CN113108929B - Power distribution network line switching decision method considering capacity increasing capacity of power transmission and transformation line - Google Patents
Power distribution network line switching decision method considering capacity increasing capacity of power transmission and transformation line Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
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- G—PHYSICS
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
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- G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
Abstract
The invention discloses a power distribution network line switching decision method considering capacity increasing capacity of a power transmission and transformation line, which comprises the following steps: s1, dividing a subsystem by taking a reactive compensation node as a decomposition point according to a reactive on-site balancing principle, and determining reactive compensation capacity based on inherent structural characteristics of a power grid in the subsystem so as to determine optimal compensation of system operation; s2, determining a capacity-increasing value delta L of the cable according to a maximum load value of a root load node of the dispatching center, and formulating a constraint condition Z which can be switched; s3, under the condition that the reactive power compensation capacity is limited, correcting and compensating by adopting a heuristic back-reckoning method; s3, calculating tide or measuring according to the current tide flow by using the net loss P Loss The minimum is the whole network compensation optimization for the target, and the final compensation scheme is determined by traversing the solution space; the scheme makes switching decision in the capacity-increasing range of the power cable, and ensures safe and efficient operation of the power line.
Description
Technical Field
The invention relates to the technical field of power transmission and distribution safety, in particular to a power distribution network line switching decision method considering capacity increase capacity of a power transmission and distribution line.
Background
With the development of the power grid, the power cable is widely applied to the power system, and the workload of management, detection and maintenance is also increased. Meanwhile, the urban electricity demand is rapidly increased, and higher requirements are put on the line capacity power supply reliability of the power cable. Reactive power compensation of a power distribution network is an effective and economical means for reducing the network loss of the power distribution system and improving the voltage level of the power grid, the purpose of the reactive power compensation is to realize the in-situ balance of reactive power, and when the self-compatible category of a line needs to be considered for switching of a node line, the current-carrying capacity of a power cable is an important dynamic parameter influenced by environmental conditions and loads in the operation of the cable, and the importance of the current-carrying capacity is related to the safe, reliable, economical and reasonable operation of the power transmission line and the service life problem of the cable. Therefore, the dynamic current-carrying capacity and the residual load capacity of the power cable are continuously monitored on line, information about the available load capacity of the cable is provided for power system schedulers, more reasonable decisions are made by the system schedulers in future load distribution, and the dynamic capacity increase of the power cable and the most full utilization of cable resources are realized.
The decisive factor for limiting the improvement of the current-carrying capacity of the cable is the maximum allowable temperature for the long-term operation of the cable, and in order to ensure the service life of the cable, the temperature of the wire core cannot exceed the long-term tolerance temperature (for example, the XLPE cable is 90 ℃). Once the core temperature exceeds this limit, the cable insulation will rapidly thermally age and thermal breakdown due to local overheating may even occur, inducing a power failure. Then the wire core is wrapped up by insulating layer, restrictive coating, armor, inner liner layer by layer, and the actual temperature of wire core is hardly detected to current temperature measuring device, generally predicts linear temperature through body surface temperature through mathematical modeling's mode, but mathematical modeling needs too many environmental factor of cable installation of considering, and model establishment is difficult, and the prediction effect often is less ideal.
Chinese patent, publication No.: CN107818239, publication date: the 3 rd 20 th 2018 discloses a method and a system for predicting the conductor temperature of a high-voltage cable, wherein the method comprises the following steps: establishing a coefficient matrix model of temperature prediction calculation of a cable conductor by using given cable structure data and a transient thermal circuit model; when a coefficient matrix is formed, performing assignment on the matrix by using cyclic assignment, and calculating the characteristic value and the characteristic vector of the matrix after the coefficient matrix is formed; constructing an integral function model according to the characteristic value and the characteristic vector, and integrating the integral function model to obtain a conductor temperature prediction model; detecting the current value of the high-voltage cable conductor, and obtaining a predicted conductor temperature value by using the conductor temperature prediction model according to the prediction time and the current as values. The method does not have a set of pre-detection equipment to truly collect cable temperature data and load data and establish a model based on the cable temperature data and the load data, and the obtained experimental data has ideal value conditions and lacks of reality.
Chinese patent, publication No.: CN104330659B, publication date: the 2017 2-15 day relates to a quasi-dynamic capacity-increasing method based on a cable heat transfer model, which is used for cable capacity increase in a calandria and comprises the following steps: 1) According to the working condition of the whole cable, a data acquisition system is established at the bottleneck cable section to measure the data of the same day; 2) According to the data of the bottleneck cable section measured by the data acquisition system on the current day, establishing and updating a cable heat transfer model of the bottleneck cable section on the next day by taking the day as a unit; 3) And estimating the current-carrying capacity of the cable to be compatibilized in the bottleneck cable section in the next day according to the cable heat transfer model of the bottleneck cable section in the next day, so as to realize cable compatibilization. According to the scheme, the relation between the cable heat and the load is monitored by taking the day as a unit, but more environmental factors are considered, for example, the soil thermal resistance, the coefficient metal sheath loss and the like need to be considered, so that the model is complicated to build.
Disclosure of Invention
The invention aims to solve the problem of potential safety hazards in power line switching decision-making caused by difficult detection of the real temperature of an underground cable, and provides a power distribution network line switching decision-making method considering capacity-increasing capacity of a power transmission and transformation line.
