Railway power supply system 27.5 kV, 50 or 60 Hz for narrow-gauge railway traffic, measures to improve load symmetry in the feeding high-voltage network

Abstract

1 Designation Railway power supply system 27.5 kV, 50 or 60 Hz for long-distance rail traffic, measures to improve load symmetry in the feeding high-voltage network. 2 Summary 2.1 Technical Problem Conventional electrical substations for the power supply of long-distance railways at 27.5 kV / 50 Hz or 60 Hz cause a non-negligible negative feedback effect in the feeding high-voltage system 21 due to unbalanced loads. 2.2 Solution to the Problem Instead of the conventional V-connection of two single-phase transformers in a railway power system 2 x 27.5 kV, 50 Hz or 60 Hz, the use of two three-phase transformers T21 and T22 with connection groups Dz0 and Dz4 or Zd0 and Zd8 is proposed as a solution. See the attached drawing Figure 5 2 for an example.3. Application Areas The primary application area is the 2 x 27.5 kV / 50 Hz or 60 Hz power supply for electric railways in long-distance operation, relevant IPC classifications: B60L 3 / 00, B60M 3 / 00, H02J 3 / 26, H02M 5 / 10. Furthermore, it is applicable in electrometallurgy, relevant IPC classifications: H05B 7 / 00, H02J 3 / 26, H02M 5 / 10. Other larger single-phase or unbalanced electrical loads supplied from three-phase networks. Figure 5 shows, as one of the solution approaches, the structure of a typical substation in a simplified representation, with transformers T21 or T22, Zd8 or Zd0 connected.

Description

[0001] The various substation designs in the field of railway power supply, in this case for long-distance railways, are presented and described in the aforementioned book. State of the art

[0002] The current state of the art is illustrated in the following figures and is then described in more detail: Fig. 1: State of the art / Structure of a typical 2 x 27.5 kV substation Fig. 2: State of the art / Circuit and phasor diagram of transformers T11 and T12

[0003] Fig. Figure 1 shows, in simplified form, the typical structure of an electrical substation for supplying long-distance electric railways with the railway voltage 2 x 27.5 kV, 50 Hz or 60 Hz, roughly according to the current state of the art. The rated power of such a 2 x 27.5 kV substation is typically on the order of 2 x 60 MVA.

[0004] Along an electrically operated railway line, several electrical substations of this type are typically installed, spaced up to 50 km apart. These substations draw their electrical energy either from a common high-voltage system or from different high-voltage systems, depending on availability.

[0005] The two single-phase transformers T11 and T12, each with a typical rated power of 60 MVA, are connected to this high-voltage system 01 in a V-connection on the primary side. On the secondary side, these transformers T11 and T12 are connected to the overhead contact line system, consisting of the contact line CL (+27.5 kV) and the negative feeder conductor NF (-27.5 kV). The plus and minus signs indicate the opposite phase angles of the two railway voltages. The two middle secondary taps 2N of transformers T11 and T12 are connected to each other and to the directly grounded rail RT (rail track) and are therefore at earth potential.

[0006] Furthermore, it is on Fig. Figure 1 shows that in a 2 x 27.5 kV system, the electric railway vehicle 04 is supplied with railway voltage +27.5 kV via the overhead line CL. The conductor NF, running parallel to the railway line and carrying railway voltage -27.5 kV, also contributes to the power supply of the electric railway vehicle 04. This occurs, among other things, via the autotransformers AT distributed along the railway line.

[0007] The single-phase alternating current I supplied by the electrical substation reaches the onboard electrical drive equipment M via the pantograph 05 of the electric railway vehicle 04. Finally, the current I flows from there via the running gear 06 of the electric railway vehicle and via the running rails RT back to the substation. Fig. Figure 2 illustrates the circuit of transformers T11 and T12 and the corresponding phasor diagram. The latter shows a phase angle discrepancy of 60° between the secondary terminals 2U and 2V, which carry +27.5 kV, and between the secondary terminals 2U' and 2V', which carry -27.5 kV. This necessitates the use of phase-separating measures in the overhead line system: on the one hand, a Fig. 1 shown neutral zone 03 between the overhead line sections CL left and right of the connection points 2U and 2V, respectively, and on the other hand a phase separation point 02 between the conductor sections NF left and right of the connection points 2U' and 2V'.

[0008] The in Fig. The moving railway vehicle 04, shown on the right, causes a one-sided, temporary load on the right overhead line section and thus, via transformer T12, a one-sided load on phases V and W of the high-voltage system 01, resulting in a load imbalance. A load imbalance would also occur if railway vehicle 04 were to move to the left side and the resulting power supply were to be routed via the left overhead line section: this time, the one-sided load on phases U and W of the high-voltage system 01 would be via transformer T11.

