Algorithm for estimating the mode and electricity losses in distribution electric networks 6-110 kV conditions of incomplete information

. The article provides an analysis of methods for calculating electricity losses. The conditions for the application of methods for calculating electricity losses are determined, and structural separated losses in electrical networks are shown. An algorithm for calculating electricity losses is presented, which makes it possible to obtain acceptable results with a minimum of initial information, which has a limited degree of reliability.


Introduction
When performing calculations of the steady state and energy losses in distribution networks of 6-110 kV, we are faced with a lack of circuit and mode information. At the same time, to perform calculations, it is possible to use methods that allow taking into account the features of the information support of networks of this class [1][2][3][4][5][6][7].
This approach is implemented in the DelPROD program, which makes it possible to calculate the mode and energy losses in open distribution networks of 6-10 kV and 35-110 kV, taking into account the incompleteness of information.
The program is designed to assess the mode and energy losses in open distribution networks 6-110 kV with uncertainty in the initial data.
The program provides: -input, creation and correction of the base of initial data on the schemes of distribution networks; -input and correction of initial data on feeder loads; -import of data from text files into databases; -determination of the total characteristics of the substation; -calculation and formation of the feeder equivalent circuit; -evaluation of the state of the feeder mode; -calculation of steady-state modes of distribution networks; -calculation of electricity losses; -drawing up a balance of electricity for feeders; -display of calculation results. Sources of information for calculating the mode and EE losses of an open distribution network are: network diagram, seasonal (monthly) measurements at 35-110 kV supply substations, data on the monthly position of switching devices in the network [8][9][10][11][12].
The algorithm is designed to evaluate the modes of open networks, taking into account the features of information support. The statement of the problem of assessing the state of the mode is formulated as the problem of determining the calculated loads of nodes using the available incomplete information and to the maximum extent corresponding to the most reliable operational information about RGU, OGU -active and reactive power and UGU, -the voltage measured at the head section (GU) of open feeders RS departing from large substations.
Mode estimation is based on algorithms for iterative refinement of node loads and calculation of normal mode. The estimation process ends according to the condition of the minimum of the objective function, which is formed in the form: where РRGU (i) , QRGU (i) -PG powers, calculated in the iterative process and corresponding to the calculated values of loads and voltages at the nodes of the circuit; , a priori weights that characterize the degree of confidence in the measurements, which are determined from the results of measuring the error variance σ 2 ℶ = 1 2 To solve (1), an iterative procedure was developed for sequentially refining the loads of network nodes and calculating modes. The distribution of the loads of the nodes is carried out in proportion to the rated powers of the transformers in the nodes using the coefficients of participation and power, which are specified at each step of the iteration [15][16][17][18][19].
To calculate the voltages and powers at the head section when specifying loads in the nodes, a two-stage method was used.
The algorithm for distributing loads and calculating the mode consists of the following stages: 1) Determination of the initial values of the participation factors and power: where SGU -full power of the head section; ∑total installed capacity of RS transformers; 2) Calculation of the capacities subject to the initial distribution between load nodes: The algorithm also provides for the ability to take into account additional information, namely, information on loads in the form of a power setting Рlj, Qlj, current measurements Izj, cosφ and load factors of transformers Кsh.c, If the additional information of the nodal loads is specified in the form of power, then the unknown values of the loads of the nodes are also determined by the capacities of the head section , In this case, the known values of the powers of the load nodes are summed up ∑ , ∑ ( = 1, 2, … ,k -the number of specified load nodes) and subtracted from the power of the head section. In accordance with this, the following changes are made to the algorithm: 1) Instead of calculation formulas (2.10), (2.11) the expression is used Where ∑total apparent power of the given load nodes; 2) the power to be distributed initially is defined as 3) powers are determined only for those nodes where the values of loads are not specified according to ratios similar to (6), (7).
When specifying the currents of the nodes, at the i-th step of the iteration, the calculated values of the voltages are used to determine the powers of the nodes by the ratios []: where Sjfull power jth node; Ujvoltage Ijload current value Рjactive power Qjreactive power. If information about loads is specified in the form of an average load factor of load transformers Sh.c. then by expression  The current in the j-th nodes is determined. Currents according to (15) are replaced by powers. After replacing the load currents with powers, the calculation is performed according to the algorithm with the given node loads described above; 4) in a two-stage calculation of the power of nodes with given loads, they are considered unchanged. The rest of the estimation algorithm is similar to that described [26][27][28][29].
It should be noted that in the calculations, the power factor cosφ for all load nodes is taken to be equal to the GI factor. If the nodes have additional information on cosφ, then the given values are taken into account in the calculations in expression (12).
Basic formulas for calculations using the two-stage method: Calculation of power flows from end to beginning for ij branches: The block diagram of the mode estimation algorithm taking into account the interval of the initial data is shown in Fig.1.
According to the results of the computational study, it became known that the developed algorithm allows obtaining acceptable results with a minimum of initial information, which has a limited degree of reliability [30][31][32][33][34].
This program can be used to determine the total losses of power and electricity in existing electrical networks, to analyze the modes and losses of electricity.