CN110490405B - Transformer energy efficiency evaluation analysis system - Google Patents
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Abstract
The invention discloses a transformer energy efficiency evaluation and analysis system which comprises an intelligent electrical CAD platform and a transformer energy efficiency evaluation and analysis calculation model in data connection with the intelligent electrical CAD platform; the transformer energy efficiency evaluation analysis and calculation model specifically comprises a theoretical line loss calculation module, a statistical line loss calculation module, a line loss analysis module, a transformer energy efficiency evaluation analysis module, a static evaluation and loss reduction decision module and a dynamic evaluation and loss reduction decision module. The invention constructs a transformer energy efficiency evaluation analysis calculation model based on an intelligent electrical CAD graphic platform, can effectively solve the difference existing in China due to the fact that the breadth of the country is vast and the power distribution networks in different areas are in different development stages, does not need to use actual manual on-site information acquisition, analysis comparison, evaluation calculation, greatly saves manpower and material resources, improves the economic benefit of power supply enterprises, simultaneously conforms to the current national low-carbon economic development target, and has considerable social benefit.
Description
Technical Field
The invention belongs to the technical field of power distribution, and particularly relates to a transformer energy efficiency evaluation and analysis system.
Background
With the progress and development of science and technology, under the condition of ensuring power supply capacity and power supply safety, the problems of minimizing the network loss of a power distribution network and improving the energy efficiency level of the power distribution network as much as possible are continuously researched and broken through in the current power departments and the power industry. However, in the current research level, the existing power distribution network energy efficiency evaluation method is rough and lacks pertinence.
According to statistics, the loss ratio of a power transmission network of 220kV or more, a high-voltage distribution network of 110kV (66 kV and 35 kV) and a medium-low voltage distribution network of 10kV or less is 10 percent to 15 percent to 75 percent, and the loss of the medium-low voltage distribution network accounts for 3/4 of the loss of the whole network. Meanwhile, according to the approximate composition proportion of the power grid losses of different areas, about one quarter of the losses in the power transmission system and three quarters of the losses in the power distribution system can be measured. The electric energy loss of the high-voltage transmission line and the high-voltage transformer is generally lower than 10%, and the loss of the medium-low voltage distribution system (comprising a medium-voltage line, a public distribution transformer and a low-voltage line) accounts for more than 70%, so the medium-low voltage distribution system is the important factor in saving energy and reducing loss of a power grid.
As one of core devices for power grid operation, in recent years, the nation has made higher requirements on energy efficiency indexes of transformers, and optimization research problems of transformer use are more and more concerned by relevant departments such as electric power, industry, agriculture and the like. In order to ensure that the transformer can fully play the performance role in the process of serving the power system, and simultaneously run more safely, reliably and economically, research on important measures of energy conservation and emission reduction of the transformer is indispensable. Internationally, a plurality of countries have already introduced relevant policies for improving the energy efficiency of transformers: in 1998, the united states initiated the "energy efficiency star transformer program"; in 2005, the european union implemented "distribution transformer promotion partner program"; in 2006, japan began implementing a "transformer energy efficiency leader program". As a domestic power service industry, the transformer is a responsibility and obligation for energy conservation, loss reduction and efficient utilization of the transformer.
At present, the method for evaluating the energy efficiency of the power distribution network is mainly to evaluate according to the statistical comprehensive line loss rate of the power distribution network, perform corresponding line splitting and distribution area statistical line loss analysis on a medium-low voltage power distribution network, and evaluate according to static parameters (power supply radius, line diameter model and the like) of the power distribution network in partial areas. However, because the breadth of our country is broad and affected by different social and economic development levels in different regions, and the power distribution network is in different development stages, great differences exist, such as differences of power distribution networks in different regions in China, differences of regions, differences of urban rural networks, differences of development levels, and influences of factors such as urbanization processes, business expansion projects, line improvement and the like, and great difficulty is brought to energy efficiency evaluation of the power distribution network. In view of the above, it is harder to focus on energy efficiency evaluation and analysis for transformers, and factors to be considered are numerous and disorderly, and the operability of the experiment is extremely low.
In the current urban and rural power grid transformation, the problem of loss reduction gradually draws attention from power supply enterprises, and is listed as one of the problems to be mainly solved in power grid transformation. However, in the conventional measures for increasing supply and reducing loss (such as energy-saving transformers, improving reactive compensation, increasing the cross section of a wire and the like) adopted in the two-network transformation, along with the current year-by-year increase of the load of the power distribution network, the loss reduction of the power distribution network gradually enters the bottleneck, and particularly, the situations of high loss, unqualified user side voltage and serious overload phenomenon still generally exist at the time of peak load. Therefore, for the research on energy conservation and consumption reduction of the power distribution network, the economic benefit of power supply enterprises can be improved, the current national low-carbon economic development target is met, and considerable social benefit is achieved.
Disclosure of Invention
The invention mainly aims to provide a transformer energy efficiency evaluation and analysis system, and aims to solve the technical problems of roughness, lack of pertinence and blindness, lagging and lacking of transformer energy efficiency evaluation technology and the like of the existing power distribution network energy efficiency evaluation method.
In order to achieve the purpose, the invention provides a transformer energy efficiency evaluation analysis system which comprises an intelligent electrical CAD platform and a transformer energy efficiency evaluation analysis calculation model in data connection with the intelligent electrical CAD platform;
the intelligent electrical CAD platform is used for drawing a full-voltage-grade power grid graph according to set electrical component parameters, and automatically converting a graph component and a mathematical model by using a graph-model integration technology and a structure combining the graph and data;
the transformer energy efficiency evaluation analysis calculation model is used for maximizing the energy efficiency of a medium-low voltage distribution network into a target function under the condition of meeting the power supply capacity and reliability constraints according to a network topological structure, load measurement data and investment cost data, and performing static energy efficiency evaluation, dynamic energy consumption evaluation and technical and economic evaluation of the transformer by taking a medium-voltage distribution line, a distribution transformer and a low-voltage distribution area as boundary adjustment.
