CN105958422A - Novel power transmission overhead ground wire lightning protection grounding method - Google Patents

Abstract

The invention relates to the lightning protection grounding field and particularly relates to a novel power transmission overhead ground wire lightning protection grounding method. Double overhead ground wires of a power transmission line comprise a first overhead ground wire and a second overhead ground wire, multiple poles are arranged on the power transmission line, according to the pole arrangement order, the double overhead ground wires realize transposition at even-number poles of the power transmission line, and the double overhead ground wires and odd-number poles are in direct grounding connection at the odd-number poles of the power transmission line. According to the method, a grounding mode of the overhead ground wires is changed, energy saving and consumption reduction of the overhead ground wires are facilitated, a grounding mode of even-number segment transposition and odd-number segment grounding is employed, circulation and damage are reduced, not only can a metal tool be prevented from heating, but also influence on a shunting coefficient of the ground wire is not great.

Description

A kind of power transmission overhead ground wire Novel lightning-proof earthing method

Technical field

Lightning protection field of the present invention, is particularly a kind of power transmission overhead ground wire Novel lightning-proof earthing method.

Background technology

Along with China's expanding economy, the proposition of global energy the Internet concept, extra-high voltage prepares construction, electric power corridor growing tension in a large number；On the other hand, Large Clean Energy Base and the construction in power station, huge edema due to wind pathogen, it is desirable to the transmission line capability of circuit strengthens day by day.When ultra-high-tension power transmission line is properly functioning, can produce strong-electromagnetic field around wire, can produce electromagnetism and Electrostatic Field Coupling between ground wire and wire, owing to ground wire is the most unequal to the distance of each phase conductor, the most sympathetic between them has difference.Therefore, on ground wire, sensing produces vertical interference and the electrostatic induction voltage of distribution along the line.

OPGW has the function of communication port and lightning conducter concurrently, is the most widely applied in ultra-high-tension power transmission line, and UHV transmission line still uses OPGW as leading communications means.On earthing mode, in engineering, OPGW uses the mode by base ground connection substantially at present. the common lightning conducter then modes using graded insulation, one point earth more.Earthing mode by base ground connection can make OPGW circulation loss occur, and energy-saving and cost-reducing to transmission line of electricity brings adverse effect；Meanwhile, also OPGW can be made increased by lightning strike probability because of the difference of lightning conducter common on same tower and OPGW earthing mode, cause the problem that disconnected stock damages.Therefore, the earthing mode researching and analysing the OPGW optical cable with extra high voltage line construction and the impact brought thereof, inquire into rational earthing mode and monitoring grounding situation is necessary.OPGW needs consider short circuit thermal capacity and bear the problems of mechanical strength such as ice, wind load in use, may also suffer from thunderbolt simultaneously, these aspects have substantial amounts of design and operation experience and lessons both at home and abroad, certainly there are strands break problem, reason and countermeasure etc. also in exploratory stage, the OPGW many places such as part province in some problem.

Summary of the invention

The technical problem to be solved is to provide a kind of power transmission overhead ground wire Novel lightning-proof earthing method, solves relay protection of transmission line double route dual pathways requirement, with the double aerial earth wire of transmission line of electricity parallel lay-up.When properly functioning, due to electromagnetic induction and electrostatic induction reason, the problem that double aerial earth wires all can produce induced voltage.

The present invention is achieved in that

A kind of power transmission overhead ground wire Novel lightning-proof earthing method, double aerial earth wires for transmission line of electricity include the first aerial earth wire and the second aerial earth wire, arrange multiple shaft tower, wherein on transmission line of electricity, according to the order of shaft tower arrangement, double aerial earth wires replace at the even number shaft tower of transmission line of electricity；Double aerial earth wires, at the odd number shaft tower of transmission line of electricity, are all directly connected to ground connection with shaft tower.

Further, double aerial earth wires replace at the even number shaft tower of transmission line of electricity, be that the insulator by belt discharge gap insulate with shaft tower, the first trolley wire is shifted to the second aerial earth wire, second aerial earth wire is connected to the first aerial earth wire, at even number shaft tower, aerial earth wire is replaced.