In order to achieve the technical purpose, the technical scheme provided by the invention is that a power distribution network line switching decision method considering capacity increase of a transmission and transformation line comprises the following steps:
s1, dividing a subsystem by taking a reactive compensation node as a decomposition point according to a reactive on-site balancing principle, and determining reactive compensation capacity based on inherent structural characteristics of a power grid in the subsystem so as to determine optimal compensation of system operation;
s2, the scheduling center determines a capacity-increasing value delta L of the cable according to the maximum load value of the load node, and formulates a constraint condition Z which can be switched;
s3, under the condition that the reactive power compensation capacity is limited, correcting and compensating by adopting a heuristic back-reckoning method;
s4, calculating the power flow by using the network loss P Loss The minimum is the whole network compensation optimization for the target, and the final compensation scheme is determined by traversing the solution space; the reactive compensation capacity is expressed by the following formula:
wherein F is LG (i, j) represents an i-th load node and a j-th reactive power supply node; n represents the number of subsystem load nodes, M represents the number of reactive power supply nodes, Q L (i) Represents the ith load node, Q G (j) Representing a j-th reactive power supply node;
the compatibilization value is delta L=Q Ld (i)-Q L (i) Wherein Q is Ld (i) Representing the maximum value of the loadable load of the ith line cable, constraint Z is therefore:when the load of the ith branch is increased, calculating the increasable capacity value of the ith line cable, and supplementing the capacity of the ith node by using the reactive capacity of the previous compensation node as an increment node by the scheduling center according to a heuristic push-back algorithm, wherein the capacity supplementing needs to meet constraint conditions.
F LG An interconnection matrix for representing load and power supply, which has the expression ofWherein Y is LL And Y LG An inter-node admittance matrix and an inter-node admittance matrix of the load-generator, respectively, the matrices being represented by a node admittance equation that distinguishes between the power supply node and the load node: />
Wherein,and->Injecting current and node voltage vectors for the power supply and load nodes, respectively, Y GG 、Y GL 、I LG And Y LL To distinguish each subarray of the node admittance matrix after the power supply node and the load node;
loss P of net Loss Expressed as:i epsilon j indicates that node i is directly connected with node j, g ij The conductance of the branch i-j is that the first and the last nodes of the branch are respectively a node i and a node j; />Is a node voltage vector; and minimizing the vector difference of the voltages at two ends of the line by using the corresponding value of the minimum network loss target, wherein the node voltage vector can be calculated according to the node admittance equation.
Before determining the optimal compensation of the system operation, test analysis is required to be carried out on the compatible characteristics of the branch cable, a characteristic model of the cable operation affected by the environment is built, and the building of the characteristic model comprises the following steps:
s11, constructing the environment temperature Te and the humidity Da of the cable operation through a pre-test system, and obtaining a function relation Tc=H (Tf, te and Da) of the surface temperature of the cable and the conductor temperature, wherein Tc is the conductor temperature, and Tf is the surface temperature of the cable;
s12, the control center acquires an environment value acquired by an environment monitor installed near the underground cable and a temperature value of a temperature monitor installed on the underground cable;
s13, the control center periodically reads real-time load Q of underground cable L (i) Correlating a cable load Li with a cable surface temperature Tf, an environment temperature Te and humidity Da obtained by a monitoring system to obtain sample data;
s14, constructing a function tc=g (Q L (i) Te, da) according to the current ambient temperature Te and humidity Da, obtaining the dynamic maximum load Q of the cable Ld (i) Dynamic maximum load Q Ld (i) So that G (Q) Ld (i) Te, da) =tc_max, which is the upper limit value of the cable operating temperature;
s15, the control center periodically outputs a dynamic maximum load Q Ld (i) The temperature is fed back to a dispatching center as a capacity-increasing upper limit, the control center calculates the conductor temperature Tc according to (Tf, te, da) periodically, if Tc>k·Tc_max, k is the safety factor, k<And 1, the control center gives an alarm to the dispatching center and instructs the dispatching center to reduce the load L of the cable.
In the scheme, a constant temperature environment is provided for a cable through a constant temperature measuring device in a testing system (wherein the temperature value of the constant temperature environment can be set according to the constant temperature measuring device) and is used for acquiring temperature data between a conductor (a battery core) and a surface of the cable, a functional relation model is built by adopting a neural network algorithm according to a plurality of groups of acquired environmental temperature Te, humidity Da, conductor temperature Tc and cable surface temperature Tf as samples, weight factors occupied by all factors are calculated according to the neural network algorithm, the environmental temperature Te, the humidity Da and the cable surface temperature Tf are used as input layers of the neural network model, the conductor temperature Tc is used as an output layer of the neural network, the weight factors in an hidden layer are obtained, and then the functional relation Tc=H (Tf, te, da) is obtained; then the control center reads the conductor load data, and a functional relation with the conductor temperature Tc, the ambient temperature Te and the humidity Da is established in the same way.
