JPS5920256B2 - power cable line - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electric cable line.

Metal sheathed single electrocardiogram cable lines generally use a cross-bond method to reduce the circulating current flowing through the sheath.

As shown in Figure 1, each phase cable IA, IB, I
Two or more insulating junction boxes 3 are provided for each section sandwiched between two ordinary junction boxes 2a and 2b provided for each metal sheath IAS, IBS, and IC8 of C.

Metal sheath IA of the different phase cable before and after the insulation junction box
By connecting the S, IBS, and IC8 comrades using the bonding wire 4, the circulating voltage induced in the metal sheaths IAS to IC8 is canceled out, and the metal sheaths IAS, IBS,
The current flowing through IC8 is suppressed.

However, in actual power transmission lines, it is difficult to make the intervals between each junction box and each cable the same due to topography and other reasons, and because the intervals between junction boxes are different, it is difficult to completely reduce the voltage caused by each metal sheath. I can't cancel it.

Therefore, in some cases, a fairly large current flows through the metal sheath, and the sheath loss is actually quite large.

In order to suppress this sheath current, there is an idea of inserting a reactor in the middle of the cross bond wire, but when high frequency waves such as lightning surges and switching surges come, abnormally high voltage is generated in this part. Therefore, in order to suppress this, a new anti-corrosion layer protection device must be installed on both sides of the reactor, which is quite expensive.

On the other hand, as a protection circuit for the cable sheath anti-corrosion layer, the second
As shown in the figure, there is an idea to connect the arrester closely to both ends of the insulated junction box, but due to space issues on actual lines, it is not possible to lay the arrester closely to the insulated junction box, and long lead wires are required. After that, these protective devices will be installed.

For this reason, the voltage drop due to the inductance of this lead wire becomes very large (and may even make it impossible to protect the anti-corrosion layer).

The present invention has been made in view of such circumstances, and includes:
The purpose is to provide a new power cable line that can greatly reduce the circulating current flowing through the metal sheath and protect the sheath anti-corrosion layer against lightning surges and the like.

In other words, the gist of the present invention is to use a cable as a cross-bond wire with a metal sheath, attach a reactor to the outer periphery of the cable for suppressing the sheath current, and attach one core wire (hereinafter referred to as the middle wire in this specification) to one end of the cable. ) and the other core wire (
In this specification, the athleta is attached between the colored lines (5).

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be specifically described below with reference to drawings showing embodiments.

Figure 3 shows an example of a cross bond.

Cross bond is the middle line 5 of pair cable 5, 5', 5"
By connecting the color lines 52, 52', 52'' to 5L51', 51'' as shown in FIG. 3, the line 5.

The colored wire 52' of another paired cable 5' is connected to the metal sheath on one side of the insulated junction box 3 via the center wire 51 of the paired cable 5, and the colored wire of the previous paired cable 5 is connected to the other metal sheath. 52
The center line 51'' of another third pair cable 5'' is connected via.

Each pair of cables 5, 5'. A beam actuator is provided on the outside of the 5" cable to suppress the cable sheath current.

Median wires 51, 51' of each pair of cables 5, 5', 5'',
51'' and colored lines 52, 52'.

52'', an arrester 6 is provided.

Now, if a lightning surge were to enter cable 1A,
The equivalent circuit at this time is shown in FIG.

An induced voltage e is generated in the insulated junction box 3, and surge currents i are generated in the center wire 51 and color wire 52 of the paired cable 5 in opposite directions.

This surge voltage is the sum of the voltage between the terminals of the arrester 6 and the voltage drop of the paired cable 5, but the voltage between the arrester terminals is suppressed to the limit voltage, and the voltage drop of the paired cable is low because the surge impedance of the paired cable is small. value, and the voltage induced in the insulating junction box can be suppressed below a predetermined value jl.

Note that although a surge current flows through the pair cable 5, the center line 51
Since the directions of the colored lines 52 and 52 are reversed, no magnetic flux is generated outside the paired cable, and the actuator 7 attached to the outside will not operate against such surges.

(No voltage is generated in the reactor.

