CN113162005A - Medium voltage distribution network system - Google Patents

Abstract

The application discloses a medium voltage distribution network system. Wherein, this system includes: the medium-voltage backbone network comprises at least one transformer substation and at least one switching station, and adopts any one of a double-petal wiring mode and a double-loop wiring mode by taking the switching station as a center; the medium-voltage branch network comprises at least one distribution room and at least one switching station, the distribution room is used as a load node, and any one of a direct distribution type double-radio network connection mode, a double-loop network connection mode and a cascading type double-radio network connection mode is adopted; and the control equipment is used for matching the number of the switch stations in the outgoing line of the transformer substation according to the capacity of the distribution room in the geographic range. The method and the device solve the technical problems that in the prior art, the medium-voltage distribution network grid structure is mainly determined based on user loads and user importance levels, when new loads in the area need to be accessed into a power grid, the access scheme is usually considered according to the number of the residual intervals between nearby switch stations and a transformer substation, and multiple networks cannot be formed to improve power supply reliability.

Description

Medium voltage distribution network system

Technical Field

The application relates to the field of power distribution networks, in particular to a medium-voltage power distribution network system.

Background

Along with the rapid development of economy and the continuous improvement of the living standard of people, the urban power utilization load continuously rises, and users have higher requirements on power supply reliability. Medium voltage distribution networks are important components of urban power networks and are links connecting the power networks with users.

The existing medium-voltage distribution network frame structure is mainly determined based on user load and user importance level, and the main wiring forms include single-shot type, double-shot type, opposite-shot type, single-ring network, double-ring network, triple-double type and N supply 1 device. Although the risk of the N-2 condition of the power grid is resisted in high-reliability areas by adopting a double-loop network closed-loop and double-petal operation mode, the medium-voltage distribution network in most domestic areas is still in radial wiring. The wiring mode is selected more reasonably, and the reduction of power distribution network transformation projects has important significance on power grid construction and economy.

In the past, the wiring mode of a medium-voltage distribution network is mainly determined by the load increase demand of users in the area, a uniform grid structure does not exist in the whole village, town or city, and systematic planning is lacked in construction. When new load increases in the area and needs to be accessed to a power grid, an access scheme is usually considered according to the number of the remaining intervals between the nearby switch station and the transformer substation, and multiple networks cannot be formed to improve the power supply reliability.

In view of the above problems, no effective solution has been proposed.

Disclosure of Invention

The embodiment of the application provides a medium-voltage distribution network system, which is used for at least solving the technical problem that in the prior art, a medium-voltage distribution network grid structure is determined mainly based on user load and user importance level, when new load growth needs to be accessed into a power grid in a region, an access scheme is usually considered according to the number of remaining intervals between a nearby switch station and a transformer substation, and multiple networks cannot be formed to improve power supply reliability.

According to an aspect of an embodiment of the present application, there is provided a medium voltage distribution grid system including: the medium-voltage backbone network comprises at least one transformer substation and at least one switching station, and leads out wires from the low-voltage side of the transformer substation to the switching station by taking the switching station as a center and adopting any one of a double-petal wiring mode and a double-loop network wiring mode; the medium-voltage branch network comprises at least one distribution room and at least one switching station, the distribution room is used as a load node, any one of a direct distribution type bijection wire, a double-loop network wire and a cascading type bijection wire is adopted for wiring, and a lead-out wire is led out from the low-voltage side of the switching station to the distribution room; and the control equipment is used for matching the number of the switch stations in the outgoing line of the transformer substation according to the capacity of the distribution room in the geographic range.

Optionally, when the medium-voltage backbone network adopts a dual-ring network connection mode, different sections of buses of different substations respectively supply power to ring networks formed by the medium-voltage backbone network, and the switching stations in the medium-voltage backbone network all have multiple power supply incoming lines.

Alternatively, in case of a failure of a main line in the medium voltage backbone, the switches of the switchyard connected to the main line are controlled to open and the other switchyards are controlled to close so that the non-failed section in the medium voltage backbone resumes the supply.

Optionally, in the case that a feeder line of any one of the switching stations in the medium-voltage backbone network fails, any one of the switches of the switching station with the failed feeder line is controlled to open, so that other loads in the medium-voltage backbone network are continuously powered.

Optionally, in the case of a fault of a bus of any one switching station in the medium-voltage backbone network, all switches of the switching station with the fault of the bus are controlled to be switched off, and other switching stations are controlled to be switched on, so that a non-fault section in the medium-voltage backbone network is restored to supply power.

Optionally, when the medium-voltage backbone network adopts a dual-petal wiring mode, the same section of buses of at least two different substations respectively supply power to a ring network formed by the medium-voltage backbone network, and the ring network operates in a closed loop manner, wherein switch stations in the medium-voltage backbone network all have multiple power supply incoming lines.

Alternatively, in case of a failure of the main line of the medium voltage backbone, the switching of the switchyard connected to the main line is controlled to open, so that any one switchyard in the medium voltage backbone is powered by the bidirectional power supply of both substations.

Optionally, in the case that a feeder line of any one of the switchyards in the medium-voltage branch network fails, any one of the switches of the switchyard with the faulty feeder line is controlled to be switched off, so that any one of the switchyards in the medium-voltage backbone network is powered by the bidirectional power supply from the two substations.

Optionally, in the case of a fault in the bus of any one of the switchyards in the medium voltage branch network, all switches of the switchyard with the fault in the bus are controlled to open and the other switchyards are controlled to close, so that any one switchyard in the medium voltage backbone network is powered by bidirectional power from two substations.