The power distribution network line switching decision system comprises a pre-test system, a monitoring system, a control center and a dispatching center, wherein the pre-test system constructs the environment temperature Te and the humidity Da of the cable operation to obtain the function relation Tc=H (Tf, te, da) of the cable surface temperature and the conductor temperature, tc is the conductor temperature, and Tf is the cable surface temperature;
the monitoring system comprises a temperature monitor and an environment monitor (the environment monitor detects the environment temperature and humidity of a low cable) which are distributed along the cable, the temperature monitor monitors the surface temperature of the cable, the environment monitor monitors the environment temperature Te and the humidity Da near the cable, and the temperature monitor and the environment monitor are connected with a control center;
the control center is in communication connection with the dispatching center and is used for analyzing and guiding the dispatching center to execute dispatching actions on the data acquired by the monitoring system;
the temperature monitor comprises a thermocouple temperature monitor which is arranged on an underground cable and used for measuring the surface temperature of the cable;
the pre-test system comprises a cable to be tested and a constant temperature measuring device for providing a constant temperature measuring environment for the cable to be tested; the constant temperature measuring device comprises a plurality of liquid injection heads arranged at two ends of a cable to be tested, a constant temperature pipe arranged between gaps of insulating layers of conductors in the cable and used for communicating the liquid injection heads at two ends, and a liquid injection pipe and a liquid outlet pipe which are arranged at two ends of the cable to be tested and respectively connected with the liquid injection heads; the liquid outlet pipe is communicated with the liquid injection pipe through a hot water pump; the liquid injection pipe is also provided with a temperature compensator for compensating the liquid temperature of the pipeline and a water pressure fine adjuster for adjusting the liquid flow of the compensating pipeline.
In the scheme, the target object suitable for the scheme is an underground cable, and because the real-time measurement of the battery core of the underground cable is inconvenient during operation, a pre-test system is required to be arranged to calculate and analyze in advance to obtain cable temperature characteristic data, the conductor temperature value of the cable can be predicted according to the cable surface temperature value actually measured on site, the capacity-increasing value which can be actually borne by the target cable can be calculated according to the relation between the established conductor temperature value and the cable load, and the safety of electric power capacity-increasing is ensured.
Preferably, the temperature compensator comprises a shell, a compensation cylinder, a locking pipe and a liquid supplementing pipe, wherein the shell is hermetically sleeved on the liquid injection pipe, the compensation cylinder is arranged in the shell and is vertically communicated with the liquid injection pipe, the locking pipe is vertically communicated with the compensation cylinder, and the liquid supplementing pipe is communicated with the compensation cylinder and the liquid injection pipe; the automatic compensation device is characterized in that a compensation spring connected with the end part of the compensation cylinder and a sliding block connected with the lower end of the compensation spring are arranged in the compensation cylinder, a locking spring connected with the end part of the locking tube and a locking block connected with the end part of the locking spring and used for locking the sliding block are arranged in the locking tube, a first annular temperature detector is arranged on the circumferential surface of a water inlet tube of the shell body of the liquid injection tube, a second annular temperature detector is arranged on the circumferential surface of a tube of a water outlet of the shell body of the liquid injection tube, the annular temperature detector is electrically connected with the detection end of the controller, and the control end of the controller is electrically connected with the locking spring and the compensation spring respectively.
In this scheme, because the hot water that the hot-water pump flows can dissipate at the in-process of annotating the liquid pipe circulation, consequently, in order to guarantee that the pipeline temperature that gets into cable insulating layer clearance is the default, need set up temperature compensating device at annotate the liquid mouth of pipe, first cyclic annular temperature detector sets up the entry at temperature compensator, second cyclic annular temperature detector sets up the export at temperature compensator, the measured value of first cyclic annular temperature detector and second cyclic annular temperature detector is obtained and the temperature difference is calculated to the controller (for 51 singlechip), control locking spring, through giving locking spring circular telegram and causing its shrink, make the slider can slide from top to bottom in the compensation section of thick bamboo, the controller is circular telegram for the compensation spring, on the one hand can make its shrink pour into the liquid pipe again into to water in the compensation section of thick bamboo through the liquid pipe of mending, make the velocity of flow diminish, on the other hand control the size of switch-on current causes the spring circular telegram heating, water heating in the compensation section of thick bamboo, reach temperature compensating effect.
Preferably, the water pressure fine adjuster comprises a substrate which is hermetically sleeved on the liquid injection pipe, a plurality of adjusting cylinders which are arranged in the machine body and are vertically communicated with the liquid injection pipe, an adjusting spring which is connected with the end part of the adjusting cylinders, and an adjusting slide block which is connected with the end part of the adjusting spring, wherein the liquid injection pipe is provided with a flow sensor which is used for detecting flow data of the liquid injection pipe at the outlet of the substrate, the flow sensor is electrically connected with the detection end of the controller, and a plurality of adjusting springs are electrically connected with the control end of the controller.
In this scheme, the controller acquires flow sensor's flow data, and the water flow that water pressure micromatic setting controlled the outflow makes the discharge of annotating the liquid pipe diminish in the liquid reposition of redundant personnel of annotating the liquid pipe to the adjustment section of thick bamboo through the shrink of controller control adjusting spring.
Preferably, the thermocouple temperature monitor comprises a control unit, a voltmeter, a current source, a resistor R0, a collecting belt and a plurality of loop wire belts, wherein the collecting belt comprises a rubber sheath, a positive wire, a negative wire and a grounding wire, the collecting belt is arranged in parallel with a cable, the loop wire belts comprise rubber loop belts, a puncture head, a detection circuit and a thermistor, the rubber loop belts are bound outside the cable in a surrounding manner, the thermistor is arranged between the rubber loop belts and the cable, the puncture head and the thermistor are connected with the detection circuit, the puncture head is used for puncturing the rubber sheath of the collecting belt, the puncture head is provided with three puncture heads, the three puncture heads are respectively connected with the positive wire, the negative wire and the grounding wire, the positive wire is connected with the resistor R0, the negative wire, the grounding wire, the negative pole of the voltmeter and the negative pole of the current source are grounded, and the voltmeter are connected with the control unit.
