WO2010087563A1

WO2010087563A1 - Power distribution system using 3-phase power cable

Info

Publication number: WO2010087563A1
Application number: PCT/KR2009/005882
Authority: WO
Inventors: 전명수
Original assignee: Jun Myung Soo
Priority date: 2009-01-30
Filing date: 2009-10-13
Publication date: 2010-08-05
Also published as: KR20100088481A

Abstract

The present invention relates to a power distribution system using a 3-phase power cable. The power distribution system comprises a plurality of 3-phase power cable bundles including concentric neutral cables, the front end of each concentric neutral cable on each phase is grounded simultaneously at each interval in which the concentric neutral cables at each bundle are disconnected and are divided; the back end of each concentric neutral cable is connected to the front end of the next concentric neutral cable in only one selected phase at the next interval, the back end of concentric neutral cable in other phases at each interval is opened; and the power cable in a phase which is selected from the 3-phase power cable is on the same phase at the corresponding interval so that the back end of the each concentric neutral cable at each interval is connected to a front end at next interval. If plural 3-phase power cables are used, the increase of a leakage current flowing in a connection member is prevented by simultaneously grounding the front end of each concentric neutral cable on each phase at each interval to an additional grounding point, connecting the back end of each concentric neutral cable in one randomly-selected phase to the front end of the next concentric neutral cable at the next interval, and opening the back end of the concentric neutral cable in other phases at the corresponding interval, thereby allowing feedback of a ground fault current and raising the ground potential of the concentric neutral cable.

Description

3-phase power cable distribution system

The present invention relates to a three-phase power cable distribution system, and more particularly to a three-phase power cable distribution system consisting of a plurality of three-phase power cable bundle having a concentric neutral wire.

In the power system of our country, 22.9KV-Y power distribution system can directly supply relatively large audiences such as factories, buildings, etc. through power distribution lines installed on the ground and underground from power plants or small factories through secondary transformers. The main trunks are used to supply power to ordinary households.In the outskirts of urban areas or in rural areas, power lines are supplied to the underground in the form of overhead lines, taking into consideration the aesthetics of the city in places where people come and go, such as the centers of large cities, and new urban areas. In operation, it adopts a multiple grounding method in which the concentric neutral line of the distribution line is grounded at certain intervals.

1 is a wiring diagram of a power cable according to the prior art.

Since the multi-grounding method directly grounds the concentric neutral wire to the ground, there is little voltage rise in the event of a ground fault, so that the insulation of the power equipment and the detection of the ground fault current are easy, and the protective relay operates quickly.

In the case of underground distribution lines, cross-linked polyethylene insulated vinyl sheath cables using high molecular compounds such as polyethylene are mainly used to protect the cable from insulation and cable damage or corrosion, and to prevent the potential of concentric neutral wires from rising due to system accidents. Wiring is performed by collectively grounding the concentric neutral wire for each section.

However, it is difficult to accurately balance the loads of each phase (A, B, C phase) in the underground distribution line, and even in the case of approximately equilibrium, as shown by the dotted line in FIG. This leads to unnecessary loss of power, which increases the internal temperature of the cable, reduces its current capacity, and leads to distribution line losses. When measuring load current, the instrument displays the combined value of the actual load current of the distribution line and the circulating current of the concentric neutral wire, which is not only dangerous due to the circulating current, but also difficult to operate the wiring line because the actual load is not measured accurately. have.

Meanwhile, in FIG. 1, since the circulation loop through the earth acts on the equivalent ground resistance (Rg) by the earth, the circulating current is only about 1 to 2 amperes (A), and the effect on the line loss and cable capacity is negligible. It doesn't matter. However, as shown in FIG. 2, when the grounding ground line is separately installed and grounded through the grounding line, a closed circuit is formed through the grounding wire, and an equivalent ground resistance by the ground does not work, so a large circulating current flows, resulting in a large power loss and an accident. There is a problem that the risk of exposure to such a large increase.