Optionally, when the medium-voltage branch network adopts a direct-distribution type dual-radio connection mode, two sections of different medium-voltage buses of any one switching station in the medium-voltage branch network are respectively led out a loop line, the medium-voltage buses are operated in an open loop mode, and power supplies of a power distribution room in the medium-voltage branch network are from different bus sections of the same switching station.

Optionally, when a line from any one switching station to the distribution room in the medium-voltage branch network has a fault, the feeder current protection switch of the higher-level switching station is turned on, and after the delay time is reached, the segmented spare power automatic switching non-voltage switching-off function of the distribution room is started, and the segmented switch is closed, so that power supply is recovered.

Optionally, when a distribution room bus in the medium-voltage branch network has a fault, a switch for protecting the overcurrent of a distribution room line is opened, and a high-voltage backup automatic switch of the distribution room is locked, after the non-voltage delay, a segmented backup automatic switch non-voltage switching-off function is started, and the segmented switch is switched on, so that the power supply is recovered.

Optionally, when a transformer of a distribution room in the medium-voltage branch network fails, a switch of a transformer protector of the distribution room is controlled to be turned on, after non-voltage delay, a function of non-voltage switching off of the segmented automatic bus transfer is started, and the segmented switch is controlled to be switched on, so that power supply is recovered.

Optionally, when the medium-voltage branch network adopts a dual-loop network connection mode, two sections of different medium-voltage buses of any one switching station in the medium-voltage branch network are respectively led out to form a return line, the return line is operated in an open loop mode, and power supplies of a power distribution room in the medium-voltage branch network are from different bus sections of the same switching station.

Optionally, in the case of a fault in any section of line in the medium-voltage branch network, the feeder current protection switch of the switching station on the faulty line is turned on, and please start the no-voltage function of the distribution room on the faulty line.

Optionally, in a case that the medium-voltage branch network adopts a dual-radio mode, two sections of different medium-voltage buses of any one switching station in the medium-voltage branch network are respectively led out to form a return line, the return line is operated in an open loop mode, and power supplies of a power distribution room in the medium-voltage branch network are from different bus sections of the same switching station.

Optionally, in the case of a fault in the trunk line of any one of the distribution rooms in the medium voltage branch network, the switchyard feeder current protection switch on the trunk line of any one of the distribution rooms is controlled to trip, and the no-voltage-drop function of the distribution room is started, and the incoming line switches of other distribution rooms in the medium voltage branch network are all disconnected.

Optionally, in the case of a fault of a bus of any one of the distribution rooms in the medium-voltage branch network, the line overcurrent protection switch of any one of the distribution rooms is controlled to be opened, and the high-voltage backup power automatic switching device of the distribution room is locked.

Optionally, in the case of a fault in a transformer of any one of the distribution rooms in the medium voltage branch network, the transformer protection switch controlling the distribution room is tripped, and the switches on both sides of the transformer are opened.

In an embodiment of the present application, there is provided a medium voltage distribution grid system, comprising: the medium-voltage backbone network comprises at least one transformer substation and at least one switching station, and leads out wires from the low-voltage side of the transformer substation to the switching station by taking the switching station as a center and adopting any one of a double-petal wiring mode and a double-loop network wiring mode; the medium-voltage branch network comprises at least one distribution room and at least one switching station, the distribution room is used as a load node, any one of a direct distribution type bijection wire, a double-loop network wire and a cascading type bijection wire is adopted for wiring, and a lead-out wire is led out from the low-voltage side of the switching station to the distribution room; and the control equipment is used for matching to obtain the number of the switch stations in the outgoing line of the transformer substation according to the capacity of the distribution room in the geographic range, and hierarchically planning the grid structure of the medium-voltage distribution network by dividing the medium-voltage distribution network into a medium-voltage main network and a medium-voltage branch network. The medium-pressure backbone network part adopts a wiring type of double petals and a double ring network, so that the reliability of the net rack is ensured; the direct distribution type bijective, double-loop network and cascade connection type bijective network wiring mode can be selected in the medium-voltage branch network part according to the reliability and load requirements of the area, the difference of users is met, the technical effects of advanced systematic planning and prior decision making in the medium-voltage distribution network construction are achieved, the later medium-voltage distribution network transformation requirements are reduced, the technical problem that in the prior art, the medium-voltage distribution network structure is mainly determined based on the user load and the user importance level, when new loads in the area need to be accessed into the power network when the area is increased, the access scheme is generally considered according to the number of the residual intervals between a nearby switch station and a transformer substation, and the technical problem that multiple networks can not be formed to improve the power supply reliability is solved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a schematic diagram of the structure of a medium voltage power distribution grid system according to an embodiment of the present application;

FIG. 2a is a schematic diagram of a dual ring network trunk line fault according to an embodiment of the present application;

fig. 2b is a schematic diagram of a dual looped-network feeder fault according to an embodiment of the present application;

FIG. 2c is a schematic diagram of a double looped network bus fault according to an embodiment of the present application;

FIG. 2d is a schematic diagram of a double looped network two consecutive faults in accordance with an embodiment of the present application;

FIG. 3a is a schematic illustration of a double petal trunk line fault according to an embodiment of the present application;

FIG. 3b is a schematic diagram of a double petal feeder line fault according to an embodiment of the present application;

FIG. 3c is a schematic illustration of a double petal busbar fault according to an embodiment of the present application;

FIG. 3d is a schematic illustration of a two petal two consecutive failure in accordance with an embodiment of the present application;

fig. 4a is a schematic diagram of a medium voltage branch network direct distribution type dual-radio line according to an embodiment of the present application;