Preferably, the detection circuit includes a resistor R1, a resistor R3, a resistor R4, a resistor R5, an electronic switch K1 and an electronic switch K2, where the resistor R1 and the electronic switch K1 are connected in series to form a first detection arm, the thermistor Rf and the electronic switch K2 are connected in series to form a second detection arm, two ends of the first detection arm and the second detection arm are connected with a positive line and a negative line respectively, the resistor R3, the resistor R4 and the resistor R5 are connected in series to form a voltage dividing resistor string, the voltage dividing resistor string is connected between the positive line and a ground line, the resistor R3 is close to the positive line, the resistor R5 is close to the ground line, a control end of the electronic switch K1 is connected between the resistor R3 and the resistor R4, and a control end of the electronic switch K2 is connected between the resistor R4 and the resistor R5. The cable skin temperature value can be obtained through simple conversion by detecting the resistance value of the thermistor Rf, further the function relation Tc=H (Tf, te, da) is obtained to obtain the conductor temperature value, and finally the range of the power cable increasable capacity value is calculated.
Preferably, the thermocouple temperature monitor further comprises a cushion block fixedly connected with the rubber sheath of the collecting belt, and the cushion block is positioned between the rubber sheath of the collecting belt and the cable, so that a gap is formed between the rubber sheath and the cable. The rubber sheath and the cable have a gap to facilitate measuring the skin temperature value of the individual cable while facilitating heat dissipation.
Preferably, the thermocouple temperature monitor further comprises a support block positioned between the thermistor and the rubber annulus.
The invention has the beneficial effects that: a power distribution network line switching decision method considering capacity increasing capability of a power transmission and transformation line is characterized in that a pre-test system provides a test environment for a cable to obtain real measurement data, a functional relation among a conductor, a cable skin temperature value and a cable load is built, and then the cable skin temperature value is monitored in real time to obtain the conductor temperature value, so that an increasing range of power cable capacity increasing can be obtained, and safety and reliability of power capacity increasing are guaranteed.
Drawings
Fig. 1 is a structural view of a constant temperature measuring device of the present invention.
Fig. 2 is a structural view of the temperature compensator of the present invention.
Fig. 3 is a structural view of the hydraulic fine adjuster of the present invention.
Fig. 4 is a structural diagram of the cable to be tested of the present invention.
Fig. 5 is a schematic diagram of the power principle of the thermocouple temperature monitor according to the present invention.
Fig. 6 is a mounting structure view of the thermocouple temperature monitor according to the present invention.
Fig. 7 is a cross-sectional view of the thermocouple temperature monitor installation of the present invention.
The figure indicates: 100. cable, 101, jacket layer, 102, armor layer, 103, inner liner, 104, conductor, 105, insulation layer, 200, pipe, 301, head, 302, pipe, 303, pipe, 400, temperature compensator, 401, compensation spring, 402, slide plug, 403, compensation cylinder, 404, lock block, 405, lock spring, 406, lock tube, 407, fluid make-up tube, 408, housing, 409, first annular temperature detector, 410, second annular temperature detector, 500, hydraulic trimmer, 501, adjusting spring, 502, adjusting cylinder, 503, adjusting slider, 504, reservoir, 505, matrix, 506, flow sensor, 611, sink tape, 612, spacer, 613, negative wire, 614, ground wire, 615, positive wire, 621, loop tape, 622, thermistor, 623, puncture head, 624, support block, 700, hot water pump.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and examples, it being understood that the detailed description herein is merely a preferred embodiment of the present invention, which is intended to illustrate the present invention, and not to limit the scope of the invention, as all other embodiments obtained by those skilled in the art without making any inventive effort fall within the scope of the present invention.
Examples: a power distribution network line switching decision method considering capacity increasing capability of a power transmission and transformation line comprises the following steps: s1, dividing a subsystem by taking a reactive compensation node as a decomposition point according to a reactive on-site balancing principle, and determining reactive compensation capacity based on inherent structural characteristics of a power grid in the subsystem so as to determine optimal compensation of system operation;
s2, the scheduling center determines a capacity-increasing value delta L of the cable according to the maximum load value of the load node, and formulates a constraint condition Z which can be switched;
s3, under the condition that the reactive power compensation capacity is limited, correcting and compensating by adopting a heuristic back-reckoning method;
s4, calculating the power flow by using the network loss P Loss The minimum is the whole network compensation optimization for the target, and the final compensation scheme is determined by traversing the solution space; the reactive compensation capacity is expressed by the following formula:
wherein F is LG (i, j) represents an i-th load node and a j-th reactive power supply node; n represents the number of subsystem load nodes, M represents the number of reactive power supply nodes, Q L (i) Represents the ith load node, Q G (j) Representing a j-th reactive power supply node;
the compatibilization value is delta L=Q Ld (i)-Q L (i) Wherein Q is Ld (i) Representing the maximum value of the loadable load of the ith line cable, constraint Z is therefore:when the load of the ith branch is increased, calculating the increasable capacity value of the ith line cable, and supplementing the capacity of the ith node by using the reactive capacity of the previous compensation node as an increment node by the scheduling center according to a heuristic push-back algorithm, wherein the capacity supplementing needs to meet constraint conditions.