In order to reduce the line loss of the power cable due to the circulating current of the concentric neutral wire, in spite of the balance or unbalance of the load current in the extra-high voltage underground distribution line of the multi-ground system, the circulating current is not generated between the concentric neutral wires. A device for stably supplying and suppressing the occurrence of abnormal voltage in a distribution line by limiting the potential rise of the concentric neutral line in the event of an abnormal voltage such as a ground fault is disclosed in Korean Patent No. 10-0438094 (Registration date June 21, 2004) 3), which combines a voltage suppressor (current and overvoltage suppressor, 40) per concentric neutral ground, as shown in FIG.

The abnormal voltage suppression device 40 shown in detail in FIG. 4 includes an iron core core 10 and a coil winding portion 20 in which a coil is wound around a portion of the iron core core portion 10, and the coil winding portion 20. It may be configured to set a set voltage by including a plurality of tabs 30 so that the terminal can be drawn out every predetermined winding of the device, this type of device will be referred to as a coil winding voltage suppression device in the present invention.

In addition, Korean Patent Application No. 10-2005-41139 proposes further improved inventions. For example, the wiring of FIG. 5 is a concentric neutral line for phase A in the first section and a concentric neutral line for phase A in the second section. Are interconnected, the concentric neutral line for phase B in the second section and the concentric neutral line for phase B in the third section, and the concentric neutral line for phase C in the third section and phase C for phase 4 The concentric neutral line is connected by repeating the effect of connecting the effect.

As a result, each phase is continuously connected in every three sections, so that a circulating circuit is formed only between the concentric neutral lines of A, B, and C phases, and a circulating current does not flow between the concentric neutral lines of each phase. Reduced current losses or reduced cable capacity.

In addition, since the connection of the power cable of FIG. 6 proposed in Korean Patent Application No. 10-2005-41139 is grounded through the voltage suppressing device 40, even the circulating current through the normal earth which is a problem that may occur in the example of FIG. Since the circulating current is suppressed and the impedance of the voltage suppressor 40 is reduced when the ground fault occurs, the potential of the concentric neutral line is increased because it must be made through the voltage suppressor 40 having the high impedance.

In addition, the power cable connection of FIG. 7 proposed in Korean Patent Application No. 10-2005-41139 is to change the color of the A phase among the A, B, and C phases, and to increase the current capacity of the concentric neutral wires to convert them to neutral wires, which is usually unbalanced. The load current flows and the fault current can flow in case of a ground fault.

However, the above-described conventional inventions have a problem in that actual construction is difficult and a lot of investment costs are not easily applicable.

That is, although the invention of FIG. 5 reduces the circulating current, there is still a disadvantage in that the circulating current is formed through each of the concentric neutral lines and the ground, and there is a line loss. There was a real problem.

In addition, in the case of FIGS. 6 and 7, the disadvantage of the line power loss due to the circulating current through the ground in FIG. 5 is solved, but in the case that the fault current is applied and the voltage is not induced at a predetermined voltage or higher, the voltage may vary depending on the line length. There is a concern that a safety problem may occur that increases and exceeds the maximum allowable voltage. For example, if 595 A flows over a 325 mm2 cross-section cable, if it exceeds about 1700 m, the induced voltage on the concentric neutral will exceed the maximum allowable voltage of 100 V, which will not meet safety design criteria. In addition, the voltage and current capacity of the voltage suppression device required in preparation for the ground fault is increased to 13,200V and 8000A or more, respectively, increasing the volume and capacity and increasing the unit cost, thereby significantly reducing economic efficiency and practicality.

The technical problem to be solved by the present invention is to eliminate the formation of a circulating loop, to configure a proper direct ground to reduce the line loss and to improve the safety. It is still another object of the present invention to provide a power distribution system that significantly improves safety and workability by converting one phase of concentric neutral wire into a neutral wire and improving identification. It is also aimed to provide a power distribution system with a separate ground wire, if possible, installed alongside the cable, further improving safety and workability. In addition, when there are a plurality of three-phase power cable bundles, the purpose of the earth potential is to rise to prevent the leakage current increases in the connecting member.