FIG. 4b is a schematic diagram of a bus bar fault in a direct-wiring twin-wire electrical distribution room according to an embodiment of the present application;

FIG. 4c is a schematic diagram of a direct-coupled twinned switchhouse transformer fault according to an embodiment of the present application;

fig. 5 is a schematic diagram of a dual ring network wiring for a medium voltage branch network, for example, four distribution rooms, according to an embodiment of the present disclosure;

fig. 6a is a schematic diagram of a cascaded two-wire connection of a medium voltage branch network, for example, four distribution rooms, according to an embodiment of the present disclosure;

FIG. 6b is a schematic view of a cascaded two-wire electrical distribution room bus bar fault according to an embodiment of the present application;

fig. 6c is a schematic diagram of a fault in a cascaded two-wire substation transformer according to an embodiment of the present application.

Detailed Description

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Fig. 1 is a schematic diagram of a medium voltage distribution grid system according to an embodiment of the present application, as shown in fig. 1, the system comprising:

the medium-voltage backbone network 10 comprises at least one transformer substation and at least one switching station, and leads out wires from the low-voltage side of the transformer substation to the switching station by taking the switching station as a center and adopting any one of a double-petal wiring mode and a double-loop wiring mode;

the medium-voltage branch network 12 comprises at least one distribution room and at least one switching station, takes the distribution room as a load node, adopts any one of a direct distribution type bijection wire, a double-loop network wire and a cascading type bijection wire mode, and leads out wires from the low-voltage side of the switching station to the distribution room;

and the control equipment 14 is used for matching the number of the switchgears in the outgoing line string of the transformer substation according to the capacity of the distribution room in the geographic range.

By the system, the medium-voltage distribution network is divided into a medium-voltage backbone network and a medium-voltage branch network, and the grid structure of the medium-voltage distribution network is planned in a layered mode. The medium-pressure backbone network part adopts a wiring type of double petals and a double ring network, so that the reliability of the net rack is ensured; the direct distribution type bijective, double-loop network and cascade connection type bijective network wiring modes can be selected in the medium-voltage branch network part according to the reliability and load requirements of the region, the difference of users is met, and therefore the technical effects of advanced systematic planning, prior decision making and reduction of the later medium-voltage power grid transformation requirements in the medium-voltage power distribution network construction are achieved.

According to an optional embodiment of the present application, in the case that the medium voltage backbone network adopts a dual-ring network connection mode, different segments of buses of different substations respectively supply power to ring networks formed by the medium voltage backbone network, and the switching stations in the medium voltage backbone network all have multiple power supply incoming lines.

According to another alternative embodiment of the present application, in case of a failure of a main line in the medium voltage backbone, the switch of the switching station connected to the main line is controlled to open and the other switching stations are controlled to close the switches, so that the non-failed section in the medium voltage backbone is restored to supply power.

In an alternative embodiment of the present application, in the event of a failure of a feeder line of any one of the switching stations in the medium voltage backbone, any one of the switches of the switching station with the failed feeder line is controlled to open, so that other loads in the medium voltage backbone are continuously powered.

According to an alternative embodiment of the present application, in the event of a fault of a bus of any one switching station in the medium voltage backbone, all switches of the switching station with the faulty bus are controlled to open and other switching stations are controlled to close, so that the non-faulty section in the medium voltage backbone is restored to supply power.

According to an optional embodiment of the present application, in a case that the medium voltage backbone network adopts a dual-petal wiring mode, the same section of bus of at least two different substations respectively supplies power to a ring network formed by the medium voltage backbone network, and the ring network operates in a closed loop manner, wherein switch stations in the medium voltage backbone network all have multiple power supply incoming lines.

According to an alternative embodiment of the application, in case of a failure of the main line of the medium voltage backbone, the switching of the switchyard connected to the main line is controlled to be opened so that any one switchyard in the medium voltage backbone is powered by both directions of the two substations.

According to another alternative embodiment of the present application, in case of a failure of a feeder line of any one of the switchyards in the medium voltage branch network, any one of the switches of the switchyard with the failed feeder line is controlled to be opened, so that any one of the switchyards in the medium voltage backbone network is powered by bidirectional power from two substations.

In some optional embodiments of the present application, in case of a fault of a bus of any one switching station in the medium voltage branch network, all switches of the switching station with the faulty bus are controlled to open and other switching stations are controlled to close so that any one switching station in the medium voltage backbone network is powered by bidirectional power from two substations.

According to an alternative embodiment of the present application, in the case that the medium voltage branch network adopts the direct-distribution type dual-radio mode, two sections of different medium voltage buses of any one switching station in the medium voltage branch network respectively lead out a return line, the medium voltage buses are operated in an open loop mode, and the power supply of the distribution room in the medium voltage branch network is from different bus sections of the same switching station.

According to an optional embodiment of the application, under the condition that a line from any one switching station to a distribution room in a medium-voltage branch network has a fault, a feeder current protection switch of a superior switching station is opened, after a delay time is reached, a segmented spare power automatic switching non-voltage switching-off function of the distribution room is started, and a segmented switch is closed, so that power supply is recovered.

According to an optional embodiment of the application, under the condition that a distribution room bus in a medium-voltage branch network has a fault, a switch for protecting a distribution room line from overcurrent is opened, and a high-voltage backup automatic switching device of the distribution room is locked, after the non-voltage delay, a segmented backup automatic switching device non-voltage switching-off function is started, and a segmented switch is switched on, so that power supply is recovered.

