Switchgear changeover construction method
The proposed switchgear replacement method addresses the issue of multiple power outages and high costs by allowing a single power outage and eliminating the need for mobile equipment, ensuring efficient and cost-effective switchgear replacement.
Patent Information
- Application Number
- JP2023201913
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-29
- Publication Date
- 2025-06-10
AI Technical Summary
Conventional switchgear replacement methods require multiple power outages for tertiary side consumers, leading to significant impact on consumers and increased work costs due to the need for mobile equipment and extensive disconnection/reconnection procedures.
A switchgear replacement method that involves disconnecting the distribution line power cable, replacing the existing switchgear's distribution secondary box with a new one, resuming power to the tertiary side, and then installing the new switchgear without using mobile equipment, thereby minimizing power outages and reducing operational complexity.
This method allows for the replacement of switchgear with only one power outage for tertiary side consumers, reducing the total power outage time and eliminating the need for mobile equipment, thus lowering costs and simplifying the replacement process.
Smart Images
Figure 2025087335000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a switchgear replacement construction method useful for replacing switchgear used as power distribution equipment, and particularly relates to a switchgear replacement construction method useful when power is also supplied to consumers from the tertiary side of a distribution transformer.
Background Art
[0002] Switchgear is a switching device that performs operations such as opening and closing and controlling electric power, and a circuit breaker, transformer, busbar, etc. are housed in a metal cabinet. Such switchgear includes a secondary distribution box connected to the secondary side of a distribution transformer, an in-house GPT box that supplies voltage for power used in the premises and instruments such as various relays, a bus connection box that connects the busbar and the busbar from the secondary panel of other transformers, and a plurality of distribution line boxes that distribute electric power to power demand areas via distribution lines.
[0003] When such switchgear has been used for a predetermined period (e.g., 30 years), there is concern about the possibility of failure due to aging deterioration, etc., so the switchgear (existing box) is replaced in units of banks (transformers) before failure occurs.
[0004] In the switchgear replacement work, it is necessary to disconnect the main circuit of the work target location from the circuit and cut off the power. However, when there are consumers who are supplied with power from the tertiary side (tertiary circuit) of the distribution transformer, it is necessary to consider stable power supply to these tertiary side consumers.
[0005] FIG. 1 is an example of a simple wiring connection diagram of an electrical substation where two banks (the first bank A and the second bank B) are connected to the busbar 10. Primary breakers 101 and 201 are provided on the primary sides of the distribution transformers 100 and 200 of the respective banks A and B, and on the secondary sides of the distribution transformers 100 and 200, there are distribution transformer secondary boxes (also referred to as main transformer secondary boxes or distribution transformer secondary panels) 111 and 211 equipped with secondary breakers 102 and 202, and other boxes (such as in-station GPT boxes, bus connection boxes, distribution line boxes, etc.) connected to the distribution transformers 100 and 200 via these distribution transformer secondary boxes 111 and 211. Switchgears 110 and 210 are provided, and distribution line power cables 112 and 212 for distributing power to the power demand area are connected to the distribution line boxes of these switchgears 110 and 210.
[0006] Also, in this example, power is supplied to a special high-voltage (22 kV) consumer via a special high-voltage power line 221 on the tertiary side (tertiary circuit) of the distribution transformer 200 of the second bank.
[0007] Note that 11 is a bus connection breaker provided on the busbar 10 connecting the first bank A (distribution transformer 100) and the second bank B (distribution transformer 200), and 222 is a tertiary breaker provided on the special high-voltage power line 221.
[0008] In such a configuration, the distribution line connected to the switchgear on the secondary side of the distribution transformer can ensure a stable power supply by performing reverse power transmission even when the distribution transformer and the switchgear are de-energized. However, the consumers supplied with power from the tertiary side (tertiary circuit) of the distribution transformer are special high-voltage consumers such as those at 22 kV, and most of them are dedicated lines. Therefore, during power outage operations associated with switchgear replacement work, it is often difficult to supply power from adjacent transformers or nearby substations. Also, in the work associated with the update of the switchgear, since it requires a certain amount of work time, if the power outage lasts for a long time, it is assumed that it will be difficult to negotiate power outages with special high-voltage consumers.
