UDC: 681.3.01: 004.5
SOFTWARE COMPLEX FOR ELECTRICAL NETWORK ADAPTIVE MANAGEMENT
V.V. DOROFEYEV, YU.I. MORZHIN, M.A.RABINOVICH1
Introduction. Development and structural transformations in the electric power industry of Russia have lead to essential changes in operating conditions of the Unified Power Grid (UPG) of Russia and in the concepts of its management. This report presents formulation of the problem and the basic principles of constructing an adaptive (intellectual) complex for electrical network management (CENM). CENM includes hardware and software control means. Below only the software CENM means are considered. The basic objectives of the complex and its structure are presented. Results of development of pilot projects and their operating experience are given.
The report considers the questions of adaptation of the network in response to operating condition situation and equipment state. The prime objective of electrical network adaptive management is increasing the reliability and efficiency of equipment operation by way of permanent monitoring the operating conditions and topology of the network using the operative-informational complex (OIC) means, state estimation, solving a series of informational and technological problems [1-5].
The prime objective leads to decrease in amount of violations of the limiting values by the operating condition parameters, reduction in network losses and in energy not supplied to consumers.
A special feature of the complex is its capability to be modified and supplemented by users and maintenance personnel. The complex was created and modified [5] using construction means (for diagrams, tables, graphs, scenarios etc.), which enabled the time and expenditures to be reduced by a factor of 3-4.
Basic tasks. Operating personnel of a network company carries out the network topology monitoring and a series of switching operations at the objects of its responsibility level. The tasks of controlling limiting values violation by the operating condition parameters, of minimizing network losses, of operative studying requests from the point of view of operating conditions, of analyzing nonstandard situations, of removal the main equipment from service for repairs and its introduction into service and a number of other tasks are being solved. Trainers-advisers on operating switching and dispatcher instructions are also used.
One of the main tasks of the complex is estimating the security of the current and forecasted operating conditions for a network utility. As a criterion of the estimate an integral parameter may serve which takes into account a degree of distance of the power object operating conditions from the borders of a feasible area in the state space. Operating personnel of some power objects reckons till now that the convergence of the state estimation (SE) task ensures a high security of operating conditions. We note that a successful solution of the classic SE task does not, unfortunately, guarantee, the operating condition security.
Sufficiently high security estimation is given by the task of controlling (in a broad sense) by N-1 criterion. Under N-1 criterion in broad sense we will understand a check of operating condition existence for a set of network topology disturbances,
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1 (NTC elektroenergetiki, Moscow, Russia, e-mail )
short-circuits, actions of emergency automatic facilities etc. This task is solved by the CENM complex in real time (RT). The operating condition security control by N-1 criterion in a broad sense can include also the control by criteria N-2, N-3 and so forth. The problem is only one of availability of sufficient computational resources for solving this task in RT.
Computational-controlling CENM, consisting of a central complex (in the network controlling center (NCC)) and a number of remote complexes in regional control centers (named MES in Russia), will enable the operating personnel to fulfill a complete set of their position functions which is now under enlargement and establishment.
The CENM must first enable the personnel to access the necessary information, which is concentrated at present mainly in OIC and a number of auxiliary Data Bases (DB). An unconnected character of the information makes integration of various CENM tasks difficult and complicates the development and technical maintenance of the complex. The use of CIM standard for representation of current, historical and normative-reference information enables the problem of incompatibility of the tasks in the CENM to be solved by way of considerable effort.
All complexes of individual MES communicate with the NCC and between each other. This communication can be realized using an economic radial circuit and will enable the NCC to receive all necessary information on MES. The system with informational ring links is less economic but more reliable.
Figure.1
In order to carry out switching it is required to form current operating conditions, to perform topological analysis of a complete diagram of connections of the controlled power object taking into account admissibility of needed switching, to fulfill calculations and obtain conclusions on the equipment state. As distinguished from the traditional analysis scheme (about a day ahead the forthcoming switching as a rule) the proposed scheme carries out analysis on the basis of the current operating conditions, which undoubtedly reduces the probability of erroneous conclusions.
The conclusion on switching admissibility is made with the help of the adviser the basic task of which is to check the expected operating conditions for security (by limit parameter values, by N-1 criterion etc.) and admissibility of switching operations from the point of view of dispatcher’s instructions. Among the checks carried out sufficiently complicated ones are possible which take into account occurrence and development of emergencies, post-emergency restoration of the network integrity etc. The violation of even a single one of the criteria checked leads to refusal from expected switching.
The complex is supplemented with a system forming possible versions for introducing the controlled system into admissible area. This role is fulfilled by the dispatcher’s adviser on dispatcher’s instructions. For each possible violation the dispatcher’s instructions relating to this violation are classified for the possibility of their realization and are checked on the model. The dispatcher obtains only feasible and effective instructions.
Figure .2.
Structure of the program complex. The nature of tasks solved by the CENM enables it to be divided into two basic systems:
· A real-time system (ON LINE),
· A system of tasks out of real time (OFF LINE).
The structure of the RT task complex is shown in Fig. 1. This complex includes SCADA and a number of informational-technological tasks (see Fig. 1). Many tasks of this complex are relatively new (power system RT model, SE, topological processor, study of requests and others). Many of these tasks were solved before only OFF LINE. It should be noted that some tasks of this system (for example switching control, geo-informational system (GIS), calculation of short-circuit currents, fault location, consumption planning, team management and others) are under development.
Informational interaction of the RT tasks is presented in Fig. 2. The pointed RT tasks are implemented in a number of power objects (in the control center of the power pool of the Center, in the control center of regional power system Bashkirenergo and others).
