Power receiving system

Abstract

To demagnetize a magnetic flux remaining in the iron core of a transformer after cutting-off of the transformer from a special high-voltage power source.SOLUTION: A power reception system comprises: a first transformer that transforms a voltage output from a special high-voltage power source into a prescribed voltage; a switch that connects or cuts off the first transformer to or from the special high-voltage power source; a second transformer that transforms the prescribed voltage transformed by the first transformer into a lower voltage; a variable voltage output power source that can apply a voltage through the second transformer to the first transformer; and a control device that executes control to boost the voltage applied to the first transformer through the second transformer from the variable voltage output power source to a rated voltage over a prescribed time when the voltage output from the special high-voltage power source to the first transformer is cut off by the switch, and then lowers the voltage to a prescribed low voltage over a prescribed time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power receiving system that receives power from an extra-high voltage power supply. [Background technology]

[0002] In a power receiving system that receives power from an extra-high voltage power supply, when a conventional transformer is excited, an excessive excitation inrush current occurs from the primary side of the transformer.

[0003] For example, Patent Document 1 discloses an uninterruptible power supply that prevents saturation of a series compensation transformer to suppress magnetizing inrush current and has high voltage compensation performance.

[0004] Furthermore, Patent Document 2 discloses a magnetic flux control device for effectively reducing residual magnetic flux in a transformer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-295717 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-196124 Summary of the Invention [Problem to be solved by the invention]

[0006] If an excessive inrush current occurs when a transformer is energized, it could cause fluctuations in the system voltage and malfunction of protective relays. Magnetizing inrush current can be suppressed by demagnetizing the magnetic flux remaining in the transformer's iron core.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a power receiving system that can demagnetize the magnetic flux remaining in the iron core of a transformer after the transformer is disconnected from the extra-high voltage power source. [Means for solving the problem]

[0008] A power receiving system according to one embodiment of the present invention comprises a first transformer that converts the voltage output from an extra-high voltage power supply into a predetermined voltage; a first switch that connects or disconnects the extra-high voltage power supply to the first transformer; a second transformer that converts the predetermined voltage converted by the first transformer into an even lower voltage; a variable voltage output power supply that is capable of applying a voltage to the first transformer via the second transformer; and a control device that, when the first switch disconnects the voltage output from the extra-high voltage power supply to the first transformer, controls the voltage that the variable voltage output power supply applies to the first transformer via the second transformer to increase from a low voltage to a rated voltage over a predetermined time, and then decrease the voltage to a predetermined low voltage over a predetermined time, and then controls the first switch to be closed.

[0009] Furthermore, a power receiving system according to one aspect of the present invention includes a first extra-high voltage transformer that converts a voltage output from an extra-high voltage power supply into a predetermined voltage, a first extra-high voltage switch that connects or disconnects the extra-high voltage power supply and the first extra-high voltage transformer, a second extra-high voltage transformer that converts a voltage output from the extra-high voltage power supply into a predetermined voltage, a second extra-high voltage switch that connects or disconnects the extra-high voltage power supply and the second extra-high voltage transformer, a first high voltage switch connected between a low voltage side winding of the first extra-high voltage transformer and a high voltage bus, a second high voltage switch connected between a low voltage side winding of the second extra-high voltage transformer and the high voltage bus, and a power receiving system according to the first extra-high voltage transformer. and a demagnetization circuit busbar; a fourth high-voltage switch connected between the low-voltage side winding of the second extra-high voltage transformer and the demagnetization circuit busbar; a demagnetization transformer having a high-voltage side winding connected to the excitation busbar and a variable voltage output power supply connected to the low-voltage side winding; and a control device that connects one of the first extra-high voltage transformer and the second extra-high voltage transformer that is not connected to the extra-high voltage power supply to the variable voltage output power supply via the demagnetization transformer, and controls the transformer to increase the voltage from a low voltage to the rated voltage over a predetermined time, and then decrease the voltage to a predetermined low voltage over a predetermined time. [Effects of the Invention]

[0010] According to the present invention, after a transformer is disconnected from an extra-high voltage power supply, the magnetic flux remaining in the iron core of the transformer can be demagnetized, and the magnetizing inrush current when the transformer is connected to an extra-high voltage power supply can be suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a first configuration example of a power receiving system according to an embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating a voltage applied by an emergency power supply device. [Figure 3] 4 is a timing chart showing a first operation example of the first configuration example of the power receiving system. [Figure 4] 10 is a timing chart showing a second operation example of the first configuration example of the power receiving system. [Figure 5] FIG. 2 is a diagram illustrating a second configuration example of a power receiving system according to an embodiment. [Figure 6] 10 is a timing chart showing an example of operation of the second configuration example of the power receiving system. [Figure 7] FIG. 10 is a diagram illustrating a third configuration example of a power receiving system according to an embodiment. [Figure 8] 10 is a timing chart showing an example of operation of the third configuration example of the power receiving system. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of a power receiving system will be described below with reference to the drawings. FIG. 1 is a diagram showing a first configuration example of a power receiving system according to an embodiment. As shown in FIG. 1, the first configuration example of the power receiving system according to an embodiment converts power supplied from an extra-high voltage power supply (first commercial power supply) 1 and a low-voltage power supply (second commercial power supply) 2 into predetermined power, and supplies the power to a low-voltage important load 18, a high-voltage general load 19, and a low-voltage general load 20. In this description, in a transformer, the high-voltage side winding connected to the extra-high voltage power supply 1 or a side close to it is referred to as the primary side, and the low-voltage side winding connected to a side close to the low-voltage important load 18, the low-voltage general load 20, and the emergency power supply 3 is referred to as the secondary side.

[0013] The power receiving system also includes an emergency power supply device 3, a control device 30 that controls each component of the power receiving system, a switch 4, a first transformer (extra-high voltage transformer) 5, and a second transformer 50. The switch 4 is an example of a first switch.