The present invention compared with prior art, has the beneficial effects that:

The even number tower of aerial earth wire of the present invention is insulated with tower by the insulator in belt discharge gap, and is connected by wire jumper, replaces aerial earth wire at even number shaft tower；Double aerial earth wires are directly connected to ground connection at the odd number of transmission line of electricity.Owing to double aerial earth wires odd number tower at two ends is all directly connected with shaft tower, time the most properly functioning, current loop is may be constructed between first aerial earth wire and the second aerial earth wire, and the earth circulation loop between the first aerial earth wire, the second aerial earth wire and the earth, can be respectively constituted, the voltage of transposition ground wire the last period is the biggest with the phase difference of voltage of latter one section of transposition, total induced voltage is neutralized, reduce electromagnetic induction voltage and the electric current of double aerial earth wire, the effect reducing electric energy loss can be played.

Use the energy-saving and cost-reducing of the earthing mode changing aerial earth wire, beneficially aerial earth wire.Use odd number section ground connection, the earthing mode of even number section transposition, reached reduction circulation and damage, not only prevent the heating of gold utensil, and the diverting coefficient impact of ground wire is little.After using odd number section ground connection, although span increases, but the impact on diverting coefficient is the least, will not significantly increase step voltage, it is ensured that personal safety.After using odd number section ground connection, the transposition of even number section, the electromagnetic induction voltage of the earth circulation loop of aerial earth wire is substantially reduced.

Accompanying drawing explanation

Fig. 1 is double aerial earth wire circulation equivalent circuit diagrams；

Fig. 2 is odd number section ground connection, even number section transposition schematic diagram；

Fig. 3 is odd number section ground connection, even number section transposition the earth circulation loop diagram.

Detailed description of the invention

In order to make the purpose of the present invention, technical scheme and advantage clearer, below in conjunction with embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.

First faradic current, the voltage of aerial earth wire is analyzed, then the earthing mode of odd number section ground connection, the transposition of even number section is analyzed, finally by analyzing the reasonable of shunting Verification method and effectiveness.

Induced voltage in aerial earth wire: time properly functioning, the aerial earth wire self-impedance with the earth as loop can be expressed as:

$Z_1=R+0.05+j0.145\lg \frac{D_0}{r}$

Wherein: Z₁Being the self-impedance of the first aerial earth wire and ground return circuit, R is the resistance of aerial earth wire, and r is the effective radius of aerial earth wire, D₀The degree of depth of equal value for earth current；

Mutual impedance between aerial earth wire and transmission line of electricity individual event wire is:

Wherein: Z₁₂It is the mutual inductive impedance between the first aerial earth wire and transmission line of electricity single-phase transmission line, d₁₂It it is the distance between the first aerial earth wire and transmission line of electricity single-phase transmission line.Under normal circumstances, transmission line of electricity a, b, c three-phase current symmetrical balance, it may be assumed that

I_a+I_b+I_c=0

Time properly functioning, the induced voltage on aerial earth wire is aerial earth wire to a, the induced voltage sum of b, c three-phase conducting wire:

$E_t=(0.05+j0.145\lg \frac{D_0}{d_{1a}})I_a+(0.05+j0.145\lg \frac{D_0}{d_{1b}})I_b+(0.05+j0.145\lg \frac{D_0}{d_{1c}})I_c$

In formula: E₁For aerial earth wire electromagnetic induction voltage time properly functioning, I_a、I_b、I_cFor the load current of a, b, c three-phase conducting wire, d_1a, d_2a, d_1cFor the distance between aerial earth wire to a, b, c three-phase conducting wire.It can be seen that the three-phase equilibrium load current that the electromagnetic induction voltage of aerial earth wire flows through to wire time properly functioning is directly proportional, after aerial earth wire construction and installation, the biggest with the load current that transmission line of electricity flows through, the electromagnetic induction voltage on aerial earth wire is the biggest.

