CN113108929B - A distribution network line switching decision-making method considering the capacity increase capacity of power transmission and transformation lines - Google Patents

Abstract

The invention discloses a distribution network line switching decision-making method that considers the capacity increase capacity of power transmission and transformation lines, including the following steps: S1. According to the reactive power local balance principle, subsystems are divided using the reactive power compensation node as the decomposition point. And determine the reactive power compensation capacity based on the inherent structural characteristics of the power grid in the subsystem to determine the optimal compensation for system operation; S2. The maximum load value of the root load node of the dispatch center determines the increaseable capacity value ΔL of the cable, and formulates the switchable The constraint Z; S3. When the reactive power compensation capacity is limited, use the heuristic backcast algorithm to correct the compensation; S3. Calculate the power flow or measure the current power flow with the goal of minimizing the network loss P _Loss . Compensation optimization of the entire network traverses the solution space to determine the final compensation plan; the plan makes switching decisions within the capacity increase range of power cables, ensuring safe and efficient operation of power lines.

Description

A distribution network line switching decision-making method considering the capacity increase capacity of power transmission and transformation lines

Technical field

The present invention relates to the technical field of power transmission and distribution safety. Specifically, it relates to a distribution network line switching decision-making method that considers the capacity increase capacity of power transmission and transformation lines.

Background technique

With the development of the power grid, power cables are used more and more widely in power systems, and the workload of their management, inspection and maintenance is also increasing. At the same time, the rapid increase in urban electricity demand has put forward higher requirements for the line capacity and power supply reliability of power cables. Distribution network reactive power compensation is an effective and economical means to reduce distribution system network losses and increase grid voltage levels. The purpose of reactive power compensation is to achieve local balance of reactive power. When the switching of node lines is required Considering the scalable scope of the line itself, the ampacity of the power cable is an important dynamic parameter affected by environmental conditions and load during cable operation. Its importance involves the safety, reliability, economical and reasonable operation of the transmission line, and the cable life. Therefore, online continuous monitoring of the dynamic ampacity and residual load capacity of power cables provides power system dispatchers with information about the cable's available load capacity, which helps system dispatchers make more reasonable decisions in future load allocation. Decision-making to achieve dynamic capacity increase of power cables and maximize the utilization of cable resources.

The decisive factor that restricts the increase in cable carrying capacity is the maximum allowable temperature for long-term operation of the cable. To ensure the life of the cable, the core temperature cannot exceed the long-term withstand temperature (for example, 90°C for XLPE cable). Once the wire core temperature exceeds this limit, the cable insulation will rapidly thermally age, and thermal breakdown due to local overheating may even occur, inducing power supply accidents. Then the wire core is wrapped layer by layer by insulation layer, sheath layer, armor layer, and lining layer. It is difficult for existing temperature measurement devices to detect the true temperature of the wire core. It is usually through mathematical modeling through the body surface. Temperature prediction can predict linear temperature, but mathematical modeling needs to consider too many environmental factors of cable installation, making model establishment difficult, and the prediction effect is often not ideal.

Chinese patent, Publication No.: CN107818239, Publication date: March 20, 2018, discloses a method and system for predicting the temperature of high-voltage cable conductors. The method includes: using given cable structure data and a transient thermal path model, Establish a coefficient matrix model for temperature prediction calculation of cable conductors; when forming the coefficient matrix, use circular assignment to assign values to the matrix, and after forming the coefficient matrix, calculate the eigenvalues and eigenvectors of the matrix; according to the eigenvalues and eigenvectors Construct an integral function model, integrate the integral function model, and obtain the conductor temperature prediction model; detect the current value of the high-voltage cable conductor, use the conductor temperature prediction model and calculate the value according to the prediction time and the current to obtain the predicted conductor temperature value. This method does not have a set of pre-detection equipment to actually collect cable temperature data and load data and build a model based on it. The experimental data obtained have ideal values and lack authenticity.