[0014] The first transformer 5 converts the voltage output from the extra-high voltage power supply 1 to a predetermined voltage. The switch 4 connects or disconnects the extra-high voltage power supply 1 to the primary side of the first transformer 5. The second transformer 50 converts the predetermined voltage converted by the first transformer 5 to a lower voltage. The emergency power supply 3 is a power supply whose output capacity is smaller than that of the first transformer 5, which is capable of applying a voltage to the first transformer 5 via the second transformer 50, and whose output voltage can be continuously changed from near zero to the rated voltage. For example, it is a variable voltage output power supply with a capacity of 50 to 100 kVA. Furthermore, as a variable voltage output power supply, it may be used in conjunction with an uninterruptible power supply (UPS) with an output voltage adjustment function or an emergency generator with an output voltage adjustment function. "Nearly zero" does not have to be strictly zero, but may be a predetermined low voltage sufficiently lower than the rated voltage (for example, 20%, 10%, or 5% of the rated voltage). Furthermore, the emergency power supply device 3 supplies power to the low-voltage important loads 18 when the extra-high voltage power supply 1 is lost.

[0015] The voltage transformer VT1 detects the voltage, phase, and frequency of the extra-high voltage power supply 1 and outputs the results to the control device 30. The voltage transformer VT2 detects the voltage, phase, and frequency of the low-voltage power supply 2 and outputs the results to the control device 30. The instrument current transformer CT detects the current flowing from the extra-high voltage power supply 1 to the primary side of the first transformer 5 and outputs the results to the protection relay 40.

[0016] Furthermore, the power receiving system is provided with switches 6, 10 to 17. Switch 6 connects or disconnects between the secondary side of the first transformer 5 and the in-house high-voltage bus 8. Switch 16 connects or disconnects between the low-voltage power source 2 and the low-voltage circuit bus B. Switch 13 connects or disconnects between the low-voltage circuit bus B and the important circuit bus A. Each switch is also referred to as a CB (circuit breaker). Switch 11 is an example of a second switch. Switch 13 is an example of a third switch. Switch 14 is an example of a fourth switch. Switch 12 is an example of a fifth switch.

[0017] When the switch 4 cuts off the voltage output from the extra-high voltage power supply 1 to the first transformer 5, the control device 30 controls the voltage applied by the emergency power supply 3 via the second transformer 50 to increase to the rated voltage over a predetermined time, and then decrease to approximately zero over a predetermined time. "Approximately zero" does not have to be strictly zero, but may be a predetermined low voltage (for example, 20%, 10%, or 5% of the rated voltage) that is sufficiently lower than the rated voltage. Even the residual magnetic flux caused by the excitation current commensurate with this is demagnetized. "Approximately zero" and the like hereinafter have similar meanings.

[0018] Here, the primary side of the second transformer 50 is connected to the in-station high-voltage bus 8 via a switch 10. The secondary side of the second transformer 50 is connected to the low-voltage circuit bus B via a switch 12. The emergency power supply 3 is connected to the important circuit bus A via a switch 14, and is connected to the secondary side of the second transformer 50 via a switch 11. The important circuit bus A and the low-voltage circuit bus B are connected via a switch 13.

[0019] The low-voltage important loads 18 are connected to the important circuit bus A. The high-voltage general loads 19 are connected to the in-station high-voltage bus 8 via a switch 15. The low-voltage general loads 20 are connected to the low-voltage circuit bus B via a switch 17. The control device 30 controls the opening and closing of each switch and the operation of the emergency power supply device 3 during power outages and for demagnetization.

[0020] 2 is a diagram showing a schematic diagram of a change in one phase of the AC output voltage of an emergency power supply 3, which is an example of a variable voltage output power supply, when the emergency power supply 3 demagnetizes the residual magnetic flux of the first transformer 5. The horizontal axis represents time, and the vertical axis represents the output voltage of the emergency power supply 3.

[0021] For example, as shown in Figure 2, the control device 30 controls the time required for the emergency power supply device 3 to increase the voltage applied to the first transformer 5 via the second transformer 50 to the rated voltage at the rated frequency, and the time required for the voltage to decrease to zero, so that each is, for example, 5 seconds.

[0022] The period of the waveform shown in Figure 2 is shown schematically, and is therefore longer than the actual period. When demagnetizing the residual magnetic flux, the period of the AC output voltage output from the actual emergency power supply 3 is set to be equal to the period of the AC voltage of the extra-high voltage power supply 1 in normal operation. If demagnetization is simply to be performed, it is sufficient to apply the rated voltage and then gradually reduce the voltage, but if the rated voltage is applied immediately, there is a possibility that an excessively large excitation current will flow due to the residual magnetic flux. Therefore, as shown in Figure 2, the voltage is gradually increased from a low voltage, and after the output voltage has risen to the rated voltage, the voltage is gradually reduced to remove the residual magnetic flux. Demagnetization By doing this, excessive excitation current can be suppressed.

[0023] Next, a more specific example of operation of the first configuration example of the power receiving system will be described below. Fig. 3 is a timing chart showing a first example of operation of the first configuration example of the power receiving system.

[0024] The first operation example is an operation example in which the period from time t1 to time t14 described below falls within the power outage allowable time for low-voltage important load 18, and the horizontal axis of each timing chart represents time. (a) shows the open / closed state of CB4, (b) shows the open / closed state of CB6, (d) shows the open / closed state of CB10, (e) shows the open / closed state of CB11, (f) shows the open / closed state of CB12, (g) shows the open / closed state of CB13, (h) shows the open / closed state of CB14, (j) shows the open / closed state of CB15, (k) shows the open / closed state of CB16, and (m) shows the open / closed state of CB17. In the timing charts (a) to (m), H level indicates the closed state, and L level indicates the open state. Also, (n) indicates the effective value of the voltage of the extra-high voltage power supply 1, (p) indicates the effective value of the voltage of the commercial power supply 2, (q) indicates the effective value of the voltage on the secondary side of the first transformer 5, (r) indicates the effective value of the voltage of the station high-voltage bus 8, (s) indicates the effective value of the secondary side voltage of the second transformer 50, (x) indicates the effective value of the output voltage of the emergency power supply 3, (y) indicates the effective value of the voltage of the low-voltage circuit bus B, and (z) indicates the effective value of the voltage of the important circuit bus A. In other words, the vertical axis of (n) to (z) indicates the effective value of the voltage. Each of (n) to (z) has two levels of dashed lines, with the upper dashed line level being the normal voltage (rated voltage) and the lower dashed line level being the zero voltage level. Note that (p) has only dashed lines and no solid lines because the first operating example of the first configuration example of the power receiving system is an operating example that does not use the low-voltage power supply 2, and therefore the voltage of the low-voltage power supply 2 is arbitrary, so it is shown with dashed lines.