Further, the transformer energy efficiency evaluation analysis calculation model specifically comprises a theoretical line loss calculation module, a statistical line loss calculation module, a line loss analysis module, a transformer energy efficiency evaluation analysis module, a static evaluation and loss reduction decision module and a dynamic evaluation and loss reduction decision module.
Furthermore, the statistical line loss calculation module is used for extracting electric quantity data from the electric power automation system and performing line loss calculation of classification, voltage division, branching and distribution areas, wherein the calculated transformer loss is expressed as
ΔP Z ＝ΔP+KQΔQ
Wherein, Δ P Z Represents the integrated power loss, Δ P represents the active loss, Δ Q represents the reactive loss, and KQ represents the reactive economic equivalent;
calculating the loss electric quantity of the transformer as
Loss electric quantity = no-load loss power supply time + monthly power consumption copper loss coefficient;
calculating the total power loss of the transformer is expressed as
ΔP T ＝P Fe +P Cu
Wherein, Δ P T Representing the total power loss, P, of the transformer Fe Representing the eddy current loss, P, of the excitation branch Cu Representing the resistive losses of the transformer coil.
Further, the theoretical total power loss of the transformer calculated by the theoretical line loss calculating module is expressed as
Wherein, Δ P Tunbalance Representing the theoretical total power loss, P, of the transformer 0 Denotes no-load loss, P k Represents the load loss, I 0 Indicating the circulating current of zero-sequence current at the high-voltage side, I A ,I B ,I C Representing the three-phase current of the transformer, I n Representing the transformer core current.
Further, the transformer energy efficiency evaluation analysis module is used for analyzing the influence on the transformer energy consumption when the temperature, the load and the power change according to the transformer energy consumption calculation result calculated by the theoretical line loss calculation module and the statistical line loss calculation module;
analyzing the influence of the temperature change on the transformer energy consumption, specifically calculating the change trend of the transformer energy consumption along with the temperature change, and displaying the analysis result in the form of a table and a curve;
analyzing the influence of the load change on the transformer energy consumption, specifically calculating the change trend of the transformer energy consumption along with the load change, and displaying the analysis result in the form of a table and a curve;
the method comprises the steps of analyzing the influence of power change on transformer energy consumption, specifically calculating the change trend of the transformer energy consumption along with the change of the power factor, and displaying the analysis result in the form of a table and a curve.
Further, the static evaluation and loss reduction decision module is used for generating a transformer model replacement suggestion according to transformer parameters, and obtaining economic evaluation of the transformer replacement technology according to load loss, no-load loss and total loss reduction of the replaced transformer under a set load rate.
Further, the dynamic evaluation and loss reduction decision module is used for analyzing the operation state of the transformer, judging whether the transformer belongs to economic operation or not, and obtaining an economic operation suggestion and energy-saving benefit evaluation; the dynamic calculation of the economic operation of the transformer comprises the steps of calculating the economic load coefficient and the economic operation interval of the transformer, judging whether the economic operation interval is in the economic operation interval, and comparing the loss with the loss under the condition of the most economic load.
Further, when the dynamic evaluation and loss reduction decision module evaluates the economic operation and energy saving benefits of the transformer, the loss reduction electric quantity before and after the transformer is replaced is calculated and expressed as
ΔΔΑ＝(P 0 -P‘ 0 )T
Wherein Δ Δ Α represents the reduced power loss during T-period due to the use of an energy-saving transformer, P 0 Representing no-load power loss, P ', before replacement of the transformer' 0 The no-load power loss after the transformer is replaced is shown, and T represents the running time of the transformer;
the optimal number of transformers for calculating the district construction cost and the low-voltage line electric energy loss cost under the condition of a certain total power transformation capacity, economic load rate and single-seat transformer district construction cost is expressed as
Wherein n represents the optimal number of transformers, S N The total power distribution capacity is represented, beta represents the economic load rate, R represents the parallel resistance of the distribution transformer low-voltage outgoing lines, T represents the running time, f represents the average electricity price, U represents the rated low voltage, C T Representing the construction cost of the distribution transformer of the single-seat platform area;
the transformer loss reduction before and after reactive compensation of the distribution network is calculated and expressed as
Wherein Q represents the reactive power of the transformer, Q C Indicating reactive power for compensation.
Furthermore, the dynamic evaluation and loss reduction decision module selects economic operation intervals of various transformer economic operation modes in a plurality of transformer operation modes according to the sequence of loads from small to large, and obtains a curve with the minimum loss by combining critical values and rated power from the loss curves of the various operation modes through various load-loss curves and a graphical method, so as to obtain the optimal operation mode of the transformer in different critical load intervals.
Further, the dynamic evaluation and loss reduction decision module calculates the power loss reduction of the transformer after the harmonic wave of the power distribution network is treated, and the power loss reduction is represented as
ΔΔP T ＝ΔP Th -ΔP T
Wherein, Δ P Th And the loss of the transformer after harmonic suppression of the power distribution network is shown.
