CN113469494B - Mountain fire-induced line fault risk assessment method - Google Patents
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Abstract
The invention discloses a mountain fire-induced line fault risk assessment method, which comprises the following steps: step S1: acquiring line information, forest fire information, environment information and power grid state information; step S2: calculating a correction coefficient of breakdown voltage according to mountain fire information and environment information: step S3: calculating the line breakdown voltage under the condition of mountain fire, and evaluating the probability of tripping the transmission line caused by the relative ground breakdown of the line and the probability of tripping the transmission line caused by the inter-phase breakdown of the line; step S4: calculating the probability of tripping of the transmission line under the condition of mountain fire; step S5: and carrying out quantitative analysis on the severity degree of the influence of the line tripping under the condition of the mountain fire on the power grid, and evaluating the risk of line faults caused by the mountain fire. The invention considers the differences of the design elevation, the pole tower height, the line sag and the mountain fire occurrence place of the lines with different voltage grades, introduces the temperature, the conductivity and the ash particles to correct the breakdown voltage, and has comprehensiveness and universality.
Description
Technical Field
The invention belongs to the technical field of risk assessment and management and control of power systems, and particularly relates to a forest fire-induced line fault risk assessment method.
Background
In recent years, global extreme climate change has led to a significant increase in disaster events, which frequently occur. With the economic development, the load and the power grid of China are continuously increased and expanded, the power transmission lines with different capacities, different grades and different transmission distances are continuously put into use, the power transmission line corridor inevitably extends to a mountain fire area with a plurality of mountain fire disasters, and the problem of mountain fire disasters is also more remarkable.
The high temperature generated by mountain fire easily causes the thermal dissociation of air molecules, generates a large amount of charged particles, and increases the conductivity of air. Charged particles continuously develop upwards along with high-temperature airflow and smoke, so that the insulation performance of air gaps around the wires is reduced; on the other hand, the particles in the smoke dust are polarized by the electric field, and tend to be arranged into impurity 'bridges' along the direction of the electric field, so that the conductivity of air is increased; second, the flame itself has some conductivity, and when the insulating gap is covered by the flame, a conductive path may be established directly in the flame to cause discharge. By combining the reasons, the forest fire is easy to cause damage to the external insulation of the transmission line to cause discharge and trip. The damage of the insulation gap caused by high temperature can last for a long time, and reclosing after tripping is difficult to succeed. On the other hand, the wire, the pole tower, the hardware fitting and the insulator can be burnt and deformed due to the combustion of the forest fire, and various performances are lost to different degrees.
In winter and spring mountain fires, accidents of the mountain fires causing tripping of the transmission line occur more or less annually, and reclosing fails in most cases. The mountain fire spreading area is wide, the burst time is dense, the chained tripping faults of a plurality of lines in the area can be caused, the impact on the power grid can influence the safe and stable operation of the power grid, the unbalance of the power grid structure is caused, the power supply reliability is reduced, the interruption of the transmission of the large-scale lines is even caused, the sudden power failure accident occurs in the people and the area, and the normal operation of the power system is threatened.
Currently, the risk assessment of mountain fire power grid faults is still in a theoretical research stage, the influence factors of air gap breakdown under the mountain fire condition and the expression method thereof are still not very clear, how the air gap breakdown voltage is corrected, how operation and maintenance personnel carry out emergency treatment, how the power grid mountain fire is prevented and treated, and the probability of fault risk and the result loss are reduced, so that deep research is still needed.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the mountain fire-induced line fault risk assessment method, so that the difference of mountain fire disasters on different lines and the severity of the influence consequences on the power grid are obtained, and an effective reference is provided for targeted disaster prevention deployment of power system operators.
