JP2000261956A - Voltage drop control wiring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce voltage drop of power feeding line, simplify cable laying work and moreover also reduce laying cost and laying area. SOLUTION: A small-sized pressure-proof and explosion-proof connection box 4 for connecting an ultra-multicore low impedance cable 3 and a 3-core cable 2 is installed at an area near a tank 10, the 3-phase power is fed to the pressure-proof and explosion proof connection box 4 from an electrical chamber 7 using the ultra-multicore low impedance cable 3, and the pressure-proof and explosion-proof connection box 4 is connected to the 3-core cable 2. The 3-core cable 2 is connected to a low temperature cable 5 at a terminal header 6, provided through the separation wall of the tank 10 to fed the power to a pump motor 1. Since power is fed to the area near the pump motor 1 using the ultra- multicore type low impedance cable 3, even if the power factor of pump motor is low, voltage drop of the power feeding line can be reduced, and since it is required to lay one cable, the cable laying work can be simplified and cost can also be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to LNG or LNG.
The present invention relates to a voltage drop suppression wiring system for supplying power to a pump motor installed in a liquid such as a PG storage tank.

[0002]

2. Description of the Related Art Conventionally, a three-core cable has been used to supply a three-phase power to a motor for a pump installed in a liquid in an LNG or LPG storage tank. FIG. 4 shows a conventional example in which electric power is supplied to the pump motor 1 installed in the LNG tank 10. From the pump motor 1 installed in the LNG tank 10, a three-core low-temperature cable 5 that withstands the low temperature of LNG emerges, and the three-core low-temperature cable 5 has a low temperature of the terminal header 6 that penetrates through the tank partition. Side (inside the tank). A commonly used three-core cable 2 is connected to the high temperature side (outside air side) of the terminal header 6.
The core cable 2 is connected to a power supply of a remote electric room 7.

[0003]

In recent years, as the size of an LNG or LPG storage tank or the like has been increased, the distance between an electric room in which power is supplied and a pump motor has been greatly increased. Along with this, the length of a cable that feeds an electric motor has become longer, and a voltage drop has become more important than the allowable current of the cable. As described below, the voltage drop is determined by the conductor resistance and reactance of the cable and the power factor of the current. When the power factor is bad, the magnitude of the reactance greatly affects the voltage drop.

The voltage drop of an AC voltage long-haul cable line is represented by a vector as shown in FIG. The voltage drop is (current) × (AC resistance), but the power supply voltage E
On the other hand, if the load current used is the delay angle θ (cos θ is called the power factor), the voltage drop I due to the conductor resistance of the cable
R, a voltage drop IX occurs due to the reactance of the cable, and the receiving end voltage becomes Er. That is, the voltage drop ΔV
Is Es-Er. Actually, since the cable size is selected so as to reduce the voltage drop ΔV, Es−
The vector angle difference of Er is small, and the voltage drop is as shown in FIG.
The calculation can be approximately performed using the horizontal dotted line in FIG.
The horizontal dotted line in the figure is (R · cos θ + X · sin θ). Therefore, the voltage drop of the cable line is calculated by the following equation by multiplying 1.73 for three phases by the distance L. △ V
= 1.73 × IL · (R · cos θ + X · sin θ)

Next, the current characteristics of the load motor will be described. Electric motors used for LNG or LPG storage tanks are often cage-type induction motors with high explosion-proof safety.
In a squirrel-cage induction motor, a rotating body (cage-shaped rotator) arranged inside rotates due to a rotating magnetic field generated in an outer stator, but at the time of startup, the rotating body rotates slowly with respect to the rotating magnetic field. Minutes are big. For this reason, the current at startup is affected by the reactor of the motor, and the power factor (cos
θ) is as bad as about 0.2. At this time, sin θ = 0.98.