The invention has the following beneficial effects:
(1) Under the condition of ensuring the power supply capacity and the power supply safety, the low-energy consumption and high-efficiency use of the transformer in the power distribution network is improved, meanwhile, the service life of the transformer is ensured, and the cost is saved for the element configuration of the power system;
(2) The good operation of the transformer is ensured, and the power transmission power parameter, the power generation parameter and the economic benefit in the power production process are ensured and improved;
(3) Through a scientific modeling mode, a transformer energy efficiency evaluation analysis calculation method is provided, and a new idea is provided for intelligent energy-saving loss-reducing research of power grid operation;
(4) By means of the transformer energy efficiency evaluation analysis modeling mode, the differences existing in the vast breadth of China and different development stages of power distribution networks in different regions can be effectively solved, actual manual information acquisition, analysis comparison and evaluation calculation in the field are not needed, and manpower and material resources are greatly saved;
(5) The energy efficiency evaluation, analysis and modeling of the transformer can be used for energy conservation and consumption reduction research of the power distribution network, so that the economic benefit of power supply enterprises can be improved, the current national low-carbon economic development target is met, and considerable social benefit is achieved.
Drawings
FIG. 1 is a schematic structural diagram of a transformer energy efficiency evaluation and analysis system according to the present invention;
FIG. 2 is a schematic diagram illustrating a process of power distribution network energy efficiency evaluation based on measured load data according to the present invention;
FIG. 3 is a schematic diagram of the load-loss curves of two transformers of the present invention;
FIG. 4 is a schematic diagram of the load-loss curves of three transformers of the present invention;
FIG. 5 is a schematic diagram of the characteristic curve of the transformer integrated power loss rate of the present invention;
fig. 6 is a graph showing the relationship between the optimal economic operation area and the load factor of the transformer according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Fig. 1 is a schematic structural diagram of a transformer energy efficiency evaluation analysis system according to the present invention; a transformer energy efficiency evaluation and analysis system comprises an intelligent electrical CAD platform and a transformer energy efficiency evaluation and analysis calculation model in data connection with the intelligent electrical CAD platform;
the intelligent electrical CAD platform is used for drawing a full-voltage-grade power grid graph according to set electrical component parameters, and automatically converting the graph component and a mathematical model by using a graph-model integration technology and a structure combining the graph and data;
the transformer energy efficiency evaluation analysis calculation model is used for maximizing the energy efficiency of a medium-low voltage distribution network into a target function under the condition of meeting the power supply capacity and reliability constraints according to a network topological structure, load measurement data and investment cost data, and performing static energy efficiency evaluation, dynamic energy consumption evaluation and technical and economic evaluation of the transformer by taking a medium-voltage distribution line, a distribution transformer and a low-voltage distribution area as boundary adjustment.
In an optional embodiment of the invention, the intelligent electrical CAD graphic platform is a convenient and efficient drawing topology platform, provides a uniform graphic modeling tool for establishing a power grid model, and can completely, accurately, intuitively and simply establish the power grid model; the graph-model integration technology is used, the conversion between the graph element and the mathematical model can be automatically carried out, and the automatic topology function is realized.
The intelligent electrical CAD graphic platform has a perfect basic database, establishes a basic file of a power grid structure, defines a complete power grid element model library, covers all voltage levels and keeps consistent with the existing automatic system graphics. The user can directly select the power grid element from the model library. The system supports the increasing, deleting, modifying and checking, contains information such as a station, a transformer, a line, a capacitance reactor, customer information, metering equipment, specific electric equipment and the like, and describes the affiliated relationship of equipment such as a voltage grade, a feeder line, a switch cabinet, a cable branch box and the like.
The basic data bank has a complete standard data bank, and the contents of the standard data bank include the type and technical parameters of the lead, the type and technical parameters of the transformer, the type and technical parameters of the capacitor, the temperature coefficient of the lead, the shape coefficient of the load, the energy efficiency limit value of the main equipment and the like.
The intelligent electrical CAD graphic platform can conveniently draw the power grid graphics of the full voltage grade, a user can draw layered graphics according to structures in a transformer substation/power plant, a station/plant and the like, default definition is carried out by adopting standard voltage grade color identification, and the color of an outer transformer substation is automatically adjusted to be the color of the highest voltage grade in the station.
The intelligent electrical CAD graphic platform applies a graphic-model integration technology, adopts a structure of combining graphics and data, and automatically converts graphic elements and mathematical models. The system can automatically judge the connection condition of the graphic elements through a built-in analysis mechanism according to the remote signaling state of the power grid, automatically carry out network topology and generate a calculation model (node, branch and load) according to the physical connection relation. The user can directly modify the graphic element or realize the adjustment and the change of the operation mode of the power grid through the entry of the switch state.
The invention can import data in batch from off-line state through the data interface, and supports the data format of most automatic systems; data may also be read from third party automation systems through data integration interfaces, such as: acquiring 24 integral point active, reactive, current, voltage, power factor, phase angle and other instantaneous quantities of a specified typical day and daily maximum and daily average values thereof from a data acquisition system; the method comprises the following steps of (1) power consumption per hour, three-phase unbalance rate, voltage qualification rate, power factor qualification rate, harmonic voltage content rate and distortion rate; after the data is read, data cleaning and data conversion are carried out according to unified standards, specifications and codes, the data are organized and stored in an efficient mode, data access service is provided, and global sharing of information is achieved.
In an optional embodiment of the present invention, the transformer energy efficiency evaluation and analysis computation model specifically includes a theoretical line loss computation module, a statistical line loss computation module, a line loss analysis module, a transformer energy efficiency evaluation and analysis module, a static evaluation and loss reduction decision module, and a dynamic evaluation and loss reduction decision module. The transformer energy efficiency evaluation analysis calculation model is a basic system for energy efficiency evaluation and can be used for carrying out line loss on a full-voltage-level power grid. And calculating the transformer, performing comprehensive evaluation and analysis on the transformer on the basis of calculation, performing energy efficiency evaluation on the power grid element and the operation state to obtain the energy consumption condition of the evaluated object, proposing an energy-saving decision, and performing energy-saving benefit analysis.
