Prefabricated flexible direct current cable termination stress wimble structure
Technical field
The present invention relates to a kind of prefabricated flexible direct current cable termination stress wimble structures.
Background technology
Flexible DC power transmission is increasingly taken seriously as a kind of New type of transmission.Flexible direct current cable system is
The important component of soft straight transmission system is made of soft straight cable body and soft straight cable connector (connector and terminal).It is soft
Straight cable terminal is the key component of cable system and is easier to the link to break down, therefore restricts soft straight cable system
It unites and develops to higher voltage grade.
In cable termination design process, it is necessary to consider the electric field distribution in cable stress cone.In ac cable terminal,
Dielectric constant of the electric field distribution depending on insulating materials, it is unrelated with Temperature Distribution.In direct current cables terminating insulation, electric field distribution
Depending on resistivity distribution, and resistivity is distributed with temperature and electric field there are relation, therefore its electric field distribution situation is increasingly complex.
At present, the not no design theory and design method on soft straight cable terminal, there are no carried based on DC electric field distribution
The structure design gone out.In existing soft straight cable terminal structure design, largely apply mechanically AC terminal structure design and carry out slightly
Micro-adjustment does not propose specific design theory and design method.
The content of the invention
The present invention provides a kind of prefabricated flexible direct current to solve drawbacks described above and deficiency in the prior art
Cable termination stress wimble structure.
In order to solve the above technical problems, the present invention provides a kind of prefabricated flexible direct current cable termination stress wimble structure, bag
Reinforced insulation layer, stress cone semi-conductive layer and stress cone curve are included, wherein the stress cone semi-conductive layer is placed in direct current cables sheet
On body insulating layer, the reinforced insulation is placed on the stress cone semi-conductive layer, and the stress cone curve is the stress cone
The lower edge of semi-conductive layer, the computational methods of wherein stress cone curve comprise the following steps:
Step 1 calculates radial electric field intensity E at stress cone curve y2(y);
Wherein, ρ2(y) it is the resistivity at reinforced insulation layer y, U bears voltage for reinforced insulation layer, and R (y) is exhausted for enhancing
Unit resistance of the edge layer inner surface at stress cone curve y;
Step 2 determines the thickness of reinforced insulation layer;
Reinforced insulation layer radius RsThe radial electric field intensity E at place2(Rs) it is cable insulation maximum functional electric field strength E0's
Half, expression formula are as follows:
E2(RS)=0.5E0
With reference to the expression formula and above formula of radial electric field intensity at stress cone curve y, R is calculated to obtains, so as to which enhancing be calculated
Thickness of insulating layer Δ n=Rs- R, R are cable insulation radius;
Step 3, identified sign cone curvilinear equation;
The axial electric field strength E of any point on stress cone curvetWith the radial electric field E of the point2There are following relations:
Above formula is integrated to obtainMake EtFor constant, by radial electric field E2Expression formula is brought intoAnd several groups of coordinates (x, y) are obtained using numerical method, obtain stress cone curvilinear equation.
Wherein, in step 1, the electricalresistivityρ at reinforced insulation layer y2(y) calculating process is as follows:
At reinforced insulation layer r' with the temperature difference of cable conductor:
I.e.:
In formula, θ2It is the temperature at r' for reinforced insulation layer outer diameter, θRFor the temperature of cable insulation outer surface, θcFor electricity
Cable conductor temperature, R be cable insulation radius, ρT2For the thermal resistivity of reinforced insulation layer, ρT1For the thermal resistance system of cable insulation
Number, WcIt is lost for cable conductor;rcFor cable conductor radius;
According to resistivity formula, electricalresistivityρ at reinforced insulation layer r'2(r') expression formula is:
Wherein,ρ2,0For the resistivity of reinforced insulation layer
Coefficient;a2For the temperature coefficient of resistivity of reinforced insulation layer;γ2For the resistivity electric field coefficient of reinforced insulation layer;E2(r') it is increasing
Radial electric field intensity at strong insulating layer r', according to Ohm's law:Therefore,I should
Electric current at power cone curve y;ByWith electricalresistivityρ at reinforced insulation layer r'2(r') expression formula obtains:Bring this formula at reinforced insulation layer r' electricalresistivityρ2(r') expression formula obtains:
Wherein,
In step 1, the calculating process of unit resistance R (y) of the reinforced insulation layer inner surface at stress cone curve y is as follows:
Wherein, resistivity at reinforced insulation layer r'It is electric at cable insulation r
Resistance rate
From hot road equation:
I.e.:
According to Ohm's law:Therefore,Electric current at I stress cone curves y;ByWith electricalresistivityρ at cable insulation r1(r) expression formula obtains:This formula is brought into
Electricalresistivityρ at cable insulation r1(r) expression formula obtains:
Therefore it is as follows to obtain unit resistance R (y) expression formula of the reinforced insulation layer inner surface at stress cone curve y:
With reference to unit resistance R (y) expression formula and reinforced insulation layer y of the reinforced insulation layer inner surface at stress cone curve y
The expression formula of place's resistivity obtains radial electric field intensity E at stress cone curve y2(y) it is:
It is as follows that letter involved in foregoing calculating formula represents meaning:
θcFor cable conductor temperature, θRFor the temperature of cable insulation outer surface, θ1For the temperature at cable insulation outer diameter r
Degree, θ2For the temperature at reinforced insulation layer outer diameter r', R is cable insulation radius, WcIt is lost for cable conductor;rcIt is led for cable