All systems must work with the DB of equipment, which will be CIM-compatible. At present DB of individual tasks of the complex are used.
The human-machine interface presents information on individual (displays) and team (video-wall) means.
Figure. 3
Structural diagram and diagram of connections of the network enterprise, and also detailed diagrams of substations are displayed. The video-wall (see Fig. 3) is managed from an individual workstation [1].
In the CENM frames the following main tasks are being solved:
1. Limit control.
This task controls limiting values of operating condition parameters (power transmission currents, power flows through cross-sections, voltages in control points of the circuit etc.) taking into account the operating condition heaviness, network topology etc. The limiting values are defined in RT taking into account weather conditions and current repairs circuit. All parameters processed are visualized at workstations of operating dispatching personnel or on the video-wall in a form of mimic diagrams, digital indicators, histograms and plots. Results of controlling the limiting values and the equipment state are presented in the structural diagram of the controlled network on the video-wall.
2. Controlling energy quality
In RT mode the power system structure (topology and equipment commitment) are chosen which ensure the best electrical energy quality and the reliability of power supply for consumers. First of all, violations of the limiting values by the operating condition parameters are controlled. For admissible parameter values the quality of the voltage and frequency of the electric current at consumer side is evaluated from the point of view of fluctuation variance, power outages and others. The task is solved by exhaustive search (by way of modeling) of possible versions of topology and equipment commitment for the current operating condition state. The current operating conditions are formed by the SE task using OIC data.
3. Optimization by Q and U – reduction in losses
Optimization of operating conditions by reactive power and voltage is solved for a purpose of minimizing losses by way of changing the network configuration, managing reactors, synchronous compensators, and transformation ratios. It is worthwhile to use in this task the new technologies (managing power transmission line carrying capacity). The task is solved in real-time using initial information obtained in the SE task. At the first stage it is supposed that this task operates in a mode of a dispatcher’s adviser. The result of the task solution is outputted to the dispatcher in a form of recommendations.
4. Switching management.
The task realizes following functions:
· Automated composition of switching plans,
· Switching plans control,
· Control of commands for switching,
· Trainer-adviser for operating switching.
At the first stage the work of the task in a mode of a dispatcher’s adviser is supposed, and in the future the automatic work when carrying out switching-over in the network.
5. Control by N-1 criterion
The operating condition reliability is controlled by N-1 criterion in real-time on the power system model using initial information received from the SE task. A given set of possible emergency situations (power line and power unit switching-off, short-circuits at the busses of substations and power lines etc.) is checked. Emergency situations are given using scenarios for the current and forecasted operating conditions and expected repairs circuits. Feasible actions of operating personnel for removal of the operating condition disturbances are given in a table form.
6. Real-Time model.
The RT model in the CENM complex takes part in solving a number of tasks: dispatcher’s advisers, trainers, control by N-1 criterion etc. The model enables steady-state and transient operating conditions to be calculated.
The model enables one to study Requests for removal equipment from service for repairs from the point of view of operating conditions, to carry out monitoring of the current balanced operating conditions and, of course, it is the basic component of the trainers-advisers.
7. Topology analysis
This task determines in RT:
· switching state of the network equipment (power transmission lines, transformers etc.),
· switching state of the power object circuits (circuit splitting).
A log of events is kept. The switching states are displayed in the operating and structural diagrams of the network. The task is used in the trainer for operating switching (TOS) and when controlling switching.
8. Non-standard situation analysis
This task determines in RT:
· network portion separation,
· probable faults in equipment (short-circuits in power lines, busses, transformers),
· possible failures in action of switching apparatus (breakers).
Non-standard situations are displayed in the circuit diagram and in a form of special symbols and text descriptions.
9. Short-circuit current calculation and recommendations on the network division
The short-circuit current calculations together with the dynamic stability calculations are carried out for the heaviest disturbances which are taken into account in the requirements for the power system stability called normative disturbances divided into three groups. Results of these calculations are used for determining the network “normal” operating conditions.
If as a result of short-circuit calculations the current values obtained are greater than the breaker interrupting capability, the program recommends to divide the network in new points or to carry existing division points to other places.
10. Fault location
Evaluates correctness of defining by dispatcher personnel of the points of network failure from the fixing device indication and protection action.
11. Managing repair teams
Defines the optimum composition of repair teams and their route to the place of restoration works, and also repair duration. Supports the DB of repairs and equipment state.
12. Dispatcher’s adviser on instructions
The dispatcher’s adviser uses a vast stock of knowledge concentrated in dispatcher’s instructions. In this task the correspondence is established between possible operating condition disturbances and the dispatcher’s instructions applied in these cases. The task automatically chooses a set of recommendations for the operating condition disturbance pointed by the dispatcher, checks their feasibility and if necessary their effectiveness by way of modeling.
13. Switching management in emergency operating conditions
The task carries out automatic reconfiguration of the network (ARCN) including:
· reconfiguration for restoration of the network portions having been separated,
· reconfiguration for removal of equipment overload,
· reconfiguration for reducing possible short-circuit currents,
· other objectives of reconfiguration.
At the first stage the ARCN operation is supposed in a mode of a dispatcher’s adviser, and in the future - the ARCN automatic operation (smart grid).
Conclusions.
The report presents structure and composition of tasks of the program complex for electrical network management. At present complex readiness is 70%. Under development there are real-time tasks: calculation of short-circuit currents, fault location, recommendations concerning network division and optimization of operating conditions by voltage and reactive power. A great amount of work is to be done when installing the complex at an object.
Literature
1. New technology of displaying operating dispatcher information at control centers in power industry. …. , Enerhoekspert, No. 2, 2007.