According to an optional embodiment of the application, under the condition that a distribution room transformer in a medium-voltage branch network breaks down, a switch of a transformer protector of the distribution room is controlled to be opened, after non-voltage delay, a segmented spare power automatic switching non-voltage switching-off function is started, and the segmented switch is controlled to be switched on, so that power supply is recovered.

According to an alternative embodiment of the present application, in the case that the medium voltage branch network adopts a dual ring network connection mode, two sections of different medium voltage buses of any one switching station in the medium voltage branch network respectively lead out a return line, and the medium voltage branch network operates in an open loop, and the power supply of the distribution room in the medium voltage branch network is from different bus sections of the same switching station.

According to an alternative embodiment of the present application, in the event of a fault in any section of line in the medium voltage branch network, the feeder current protection switch of the switching station on the faulty line is opened, please activate the no-voltage-drop function of the distribution room on the faulty line.

According to an alternative embodiment of the present application, in the case that the medium voltage branch network adopts the dual-wire mode, two sections of different medium voltage buses of any one switching station in the medium voltage branch network respectively lead out a return line, and the medium voltage branch network operates in an open loop, and the power supply of the distribution room in the medium voltage branch network is from different bus sections of the same switching station.

According to an optional embodiment of the application, in the case of a fault of a main line of any distribution room in the medium-voltage branch network, the switching station feeder current protection switch on the main line of any distribution room is controlled to be tripped, the no-voltage-drop function of the distribution room is started, and the incoming line switches of other distribution rooms in the medium-voltage branch network are all disconnected.

According to an optional embodiment of the application, in the event of a fault of a bus of any one of the distribution rooms in the medium-voltage branch network, the line overcurrent protection switch of any one of the distribution rooms is controlled to be opened, and the high-voltage spare power automatic switching of the distribution room is locked.

According to an alternative embodiment of the present application, in case of a fault in the transformer of any one of the distribution rooms in the medium voltage branch network, the transformer protection switch controlling that distribution room trips and the switches on both sides of the transformer are opened.

The invention provides a high-reliability medium-voltage distribution network wiring mode which comprises the following steps: in a medium-voltage distribution network, a switching station is taken as a core, and a medium-voltage backbone network is constructed from a lead-out wire at the low-voltage side of a transformer substation to the switching station; and a medium-voltage branch network is constructed from the low-voltage side outlet of the switching station to the distribution room by taking the distribution room as a load node.

The wiring mode of the medium-voltage backbone network is a double-ring network wiring mode or a double-petal wiring mode. As shown in fig. 2a and 2b, the serial switching station is considered as 4 seats temporarily. Open boxes indicate that the circuit breaker is in a normally open state and solid boxes indicate that the circuit breaker is in a normally closed state.

The connection mode of the medium-voltage branch network comprises a direct distribution type double-radio connection wire, a double-loop network connection wire and a cascade type double-radio connection wire. The medium-voltage branch network wiring mode in the power supply area with high requirement on reliability selects a double-ring network wiring and a direct-distribution type dual-injection wiring, and the medium-voltage branch network wiring mode in the power supply area with low requirement on reliability is a cascade type dual-access wiring with different cascade numbers.

Firstly, the double-ring net and double-petal wiring mode is proved to have high reliability.

Double-ring network wiring:

different section buses of two different transformer substations respectively supply power to each looped network, and each switch station in each looped network is provided with 4 power supply incoming lines. The operation mode of the power grid under different fault conditions is specifically explained by taking an example that 4 switching stations are connected in series between two transformer substations, so as to demonstrate that the double-loop network wiring has high reliability.

1) The failure occurred in the main trunk (dual ring network main trunk failure):

after the fault occurs at the position shown in fig. 2a, the switch of the switch station a S2 is opened, the switch of the switch station B S1 is opened, the switch station C2 is closed, the recovery of power supply in the non-fault section is completed, and the fault processing is completed. The four switch stations are not affected by faults and continuously supply power.

2) The fault occurs on the feed-out line (double-loop network feed-out line fault):

after the position shown in fig. 2B is failed, the switch of the B-switch station K1 is opened, and the failure processing is completed. Except the feeder line of the K1, other loads are not affected by faults and are continuously supplied with power.

3) Faults occurred on the bus (double ring network bus fault):

after the position shown in fig. 2C is failed, the switches of the switch station a S1 and S2 are opened, the switches of the switches K1 to K6 are opened, the local backup power automatic switching device is locked, the switch station C S2 is closed (when no load is exceeded), the non-failure section is restored to supply power, and the failure processing is completed. Except for a section of bus of the switch station A, other loads are not affected by faults and power is supplied continuously.

4) Two faults occurred in succession (two consecutive faults of the double loop network):

after the position lines AS 2-BS 1 have faults AS shown in FIG. 2d, the switch of the switch station A S2 is switched off, and the switch of the switch station B S1 is switched off; when the C switch station S2 is closed (no overload), the non-fault section is restored to power supply. The four switch stations are not affected by faults and continuously supply power.

When the first fault is not relieved, a second fault occurs again, position lines CS 1-DS 2 generate faults as shown in figures 2a-2D, a switch of the C switch station S1 is switched off, and a switch of the D switch station S2 is switched off.

When the fault isolation of the C-switch station and the D-switch station is successful, the I-section bus switch of the B, C switch station causes a power loss state. The system is started and the local spare power automatic switching is carried out, switches S1 and S2 of a switching station B, C are tripped, and a switch S5 of a switching station B, C is closed; the non-failed region is restored. The four switch stations are not affected by faults and continuously supply power.