According to one aspect of the invention, there is provided a three-phase power cable distribution system comprising a plurality of three-phase power cable bundles having a concentric neutral wire. In this system, the concentric neutral wire front end of each phase is collectively grounded in each section where the concentric neutral wire is disconnected and separated for each bundle, and the rear end is connected to the front end of the concentric neutral wire of the next section only for one selected phase, and each section The rear end of the concentric neutral wire of the other phases of the other phase is configured to be open, and in each section, the power cables selected phases of the three-phase power cables are all the same phase in the corresponding interval such that the rear end of the concentric neutral wire is connected to the front end of the next section. .

In an embodiment of the present invention, the power loss is reduced by eliminating or reducing the circulating current generated through the closed loop of the power cable, and improving the safety by preventing the increase of the voltage of the concentric neutral wire which may appear as the length increases. to provide. In addition, when the dedicated neutral wire is used, the cable wiring cost can be greatly reduced by relatively reducing the capacity of the concentric neutral wire of the other phase. In addition, since the length of the concentric neutral line of the cable is long, even when the voltage suppression device is used at the other end, the voltage suppression device is miniaturized, thereby greatly reducing the cost. In another aspect, the present invention provides a method of grounding the cable concentric neutral wire is simple and economical construction and management.

In addition, in the present invention, when there are a plurality of three-phase power cable bundles, only a randomly selected phase is connected to the front end of the concentric neutral in the next section, and the rear end of the concentric neutral in the other phase of the section is opened, so that the fault current is returned when the ground fault occurs. It is possible to prevent the ground potential of the concentric neutral wire from rising to increase the leakage current in the connecting member.

1 is a wiring diagram of a power cable according to the prior art.

2 is a wiring diagram of a power cable according to the related art in which a ground line is separately installed.

3 is a wiring diagram of a power cable using a voltage suppressing device according to the prior art.

4 is a circuit diagram of a voltage suppression apparatus used in the prior art.

5 is a wiring diagram of a power cable according to an embodiment of the prior art.

6 is a wiring diagram of a power cable according to another embodiment of the prior art.

7 is a wiring diagram of a power cable according to another embodiment of the prior art.

8 is a wiring diagram of a power cable according to a first embodiment of the present invention.

9 is a wiring diagram of a power cable according to a second embodiment of the present invention.

10 is an example of a voltage suppression device according to the present invention.

11 is a wiring diagram of a power cable according to a third embodiment of the present invention.

12 is a wiring diagram of a power cable according to a fourth embodiment of the present invention.

13 is a wiring diagram of a power cable according to a fifth embodiment of the present invention.

14 is a wiring diagram of a power cable according to a sixth embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, when a part is "connected" with another part, this includes not only the "directly connected" but also the "electrically connected" with the other element in between.

Now, a three-phase power cable distribution system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In this embodiment, the front ends of the concentric neutrals of each phase are collectively grounded in each section divided by about 300m, and the rear end connects only one phase selected arbitrarily to the front of the concentric neutrals of the next section, and the concentric neutrals of the other phases of the other sections. The rear end of is opened so that no closed loop is formed between the concentric neutrals of each phase so that no circulating current is generated. At this time, the phase to which the front and rear ends of the concentric neutral line of one section and the next section are connected is randomly selected. This provides a technical effect of effectively blocking the circuit formation while significantly improving workability in a narrow underground work space. As mentioned earlier in FIG. 1, the circulating loop through the earth has a low circulating current because the equivalent ground resistance (R _g ) is acted on by the earth, and thus the effect on line loss and cable capacity is negligible.

Therefore, in the first embodiment according to the present invention, the power loss is prevented by eliminating unnecessary circulating loops, and the front end of the concentric neutral line of each section is directly grounded, so that the current suppression apparatus as shown in FIG. Alternatively, unnecessary voltage increases on concentric neutrals are prevented, reducing the usual induced voltage to within 100V, the design criterion, and reducing surge voltages.

In the second embodiment, one end of the concentric neutral wire of each phase is collectively directly grounded for each section divided by about 300 m, and the concentric neutral wire of each section is connected in turn to only one phase (for example, A phase) in order to form a neutral wire. Is to use. At this time, the other end of the concentric neutral line of the remaining phases (for example, B and C phases) of each section is opened so that no closed loop is formed between the neutral lines of each phase so that a circulating current is not generated. to be. The second embodiment differs from the first embodiment in that one phase of concentric neutral lines is used as dedicated neutral lines.