[0009] Therefore, conventionally, when performing the operation of replacing (updating) the switchgear 210 connected to the secondary side in units of banks, as shown in FIG. 7, while taking temporary power supply countermeasures using the mobile transformer 300, the mobile power cables 301 and 302, the replacement work of the switchgear 210 was carried out while ensuring power transmission to the tertiary circuit.
[0010] Specifically, as shown in FIGS. 8 to 11, first, the distribution transformer and the switchgear are de-energized (step S101, FIG. 9(a)).
[0011] That is, the primary breaker 201, the bus tie breaker 11, and the secondary breaker 202 on the primary side of the distribution transformer 200 are opened to de-energize the distribution transformer 200 and also de-energize the switchgear 210. At this time, in the switchgear 210, the distribution line breaker is opened to prevent the inflow of electricity into the switchgear 210.
[0012] Also, although the tertiary circuit (22 kV consumers) of the distribution transformer 200 will inevitably be de-energized by the operation of step S101, since it is the replacement work of the switchgear 210, in order to prevent the inflow of electricity, the tertiary breaker 222 of the extra-high voltage power line 221 is opened (step S102, FIG. 9(b)).
[0013] Thereafter, in order to connect the mobile equipment, the tertiary circuit of the distribution transformer 200 is disconnected (step S103, FIG. 9(c)).
[0014] In this state, the distribution transformer 200 is bypassed, and the power transmission line and the tertiary circuit (22 kV consumers) of the distribution transformer 200 are connected via the mobile transformer 300, and then a connection test is performed (step S104, FIG. 9(d)). And if there is no problem, power transmission to the 22 kV consumers is resumed via the mobile transformer 300 (step S105, FIG. 10(a)).
[0015] In this way, power transmission to the 22 kV consumers is ensured by the mobile transformer 300. Then, the replacement work of the switchgear 210 is carried out (removing the existing switchgear 210, performing foundation work as necessary, installing the new switchgear (new installation box) 240, laying power cables, and conducting various tests) (Step S106, Fig. 10(b)).
[0016] After replacing the existing switchgear 210 with the new switchgear 240 in this way (after the replacement work of the switchgear is completed), the circuit breakers on the primary side of the mobile transformer 300 (the primary circuit breaker 201 and the bus connection circuit breaker 11) are turned off to de-energize the mobile transformer 300 (Step S107, Fig. 10(c)), and also the tertiary circuit breaker 222 is turned off to de-energize the 22 kV consumers again (Step S108, Fig. 10(d)).
[0017] In this power-off state, the 22 kV consumers are connected to the tertiary circuit of the distribution transformer 200 (Step S109, Fig. 11(a)), and the mobile equipment (mobile transformer) is disconnected (Step S110, Fig. 11(b)). After the phase checking is completed through various tests, power transmission to the tertiary circuit (22 kV consumers) of the distribution transformer 220 is resumed, and power transmission is also carried out to the secondary circuit (6 kV distribution line) of the distribution transformer (Steps S111 - S114, Fig. 11(c)).
[0018] Then, after conducting various tests (artificial ground fault test, actual load test, etc.) while supplying electricity, the construction work is completed (Steps S115, S116).
[0019] As a result, even during the replacement work of the switchgear, power supply to the tertiary side of the distribution transformer is carried out via the mobile transformer 300, so it is possible to minimize the power-off time as much as possible.
Summary of the Invention
Problems to be Solved by the Invention
[0020] However, in the conventional switchgear replacement work, power outages of the tertiary circuit (22 kV consumers) of the distribution transformer are required respectively when connecting and disconnecting the mobile equipment (mobile transformer 30), and a total of two power outages are required. Therefore, the impact on consumers connected to the tertiary circuit becomes significant. In particular, when there are multiple 22 kV consumers, power outages must be carried out according to the convenience of each consumer, making the response even more difficult.
