CN107196277B - The active heat protection method of transmission line of electricity based on the prediction of electric current tolerance time - Google Patents
The active heat protection method of transmission line of electricity based on the prediction of electric current tolerance time Download PDFInfo
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- CN107196277B CN107196277B CN201710409746.1A CN201710409746A CN107196277B CN 107196277 B CN107196277 B CN 107196277B CN 201710409746 A CN201710409746 A CN 201710409746A CN 107196277 B CN107196277 B CN 107196277B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
- H02H7/262—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of switching or blocking orders
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
- H02H7/263—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of measured values
Abstract
The invention discloses a kind of active heat protection methods of transmission line of electricity based on the prediction of electric current tolerance time; when power flow transfer, which occurs, for power grid leads to protected circuit current jump; route overcurrent tolerance, the actual time safety state of Accurate Prediction route are characterized using conductor temperature；The live value and predicted value of route operation meteorological condition are obtained, calculates route temperature rise response with the safe tolerance time of Accurate Prediction transmission line of electricity overcurrent with weather station distribution characteristics, subregion segmentation along the line based on transmission line of electricity geography information；Then power network dispatching system is fed back to, provides basis of time for accurately stable control；Conductor temperature variation track during Focus Control cuts off the route if still having more than highest allows the dangerous situation of running temperature.For this method under the premise of guaranteeing system safety, the tolerance of raising route as far as possible avoids cascading trip so as to delay trip protection to act as far as possible to greatest extent.
Description
Technical field
The present invention relates to the novel relay protecting methods of transmission line of electricity, refer specifically to a kind of based on the time prediction of electric current tolerance
The active heat protection method of overhead transmission line, belong to technical field of electric system protection.
Background technique
The multiple large-area power-cuts that recent domestic occurs has caused the concern of people, and summarizing reason is due to a mostly
The excision of other element fault causes electricity grid network structure to change, and causes system load flow transfer so as to cause part transmission line of electricity
Electric current transition occurs, electric current cuts off route if being more than the protection seting value of the route, and then causes the trend of a new round
Transfer, is eventually developed to cascading trip accident.The research of prevention power grid cascading tripping is concentrated mainly on wide area protection at present
(wide-area protection system, WAPS) etc., more stringent requirements are proposed to communication for wide area protection, needs
All multidate informations of real-time collecting power grid, that there is calculation amounts is excessive, is difficult to the disadvantages of determining reasonable protection scope.
Route protection tripping boosting cascading failure has its source in protection according to transmission line of electricity running current parameter beyond just
Normal boundary is starting tripping condition, and this boundary condition cannot dynamically reflect the real-time change of line security state, so that hair
When raw power flow transfer current jump before dispatcher takes regulation measure, protection cuts off route with regard to auto-action, although this
It ensure that the safety of the equipment such as transmission line of electricity, but thus cause bigger cascading trip, be unfavorable for system safety and stability.
The tolerance that route carries overcurrent is mainly limited by conducting wire running temperature and electric insulation clearance distance, with leading
Weather environment locating for line, conducting wire electric property, mechanical performance and heating power phenomenon and change.Existing Transmission Line Design specification
In operating standard, using maximum permissible temperature characterization transmission line safety running temperature and over the ground, the minimum peace of scissors crossing
Two aspect of full distance.So comparing electric current, the overcurrent tolerance using temperature characterization route will more accurately reflect route
Safe condition, and there are time-lag effects between route temperature rise and current jump, if the extension of route thermal inertia can be made full use of
Time can gain time for accurate security and stability control.
Summary of the invention
For the prior art using current parameters beyond normal boundary as starting tripping condition above shortcomings, it is of the invention
It is proposed a kind of active heat protection method of transmission line of electricity based on the prediction of electric current tolerance time, this method is guaranteeing system safety
Under the premise of, the tolerance of raising route as far as possible avoids chain jump so as to delay trip protection to act as far as possible to greatest extent
Lock.