[0025] As shown in Figure 3, in the first configuration example of the power receiving system, when a power outage occurs in the extra-high voltage power supply 1, for example at time t1, the protective relay 40 detects the occurrence of the power outage based on the output of the voltage transformer VT1 and opens CBs (switches) 4, 6, 10, 12, 13, 15, and 17 at time t2.

[0026] Then, when the emergency power supply 3 is ready to start up, the control device 30 closes CB11 at time t3, then closes CB10 at time t4, and then closes CB6 at time t5. Basically, the switches are closed starting from the one closest to the power source, but since there is no voltage, the order of closing the switches from time t3 to t5 may be changed.

[0027] Between times t6 and t7, the control device 30 starts up the emergency power supply 3 as shown in (x) and gradually increases the output voltage up to the rated voltage (see FIG. 2). As a result, the voltage on the secondary side of the first transformer 5 also gradually increases from zero to the rated voltage as shown in (q).

[0028] After that, from time t8 to t9, the control device 30 gradually reduces the output voltage of the emergency power supply 3 to near zero as shown in (x), and then stops the operation. As a result, as shown in (q), the voltage on the secondary side of the first transformer 5 also gradually reduces from the rated voltage to near zero, and after that, the applied voltage is removed. Therefore, the residual magnetic flux of the first transformer 5 also almost disappears and the transformer is demagnetized. Here, gradually reducing the output voltage of the emergency power supply 3 to near zero may mean reducing the output voltage to a predetermined low voltage that is sufficiently lower than the rated voltage (for example, 20%, 10%, or 5% of the rated voltage). The residual magnetic flux due to the excitation current corresponding to this is also demagnetized.

[0029] The control device 30 opens CB6 at time t10, opens CB10 at time t11, and opens CB11 at time t12. Basically, the switches are opened from the one farthest from the power source, but since there is no voltage, the opening order from time t10 to t12 may be changed.

[0030] At time t13, the control device 30 outputs a control or voltage command so that the emergency power supply 3 reaches the rated voltage immediately after startup. Once the output of the emergency power supply 3 has stabilized, the control device 30 closes the CB 14 at time t14 and performs control so that power is supplied from the emergency power supply 3 to the important circuit bus A including the low-voltage important load 18. In this way, the emergency power supply can supply power to the low-voltage important load 18 even when the extra-high voltage power supply 1 is experiencing a power outage.

[0031] At time t15, power is restored to the extra-high voltage power supply 1. When the control device 30 confirms that power has been restored via the voltage transformer VT1, it opens the CB14 at time t16. At time t17, the control device 30 shuts down the emergency power supply 3. Note that the control device 30 may shut down the emergency power supply 3 at a later time, provided that this is after time t16 (i.e., after the CB14 is opened).

[0032] Then, at time t18, control device 30 closes CB4. When CB4 is closed, first transformer 5 is excited from the primary side, but because the residual magnetic flux has been demagnetized by the demagnetization operation from time t8 to t9, it is possible to prevent an excessive excitation current from flowing through first transformer 5. Then, CB6 is closed at time t19, CB10 is closed at time t20, CB12 is closed at time t21, and CB13 is closed at time t22 to supply power from extra-high voltage power supply 1 to low voltage important load 18, and thereafter CB15 is closed at time t23, and CB17 is closed at time t24. The switches are closed in order from the one closest to the power supply.

[0033] The allowable power outage time of the low-voltage important load 18 is set to be longer than the period from time t1 to t14. The period from time t16 (opening of CB14) to t22 (closing of CB13) is set to be shorter than the allowable power outage time of the low-voltage important load 18. The opening of CB14 at time t16 may be set to be later as long as it is before the closing of CB13 at time t22. The period from time t16 to t22 is simply the operation of the switch, and therefore can be shorter than the period from time t1 to t14.

[0034] As described above, according to the first operation example of the first configuration example, it is possible to suppress the magnetizing inrush current of the first transformer 5. Furthermore, it is possible to keep the power outage time of the low-voltage important load 18 within an allowable range.

[0035] Next, a second operation example of the first configuration example of the power receiving system will be described. Figure 4 is a timing chart showing the second operation example of the first configuration example of the power receiving system. This operation example is an example of operation when the low-voltage power supply 2 is available even during a power outage of the extra-high-voltage power supply 1, and the horizontal axis of each timing chart represents time. The horizontal and vertical axes of (a) to (z) in Figure 4 represent the same items as in Figure 3, so their explanation will be omitted. In (p), the periods before time t35 and after t54 are all dashed lines, indicating that the presence or absence of voltage from the commercial power supply 2 during these periods does not affect this operation example and is optional.

[0036] As shown in Figure 4, in the second operation example of the first configuration example of the power receiving system, when a power outage occurs in the extra-high voltage power supply 1 at time t31, the protective relay 40 detects the occurrence of the power outage based on the output of the voltage transformer VT1, and opens CBs (circuit breakers) 4, 6, 10, 12, 13, 15, and 17 at time t32.

[0037] At time t33, the control device 30 controls the emergency power supply 3 so that the rated voltage is reached immediately after startup. At time t34, when the output voltage of the emergency power supply 3 stabilizes, the control device 30 closes the CB 14 and controls so that power is supplied from the emergency power supply 3 to the low-voltage important loads 18.