Chinese patent, Publication No.: CN104330659B, Publication date: February 15, 2017, involves a quasi-dynamic capacitance increasing method based on a cable heat transfer model, which is used to increase the cable capacity inside the pipe, including the following steps: 1) According to According to the working conditions of the entire cable line, a data collection system is established in the bottleneck cable section to measure data on the day; 2) Based on the data of the bottleneck cable section measured by the data collection system on that day, establish and update the cables of the next day's bottleneck cable section on a daily basis. Heat transfer model; 3) Based on the cable heat transfer model of the bottleneck cable section the next day, estimate the carrying capacity of the cable to be increased in the bottleneck cable section the next day to achieve cable capacity increase. This solution monitors the relationship between cable heat and load on a daily basis, but it takes into account many environmental factors, such as soil thermal resistance, coefficient metal sheath loss, etc., which makes the model establishment complex.

Contents of the invention

The purpose of this invention is to solve the problem of potential safety hazards in power line switching decisions caused by the difficulty in detecting the true temperature of underground cables. It proposes a distribution network line switching decision-making method that considers the capacity increase capacity of power transmission and transformation lines. Minimum network loss is used as the objective function to formulate switching constraints. The pre-test system provides a test environment for the cable to obtain real measurement data. It establishes the functional relationship between the conductor, cable skin temperature value and cable load, and then monitors the cable skin temperature value in real time to obtain The conductor temperature value can then be used to obtain the range of power cable capacity expansion, ensuring the safety and reliability of power capacity expansion.

In order to achieve the above technical objectives, a technical solution provided by the present invention is a distribution network line switching decision-making method that considers the capacity increase capacity of power transmission and transformation lines, including the following steps:

S1. According to the reactive power in-situ balancing principle, the reactive power compensation node is used as the decomposition point to divide the subsystem, and the reactive power compensation capacity is determined within the subsystem based on the inherent structural characteristics of the power grid to determine the optimal compensation for system operation;

S2. The dispatch center determines the cable capacity increase value ΔL based on the maximum load value of the load node, and formulates the switching constraints Z;

S3. When the reactive power compensation capacity is limited, use a heuristic backcast algorithm for correction compensation;

S4. Calculate the power flow, optimize the entire network compensation with the goal of minimizing the network loss P _Loss , and traverse the solution space to determine the final compensation plan; the reactive power compensation capacity is expressed by the following formula:

Among them, F _LG (i, j) represents the i-th load node and j-th reactive power node; N represents the number of subsystem load nodes, M represents the number of reactive power supply nodes, Q _L (i) represents the i-th load Node, Q _G (j) represents the j-th reactive power node;

The scalable capacity value is ΔL=Q _Ld (i)-Q _L (i), where Q _Ld (i) represents the maximum load capacity of the i-th line cable. Therefore, the constraint Z is: When the load of the i-th branch becomes larger, the capacity increase value of the i-th line cable is calculated. The dispatch center uses the reactive power capacity of the previous compensation node as an incremental node to supplement the capacity of the i-th node based on the heuristic backcast algorithm. , whose capacity supplement needs to satisfy constraints.

F _LG represents the interconnection matrix of load and power supply, and its expression is Among them, Y _LL and Y _LG are the interconnection admittance matrix between load nodes and the interconnection admittance matrix between load and generator nodes respectively. This matrix can be represented by the node admittance equation after distinguishing the power node and the load node: />

in, and/> Inject current and node voltage vectors into the power supply and load nodes respectively. Y _GG , Y _GL , I _LG and Y _LL are the sub-arrays of the node admittance matrix after distinguishing the power supply node and the load node;

Network loss P _Loss is expressed as: i∈j means that node i and node j are directly connected, g _ij is the conductance of branch ij, and the first and last nodes of the branch are node i and node j respectively;/> is the node voltage vector; with the minimum network loss target, the corresponding value minimizes the vector difference of the voltages at both ends of the line, where the node voltage vector can be calculated according to the node admittance equation.