Based on the active heat protection method of transmission line of electricity of electric current tolerance time prediction, juche idea is as shown in Figure 1, protection
Logic is as shown in Fig. 2, technical solution of the present invention carries out as follows:
Step 1 information collection: acquisition transmission line of electricity multi-source data
Weather station is limited in the power system and can not be overlapped completely with power transmission line corridor, and high pressure is defeated over long distances
Electric line can pass through the special region of some weather conditions, and meteorological condition may have apparent difference with the environment on periphery.Cause
This, according to overhead transmission line parameter, geographical location original image, in conjunction in crossed over range weather station and weather bureau's publication
Weather forecast data, to route carry out subregion segmentation fining obtain weather information, it is resistance to effectively improve subsequent route overcurrent
By the computational accuracy of time prediction.Transmission line of electricity as shown in Figure 3 can be according to its geographical environment and surrounding weather station distribution characteristics
It is divided into N sections, obtains the live value and forecast of the meteorological variables such as wind speed, wind direction, environment temperature, humidity and the intensity of sunshine in each region
Value, the meteorological input quantity of temperature rise calculating and tolerance time prediction as subsequent each section of route.It is being not required to addition measuring device
In the case of, route current information is acquired by the measuring cell of circuit relay protection in real time, power transmission line is acquired by temperature element
Line conductor temperature.
Step 2 protection starting: temperature of electric transmission line start-up criterion and overcurrent start-up criterion
By temperature of electric transmission line start-up criterion and overcurrent start-up criterion, opening for the active Thermal protection of transmission line of electricity is realized
Dynamic function.If any one in the two meets criterion, starting is protected.Temperature of electric transmission line start-up criterion is the conducting wire that will be acquired
Temperature value θcWith conductor temperature initiation value θstartIt is compared, if being more than conductor temperature initiation value, protects starting, embody
Formula is as follows:
θc> θstart,θstart=kθθmax (1)
In formula (1), kθFor temperature startup coefficient, 0.6-0.8, θ are takenmaxThe highest of conducting wire rolling schedule design is taken to allow to run temperature
Degree；
Overcurrent start-up criterion is the line current information I that will be acquiredcWith current start value IstartIt is compared, if acquisition
Current value is more than current start value, then protects starting, expression is as follows:
Ic> Istart,Istart=kIIL.max (2)
In formula (2), kIFor current start coefficient, 0.8-0.9, I are takenL.maxIndicate route maximum load current；
Step 3 tolerance time prediction: transmission line of electricity overcurrent tolerance time prediction
Tolerance time prediction is carried out after protection starting, transmission line of electricity multi-source data information collected is based on, passes through conducting wire
Dynamic thermal balance analysis acquires conducting wire temperature rise response expression formula, takes the highest of conducting wire rolling schedule design that running temperature is allowed to be route
It is resistant to a reference value, measures the safe tolerance time of route in advance, specific to predict that process is as follows:
3.1) transmission line of electricity dynamic thermal balance is analyzed
Under service condition, transmission of electricity component temperature variation is related to running environment and state, for overhead transmission line,
Temperature change is mainly influenced by factors such as current-carrying, wind speed, wind direction, sunshine, temperature.Transmission line of electricity dynamic thermal balance equation is
To the mathematical modeling of transmission line of electricity electro thermal coupling rule on the basis of comprehensively considering above-mentioned factor, embody as follows:
In formula (3), qc、qr、qs、qlIt is heat loss through convection power, the heat loss through radiation power, sunshine of unit length conducting wire respectively
Heating power and joule thermal power, W/m；θ indicates conductor temperature, usually takes the mean temperature of each twisted layer, DEG C.For by a variety of materials
The conducting wire for expecting composition for steel-cored aluminium strand, there is mc=ma·ca+ms·cs；Wherein, ma、msFor aluminium in unit length conducting wire,
The quality kg/m of Steel material；ca、csFor the specific heat capacity of aluminium, Steel material, J/ (kg DEG C).
