Gemini project - Integrated solution for operation centers

Gemini project - Integrated solution for operation centers

Marcos V. Abi-Ackel, Cláudio L. Bonfim, Elaine F. Fonseca
Euler H. Teixeira, Leandro R. Medeiros
Cemig - Companhia Energética de Minas Gerais - Brazil
Av. Barbacena, 1200
30.190-131 - Belo Horizonte - MG - Brazil

Introduction
Cemig is the main power company in the state of Minas Gerais - Brazil and its purpose is the generation, transmission and distribution of power within its concession area. Its main focus is electric power with a basically-hydraulic generation matrix.

The company has about 4.9 million customers, distributed in an area of 586,000 km2 - about the same size as France - 286,000 km of distribution network, and 365,000 transformers installed. About 10,000 km of distribution networks are built every year to supply new customers, growing at an average annual rate of 7% .

Our customers are spread in agglomerations ranging from a big one, with 1.6 million customers - the metropolitan region of Belo Horizonte, to a medium one - seven cities over 150,000 customers, and many small centers about and over 3,000 customers, performing a total of 793 cities.

To manage this asset, the company has been investing, since the 1970's, in computer systems. The first successful one was a mainframe-based system to control the low-tension secondary network, from the transformer to the customer. This system has been very necessary because of the secondary network topology used, which sometimes encloses many street blocks and hundreds of customers. The system was dubbed CONSEC, which stands for Secondary Control, and was put into operation in 1982, using since the beginning the UTM (Universal Transverse of Mercator) geographic coordinate system.

The evolution of the geographically-oriented systems was shortly like this:

Consec - (mainframe - IMS-based) secondary network control: from the distribution transformer to the customer. Started its development in 1977, and was initially put into operation in 1981.

Conprim - (mainframe - IMS-based) primary network control: for the primary, 25 kV class feeders. Started its development in 1981, and was initially put into operation in 1984.

Consec - (micro computer version - DOS) graphical user interface, showing the secondary data in geographical form: Started its development in 1988, and was initially put into operation in 1990. This system improved greatly the secondary data quality because of the graphical user interface and the very easy way to check and modify the electrical network data.

Conprim - (micro computer version - DOS) interface based on primary schematic diagrams. Although the interface was not geographic, the internal data was all UTM-based.

All these systems were completely developed inside the company by a specialized team consisting of electrical engineers with a large experience in computer science.

From 1994 to February, 2000 the entire company used the microcomputer version of the CONSEC and CONPRIM systems to manage its electrical network. The Gemini Project is now replacing these systems.

The Gemini Project was started in 1995 with the main purpose of evolving the existing network management systems into a modern, completely integrated and GIS-based system. In December, 1998, the system was put into operation in the main Operation Center of the company, in Belo Horizonte, eliminating the 2.5x13.5m operation wall diagram and assisting all the operation tasks to the 1.5 million customers of the covered region.

Now (March, 2000) the Gemini project is in operation in all Operation Centers in the company, directly assisting the operation tasks to the whole covered area, about 4.9 million customers. The old CONSEC and CONPRIM systems are now being systematically replaced by the new system.

Gemini project
Gemini is an integrated project for mapping and management of the electricity distribution system. The main goals are the production and update of mappings (Cartor Module) and the storage, update and use of the electrical network data to support the planning, design, maintenance and operation activities (Prolux Module). The main emphasis is on the operation of the distribution system.

The system emphasizes geographical functions and modeling of the distribution networks, in the form of the AM - Automated Mapping and FM - Facilities Management, running under Windows NT, on a client-server architecture. It is a low-cost platform that allows a perfect matching between resources and the size of the database, being easily scalable: the same software is installed at small computers serving small cities and NT clusters for reliable operation at larger centers.

The system has been completely developed by using object-oriented methodologies, and supports the main databases in the market, making it easily adaptable to cities of several magnitudes. We're now using Oracle database for the major cities and Interbase for all others, due to price and support issues.

The Gemini Project has two main modules named CARTOR and PROLUX.

