may be generating system, in the form of some type of power plant generators of electricity, or consumer system, or network to connect to electricity consumers, such as businesses or residential areas. Each Converter substation has two Converter 8, 9, each of which has a DC side connected to one side of said conductors 4, 5, respectively, and on the other, to a common transducer installation 10 neutral DC, connected to low voltage and closed to the earth, to restrict the voltage on each conductor. Each transducer 8, 9 may be replaced by a set of probes consisting of two or three connected in series, to obtain a high voltage, which may be of the order of 800 kV. The converters include a number of the current valves in any known configuration, such as 12-pulse bridge configuration. The converters can be linearly commutated converters, current source, in which switching elements such as thyristors are turned off at the zero crossing of the AC, the AC system. Converters can also be forced commutated converters voltage source, in which the above-mentioned switching ele the coefficients are switching devices, managed according to the widely-width modulation (PWM).

The advantage of HVDC transmission system relative to the AC transmission system is a significant reduction of the resulting losses in the transmission line between the two Converter stations at each end of these lines, with Converter stations are mainly more expensive in the power transmission system HVDC than in the AC transmission system. However, the HVDC transmission system is mainly used to transmit high power, usually of the order of several GW, over long distances, such as hundreds of kilometers. This means that the consequences for the connected AC systems can be very serious if the two wires of the transmission line will break, there will be disconnected as a result of undesirable simultaneous ground fault. If referred to the AC system belongs to the main system, the supply of electricity to a large city, such bipolar disconnection may lead to a large decrease electric power supplied to said main system that will create instability in the system, and can then cause damage to other parts. Consequences for connecting the AC system in case of breakdown of one of the conductor are not half in seriousness, as if they were cut off both of the conductor. The crust is ASEE the invention is considered by the criterion of reliability is relatively described in the introductory part of the Converter substations, mentioned setting neutral DC are functionally similar, and typical installation neutral known DC Converter stations shown in figure 2. This installation 10 has a neutral bus 11 connected to the low voltage side of a Converter 8, and a neutral bus 12 connected to the low voltage side of the other of the transducer 9. Neutral bus connected to each other through the serial connection of the two first switches 13, 14 DC and dividers 15, 16 associated with each switch 13, DC 14. The midpoint 17 of this series connection between the first switch DC and disconnector related to one another neutral bus, connected to the circuit line 18, which includes disconnectors connected to the element 19, is connected to two electrode lines 20, 21, coming from the Converter station to the electrode station 22, which will be described below. Installation 10 neutral DC also includes a grounding switch 23 connected through line includes switches, outlets 24, 24' between the first switch DC and disconnector related to each neutral bus 11, 12.

The function of Converter stations, with this known installation the neutral DC, shown in figure 2, the following. During operation in the bipolar mode conversion at the station operates as a rectifier, electric current from the conductor 5 having a negative polarity, goes to the Converter 9 and then through the neutral bus 12 to the neutral bus 11, while the first switches 13, 14 and switches 15, 16 are closed. The electric current then passes through the inverter 8 to another conductor 4 of the HVDC transmission line with a positive polarity in accordance with the arrows 25. Disconnectors on line 18 leading to the connecting element electrode line 19, are closed, thereby establishing a zero potential of the neutral.

Assume that the conductor 4 side DC happened undesirable short circuit, figure 3 illustrates how to act the transforming substation and, in particular, the installation of a neutral DC. Current valves of the Converter 8 will then be blocked roundabout pairs, and that means serially connected current valves are included and, thus, the AC side is bypassed to protect the system 6 AC and attached equipment. These bypass pair will form a connection with low resistance between the conductor 4 DC and installation of neutral DC. Points shown as an electric current will pass to undesirable circuit 26 to the ground. It is important to quickly isolate the unwanted circuit 26 to the ground to keep the other conductor is 5. Disconnectors line 18 are closed for the formation of a circuit on the connecting element 19 of the electrode line and then through the electrode lines 20, 21 to the electrode station 22. An electric current conductor DC 5 is thus distributed between the two current circuits: through electrode line on the ground and through another conductor 4 to unwanted short circuit. About half of the electric current will go on each of the two circuits. To isolate unwanted shorted to ground, the first switch 13 DC opens, thus, all the electric current will pass through the electrode line on the electrode station. When the switch 13 DC is open, the switches 15 and 15' on the neutral bus, as well as the switch 27 on the conductor 4, the current path to provide isolation of the faulty conductor 4.