[0038] At time t35, the control device 30 confirms via the potential transformer VT2 that the voltage of the low-voltage power supply 2 is normal, and at time t36, opens CB14 and closes CB16. The opening of CB14 and the closing of CB16 may be reversed.

[0039] Then, the control device 30 turns on CB13 at time t37 to supply power from the low-voltage power supply 2 to the low-voltage important load 18, temporarily stops the emergency power supply 3 at time t38, turns on CB11 at time t39, turns on CB10 at time t40, and turns on CB6 at time t41.

[0040] Between times t42 and t43, the control device 30 starts up the emergency power supply 3 and gradually increases the output voltage up to the rated voltage (see FIG. 2).

[0041] Thereafter, from time t44 to t45, the control device 30 gradually reduces the output voltage of the emergency power supply 3 to near zero and then stops it. Gradually reducing the output voltage of the emergency power supply 3 to near zero may mean reducing it to a predetermined low voltage that is sufficiently lower than the rated voltage (for example, 20%, 10%, or 5% of the rated voltage).

[0042] The control device 30 opens CB6 at time t46, opens CB10 at time t47, and opens CB11 at time t48.

[0043] Then, when power is restored to the extra-high voltage power supply 1 at time t49, the control device 30, upon confirming the restoration of power using the voltage transformer VT1, opens CB13 at time t50 and opens CB16 at time t51. Then, the control device 30 closes CB4 at time t52. When CB4 is closed, the first transformer 5 is excited from the primary side, but because the residual magnetic flux has been demagnetized by the demagnetization operation from time t44 to t45, it is possible to prevent an excessive excitation current from flowing through the first transformer 5. Thereafter, CB6 is closed at time t53, CB10 is closed at time t54, CB12 is closed at time t55, and CB13 is closed at time t56, thereby supplying power from the extra-high voltage power supply 1 to the low-voltage important load 18. Then, CB15 and CB17 are closed in sequence at time t57.

[0044] The periods during which power cannot be supplied to the important low-voltage load 18 are times t31 to t34, times t36 to t37, and times t50 to t56. The periods t36 to t37 and t50 to t56 are short periods because they are periods during which the switch is operated. In the second operation example of the first configuration example of the power receiving system, power can be supplied to the important low-voltage load 18 during the period from t39 to t48, which corresponds to times t3 to t12 in the first operation example. Therefore, compared to the first operation example, it is possible to shorten the total period during which power cannot be supplied to the important low-voltage load 18. Note that if a power outage occurs in the commercial power source 2 before power is restored to the extra-high-voltage power supply 1 after time 48, CB16 and CB13 can be opened, the emergency power supply 3 can be started, and once the output voltage of the emergency power supply 3 has stabilized, CB14 can be closed, and power can be supplied to the important low-voltage load 18 from the emergency power supply 3.

[0045] As described above, according to the second operation example of the first configuration example, it is possible to suppress the magnetizing inrush current of the first transformer 5. Furthermore, it is possible to keep the power outage time of the low-voltage important load 18 within an allowable range.

[0046] Next, a second configuration example of a power receiving system according to an embodiment will be described. FIG. 5 is a diagram illustrating a second configuration example of a power receiving system according to an embodiment. In the power receiving system illustrated in FIG. 5, components that are substantially the same as those in the power receiving system illustrated in FIG. 1 are assigned the same reference numerals. The configuration differs from FIG. 1 in that the emergency power supply 3 is replaced with an uninterruptible power supply 3a. The uninterruptible power supply 3a has an input and an output. The uninterruptible power supply 3a converts AC power input from the input side into DC power using a converter within the uninterruptible power supply 3a and stores the DC power in a battery within the uninterruptible power supply 3a. The uninterruptible power supply 3a also converts the DC power into AC power using an inverter within the uninterruptible power supply 3a and outputs it from the output side. The uninterruptible power supply 3a may also be referred to as UPS 3a.

[0047] In this description, in the transformer, the high-voltage side winding connected to the extra-high voltage power supply 1 or the side close to it is referred to as the primary side, and the low-voltage side winding connected to the side close to the low-voltage important load 18, low-voltage general load 20, and emergency power supply 3, etc. is referred to as the secondary side.

[0048] 5, a second configuration example of a power receiving system according to an embodiment converts power supplied from an extra-high voltage power supply 1 and a low voltage power supply 2 into predetermined power and supplies the power to a low voltage important load 18, a high voltage general load 19, and a low voltage general load 20. This is a so-called continuous UPS power supply system in which power is supplied to the low voltage important load 18 from an uninterruptible power supply device 3a via an important circuit bus A.

[0049] The power receiving system also includes a UPS 3a, a control device 30 that controls each component of the power receiving system, a switch 4, a first transformer (extra-high voltage transformer) 5, and a second transformer 50.

[0050] The first transformer 5 converts the voltage output from the extra-high voltage power supply 1 into a predetermined voltage. The switch 4 connects or disconnects the extra-high voltage power supply 1 and the primary side of the first transformer 5. The second transformer 50 converts the predetermined voltage converted by the first transformer 5 into an even lower voltage. The UPS 3a is an example of a variable voltage output power supply that is capable of applying a voltage to the first transformer 5 via the second transformer 50.

[0051] Furthermore, the power receiving system is provided with switches 6, 10, 11, 12, 12A, 13 to 17. Switch 6 connects or disconnects between the secondary side of first transformer 5 and in-house high-voltage bus 8. Switch 16 connects or disconnects between low-voltage power source 2 and low-voltage circuit bus B. Switch 13 connects or disconnects between low-voltage circuit bus B and important circuit bus A. Each switch is also referred to as a CB (circuit breaker).