The Cartor Module corresponds to obtaining and updating the cartographic bases in digital media, and is a customization of the existing CAD software.

The Prolux Module, which corresponds to the management of the distribution network, has been entirely developed by the company's team to better meet the electrical distribution needs.

Cartor Module
This module helps obtain and maintain the maps used in the electrical distribution activities. Cartor is the tool used to transfer the main existing cartographic documents to digital media, so that the Prolux Module could use them as a base for plotting the electrical network. It also allows mapping updates through many data acquisition techniques, such as topography, aerophotogrametry, satellites geodesics and GPS (Global Positioning System).

It has been developed by using the Microstation CAD and its intrinsic Basic language. The customization placed a standard for the digital maps at the distribution departments of the company, establishing 49 specific levels of information grouped in 9 classes: field support, road system, hydrographic system, buildings, text, vegetation, altimetry, streets and geo-reference.

The Cartor Module has support for "heads-up" vectoring, and coordinates transformations to convert the previous paper maps into the UTM coordinate system.

All urban maps of the company are now in digital format. The system has shown an 80% reduction in time and costs regarding office work. This figure corresponds to about 50% reduction of final costs for the whole mapping process.

Prolux Module
The Prolux Module is aimed at the management of the electrical network, integrating in the data model all the necessary entities to describe the entire distribution network, so as to support the operation, design, planning, construction and maintenance activities of the electric distribution system.

The cartographic information generated and updated by the Cartor module is integrated seamlessly with Prolux's distribution network data. It's also possible to display two different levels of raster images below the mapping layer, allowing the use of orthophotos and systematic mappings.

All the information is stored in a UTM reference system that is graphically represented inside a continuous space of coordinates in the UTM fuse, allowing continuous zoom scales.

Fig. 1 - Prolux: Key Map and 3 Normal views in different scales.
The leftmost shows a query popup menu.

There are many levels of information that can be turned on, off or adjusted to a range of scales, such as:

Clients (customers);
Primary and secondary cable spans;
Transformers;
Primary and secondary structures;
Poles
Public lights
Equipment and switches
Images
Streets
Orthophoto
Systematic mapping
Vehicles
Tags
Etc

There are also many support functions accessible through consults or specific commands issued by the system's user:

Electric loss, load and tension drop for secondary and primary circuits;
Short circuit levels along the primary feeders;
Queries to all physical data for each element or entity;
Load maps - plotted using load density or main consumption type.
Graphical functions for transformer load management, secondary tension drop and primary feeder cable load;
Support for primary switching: opening and closing of primary switches with calculations for the new electrical network condition;
Switching analysis, showing the many constraint conditions;
Hierarchy diagrams for feeder's switches
Etc.

Operation Support
The Prolux Module has specialized views to support the Operation Center activities, helping minimize the involved complexity inherent to the operation tasks.

Besides the Normal View, that has all the information of each entity, there are three other views specifically designed for operation support, where the primary feeders are drawn in a simplified way, although preserving the raw geographic form and omitting all information not necessary for the operation analysis. The first of these views is the General Operation View, which draws the operational view of the feeders inside the geographic area to be represented. See fig. 2 and 3.

The Operation Analysis View (fig. 4) is the most frequently used view in the Operation Center. It represents only the feeders chosen by the user in the same simplified way as shown at the General Operation View, but has many other options, such as:

Turn on or off each feeder;
Perform switching analysis;
Turn on or off each of the feeders that has a direct connection with a represented feeder;

The switching analysis is a powerful tool that can be used to verify the constraints imposed by the maneuver, showing the primary cable spans that will be overloaded, the equipment - like reclosers - that will have its electrical flux reversed, special customers affected, etc. See fig. 4. At the initial window it is possible to specify at what time switching will start and end. This information builds the load curve for each feeder before and after the operation. See fig. 4.

The small white diamond a little above and to the left of the center of figure 4 indicates the nearest 50% load switch.