[0021] Also, in the conventional method, since it involves the installation and removal of mobile equipment, there is a disadvantage that the work cost increases. Moreover, since it is necessary to secure a space for installing the mobile equipment, it is not suitable for switchgear replacement work in narrow places.
[0022] Furthermore, in order to use the mobile transformer, disconnection and connection work of the tertiary circuit of the distribution transformer are required, so the work is troublesome and requires a long working time.
[0023] The present invention has been made in view of such circumstances. When replacing the switchgear used as the secondary side equipment of the distribution transformer, when a consumer is connected to the tertiary side of the distribution transformer, the switchgear can be replaced with only one power outage for the tertiary side consumer, and it is possible to supply power to the consumers of the tertiary circuit using the existing distribution transformer without using mobile equipment. The main object is to provide a switchgear replacement construction method.
Means for Solving the Problems
[0024] In order to achieve the above object, the switchgear replacement construction method according to the present invention is A switchgear replacement construction method for replacing the switchgear of a power system that supplies power from the primary power transmission system of a distribution transformer to the secondary power distribution system through the switchgear provided on the secondary side and also supplies power from the tertiary side of the distribution transformer. A power outage state formation step of disconnecting a distribution line power cable connected to the existing switchgear and putting the distribution transformer into a power outage state to cut off the power supply on the tertiary side; In the power outage state of this power outage state formation step, a distribution secondary box replacement step of disconnecting the distribution secondary box of the existing switchgear (disconnecting the existing distribution secondary power cable) and connecting the distribution secondary box of the newly installed switchgear (connecting the newly installed distribution secondary power cable); A tertiary side power supply resumption step of releasing the power outage state of the distribution transformer and resuming power supply to the tertiary side of the distribution transformer; A new installation box installation step of removing the existing box excluding the distribution secondary box of the existing switchgear and installing the new installation box excluding the distribution secondary box of the newly installed switchgear; A power supply available state formation step of connecting the adjacent new installation boxes of the newly installed switchgear to the bus and connecting the distribution line power cable to the newly installed switchgear; It is characterized by comprising the above.
[0025] Therefore, for the tertiary side of the distribution transformer, in the power outage state formation step, the distribution line power cable connected to the existing switchgear is disconnected, and after putting the distribution transformer into a power outage state to cut off the power supply on the tertiary side, in the distribution secondary box replacement step, the existing distribution secondary box is replaced with the newly installed distribution secondary box, and then in the tertiary side power supply resumption step, the power outage state of the distribution transformer is released and the power supply to the tertiary side of the distribution transformer is resumed. After ensuring the power supply to the tertiary side, in the new installation box installation step, the existing box excluding the distribution secondary box of the existing switchgear is removed, the new installation box excluding the distribution secondary box of the newly installed switchgear is installed, and in the power supply available state formation step, the adjacent new installation boxes of the newly installed switchgear are connected to the bus and the distribution line power cable is connected to the newly installed switchgear. Thus, the power outage of the consumers on the tertiary side of the distribution transformer associated with the replacement work of the switchgear is only once, and it is possible to shorten the total power outage time during the replacement work of the switchgear.
[0026] Here, it is desirable that a protective relay be provided in the newly installed secondary distribution box through an instrument transformer connected to the secondary side of the distribution transformer.
[0027] With such a configuration, since a protective relay is provided in the secondary distribution box provided on the secondary side of the distribution transformer, while ensuring the power supply to consumers connected to the tertiary circuit of the distribution transformer, it is possible to simultaneously perform secondary side ground fault protection. Even when a ground fault occurs, it will not affect the consumers connected to the tertiary circuit.
[0028] Also, after connecting the distribution line power cable by the power supply available state forming step, a trial charge of the newly installed switchgear is performed. In this trial charge, it is desirable that the trip circuit be temporarily changed so as to perform protective interruption by the circuit breaker of the newly installed secondary distribution box (the circuit breaker on the secondary side of the distribution transformer).
[0029] With such a configuration, when performing a trial charge of the newly installed switchgear, since the trip circuit is connected to the secondary circuit breaker of the distribution transformer, even if the secondary circuit breaker trips in the event of an accident, it is possible to avoid power outages to tertiary side consumers.