In order to solve the technical problems, the invention adopts the following technical scheme:
a mountain fire-induced line fault risk assessment method comprises the following steps:
step S1: acquiring line information, forest fire information, environment information and power grid state information;
step S2: calculating a correction coefficient of breakdown voltage according to the mountain fire information and the environment information acquired in the step S1:
step S3: according to the line information, calculating the line breakdown voltage under the condition of mountain fire, and evaluating the probability of tripping the transmission line caused by the relative breakdown of the line and the probability of tripping the transmission line caused by the inter-phase breakdown of the line;
step S4: calculating the probability of tripping of the power transmission line under the condition of mountain fire by the probability of tripping of the power transmission line caused by the relative earth breakdown of the line and the probability of phase-to-phase breakdown of the power transmission line caused by the phase-to-phase breakdown of the line;
step S5: according to the power grid state information, the importance and the influence degree of the line are considered, the severity degree of the line tripping influence on the power grid under the condition of the mountain fire is quantitatively analyzed, and the risk of the line fault caused by the mountain fire is estimated.
Preferably, the mountain fire information comprises mountain fire temperature, flame height and smoke concentration; the line information comprises actual running voltage, line-to-ground distance and line-to-line distance; the environment information comprises wind speed, air temperature, air pressure, combustible type, height and distribution; the power grid state information comprises a grid structure, tide distribution, power supply access capacity and positions.
Preferably, step S2 comprises the steps of:
step 2.1, calculating an atmospheric correction coefficient:
introducing an atmospheric correction coefficient K for air gap insulation strength reduction caused by temperature rise t ：
K t ＝K d K h
Wherein K is d K is the air density correction coefficient h Is an air humidity correction coefficient, and has:
where delta is the relative air density,the values of the indexes m, W and K come from the national standard GB/T16927.1-1997, p and p 0 The air pressures under the condition of mountain fire and under the condition of standard reference atmosphere are respectively t and t 0 The temperatures under the forest fire condition and the standard reference atmospheric condition are respectively;
step 2.2, calculating a particle correction factor:
introducing a particle correction factor K for air gap insulation strength reduction caused by carbonized small particles and ash smoke generated by combustion P ：
Wherein R is smoke concentration, r=0% indicates no impurity in the air gap, and r=100% indicates that the dense smoke fills the entire gap.
Preferably, the step S includes 3 steps of:
step 3.1, correcting the relative ground breakdown voltage and the interphase breakdown voltage of the circuit:
according to the voltage level of the circuit, the line-to-ground distance h of the typical circuit with different voltage levels is obtained by referring to the design rules l As the line height of the mountain fire place; obtaining the combustible material height h of the mountain fire area according to the environmental information of the line corridor r Thereby obtaining the relative air gap length H=h of the line l -h r ；
Under the condition of mountain fire, the air gap of the circuit is divided into a flame zone and a non-flame zone, the relative breakdown voltage of the circuit is the sum of the breakdown voltage of the air gap of the flame zone and the breakdown voltage of the air gap of the non-flame zone, the insulation strength of the air gap of the flame zone is affected by the combined action of temperature, carbonized small particles and ash smoke, and the insulation strength of the air gap of the non-flame zone is affected by the ash smoke, so that the breakdown voltage of the air gap of the circuit can be corrected as follows:
wherein the first term is flame zone gasGap breakdown voltage correction value, the second term is the gap breakdown voltage correction value of a non-flame area, U is line power frequency breakdown voltage under a mountain fire condition, U 0 The line power frequency breakdown voltage is the line power frequency breakdown voltage under the standard atmospheric condition; h is mountain fire height, H is air gap length, K p1 、K p2 Particle correction factors of the flame zone and the non-flame zone respectively, and the smoke concentration data of the flame zone and the non-flame zone respectively are used for controlling the particle correction factorsCalculating to obtain;
for the air gap between the conducting wire of the power transmission line and the ground, the mountain fire height is lower, namely h r +h<h l When the flame zone and the non-flame zone are needed to be considered comprehensively, the breakdown voltage of the line to the ground air gap is
For the air gap between the conductor and the ground of the power transmission line, if the mountain fire is close to or even envelops the conductor, the air gap is h r +h≥h l When the flame area is considered, the breakdown voltage of the line to the ground air gap is
U＝K t K p1 U 0
For the air gap between the wires, the fire is not close to the wires, namely r +h<h l I.e. consider the air gap to be entirely in the non-flame region, the breakdown voltage of the inter-air gap is degraded to
U＝K p2 U 0
For the air gap between the wires, if the mountain fire approaches or even envelops the wires, the air gap is h r +h≥h l An inter-phase air gap breakdown voltage of
U＝K t K p1 U 0 ；
Step 3.2, calculating the line relative ground breakdown probability and the line inter-phase breakdown probability:
under the condition of mountain fire, the line breakdown voltage is considered to accord with normal distribution, and the breakdown probability density is expressed as:
wherein U is line voltage when mountain fire occurs; mean mu is equal to U 50％ The power frequency breakdown voltage is 50%; sigma= zU 50％ The method comprises the steps of carrying out a first treatment on the surface of the z is a variation coefficient, and the value is between 2% and 8%.