If the switch 13 DC fails and does not reduce the electrical current to zero, i.e. commutes electric current to the electrode lines, it will be re-closed. The grounding switch 23 is then closed as a reserve for the switch 13 DC, when forming the connection of low resistance between the neutral bus 12 and ground. Almost all of the electric current "healthy" Explorer 5 will then go to the network station grounding, and a value of electric current in another conductor 4 BU the em thus, to decrease almost to zero, so that the dividers 15, 27 and 15' may then be opened to perform the isolation. When the conductor 4 is isolated, the grounding switch 23 is opened, and the entire electric current is switched on the electrode line. The transforming substation and transmission system HVDC then operates in unipolar mode, so half of that power in bipolar mode can still be delivered. As soon as possible, usually within about a minute, connect the neutral bus 12 to the conductor 4 is a circuit disconnectors and switches, directing electric current, in accordance with arrow 28 on the reverse wire instead of grounding through electrode station, if there is a need to maintain a unipolar mode of operation of the system without power on the earth electrode station.

The various components of the installation neutral DC will be the same if unwanted ground fault happens on the other conductor 5, in this case, the switch 14 and the switch 16 will open to the deviation of the electric current to the electrode station and so on.

Installation is neutral a famous DC Converter stations provides sufficient reliability, but at the same time has some drawbacks. It is impossible to separate the two electrode the line, this means that in case of an earth fault of one of them will be a failure just connect to the electrode station, which will lead to a bipolar system shutdown. It is also impossible to test properly each electrode line when not in use. Another disadvantage is that the ground selector switch, described above, is the provision for each of the first switch 13, 14, and circuit raises the potential of the grounding network as a result of high values of the passing of an electric current. Neutral point of transformer Converter stations connected to the ground network, and the growth of its potential makes the DC current through the transformer, and thus the risk off of another conductor. Another disadvantage is the inability to perform service first switch DC in bipolar mode Converter stations.

The invention

The present invention is the creation of Converter stations, related to the type described in the introductory part, and which eliminates at least one of the above disadvantages of this known Converter stations.

This task, in accordance with the invention, is achieved by creating such a Converter postans and, in which the installation of a neutral performed with individual mentioned connecting elements for each of the electrode lines, and means for connecting each neutral bus to the selected connecting elements of the two electrode lines. This reduces the risk of bipolar outage HVDC transmission system, which essentially belongs to the transforming substation, since it is possible to separately test the functionality of each electrode line and connected equipment during bipolar operation mode Converter stations, which ensures the functioning of these electrode lines properly immediately upon insertion. In addition, in the event of an unwanted short-circuit to ground one of the electrode lines during a change in the unipolar mode of operation, consider the neutral bus is connected via the said means to the other electrode lines, and faulty electrode line will be isolated to avoid dangerous situations in the unipolar mode.

In accordance with the embodiment of the invention the said means of connection holds for each neutral bus on the first line separate from the first mentioned circuit including the first switch DC and connects the bus to the od of the WMD of the connecting elements of the electrode line, associated with this bus, at least one switch and/or switch DC, and on the second line, cross-cutting mentioned the first two lines located closer to the corresponding bus than the location mentioned above, at least one switch and/or switch, at least one disconnector and circuit breaker DC. This means that each neutral bus can work through the above mentioned switch DC and/or disconnector connected to a selected one of the connecting elements of the electrode line or to both of them, to disable any of the electrode lines, unwanted shorted to ground, one of them, and to isolate unwanted circuit to earth or even to check the status or maintenance in unipolar mode.