Before determining the optimal compensation of the system operation, test analysis is required to be carried out on the compatible characteristics of the branch cable, a characteristic model of the cable operation affected by the environment is built, and the building of the characteristic model comprises the following steps:
s11, constructing the environment temperature Te and the humidity Da of the cable operation through a pre-test system, and obtaining a function relation Tc=H (Tf, te and Da) of the surface temperature of the cable and the conductor temperature, wherein Tc is the conductor temperature, and Tf is the surface temperature of the cable;
s12, the control center acquires an environment value acquired by an environment monitor installed near the underground cable and a temperature value of a temperature monitor installed on the underground cable;
s13, the control center periodically reads real-time load Q of underground cable L (i) Correlating a cable load Li with a cable surface temperature Tf, an environment temperature Te and humidity Da obtained by a monitoring system to obtain sample data;
s14, constructing a function tc=g (Q L (i) Te, da) according to the current ambient temperature Te and humidity Da, obtaining the dynamic maximum load Q of the cable Ld (i) Dynamic maximum load Q Ld (i) So that G (Q) Ld (i) Te, da) =tc_max, which is the upper limit value of the cable operating temperature;
s15, the control center periodically outputs a dynamic maximum load Q Ld (i) The temperature is fed back to a dispatching center as a capacity-increasing upper limit, the control center calculates the conductor temperature Tc according to (Tf, te, da) periodically, if Tc>k is Tc_max, k is a safety factor, k<And 1, the control center gives an alarm to the dispatching center and instructs the dispatching center to reduce the load L of the cable.
In this embodiment, since a constant temperature environment is provided for the cable by the constant temperature measurement device in the testing system (wherein the temperature value of the constant temperature environment can be set according to the constant temperature measurement device), the constant temperature environment is used for collecting temperature data between the conductor (cell) and the surface of the cable, a functional relation model is built by using a neural network algorithm according to the collected multiple groups of environmental temperature Te, humidity Da, conductor temperature Tc and cable surface temperature Tf as samples, weight factors occupied by each factor are calculated according to the neural network algorithm, the environmental temperature Te, humidity Da and cable surface temperature Tf are used as input layers of the neural network model, the conductor temperature Tc is used as an output layer of the neural network, weight factors in hidden layers are obtained, and then a functional relation tc=h (Tf, te, da) is obtained; then the control center reads the conductor load data, and a functional relation with the conductor temperature Tc, the ambient temperature Te and the humidity Da is established in the same way.
The power distribution network line switching decision system comprises a pre-test system, a monitoring system, a control center and a dispatching center, wherein the pre-test system constructs the environment temperature Te and the humidity Da of the cable operation to obtain the function relation Tc=H (Tf, te, da) of the cable surface temperature and the conductor temperature, tc is the conductor temperature, and Tf is the cable surface temperature;
the monitoring system comprises a temperature monitor and an environment monitor which are distributed along the cable, wherein the temperature monitor monitors the surface temperature of the cable, the environment monitor monitors the ambient temperature Te and the humidity Da near the cable, and the temperature monitor and the environment monitor are connected with a control center;
the control center is in communication connection with the dispatching center and is used for analyzing and guiding the dispatching center to execute dispatching actions on the data acquired by the monitoring system;
the temperature monitor comprises a thermocouple temperature monitor which is arranged on an underground cable and used for measuring the surface temperature of the cable;
as shown in fig. 1, the pre-test system includes a constant temperature measurement device for providing a constant temperature measurement environment for a cable to be tested; the constant temperature measuring device comprises a plurality of liquid injection heads 301 arranged at two ends of a cable to be tested, a constant temperature pipe (not shown) arranged between gaps of insulating layers of conductors in the cable and used for communicating the liquid injection heads at two ends, a liquid injection pipe 302 and a liquid outlet pipe 303 which are arranged at two ends of the cable to be tested and respectively connected with the liquid injection heads; the liquid outlet pipe is communicated with the liquid injection pipe through a hot water pump 700; the liquid injection pipe is also provided with a temperature compensator 400 for compensating the liquid temperature of the pipeline and a water pressure fine adjuster 500 for adjusting the liquid flow of the compensating pipeline.
In this embodiment, the target object applicable to the scheme is an underground cable, and because the real-time measurement of the battery core of the underground cable is inconvenient during operation, a pre-test system needs to be set to calculate and analyze in advance to obtain cable temperature characteristic data, the conductor temperature value of the cable can be predicted according to the cable surface temperature value actually measured on site, and the capacity-increasing value actually carried by the target cable can be calculated according to the relation between the established conductor temperature value and the cable load, so that the safety of electric power capacity-increasing is ensured.