Advantages of the Invention
[0030] As described above, according to the present invention, while disconnecting the distribution line power cable connected to the existing switchgear and putting the distribution transformer into a power outage state to cut off the tertiary side, the secondary distribution box of the existing switchgear is disconnected and a newly installed secondary distribution box is connected. Then, the power outage state of the distribution transformer is released and power transmission to the tertiary side of the distribution transformer is resumed. After ensuring power transmission to the tertiary side, the existing boxes except the secondary distribution box of the existing switchgear are removed, the new boxes except the secondary distribution box of the newly installed switchgear are installed, adjacent new boxes are connected by a bus, and the distribution line power cable is connected. Therefore, when replacing the switchgear, it is possible to have only one power outage for consumers on the tertiary side, and it is possible to shorten the power outage time associated with the switchgear replacement work. In addition, since it becomes possible to replace the switch gear without using the mobile equipment, it is possible to reduce the working costs and working hours associated with the installation and removal of the mobile equipment, and it also becomes easier to replace the switch gear in a narrow place where it is not possible to secure a space for installing the mobile equipment.
Brief Description of the Drawings
[0031]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Embodiments for Carrying Out the Invention
[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0033] FIG. 1 is a simplified wiring connection diagram of a substation for stepping down electricity from a power transmission line (110 kV or 66 kV). In this example, the first bank A and the second bank B are connected to the bus 10. A switchgear 110 is connected to the secondary side of the distribution transformer 100 on the first bank A side, and a switchgear 210 is connected to the secondary side of the distribution transformer 200 of the second bank B. Each of the switchgears 110 and 210 includes a secondary distribution box 111 and 211 having secondary circuit breakers 102 and 202 connected to the secondary sides of the distribution transformers 100 and 200, and other boxes (indoor GPT boxes, bus coupler boxes, distribution line boxes, etc., not shown) connected to the distribution transformers 100 and 200 via the secondary distribution boxes 111 and 211. And in each switchgear's distribution line box, distribution line power cables 112 and 212 for distributing power to the power demand area are connected.
[0034] Note that primary circuit breakers 101 and 201 are provided on the primary sides of the distribution transformers 100 and 200 of each of the banks A and B, respectively. Also, a bus tie breaker 11 is provided on the bus 10 connecting the first bank A (distribution transformer 100) and the second bank B (distribution transformer 200).
[0035] Here, the switchgears 110 and 210 are configured by arranging a plurality of closed metal boxes in a row. In each switchgear 110 and 210, a metal plate (not shown) that constitutes a bus is provided inside the box, and by connecting the respective metal plates, the equipment housed inside each switchgear is connected to the bus.
[0036] The switchgears 110 and 210 are appropriately combined and installed with a distribution secondary box (essential box) 111 and 211 connected to the secondary sides of the distribution transformers 100 and 200, an in-station GPT box (essential box) for supplying power to the power used in the station and instruments such as various relays, a bus box (optional box) for connecting the bus of the distribution secondary box and the bus from the secondary panel of other transformers, a distribution line box (optional box) to which the power cables 112 and 212 can be connected, etc.
[0037] Furthermore, the bus 113 of the switchgear 110 of bank A and the bus 213 of the switchgear 210 of bank B are connected by a bus tie line 20, and a bus tie breaker 21 is provided on this bus tie line 20. This bus tie breaker 21 is turned on in cases such as when one distribution transformer fails and cannot supply power to the distribution line, and power is to be supplied from the other distribution transformer, and is kept off at all times.
[0038] And in this substation, a special high-voltage power line 221 for supplying power to special high-voltage (22 kV) consumers is connected to the tertiary side (tertiary circuit) of the distribution transformer 200 of the second bank B. This special high-voltage power line 221 can be opened and closed by a tertiary circuit breaker 222.