An example of a conventional wiring system is as follows. A power supply voltage of 440 V is 600 V, 3 cores, 325 mm ^2.
Two cables are laid at a distance of 1 km. Note that the distance 1 km (the distance between the storage tank and the power supply room) is a value determined from the layout. This cable has one conductor resistance and various reactance, R = 0.0808Ω / k
m (at 90 ° C.), X = 0.0714Ω / km. When the load current is 300 A, the voltage drop is as follows. ΔV = 1.73 × 300 × 1.00 × (0.0808 ×
0.2 + 0.0714 × 0.98) /2=22.4V A voltage drop of 5.1% with respect to the power supply voltage of 440V.

The actual procedure is as follows. After the cable route is determined, the voltage drop is calculated for each cable conductor size and number based on a voltage drop of about 5%, and the current capacity is calculated. Choose a number. As the distance increases, it is necessary to use a cable having a larger size to further reduce the voltage drop. However, a load having a bad power factor (such as an induction motor) is greatly affected by reactance, so that the use of a large-sized cable does not reduce the reactance so much. Therefore, there is little improvement in voltage drop. As a countermeasure, it is conceivable to increase the number of cables. However, since the cable laying construction cost is almost proportional to the number of the cables, there arises a problem that the construction cost increases. Further, when the number of cable strips is increased, there is a problem that a cable installation route area increases.

As a countermeasure against this, a low impedance cable (hereinafter, such a cable is referred to as a super multi-core low impedance cable) having a large number of cores and a devised arrangement is used to particularly reduce the reactance. It is conceivable that the three-phase power source is transmitted to the vicinity of the used motor using an impedance cable, and is connected to a three-core cable on the outside air side of the used motor by a connection box. However, the conventional connection box has the following problems.

FIG. 6 shows a junction box for a low-impedance cable having a total of 12 cores and a three-core cable with three phases and four cores whose impedance is not sufficiently reduced. Junction box 5 shown in FIG.
At 0, each wire core 51 is branched from a low impedance cable at a portion (not shown), and a terminal 52 is attached to each wire core 51 of the low impedance cable in the connection box 50. Then, each terminal 52 is fixed to the connection conductor (bus bar) 53 in each phase (four terminals for four wire cores in FIG. 5) by bolting. On the other hand, the terminal 54 is attached to each core wire 55 of the other party's three-core cable 56, and is fixed to the connection conductor (bus bar) 53 for each phase by bolting. Connection. Then, both the cable end portions and the connection conductor (bus bar) are stored in a large box 57.

The dimensions of the junction box shown in FIG. 6 are as large as 1230 mm in height, 1050 mm in width, and 400 mm in thickness even for a 12-core connector. In order to further reduce the impedance, it is necessary to increase the number of wire cores, but the connection box becomes larger and the connection operation becomes complicated. Also, in order to install such a junction box near a tank that requires explosion-proof, measures must be taken to make it even more flame-proof.
It becomes larger and the workability is inferior. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wiring system for supplying power to a pump motor installed in a liquid such as an LNG or LPG storage tank. The object of the present invention is to reduce the descent, facilitate the cable laying work, and further reduce the laying cost and laying area.

[0011]

In order to solve the above-mentioned problems, in the present invention, a small explosion-proof connector for connecting a super-multi-core low-impedance dance cable and a three-core cable is installed near a pump motor. Then, a three-phase power source is transmitted to the explosion-proof connection type using an ultra-multi-core low-impedance cable, and the three-phase power supply is connected to the three-core cable for supplying power to the pump motor at the explosion-proof connection type. It was done. In the present invention, as described above, the pressure-resistant explosion-proof type connection is installed near the pump motor, and power is transmitted to the vicinity of the pump motor using a super multi-core low impedance cable. Can be suppressed, and power can be supplied by a single cable, so that the cable laying operation can be facilitated and the laying cost, laying area, and the like can be reduced.

[0012]

1 shows the configuration of a wiring system according to an embodiment of the present invention for supplying power to a pump motor 1 installed in an LNG tank 10. FIG. In the figure, LNG
LN from the pump motor 1 installed in the tank 10
A three-core low-temperature cable 5 that can withstand the low temperature of G is provided. 3
The core low-temperature cable 5 is connected to the low-temperature side (inside the tank) of the terminal header 6 that penetrates the tank partition. A normal three-core cable 2 is connected to the high temperature side (outside air side) of the terminal header 6. The three-core cable 2 is connected to an ultra-multi-core low impedance cable 3 at a pressure-resistant explosion-proof connection part 4 in the vicinity of the tank 10. The super multi-core low impedance cable 3 is connected to a power supply of a remote electric room 7.