Double petal wiring:

the same section of bus of two different transformer substations supplies power to each petal respectively, and the closed loop operation realizes that each switch station in each petal has 4 power inlet wires. The operation condition of a double-petal power grid with different fault points is specifically explained by taking an example that 4 switching stations are connected in series between two transformer substations, so as to demonstrate that the double-petal wiring has high reliability.

1) Main line of failure occurrence (double petal main line failure)

After the position shown in fig. 3a is failed, the switch of the switch station a S2 is opened, the switch of the switch station B S1 is opened, and the failure processing is completed. There is still a bidirectional power supply from both substations per switchyard.

2) Feeding-out line of fault occurrence (double petal feeding-out line fault)

When the position shown in fig. 3B is failed, the switch of the B switch station K1 is opened, and the failure processing is completed. Each switchyard still has a bidirectional power supply from two substations, 4 return lines.

3) Bus of fault occurrence (double petal bus fault)

And after the position shown in fig. 3c has a fault, the switches of the switch station B S1 and S2 are switched off, the switches K1-K6 are switched off, the spare power automatic switching device is locked in place, and the fault processing is finished. In addition, three switchyards still have bidirectional power supplies from two substations, 4 return lines.

4) Two faults occur continuously (double petal two continuous fault)

And when the bus of the switch station B at the position shown in the figure 3d has a fault, the switches S1 and S2 of the switch station B are switched off, and the switches K1-K6 are switched off, so that the spare power automatic switching device is locked in place. In addition, three substations still have bidirectional power supplies from two substations, 4 return lines.

When the first fault is not resolved, a second fault occurs, and the switching station bus is in fault at the position D shown in the figure and is on the same closed loop circuit as the first fault B switching station. And D, the switches of the switch stations S1 and S2 are switched off, and the switches K1-K6 are switched off, so that the spare power automatic switching device is locked in place.

When the fault isolation of the B switch station and the D switch station is successful, the C switch stations S1, S2 and K1-K6 cause a power-off state. When the C switch station detects that the bus is in voltage loss, the system is started to carry out local backup power automatic switching, the C switch stations S1 and S2 trip, and the C switch station S5 closes the interconnection switch; the non-failed region is restored.

Therefore, under the condition that buses of two switching stations have faults, the power supply of the other two switching stations is not influenced.

In conclusion, the double-petal and double-ring network wiring mode meets the N-1 operation mode, and the non-fault area can still continue to operate under the conditions that any two sections of lines of the backbone network have faults and buses at any two ends of the switching station have faults, so that the risk of N-2 faults of the system can be resisted, and the high-reliability double-petal and double-ring network wiring mode is realized.

Then, the reliability of the double-loop network, the direct-coupled bijective and the cascade bijective connection is compared.

Direct-distribution type double-injection wire of medium-voltage branch network:

fig. 4a is a schematic diagram of a direct-distribution type dual-transmission line of a medium-voltage sub-grid. 1 loop circuit is respectively led out from two sections of different medium voltage buses of a switching station to form a double-loop type wiring form, and the double-loop type wiring form operates in an open loop mode. The cubicle power supplies come from different bus sections of the same switchyard.

1) Line fault

When a line from a switching station to a distribution room has an N-1 fault, as shown in fig. 4a, a feeder current protection action of a superior switching station trips a KA1 switch, after non-voltage delay, a distribution room sectional backup power automatic switching non-voltage switching-off function starts the PA1 switch to be tripped, fault processing is completed, and a switching-on/switching-off switch G2 recovers power supply.

2) Bus fault of distribution room

As shown in fig. 4b, when a bus of the distribution room has a fault, the overcurrent protection action switch PA1 of the line of the distribution room locks the high-voltage backup automatic switch of the distribution room, the fault processing is completed, after no delay, the 380V side section backup automatic switch non-voltage tripping function starts to trip the PA12, and the section switch G2 is switched on to restore power supply.

3) Distribution room transformer fault

As shown in fig. 4c, when the distribution room transformer fails, the protection action of the distribution room transformer trips switches PA11 and PA12, the fault processing is completed, after no-voltage delay, the 380V side section backup power automatic switching no-voltage switching-off function is started, and the section switch G2 is switched on to recover power supply.

Medium voltage branch network double-loop network wiring:

fig. 5 is a schematic diagram of a double loop network wiring diagram of a medium voltage branch network, for example, four distribution rooms. The double-loop network wiring mode of the medium-voltage branch network is similar to that of the medium-voltage main network, 1 loop circuit is respectively led out from two sections of different medium-voltage buses of two switching stations to form a double-loop type wiring mode, and the double-loop type wiring mode operates in an open loop mode. Each distribution room has 4 incoming lines, and the power supply of each distribution room comes from different bus sections of the same switching station.

When any section of line has a fault, as shown in fig. 5, the feeder current protection action of the switch station a trips the switch KA1 on the side, and the line between the switch station a and the interconnection switch PB1 loses power. The power distribution room is not pressed to be turned off, the function is started, and the PA21 and PA1 switches on two sides of the A-1# power distribution room and the A-2# power distribution room are all turned off. After the faults are found out, the switches PA21 and PA1 on the two sides of the A-2# distribution room are switched on, the switches KA1 and A-1# distribution room PA1 are switched on, and the interconnection switch PB1 is switched on. And the four distribution rooms recover the dual power supply.

Similar to a direct distribution type dual-radio line, in the fault processing stage, a high-voltage side section switch of the distribution room is switched on automatically, and all loads of the distribution room are carried by an incoming line where a switch of the distribution room PA2 is located. And after the fault is found out, the section switch of the power distribution room is disconnected to restore the power supply.