[0039] In such an electrical substation, when attempting to replace the switchgear 210 of the second bank B, to which a special high-voltage consumer (special high-voltage power line 221) is connected on the tertiary side of the distribution transformer 200, on a bank-by-bank basis, it is necessary to fully consider the stable power supply to the consumers connected to the tertiary side. Therefore, in order to replace the existing switchgear 210 connected to the secondary side of the second bank B with new switchgear, the replacement method described below (see FIGS. 2 to 6) is adopted.
[0040] First, install the newly established distribution transformer secondary box 230 near the existing switchgear 210 (step S01, FIG. 3(a)). This newly established distribution transformer secondary box 230 can be electrically connected to the secondary side of the distribution transformer 200 via a distribution transformer secondary power cable (not shown), is equipped with a secondary circuit breaker 231 that can open and close the secondary side of the distribution transformer 200, and can also be connected to the secondary side of the distribution transformer 200 via an instrument transformer 232, and is equipped with a protective relay (64VD) 233 that operates in the event of an abnormality such as a ground fault.
[0041] Thereafter, in order to de-energize the existing distribution transformer secondary box 211, disconnect and remove the existing control cable (not shown), and disconnect and remove the distribution line power cable 212 connected to the distribution line box (actually, after de-energizing by cutting the distribution line circuit breaker and the first switch, disconnect the distribution line power cable 212, and reverse-feed up to the first switch of the distribution line power cable 212) (step S02, FIG. 3(b)). For this reason, in this step, without de-energizing the distribution line by reverse-feed and without de-energizing the distribution transformer 200 either, the distribution line power cable 212 is disconnected and removed from the existing switchgear 210.
[0042] Thereafter, turn off the circuit breaker on the primary side of the distribution transformer 200 (primary circuit breaker 201) and the bus tie circuit breaker 11, and turn off the circuit breaker of the 22 kV special high-voltage power line (tertiary circuit breaker 222) to de-energize the distribution transformer 200 and the tertiary circuit (22 kV consumers) of the distribution transformer 200 (step S3, FIG. 3(c)).
[0043] Thereafter, the distribution transformer secondary power cable 214 of the existing distribution transformer secondary box 211 connected to the secondary side of the distribution transformer 200 is disconnected and removed (step S04, Fig. 3(d)), and the distribution transformer secondary power cable 234 of the newly installed distribution transformer secondary box 230 is connected here and a trial charge is performed (step S05, Fig. 4(a)).
[0044] And, if there is no particular problem, with the tertiary breaker 222 turned on, power is transmitted to the tertiary circuit (22 kV consumers) of the distribution transformer 200 to lift the power outage (step S06, Fig. 4(b)), and in that state, a full load test of the newly installed connected distribution transformer secondary box is performed and phase checking is carried out (step S07, Fig. 4(b)). The power outage time of the tertiary circuit (22 kV consumers) of this distribution transformer 200 is about 8.5 hours.
[0045] Thereafter, the remaining existing boxes of the existing switchgear 210 excluding the distribution transformer secondary box 211 are removed, and switchgear body work is carried out to install the newly installed boxes of the newly installed switchgear 240 excluding the distribution transformer secondary box 230 (step S08, Fig. 4(c)).
[0046] Here, even if the newly installed switchgear 240 has the same configuration as the existing switchgear, when the existing switchgear is composed of an essential box including a distribution transformer secondary box and an accessory box including a distribution line box, a part of the configuration of the accessory box may be changed or a new accessory box may be added. In this example, the existing distribution transformer secondary box, in-station GPT box, and distribution line box are removed, and the newly installed distribution transformer secondary box, in-station GPT box, distribution box, and the newly installed bus connection duct box are installed.
[0047] Thereafter, bus connection of the newly installed distribution transformer secondary box and the newly installed boxes that have been installed is performed (bus connection of the newly installed boxes adjacent to the newly installed switchgear 240), and various tests such as relay acceptance test, PT primary test, CT primary test, and comprehensive operation test are carried out (step S09, Fig. 4(d)).
[0048] After that, connect the power cable 212 to the distribution switchgear box of the newly installed switchgear 240 (step S10, Fig. 5(a)), and conduct a pre-charging test on the newly installed boxes excluding the distribution transformer secondary box 230 (step S11, Fig. 5(b)).