Preferably, under the condition of mountain fire, the variation coefficient z is taken to be 4%, and the line breakdown probability is
Preferably, the step S4 classifies the fault types of the power transmission line tripping under the condition of mountain fire into two types of relative ground breakdown tripping and inter-phase breakdown tripping, combines the actual power transmission line voltage grade and the fault types, and calculates the probability of the power transmission line tripping under the condition of mountain fire according to the proportion distribution of the relative ground breakdown and the inter-phase breakdown in the historical statistical data of the power transmission line voltage grade
P l (U)＝λ g ·P g (U)+λ p ·P p (U)
λ g The relative ground breakdown tripping proportion coefficient of the line is calculated by the proportion of the relative ground breakdown times of the mountain fire historical tripping to the total times of the mountain fire historical tripping under the voltage class corresponding to the line;
λ p the line phase-to-phase breakdown tripping proportion coefficient is calculated by the proportion of the peak fire history tripping phase-to-phase breakdown times to the peak fire history tripping total times under the voltage class corresponding to the line;
pg (U) is the probability of the relative breakdown of the line to cause the tripping of the transmission line, and is represented by the formulaCalculating;
pp (U) is the probability of tripping a transmission line caused by line phase breakdown, and is represented by the formulaAnd (5) calculating.
Preferably, in the step S5, the probability of tripping the forest fire-induced transmission line is used as a probability evaluation index of risk, the importance evaluation value of the transmission line is used as a severity evaluation index of fault results, and a forest fire-induced line fault risk representation including a plurality of lines is established:
wherein J is a mountain fire-caused trip line set; p (P) l The trip probability of the line l under the mountain fire condition; e is the importance evaluation value of line l.
The calculation of the mountain fire-induced line tripping probability provided by the invention considers the differences of the line design elevation, the pole tower height, the line sag and the mountain fire occurrence place of different voltage grades, introduces temperature, conductivity and ash particles, corrects breakdown voltage, and has comprehensiveness and universality.
The analysis method provided by the invention can obtain the difference of the influence of mountain fire disasters on different lines and the severity of the influence result on the power grid, and provides effective suggestions for targeted disaster prevention deployment of power system operators.
The specific technical scheme and the beneficial effects of the invention are described in detail in the following detailed description with reference to the accompanying drawings.
Drawings
The invention is further described with reference to the drawings and detailed description which follow:
fig. 1 is a flowchart of a mountain fire-induced line fault risk assessment method according to the present invention.
Fig. 2 is a schematic diagram of a mountain fire-induced line fault mechanism and influencing factors counted by the invention.
Fig. 3 is a graph showing the relative air gap distribution of the line under the condition of mountain fire according to the present invention.
Fig. 4 is a graph showing the relative breakdown probability of the lines with different voltage classes according to the present invention.