FIG. 2A shows a cross-sectional configuration of the super multi-core low impedance cable 3 used in this embodiment. The super multi-core low impedance cable of this embodiment has
Phase and Z phase. One phase has 16 cores, that is, the total of three phases has 48 cores. Each wire core has a structure in which an insulating coating 22 is provided around a conductor 21 as shown in FIG. Note that reference numeral 25 denotes a pressing tape, and an outer package 31 is provided on the outermost layer. Returning to FIG. 1, the terminal header 6
The three-phase three-core cable 2 is connected between the super-multi-core low impedance cable 3 and the three-phase three-core cable 2 used in this embodiment is a cable having a normal structure. The cross-sectional structure is as shown in FIG.
, An insulation coating 28 is provided around the wire, a three-wire core is circularly fitted together with the inclusion 29, and an exterior 32 is provided.

FIG. 3 shows an example of an explosion-proof explosion-proof type connecting portion 4 for connecting the super multi-core low impedance cable 3 and the three-core cable 2 used in the present embodiment. In the explosion-proof connection section 4 shown in FIG. 1, the phase conductors 3a, 2a of the super multi-core low impedance cable 3 and the three-core cable 2 are connected by conductor connection contacts 41, 42. That is, 16 cores of the same phase of the super multi-core low impedance cable 3 are connected to one conductor connection connector 41. In addition, one conductor of the conductor of the three-core cable 2 is connected to the connection connector 42 of one conductor (3
Since the phase is a phase, three contactors 41 and 42 are provided respectively).

The conductor connecting contact 41 is provided with a protruding portion, and the conductor connecting contact 42 is provided with an insertion hole to be fitted into the protruding portion, and the conductor connecting terminal 41 of each phase is provided. , 42 and both cables are subjected to insulation treatment 43a, and then the protruding portion of the conductor connection connector 41 is inserted into the insertion opening of the conductor connection connector 41 and fixed as shown in FIG. The conductors of each phase of both cables are electrically connected. Further, insulation treatment 43b is performed on the conductor connecting contacts 41 and 42, and the three phases are collectively stored in the cylindrical case 46. Flanges 46a and 46b are provided at both ends of the cylindrical case 46, respectively, and the cylindrical case 46 is fixed to the cable glands 44 and 45 that meet explosion-proof standards by the flanges 46a and 46b.
The cable glands 44 and 45 are attached between the flange 46 a and the sheath of the cable 3 and between the flange 46 b and the sheath of the cable 2.

The cable glands 44, 45 are provided with packings 44a, 45a, and by tightening the packings 44a, 45a with fasteners 44b, 45b, the airtightness of the cable connection portion is ensured. A compound 47 is injected into the cylindrical case 46, and a waterproof cover 48 for protecting the main body against external damage is attached to the outer periphery of the cylindrical case 46. The waterproof cover 48 has a cylindrical shape whose lower part is open, and its upper part is locked by the cable gland 45 and fixed with screws or the like. In the connecting portion 4 having the above-described structure, each phase conductor is connected to the conductor connecting contacts 41 and 42.
Therefore, the workability of the connection work is good and the size can be reduced. In addition, the connection portion is insulated from the outside air by a cylindrical case 46 in which a compound 47 is injected, and cable glands 44 and 45 that meet explosion-proof standards are provided on both sides of the cylindrical case 46, so that explosion-proof standards are met. It has high performance and can be used near tanks that need to be flameproof.