When a bus or a transformer of a distribution room has a fault, the operation logic of the switch in the distribution room is similar to that of a direct-distribution type bijection wire. The switchyard-cubicle line operation logic is to close tie switch PB1, the non-faulted line is continuously powered.

The medium-voltage branch network cascade type bijection wire form:

fig. 6a is a schematic diagram of a cascaded two-wire connection of a medium voltage branch network, for example, 4 cubicles. 1 circuit lines are respectively led out from two sections of different medium-voltage buses of a switching station to form a double-wire type line. The upper power supply directions of the four power distribution rooms all come from the same switching station, and no standby power supply of other switching stations exists.

1) Distribution room trunk line fault

When any section of line has a fault, the feeder current protection action of the switch A station trips the switch KA1 at the side, and the carried line loses power on the whole line. The power distribution room is not pressurized, the function is started, and the four power distribution room inlet switches are all disconnected. After a fault is found out, switches of a switching station KA1 and an A power distribution room PA1 are switched on, only the A power distribution room recovers dual power supply, and other three power distribution rooms need to be automatically switched on and switched on through section switches in the power distribution rooms. The power supply reliability of each power distribution room is greatly influenced by the circuit where the power distribution room is located, and the power supply reliability is not high.

2) Bus fault of distribution room

As shown in fig. 6b, when the distribution room bus fails, the distribution room line overcurrent protection action trip switches PA1 and PA11 lock the distribution room high-voltage backup power automatic switch, and the fault processing is completed. And the low-voltage interconnection switch of the power distribution room supplies power to the power distribution room A.

Since the PA1 switch is open and the load of cubicle B, C, D on the line is totally discharged, cubicle B, C, D also needs to supply itself with power through its low-voltage tie switch.

3) Distribution room transformer fault

As shown in fig. 6c, when the distribution room transformer fails, the distribution room transformer protection operation trips switches (not shown) on both sides of the transformer, and the failure processing is completed. And the low-voltage interconnection switch of the power distribution room supplies power to the power distribution room A. The distribution room B, C, D is not affected by the fault and is continuously powered.

In summary, in the case that a line between a switching station and a distribution room bus have a fault, the distribution room only has unidirectional power supply after the fault point, and the power supply reliability is not high. And the direct-distribution type bijection wire and the double-ring wire only affect the power supply of the load at the fault point without affecting other loads under the condition of the faults in the line between the switching station and the distribution room and the interior of the distribution room, and the power supply reliability is high. Therefore, double-ring network connection and direct distribution type dual-radio connection are selected in a medium-voltage branch network connection mode in a power supply area with high requirement on reliability, and the medium-voltage branch network connection mode in the power supply area with low requirement on reliability is cascade type dual-access connection with different cascade numbers.

Meanwhile, on the basis of planning the network frame, the number of the switch stations which are connected in series and correspond to the outgoing lines of the transformer substation can be quickly matched according to the capacity of the distribution room in a specific area. Planning in advance and making a decision preferentially in the construction of the medium-voltage power distribution network are achieved, and the requirements for medium-voltage power distribution network transformation in the later period are reduced.

In another optional embodiment of the present application, a calculation method is further provided, in which the load carrying capacity of the power line of the medium-voltage distribution network is used as a boundary condition, and the load connected to the switching station is used as a variable, so that the number of the switching stations in the 10kV outgoing line string of the transformer substation can be quickly and accurately calculated, and a suggestion is provided for planning and constructing the switching stations and the distribution room.

For the medium-voltage backbone network double-loop network connection, when one single-loop network power inlet line generates N-1, the non-fault side power supply circuit of the loop network is provided with a half load of a switch serially connected with the double-loop network; when the single-ring power supply inlet wire has N-2 or one side of the substation bus fails, the non-failed 2 lines carry all the switch station loads.

For the double-petal wiring of the medium-voltage backbone network, when the petal power supply incoming line is N-1, the petal non-fault side power supply line has a load of half of each switch station serial by double petals; when N-2 or 10kV bus fault of a transformer substation occurs on the power inlet wire at one side of the double petals, the petal load is transferred from the non-fault side petals, and the non-fault petal double-circuit power inlet wire bears the whole load of the switch station in which the double petals are connected.

And under the condition of neglecting the uneven loading capacity, the number of the double-ring network wiring string belt switch stations meets the following formula:

the converted capacity is:

wherein the content of the first and second substances,

for a power supply area with high requirement on reliability, the corresponding capacity of distribution rooms with different numbers of distribution rooms connected in series under the wiring form of a double-loop network and the corresponding capacity of distribution rooms under the wiring form of a direct-distribution double-access mode need to be calculated firstly. For each double-ring network led out from a transformer substation to an opening and closing station, the number of switchgears connected to the switching station and the switchgears connected to the switchgears in the double-ring network needs to be the same.

Switching station access distribution variable capacity is equal to capacity of double-ring network type wiring distribution room multiplied by outgoing line number/2 + direct distribution type double-access wiring distribution room capacity multiplied by outgoing line number/2 + capacity of switching station distribution transformer

For a power supply area with lower requirement on reliability, the corresponding capacity of different numbers of distribution rooms in series connection under the condition that the wiring form of the distribution rooms is a cascading bijection wiring mode needs to be calculated. For each double-ring network led out from a transformer substation to an opening and closing station, the number of switchyard-switchyard connected with switchyard-switchyard in the form of cascade bijective connection is considered according to the equal proportion of 1, 2, 3 and 4. And calculating the average capacity when the maximum number of the accessed distribution rooms is n.