Before determining the optimal compensation for system operation, it is necessary to test and analyze the scalable characteristics of the branch cable, and establish a characteristic model of the cable operation affected by the environment. The establishment of the characteristic model includes the following steps:

S11. Construct the ambient temperature Te and humidity Da of the cable operation through the pre-test system, and obtain the functional relationship between the cable surface temperature and the conductor temperature Tc = H (Tf, Te, Da), where Tc is the conductor temperature and Tf is the cable surface temperature;

S12. The control center obtains the environmental values collected by the environmental monitor installed near the underground cable and the temperature value of the temperature monitor installed on the underground cable;

S13. The control center periodically reads the real-time load Q _L (i) of the underground cable, associates the cable load Li with the cable surface temperature Tf, ambient temperature Te and humidity Da obtained by the monitoring system to obtain sample data;

S14. After obtaining enough sample data, construct the function Tc=G(Q _L (i), Te, Da). Based on the current ambient temperature Te and humidity Da, obtain the dynamic maximum load Q _Ld (i) of the cable, and the dynamic maximum load Q _Ld (i) makes G(Q _Ld (i), Te, Da) = Tc_max, Tc_max is the upper limit of the cable operating temperature;

S15. The control center periodically feeds back the dynamic maximum load Q _Ld (i) to the dispatch center as the upper limit of capacity increase. The control center periodically calculates the conductor temperature Tc based on (Tf, Te, Da). If Tc>k·Tc_max, k is the safety factor. If k<1, the control center sends an alarm to the dispatching center and instructs the dispatching center to reduce the load L of the cable.

In this solution, since the test system provides a constant temperature environment for the cable through a constant temperature measuring device (the temperature value of the constant temperature environment can be set according to the constant temperature measuring device), it is used to collect the connection between the conductor (cell) and the surface of the cable. Temperature data, based on the collected multiple sets of ambient temperature Te, humidity Da, conductor temperature Tc and cable surface temperature Tf as samples, a neural network algorithm is used to establish a functional relationship model, and the weight factors of each factor are calculated according to the neural network algorithm, and the environment Temperature Te, humidity Da and cable surface temperature Tf are used as the input layer of the neural network model, and the conductor temperature Tc is used as the output layer of the neural network. The weight factor in the hidden layer is obtained, and then the functional relationship Tc=H(Tf, Te, Da); then read the conductor load data through the control center, and use the same method to establish the functional relationship with the conductor temperature Tc, ambient temperature Te and humidity Da.

A distribution network line switching decision-making system, including a pre-test system, a monitoring system, a control center and a dispatch center. The pre-test system constructs the ambient temperature Te and humidity Da of cable operation, and obtains the function of the cable surface temperature and the conductor temperature. The relationship Tc=H(Tf,Te,Da), where Tc is the conductor temperature and Tf is the cable surface temperature;

The monitoring system includes a temperature monitor and an environmental monitor arranged along the cable (the environmental monitor detects the ambient temperature and humidity of the cable), the temperature monitor monitors the surface temperature of the cable, and the environmental monitor monitors the ambient temperature Te and near the cable. The humidity, temperature monitor and environment monitor are all connected to the control center;

The control center is communicatively connected to the dispatch center and is used to analyze the data collected by the monitoring system and guide the dispatch center to perform dispatch actions;

The temperature monitor includes a thermocouple temperature monitor installed on the underground cable for measuring the surface temperature of the cable;

The pre-test system includes a cable to be tested and a constant temperature measurement device that provides a constant temperature measurement environment for the cable to be tested; the constant temperature measurement device includes a number of liquid injection heads arranged at both ends of the cable to be tested, and conductors arranged in the cable. There is a thermostatic pipe between the insulation layer gap for connecting the liquid injection heads at both ends, a liquid injection pipe and a liquid outlet pipe respectively connected to the liquid injection heads at both ends of the cable to be tested; the liquid outlet pipe and the liquid injection pipe pass through the hot water pump Connected; the liquid injection pipe is also provided with a temperature compensator for compensating the temperature of the liquid in the pipe and a water pressure trimmer for adjusting the liquid flow rate of the compensation pipe.