Fig. 5 is a graph showing the relative breakdown probability of different voltage class lines according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
1. First, the method principle and the specific embodiments related to the present invention will be described:
as shown in fig. 1, a forest fire-induced line fault risk assessment method includes the following steps:
step S1: acquiring line information, forest fire information, environment information and power grid state information;
step S2: analyzing the mechanism of line tripping caused by mountain fire according to the mountain fire information and the environment information, determining the influence factors of the mountain fire on air gap breakdown, and calculating the correction coefficient of breakdown voltage;
step S3: according to the line information, calculating the line breakdown voltage under the condition of mountain fire, and evaluating the probability of tripping the transmission line caused by the relative breakdown of the line and the probability of tripping the transmission line caused by the inter-phase breakdown of the line;
step S4: and calculating the probability of tripping of the power transmission line under the condition of mountain fire by the probability of tripping of the power transmission line caused by the relative earth breakdown of the line and the probability of phase-to-phase breakdown of the power transmission line caused by the phase-to-phase breakdown of the line.
Step S5: according to the power grid state information, the importance and the influence degree of the line are considered, the severity degree of the line tripping influence on the power grid under the condition of the mountain fire is quantitatively analyzed, and the risk of the line fault caused by the mountain fire is estimated.
In step S1: the mountain fire information comprises mountain fire temperature, flame height and smoke concentration; the line information comprises actual running voltage, line-to-ground distance and line-to-line distance; the environment information comprises wind speed, air temperature, air pressure, combustible type, height and distribution; the power grid state information comprises a grid structure, tide distribution, power supply access capacity and positions.
As shown in fig. 2, step S2 summarizes the reasons why the fire causes the decrease in the gap insulation strength according to the analysis result of the fire-induced line tripping mechanism: temperature, conductivity, and ash particles.
1) Temperature: the air density is reduced by the large temperature rise, so that the average free path length of electrons is increased, the discharge is promoted, and the air insulation strength is reduced.
2) Conductivity: conductivity is the macroscopic manifestation of severe chemical ionization and thermal dissociation of alkali and alkaline earth ions caused by vegetation burning, which provides both the initial electrons for discharge and also injects a large amount of charge into the streamer channel to promote streamer development, thereby reducing gap dielectric strength.
3) Ash particles: the ash particles move to a strong field region under the action of thermal buoyancy and electric field force and approach to the lead, so that obvious distortion of electric fields at two ends of the particles is caused, if the critical field strength is exceeded, discharge is triggered, gaps among the lead, the particles and the particles are broken down, part of gaps are shorted, the electric field strength of other gaps is enhanced, and discharge is further promoted.
According to the above analysis, step S2 specifically comprises the following steps:
step 2.1, calculating an atmospheric correction coefficient:
introducing an atmospheric correction coefficient K for air gap insulation strength reduction caused by temperature rise t ：
K t ＝K d K h
Wherein K is t K is the atmospheric correction coefficient d K is the air density correction coefficient h Is an air humidity correction coefficient, and has:
wherein delta is the relative air densitym is an air density correction index, W is a humidity correction index, K depends on the voltage type and is a function of the ratio of absolute humidity to relative air density delta, and the values of the indexes m, W and K are referred to the national standard of GB/T16927.1-1997; p, p 0 The air pressures under the condition of mountain fire and under the condition of standard reference atmosphere are respectively t and t 0 The temperatures under the forest fire condition and the standard reference atmospheric condition are respectively; standard reference atmospheric conditions are temperature t 0 =20 ℃, pressure p 0 =101.3 kPa, absolute humidity h 0 ＝11g/m 2 . The air pressure under mountain fire conditions was obtained from meteorological data. The forest fire temperature is estimated from the type of combustible.
Step 2.2, calculating a particle correction factor:
introducing a particle correction factor K for air gap insulation strength reduction caused by carbonized small particles and ash smoke generated by combustion P ：
Wherein R is smoke concentration, r=0% indicates no impurity in the air gap, and r=100% indicates that the dense smoke fills the entire gap.