The statistical line loss calculation module extracts related electric quantity data from an electric power automation system according to calculation and management standards of the electric power industry, achieves line loss statistical calculation of classification, voltage division, branching and distribution areas, can automatically perform hierarchical calculation statistics and voltage division calculation statistics according to a set hierarchical statistical relationship, can automatically perform calculation statistics of branching lines according to a set branching statistical relationship, can automatically perform calculation statistics of all low-voltage distribution areas according to a set low-voltage distribution area statistical relationship, can automatically perform calculation statistics of bus unbalance rate according to a set bus statistical relationship, and can automatically perform line loss rate statistics of a transformer according to a set main transformer statistical relationship.
The transformer loss is divided into iron loss and copper loss, the iron loss is also called no-load loss, that is, fixed loss, and actually, loss generated by an iron core (also called iron core loss, and copper loss is also called load loss).
The calculation formula of the transformer loss is expressed as
ΔP Z ＝ΔP+KQΔQ
Wherein, Δ P Z Represents the integrated power loss, Δ P represents the active loss, Δ P = P0+ KT β 2PK, Δ Q represents the reactive loss, Δ Q = Q0+ KT β 2qk, p0 represents the no-load loss, PK represents the rated load loss, SN represents the rated capacity of the transformer, I0% represents the transformer no-load current percentage, UK% represents the short-circuit voltage percentage, β represents the average load factor, KT represents the load fluctuation loss factor, QK represents the rated load leakage power, KQ represents the reactive economic equivalent;
the loss ratio of the transformer = PC/P0;
transformer efficiency = PZ/(PZ + Δ P), expressed in percentage; wherein PZ is the secondary side output power of the transformer;
p0 represents no-load loss, mainly iron loss, including hysteresis loss and eddy current loss; hysteresis loss is proportional to frequency; proportional to the power of the hysteresis coefficient of the maximum magnetic flux density. The eddy current loss is proportional to the product of the frequency, the maximum magnetic flux density and the thickness of the silicon steel sheet
PC represents the load loss, mainly the loss in resistance when the load current passes through the winding, commonly referred to as copper loss. The magnitude of the current is changed along with the load current and is in direct proportion to the square of the load current; the load loss is also affected by the transformer temperature, and the leakage flux caused by the load current generates eddy current loss in the winding and stray loss in the metal part outside the winding.
The loss electric quantity of the transformer consists of an iron loss part and a copper loss part, wherein the iron loss is related to the operation time, and the copper loss is related to the load size. Therefore, the amount of lost power should be calculated separately.
The loss electric quantity calculation formula of the transformer is expressed as
The power loss = no-load loss, power supply time and monthly power consumption, copper loss coefficient;
since the copper loss is related to the magnitude of the load current (electricity), when the monthly average load rate of the distribution transformer exceeds 40%, the copper loss coefficient takes 3%.
The theoretical line loss calculation module also provides a line loss small index calculation management function. And small index calculation statistics such as the qualification rate of the unbalanced bus rate and the power utilization completion rate of the transformer substation can be performed.
The yield of the unbalance rate of the bus electricity quantity = (the number of bus bars qualified by the unbalance rate ÷ the number of bus bars) × 100%;
the power consumption index completion rate of the substation = (the number of completed substation power consumption indexes of the substation is divided by 35kV and more) x 100%;
total power loss delta P of transformer T Comprising iron loss P Fe And copper loss P Cu Two parts, the total power loss of the transformer is expressed as
Wherein, Δ P T Representing the total power loss, P, of the transformer Fe Representing the eddy current loss, P, of the excitation branch Cu Representing the resistive losses, P, of the transformer coil 0 Denotes no-load loss, P k Represents the load loss, S N Representing rated capacity, P representing load, and λ representing power factor.
The transformer loss is composed of a variable loss and a fixed loss, the variable loss is approximate to resistance loss and changes along with the change of load, and the fixed loss is generally regarded as constant. Because the distribution transformer generally adopts a delta/Y-11 wiring mode, the load imbalance of each low-voltage winding also causes the zero-sequence current circulation I at the high-voltage side 0 Will become larger.
The theoretical total power loss of the transformer calculated by the theoretical line loss calculating module is expressed as
Wherein, Δ P Tunbalance Representing the theoretical total power loss, P, of the transformer 0 Denotes no-load loss, P k Represents the load loss, I 0 And represents the circulating current of the zero-sequence current on the high-voltage side.
The transformer energy efficiency evaluation analysis module integrally draws a wiring diagram through a diagram module library, records the wiring diagram and then generates a connection relation to perform topology analysis. And after the topological relation is normal, analyzing the static energy efficiency and determining whether a model changing or optimizing strategy exists. And then, judging whether the metering point is perfect and whether the data is finished by combining actual metering data, and then carrying out dynamic analysis to provide energy-saving auxiliary measure suggestions and energy-saving and technical-economic analysis.
Taking a distribution network energy efficiency evaluation system block diagram as an example, transformer energy efficiency analysis is to analyze transformer energy efficiency calculation results from multiple angles such as a result trend of transformer loss, heavy loss lines and the like based on transformer energy efficiency calculation results and statistical results.