) Next, consider the metal sheath current at commercial frequency.

The metal sheath current can be expressed as the sum of the zero-sequence current and the circulating current, most of which is the latter, and in order to suppress the metal sheath current, it is sufficient to reduce this circulating current component.

Even when cross-bonding is performed, a circulating current flows in the actual line because the cross-bond section length and phase-to-phase distance differ from section to section, and an induced voltage Δe due to this deviation occurs in each cross-bond circuit.

The induced voltage due to the shift of A, B, and C phases is △ea.

Naturally, if △eb and △ec are the sum of these (△ea
10△eb+△ec) becomes zero.

here. The impedance of the cross bond circuit is Zo, the inductance of the reactor is L1, each cross bond current is I
Let a, Ib, and Ic.

△ea=Zo・Ia+jwL(2Ia-Ib-Ic)△
eb=Zo ・Ib+jwL(2Ia-Ic-Ia)△
ec = Zo ・Ic + jwL (2Ic - Ia - Ib), and by taking the sum of these, the sum of each current (I a + I
It can be seen that b + I c ) is zero.

Considering this, the voltage drop △e in each phase becomes △e=(Zo+j 3wL)I, and the sheath current ■ is calculated by the inductance L of the reactor.
It can be seen that it is limited by

In this embodiment, beam actors 7 are provided for all three phases, but
The same effect can be obtained even if it is provided in only two of the three phases.

The reactor 7 may have one or more primary windings.

In this specification, the medium wire and colored wire are named for convenience in order to clarify the connection relationship between the core wires of the paired cables, and do not mean any special wires. It is just an insulated core wire.

According to the present invention, the following effects are achieved.

(1) Since the sheath current can be suppressed by the reactor, sheath loss can be greatly reduced.

(2) Since a paired cable is used for the cross bond wire, the reactor (installed outside the paired cable) does not operate against surge waves, so there is no need to attach an arrester to the reactor section.

(3) Since a pair cable is used for the cross bond wire, the voltage drop in this part can be ignored, and the surge voltage of the anticorrosion layer can be suppressed to about the limit voltage of the arrester.

(4) Generally, sheath current is suppressed by a reactor or the like.

When a large current such as a ground current flows, a high voltage is generated between the reactors, and the reactor must be an expensive saturable type. However, in the circuit configuration of the present invention, the ground current is a zero-sequence component. Therefore, as in the case of surge voltage, the reactor does not operate and no voltage is generated between the reactors.

Therefore, it is not necessary to make the reactor a saturable type, and it is inexpensive.

(5) Since the arrester used in the present invention is not grounded, there is no need to provide a low resistance grounding part.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing an example of a conventional electric cable line,
Figure 2 is an explanatory diagram showing an example of the conventional arrester installation method.
FIG. 3 is an explanatory diagram showing one embodiment of the present invention, and FIG. 4 is an explanatory diagram showing a portion of an equivalent circuit of the embodiment for surge voltage. 1A: Cable A phase, 1B = Cable B phase. 1C: Cable phase C, IAS: Metal sheath A phase. IBS: Metal sheath B phase, IC8: Metal sheath C phase
2a * 2b: Ordinary junction box, 3: Insulated junction box. 4: Cross bond wire, 5: Pair cable. 51: Medium line of paired cable, 52: Color wire of paired cable, 6
:Arrester, 7:Reactor,

Claims (1)

[Claims] Two insulated junction boxes are installed in each section sandwiched between two ordinary junction boxes to which the 13-line metal sheathed single-cardiac cable is grounded. In a power cable line in which metal sheaths are cross-bonded, the metal sheath on one side of the insulated junction box 3 is connected to the other pair cable 5 via the center line 51 of the pair cable 5.
', and the metal sheath on the other side is connected to the middle wire 51'' of the other third pair cable 5'' via the color wire 52 of the previous pair cable 5, An arrester 6 is connected between each medium line and the colored wire of each of the paired cables 5, 5', and 5'', and
An electric cable line characterized in that a reactor 7 is provided on the outer periphery of the 5".