As shown in fig. 3, the step S3 specifically includes the following steps:
step 3.1, correcting the relative ground breakdown voltage and the interphase breakdown voltage of the circuit:
according to the voltage level of the circuit, the line-to-ground distance h of the typical circuit with different voltage levels is obtained by referring to the design rules l The height of the line at the mountain fire place can be used; obtaining the combustible material height h of the mountain fire area according to the environmental data of the line corridor r Thereby obtaining the relative air gap length H=h of the line l -h r 。
Under the condition of mountain fire, the air gap of the line is divided into a flame zone and a non-flame zone, and the relative breakdown voltage of the line is the sum of the air gap breakdown voltage of the flame zone and the air gap breakdown voltage of the non-flame zone. The air gap insulation strength of the flame area is affected by the temperature, carbonized small particles and ash smoke, and the air gap insulation strength of the non-flame area is affected by the ash smoke, so that the line air gap breakdown voltage can be corrected as follows:
wherein the first term is the flame area air gap breakdown voltage correction value, the second term is the non-flame area air gap breakdown voltage correction value, U is the line power frequency breakdown voltage under the condition of mountain fire, U 0 Is the line power frequency breakdown voltage under the standard atmospheric condition, U 0 The method comprises the steps of obtaining a relation chart of the long air gap power frequency 50% breakdown voltage and the air gap distance by referring to the relation chart; h is mountain fire height, H is air gap length, K p1 、K p2 Particle correction factors of the flame zone and the non-flame zone respectively, and the smoke concentration data of the flame zone and the non-flame zone respectively are used for controlling the particle correction factorsAnd (5) calculating to obtain the product.
For the air gap between the conducting wire of the power transmission line and the ground, h r +h<h l When the mountain fire is low, the flame area and the non-flame area need to be comprehensively considered, and the breakdown voltage of the air gap of the circuit relative to the ground is
For the air gap between the conducting wire of the power transmission line and the ground, h r +h≥h l When the mountain fire approaches or even envelops the wire, only the flame area is considered, and the breakdown voltage of the wire relative to the ground air gap is
U＝K t K p1 U 0
For the air gap between the wires, h r +h<h l When the mountain fire is not close to the wire, the inter-phase air gap is all in a non-flame region, the breakdown voltage of the inter-phase air gap is reduced to
U＝K p2 U 0
For the air gap between the wires, h r +h≥h l When the mountain fire approaches or even envelops the wire, the inter-phase air gap is all in the flame zone, and the breakdown voltage of the inter-phase air gap is
U＝K t K p1 U 0 ；
Step 3.2, calculating the line relative ground breakdown probability and the line inter-phase breakdown probability:
under the condition of mountain fire, the line breakdown voltage is considered to accord with normal distribution, and the breakdown probability density is expressed as:
wherein U is line voltage when mountain fire occurs; mean mu is equal to U 50％ The power frequency breakdown voltage is 50%; sigma= zU 50％ The method comprises the steps of carrying out a first treatment on the surface of the z is a variation coefficient, and the value is between 2% and 8%. Under the electric field forms of different gaps and different types of breakdown voltages, the dispersibility is different, and the value of the variation coefficient z is 2% -8% different. Under normal conditions, the dispersity of the air gap power frequency breakdown voltage is not large, and 2% is taken. However, considering that the mountain fire occurs, the particles cause the air gap to be more uneven, and the dispersibility increases. Therefore, when mountain fire occurs, the coefficient of variation z is 4%.
Under the condition of mountain fire, the variation coefficient z is taken to be 4 percent, and the line breakdown probability is
And S4, classifying the fault types of the power transmission line tripping under the mountain fire condition into two types of relative ground breakdown tripping and interphase breakdown tripping. Combining the actual voltage class and fault type of the power transmission line, calculating the probability of tripping the power transmission line under the condition of mountain fire according to the proportion distribution of the relative ground breakdown and interphase breakdown in the historical statistical data of the voltage class of the power transmission line
Pl(U)＝λg·Pg(U)+λp·Pp(U)
Wherein λg is the relative ground breakdown trip proportion coefficient of the line, and is calculated by the proportion of the relative ground breakdown times of mountain fire historical trip to the total times of mountain fire historical trip under the voltage class corresponding to the line; λp is a line phase-to-phase breakdown trip proportion coefficient calculated by the proportion of the peak fire history trip phase-to-phase breakdown times to the peak fire history trip total times under the voltage class corresponding to the line; pg (U) is the probability of the tripping of the transmission line caused by the relative breakdown of the line, and is calculated by a formula; pp (U) is the probability of line phase breakdown causing the transmission line to trip, calculated by the equation.