And the switching station access distribution transformer capacity is equal to the average distribution room capacity of the cascaded bijection connecting wire multiplied by the number of outgoing wires/2 + the distribution transformer capacity of the switching station.

The invention has the advantages that in a new area, under the condition of stipulating the quantity ratio of the respective capacities of each public power distribution room and each user power distribution room, the total distribution variable capacity in the double-ring network and the cascade dual-beam network with different serial quantities can be rapidly calculated, and further, the capacity of the accessed switching station can be rapidly calculated and the number of the switching stations connected in series with the backbone network is suggested.

The following is a detailed description of examples of the application of the present invention. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.

Taking a new planning area as an example, assuming that the distribution capacity of the public power distribution room in the area is 1000kVA, 2 or 4 distribution transformers are configured for each power distribution room. The capacity of the user power distribution room is 1.5 times that of the public power distribution room, and the user power distribution room and the public power distribution room are considered in equal proportion. And considering that the switch station has 12 feedback wires, one of which is a distributed power supply access system. And the distribution capacity of the switchyard is taken into account to be 2 multiplied by 1000 kVA.

In the medium-voltage branch network, for the double-loop network wiring of 4 power distribution rooms connected in series, the connection capacity of each switch station is about 21250-40500 kVA; for the direct-matching type dual-radio line, the capacity of each switch station is 15750-29500 kVA; for the cascade type dual-radio line of 4 power distribution rooms in series, the connection capacity of each switch station is about 32250-62500 kVA. And the capacity of each switch station under the double-ring network connection and the cascade-type dual-radio connection of the distribution rooms with different numbers can be calculated in the same way.

In the medium-voltage backbone network, the 10kV outgoing cables of the transformer substation comprise cables with sections of 300 square millimeters, cables with sections of 400 square millimeters, double cables with sections of 400 square millimeters and the like. The cables with different cross sections are different from cables laid in the calandria in air in carrying capacity. For example, a 400mm2 cross-section cable is laid in air with a current carrying capacity of 646A. When the load rate of the distribution transformer is 50 percent and the synchronous rate of the switch stations is 0.6, the capacity of the single-circuit power line laid in the air is 37295 kVA.

It can be calculated that, in areas with high requirements on power supply reliability:

if the distribution room of the sub-grid network adopts a direct distribution type dual-emission mode, the number of double-ring networks or double-petal series switch stations led out from a transformer substation is recommended to be 2.5-4.7;

if the distribution room of the sub-grid network adopts a double-loop network mode, the number of double-loop networks or double-petal string switch stations led out from a transformer substation is 1.8-3.5;

if the sub-grid distribution room adopts a direct distribution type double-emission and double-loop network equal proportion mixing mode, the number of double-loop networks or double-petal string switch stations led out from a transformer substation is recommended to be 2.1-4;

and similarly, the number of the outgoing lines of the transformer substation corresponding to the switch stations can be calculated in a direct distribution type double-emitting and double-loop network wiring different proportion mixing mode of the sub-network.

In areas with low requirements for power supply reliability:

the distribution room of the secondary network adopts a cascading dual-emission mode, 4 distribution rooms are cascaded, and the number of double-ring networks or double-petal series switch stations led out from a transformer substation is recommended to be 0.9-1.7; in the same way, when the number of the cascaded distribution rooms is respectively 3, 2 and 1, the number of double-ring networks or double-petal string switch stations led out by the corresponding transformer substation is respectively 1-2, 1.4-2.6 and 1.8-3.5. And further calculating the number of the outgoing lines of the transformer substation corresponding to the switch stations in a mixed mode according to different proportions.

Table 1 shows the number of switching stations proposed for different access modes calculated quickly by this method.

TABLE 1 summary of the number of switchyard in series

In an urban medium-voltage distribution network, the outgoing line of a transformer substation takes a switch station as a core, and a wiring mode of the transformer substation, the switch station and a distribution room is recommended.

The wiring mode of a medium-voltage backbone network formed by a transformer substation and a switch station is a double-ring network wiring mode or a double-petal wiring mode; in a medium-voltage sub-grid network formed by a switch station and a distribution room, a double-ring network wiring and a direct distribution type bijection wiring are selected in a wiring mode of a power supply area with high requirement on reliability, and a cascaded double-access wiring with different cascade numbers is selected in a power supply area with low requirement on reliability.

On the basis of the first point, the invention provides a faster and more convenient calculation method, namely a method for quickly calculating the number of transformer substation feeder line string switch stations by taking the load capacity of a medium-voltage distribution network line as a boundary condition and the load connected with the switch stations as a variable.

The invention utilizes the mode of hierarchically planning the medium-voltage distribution network, thereby satisfying the reliability and realizing the difference. The capacity of the switch stations under different wiring modes can be rapidly calculated, and the number of the corresponding transformer substation outlet series switch stations is suggested. Systematic planning is carried out in advance in the construction of the medium-voltage distribution network, decision is given first, and the requirements for medium-voltage power grid transformation in the later period are reduced.

The above-mentioned serial numbers of the embodiments of the present application are merely for description and do not represent the merits of the embodiments.

In the above embodiments of the present application, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units may be a logical division, and in actual implementation, there may be another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, units or modules, and may be in an electrical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.