Power transmission line overhead ground wire uses double aerial earth wire, to increase aerial earth wire protection domain, reduces shielding angle, reduces the risk of shielding failure of thunderbolt.The generally symmetrical layout of double aerial earth wires, the first aerial earth wire is near a phase of transmission line of electricity, and the second aerial earth wire then near the c phase of transmission line of electricity, can be approximately considered:

d_1a=d_2c d_1b=d_2b d_1c=d_2c

In the most double aerial earth wires, the electromagnetic induction voltage of the second aerial earth wire can be expressed as:

$E_2=j0.145I_a\{a\lg \frac{d_{2a}}{d_{2b}}+a2\lg \frac{d_{2a}}{d_{2c}}\}$

Wherein E₂It is the electromagnetic induction voltage of the second aerial earth wire 2, d_2a, d_2b, d_2cIt is that the second aerial earth wire is to a, the distance between b, c three-phase conducting wire.

Faradic current referring again to seeing aerial earth wire: when all using by base earthing mode for double aerial earth wires, double aerial earth wires are all directly connected with electric power line pole tower, due to the first aerial earth wire, the induced voltage E of the second aerial earth wire₁With E₂Size, direction all differ, and therefore, will produce circulation between the first aerial earth wire and the second aerial earth wire, its current loop as shown in Figure 1: induced voltage produced by aerial earth wire loop is superposed to:

$E_h=\frac{1}{2}(E_1-E_2)=\frac{1}{2}j0.145I_a\{a\lg \frac{d_{1a}}{d_{1c}}+2a^2\lg \frac{d_{1a}}{d_{1c}}\}{I}_h=\frac{E_h}{Z_h}$

Wherein in Fig. 1, Z_h1 Z_h2Represent impedance and the impedance of the second aerial earth wire, the Z of the first aerial earth wire respectively_hRepresent aerial earth wire impedance.

Also inciting somebody to action by base ground connection of aerial earth wire produces the earth circulation, independently can calculate as two components, and by electric energy loss superposition produced by two current weights, voltages, double aerial earth wire can be obtained and all use the electric energy loss of aerial earth wire under main frame direct grounding way.

If only wall scroll ground wire is by base ground connection in double aerial earth wires, owing to an aerial earth wire therein insulate with electric power line pole tower, thus without producing Circulation Components between two aerial earth wires.Only it is directly grounded in aerial earth wire generation the earth Circulation Components by base, in by the directly grounded aerial earth wire of base, only produces the earth Circulation Components I_d, the electric energy loss of aerial earth wire is mainly produced by the earth circulation.

And odd number section ground connection, even number section transposition earthing mode: UHV transmission line typically uses double aerial earth wire, article one, aerial earth wire uses by base direct grounding way, another strip adoption graded insulation single-point grounding mode, the electric energy loss of aerial earth wire is mainly by using the loss by base direct grounding way, but the aerial earth wire of another graded insulation single-point grounding mode is difficult to adjust due to the distance of the insulator in belt discharge gap, when properly functioning, may puncture for a long time when meeting the excessive discharging gap of electric current, there is potential safety hazard, and when lightning hazards occurs, there is again power frequency continued flow to be difficult to cut off, power-off protection positive definite is difficult to coordinate, during circuit generation individual event earth fault, the deficiencies such as good shunting action can not be played.When double aerial earth wires all use graded insulation single-point grounding mode, the electric energy loss of generation is minimum, but the problem that the insulator distance equally existing belt discharge gap is difficult to positive definite.The problem existed for above aerial earth wire earthing mode, the earthing mode of aerial earth wire is improved by this patent, propose aerial earth wire and insulated with shaft tower by the insulator in belt discharge gap at the even number shaft tower of transmission line of electricity, and by connecting jumping figure, at even number shaft tower, aerial earth wire is replaced；Odd number section ground connection refers to, double aerial earth wires, at the odd number shaft tower of transmission line of electricity, are all directly connected to ground connection with shaft tower.Aerial earth wire technical ground connection, schematic diagram such as Fig. 2 of even number section transposition.

As in figure 2 it is shown, properly functioning time, the first aerial earth wire and the second aerial earth wire are respectively close to a phase of transmission line of electricity and c phase, and the electromagnetic induction voltage phase angle difference of generation is the biggest.Therefore, after using the transposition of even number section, the voltage of 1 transposition ground wire the last period in two aerial earth wires is very big with the phase difference of voltage of latter one section of transposition, and total induced voltage is neutralized, reduce electromagnetic induction voltage and the electric current of double aerial earth wire, the effect reducing electric energy loss can be played.