Step S5, taking the probability of mountain fire-induced power transmission line tripping as a probability evaluation index of risk, taking an importance evaluation value of the power transmission line as a fault result severity evaluation index, and establishing a mountain fire-induced line fault risk representation comprising a plurality of lines:
wherein r is the risk of line fault caused by mountain fire; j is a mountain fire-caused trip line set; p (P) l The probability of tripping the line l under the mountain fire condition is given; e is an importance evaluation value of the line l and is also an evaluation index of the severity of the fault result.
2. The following is a specific case of using the above method:
referring to 110kV lines in the national environmental protection standard, the height of the wires from the ground is set to be 11.50m, and the distance between the wires is set to be 4.25m. Looking up a relation chart of the long air gap power frequency 50% breakdown voltage and the air gap distance, it can be known that under normal conditions, the phase 50% power frequency breakdown voltage is 2100kV, and the phase 50% power frequency breakdown voltage is 1900kV.
Reference is made to 500kV lines in national environmental standards. The line-to-ground distance is 12.19m, the phase-to-phase distance is 13.72m, the 50% power frequency breakdown voltage of the phase-to-ground is 3657kV, and the 50% power frequency breakdown voltage of the phase-to-phase is 4116kV.
The reference is made to a typical 1000kV extra-high voltage alternating current double-circuit transmission line. In the center of the line span, the line-to-ground distance is 20.9m, the phase-to-phase distance is 19.4m, the 50% power frequency breakdown voltage of the phase-to-ground is 6720kV, and the 50% power frequency breakdown voltage of the phase-to-phase is 5820kV.
The line operating voltage is rated and takes the same particle correction factor in the flame zone and the non-flame zone, i.e. K p1 ＝K p2 . And correcting the discharge voltage according to the mountain fire conditions of different temperatures and smoke concentrations, and calculating the fault probability of breakdown of the air gap under different conditions. Setting mountain fire conditions: the off-line trees were set to a maximum of about 5m, with mountain fire height h=6m.
Fig. 4 shows the relative ground breakdown probability of the transmission lines with different voltage levels with smoke concentration r=50% according to the temperature. It can be seen that under the condition that the arranged mountain fire possibly causes phase-to-ground breakdown, the breakdown probability of the extra-high voltage line is far lower than that of a 110kV power transmission line and an extra-high voltage line. In the simulated temperature range, the maximum breakdown probability of the 110kV power transmission line exceeds 100%, the maximum breakdown probability of the 500kV ultra-high voltage line exceeds 80%, and the maximum breakdown probability of the 1000kV ultra-high voltage line is less than 20%. The reason is mainly that the breakdown probability of the extra-high voltage phase is far lower than that of a 110kV transmission line and the extra-high voltage because the non-flame area of the extra-high voltage is 14.90 m.
Fig. 5 is a graph showing the relative breakdown probability of different voltage class lines as a function of smoke concentration. Therefore, the phase-to-ground breakdown probability of the 110kV power transmission line starts to rise rapidly when R=40%, and the ultra-high voltage reach about R=45%, so that the lower the voltage level is under the same smoke concentration, the phase-to-ground breakdown accident is more likely to happen.
According to different wind speeds and different combustible environmental data, the mountain fire spreading speed and the fire wire intensity are calculated, the average temperature of the air gap of the line and the fire scene formed by the mountain fire are calculated according to the mountain fire spreading speed and the fire wire intensity, the probability of breakdown and tripping of the mountain fire-induced line can be calculated, the probability of outage of the power transmission lines at different distances from the ignition source along different directions is predicted, the trip risk of the mountain fire-induced line is calculated according to the importance of the line, and the auxiliary dispatching department reacts in time.