3.2) transmission line of electricity temperature prediction expression formula derives
Under conditions of known meteorologic parameter and transmission line of electricity short-time overload amount, analytically analyzes derivation of starting with and acquire electric current punching
Hit the temperature time-domain expression of rear thermal inertia process are as follows:
In formula (4), D indicates the diameter of conducting wire；θ0、θa、θmaxIt is the initial temperature of conducting wire, operating ambient temperature and most respectively
Height allows running temperature；RrefThe AC equivalent resistance for referring to transmission line of electricity is sought with reference to the calculating of Transmission Line Design handbook；Ac、
Ar、AsIt is heat loss through convection coefficient, heat loss through radiation coefficient, the sunshine heat absorption coefficient of conducting wire respectively, is marked with reference to ieee standard and CIGRE
Standard is calculated and is sought；I0、IfIt is current effective value after the initial current virtual value of conducting wire, power flow transfer respectively, i.e. k indicates route
Overcurrent multiple.
3.3) transmission line safety tolerance time is predicted
If taking θmaxAs overcurrent in short-term maximum permissible temperature when, corresponding current multiple k can be acquired by temperature rise analytic modell analytical model
With the relationship of temperature rising-time are as follows:
Running temperature θ is allowed by highestmax, can be obtained conducting wire at such a temperature critical permission electric current relative to initial launch
The multiple proportion formula of electric current are as follows:
By conducting wire heat balance theory it is found that allowing the ascending temperature time infinite when overcurrent is less than critical permission electric current
Greatly.When overcurrent is greater than critical permission electric current, the bigger temperature rise of electric current allows the time will be smaller.Specific functional relation is as follows:
3.4) selection of full transmission line safety tolerance time
According to the real-time electrical quantity of full power transmission line corridor and meteorological amount data sectional region division, route is divided into N sections.
Obtain each region wind speed, wind direction, environment temperature, humidity and intensity of sunshine these meteorological variables real-time or predicted value after,
Each section of line energizing flow amount can calculate respectively according to formula (7), obtain N number of safe tolerance time value, then whole route shown in Fig. 2
Safe tolerance time is taken as minimum value in N sections.It indicates are as follows:
Ts=min { ts1,ts2,…tsi…tsNI=1,2 ... N (8)
Step 4 temperature warning:
Predict that obtained conducting wire after safe tolerance time, sends tolerance time information to power network dispatching system in short-term, for essence
Quasi- stable control provides time reference, while sending enabling signal to starting timing element, and starting timing element starts timing.?
During this, takes power regulation, cuts the security and stability control measurements such as machine-cut load, power grid is made to restore safety and stability as early as possible；Work as meter
When element time reach 0.5TsWarning information is sent to power network dispatching system, reminds dispatcher by the moment.
Step 5 trip protection:
When timing time reaches TsMoment then sends trip signal to line-breaker and scheduling system, in time excision temperature
Spend out-of-limit route.Conductor temperature is monitored in safe tolerance time section simultaneously, when meeting temperature beyond limit operating criterion, nothing
It needs to wait for timing time and reaches TsMoment, Thermal protection directly can send trip signal to line-breaker and scheduling system, cut
Except the route of temperature beyond limit.
Temperature beyond limit operating criterion is the conductor temperature value θ that will be acquiredcWith conductor temperature action value θsetIt is compared, if
More than conductor temperature action value, then protection act, expression are as follows:
θc> θset,θset=krelθmax (9)
In formula (9), krelFor safety factor, 1.05-1.1 is taken.
Due in starting timing to arrival TsIn etching process, scheduling system, which may take, cuts the stable control such as machine-cut load
Measure processed, the implementation of these measures, the protection start-up criterion before may being allowed to no longer meet, i.e., temperature or electric current are lower than correspondence
Initiation value, even if at this time reach TsIt is moment, maximum so as to delay trip protection to act as far as possible without trip protection
Limit avoids cascading trip.
Compared with prior art, the invention has the following beneficial effects:
The active heat protection method of transmission line of electricity provided by the present invention, in power flow transfer initial stage active predicting transmission line of electricity
The real-time change trend of security performance, under the premise of being not required to addition expensive device, by the existing on-line monitoring of transmission line of electricity
Device, microclimate station and fining Meteorology Forecast System, the overcurrent tolerance time of Accurate Prediction route are dug to greatest extent
It digs transmission line of electricity and is resistant to power flow transfer overcurrent capability；Urgent emergency case, which is coped with, in grid operator takes treatment measures in time
When, the safe tolerance of current transmission line of electricity is fed back into power network dispatching system in time, quilt is eliminated in the stable control of active negotiation
The overcurrent of protection circuit guarantees electricity net safety stable, effectively avoids occurrence of large-area cascading trip accident, guarantees power grid security
Stable operation.