[0009] The one-sided load condition described above for these electrical substations supplying railway power occurs relatively frequently, as longer train spacings are the norm in long-distance rail operations, meaning that only a few vehicles (04) are often in the substation's feeder area. Due to the necessity of phase-separation measures, the substation is sometimes supplied via only one of the transformers T11 or T12. However, even with simultaneous operation of vehicles (04) on both sides, certain load imbalances would still occur in the high-voltage system (01), since the... Fig. The V-circuit of two single-phase transformers shown in Figure 1 is not necessarily beneficial in this sense.

[0010] Load imbalances pose a problem for both the operation of the affected high-voltage system 01 and the connected users. Line capacity remains unused, leading to increased current loads and losses in the grid and in connected consumers. Power plant generators and transformers can also be affected. Therefore, the grid operator specifies compatibility levels for imbalances, which must be adhered to.

[0011] Several patents already exist in the field of power supply for electric railways for long-distance transport, in which measures to maintain load symmetry in the supplying high-voltage network are proposed, including: • EP 0 967 109 A1 / 29.12.1999 Substation for supplying two sections of an electrified railway network • DE 10 2008 012 325 A1 / 10.09.2009 Device for connecting a single-phase supply line to a three-phase supply network • DE 10 2014 217 300 A1 / 03.03.2016 Order for connecting a railway power supply for a railway line to a three-phase supply network • EP 3 161 930 B1 / 10.03.2021 Order for connecting a railway power supply for a railway line to a three-phase supply network

[0012] The solutions presented therein are primarily based on adding inductive or capacitive loads or relying on balancing devices. Both of these solutions differ fundamentally from the proposal described here. Exemplary embodiment with transformers of switching groups Dz0 and Dz8

[0013] This embodiment is illustrated in the following figures and is explained in more detail below: Fig. 3: Construction of a typical 3 x 27.5 kV substation with transformers Dz0 and Dz8 Fig. 4: Transformers Dz0 and Dz8 / Circuit and phasor diagram of transformers T21 and T22

[0014] Fig. Figure 3 shows, in simplified form, the typical setup of an electrical substation for supplying long-distance electric railways with the railway voltage 3 x 27.5 kV, 50 Hz or 60 Hz, using two three-phase transformers of connection groups Dz0 and Dz8. The designation 3 x 27.5 kV indicates that this solution is based on a three-phase railway power system.

[0015] Along an electrically operated railway line, several electrical substations of this type are typically installed, also in this approach, at intervals of up to 50 km. These substations obtain their electrical energy either from a common high-voltage system or from different ones, depending on availability.

[0016] In this case, the two three-phase transformers T21 and T22 are each connected to the high-voltage system 21 on their primary side with all three phases. The rated power of these transformers is also in the range of 60 MVA each.

[0017] Fig. Figure 4 illustrates the circuit of transformers T21 and T22, as well as the corresponding phasor diagram. The latter shows that, due to the 240° phase shift of the secondary-side Z-windings of transformers T21 and T22, their secondary windings have identical phase positions and phase sequences. This allows the secondary connections of both transformers to be connected in parallel, even though they are assigned to different phases on the primary side.

[0018] As on Fig. As can be seen in Figure 3, the secondary terminal 2U of transformer T21 and the secondary terminal 2V of transformer T22, or 2V and 2W, or 2W and 2U, are connected in parallel.

[0019] The resulting connection pairs 2U / 2V and 2W / 2U are connected to the contact line CL (contact line) and the phase feeder PF (phase feeder) of the overhead contact line system, respectively. The 2V / 2W pair is connected to the directly grounded running rails RT (rail track) and is therefore at earth potential. In the configuration described above, the contact line CL, phase feeder PF, and running rails RT form a three-phase 25 kV railway power system, here designated as 3 x 27.5 kV, instead of the one described in Fig. 1 shown, conventional 2 x 25 kV railway power system.

[0020] The single-phase alternating current I supplied by the electrical substation reaches the onboard electric drive M via the pantograph 29 of the electric railway vehicle 28. Finally, the current I flows from there via the running gear 30 of the electric railway vehicle and via the running rails RT back to the substation as an electric return current.

[0021] The contribution of conductor PF to the power supply of the electric railway vehicle 28 is also made, among other things, via the three-phase, delta-connected compensation windings distributed along the railway line, as shown in Fig. 3. Compensation winding CT21 shown. The compensation winding CT21 is connected to the overhead contact line CL and the conductor PF of the overhead line system as well as to the running rails RT and is used in this three-phase 25 kV railway power system instead of the one shown in Fig. The AT11 autotransformer shown in Figure 1 is used in the conventional 2 x 27.5 kV railway power system. The delta-connected compensating winding CT21 enables the flow of compensating currents in the 3 x 27.5 kV railway power network.