In accordance with another embodiment of the invention mentioned cross-cutting the second line is made with switch DC connected in series with the switches located on each side about it.

In accordance with the following embodiment of the invention the said means of connection holds for each first line connecting the neutral bus to one of the mentioned connecting element electrode line, a serial connection of DC switches and disconnect the lei, more closely situated to consider a neutral bus than the connection point cross-cutting the second line to the first line. This means that the next circuit having at least two switch DC connected in series, can be installed between the two neutral buses, next to the first current circuit, this means that during bipolar operation mode Converter stations can be performed the service mentioned first switch DC first mentioned circuit, and this circuit. In addition, the above-mentioned second line is made with switch DC, which also functions as a reserve for the two switches DC first mentioned lines.

In accordance with another embodiment of the invention mentioned setting neutral contains additional second switch DC connected in series with the first-mentioned switch DC in said first circuit between these two neutral buses in bipolar mode of operation of the substation. This means that these two switches DC, is connected in series to function as a backup for each other in cases where it is necessary to break circuit to discard the electric current to the electrode station that will allow avoi is ü circuit switch ground if one of the switches will not be able to reduce electrical current to zero.

In accordance with another embodiment of the invention, the mid-point between the said first and second switch DC in the above-mentioned first circuit is connected through the first switch to the middle point of the line, cross-cutting mentioned two conductor transmission line HVDC, while the first mentioned switch is designed to be open in bipolar mode of operation of the substation, the line correlation of these two conductors is made with dividers on both sides on the said mid-point, and the above-mentioned control device configured to control circuit mentioned first disconnector and disconnector that connects one of the conductors to the circuit return line with a different conductor, when the unipolar mode of operation of the substation after disabling referred to one of the conductor.

In accordance with another embodiment of the invention the transforming substation includes a ground selector switch connected to the first mentioned circuit between the two neutral buses at a point between the said switch DC and said additional switch DC. This is done for additional reserve in case the first is AK, as the second switch DC, malfunction, which, however, is unlikely.

In accordance with another embodiment of the invention mentioned control device is arranged to control the said DC switches and disconnectors in each of the aforementioned first line and said second cross-cutting lines for the circuit and install a second circuit between the two neutral buses through the first mentioned line and the above-mentioned cross-cutting the second line, to allow maintenance equipment, such as a switch in said first circuit in bipolar mode of operation of the substation.

In accordance with another embodiment of the invention, the station is designed to connect the AC system to a bipolar HVDC transmission line, designed for voltages between each conductor and ground greater than 200 kV, mainly above 500 kV, preferably 600 kV - 1500 kV and more preferably 600 kV - 1000 kV. The transforming substation according to the invention mainly more interesting for higher voltage and, thus, to a higher power transmitted through the transmission line HVDC, which also means higher reliability requirements.

Other benefits as well as benefits what s the features of the invention, will be provided from the following description.

Brief description of drawings

Below follows a specific description of the Converter stations in accordance with the embodiment of the invention with reference to the accompanying drawings.

In the drawings:

Figure 1 - simplified schematic view illustrating the General construction of the HVDC transmission system.

Figure 2 is a circuit diagram illustrating the construction of the installation of a neutral DC, part of the known Converter stations transmission system HVDC.

Figure 3 - view of the installation of a neutral DC in accordance with figure 2, is used to explain its operation, when a ground fault occurs on the conductor.

4 is a view similar to figure 2 installation the neutral DC Converter stations, corresponding to the implementation of the present invention.

Detailed description of a variant embodiment of the invention

Two conductors in this case denoted by 104 and 105 and two neutral bus through 111 and 112. The conductors 104, 105 in this case have polarity +800 -800 kV and kV, respectively. Neutral bus 111, 112 are connected to each other through the first circuit 130, in which the first switch 131 DC and the second switch 132 DC connected in series. Each of these switches DC surrounded by two disconnectors 133-136.