Detailed description of the invention
Fig. 1 is the juche idea figure of the active heat protection method of transmission line of electricity.
Fig. 2 is the logic diagram of the active heat protection method of transmission line of electricity.
Fig. 3 is the segment-and-region-based acquisition mode figure of transmission line of electricity weather information data.
Fig. 4 is that the tolerance time of the active heat protection method of transmission line of electricity predicts flow chart.
Specific embodiment
The present invention is based on the active heat protection method of transmission line of electricity of electric current tolerance time prediction, juche ideas are as follows: work as electricity
When power flow transfer, which occurs, for net leads to protected circuit current jump, route overcurrent tolerance is characterized using conductor temperature, it is quasi-
The really actual time safety state of prediction route；Weather station distribution characteristics based on transmission line of electricity geography information and along the line, subregion point
Section obtains the live value and predicted value of route operation meteorological condition, calculates route temperature rise response with Accurate Prediction power transmission line and passes by electricity
Flow safe tolerance time value；Tolerance time information is fed back into power network dispatching system, for accurately it is stable control provide the time according to
According to, while conductor temperature variation track during Focus Control is cut if still having more than highest allows the dangerous situation of running temperature
Except route, avoid generation arc sag because caused by temperature is excessively high out-of-limit and thermal ageing；Juche idea is as shown in Figure 1.
The present invention specifically carries out as follows:
Step 1 information collection: acquisition transmission line of electricity multi-source data
Weather station is limited in the power system and can not be overlapped completely with power transmission line corridor, and high pressure is defeated over long distances
Electric line can pass through the special region of some weather conditions, and meteorological condition may have apparent difference with the environment on periphery.Cause
This, according to overhead transmission line parameter, geographical location original image, in conjunction in crossed over range weather station and weather bureau's publication
Weather forecast data, to route carry out subregion segmentation fining obtain weather information, it is resistance to effectively improve subsequent route overcurrent
By the computational accuracy of time prediction.Transmission line of electricity as shown in Figure 3 can be according to its geographical environment and surrounding weather station distribution characteristics
It is divided into N sections, obtains the live value and forecast of the meteorological variables such as wind speed, wind direction, environment temperature, humidity and the intensity of sunshine in each region
Value, the meteorological input quantity of temperature rise calculating and tolerance time prediction as subsequent each section of route.It is being not required to addition measuring device
In the case of, route current information is acquired by the measuring cell of circuit relay protection in real time, power transmission line is acquired by temperature element
Line conductor temperature.