While the invention has been described in terms of specific embodiments, it will be appreciated by those skilled in the art that the invention is not limited to the specific embodiments described above. Any modifications which do not depart from the functional and structural principles of the present invention are intended to be included within the scope of the appended claims.
Claims (2)
1. The mountain fire-induced line fault risk assessment method is characterized by comprising the following steps of:
step S1: acquiring line information, forest fire information, environment information and power grid state information;
step S2: calculating a correction coefficient of breakdown voltage according to the mountain fire information and the environment information acquired in the step S1:
step S3: according to the line information, calculating the line breakdown voltage under the condition of mountain fire, and evaluating the probability of tripping the transmission line caused by the relative breakdown of the line and the probability of tripping the transmission line caused by the inter-phase breakdown of the line;
step S4: calculating the probability of tripping of the power transmission line under the condition of mountain fire by the probability of tripping of the power transmission line caused by the relative earth breakdown of the line and the probability of phase-to-phase breakdown of the power transmission line caused by the phase-to-phase breakdown of the line;
step S5: according to the state information of the power grid, taking importance and influence degree of the line into consideration, carrying out quantitative analysis on the severity degree of the line tripping influence on the power grid under the condition of mountain fire, evaluating the risk of the line fault caused by the mountain fire,
the mountain fire information comprises mountain fire temperature, flame height and smoke concentration; the line information comprises actual running voltage, line-to-ground distance and line-to-line distance; the environment information comprises wind speed, air temperature, air pressure, combustible type, height and distribution; the power grid state information comprises a grid structure, power flow distribution, power supply access capacity and positions;
step S2 comprises the steps of:
step 2.1, calculating an atmospheric correction coefficient:
for air gap insulation strength reduction caused by temperature riseIntroducing an atmospheric correction coefficient K t ：
K t ＝K d K h
Wherein K is d K is the air density correction coefficient h Is an air humidity correction coefficient, and has:
where delta is the relative air density,the values of the indexes m, W and K come from the national standard GB/T16927.1-1997, p and p 0 The air pressures under the condition of mountain fire and under the condition of standard reference atmosphere are respectively t and t 0 The temperatures under the forest fire condition and the standard reference atmospheric condition are respectively;
step 2.2, calculating a particle correction factor:
introducing a particle correction factor K for air gap insulation strength reduction caused by carbonized small particles and ash smoke generated by combustion P ：
Wherein R is smoke concentration, r=0% indicates no impurity in the air gap, and r=100% indicates that the dense smoke fills the whole gap;
the step S3 includes the steps of:
step 3.1, correcting the relative ground breakdown voltage and the interphase breakdown voltage of the circuit:
according to the voltage level of the circuit, the line-to-ground distance h of the typical circuit with different voltage levels is obtained by referring to the design rules l As the line height of the mountain fire place; obtaining the combustible material height h of the mountain fire area according to the environmental information of the line corridor r Thereby obtaining the relative air gap length H=h of the line l -h r ；
Under the condition of mountain fire, the air gap of the circuit is divided into a flame zone and a non-flame zone, the relative breakdown voltage of the circuit is the sum of the breakdown voltage of the air gap of the flame zone and the breakdown voltage of the air gap of the non-flame zone, the insulation strength of the air gap of the flame zone is affected by the combined action of temperature, carbonized small particles and ash smoke, and the insulation strength of the air gap of the non-flame zone is affected by the ash smoke, so that the breakdown voltage of the air gap of the circuit can be corrected as follows:
wherein the first term is the flame area air gap breakdown voltage correction value, the second term is the non-flame area air gap breakdown voltage correction value, U is the line power frequency breakdown voltage under the condition of mountain fire, U 0 The line power frequency breakdown voltage is the line power frequency breakdown voltage under the standard atmospheric condition; h is mountain fire height, H is air gap length, K p1 、K p2 Particle correction factors of the flame zone and the non-flame zone respectively, and the smoke concentration data of the flame zone and the non-flame zone respectively are used for controlling the particle correction factorsCalculating to obtain;