In this plan, the applicable target object of this plan is underground cables. Since it is inconvenient to measure the battery cores of underground cables in real time when they are running, it is necessary to set up a pre-test system to calculate and analyze in advance to obtain the cable temperature characteristic data. According to the actual measured cables on site The surface temperature value can predict the conductor temperature value of the cable. Based on the established relationship between the conductor temperature value and the cable load, the actual capacity increase value that the target cable can carry can be calculated, ensuring the safety of power capacity increase.

Preferably, the temperature compensator includes a shell that is sealingly connected to the liquid injection pipe, a compensation cylinder arranged in the housing and vertically connected to the liquid injection pipe, a locking tube that is vertically connected to the compensation cylinder, and a connecting tube that connects the compensation cylinder and the liquid injection pipe. The replenishing pipe of the liquid pipe; the compensation cylinder is provided with a compensation spring connected to the end of the compensation cylinder and a slider connected to the lower end of the compensation spring; the locking tube is provided with a locking spring connected to the end of the locking tube and a locking spring connected to the end of the locking tube; The spring end is connected to a locking block for locking the sliding block. The liquid injection pipe is provided with a first annular temperature detector on the peripheral surface of the water inlet pipe of the housing. The liquid injection pipe is located at the water outlet of the housing. A second annular temperature detector is provided on the circumferential surface of the tube. The annular temperature detector is electrically connected to the detection end of the controller. The control end of the controller is electrically connected to the locking spring and the compensation spring respectively.

In this solution, since the hot water flowing out of the hot water pump will dissipate heat during the flow of the liquid injection pipe, in order to ensure that the temperature of the pipe entering the gap between the cable insulation layers is the preset value, a temperature compensation needs to be set at the liquid injection pipe mouth. device, the first annular temperature detector is set at the entrance of the temperature compensator, the second annular temperature detector is set at the outlet of the temperature compensator, the controller (51 microcontroller) obtains the first annular temperature detector and the second The measured value of the annular temperature detector is used to calculate the temperature difference, and the locking spring is controlled. By energizing the locking spring, it causes it to shrink, so that the slider can slide up and down in the compensation cylinder. The controller energizes the compensation spring, which on the one hand can make it The contraction re-injects the water in the compensation cylinder into the liquid injection pipe through the liquid replenishing pipe, making the flow rate smaller. On the other hand, controlling the size of the conduction current causes the spring to be energized and heated, heating the water in the compensation cylinder to achieve temperature compensation.

Preferably, the hydraulic fine adjuster includes a base body that is sealed and sleeved on the liquid injection pipe, a number of adjustment barrels arranged in the body and vertically connected to the liquid injection pipe, an adjustment spring connected to the end of the adjustment barrel, and an adjustment spring. The adjusting slider is connected at the end. The liquid injection pipe is provided with a flow sensor for detecting the flow data of the liquid injection pipe at the outlet of the base body. The flow sensor is connected to the detection end of the controller, and several adjusting springs are connected to the controller's detection end. The control terminal is electrically connected.

In this solution, the controller obtains the flow data from the flow sensor, and the water pressure trimmer controls the outflow water flow. The controller controls the contraction of the adjusting spring to shunt the liquid in the liquid injection pipe into the regulating cylinder, so that the water flow rate in the liquid injection pipe changes. Small.

Preferably, the thermocouple temperature monitor includes a control unit, a voltmeter, a current source, a resistor R0, a collection belt and several loop wire belts. The collection belt includes a rubber sheath, a positive wire, a negative wire and a ground wire. The collection belt is arranged parallel to the cable. The loop belt includes a rubber loop belt, a puncture head, a detection circuit and a thermistor. The rubber loop belt is wrapped around the cable and the thermistor is located between the rubber loop belt and the cable. , the puncture head and the thermistor are both connected to the detection circuit, the puncture head pierces the rubber outer skin of the collection belt, there are three puncture heads, and the three puncture heads are respectively connected to the positive wire, the negative wire and the ground wire. connection, the positive line is connected to the resistor R0, the resistor R0 is connected to the positive electrode of the voltmeter and the current source, the negative line, the ground wire, the negative electrode of the voltmeter and the negative electrode of the current source are all grounded, and the voltmeter and current source are connected to the control unit connection.