[0052] Here, the primary side of the second transformer 50 is connected to the in-station high-voltage bus 8 via a switch 10. The secondary side of the second transformer 50 is connected to the low-voltage circuit bus B via a switch 12, and is connected to the important circuit bus A via switches 11 and 14. The input side of the UPS 3a is connected to the low-voltage circuit bus B via a switch 12A. The output side of the UPS 3a is connected to the important circuit bus A via a switch 14, and is connected to the secondary side of the second transformer 50 via a switch 11. The important circuit bus A and the low-voltage circuit bus B are connected via a switch 13.

[0053] The low-voltage important load 18 is connected to the important circuit bus A. The high-voltage general load 19 is connected to the in-station high-voltage bus 8 via the switch 15. The low-voltage general load 20 is connected to the low-voltage circuit bus B via the switch 17. The control device 30 controls the opening and closing of each switch and controls the operation of the UPS 3a during power outages and for degaussing. The switch 4 is an example of a first switch. The switch 11 is an example of a second switch. The switch 13 is an example of a third switch. The switch 14 is an example of a fourth switch. The switch 12 is an example of a fifth switch.

[0054] Next, a more specific example of operation of the second configuration example of the power receiving system will be described. Fig. 6 is a timing chart showing an example of operation of the second configuration example of the power receiving system. All horizontal axes indicate time. (a) shows the open / close state of CB4, (b) shows the open / close state of CB6, (d) shows the open / close state of CB10, (e) shows the open / close state of CB11, (f) shows the open / close state of CB12, (g) shows the open / close state of CB13, (h) shows the open / close state of CB14, (j) shows the open / close state of CB15, (k) shows the open / close state of CB16, (m) shows the open / close state of CB17, and (f1) shows the open / close state of CB12A. In the timing charts of (a) to (f1), the H level on the vertical axis indicates the closed state, and the L level indicates the open state. Also, (n) indicates the effective value of the voltage of the extra-high voltage power supply 1, (p) indicates the effective value of the voltage of the commercial power supply 2, (q) indicates the effective value of the voltage on the secondary side of the first transformer 5, (r) indicates the effective value of the voltage of the in-house high-voltage bus 8, (s) indicates the effective value of the voltage on the secondary side of the second transformer 50, (x) indicates the effective value of the output voltage of the emergency power supply 3, (y) indicates the effective value of the voltage of the low-voltage circuit bus B, and (z) indicates the effective value of the voltage of the important circuit bus A. The vertical axes of (n) to (z) indicate the effective values ​​of the voltages.

[0055] In (n) to (z), two levels of dashed lines are drawn, with the upper dashed line level being the normal voltage (rated voltage) and the lower dashed line level being the zero voltage level. In (p), the lines before time t63 and after t83 are all dashed lines, indicating that the presence or absence of voltage from commercial power source 2 during these periods does not affect this operation example and is optional.

[0056] As shown in Figure 6, in the second configuration example of the power receiving system, if a power outage occurs in the extra-high voltage power supply 1 at time t61, the protective relay 40 detects the power outage based on the output of the voltage transformer VT1 and opens CBs (circuit breakers) 4, 6, 10, 12, 15, and 17 at time t62.

[0057] At time t63, the control device 30 confirms that the voltage of the low-voltage power supply 2 is normal using the voltage transformer VT2, and then at time t64, closes CB16 to start receiving power from the low-voltage power supply 2 to the low-voltage circuit bus B.

[0058] At time t65, the control device 30 synchronizes the phase and voltage of the output of the UPS 3a with those of the low-voltage power supply 2, and turns on the CB 13 in synchronization.

[0059] The control device 30 opens CB14 at time t66 after CB13 is activated, controls the supply of power from the low-voltage power supply 2 to the low-voltage important load 18, stops the output of UPS 3a at time t67, activates CB11 at time t68, activates CB10 at time t69, and activates CB6 at time t70.

[0060] Between times t71 and t72, the control device 30 starts up the UPS 3a and gradually increases the output voltage up to the rated voltage (see FIG. 2).

[0061] Thereafter, from time t73 to t74, the control device 30 gradually reduces the output voltage of the UPS 3a to near zero and then stops it. Here, gradually reducing the output voltage of the UPS 3a to near zero may mean reducing it to a predetermined low voltage that is sufficiently lower than the rated voltage (for example, 20%, 10%, or 5% of the rated voltage).

[0062] The control device 30 opens CB6 at time t75, opens CB10 at time t76, and opens CB11 at time t77.

[0063] The control device 30 starts up the UPS 3a at time t78, and at time t79 matches the output phase and voltage of the UPS 3a with those of the low-voltage power supply 2, and synchronizes the CB 14.

[0064] The control device 30 opens CB13 at time t80. This allows the low-voltage important load 18 to again receive power from the UPS 3a. The control device 30 closes CB12A at time t81 and waits until power is restored to the extra-high voltage power supply 1 while charging the battery of the UPS 3a. When the control device 30 confirms, via the voltage transformer VT2 at time t82, that power has been restored to the extra-high voltage power supply 1, it opens CB12A and CB16 at time t83.

[0065] Then, at time t84, control device 30 closes CB4. When CB4 is closed, first transformer 5 is excited from the primary side, but because the residual magnetic flux has been demagnetized by the demagnetization operation from time t73 to t74, it is possible to prevent an excessive excitation current from flowing through first transformer 5. Then, control device 30 closes CB6 at time t85, CB10 at time t86, CB12 at time t87, CB12A at time t88, and then CB15 and CB17 in sequence after time t88 (for example, time t89).

[0066] As described above, according to the operation example of the second configuration example, it is possible to suppress the magnetizing inrush current of the first transformer 5. Furthermore, there is no power outage in the low-voltage important load 18. Note that, although in the above-described embodiment, CB12A is turned on at time t81, if the capacity of the battery in the UPS 3a is large, the turning on of CB12A at time t81 may be omitted and it may be turned on at time t88.

[0067] Next, a third configuration example of a power receiving system according to an embodiment will be described. Fig. 7 is a diagram showing the third configuration example of a power receiving system according to an embodiment. In the power receiving system shown in Fig. 7, components that are substantially the same as those in the power receiving system shown in Fig. 1 are assigned the same reference numerals.