As shown in fig. 2, the process of evaluating the energy efficiency of the power distribution network based on the measured load data by the transformer energy efficiency evaluation analysis module is as follows:
drawing a power grid topological structure, and judging whether the topological structure is normal or not; if yes, carrying out the next step; if not, redrawing the power grid topological structure;
static index statistics is carried out according to the static power grid energy efficiency index range library and the static energy efficiency analysis evaluation index system;
judging whether the metering point is perfect; if yes, carrying out the next step; if not, the metering point is installed, and then the next step is carried out;
performing dynamic energy efficiency evaluation based on the actually measured load data, and calculating statistical line loss values under various power supply modes;
judging whether the line loss value is in a set range or not according to the dynamic energy efficiency standard library; if so, generating a power distribution network energy efficiency evaluation report; and if not, carrying out technical and economic evaluation on energy-saving and consumption-reducing measures.
The reason of the energy efficiency change of the transformer can be determined in time through the application of the transformer analysis module, and the rule and the characteristics of the energy efficiency change caused by different power loads, equipment switching and the like of each power grid, each line and each transformer are accurately mastered; and aiming at the condition of higher actual energy consumption, the problems in management and the weak links and unreasonable parts of the power grid structure layout are found in a targeted manner.
The transformer energy efficiency evaluation analysis module is used for analyzing the influence on the transformer energy consumption when the temperature, the load and the power are changed according to the transformer energy consumption calculation result calculated by the theoretical line loss calculation module and the statistical line loss calculation module;
analyzing the influence on the transformer energy consumption after the external temperature changes, wherein the increase of the external temperature can cause the unit resistance of each element to increase, so the transformer energy consumption is a trend of increasing along with the increase of the temperature. The system automatically calculates the variation trend of the energy consumption of the transformer along with the temperature variation according to the setting, and displays the analysis result in the form of a table and a curve;
analyzing the influence on the transformer energy consumption after the load changes, wherein the line transformer energy consumption changes in a curve shape along with the change of the load. The system automatically calculates the variation trend of the transformer energy consumption along with the load variation according to the setting, and displays the analysis result in the form of a table and a curve. The running state of the current transformer can be known to be light load or heavy load through analysis, and a next line transformation scheme can be guided and formulated by taking the running state as a theoretical basis;
and analyzing the influence on the energy consumption of the transformer after the power factor is changed, wherein the line loss rate is reduced along with the improvement of the power factor. The system automatically calculates the variation trend of the transformer energy consumption along with the variation of the power factor according to the setting, and displays the analysis result in the form of a table and a curve. The function can assist the transformer to perform reactive power optimization calculation and provide a theoretical basis for the erection and switching of reactive power equipment in the transformer.
The transformer energy efficiency evaluation analysis module comprehensively analyzes the transformer energy efficiency calculation result, assists transformer energy efficiency analysis work through methods such as contrastive analysis, trend analysis, comprehensive power consumption analysis and transformer energy efficiency loss statistical composition analysis, and analyzes a large amount of data to obtain a useful conclusion.
The transformer energy efficiency contrastive analysis function is carried out on the basis of calculation, and through contrastive analysis, data abnormal points in a power grid are visually displayed, so that the analysis work of the transformer energy efficiency is more convenient.
The fixed loss and the variable loss are two components of the energy efficiency loss value of the transformer. Through the comparative analysis of the two parts, the operation condition of the power grid and whether the transformer and the equipment are in an economic and reasonable operation state can be known, and theoretical support is provided for implementing a corresponding technical loss reduction scheme.
The fixed loss-variable loss is more than or equal to a set value, and the transformer or the equipment is in a light load running state at the moment;
the variable loss-fixed loss is more than or equal to a set value, and the transformer or the equipment is in an overload running state at the moment.
The variation trends of the actual transformer energy efficiencies of the power grid in different periods are obtained by comparing the actual transformer energy efficiency calculation results of the power grid in the same year and different periods (ring ratio analysis) and comparing the actual transformer energy efficiency calculation results of the power grid in the same period in different years (same ratio analysis).
The comprehensive power consumption analysis integrates the energy efficiency basic data of the transformer, and performs basic analysis such as comprehensive load analysis and electric quantity analysis and advanced application such as anti-electricity stealing according to different types and analysis principles so that a user can know the change condition of the system load in time.
The static evaluation and loss reduction decision module is used for generating a transformer model replacement suggestion according to transformer parameters, and obtaining economic evaluation of a transformer replacement technology according to load loss, no-load loss and total loss reduction of a replaced transformer under a set load rate.
In the loss of the power grid, the loss of the transformer accounts for a large part of the total loss, and the system determines whether the transformer is an energy-saving transformer meeting the national standard or not according to the current transformer nameplate parameter, and gives an energy efficiency grade. If the transformer is not an energy-saving transformer, a recommended replacement model is given.
And (3) evaluating the energy-saving benefit of replacing the transformer:
taking load data of a typical day as an example, calculating the power consumption before and after the transformer is replaced and saving the power;
and (4) recording the total investment amount and the discount rate, calculating the date and year energy of model change by using the load data of the typical date, and estimating the recovery age limit.
The dynamic evaluation and loss reduction decision module is used for analyzing the running state of the transformer, judging whether the transformer belongs to economic running or not, and obtaining an economic running suggestion and energy-saving benefit evaluation;
the dynamic calculation of the economic operation of the transformer comprises the steps of calculating the economic load coefficient and the economic operation interval of the transformer, judging whether the economic load coefficient and the economic operation interval are in the economic operation interval, and comparing the loss with the loss under the most economic load condition.
The economic load coefficient of the comprehensive power at the power supply side in the economic operation interval of the double-winding transformer is expressed as
The upper limit load coefficient of the economic operation area is 1, and the lower limit load coefficient is
Namely, it is
The upper limit load factor of the optimal economic operation area is 0.75, and the lower limit load factor is
Namely, it is
The upper limit load factor of the non-economic operation area is
The lower limit load factor is 0, i.e.