The switch 170 grounding is connected to the first mentioned circuit 130 between the two switches 131, 132 DC associated with the dividers, the first circuit 130 is also connected through switch 180 to the midpoint of the line 181, cross-cutting mentioned two conductors 104, 105 of the HVDC transmission line. This switch 180 is adapted to be open when the bipolar mode of operation of the substation. Cross-cutting line between the two conductors is made with two switches 182, 183 on either side of the midpoint.

Also shows the location of ammeters, such as 210, to monitor the functioning of various the t install the neutral DC. Also the figure shows a capture filter 211 and the injection circuit 212 for measuring the resistance of the electrode line.

The purpose of this installation neutral following. When the power transmission system high voltage direct current, including electric Converter substation operates in bipolar mode, the electric current passes between two neutral buses in the first circuit 130, with closed switches 131, 132 DC and disconnectors 133-136, as well as through the second circuit, while passing through the closed switches 144, 145 DC and dividers 146-149, and closed switch 151 DC and dividers 152, 153 of the second line 150. Disconnectors 160, 161 are closed to connect the electrode to the station with the said neutral busbar to determine the polarity. Maintenance of all equipment of this unit neutral is now possible without turning off the bipolar mode. The DC switches in said first circuit 130 can be opened for inspection or service, while an electric current is passed between the two neutral buses through the second circuit on the second line 150. The proper functioning of the equipment in the second circuit can also be tested, in this case the electric current through two neutral bus will be popularuty first electrical circuit 130. It is also possible to check the equipment of the two electrode lines and perform maintenance on the equipment of the first electrode lines at the same time without any risk that disconnecting one wire can cause bipolar disable the Converter stations. When performing maintenance, for example, switch 131 DC in bipolar mode Converter stations two switch 133 and 134 are opened after you open switch 131 DC. The same scheme is used to switch 132 DC.

Suppose that an undesirable short circuit as described above with reference to figure 3, occurred on the conductor 104. The switch 144 DC in this case will be closed with switch 151 DC as a backup, in case the switch 144 DC will re-close. In addition, the first switch 131 DC is controlled to open, and when this happens, the electric current will decrease to zero, will also be open one of the switches 133 or 134. However, if the first switch 131 DC fails, the second switch 132 DC will function as a reserve, being open manageable. Additionally to reserve ground selector switch 170 will operate as described with reference to Fig. 3.

Electric current from the neutral bus 112 will go on connecting ale is applying to ingredients 142, 143 electrode line, and through them to the electrode station 190. Switch 151 DC re-closed if necessary to provide a reserve for the switch 144 DC. However, if a ground fault has occurred on the first electrode line 191 or related equipment, the connection between the neutral bus 112 and a connecting element 142 of the electrode line will be interrupted by means of the control switch 151 DC to unlock and then open any of the dividers 160, 152 and 153. And in the case of a ground fault on another electrode line 192 or related equipment can be operated switch 161 and the entire electric current with neutral bus 112 is placed on the connecting element 142 of the electrode line.

Once the defective sector is isolated, the switch 180 and the switch 182 can be shorted to output an electric current through the reverse wire on the conductor 104, while the connection is interrupted neutral bus 112 to the electrode station 190 in order not to hold too high an electric current to the grounding electrode of the station.

In other cases, the invention is certainly not limited to the embodiment described above, and allows many possibilities to modifications by a person with ordinary skill without deviating from the basic idea of the invention in suitable the following paragraphs in the accompanying claims.

For example, in the above-mentioned first circuit may be not two, but a different number of series-connected switches DC.

In addition, for example, it is permissible to have more than two coupling element electrode lines, to connect more than two electrode lines connected to equipment with a neutral tires.