As shown in fig. 2, the temperature compensator comprises a housing 408, a compensation cylinder 403, a locking pipe 406 and a fluid supplementing pipe 407, wherein the housing 408 is hermetically sleeved on the fluid injecting pipe, the compensation cylinder 403 is arranged in the housing and is vertically communicated with the fluid injecting pipe, the locking pipe 406 is vertically communicated with the compensation cylinder, and the fluid supplementing pipe is communicated with the compensation cylinder and the fluid injecting pipe; the compensating cylinder is internally provided with a compensating spring 401 connected with the end part of the compensating cylinder and a sliding block 402 connected with the lower end of the compensating spring, the locking pipe is internally provided with a locking spring 405 connected with the end part of the locking pipe and a locking block 404 connected with the end part of the locking spring and used for locking the sliding block, the liquid injection pipe is provided with a first annular temperature detector 409 on the circumferential surface of a water inlet pipe of the shell, the liquid injection pipe is provided with a second annular temperature detector 410 on the circumferential surface of a water outlet pipe of the shell, the annular temperature detector is electrically connected with the detection end of the controller, and the control end of the controller is respectively electrically connected with the locking spring and the compensating spring.
In this embodiment, since heat of hot water flowing out of the hot water pump is dissipated during circulation of the liquid injection pipe, in order to ensure that the temperature of a pipeline entering a gap between cable insulation layers is a preset value, a temperature compensation device needs to be arranged at a liquid injection pipe orifice, a first annular temperature detector is arranged at an inlet of the temperature compensator, a second annular temperature detector is arranged at an outlet of the temperature compensator, a controller (a 51 single chip microcomputer) obtains measured values of the first annular temperature detector and the second annular temperature detector and calculates a temperature difference value, controls the locking spring, and enables the locking spring to shrink by electrifying the locking spring so that the sliding block can slide up and down in the compensation cylinder, and the controller electrifies the compensation spring.
As shown in fig. 3, the hydraulic fine adjuster includes a base 505 that is sealed and sleeved on a liquid injection pipe, a plurality of adjusting cylinders 502 that are arranged in the machine body and are vertically communicated with the liquid injection pipe, an adjusting spring 501 that is connected with the end of the adjusting cylinders, and an adjusting slide block 503 that is connected with the end of the adjusting spring, the liquid injection pipe is provided with a flow sensor 506 at the outlet of the base for detecting flow data of the liquid injection pipe, the flow sensor is electrically connected with the detection end of the controller, and the plurality of adjusting springs are electrically connected with the control end of the controller.
In this embodiment, the controller obtains the flow data of the flow sensor, the water pressure micro-regulator controls the flow of the water flowing out, and the controller controls the contraction of the adjusting spring to shunt the liquid of the liquid injection pipe to the liquid storage section 504 so that the water flow of the liquid injection pipe is reduced in the adjusting cylinder.
As shown in fig. 4, the cable to be tested includes a pipe 200 and a plurality of bundles of cables disposed in the pipe, each bundle of cables includes a plurality of bundles of cables independent from each other, the cables include a sheath layer 101, an armor layer 102, an inner liner layer 103, and a plurality of conductors 104 provided with the inner liner layer from outside to inside, and the outer layers of the conductors are all covered with an insulating layer 105.
The thermocouple temperature monitor comprises a control unit, a voltmeter, a current source, a resistor R0, a collecting belt 611 and a plurality of loop belts 621, wherein the collecting belt comprises a rubber sheath, an anode wire 615, a cathode wire 613 and a grounding wire 614, the collecting belt is arranged in parallel with the cable, the loop belts comprise rubber endless belts, a puncture head, a detection circuit and a thermistor 622, the rubber endless belts are bound outside the cable, the thermistor is arranged between the rubber endless belts and the cable, the puncture head 623 and the thermistor are connected with the detection circuit, the puncture head punctures the rubber sheath of the collecting belt, the puncture head is provided with three puncture heads, the three puncture heads are respectively connected with the anode wire, the cathode wire and the grounding wire, the anode wire is connected with the anode of the voltmeter and the current source, the cathode wire, the grounding wire, the cathode of the voltmeter and the cathode of the current source are grounded, and the voltmeter and the current source are connected with the control unit; as shown in fig. 7, the thermocouple temperature monitor further includes a pad 612 fixedly connected to the rubber sheath of the collecting belt, the pad being located between the rubber sheath of the collecting belt and the cable such that there is a gap between the rubber sheath and the cable; the thermocouple temperature monitor also includes a support block 624 positioned between the thermistor and the rubber cuff. The rubber sheath and the cable have a gap to facilitate independent measurement of the skin temperature value of the cable while facilitating heat dissipation.
As shown in fig. 5, the detection circuit includes a resistor R1, a resistor R3, a resistor R4, a resistor R5, an electronic switch K1 and an electronic switch K2, where the resistor R1 and the electronic switch K1 are connected in series to form a first detection arm, the thermistor Rf and the electronic switch K2 are connected in series to form a second detection arm, two ends of the first detection arm and the second detection arm are respectively connected with a positive line and a negative line, the resistor R3, the resistor R4 and the resistor R5 are connected in series to form a voltage division resistor string, the voltage division resistor string is connected between the positive line and a ground line, the resistor R3 is close to the positive line, the resistor R5 is close to the ground line, a control end of the electronic switch K1 is connected between the resistor R3 and the resistor R4, and a control end of the electronic switch K2 is connected between the resistor R4 and the resistor R5. The cable skin temperature value can be obtained through simple conversion by detecting the resistance value of the thermistor Rf, further the function relation Tc=H (Tf, te, da) is obtained to obtain the conductor temperature value, and finally the range of the power cable increasable capacity value is calculated.
The above embodiments are preferred embodiments of the power distribution network switching decision method considering capacity increase of the power transmission and transformation line according to the present invention, and are not limited to the specific embodiments, but the scope of the present invention includes equivalent changes made according to the shape and structure of the present invention.