The economic load coefficient of the comprehensive power in the economic operation interval of the three-winding transformer is expressed as
The upper limit load coefficient of the economic operation area is 1, and the lower limit load coefficient is
Namely, it is
The upper limit load coefficient of the optimal economic operation area is 1.865 beta JZ With a lower limit load factor of 0.537 beta JZ I.e. 0.537 beta JZ ≤β≤1.865β JZ 。
The upper limit load factor of the non-economic operation area is
The lower limit load factor is 0, i.e.
The dynamic evaluation and loss reduction decision module evaluates the energy efficiency and economic operation of the transformer and comprises the model change evaluation of the distribution transformer.
The power loss of the transformer consists of two parts. One is hysteresis and eddy current loss in the transformer core related to the operating voltage, and because the voltage change in the actual operating process is very small, the loss is traditionally called as invariant loss, also called as iron loss; the second is the loss associated with the transformer load, also known as copper loss, which varies with load and is therefore traditionally referred to as variable loss (excluding losses in the transmission line resistance here). The magnitude of the variable losses depends on the load carried by the transformer, while the magnitude of the constant losses depends on the durability of the transformer core material. Namely that
The loss of the transformer can be effectively reduced by replacing the high-loss transformer into the energy-saving transformer. Under the condition of constant load, the influence of the power grid operating voltage on the iron loss is ignored at the same time, namely the power grid operating voltage is considered to be the same as the operating tap voltage, transformers of different types are used, and the power loss difference is
If the transformers with the same capacity and different models are selected, the copper loss coefficient is the difference between the power loss of the energy-saving transformer with the same capacity and the power loss of the high-loss transformer
ΔΔP T ＝ΔP T2 -ΔP T1 ＝(P k2 -P k1 )β 2 +(P 02 -P 01 )
The energy-saving transformer starts from transformer core materials, and reduces loss and energy saving by reducing core loss. Therefore, the calculation formula of the loss reduction electric quantity before and after the replacement of the transformer is expressed as
ΔΔΑ＝(P 0 -P‘ 0 )T
Wherein Δ Δ Α represents the reduced power loss during T-period due to the use of an energy-saving transformer, P 0 Representing no-load power loss, P ', before replacement of the transformer' 0 The no-load power loss after the transformer is replaced is shown, and T represents the running time of the transformer;
the dynamic evaluation and loss reduction decision module evaluates the energy efficiency economic operation of the transformer and comprises capacity selection evaluation of the distribution transformer.
When selecting a distribution transformer for supplying power to a low-voltage line, the selection of the distribution variable capacity is considered in addition to the address of the load center, and actually, an optimal economic compromise value of transformer area cost increase and low-voltage line loss energy-saving cost exists between 'the distribution variable capacity is large, the low-voltage line is long' and 'the distribution variable capacity is small and the low-voltage line is short'.
At the same total transformation capacity S N Economic load factor beta, and construction cost of single-seat transformer area C T The sum of the station area construction cost for constructing n station area power supply points and the electric energy loss cost of the low-voltage line is
If and only if
The optimal number of transformers for obtaining the construction cost of the transformer area and the electric energy loss cost of the low-voltage line is expressed as
The dynamic evaluation and loss reduction decision module evaluates the energy efficiency economic operation of the transformer and comprises the evaluation of a reactive compensation capacitor.
When a reactive compensation device is arranged at a certain point in the power grid, the reactive power flow of all the series-connected lines and transformers from the point to the power supply point is reduced, so that the electric energy loss in the series-connected elements at the point is reduced. The lower the power factor of the load, the greater the reactive power transmitted from the power supply to the load through the line and the corresponding components in the distribution network, and thus the greater the loss of the distribution network, and the lower the current flowing through the line and the transformer after the distribution network is subjected to reactive compensation, the corresponding reactive loss of the transformer is reduced.
For a transformer, the loss of the transformer before compensation can be expressed as:
under the condition of constant load, if the reactive power is reduced, the loss of the transformer is reduced. If the compensated reactive power is Q C The loss of the transformer after compensation is not counted as the change of the power grid voltage before and after compensation
The loss reduction of the transformer before and after the reactive compensation of the distribution network is obtained and expressed as
Wherein Q represents the reactive power of the transformer, Q C Indicating reactive power for compensation.
The dynamic evaluation and loss reduction decision module evaluates the load balance adjustment and loss reduction technology of the transformer in the power distribution network.
The determination of the economic mode of operation is preferably the mode of operation with the least power loss under the same load conditions. According to the principle, in a plurality of transformer operation modes, the economic operation intervals of the various transformer economic operation modes are selected according to the order of the load from small to large.
And solving a curve positioned at the lowest part, namely a curve with the minimum loss by using each load-loss curve and a graphical method according to the loss curve of each operation mode and combining the critical value and the rated power to obtain the optimal operation mode of the transformer in different critical load intervals. .
Assuming two transformers a and B, the curves in the figure are A, B operating alone and AB operating in parallel, respectively.
As shown in FIG. 3, the load is less than S AtoB The single operation of A is the most economical, and the load is more than S AtoB Less than S BtoAB The operation is most economical when the load is more than S BtoAB It is most economical to run A and B in parallel.
Wherein the critical load S AtoB ，S BtoAB Comprises the following steps:
as shown in fig. 4, three transformers operate economically and corresponding loads. Load less than S AtoB The single operation of A is the most economical, and the load is more than S AtoB Is less than S nB The operation is most economical when the load is more than S nB Less than S ABtoABC The parallel operation of A and B is the most economical, and the load is larger than S ABtoABC ABC is most economical to run in parallel.