[0022] Each of the secondary connection pairs 2U / 2V, 2V / 2W, and 2W / 2U of the two parallel-connected, three-phase transformers T21 and T22 accesses two different phases on the primary side, namely 1U / 1V, 1V / 1W, and 1W / 1U. This represents a significant improvement in the load balance of the high-voltage system 21 compared to the load balance achievable with a conventional electrical substation for railway power supply using single-phase transformers connected in V. The advantage stated in claim 1 would thus be demonstrated by the solution approach described above, based on the use of three-phase Dz0 and Dz8 transformers T21 and T22.

[0023] The delta-connected primary windings of the three-phase transformers T21 and T22 used in this solution are equipped with phase shifters, each connected to the phase-shifted windings. Fig. 3 and Fig. The 4 coils shown A', B' and C' enable fine-tuned phase shifts and thus even more precise load distributions between the three-phase transformers T21 and T22, which in turn benefits the load symmetry in the supplying high-voltage system 21.

[0024] These phase shifters in the form of in Fig. The three changeover switches 27 shown can be operated manually and without load or automatically and under load. In the latter case, the control unit 24 would also be used. This control unit 24 would tap the current and voltage values ​​25 at the respective current transformers 22 and voltage transformers 23, and after evaluating the measured values ​​25, adjust the changeover switches 27 directly and in real time via the control lines 26, according to an optimal load distribution.

[0025] The advantages described here of a more finely graduated load distribution among the three-phase transformers T21 and T22 by means of these phase shifters also correspond to patent claim 1.

[0026] The matching phase angle and phase sequence of the parallel-connected secondary windings of both three-phase transformers T21 and T22 enable the provision of 27.5 kV railway voltages with a uniform phase angle at the overhead contact line CL or the PF conductor of the overhead line system, or at the running rails RT. The installation of the in Fig. The neutral zone 03 and phase separation point 02 shown in Figure 1 are therefore omitted. The solution approach described above thus demonstrates the advantage stated in claim 2.

[0027] This solution, based on a three-phase 3 x 27.5 kV railway power system, also includes the use of delta-connected compensation coils, as in Fig. 3 marked with C21. They allow the flow of compensating currents and replace those in Fig. Figure 1 shows the T11 autotransformers of conventional 2 x 27.5 kV railway power systems. The advantages gained through the use of these compensation coils correspond to claim 3. Exemplary embodiment with transformers of switching groups Zd0 and Zd4

[0028] This embodiment is illustrated in the following figures and is explained in more detail below: Fig. 5: Construction of a typical 3 x 27.5 kV substation with transformers Zd0 and Zd4 Fig. 6: Transformers Zd0 and Zd4 / Circuit and phasor diagram of transformers T21 and T22

[0029] Fig. Figure 5 shows, in simplified form, the typical setup of an electrical substation for supplying long-distance electric railways with the railway voltage 3 x 27.5 kV, 50 Hz or 60 Hz, using two three-phase transformers of connection groups Zd0 and Zd4. The designation 3 x 27.5 kV indicates that this solution is based on a three-phase railway power system.

[0030] Along an electrically operated railway line, several electrical substations of this type are typically installed, also in this approach, at intervals of up to 50 km. These substations obtain their electrical energy either from a common high-voltage system or from different ones, depending on availability.

[0031] In this case, the two three-phase transformers T21 and T22 are each connected to the high-voltage system 21 on their primary side with all three phases. The rated power of these transformers is also in the range of 60 MVA each.

[0032] Fig. Figure 6 illustrates the circuit of transformers T21 and T22, as well as the corresponding phasor diagram. The latter shows that, due to the 120° phase shift of the secondary-side delta windings of transformer T21 and transformer T22, their secondary windings have identical phase positions and phase sequences. This allows the secondary connections of both transformers to be connected in parallel, even though they are assigned to different phases on the primary side.

[0033] As on Fig. As can be seen in Figure 5, the secondary terminal 2U of transformer T21 and the secondary terminal 2W of transformer T22, or 2V and 2U, or 2W and 2V, are connected in parallel.

[0034] The resulting connection pairs 2U / 2W and 2W / 2V are connected to the contact line CL (contact line) and the phase feeder PF (phase feeder) of the overhead contact line system, respectively. The 2V / 2U pair is connected to the directly grounded running rails RT (rail track) and is therefore at earth potential. In the configuration described above, the contact line CL, phase feeder PF, and running rails RT form a three-phase 25 kV railway power system, here designated as 3 x 27.5 kV, instead of the one described in Fig. 1 shown, conventional 2 x 25 kV railway power system.