Claims (9)
1. A power distribution network line switching decision method considering capacity increasing capability of a power transmission and transformation line is characterized by comprising the following steps:
s1, dividing a subsystem by taking a reactive compensation node as a decomposition point according to a reactive on-site balancing principle, and determining reactive compensation capacity based on inherent structural characteristics of a power grid in the subsystem so as to determine optimal compensation of system operation;
s2, the scheduling center determines a capacity-increasing value delta L of the cable according to the maximum load value of the load node, and formulates a constraint condition Z which can be switched;
s3, under the condition that the reactive power compensation capacity is limited, correcting and compensating by adopting a heuristic back-reckoning method;
s4, calculating the power flow by using the network loss P Loss The minimum is the whole network compensation optimization for the target, and the final compensation scheme is determined by traversing the solution space; the reactive compensation capacity is expressed by the following formula:
wherein F is LG (i, j) represents an i-th load node and a j-th reactive power supply node; n represents the number of subsystem load nodes, M represents the number of reactive power supply nodes, Q L (i) Represents the ith load node, Q G (j) Representing a j-th reactive power supply node;
the compatibilization value is delta L=Q Ld (i)-Q L (i) Wherein Q is Ld (i) Representing the maximum value of the loadable load of the ith line cable, constraint Z is therefore:when the load of the ith branch is increased, calculating the increasable capacity value of the ith line cable, and supplementing the capacity of the ith node by using the reactive capacity of the previous compensation node as an increment node by the scheduling center according to a heuristic push-back algorithm, wherein the capacity supplementing needs to meet constraint conditions.
2. The power distribution network line switching decision method considering capacity-increasing capability of a power transmission and transformation line according to claim 1, wherein test analysis is required to be performed on the capacity-increasing characteristics of branch cables before optimal compensation of system operation is determined, a characteristic model of the cable operation affected by environment is established, and the establishment of the characteristic model comprises the following steps:
s11, constructing the environment temperature Te and the humidity Da of the cable operation through a pre-test system, and obtaining a function relation Tc=H (Tf, te and Da) of the surface temperature of the cable and the conductor temperature, wherein Tc is the conductor temperature, and Tf is the surface temperature of the cable;
s12, the control center acquires an environment value acquired by an environment monitor installed near the underground cable and a temperature value of a temperature monitor installed on the underground cable;
s13, the control center periodically reads real-time load Q of underground cable L (i) Correlating a cable load Li with a cable surface temperature Tf, an environment temperature Te and humidity Da obtained by a monitoring system to obtain sample data;
s14, constructing a function tc=g (Q L (i) Te, da) according to the current ambient temperature Te and humidity Da, obtaining the dynamic maximum load Q of the cable Ld (i) Dynamic maximum load Q Ld (i) So that G (Q) Ld (i) Te, da) =tc_max, which is the upper limit value of the cable operating temperature;
s15, the control center periodically outputs a dynamic maximum load Q Ld (i) The temperature is fed back to a dispatching center as a capacity-increasing upper limit, the control center calculates the conductor temperature Tc according to (Tf, te, da) periodically, if Tc>k is Tc_max, k is a safety factor, k<And 1, the control center gives an alarm to the dispatching center and instructs the dispatching center to reduce the load L of the cable.
3. A power distribution network line switching decision system considering capacity increasing capability of a power transmission and transformation line, which is suitable for the power distribution network line switching decision method according to any one of claims 1-2, and is characterized in that the power distribution network line switching decision system comprises a pre-test system, a monitoring system, a control center and a dispatching center,
the pre-test system constructs the environment temperature Te and the humidity Da of the cable operation to obtain the function relation Tc=H (Tf, te, da) of the cable surface temperature and the conductor temperature, wherein Tc is the conductor temperature and Tf is the cable surface temperature;
the monitoring system comprises a temperature monitor and an environment monitor which are distributed along the cable, wherein the temperature monitor monitors the surface temperature of the cable, the environment monitor monitors the ambient temperature Te and the humidity Da near the cable, and the temperature monitor and the environment monitor are connected with a control center;
the control center is in communication connection with the dispatching center and is used for analyzing and guiding the dispatching center to execute dispatching actions on the data acquired by the monitoring system;
the temperature monitor comprises a thermocouple temperature monitor which is arranged on an underground cable and used for measuring the surface temperature of the cable;
the pre-test system comprises a cable to be tested and a constant temperature measuring device for providing a constant temperature measuring environment for the cable to be tested; the constant temperature measuring device comprises a plurality of liquid injection heads arranged at two ends of a cable to be tested, a constant temperature pipe arranged between gaps of insulating layers of conductors in the cable and used for communicating the liquid injection heads at two ends, and a liquid injection pipe and a liquid outlet pipe which are arranged at two ends of the cable to be tested and respectively connected with the liquid injection heads; the liquid outlet pipe is communicated with the liquid injection pipe through a hot water pump; the liquid injection pipe is also provided with a temperature compensator for compensating the liquid temperature of the pipeline and a water pressure fine adjuster for adjusting the liquid flow of the compensating pipeline.