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. The resistor R1 and the electronic switch K1 are connected in series to form the first detection arm, and the thermistor Rf is connected in series with the electronic switch K2. The second detection arm is formed. Both ends of the first detection arm and the second detection arm are connected to the positive line and the negative line respectively. Resistors R3, R4 and R5 are connected in series to form a voltage dividing resistor string. The voltage dividing resistor string is connected to the positive line and the negative line. Between the ground wires, resistor R3 is close to the positive wire, resistor R5 is close to the ground wire, the control terminal of electronic switch K1 is connected between resistor R3 and resistor R4, and the control terminal of electronic switch K2 is connected between resistor R4 and resistor R5. By detecting the resistance of the thermistor Rf, the cable skin temperature value can be known through simple conversion, and then the functional relationship Tc = H (Tf, Te, Da) can be used to obtain the temperature value of the conductor, and finally the increase in capacity of the power cable can be calculated. scope.

Preferably, the thermocouple temperature monitor further includes a pad, which is fixedly connected to the rubber sheath of the collection belt, and is located between the rubber sheath of the collection belt and the cable, so that there is a gap between the rubber sheath and the cable. Has gaps. There is a gap between the rubber sheath and the cable to facilitate the measurement of skin temperature values of independent cables and to help dissipate heat.

Preferably, the thermocouple temperature monitor further includes a support block located between the thermistor and the rubber ring.

The beneficial effects of the present invention: a distribution network line switching decision-making method that considers the capacity expansion capacity of power transmission and transformation lines. The pre-test system provides a test environment for the cable to obtain real measurement data to establish conductor and cable skin temperature values and cable Functional relationship of the load, and then monitor the cable skin temperature value in real time to obtain the conductor temperature value, and then obtain the increaseable range of the power cable capacity, ensuring the safety and reliability of the power capacity increase.

Description of the drawings

Figure 1 is a structural diagram of the constant temperature measuring device of the present invention.

Figure 2 is a structural diagram of the temperature compensator of the present invention.

Figure 3 is a structural diagram of the water pressure trimmer of the present invention.

Figure 4 is a structural diagram of the cable to be tested according to the present invention.

Figure 5 is a schematic diagram of the electrical principle of the thermocouple temperature monitor of the present invention.

Figure 6 is an installation structural diagram of the thermocouple temperature monitor of the present invention.

Figure 7 is a cross-sectional view of the installation of the thermocouple temperature monitor of the present invention.

Marking instructions in the figure: 100. Cable, 101. Sheath layer, 102. Armor layer, 103. Lining layer, 104. Conductor, 105. Insulation layer, 200. Pipe, 301. Liquid injection head, 302. Liquid injection Pipe, 303. Liquid outlet pipe, 400. Temperature compensator, 401. Compensation spring, 402. Slide plug, 403. Compensation cylinder, 404. Locking block, 405. Locking spring, 406. Locking pipe, 407. Liquid filling pipe, 408 , shell, 409, first annular temperature detector, 410, second annular temperature detector, 500, water pressure trimmer, 501, adjustment spring, 502, adjustment cylinder, 503, adjustment slider, 504, storage Liquid section, 505, matrix, 506, flow sensor, 611, collection belt, 612, spacer, 613, negative wire, 614, ground wire, 615, positive wire, 621, loop belt, 622, thermistor, 623, Puncture head, 624, support block, 700, hot water pump.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific implementation described here is only one of the best embodiments of the present invention. The embodiments are only used to explain the present invention and do not limit the scope of protection of the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