Step 2 protection starting: temperature of electric transmission line start-up criterion and overcurrent start-up criterion
By temperature of electric transmission line start-up criterion and overcurrent start-up criterion, opening for the active Thermal protection of transmission line of electricity is realized
Dynamic function.If any one in the two meets criterion, starting is protected.Temperature of electric transmission line start-up criterion is the conducting wire that will be acquired
Temperature value θcWith conductor temperature initiation value θstartIt is compared, if being more than conductor temperature initiation value, protects starting, embody
Formula is as follows:
θc> θstart,θstart=kθθmax (1)
In formula (1), kθFor temperature startup coefficient, 0.6-0.8, θ are takenmaxThe highest of conducting wire rolling schedule design is taken to allow to run temperature
Degree；
Overcurrent start-up criterion is the line current information I that will be acquiredcWith current start value IstartIt is compared, if acquisition
Current value is more than current start value, then protects starting, expression is as follows:
Ic> Istart,Istart=kIIL.max (2)
In formula (2), kIFor current start coefficient, 0.8-0.9, I are takenL.maxIndicate route maximum load current；
The prediction of step 3 tolerance time: transmission line of electricity overcurrent tolerance time predicts (referring also to Fig. 4)
Tolerance time prediction is carried out after protection starting, transmission line of electricity multi-source data information collected is based on, passes through conducting wire
Dynamic thermal balance analysis acquires conducting wire temperature rise response expression formula, takes the highest of conducting wire rolling schedule design that running temperature is allowed to be route
It is resistant to a reference value, measures the safe tolerance time of route in advance, specific to predict that process is as follows:
3.1) transmission line of electricity dynamic thermal balance is analyzed
Under service condition, transmission of electricity component temperature variation is related to running environment and state, for overhead transmission line,
Temperature change is mainly influenced by factors such as current-carrying, wind speed, wind direction, sunshine, temperature.Transmission line of electricity dynamic thermal balance equation is
To the mathematical modeling of transmission line of electricity electro thermal coupling rule on the basis of comprehensively considering above-mentioned factor, embody as follows:
In formula (3), qc、qr、qs、qlIt is heat loss through convection power, the heat loss through radiation power, sunshine of unit length conducting wire respectively
Heating power and joule thermal power, W/m；θ indicates conductor temperature, usually takes the mean temperature of each twisted layer, DEG C.For by a variety of materials
The conducting wire for expecting composition for steel-cored aluminium strand, there is mc=ma·ca+ms·cs；Wherein, ma、msFor aluminium in unit length conducting wire,
The quality kg/m of Steel material；ca、csFor the specific heat capacity of aluminium, Steel material, J/ (kg DEG C).
3.2) transmission line of electricity temperature prediction expression formula derives
Under conditions of known meteorologic parameter and transmission line of electricity short-time overload amount, analytically analyzes derivation of starting with and acquire electric current punching
Hit the temperature time-domain expression of rear thermal inertia process are as follows:
In formula (4), D indicates the diameter of conducting wire；θ0、θa、θmaxIt is the initial temperature of conducting wire, operating ambient temperature and most respectively
Height allows running temperature；RrefThe AC equivalent resistance for referring to transmission line of electricity is sought with reference to the calculating of Transmission Line Design handbook；Ac、
Ar、AsIt is heat loss through convection coefficient, heat loss through radiation coefficient, the sunshine heat absorption coefficient of conducting wire respectively, is marked with reference to ieee standard and CIGRE
Standard is calculated and is sought；I0、IfIt is current effective value after the initial current virtual value of conducting wire, power flow transfer respectively, i.e. k indicates route
Overcurrent multiple.
3.3) transmission line safety tolerance time is predicted
If taking θmaxAs overcurrent in short-term maximum permissible temperature when, corresponding current multiple k can be acquired by temperature rise analytic modell analytical model
With the relationship of temperature rising-time are as follows:
Running temperature θ is allowed by highestmax, can be obtained conducting wire at such a temperature critical permission electric current relative to initial launch
The multiple proportion formula of electric current are as follows:
By conducting wire heat balance theory it is found that allowing the ascending temperature time infinite when overcurrent is less than critical permission electric current
Greatly.When overcurrent is greater than critical permission electric current, the bigger temperature rise of electric current allows the time will be smaller.Specific functional relation is as follows:
3.4) selection of full transmission line safety tolerance time
According to the real-time electrical quantity of full power transmission line corridor and meteorological amount data sectional region division, route is divided into N sections.
Obtain each region wind speed, wind direction, environment temperature, humidity and intensity of sunshine these meteorological variables real-time or predicted value after,
Each section of line energizing flow amount can calculate respectively according to formula (7), obtain N number of safe tolerance time value, then whole route shown in Fig. 2
Safe tolerance time is taken as minimum value in N sections.It indicates are as follows:
Ts=min { ts1,ts2,…tsi…tsNI=1,2 ... N (8)
Step 4 temperature warning:
Predict that obtained conducting wire after safe tolerance time, sends tolerance time information to power network dispatching system in short-term, for essence
Quasi- stable control provides time reference, while sending enabling signal to starting timing element, and starting timing element starts timing.?