Body radius;ρT2For the thermal resistivity of reinforced insulation layer, ρT1For the thermal resistivity of cable insulation, ρ1,0For the electricity of cable insulation
Hinder rate coefficient, ρ2,0For the resistivity coefficient of reinforced insulation layer, a1For cable insulation temperature coefficient of resistivity, a2For reinforced insulation
The temperature coefficient of resistivity of layer, γ1For the resistivity electric field coefficient of cable insulation, γ2For the resistivity electric field of reinforced insulation layer
Coefficient, E1(r) it is the radial electric field intensity at cable insulation radius r, E2(r') it is the radial direction electricity at reinforced insulation layer radius r'
Field intensity;
The advantageous effects that the present invention is reached:1. on the basis of considering temperature, electric field factor to resistivity effects,
It proposes the electric field distribution in the soft straight cable terminating insulation of prefabricated, provides fundamental basis for soft straight cable stud connector design;2. it carries
A kind of soft straight cable terminal reinforced insulation layer thickness computational methods of prefabricated are supplied, it is ensured that cable insulation-reinforced insulation stratum boundary
Face electric field is in the reasonable scope;3. devising rational stress cone-shaped, solve soft straight cable terminal potential line concentration phenomenon,
And ensure entire stress cone electric fields uniform;4. meeting requirement on electric performance of the entire soft straight cable system to terminal, ensure soft straight electricity
The long-term safety of cable system is reliable.
Specific embodiment
With reference to specific embodiment, the invention will be further described, and following embodiment is only used for clearly illustrating
Technical scheme, and be not intended to limit the protection scope of the present invention and limit the scope of the invention.
The present invention provides a kind of prefabricated flexible direct current cable termination stress wimble structure, including reinforced insulation layer, stress cone
Semi-conductive layer and stress cone curve, wherein the stress cone semi-conductive layer is placed on direct current cables insulating layer, the reinforced insulation
It is placed on the stress cone semi-conductive layer, the stress cone curve is the lower edge of the stress cone semi-conductive layer, wherein should
The computational methods of power cone curve comprise the following steps:
Step 1 calculates radial electric field intensity E at stress cone curve y2(y);
Wherein, ρ2(y) it is the resistivity at reinforced insulation layer y, U bears voltage for reinforced insulation layer, and R (y) is exhausted for enhancing
Unit resistance of the edge layer inner surface at stress cone curve y;
Electricalresistivityρ at one, reinforced insulation layer y2(y) calculating process is as follows:
At reinforced insulation layer r' with the temperature difference of cable conductor:
I.e.:
According to resistivity formula, electricalresistivityρ at reinforced insulation layer r'2(r') expression formula is:
According to Ohm's law:Therefore,Electric current at I stress cone curves y;ByWith electricalresistivityρ at reinforced insulation layer r'2(r') expression formula obtains:It will
This formula brings electricalresistivityρ at reinforced insulation layer r' into2(r') expression formula obtains:
Two, the calculating process of unit resistance R (y) of the reinforced insulation layer inner surface at stress cone curve y is as follows:
Wherein, resistivity at reinforced insulation layer r'It is electric at cable insulation r
Resistance rate
From hot road equation:
I.e.:
According to Ohm's law:Therefore,Electric current at I stress cone curves y;ByWith electricalresistivityρ at cable insulation r1(r) expression formula obtains:By this formula band
Enter electricalresistivityρ at cable insulation r1(r) expression formula obtains:
Therefore it is as follows to obtain unit resistance R (y) expression formula of the reinforced insulation layer inner surface at stress cone curve y:
With reference to unit resistance R (y) expression formula and reinforced insulation layer y of the reinforced insulation layer inner surface at stress cone curve y
The expression formula of place's resistivity obtains radial electric field intensity E at stress cone curve y2(y) it is:
It is as follows that letter involved in foregoing calculating formula represents meaning:
θcFor cable conductor temperature, θRFor the temperature of cable insulation outer surface, θ1For the temperature at cable insulation outer diameter r
Degree, θ2For the temperature at reinforced insulation layer outer diameter r', R is cable insulation radius, WcIt is lost for cable conductor;rcIt is led for cable
Body radius;ρT2For the thermal resistivity of reinforced insulation layer, ρT1For the thermal resistivity of cable insulation, ρ1,0For the electricity of cable insulation
Hinder rate coefficient, ρ2,0For the resistivity coefficient of reinforced insulation layer, a1For cable insulation temperature coefficient of resistivity, a2For reinforced insulation
The temperature coefficient of resistivity of layer, γ1For the resistivity electric field coefficient of cable insulation, γ2For the resistivity electric field of reinforced insulation layer
Coefficient, E1(r) it is the radial electric field intensity at cable insulation radius r, E2(r') it is the radial direction electricity at reinforced insulation layer radius r'
Field intensity;
Step 2 determines the thickness of reinforced insulation layer;
Reinforced insulation layer radius RsThe radial electric field intensity E at place2(Rs) it is cable insulation maximum functional electric field strength E0's
Half, expression formula are as follows:
E2(RS)=0.5E0
With reference to the expression formula and above formula of radial electric field intensity at stress cone curve y, R is calculated to obtains, so as to which enhancing be calculated
Thickness of insulating layer Δ n=Rs- R, R are cable insulation radius;
Step 3, identified sign cone curvilinear equation;
The axial electric field strength E of any point on stress cone curvetWith the radial electric field E of the point2There are following relations:
Above formula is integrated to obtainMake EtFor constant, by radial electric field E2Expression formula is brought intoAnd several groups of coordinates (x, y) are obtained using numerical method, obtain stress cone curvilinear equation.