In the second embodiment, the current capacity of the concentric neutral wire to be converted into the neutral wire is larger than the other phases, thereby allowing an unbalanced load current to flow in normal times, minimizing the voltage increase according to the distance from the ground point, and smoothly the fault current in case of a ground fault. It is desirable to allow flow. The capacity of power lines and concentric neutrals in other phases except for cables dedicated to neutrals may be increased by increasing the current capacity of power lines and dedicated neutrals to increase the current capacity of power lines and dedicated neutrals of cables to be converted into neutrals. It is more desirable to achieve this by relatively reducing. Since the power line of the other phase has no circulating current in the concentric neutral line, the allowable current is increased and the concentric neutral line needs only enough capacity to handle the fault current, thereby reducing the size of the power line and reducing the number of strands forming the neutral line. Or by using copper tape, it is possible to save even more facility costs.

In addition, in the second embodiment, it is easy to construct even in a narrow underground work space by providing identification so that it can be easily distinguished from the others by varying the thickness, color, shape, etc. of the neutral wire cable (power line, concentric neutral wire). It is desirable to be able to prevent accidental connection of cables.

Increasing the current capacity of the cables (power lines, concentric neutral lines) to be converted into neutral wires, or giving identification to them, in particular, is applied to newly installed distribution lines, thereby increasing work efficiency than the first embodiment capable of working on existing distribution lines. This has the advantage of reducing costs.

In particular, if the constant current capacity is large or the cable section is long (illustrated as the fourth section in FIGS. 8 and 9), the open ends of B and C are connected via voltage suppressors (current and overvoltage suppressors). It is preferable to ground. This voltage suppression device is connected to the coil winding type voltage suppression unit 200 and the surge protector 100 in parallel as shown in FIG. 10 to pass the abnormal voltage as well as the surge voltage of the commercial frequency, the brain surge or open and close surge It is desirable to protect the insulation of the external insulation layer from abnormal voltages generated by the above-described voltage and to prevent an electric shock accident. Even in this case, since one end of the concentric neutral line of each section is directly grounded, the voltage rise is significantly lower than that of the prior art, so that the capacity and size of the voltage suppression device can be downsized to about tens of conventional ones.

11 is a wiring diagram of a power cable according to a third embodiment of the present invention. As shown in FIG. 2, when a separate ground line is provided, excessive circulating current may be generated in a loop formed through the ground line as described above. As indicated, it must be grounded with the ground wire via a voltage suppressor. In other words, the concentric neutral line is single-sided with respect to the ground line at each front end, and grounded through a voltage suppression device. The rear end is connected to the front end of the next section and the concentric neutral line of the remaining phases is opened. The phase to which the rear and front ends are connected can be selected at random. Also in this case, especially if the constant current capacity is large or the cable section is long (exemplified by the fourth section in Fig. 11), it is preferable that the open end is grounded via a voltage suppressor. In addition, it is preferable that the constant voltage value of the voltage suppression device is adjusted low for each predetermined number of sections so that the voltage does not rise above the allowable value over several sections, and the constant circulating current is limited to a certain set value or less.

12 is a wiring diagram of a power cable according to a fourth embodiment of the present invention. In the fourth embodiment, as in the third embodiment, a ground wire is provided or a technical feature of the second embodiment is added. In each section, one end of the concentric neutral wire of each phase is collectively directly grounded and only one phase is connected. Concentric neutral wires of each section are connected in sequence to (for example, phase A) and used as neutral wires. The fourth embodiment differs from the third embodiment by using a concentric neutral line of one phase as a dedicated neutral line.

Also in the fourth embodiment, as in the second embodiment, it is preferable to increase the current capacity of the power line and the concentric neutral line of the cable to be converted into the neutral wire, or to give identification.

In a real power system, two or more three-phase power cables pass through one passage. When a three-phase power cable is referred to as one bundle, the following describes a case where there are a plurality of three-phase power cable bundles in one passage.