[0068] As shown in Fig. 7, a third configuration example of a power receiving system according to an embodiment converts power supplied from an extra-high voltage power supply 1 into predetermined power and supplies the power to a low-voltage important load (important load) 18, a high-voltage general load 19, and a low-voltage general load 20. In this description, in a transformer, the high-voltage side winding connected to the extra-high voltage power supply 1 or a side close to it is referred to as the primary side, and the low-voltage side winding connected to the side close to the low-voltage important load 18, the low-voltage general load 20, and the emergency power supply 3 is referred to as the secondary side. The emergency power supply 3 is an example of a variable voltage output power supply.

[0069] The power receiving system also has an emergency power supply (variable voltage output power supply) 3, a control device 30 that controls each part of the power receiving system, a first extra-high voltage switch 4-1, a second extra-high voltage switch 4-2, a switch 4-3, a first extra-high voltage transformer (transformer) 5-1, a second extra-high voltage transformer (transformer) 5-2, a degaussing transformer 50-1, a low voltage circuit transformer 50-2, and a degaussing circuit bus 9. The power receiving system also has a first high voltage switch 6-1, a second high voltage switch 6-2, a third high voltage switch 7-1, a fourth high voltage switch 7-2, and switches 10 to 15 and 17.

[0070] The extra-high voltage power supply 1 is connected to a first extra-high voltage switch 4-1 and a second extra-high voltage switch 4-2 via a third extra-high voltage switch 4-3. An instrument current transformer CT is provided on the load side of the first extra-high voltage switch 4-1, and its output is input to a protective relay 40. The first extra-high voltage transformer 5-1 and the second extra-high voltage transformer 5-2 convert the voltage output from the extra-high voltage power supply 1 into a predetermined voltage.

[0071] The degaussing transformer 50-1 and the low-voltage circuit transformer 50-2 convert the predetermined voltage converted by the first extra-high voltage transformer 5-1 or the second extra-high voltage transformer 5-2 into an even lower voltage. The emergency power supply device (variable voltage output power supply) 3 supplies power to the low-voltage important loads 18 in the event of a loss of the extra-high voltage power supply 1, and is an example of a variable voltage output power supply that is capable of applying voltage to at least either the first extra-high voltage transformer 5-1 or the second extra-high voltage transformer 5-2 via the degaussing transformer 50-1.

[0072] The first extra-high voltage transformer 5-1, the second extra-high voltage transformer 5-2, the demagnetizing transformer 50-1, and the low-voltage circuit transformer 50-2 may be referred to simply as transformer 5-1, transformer 5-2, transformer 50-1, and transformer 50-2, respectively. Also, the first extra-high voltage switch 4-1, the second extra-high voltage switch 4-2, the third extra-high voltage switch 4-3, the first high voltage switch 6-1, the second high voltage switch 6-2, the third high voltage switch 7-1, and the fourth high voltage switch 7-2 may be referred to as switch 4-1, switch 4-2, switch 4-3, switch 6-1, switch 6-2, switch 7-1, and switch 7-2, respectively. Furthermore, the first extra-high voltage switch 4-1, the second extra-high voltage switch 4-2 and the third extra-high voltage switch 4-3, the first high voltage switch 6-1, the second high voltage switch 6-2, the third high voltage switch 7-1 and the fourth high voltage switch 7-2 may also be referred to as CB4-1, CB4-2, CB4-3, CB6-1, CB6-2, CB7-1 and CB7-2, respectively.

[0073] The power receiving system is further provided with a first high-voltage switch 6-1, a second high-voltage switch 6-2, a third high-voltage switch 7-1, a fourth high-voltage switch 7-2, and switches 10 to 15 and 17. The extra-high-voltage power source 1 is connected to switches 4-1 and 4-2 via switch 4-3. An instrument current transformer CT is provided on the load side of switch 4-1, and its output is input to protective relay 40. The load side of switch 4-1 is connected to the primary side of a first extra-high-voltage transformer 5-1, and the load side of switch 4-2 is connected to the primary side of a second extra-high-voltage transformer 5-2. The secondary side of the first extra-high-voltage transformer 5-1 is connected to the first high-voltage switch 6-1 and the third high-voltage switch 7-1. The secondary side of the second extra-high-voltage transformer 5-2 is connected to the second high-voltage switch 6-2 and the fourth high-voltage switch 7-2.

[0074] The load sides (sides not connected to the extra-high voltage transformer) of the first high voltage switch 6-1 and the second high voltage switch 6-2 are both connected to the in-station high voltage bus 8. The load sides (sides not connected to the extra-high voltage transformer) of the third high voltage switch 7-1 and the fourth high voltage switch 7-2 are both connected to the degaussing bus 9. The first high voltage switch 6-1 and the second high voltage switch 6-2 make connection or disconnection between the first extra-high voltage transformer 5-1 and the in-station high voltage bus 8, and between the second extra-high voltage transformer 5-2 and the in-station high voltage bus 8, respectively. The third high voltage switch 7-1 and the fourth high voltage switch 7-2 make connection or disconnection between the first extra-high voltage transformer 5-1 and the degaussing circuit bus 9, and between the second extra-high voltage transformer 5-1 and the degaussing circuit bus 9, respectively. Switch 13 makes connection or disconnection between the low voltage circuit bus B and the important circuit bus A. Each switch is also referred to as a CB (circuit breaker).

[0075] Here, the primary side of the demagnetizing transformer 50-1 is connected to the demagnetizing circuit bus 9, and the secondary side of the demagnetizing transformer 50-1 is connected to the emergency power supply 3 via a switch 11. The primary side of the low-voltage circuit transformer 50-2 is connected to the in-station high-voltage bus 8 via a switch 10, and further, the secondary side of the low-voltage circuit transformer 50-2 is connected to the low-voltage circuit bus B via a switch 12 and to the important circuit bus A via a switch 13.

[0076] The emergency power supply device 3 is connected to the important circuit bus A via a switch 14. The important circuit bus A and the low voltage circuit bus B are connected to each other via a switch 13.