The dynamic evaluation and loss reduction decision module evaluates the transformer harmonic suppression and loss reduction technology in the power distribution network.
The transformer loss is changed from no-load loss P 0 And load loss P k The no-load loss is proportional to the harmonic voltage, however, because the voltage distortion rate is small under normal conditions and the proportion of the no-load loss in the total loss of the transformer is small,therefore, it can be considered that no-load loss of the transformer is constant under the harmonic condition. Load loss of transformer is caused by winding resistance loss P R Eddy current loss of winding P EC And metal article stray loss P ST And (4) forming. Under harmonic conditions, eddy current losses and stray losses are proportional to frequency. So transformer loss under harmonic conditions can be expressed as
In which the winding has a resistive loss P R The analysis model of the same line is
Total eddy current loss P EC The eddy current loss under each harmonic is proportional to the square of harmonic current and proportional to the square of harmonic times, i.e. the superposition of the eddy current loss under each harmonic and the fundamental eddy current loss under each harmonic
Total stray loss P ST The stray loss under each harmonic is proportional to the square of harmonic current and proportional to the 0.8 power of harmonic times, i.e. the superposition of the fundamental stray loss and the eddy current loss under each harmonic
In summary, the transformer loss can be expressed as:
after harmonic suppression, the transformer loss is reduced by the amount of power loss reduction
The dynamic evaluation and loss reduction decision module is used for carrying out transverse evaluation and analysis on the technical economy of the distribution transformer in the power distribution network.
And determining the capacity of the distribution transformer according to the load increase condition, and expanding the capacity. And during capacity expansion, carrying out technical and economic analysis on the distribution transformer according to the DL/T985-2005 distribution transformer energy efficiency and technical and economic evaluation guide rule according to the technical parameters, economic parameters and operating parameters of the distribution transformer, and reasonably selecting the capacity of the transformer.
Total power loss Δ P of transformer T Iron loss P in Fe Copper loss P proportional to the square of the operating voltage U Cu Proportional to the square of the operating load S; the operation voltage U is at the rated voltage U N Near, transformer iron loss P Fe Approximately equal to the no-load loss P of the transformer 0 Also known as "invariant losses"; accordingly, the copper loss varies with the change in the load factor of the transformer, and is also referred to as "variable loss". Iron loss P Fe And copper loss P Cu Two parts are as follows: namely, it is
Comparing the total loss of the transformer with the transformer load, the loss rate of the transformer in operation can be obtained
The transformer has the lowest loss ratio if and only if the constant and variable losses in the operation of the transformer are equal. The economic load factor of the transformer at this time is:
transformer integrated power loss delta P Z It can also be represented by the following formula:
because the actual load of the transformer always changes in a certain range, the quality of the operation condition of the transformer cannot be evaluated by a certain value, and an operation area is required for evaluation.
The comprehensive power loss rate of the transformer is as follows:
wherein, P1 is the active power input at the primary side of the transformer. .
According to the above formula, the characteristic curve of the comprehensive power loss rate of the transformer can be obtained, as shown in FIG. 5, the load factor beta is more than or equal to 0 and less than or equal to beta JZ In the range,% Δ Pz is a decreasing function at β JZ In the range of ≦ β ≦ 1, Δ Pz% is an increasing function, but its curvature is much smaller than when decreasing (the variation is more smooth). The long-term full-load operation of the transformer is regarded as safe and reasonable, so the determination principle of the economic operation area of the transformer is as follows: the transformer operates under rated load condition as the upper limit value of economic operation area, so that beta is obtained L1 =1. The lower limit of the economic operation area corresponds to a loss rate equal to the rated loss rate and has a value of beta L2 ＝β JZ 2 ＝P 0Z /P KZ . So the economic operation interval is: beta is a beta L2 —1；
The transformer economy running region includes a large load range including the rated load of the transformer, at the edge of the range (e.g., near beta) L1 ，β L2 Load factor) whose loss rate is still high compared to the lowest loss rate, it is necessary to determine a preferred operation section within the economical operation region.
Through demonstration and analysis, according to the national standard GB/T13462 Industrial and mining enterprises power transformer economic operation guide rule, the upper limit load rate of the optimal economic operation area of the transformer is defined as beta J1z ＝0.75。
Deducing the lower limit value beta of the economic operation area from the above L2 The same method as above, according to the characteristic curve of the integrated power loss rate of the transformer, as shown in FIG. 6, β can be found J1z Corresponding point β when =0.75 J2z ＝1.33β JZ 2 Comprehensively obtaining:
the economic operation interval is as follows: beta is a beta JZ 2 -1；
The optimal interval is as follows: 1.33 beta JZ 2 -0.75；
The worst interval operation area is as follows: 0-beta JZ 2 。
The transformer energy efficiency evaluation analysis and calculation model is established on the basis of an intelligent electrical CAD graphic platform, the transformer energy efficiency evaluation analysis and calculation model is established through a convenient drawing platform and an advanced network topology and graphic-model conversion tool, a whole set of transformer energy efficiency evaluation analysis and calculation model in the whole process is formed, various attribute elements of the transformer can be scientifically and completely reflected in an integrated mode, data basis can be provided for transformer energy efficiency evaluation analysis, and therefore the calculation model is established. The method provides a powerful reference for the energy-saving research of the transformer of the power system, has scientificity and pertinence, and provides a brand-new thought and method for energy-saving transformation of energy efficiency evaluation of the power distribution network through the energy conservation of the transformer.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto and changes may be made without departing from the scope of the invention in its aspects.