At figure 4, the following should also be noticed:

The switches involved in the operation analysis, highlighted with a target sign;
The analysis result window, showing current limits and constraints;
Two overlapped windows showing the load curve of each feeder before and after switching;

The operation views also display:

Special customer flags, in four different classes;
Tags of many types, such as "Defective Equipment", "Do not operate this equipment", "Earth protection out of service", and many others;
Direction of electrical flow on closed switches and equipment;
Equipment with remote command for automation;
Equipment numbers, shown as hints when the cursor runs over them;
Feeder interconnections to other feeders;

Fig. 2-General Operation View side by side with a Normal View of the same area,
showing the feeder simplification. At lower right of each view there is an open switch
showing a de-energized feeder (left view: dotted with white, right view: gray dotted).
At the center, part of the green feeder has been moved to the red feeder (left view:
red dashed, right view: green). Note the advertent plates (as flags) placed
automatically to show that the devices are not at normally-operated position.

There is also an Operation Diagram View showing the hierarchy of equipment and switches along the feeder, together with the percentage load at each point. See fig. 3 and 6.

All data is dynamically updated, so that after every equipment or switch operation, a procedure is started to calculate all the parameters for the new feeder configuration. All these procedures must be accomplished within a few seconds because of the nature of the job at the Operation Center, imposing a hard requirement on the system.

Fig. 3 -General Operation View and Operation Diagram View.

Fig. 4 - Operation Analysis View, analysis result window and load curves.

Fig. 5 - Secondary Analysis View and Load Map View. The Secondary analysis
shows transformers colored according to their load and the secondary
circuit colored according to tension drop.

Corporate integration
The electric demands calculated by the system for the feeders, transformers and secondary circuits are based on the individual consumption of each customer stored in the database. This very precise data is read each month from the customer meter and stored in the mainframe customer database. All necessary customer data changes are exported to update the Gemini database on a weekly basis.

There is an internal statistical model that converts the customer's consumptions to electrical demand, computing the sum at the transformer. The primary calculations are based on the demand value at the transformer, but adjusted to the observed hourly load curve of the feeder, which is obtained by the SCADA system or by direct measurement at the substation or along the feeder.

The SCADA system sends all alarms and significant events to the Prolux Module, which is the unique usual graphical interface to the personnel at the Operation Centers.

The interface between the Trouble Call/Outage Management system and the Gemini Project is very tightly coupled, since they share the same logical database. The Trouble Call receives the calls from the customers and groups the problems together using the network topology stored at the Gemini database, indicating the exact defect point or the probable operated device. Then the operator can initiate a service to solve the problem, dispatching a vehicle to the determined position. All these activities are completely supported by the Prolux Module, which is integrated to the Trouble Call/Outage Management processes.

If the operator determines that it's necessary to operate some equipment or switch, he issues the command directly to the Trouble Call/Outage system. All consequent actions are automatically taken at the Gemini database, reflecting the opening or closing of the device, including all primary feeder calculations.

Presently, all SCADA-controlled equipment operation is reported to the Prolux, but the command to operate the equipment is issued directly to the SCADA interface. This was chosen for security purposes, but it will be replaced by an automatic operation in the near future.

The Prolux Module is also connected with the Automatic Vehicle Location system (AVL), showing their positions in real time.

Fig. 6 - An ortophoto under the Normal View, showing a consult to a feeder
data, and its load curve. On the left, the feeder Operation
Diagram View and the Operation Analysis View.

Conclusion
Since its first release, the Gemini Project has achieved great reliability and trust, eliminating all conventional paper and wall maps used to support the Operation Centers' main tasks.

The quality of the Operation Centers' work was greatly improved, reducing theaverage outage service time, because of the easy analysis of outage problems, and better specification of long maneuvers involving many switches and equipment. Users can get all needed information at the computer.

One important fact is the improved environment at the Operation Centers, which are now quieter and less stressing, leading to better-analyzed solutions during emergency outages.

The Gemini Project release has introduced great changes to the way operations are processed are conducted at the company, making the whole scenario more reliable and clearer. It has definitely changed the profile of Cemig Operation Centers and their associated activities. mvaa/99