[0077] A low-voltage important load 18 is connected to an important circuit bus A. A high-voltage general load 19 is connected to an in-station high-voltage bus 8 via a switch 15. A low-voltage general load 20 is connected to a low-voltage circuit bus B via a switch 17. A control device 30 controls the opening and closing of each switch and the operation of the emergency power supply 3 during a power outage and for demagnetization. There is also an instrument transformer VT1, which detects the voltage of the extra-high voltage power supply 1 and outputs the voltage to the protection relay and control device 30, just like in the first configuration example.

[0078] Next, a more specific example of operation of the third example configuration of the power receiving system will be described. Fig. 8 is a timing chart showing an example of operation of the third example configuration of the power receiving system. All horizontal axes indicate time. (a1) shows the open / close state of CB4-1, (a2) shows the open / close state of CB4-2, (a3) ​​shows the open / close state of CB4-3, (b1) shows the open / close state of CB6-1, (b2) shows the open / close state of CB6-2, (b3) shows the open / close state of CB7-1, (b4) shows the open / close state of CB7-2, (d) shows the open / close state of CB10, (e) shows the open / close state of CB11, (f) shows the open / close state of CB12, (g) shows the open / close state of CB13, (h) shows the open / close state of CB14, (j) shows the open / close state of CB15, and (m) shows the open / close state of CB17. In the timing charts (a1) to (m), the H level indicates a closed state, and the L level indicates an open state.

[0079] Note that (n) indicates the effective voltage of the extra-high voltage power supply 1, (q1) indicates the effective voltage of the secondary side of transformer 5-1, (q2) indicates the effective voltage of the secondary side of transformer 5-2, (r1) indicates the effective voltage of the in-house high-voltage bus 8, (r2) indicates the effective voltage of the demagnetizing circuit bus 9, (s) indicates the effective voltage of the secondary side of low-voltage circuit transformer 50-2, (x) indicates the effective value of the output voltage of the emergency power supply 3, (y) indicates the effective value of the voltage of the low-voltage circuit bus B, and (z) indicates the effective value of the voltage of the important circuit bus A. In other words, the vertical axis of (n) to (z) indicates the effective voltage. Two dashed lines are drawn on each of (n) to (z), with the upper dashed line indicating the normal voltage (rated voltage) and the lower dashed line indicating the zero voltage level.

[0080] In the operational example shown in Figure 8, transformer 5-1 is in operation and transformer 5-2 is in a standby state as an initial state. That is, before time t91, CB4-1 is closed, CB4-2 is open, and power is received via transformer 5-1. CB6-2, CB7-1, CB7-2, CB11, and CB14 are also open. In the third configuration example of the power receiving system, transformer 5-2 is demagnetized from time t91.

[0081] The control device 30 closes CB11 at time t91 and closes CB7-2 at time t92, thereby establishing a circuit connection between the emergency power supply 3 and the secondary side of the transformer 5-2 via the excitation transformer 50-1.

[0082] Between times t93 and t94, the control device 30 starts up the emergency power supply 3 and gradually increases the output voltage up to the rated voltage (see FIG. 2).

[0083] Then, from time t95 to t96, the control device 30 gradually reduces the output voltage of the emergency power supply 3 until it reaches near zero and then stops it. This demagnetizes the residual magnetic flux in the transformer 5-2. Near zero does not have to be strictly zero, but may be a predetermined low voltage (for example, 20%, 10%, or 5% of the rated voltage) that is sufficiently lower than the rated voltage. The residual magnetic flux due to the excitation current corresponding to this is also demagnetized.

[0084] The control device 30 opens CB7-2 at time t97 and opens CB11 at time t98.

[0085] When a power outage occurs in extra-high voltage power supply 1 at time t99, controller 30 causes protective relay 40 to detect the occurrence of the power outage based on the output of potential transformer VT1, and opens CB4-1, 4-3, 6-1, 10, 12, 13, 15, and 17 at time t100.

[0086] The control device 30 starts up the emergency power supply 3 at time t101 and immediately increases the voltage of the emergency power supply 3 to the rated voltage.

[0087] When the control device 30 confirms that the output voltage of the emergency power supply 3 has stabilized, it turns on the CB 14 at time t102 and performs control to start supplying power from the emergency power supply 3 to the low-voltage important load 18.

[0088] When the control device 30 confirms the restoration of power to the extra-high voltage power supply 1 at time t103 from the output of the voltage transformer VT1, it opens CB14 at time t104 and stops the emergency power supply 3 at time t105. Note that the operations at times t104 and t105 may be performed at later times as long as they are before CB13 is closed.

[0089] Then, control device 30 closes CB4-3 at time t106, and closes CB4-2 on the side of transformer 5-2, which has been demagnetized, at time t107. Transformer 5-2 is now excited by extra-high voltage power supply 1, but the residual magnetic flux has been demagnetized by the demagnetization operation performed between times t95 and t96, so the magnetizing inrush current is suppressed.

[0090] Then, the control device 30 turns on CB6-2 at time t108, turns on CB10 at time t109, turns on CB12 at time t110, turns on CB13 at time t111, and turns on CB15 and CB17 in that order at time t112.

[0091] According to the above explanation, while transformer 5-1 is receiving power, the residual magnetic flux of standby transformer 5-2 is demagnetized by emergency power supply 3. When extra-high voltage power supply 1 goes out and then power is restored, power is received by demagnetized standby transformer 5-2, thereby suppressing the magnetizing inrush current. While transformers 5-1 and 5-2 are receiving power, standby transformer 5-1 can be demagnetized in a similar manner. That is, in the time chart of FIG. 6, (a1) should be read as CB4-2, (a2) as CB4-1, (b1) as CB6-2, (b2) as CB6-1, (b3) as CB7-2, (b4) as CB7-1, (q1) as the secondary voltage of transformer 5-2, and (q2) as the secondary voltage of transformer 5-1.