1. The transforming substation for connection of the system (6) speakers, bipolar line (3) HVDC transmission, these substation contains two transducer (8, 9), each of which has a DC side connected to one side respectively with two conductors (104, 105) of the said transmission line on high potential and on the other with neutral tires (111, 112), for which the conductor installation 10 neutral DC common to the converters grounded to zero potential, and the side of the speakers connected to the said system speakers, install neutral DC has the element connecting two electrode lines (191, 192)when this setting is made with the first DC switches, enabling them to break the first circuit (130)disposed between the neutral bus of one of the conductor and the neutral bus of another conductor in bipolar mode of operation of the substation for changes in unipolar mode, the station also contains a control device (200), performed in what zmoznostjo management mentioned the change from a bipolar to a unipolar mode of operation using the first control switch (131) DC, for tripping mentioned circuit, located between the two neutral buses (111, 112), and a connection circuit of the said connecting element electrode line to the direction of the current from one conductor to another, characterized in that the installation of a neutral performed with a separate connecting element (142, 143) for each of these electrode lines, and means for connecting each neutral bus (111, 112) with the selected connecting elements of the two electrode lines.

2. The transforming substation according to claim 1, characterized in that the said means of connection holds for each referred to the neutral bus on the first line (140, 141), separate from the first circuit includes a first switch DC, and connects the bus to one of the connecting elements (142, 143) of the electrode line connected to this bus, at least one disconnector (160, 161) and/or switch DC, and on the second line (150), cross-cutting mentioned the first two lines, more closest to the corresponding bus than the location mentioned above, at least one switch and/or switch, at least one disconnector (152, 153) and switch DC (151).

3. The transforming substation according to claim 2, characterized in that the said second cross-cutting line (150) is accomplished with a switch (151) DC, connected in series with the switch (152, 153), located on each side about it.

4. The transforming substation according to claim 2 or 3, characterized in that the said means of connection holds for each of the first line (140, 141), connecting the neutral bus (111, 112) with one of the connecting elements (142, 143) of the electrode line, serially connected switch (144, 145) DC disconnector (146-149), located more closely to consider a neutral bus than the connection point cross-cutting the second line with the first line.

5. The transforming substation according to claim 1, characterized in that the installation of a neutral DC contains additional second switch (132) DC connected in series with the first switch (131) DC mentioned in the first circuit (130)between the two neutral buses for bipolar mode of operation of the substation.

6. The transforming substation according to claim 5, characterized in that the middle point between the first (131) and second (132) switch DC in the first circuit (130) is connected through the first switch (180) to the midpoint of the line (181), cross-cutting the two wires (104, 105) referred to the HVDC transmission line, and the first switch adapted to be open when the bipolar mode of operation of the substation, the line correlation'll mention what's the two conductors made with disconnector (182, 183) on both sides referred to the mid-point, and the above-mentioned control device configured to control the first switch (180) for the circuit, and a switch that connects one of the conductors to the circuit to the reverse wire of the electric current from the other of the conductor in unipolar mode of operation of the substation after disabling referred to one of the conductor.

7. The transforming substation according to claim 5, characterized in that it contains a switch (170) ground connected to the first mentioned circuit (130) between the two neutral buses (111, 112) at the point between the first-mentioned switch (131) DC and said additional second switch (132) DC.

8. The transforming substation according to claim 4, characterized in that the said control device is arranged to control the said switches (144, 145, 151) DC and disconnectors (146-149, 152, 153) mentioned in each of the first line, and said second cross-cutting lines, circuits, and installation of a second circuit between the two neutral buses (111, 112) via the first line (140, 141) and the above-mentioned cross-cutting the second line (150) to ensure maintenance of equipment, such as switch (131, 132) DC in the first circuit (130) in bipolar mode of operation of the substation.

9. The transforming substation at p., characterized in that it is made with the possibility to connect the AC system to a bipolar HVDC transmission line, designed for voltages between each conductor and ground greater than 200 kV, mainly above 500 kV, preferably 600 to 1500 kV, and most preferably 600 to 1000 kV.