The foregoing is only a preferred embodiment of the present application and it should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims (19)

1. A medium voltage power distribution grid system, comprising:

the medium-voltage backbone network comprises at least one transformer substation and at least one switching station, and leads out wires from the low-voltage side of the transformer substation to the switching station by taking the switching station as a center and adopting any one of a double-petal wiring mode and a double-loop network wiring mode;

the medium-voltage branch network comprises at least one distribution room and at least one switching station, wherein the distribution room is used as a load node, and any one of a direct distribution type double-radio network connection mode, a double-ring network connection mode and a cascading type double-radio network connection mode is adopted to lead out wires from the low-voltage side of the switching station to the distribution room;

and the control equipment is used for matching and obtaining the number of the switch stations in the outgoing line string of the transformer substation according to the capacity of the distribution room in the geographic range.

2. The system according to claim 1, wherein, in the case that the medium voltage backbone network adopts the dual-ring network connection mode, different segments of buses of different substations respectively supply power to ring networks formed by the medium voltage backbone network, and the switching stations in the medium voltage backbone network all have multiple power supply incoming lines.

3. The system according to claim 2, characterized in that in case of a failure of a main line in the medium voltage backbone network, the switching station connected to the main line is controlled to open and the other switching stations are controlled to close so that the non-failed section in the medium voltage backbone network is restored to supply power.

4. The system according to claim 2, characterized in that in case of a failure of the feeder line of any one of the switchyard in the medium voltage backbone network, any one of the switches of the switchyard with the failed feeder line is controlled to be opened so that the other loads in the medium voltage backbone network are continuously powered.

5. The system according to claim 2, characterized in that in case of a failure of a bus bar of any one switching station in the medium voltage backbone, all switches of the switching station with the failed bus bar are controlled to open and other switching stations to switch on, so that non-failed sections in the medium voltage backbone are restored to supply power.

6. The system according to claim 1, wherein in the case that the medium voltage backbone network adopts the dual petal cabling mode, the same section of bus of at least two different substations respectively supplies power to a ring network formed by the medium voltage backbone network, and performs loop-closing operation, wherein the switching stations in the medium voltage backbone network all have multiple power supply incoming lines.

7. System according to claim 6, characterized in that in case of a failure of a main line of the medium voltage backbone, the switching of the switchyard connected to the main line is controlled to be opened so that any switchyard in the medium voltage backbone is powered by both directions of the two substations.

8. The system of claim 6, wherein in case of a failure of the feeder line of any one of the switchyard in the medium voltage branch network, any one of the switches of the switchyard with the failed feeder line is controlled to be opened so that any one of the switchyard in the medium voltage backbone network is powered by bidirectional power from two substations.

9. The system of claim 6, wherein in case of a failure of a bus of any one switchyard in the medium voltage branch network, all switches of the switchyard with the failed bus are controlled to open and the other switchyards are controlled to close so that any one switchyard in the medium voltage backbone network is powered by bidirectional power from both substations.

10. The system of claim 1, wherein in the case of the direct distribution twinshot mode, two different medium voltage buses of any one switchyard in the medium voltage branch network each lead out a return line, and the switchyard in the medium voltage branch network operates in an open loop, and the distribution room power supply is from different bus sections of the same switchyard.

11. The system according to claim 10, wherein in case of a line fault from any one switching station to the distribution room in the medium voltage branch network, the feeder current protection switch of the superior switching station is opened, and after a delay time period is reached, the sectionalized backup automatic switching no-voltage switching-off function of the distribution room is started, and the sectionalized switch is closed, so that the power supply is recovered.

12. The system of claim 10, wherein in case of a fault of a distribution room bus in the medium voltage branch network, a switch for protecting the distribution room line from overcurrent is turned on and locks the high-voltage backup automatic switch of the distribution room, and after a non-voltage delay, a non-voltage tripping function of the segmented backup automatic switch is started, and the segmented switch is switched on, so that power supply is recovered.

13. The system of claim 10, wherein in case of a fault of a distribution room transformer in the medium voltage branch network, a switch of a transformer protector of the distribution room is controlled to be opened, and after a non-voltage delay, a non-voltage switching-off function of the segment backup automatic switch is started, and a switch of the segment switch is controlled to be closed, so that power supply is recovered.

14. The system of claim 1, wherein in the case of the medium voltage branch network in the dual loop network connection mode, two different medium voltage buses of any one switching station in the medium voltage branch network each lead out a return line, and are operated in an open loop, and the distribution room power in the medium voltage branch network is from different bus sections of the same switching station.

15. The system according to claim 14, characterized in that in case of a fault in any section of line in the medium voltage branch network, the feeder current protection switch of the switching station on the faulty line is opened, please activate the no-voltage-drop function of the distribution room on the faulty line.

16. The system of claim 1, wherein in the case of the medium voltage branch network in the dual-wire mode, two different medium voltage buses of any one switching station in the medium voltage branch network each lead out a return line, and are operated in an open loop, and the distribution room power in the medium voltage branch network is from different bus sections of the same switching station.

17. The system of claim 16, wherein in the event of a failure of the trunk line of any one of the distribution rooms in the medium voltage branch network, the switchyard feeder current protection switch on the trunk line of any one of the distribution rooms is controlled to trip and activate the no-voltage-drop function of that distribution room, and the other distribution room line switches in the medium voltage branch network are all open.

18. The system of claim 16, wherein in the event of a failure of a bus of any one of the distribution rooms in the medium voltage branch network, the line overcurrent protection switch of the any one of the distribution rooms is controlled to open and the high voltage backup power automatic switching of the distribution room is blocked.

19. The system of claim 16, wherein in the event of a failure of a transformer of any one of the distribution rooms in the medium voltage branch network, the transformer protection switch controlling that distribution room trips and the switches on both sides of the transformer open.

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