Embodiment: A distribution network line switching decision-making method that considers the capacity expansion capacity of power transmission and transformation lines, including the following steps: S1. According to the reactive power local balancing principle, divide the subsystems with the reactive power compensation node as the decomposition point, and Determine the reactive power compensation capacity within the subsystem based on the inherent structural characteristics of the power grid to determine the optimal compensation for system operation;

S2. The dispatch center determines the cable capacity increase value ΔL based on the maximum load value of the load node, and formulates the switching constraints Z;

S3. When the reactive power compensation capacity is limited, use a heuristic backcast algorithm for correction compensation;

S4. Calculate the power flow, optimize the entire network compensation with the goal of minimizing the network loss P _Loss , and traverse the solution space to determine the final compensation plan; the reactive power compensation capacity is expressed by the following formula:

Among them, F _LG (i, j) represents the i-th load node and j-th reactive power node; N represents the number of subsystem load nodes, M represents the number of reactive power supply nodes, Q _L (i) represents the i-th load Node, Q _G (j) represents the j-th reactive power node;

The scalable capacity value is ΔL=Q _Ld (i)-Q _L (i), where Q _Ld (i) represents the maximum load capacity of the i-th line cable. Therefore, the constraint Z is: When the load of the i-th branch becomes larger, the capacity increase value of the i-th line and cable is calculated. The dispatch center uses the reactive power capacity of the previous compensation node as an incremental node to supplement the capacity of the i-th node based on the heuristic backcast algorithm. , whose capacity supplement needs to satisfy constraints.

Before determining the optimal compensation for system operation, it is necessary to test and analyze the scalable characteristics of the branch cable, and establish a characteristic model of the cable operation affected by the environment. The establishment of the characteristic model includes the following steps:

S11. Construct the ambient temperature Te and humidity Da of the cable operation through the pre-test system, and obtain the functional relationship between the cable surface temperature and the conductor temperature Tc = H (Tf, Te, Da), where Tc is the conductor temperature and Tf is the cable surface temperature;

S12. The control center obtains the environmental values collected by the environmental monitor installed near the underground cable and the temperature value of the temperature monitor installed on the underground cable;

S13. The control center periodically reads the real-time load Q _L (i) of the underground cable, associates the cable load Li with the cable surface temperature Tf, ambient temperature Te and humidity Da obtained by the monitoring system to obtain sample data;

S14. After obtaining enough sample data, construct the function Tc=G(Q _L (i), Te, Da). Based on the current ambient temperature Te and humidity Da, obtain the dynamic maximum load Q _Ld (i) of the cable, and the dynamic maximum load Q _Ld (i) makes G(Q _Ld (i), Te, Da) = Tc_max, Tc_max is the upper limit of the cable operating temperature;

S15. The control center periodically feeds back the dynamic maximum load Q _Ld (i) to the dispatch center as the upper limit of capacity increase. The control center periodically calculates the conductor temperature Tc based on (Tf, Te, Da). If Tc>k·Tc_max, k is the safety factor. If k<1, the control center sends an alarm to the dispatching center and instructs the dispatching center to reduce the load L of the cable.

In this embodiment, since the test system provides a constant temperature environment for the cable through a constant temperature measuring device (the temperature value of the constant temperature environment can be set according to the constant temperature measuring device), it is used to collect the relationship between the conductor (cell) and the surface of the cable. Based on the collected temperature data between multiple sets of ambient temperature Te, humidity Da, conductor temperature Tc and cable surface temperature Tf as samples, a neural network algorithm is used to establish a functional relationship model, and the weight factors of each factor are calculated according to the neural network algorithm. The ambient temperature Te, humidity Da and cable surface temperature Tf are used as the input layer of the neural network model, and the conductor temperature Tc is used as the output layer of the neural network. The weight factor in the hidden layer is obtained, and then the functional relationship Tc=H(Tf , Te, Da); then read the conductor load data through the control center, and use the same method to establish the functional relationship with the conductor temperature Tc, ambient temperature Te and humidity Da.