During this, takes power regulation, cuts the security and stability control measurements such as machine-cut load, power grid is made to restore safety and stability as early as possible；Work as meter
When element time reach 0.5TsWarning information is sent to power network dispatching system, reminds dispatcher by the moment.
Step 5 trip protection:
When timing time reaches TsMoment then sends trip signal to line-breaker and scheduling system, in time excision temperature
Spend out-of-limit route.Conductor temperature is monitored in safe tolerance time section simultaneously, when meeting temperature beyond limit operating criterion, nothing
It needs to wait for timing time and reaches TsMoment, Thermal protection directly can send trip signal to line-breaker and scheduling system, cut
Except the route of temperature beyond limit.
Temperature beyond limit operating criterion is the conductor temperature value θ that will be acquiredcWith conductor temperature action value θsetIt is compared, if
More than conductor temperature action value, then protection act, expression are as follows:
θc> θset,θset=krelθmax (9)
In formula (9), krelFor safety factor, 1.05-1.1 is taken.
Due in starting timing to arrival TsIn etching process, scheduling system, which may take, cuts the stable control such as machine-cut load
Measure processed, the implementation of these measures, the protection start-up criterion before may being allowed to no longer meet, i.e., temperature or electric current are lower than correspondence
Initiation value, even if at this time reach TsIt is moment, maximum so as to delay trip protection to act as far as possible without trip protection
Limit avoids cascading trip.Relay protective scheme of the present invention is as shown in Figure 2.
Finally, it should be noted that examples detailed above of the invention is only example to illustrate the invention, and it is not
It is the restriction to embodiments of the present invention.It is right although applicant describes the invention in detail referring to preferred embodiment
For those of ordinary skill in the art, can also make on the basis of the above description other it is various forms of variation and
It changes.Here all embodiments can not be exhaustive.All belong to that technical solution of the present invention amplifies out aobvious and
The variation or variation being clear to are still in the scope of protection of the present invention.
Claims (5)
1. the active heat protection method of transmission line of electricity based on the prediction of electric current tolerance time, it is characterised in that: specific step is as follows,
(1) transmission line wire temperature information collection: is acquired by temperature element；It is adopted by the measuring cell of circuit relay protection
Collect route current information；According to the distribution characteristics of transmission line of electricity geographical map and weather station along the line, transmission line of electricity is segmented, and
Each section of weather information of piecewise acquisition power transmission line corridor institute overlay area, weather information include: wind speed, wind direction, environment temperature,
The live value and predicted value of humidity and intensity of sunshine；
(2) protection starting: setting conductor temperature start-up criterion and current start criterion, if any one in the two meets criterion,
Then protect starting；
(3) tolerance time is predicted: tolerance time prediction is carried out after protection starting, it is more based on step (1) transmission line of electricity collected
Source data information is analyzed by conducting wire dynamic thermal balance, is acquired conducting wire temperature rise response expression formula, is taken the highest of conducting wire rolling schedule design
Allowing running temperature is that route is resistant to a reference value, measures the safe tolerance time T of route in advances；
(4) temperature warning: after the safe tolerance time of the conducting wire that (3) step is predicted, safe tolerance time information is fed back to
Power network dispatching system, while enabling signal is sent to starting timing element, start timing；When timing time reaches 0.5TsMoment,
Alarm signal is sent to power network dispatching system；
(5) trip protection: when timing time reaches TsMoment then sends trip signal to line-breaker and scheduling system, in time
Cut off the route of temperature beyond limit；Conductor temperature is monitored in safe tolerance time section simultaneously, is sentenced when meeting temperature beyond limit movement
According to when, even if TsIt has not timed out, still sends trip signal to line-breaker and scheduling system, cut off temperature beyond limit in time
Route；
Safe tolerance time described in (3) step is predicted as follows:
3.1) transmission line of electricity dynamic thermal balance is analyzed
Mathematical modeling is carried out to transmission line of electricity electro thermal coupling rule, is embodied as follows:
Wherein, qc、qr、qs、qlIt is the heat loss through convection power, heat loss through radiation power, sunshine heating power of unit length conducting wire respectively
With joule thermal power, W/m；θ indicates conductor temperature, takes the mean temperature of each twisted layer, DEG C；M is the quality kg/ of unit length conducting wire
m；C is the specific heat capacity of conducting wire, J/ (kg DEG C)；
3.2) transmission line of electricity temperature prediction expression formula derives
Analytically analyze the temperature time-domain expression for starting with and deriving and acquiring thermal inertia process after electric current changes are as follows:
Wherein, D indicates the diameter of conducting wire；θ0、θa、θmaxIt is initial temperature, operating ambient temperature and the highest permission of conducting wire respectively
Running temperature；RrefRefer to the AC equivalent resistance of transmission line of electricity；Ac、Ar、AsBe respectively conducting wire heat loss through convection coefficient, radiation dissipate
Hot coefficient, sunshine heat absorption coefficient；I0、IfIt is current effective value, i.e. k table after the initial current virtual value of conducting wire, power flow transfer respectively
The overcurrent multiple on timberline road；
3.3) transmission line safety tolerance time is predicted
Take the highest of conducting wire rolling schedule design that running temperature is allowed to be route tolerance criterion, when measuring the safety tolerance of route in advance
Between Ts, expression is as follows:
Running temperature θ is allowed by highestmax, can be obtained conducting wire at such a temperature critical permission electric current relative to initial launch electric current
Multiple proportion formula are as follows:
When overcurrent is less than critical permission electric current, allow the ascending temperature time infinitely great；When overcurrent is greater than critical permission electricity
When stream, the bigger temperature rise of electric current allows the time will be smaller, and specific temperature rise allows time relationship as follows:
3.4) selection of full transmission line safety tolerance time
Pass through step 3.1) -3.3), prediction obtains N number of safe tolerance time value of N sections of transmission lines of electricity, and the safety of whole route is resistance to
Minimum value in N sections is taken by the time, it may be assumed that
Ts=min { ts1,ts2,…tsi…tsNI=1,2 ... N (8).
2. the transmission line of electricity active heat protection method according to claim 1 based on the prediction of electric current tolerance time, special
Sign is that temperature start-up criterion described in (2) step is the conductor temperature value θ that will be acquiredcWith conductor temperature initiation value θstartIt carries out
Compare, if being more than conductor temperature initiation value, protect starting, expression is as follows:
θc> θstart,θstart=kθθmax (1)
Wherein, kθFor temperature startup coefficient, 0.6-0.8, θ are takenmaxTaking the highest of conducting wire rolling schedule design allows running temperature；
The current start criterion is the line current information I that will be acquiredcWith current start value IstartIt is compared, if acquisition electricity
Flow valuve is more than current start value, then protects starting, expression is as follows:
Ic> Istart,Istart=kIIL.max (2)
Wherein, kIFor current start coefficient, 0.8-0.9, I are takenL.maxIndicate route maximum load current.
3. the transmission line of electricity active heat protection method according to claim 1 based on the prediction of electric current tolerance time, special
Sign is that temperature beyond limit operating criterion described in (5) step is the conductor temperature value θ that will be acquiredcWith conductor temperature action value θsetInto
Row compares, if being more than conductor temperature action value, protection act, expression is as follows:
θc> θset,θset=krelθmax (9)
In formula (9), krelFor safety factor, 1.05-1.1 is taken.
4. the transmission line of electricity active heat protection method according to claim 1 based on the prediction of electric current tolerance time, special
Sign is that the step 3.1) conducting wire is steel-cored aluminium strand, mc=ma·ca+ms·cs；Wherein, ma、msIt is led for unit length
The quality kg/m of aluminium, Steel material in line；ca、csFor the specific heat capacity of aluminium, Steel material, J/ (kg DEG C).
5. the transmission line of electricity active heat protection method according to claim 1 based on the prediction of electric current tolerance time, special
Sign is, when step (5) carries out trip protection, when timing time reaches TsMoment, while starting protection judgement is carried out, only arrive
Up to TsMoment, while the starting protection for meeting step (2) determines, just sends trip signal to line-breaker and scheduling system,
The route of excision temperature beyond limit in time.
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