for the air gap between the conducting wire of the power transmission line and the ground, the mountain fire height is lower, namely h r +h<h l When the flame zone and the non-flame zone are needed to be considered comprehensively, the breakdown voltage of the line to the ground air gap is
For the air gap between the conductor and the ground of the power transmission line, if the mountain fire is close to or even envelops the conductor, the air gap is h r +h≥h l When the flame area is considered, the breakdown voltage of the line to the ground air gap is
U＝K t K p1 U 0
For the air gap between the wires, the fire is not close to the wires, namely r +h<h l I.e. the air gap is considered to be entirely in the non-flame region, the inter-phase air gap breaks downVoltage degradation to
U＝K p2 U 0
For the air gap between the wires, if the mountain fire approaches or even envelops the wires, the air gap is h r +h≥h l An inter-phase air gap breakdown voltage of
U＝K t K p1 U0；
Step 3.2, calculating the line relative ground breakdown probability and the line inter-phase breakdown probability:
under the condition of mountain fire, the line breakdown voltage is considered to accord with normal distribution, and the breakdown probability density is expressed as:
wherein U is line voltage when mountain fire occurs; mean mu is equal to U 50％ The power frequency breakdown voltage is 50%; sigma= zU 50％ The method comprises the steps of carrying out a first treatment on the surface of the z is a variation coefficient, and the value is between 2 and 8 percent;
step S4 is to classify the fault types of the electric transmission line tripping under the condition of mountain fire into two types of relative ground breakdown tripping and inter-phase breakdown tripping, and calculate the probability of the electric transmission line tripping under the condition of mountain fire according to the proportion distribution of the relative ground breakdown and the inter-phase breakdown in the historical statistical data of the electric transmission line voltage level by combining the actual electric transmission line voltage level and the fault types
P l (U)＝λ g ·P g (U)+λ p ·P p (U)
λ g The relative ground breakdown tripping proportion coefficient of the line is calculated by the proportion of the relative ground breakdown times of the mountain fire historical tripping to the total times of the mountain fire historical tripping under the voltage class corresponding to the line;
λ p the line phase-to-phase breakdown tripping proportion coefficient is calculated by the proportion of the peak fire history tripping phase-to-phase breakdown times to the peak fire history tripping total times under the voltage class corresponding to the line;
pg (U) is the probability of the relative breakdown of the line to cause the tripping of the transmission line, and is represented by the formulaCalculating;
pp (U) is the probability of tripping a transmission line caused by line phase breakdown, and is represented by the formulaCalculating;
step S5 is to set up a mountain fire-induced line fault risk representation comprising a plurality of lines by taking the mountain fire-induced power transmission line tripping probability as a probability evaluation index of risk and taking an importance evaluation value of the power transmission line as a fault result severity evaluation index:
wherein J is a mountain fire-caused trip line set; p (P) l The trip probability of the line l under the mountain fire condition; e is the importance evaluation value of line l.
2. The mountain fire initiated line fault risk assessment method as claimed in claim 1, wherein: under the condition of mountain fire, the variation coefficient z is taken to be 4 percent, and the line breakdown probability is
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| CN106886841A (en) * | 2017-02-24 | 2017-06-23 | 湖南省湘电试研技术有限公司 | Without the circuit mountain fire Disaster Assessment method and system of Real-time Collection field data |
| CN107704713A (en) * | 2017-10-31 | 2018-02-16 | 合肥天鹰高科技有限公司 | A kind of transmission line forest fire is distributed appraisal procedure |
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| CN104915775A (en) * | 2015-06-05 | 2015-09-16 | 国家电网公司 | Risk assessment and emergency decision-making method for forest fire disaster of power transmission line |
| CN106886841A (en) * | 2017-02-24 | 2017-06-23 | 湖南省湘电试研技术有限公司 | Without the circuit mountain fire Disaster Assessment method and system of Real-time Collection field data |
| CN107704713A (en) * | 2017-10-31 | 2018-02-16 | 合肥天鹰高科技有限公司 | A kind of transmission line forest fire is distributed appraisal procedure |
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