When double aerial earth wires use odd number section ground connection, the transposition of even number section, owing to double aerial earth wires technology tower at two ends is all directly connected with shaft tower, time the most properly functioning, current loop is may be constructed between first aerial earth wire and the second aerial earth wire, and the earth circulation loop between the first aerial earth wire, the second aerial earth wire and the earth, can be respectively constituted, after odd number section ground connection, the transposition of even number section, the equivalent current loop in aerial earth wire and the earth circulation loop is as shown in Figure 3.Can be seen by Fig. 3, the electromagnetic induction voltage in aerial earth wire the earth circulation loop can be expressed as:

$E_d=\frac{1}{2}(E_1+E_2)=\frac{1}{2}\[j0.145I_a(a\lg \frac{d_{1a}}{d_{1b}}+a^2\lg \frac{d_{1a}}{d_{1c}})\]+\[j0.145I_a(a\lg \frac{d_{1c}}{d_{1b}}+a2\lg \frac{d_{1c}}{d_{1a}})\]=\frac{1}{2}j0.145I_{a}a\lg \frac{d_{1a}{d}_{1c}}{d_{1b}^2}$

Comparing with the inductive voltage value being previously obtained, after using odd number section ground connection, the transposition of even number section, the electromagnetic induction voltage of the earth circulation loop of aerial earth wire is substantially reduced.Z in Fig. 3_d1It is the self-impedance of the first aerial earth wire, Z_d2It is the self-impedance of the second aerial earth wire, Z_r1It is first pole tower ground resistance, Z₀Represent ground return circuit self-impedance, Z_r2Represent second pole tower ground resistance.

Have a talk the most again the earthing mode impact on diverting coefficient improved: in power plant, transformer station, the earthing mode of transformer neutral point is divided into two kinds: a kind of for neutral-point solid ground, another kind of for isolated neutral or through grounding through arc, earthing mode in ultra-high voltage transformer station station, generally individually use neutral-point solid ground mode, to meet the Insulation Coordination requirement of equipment, it is ensured that the safe and reliable operation of power equipment.Along with the continuous lifting of power system capacity, substation grounding short circuit current level improves constantly, and earth-fault current during fault constantly increases, and brings following harmful effect to power system:

(1) electric grid investment expense increases: the increase of short circuit current, require that the level that chopper cut-offs short circuit current when breaking down increases, make the rated current of existing electrical equipment, electric insulation etc. can not meet requirement simultaneously, therefore when carrying out Study on Power Grid Planning and transformation, designer has to select high dielectric level, high drop-out current, the electrical equipment of high rated capacity, causes cost of equipment to be greatly improved.

(2) safety of electrical equipment is threatened: short circuit current, through transformer neutral point ground connection, flows into grounding net of transformer substation.The increase of short circuit current causes the place of transformer station for raising, and threatens the turn-to-turn insulation of transformator.The rising that place is can produce bigger touch voltage and step voltage, directly jeopardizes the safe and stable operation of power transformation station equipment, even entail dangers to personal safety.

(3) harm that communication line is produced；UHV transmission line, during the asymmetric ground short circuit of OPGW, short circuit current can induce the biggest electromotive force on adjacent lines, and communication line is produced interference.

When being short-circuited in Substation Station, short circuit current is provided by the power supply of the infinite far-end in transformator both sides, and not only from the power supply of short circuit end, according to Kirchhoff's law, short circuit current flows back to the power supply of both sides the most at last.Therefore, short circuit current is classified into two parts: a part of short circuit current directly passes through earthed system by the power supply greatly flowing to infinite far-end；If aerial earth wire uses by base direct grounding way, due to transformer neutral point and aerial earth wire, to be all connected to substation grounding online, another part short circuit current flows out grounded screen by the aerial earth wire of transformer neutral point and transmission line of electricity, the short circuit current of power supply is flowed back to by aerial earth wire, by base through tower grounding, having again portion of electrical current and flow to the earth by tower grounding system, remaining electric current flows back to power supply by aerial earth wire.