[0092] In this way, in one embodiment of the power receiving system, when the switch interrupts the voltage output from the extra-high voltage power supply to the first transformer, the voltage applied to the first transformer by the variable voltage output power supply via the second transformer is controlled so that it increases to the rated voltage over a predetermined time and then decreases to zero over a predetermined time. This allows the magnetic flux remaining in the iron core of the first transformer to be demagnetized after the first transformer is disconnected from the extra-high voltage power supply. Therefore, when the extra-high voltage power supply is restored from a power outage, excessive magnetizing inrush currents, which can be as large as 5 to 10 times the rated current, generated by the residual magnetic flux in the first transformer, can be suppressed. Furthermore, because the variable voltage output power supply can be used as a power supply source for low-voltage important loads when the extra-high voltage power supply is out of service, costs can be reduced compared to providing a separate emergency power source for the low-voltage important loads.

[0093] In addition, the power receiving system of one embodiment may be configured to include a second switch between the low-voltage winding side of the second transformer and the output of the variable voltage output power supply, a third switch between the low-voltage winding side of the second transformer and an important circuit bus, and a fourth switch between the output of the variable voltage output power supply and an important circuit bus.

[0094] Furthermore, a power receiving system according to one embodiment includes a first extra-high voltage transformer that converts a voltage output from an extra-high voltage power supply into a predetermined voltage, a first extra-high voltage switch that connects or disconnects the extra-high voltage power supply and the first extra-high voltage transformer, a second extra-high voltage transformer that converts a voltage output from the extra-high voltage power supply into a predetermined voltage, a second extra-high voltage switch that connects or disconnects the extra-high voltage power supply and the second extra-high voltage transformer, a first high voltage switch connected between a low voltage side winding of the first extra-high voltage transformer and a high voltage bus, a second high voltage switch connected between a low voltage side winding of the second extra-high voltage transformer and a high voltage bus, and a second high voltage switch connected between a low voltage side winding of the second extra-high voltage transformer and a high voltage bus. The configuration may also include a third high-voltage switch connected between the low-voltage side winding and the demagnetization circuit bus, a fourth high-voltage switch connected between the low-voltage side winding of the second extra-high-voltage transformer and the demagnetization circuit bus, a demagnetization transformer having its high-voltage side winding connected to the excitation bus and a variable voltage output power supply connected to the low-voltage side winding, and a control device that connects the transformer of the first extra-high-voltage transformer and the second extra-high-voltage transformer that is not connected to the extra-high-voltage power supply to the variable voltage output power supply via the demagnetization transformer, and controls the transformer to increase the voltage from a low voltage to the rated voltage over a predetermined time, and then decrease the voltage to 0 over a predetermined time. [Explanation of symbols]

[0095] 1···Extra-high voltage power supply, 2···Low voltage power supply, 3···Emergency power supply unit, 3a···UPS, 4, 4-1 to 4-3, 6, 6-1, 6-2, 7-1, 7-2, 10, 11, 12, 12A, 13, 14, 15, 16, 17···Switch, 5···First transformer, 18···Low voltage important load, 19···High voltage general load, 20···Low voltage general load, 30···Control device, 40···Protective relay, 50···Second transformer, 50-1···Degaussing transformer, 50-2···Low voltage circuit transformer, 5-1···First extra-high voltage transformer, 5-2···Second extra-high voltage transformer

Claims

1. a first transformer that converts a voltage output from the extra-high voltage power supply into a predetermined voltage; a first switch that connects or disconnects the extra-high voltage power supply and the first transformer; a second transformer that converts the predetermined voltage converted by the first transformer into a lower voltage; a variable voltage output power supply capable of applying a voltage to the first transformer via the second transformer; a control device that controls, when the first switch cuts off the voltage output from the extra-high voltage power supply to the first transformer, the voltage applied to the first transformer by the variable voltage output power supply via the second transformer so as to increase from a low voltage to a rated voltage over a first predetermined time, and then decrease the voltage to a predetermined low voltage over a second predetermined time, and then closes the first switch; A power receiving system comprising:

2. a second switch is provided between a low voltage winding side of the second transformer and an output of the variable voltage output power supply, a third switch is provided between the low voltage winding side of the second transformer and an important circuit bus, and a fourth switch is provided between the output of the variable voltage output power supply and the important circuit bus; The power receiving system according to claim 1 .

3. The variable voltage output power source is a generator. The power receiving system according to claim 2 .

4. The variable voltage output power supply is an uninterruptible power supply. The power receiving system according to claim 2 .

5. The first predetermined time and the second predetermined time are times set to demagnetize the residual magnetic flux of the first transformer. The power receiving system according to claim 1 .

6. a first extra-high voltage transformer that converts a voltage output from the extra-high voltage power supply into a predetermined voltage; a first extra-high voltage switch that connects or disconnects the extra-high voltage power supply and the first extra-high voltage transformer; a second extra-high voltage transformer that steps down the voltage output from the extra-high voltage power supply to a predetermined voltage; a second extra-high voltage switch that connects or disconnects the extra-high voltage power supply and the second extra-high voltage transformer; a first high voltage switch connected between a low voltage side winding of the first extra-high voltage transformer and a high voltage bus; a second high-voltage switch connected between a low-voltage side winding of the second special high-voltage transformer and the high-voltage bus; a third high-voltage switch connected between a low-voltage side winding of the first special high-voltage transformer and a demagnetization circuit bus; a fourth high-voltage switch connected between a low-voltage side winding of the second special high-voltage transformer and the demagnetization circuit bus; a demagnetizing transformer having a high-voltage side winding connected to an excitation bus and a variable voltage output power supply connected to a low-voltage side winding; a control device that connects one of the first extra-high voltage transformer and the second extra-high voltage transformer that is not connected to the extra-high voltage power supply to the variable voltage output power supply via the demagnetizing transformer, and controls the transformer to step up from a low voltage to a rated voltage over a predetermined time period, and then step down to a predetermined low voltage over a predetermined time period; A power receiving system comprising:

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