Embodiment one
Using the soft straight cable terminal of rated voltage ± 320kV prefabricateds.
Radial electric field intensity E at one, stress cone curve y2(y) calculate
For the soft straight cable terminal of ± 320kV prefabricateds, U=320kV;ρ1,0=ρ2,0=1016Ω.m;a1=0.06 DEG C-1,
a2=0.05 DEG C-1;θc=90 DEG C, wc=68W;ρT1=3.5K.m/W, ρT2=3.3K.m/W;rc=26.5mm, R=50.5mm;
γ1=2.2, γ2=1.69, bring above-mentioned data at stress cone curve y radial electric field intensity E2(y) calculation formula:
Two, reinforced insulation layer thickness
Soft straight cable body insulation thickness R=24mm, maximum field E0=18kV/mm, then E (Rs)=9kV/mm.
E (R are taken to leave enough safety marginss)=7kV/mm, which substitutes into formula above formula, can obtain RS=71.5mm can be enhanced
Insulation thickness Δ n=RS- R=21mm.
Three, identified sign cone curvilinear equation
It is computed that several groups of coordinates (x, y) on the soft straight cable terminal stress cone curve of ± 320kV prefabricateds can be obtained, respectively
It is:(0,50.5), (11.9,51.5), (23.4,52.5), (34.5,53.5), (45.2,54.5), (55.6,55.5),
(65.6,56.5), (75.4,57.5), (84.9,58.5), (94.1,59.5), (103.1,60.5), (111.8,61.5),
(120.3,62.5), (128.6,63.5), (136.7,64.5), (144.6,65.5), (152.3,66.5), (159.9,
67.5), (167.3,68.5), (174.6,69.5), (181.7,70.5), (188.7,71.5) finally obtain stress cone shaped form
Shape.
Embodiment 2
Using the soft straight cable terminal of rated voltage ± 200kV prefabricateds.
Radial electric field intensity E at one, stress cone curve y2(y) calculate
For the soft straight cable terminal of ± 200kV prefabricateds, U=200kV;ρ1,0=ρ2,0=1016Ω.m;a1=0.06 DEG C-1,
a2=0.05 DEG C-1;θc=90 DEG C, wc=66W;ρT1=3.5K.m/W, ρT2=3.3K.m/W;rc=20.4mm, R=36.4mm;
γ1=2.2, γ2=1.69, bring above-mentioned data at stress cone curve y radial electric field intensity E2(y) calculation formula:
Two, reinforced insulation layer thickness
Soft straight cable body insulation thickness R=15mm, maximum field E0=20kV/mm, then E (Rs)=10kV/mm.
E (R are taken to leave enough safety marginss)=7kV/mm, which substitutes into formula (22), can obtain RS=46.4mm can be enhanced
Insulation thickness Δ n=RS- R=10mm.
Three, identified sign cone curvilinear equation
It is computed that several groups of coordinates (x, y) on the soft straight cable terminal stress cone curve of ± 200kV prefabricateds can be obtained, respectively
It is:(0,36.4), (12.2,37.4), (23.7,38.4), (34.6,39.4), (44.9,40.4), (54.7,41.4), (64,
42.4), (72.9,43.4), (81.4,44.4), (89.6,45.4), (97.6,46.4) finally obtain stress cone curve shape.
The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For member, without departing from the technical principles of the invention, several improvement and deformation can also be made, these are improved and deformation
Also it should be regarded as protection scope of the present invention.