[0049] This pre-charging test is carried out by connecting the protection trip circuit to the secondary breaker 231 of the distribution transformer 200. As a result, even if the pre-charging is unsuccessful, only the secondary breaker 231 of the distribution transformer 200 will trip, and it will not affect the tertiary circuit (22 kV consumers) of the distribution transformer 200.
[0050] After that, conduct various tests and inspections (phase checking of the 6 kV bus (S12, Fig. 5(c)), pre-charging test of the distribution line (S13, Fig. 5(d)), phase checking of the distribution line (S14, Fig. 6(a))). If there are no particular problems, stop the reverse power flow of each distribution line, turn on the distribution line breaker, and resume the supply of electricity from the distribution transformer 200 to each distribution line (step S15, Fig. 6(b)). At the same time, conduct tests such as the artificial ground fault test and the actual load test while continuing the power distribution to the distribution line (steps S16, S17).
[0051] Therefore, by adopting the above switchgear replacement construction method, it is possible to have only one power outage for the 22 kV consumers connected to the tertiary circuit of the distribution transformer 200, and the total power outage time of the tertiary side consumers can also be reduced to about half compared with the conventional method.
[0052] Also, when replacing the switchgear, it is not necessary to connect and disconnect the mobile equipment. Therefore, the working time and labor associated with the connection and disconnection of the mobile equipment can be reduced, and the mobile equipment can be moved to other work locations. In addition, since the mobile equipment is no longer needed, there is no need to secure the installation space for the mobile equipment, and the space within the substation can be effectively utilized. Also, since the connection and disconnection work of the control circuit of the mobile equipment is no longer needed, it is possible to eliminate the human errors associated with this work.
[0053] Furthermore, since the newly installed secondary distribution box is equipped with a protective relay (64VD) 233, by connecting the secondary distribution box 230 to the secondary circuit of the distribution transformer 200 in synchronization with the power outage of the 22 kV consumer, it becomes possible to simultaneously supply power to the 22 kV consumer and provide secondary ground fault protection. Also, even in the case where there is a problem with the secondary circuit breaker 231 of the distribution transformer 200 and long-term repair is required, ground fault protection on the secondary side of the distribution transformer becomes possible.
Explanation of Signs
[0054] 100, 200 Distribution transformers 110, 210, 240 Switchgears 112, 212 Distribution line power cables 211, 230 Secondary distribution boxes 232 Instrument transformers 233 Protective relays
Claims
1. A switchgear replacement construction method for a power system that supplies power from the primary power transmission system of a distribution transformer to the secondary power distribution system via a switchgear provided on the secondary side and also supplies power from the tertiary side of the distribution transformer, comprising: A power outage state formation step of disconnecting the distribution line power cable connected to the existing switchgear and putting the distribution transformer into a power outage state to cut off the tertiary side; A secondary distribution box replacement step of disconnecting the secondary distribution box of the existing switchgear and connecting the secondary distribution box of the new switchgear in the power outage state of this power outage state formation step; A tertiary side power transmission restart step of releasing the power outage state of the distribution transformer and restarting power transmission to the tertiary side of the distribution transformer; A new box installation step of removing the existing box excluding the secondary distribution box of the existing switchgear and installing the new box excluding the secondary distribution box of the new switchgear; A power supply possible state formation step of connecting the new boxes adjacent to the new switchgear to the bus and connecting the distribution line power cable to the new switchgear; A switchgear replacement construction method characterized by comprising the above steps.
2. The switchgear replacement construction method according to Claim 1, wherein a protective relay is provided in the new secondary distribution box of the distribution transformer via an instrument transformer connected to the secondary side of the distribution transformer.
3. After connecting the distribution line power cable in the power supply possible state formation step, a trial charge of the new switchgear is performed. In this trial charge, the trip circuit is temporarily changed so as to be protected and interrupted by the circuit breaker of the new secondary distribution box of the distribution transformer. The switchgear replacement construction method according to Claim 1 or 2, characterized by this.