[0035] The single-phase alternating current I supplied by the electrical substation reaches the onboard electric drive M via the pantograph 29 of the electric railway vehicle 28. Finally, the current I flows from there via the running gear 30 of the electric railway vehicle and via the running rails RT back to the substation as an electric return current.

[0036] The contribution of conductor PF to the power supply of the electric railway vehicle 28 is also made, among other things, via the three-phase, delta-connected compensation windings distributed along the railway line, as shown in Fig. 5. Compensation winding CT21 shown. The compensation winding CT21 is connected to the overhead contact line CL and the conductor PF of the overhead line system as well as to the running rails RT and is used in this three-phase 25 kV railway power system instead of the one shown in Fig. The AT11 autotransformer shown in Figure 1 is used in the conventional 2 x 27.5 kV railway power system. The delta-connected compensating winding CT21 enables the flow of compensating currents in the 3 x 27.5 kV railway power network.

[0037] Each of the secondary connection pairs 2U / 2W, 2V / 2U, and 2W / 2V of the two parallel-connected, three-phase transformers T21 and T22 accesses two different phases on the primary side, namely 1U / 1W, 1V / 1U, and 1W / 1V. This represents a significant improvement in the load balance of the high-voltage system 21 compared to the load balance achievable with a conventional electrical substation for railway power supply using single-phase transformers connected in V. The advantage stated in claim 1 would thus be demonstrated by the solution approach described above, based on the use of three-phase Zd0 and Zd4 transformers T21 and T22.

[0038] The delta-connected secondary windings of the three-phase transformers T21 and T22 used in this solution are equipped with phase shifters, each connected to the phase-shifted windings. Fig. 5 and Fig. The 6 coils shown a', b' and c' enable fine-tuned phase shifts and thus even more precise load distributions between the three-phase transformers T21 and T22, which in turn benefits the load symmetry in the supplying high-voltage system 21.

[0039] These phase shifters in the form of in Fig. The five switches 27 shown can be operated manually and without load or automatically and under load. In the latter case, the control unit 24 would also be used. This control unit 24 would tap the current and voltage values ​​25 at the respective current transformers 22 and voltage transformers 23 and, after evaluating the measured values ​​25, adjust the switches 27 directly and in real time via the control lines 26, according to an optimal load distribution.

[0040] The advantages described here of a more finely graduated load distribution among the three-phase transformers T21 and T22 by means of these phase shifters also correspond to patent claim 1.

[0041] The matching phase angle and phase sequence of the parallel-connected secondary windings of both three-phase transformers T21 and T22 enable the provision of 27.5 kV railway voltages with a uniform phase angle at the overhead contact line CL or the PF conductor of the overhead line system, or at the running rails RT. The installation of the in Fig. The neutral zone 03 and phase separation point 02 shown in Figure 1 can therefore be omitted. The solution approach described above thus demonstrates the advantage stated in claim 2.

[0042] This solution, based on a three-phase 3 x 27.5 kV railway power system, also includes the use of delta-connected compensation coils, as in Fig. 5 marked with C21. They allow the flow of compensating currents and replace those in Fig. Figure 1 shows the T11 autotransformers of conventional 2 x 27.5 kV railway power systems. The advantages gained through the use of these compensation coils correspond to claim 3.

Claims

[1] Railway power supply system 27.5 kV, 50 or 60 Hz for long-distance railway traffic, characterized by , that the transformer pair (T21,T22) used in the respective supplying railway power substations has the switching groups Dz0 and Dz8 with a secondary-side phase shift of 240° or the switching groups Zd0 and Zd4 with a secondary-side phase shift of 120°, thereby enabling the secondary-side parallel connection of 2 different phases each (2W / 2U, 2U / 2V, 2V / 2W or 2W / 2V, 2V / 2U, 2U / 2W) and thus improving the load symmetry, also in the supplying high-voltage system (21), characterized by , that the triangular windings of the transformer pair used (T21,T22) in the supplying railway power substations are equipped with phase shifters (27) which further improve the load symmetry in the supplying high-voltage system (21) by means of a fine-tuned phase shift of the individual windings (fine tuning), [2] Railway power supply system according to claim 1, characterized by , that, contrary to the current state of the art, uniform phase angles of the three 27.5 kV railway voltages occur on the secondary side on both sides of the railway power substation and the railway power supply system contains neither neutral zones (03) nor phase separation points (02), [3] Railway power supply system according to claim 1, characterized by , that three-phase 27.5 kV compensation windings (C21) are used along the route and between the electrical railway power substations, which enable the flow of compensating currents between the 27.5 kV conductors (PF, CL) and the running rails (RT) in the railway power network and thus contribute to a more even load distribution among them.

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