4. A power distribution network line switching decision system taking capacity increase capability of a power transmission and transformation line into consideration according to claim 3,
the temperature compensator comprises a shell, a compensation cylinder, a locking pipe and a fluid supplementing pipe, wherein the shell is hermetically sleeved on the fluid injection pipe, the compensation cylinder is arranged in the shell and is vertically communicated with the fluid injection pipe, the locking pipe is vertically communicated with the compensation cylinder, and the fluid supplementing pipe is communicated with the compensation cylinder and the fluid injection pipe; the automatic compensation device is characterized in that a compensation spring connected with the end part of the compensation cylinder and a sliding block connected with the lower end of the compensation spring are arranged in the compensation cylinder, a locking spring connected with the end part of the locking tube and a locking block connected with the end part of the locking spring and used for locking the sliding block are arranged in the locking tube, a first annular temperature detector is arranged on the circumferential surface of a water inlet tube of the shell body of the liquid injection tube, a second annular temperature detector is arranged on the circumferential surface of a tube of a water outlet of the shell body of the liquid injection tube, the annular temperature detector is electrically connected with the detection end of the controller, and the control end of the controller is electrically connected with the locking spring and the compensation spring respectively.
5. A power distribution network line switching decision system taking capacity increase of a power transmission and transformation line into consideration according to claim 3 or 4,
the water pressure micromatic setting is including sealing the base member of cup jointing on annotating the liquid pipe, sets up a plurality of regulating cylinders of perpendicular intercommunication with annotating the liquid pipe in the organism, with regulating spring of regulating cylinder end connection, with regulating spring end connection's regulation slider, annotate the liquid pipe and be provided with the flow sensor who is used for detecting annotating liquid pipe flow data in the exit of base member, flow sensor and the detection end of controller, a plurality of regulating spring are connected with the control end electricity of controller.
6. A power distribution network line switching decision system taking capacity increase capability of a power transmission and transformation line into consideration according to claim 3,
thermocouple temperature monitor includes control unit, voltmeter, electric current source, resistance R0, gathers area and a plurality of ring line area, it includes rubber crust, positive pole line, negative pole line and earth connection to gather the area, it sets up with the cable parallel to gather the area, the ring line area includes rubber ring area, puncture head, detection circuitry and thermistor, the rubber ring area encircles and ties outside the cable, thermistor is located between rubber ring area and the cable, puncture head and thermistor all are connected with detection circuitry, puncture head all pierces the rubber crust that gathers the area, puncture head is equipped with three, three puncture head is connected with positive pole line, negative pole line and earth connection respectively, positive pole line is connected with resistance R0, and resistance R0 is connected with the positive pole of voltmeter and electric current source, and negative pole line, earth connection, voltmeter negative pole and the negative pole of electric current source all are grounded, voltmeter and electric current source all are connected with control unit.
7. The power distribution network line switching decision system considering capacity increasing capability of power transmission and transformation lines according to claim 6, wherein,
the detection circuit comprises a resistor R1, a resistor R3, a resistor R4, a resistor R5, an electronic switch K1 and an electronic switch K2, wherein the resistor R1 and the electronic switch K1 are connected in series to form a first detection arm, the thermistor Rf and the electronic switch K2 are connected in series to form a second detection arm, two ends of the first detection arm and two ends of the second detection arm are respectively connected with a positive line and a negative line, the resistor R3, the resistor R4 and the resistor R5 are connected in series to form a voltage dividing resistor string, the voltage dividing resistor string is connected between the positive line and a grounding line, the resistor R3 is close to the positive line, the resistor R5 is close to the grounding line, a control end of the electronic switch K1 is connected between the resistor R3 and the resistor R4, and a control end of the electronic switch K2 is connected between the resistor R4 and the resistor R5.
8. A power distribution network line switching decision system taking capacity increase capability of a power transmission and transformation line into consideration according to claim 6 or 7,
the thermocouple temperature monitor further comprises a cushion block, the cushion block is fixedly connected with the rubber sheath of the collecting belt, and the cushion block is located between the rubber sheath of the collecting belt and the cable, so that a gap is reserved between the rubber sheath and the cable.
9. The power distribution network line switching decision system considering capacity increasing capability of power transmission and transformation lines according to claim 6, wherein,
the thermocouple temperature monitor also comprises a support block, wherein the support block is positioned between the thermistor and the rubber endless belt.
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| JP2000088666A (en) * | 1998-09-11 | 2000-03-31 | Fujikura Ltd | Method and apparatus for calculating conductor temperature of power cable in underground duct |
| CN103138397A (en) * | 2012-11-19 | 2013-06-05 | 江西省电力科学研究院 | Method of dynamic capacity increasing of distribution network lines based on technology of internet of things |
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| CN104501992A (en) * | 2014-12-11 | 2015-04-08 | 无锡市锡容电力电器有限公司 | Reactor temperature-monitoring device for reactive compensation device |
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| US20110137483A1 (en) * | 2009-12-03 | 2011-06-09 | Alastar Jenkins | Method of real time remote control of transmission capacity of aerial power lines |
| US8965591B2 (en) * | 2012-02-16 | 2015-02-24 | General Electric Company | Regenerating electric power distribution switching plans based on changing power distribution network conditions |
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| JP2000088666A (en) * | 1998-09-11 | 2000-03-31 | Fujikura Ltd | Method and apparatus for calculating conductor temperature of power cable in underground duct |
| CN103138397A (en) * | 2012-11-19 | 2013-06-05 | 江西省电力科学研究院 | Method of dynamic capacity increasing of distribution network lines based on technology of internet of things |
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