13 is a wiring diagram of a power cable according to a fifth embodiment of the present invention. In a power distribution system having two or more three-phase power cable bundles, when the ground line and the ground are grounded through a voltage suppressor as shown in FIGS. 11 and 12, the circulating current may be reduced, but the ground potential of the concentric neutral line may increase. Leakage current may increase in the connecting material and be damaged. In order to solve this problem, the fifth embodiment shows a three-phase power wiring system in which a plurality of three-phase power cable bundles are provided. It is collectively grounded to an individual ground, and the rear end is connected to the front end of the concentric neutral line of the next section for only one selected phase, and the rear end of the concentric neutral line of the other phase of each section is configured to be open. The phase to which the rear end and the front end are connected may be randomly selected, but in each section, the power cable selected among the three phase power cables must be the same phase in the section so that the rear end of the concentric neutral line is connected to the front section of the next section.

In the case of multiple three-phase power cables, the front ends of the concentric neutrals of each phase are collectively grounded to one individual ground for each section, and the rear end is connected to only one of the arbitrarily selected phases to the front of the concentric neutrals of the next section. By opening the rear end of the concentric neutral wire of the other phase, it is possible to prevent a fault current from returning to the ground fault and increasing the earth potential of the concentric neutral wire to increase the leakage current in the connecting member.

14 is a wiring diagram of a power cable according to a sixth embodiment of the present invention. In the sixth embodiment, as in the fifth embodiment, there are two three-phase power cable bundles, and in each section, one end of the concentric neutral wire of each phase is collectively directly grounded, and only for one phase (for example, A phase). Concentric neutral wire of each section is connected in order to use as neutral wire. At this time, the other end of the concentric neutral line of the remaining phases (e.g., B and C phases) of each section is opened, and when the ground fault occurs, the fault current is returned and the ground potential of the concentric neutral line is raised to prevent the leakage current from increasing in the connecting member. The configuration is the same as in the fifth embodiment. The sixth embodiment differs from the fifth embodiment in that one phase of the concentric neutral wire is used as a dedicated neutral wire, and in each section, the front end of each phase of the concentric neutral wire is grounded in common to the ground wire separately installed alongside the three-phase power cable bundle. will be.

Also in the sixth embodiment, as in the second embodiment, it is preferable to increase the current capacity of the concentric neutral wire to be converted into the neutral wire or to impart discrimination.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims

In the three-phase power cable distribution system consisting of a plurality of three-phase power cable bundle having a concentric neutral wire,

The concentric neutral line front of each phase is collectively grounded in each section where the concentric neutral line is disconnected and separated for each bundle, and the rear end thereof is connected to the front end of the concentric neutral line of the next section only for one selected phase, and the other phases of the other sections of each section. The rear end of the concentric neutral wire is configured to be open,

3. The power distribution system of claim 3, wherein the selected power cables of the three phase power cables are all in the same phase so that the rear end of the concentric neutral wire is connected to the front end of the next section in every section.
The method of claim 1,

The power cable selected phase of the three-phase power cable is the same phase in all sections so that the rear end of the concentric neutral line in each section is connected to the front end of the next section, the three-phase power, characterized in that the same phase concentric neutral line is used as a dedicated neutral line Cable distribution system.
The method of claim 2,

And the current capacity of the concentric neutral wire used as the dedicated neutral wire is relatively larger than the concentric neutral wire of the other phases.
The method of claim 2,

The current capacity of the power line of the cable used as the dedicated center line is relatively larger than the power line of the cable of the other phases, characterized in that the three-phase power cable distribution system.
The method of claim 2,

The three-phase power cable distribution system, characterized in that the concentric neutral wire used as the dedicated neutral wire has a distinction from other phases.
The method of claim 5,

Three-phase power cable distribution system, characterized in that the identification of the concentric neutral wire used as the dedicated neutral wire is obtained by changing the thickness, color or shape.
The method of claim 1,

And a ground line separately installed in parallel with the three-phase power cable bundle, wherein the grounding ground is grounded through a grounding resistor.