When transformer station is short-circuited, a short circuit current part is to flow into the earth by aerial earth wire through electric power line pole tower, and therefore, the earthing mode of aerial earth wire is different, on diverting coefficient impact difference.Employing is directly grounded every by base, short circuit current directly flows into the earth through transmission line of electricity, in the case of the impedance ground of the impedance ground of transformer station, the material of aerial earth wire and model, electric power line pole tower is certain, the diverting coefficient of this earthing mode is maximum, in transformer station to enter ground short circuit electric current minimum, step voltage and contact voltage are the lowest, and safety is the highest.

Use the mode of graded insulation single-point grounding, when transformer station is short-circuited, the insulator breakdown in belt discharge gap, constitutes the path of short circuit current, but, if the distance positive definite of discharging gap is improper, cannot may puncture by discharging gap when being short-circuited fault, now aerial earth wire can not constitute path with the earth, it is impossible to plays shunting action, therefore, under graded insulation, single-point grounding mode, the clearance distance of charged gap insulator is adjusted and can aerial earth wire be played shunting action had impact.

Aerial earth wire odd number section ground connection, the earthing mode of even number section transposition, owing to ground wire insulate with ground wire at transmission line of electricity even number shaft tower, during the fault that is short-circuited, the path of short circuit current can only flow into the earth via the technology shaft tower of transmission line of electricity, being equivalent to increase the span between each tower grounding of aerial earth wire, the size of span have impact on the equiva lent impedance of aerial earth wire.The loop method of analysis based on phase component can be used, calculate the diverting coefficient of aerial earth wire under different span, it can be seen that, span is the least, and the diverting coefficient of aerial earth wire is the biggest, when this diminishes mainly due to span, total equiva lent impedance of ground wire reduces, and therefore the shunting of aerial earth wire increases.When span > 400 time, diverting coefficient the most no longer changes.500kV transmission line of electricity span is relatively big, and therefore, after using odd number section ground connection, although span increases, but the impact on diverting coefficient is the least, will not significantly increase step voltage, it is ensured that personal safety.

This patent utilizes aerial earth wire respectively close to the A phase of transmission line of electricity and C phase, and the induced voltage phase angle difference on ground wire is very big, so proposing aerial earth wire odd number section ground connection, the earthing mode of even number section transposition.After improving earthing mode, induced voltage and faradic current when aerial earth wire is properly functioning are analyzed, and can effectively reduce the energy-saving and cost-reducing of the induced voltage on aerial earth wire and faradic current, beneficially aerial earth wire.

The change of aerial earth wire earthing mode, the span between two earth points is caused to change, by the influence factor of aerial earth wire diverting coefficient is analyzed, whether the change of research aerial earth wire earthing mode can produce impact to diverting coefficient, the span change that ground wire grounded mode causes, impact on aerial earth wire diverting coefficient is the least, and the size impact that transformer station enters the distribution of ground short circuit electric current, step voltage and basic voltage is little.In the case of not affecting aerial earth wire shunting, reduce the electric energy loss on aerial earth wire, decrease the potential safety hazard of gold utensil heating.

The foregoing is only presently preferred embodiments of the present invention, not in order to limit the present invention, all any amendment, equivalent and improvement etc. made within the spirit and principles in the present invention, should be included within the scope of the present invention.

Claims (2)

1. a power transmission overhead ground wire Novel lightning-proof earthing method, it is characterised in that double for transmission line of electricity Aerial earth wire includes the first aerial earth wire and the second aerial earth wire, arranges multiple shaft tower on transmission line of electricity, its In, according to the order of shaft tower arrangement, double aerial earth wires replace at the even number shaft tower of transmission line of electricity；Double framves Vacant lot line, at the odd number shaft tower of transmission line of electricity, is all directly connected to ground connection with shaft tower.

2. according to the power transmission overhead ground wire Novel lightning-proof earthing method described in claim 1, it is characterised in that Double aerial earth wires replace at the even number shaft tower of transmission line of electricity, are the insulator by belt discharge gap and bar Tower insulate, and the first trolley wire is shifted to the second aerial earth wire, the second aerial earth wire is connected to first and makes somebody a mere figurehead Ground wire, replaces to aerial earth wire at even number shaft tower.