A distribution network line switching decision-making system, including a pre-test system, a monitoring system, a control center and a dispatch center. The pre-test system constructs the ambient temperature Te and humidity Da of cable operation, and obtains the function of the cable surface temperature and the conductor temperature. The relationship Tc=H(Tf,Te,Da), where Tc is the conductor temperature and Tf is the cable surface temperature;

The monitoring system includes a temperature monitor and an environmental monitor arranged along the cable. The temperature monitor monitors the surface temperature of the cable. The environmental monitor monitors the ambient temperature Te and humidity Da near the cable. The temperature monitor and the environmental monitor are both connected to the control center. connect;

The control center is communicatively connected to the dispatch center and is used to analyze the data collected by the monitoring system and guide the dispatch center to perform dispatch actions;

The temperature monitor includes a thermocouple temperature monitor installed on the underground cable for measuring the surface temperature of the cable;

As shown in Figure 1, the pre-test system includes a cable to be tested and a constant temperature measurement device that provides a constant temperature measurement environment for the cable to be tested; the constant temperature measurement device includes a number of liquid injection heads 301 arranged at both ends of the cable to be tested. A thermostatic tube (not shown) is provided between the conductor insulation layer gaps in the cable for connecting the liquid injection heads at both ends, and a liquid injection pipe 302 and a liquid outlet pipe are provided at both ends of the cable to be tested and are respectively connected to the liquid injection heads. 303; The liquid outlet pipe and the liquid injection pipe are connected through a hot water pump 700; the liquid injection pipe is also provided with a temperature compensator 400 for compensating the pipeline liquid temperature and a hydraulic pressure trimmer 500 for adjusting the compensation pipeline liquid flow rate. .

In this embodiment, the applicable target object of this solution is underground cables. Since it is inconvenient to measure the battery cores of underground cables in real time when they are running, a pre-test system needs to be set up to calculate and analyze in advance to obtain the cable temperature characteristic data. According to the actual cable measurements on site The cable surface temperature value can predict the conductor temperature value of the cable. Based on the established relationship between the conductor temperature value and the cable load, the actual capacity increase value that the target cable can carry can be calculated, ensuring the safety of power capacity increase.

As shown in Figure 2, the temperature compensator includes a housing 408 that is sealed and connected to the liquid injection pipe, a compensation cylinder 403 arranged in the housing and vertically connected to the liquid injection pipe, and a locking tube 406 that is vertically connected to the compensation cylinder. And a liquid replenishing pipe 407 that connects the compensation cylinder and the liquid injection pipe; the compensation cylinder is provided with a compensation spring 401 connected to the end of the compensation cylinder and a slider 402 connected to the lower end of the compensation spring; the locking tube is provided with a locking tube The end of the locking spring 405 is connected and the end of the locking spring is connected to the locking block 404 for locking the sliding block. The liquid injection pipe is provided with a first annular temperature detector 409 on the peripheral surface of the water inlet pipe of the housing. , the liquid injection pipe is provided with a second annular temperature detector 410 on the peripheral surface of the water outlet of the housing, the annular temperature detector is electrically connected to the detection end of the controller, and the control of the controller The ends are electrically connected to the locking spring and the compensation spring respectively.

In this embodiment, since the heat of the hot water flowing out of the hot water pump will be dissipated during the circulation of the liquid injection pipe, in order to ensure that the temperature of the pipe entering the gap between the cable insulation layers is the preset value, it is necessary to set the temperature at the liquid injection pipe mouth Compensation device, the first annular temperature detector is set at the inlet of the temperature compensator, the second annular temperature detector is set at the outlet of the temperature compensator, the controller (51 single chip microcomputer) obtains the first annular temperature detector and the third annular temperature detector. The measured value of the two-ring temperature detector is used to calculate the temperature difference, and the locking spring is controlled. By energizing the locking spring, it causes it to shrink, so that the slider can slide up and down in the compensation cylinder. The controller energizes the compensation spring. On the one hand, it can make the Its search re-injects the water body in the compensation cylinder into the liquid injection pipe through the liquid replenishing pipe. On the other hand, it controls the size of the conduction current to cause the spring to be energized and heated, heating the water body in the compensation cylinder to achieve the effect of temperature compensation.