Claims (1)
1. A transformer energy efficiency evaluation analysis system is characterized by comprising an intelligent electrical CAD platform and a transformer energy efficiency evaluation analysis calculation model in data connection with the intelligent electrical CAD platform;
the intelligent electrical CAD platform is used for drawing a full-voltage-grade power grid graph according to set electrical component parameters, and automatically converting a graph component and a mathematical model by using a graph-model integration technology and a structure combining the graph and data;
the transformer energy efficiency evaluation analysis calculation model is used for maximizing the energy efficiency of the medium-low voltage distribution network into a target function under the condition of meeting the power supply capacity and reliability constraints according to a network topological structure, load measurement data and investment cost data, and performing static energy efficiency evaluation, dynamic energy consumption evaluation and technical and economic evaluation of the transformer by taking the medium-voltage distribution line, the distribution transformer and the low-voltage distribution area as boundary adjustment;
the transformer energy efficiency evaluation analysis calculation model specifically comprises a theoretical line loss calculation module, a statistical line loss calculation module, a line loss analysis module, a transformer energy efficiency evaluation analysis module, a static evaluation and loss reduction decision module and a dynamic evaluation and loss reduction decision module;
the statistical line loss calculation module is used for extracting electric quantity data from the power automation system and calculating line loss of classification, voltage division, branching and distribution areas, wherein the calculated transformer loss is expressed as
ΔP Z ＝ΔP+KQΔQ
Wherein, Δ P Z Represents the integrated power loss, Δ P represents the active loss, Δ Q represents the reactive loss, and KQ represents the reactive economic equivalent;
calculating the loss electric quantity of the transformer as
The power loss = no-load loss, power supply time and monthly power consumption, copper loss coefficient;
calculating the total power loss of the transformer is expressed as
ΔP T ＝P Fe +P Cu
Wherein, Δ P T Representing the total power loss, P, of the transformer Fe Representing the eddy current loss, P, of the excitation branch Cu Representing the resistive loss of the transformer coil;
the theoretical total power loss of the transformer calculated by the theoretical line loss calculating module is expressed as
Wherein, Δ P Tunbalance Representing the theoretical total power loss, P, of the transformer 0 Denotes no-load loss, P k Represents the load loss, I 0 Indicating the circulating current of zero-sequence current at the high-voltage side, I A ,I B ,I C Representing the three-phase current of the transformer, I n Representing the transformer core current;
the transformer energy efficiency evaluation analysis module is used for analyzing the influence on the transformer energy consumption when the temperature, the load and the power are changed according to the transformer energy consumption calculation result calculated by the theoretical line loss calculation module and the statistical line loss calculation module;
analyzing the influence of the temperature change on the transformer energy consumption, specifically calculating the change trend of the transformer energy consumption along with the temperature change, and displaying the analysis result in the form of a table and a curve;
analyzing the influence of the load change on the transformer energy consumption, specifically calculating the change trend of the transformer energy consumption along with the load change, and displaying the analysis result in the form of a table and a curve;
analyzing the influence of the power change on the transformer energy consumption, specifically calculating the change trend of the transformer energy consumption along with the change of the power factor, and displaying the analysis result in the form of a table and a curve;
the static evaluation and loss reduction decision module is used for generating a transformer model replacement suggestion according to transformer parameters, and obtaining economic evaluation of a transformer replacement technology according to the load loss, no-load loss and total loss reduction of a replaced transformer under a set load rate;
the dynamic evaluation and loss reduction decision module is used for analyzing the running state of the transformer, judging whether the transformer belongs to economic running or not, and obtaining an economic running suggestion and energy-saving benefit evaluation; the dynamic calculation of the economic operation of the transformer comprises the steps of calculating the economic load coefficient and the economic operation interval of the transformer, judging whether the transformer is in the economic operation interval, and comparing the loss with the loss under the condition of the most economic load;
when the dynamic evaluation and loss reduction decision module evaluates the economic operation and energy-saving benefits of the transformer, the loss reduction electric quantity before and after the transformer is replaced is calculated and expressed as
ΔΔΑ＝(P 0 -P‘ 0 )T
Wherein Δ Δ Α represents a reduced power loss during T-period due to the use of an energy saving transformer, P 0 Representing no-load power loss, P ', before replacement of the transformer' 0 The no-load power loss after the transformer is replaced is shown, and T represents the running time of the transformer;
calculating the optimal number of transformers under the conditions of a certain total power transformation capacity, an economic load rate and the construction cost of a single transformer substation area, and representing the optimal number of transformers as the electric energy loss cost of low-voltage lines
Wherein n represents the optimal number of transformers, S N The total power distribution capacity is represented, beta represents the economic load rate, R represents the parallel resistance of the distribution transformer low-voltage outgoing lines, T represents the running time, f represents the average electricity price, U represents the rated low voltage, C T Representing the construction cost of the distribution transformer of the single-seat platform area;
the transformer loss reduction before and after reactive compensation of the distribution network is calculated and expressed as
Wherein Q represents the reactive power of the transformer, Q C Indicating reactive power of compensation;
the dynamic evaluation and loss reduction decision module selects economic operation intervals of various transformer economic operation modes in a plurality of transformer operation modes according to the sequence of loads from small to large, and calculates a curve with the minimum loss through various load-loss curves and by using a graphical method according to the loss curve of each operation mode and a critical value and rated power to obtain the optimal operation mode of the transformer in different critical load intervals;
the dynamic evaluation and loss reduction decision module calculates the power loss reduction of the transformer after the harmonic wave of the power distribution network is treated, and the power loss reduction is expressed as
ΔΔP T ＝ΔP Th -ΔP T
Wherein, Δ P Th And the loss of the transformer after harmonic suppression of the power distribution network is shown.
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