A three-core cable and a super-multi-core low-impedance cable are connected by using the above-described connecting portion 4, and power is supplied from an electric room 7 installed at a remote position via the super-multi-core low-impedance cable. Accordingly, the impedance in the power supply path can be reduced, and the voltage drop can be reduced. Hereinafter, specific numerical examples will be described. As described above, the induction motor has a particularly bad power factor at the time of starting, and has cos θ = 0.2 and sin θ = 0.98.
On the other hand, the super multi-core low impedance cable used
The three-phase 16 cores having a current carrying capacity of 300 A (48 cores in total) are 22 mm ² . The conductor resistance and reactance of this cable are as follows. R = 0.0662Ω / km (at a temperature of 90 ° C.) X = 0.00472Ω / km

Therefore, assuming that the distance is 1 km and the current is 300 A, the voltage drop is as follows. ΔV = 1.73 × 300 × 1,00 × (0.0662 ×
0.2 + 0.00472 × 0.98) = 9.27V As described above, in the case of the conventional three-core 325 mm ² cable, the voltage drop is 22.4V. The voltage drop could be reduced to 9.27V.

Further, in this embodiment, since the number of cables can be reduced from two to one, construction costs for cable laying, cable terminal treatment, cable conduits and the like can be reduced, and furthermore, cable laying can be performed. The occupied area could be reduced. When the amount of copper, in the conventional example, when the effective cross-sectional area of the three-core ^{325mm 2, 3 × 325 × 2} = 195
In contrast to 0 mm ² , this embodiment uses 48 × 22 ×
1 = 1,056 mm ² , making it possible to greatly reduce the amount of use. In the above embodiment, a trial calculation was made for the case where the line length was 1 km. However, the effect can be further exhibited when the line length becomes long.

[0020]

As described above, in the present invention, the pressure-resistant explosion-proof connection is installed near the pump motor, and power is transmitted to the vicinity of the pump motor using a super multi-core low impedance cable. As a result, a voltage drop in the power supply path can be suppressed. In addition, since power can be supplied by a single cable, the cable laying operation can be facilitated, and the laying cost, laying area, and the like can be reduced. Further, since the conductor size of the power supply cable can be reduced, the workability of handling the cable can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a wiring system according to an embodiment of the present invention for supplying power to a pump motor installed in an LNG tank.

FIG. 2 is a diagram showing a configuration of a super multi-core low impedance cable and a three-core cable used in an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a pressure-resistant explosion-proof type connection part of a super multi-core low impedance cable and a three-core cable used in an embodiment of the present invention.

FIG. 4 is a diagram showing an example of a conventional wiring system for supplying power to a pump motor installed in an LNG tank.

FIG. 5 is a vector diagram for explaining a voltage drop in a power supply line.

FIG. 6 is a diagram illustrating an example of a conventional connection box for a 12-core low impedance cable and a 3-core cable.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pump motor 2 3-core cable 3 Ultra-multi-core low-impedance cable 4 Explosion-proof connection part 5 Low-temperature cable 6 Terminal header that penetrates a tank partition 7 Electric room 10 Storage tank (tank) 21 Conductor 22 R-phase Insulation Coating 23 K-Phase Insulation Coating 24 Z-Phase Insulation Coating 25 Pressing Tape 26 Outer 27 Conductor 28 Insulating Coating 29 Inclusion 31 Extra Multi-Core Low Impedance Cable Exterior 32 Three-Core Cable Exterior 41 Conductor Connection 42 Conductor connection contacts 43a, 43b Insulation treatment 44, 45 Cable gland 44a, 45a Packing 44b, 45b Clamping fitting 46 Cylindrical case 46a, 46b Flange 47 Compound 48 Waterproof cover

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Sato 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Inventor Hideo Negishi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa F-term (reference) in Denki Kogyo Co., Ltd. 5G013 AA01 AA11 AA13 BA03

Claims (1)

[Claims] 1. A wiring system for supplying power to a pump motor installed in a liquid such as an LNG storage tank or an LPG storage tank, wherein a super multi-core low impedance dance cable and a three-core cable are provided near the pump motor. To connect a three-phase power supply to the above explosion-proof connection using an ultra-multi-core low-impedance cable, and to supply power to the pump motor with the explosion-proof connection A wiring system characterized by being connected to a three-core cable.