As shown in Figure 3, the hydraulic fine adjuster includes a base body 505 that is sealed and sleeved on the liquid injection pipe, a number of adjustment barrels 502 arranged in the body and vertically connected to the liquid injection pipe, and an adjustment barrel connected to the end of the adjustment barrel. Spring 501 and an adjustment slider 503 connected to the end of the adjustment spring. The liquid injection pipe is provided with a flow sensor 506 for detecting the flow data of the liquid injection pipe at the outlet of the base body. The flow sensor is connected to the detection end of the controller. Several adjusting springs are electrically connected to the control terminal of the controller.

In this embodiment, the controller obtains the flow data of the flow sensor, the water pressure trimmer controls the outflow water flow, and the controller controls the contraction of the adjustment spring to shunt the liquid in the liquid injection pipe to the liquid storage section 504 so that the injection pipe is filled with water. The water flow in the liquid pipe becomes smaller.

As shown in Figure 4, the cable to be tested includes a pipeline 200 and several bundles of cables arranged in the pipeline. Each bundle of cables includes several independent bundles of cables, and the cables include sheaths from outside to inside. Layer 101, armor layer 102, lining layer 103 and several conductors 104 with lining layers, the outer layers of the conductors are all covered with insulating layers 105.

The thermocouple temperature monitor includes a control unit, a voltmeter, a current source, a resistor R0, a collection belt 611 and several loop belts 621. As shown in Figure 6, the collection belt includes a rubber sheath, a positive wire 615, and a negative wire. 613 and ground wire 614. The collection belt is arranged parallel to the cable. The loop belt includes a rubber ring belt, a puncture head, a detection circuit and a thermistor 622. The rubber ring belt is tied around the outside of the cable, and the thermosensitive The resistor is located between the rubber ring belt and the cable. The puncture head 623 and the thermistor are both connected to the detection circuit. The puncture heads pierce the rubber outer skin of the collection belt. There are three puncture heads. There are three puncture heads. They are respectively connected to the positive wire, the negative wire and the ground wire. The positive wire is connected to the resistor R0. The resistor R0 is connected to the positive electrode of the voltmeter and the current source. The negative wire, the ground wire, the negative electrode of the voltmeter and the negative electrode of the current source are all grounded. The voltmeter and current source are both connected to the control unit; as shown in Figure 7, the thermocouple temperature monitor also includes a pad 612, which is fixedly connected to the rubber outer skin of the collection belt, and is located at Between the rubber sheath of the collection belt and the cable, there is a gap between the rubber sheath and the cable; the thermocouple temperature monitor also includes a support block 624, which is located between the thermistor and the rubber ring band. There is a gap between the rubber sheath and the cable to facilitate independent measurement of the cable's skin temperature and to help dissipate heat.

As shown in Figure 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. The resistor R1 and the electronic switch K1 are connected in series to form the first detection arm. The thermistor Rf is connected to the electronic switch K2. The switch K2 is connected in series to form the second detection arm. Both ends of the first detection arm and the second detection arm are connected to the positive line and the 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 to Between the positive line and the ground wire, resistor R3 is close to the positive line, resistor R5 is close to the ground wire, the control end of electronic switch K1 is connected between resistor R3 and resistor R4, and the control end of electronic switch K2 is connected between resistor R4 and resistor R5. between. By detecting the resistance of the thermistor Rf, the cable skin temperature value can be known through simple conversion, and then the functional relationship Tc = H (Tf, Te, Da) can be used to obtain the temperature value of the conductor, and finally the increase in capacity of the power cable can be calculated. scope.

The above-mentioned specific implementation modes are the preferred implementation modes of the present invention for a distribution network line switching decision-making method that considers the capacity increase capacity of power transmission and transformation lines, and are not intended to limit the specific implementation scope of the present invention. The scope of the present invention is Including but not limited to this specific embodiment, all equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope 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.