GIPSY is an Information Technology tool developed by Tractebel for analysis, planning and graphical design of electric networks. It is based on a high-level graphical interface associated with an object-oriented database. Different modules for specialised calculation of network analysis can be added to this standard platform.
This environment has been designed to relieve users as much as possible from accessory, repetitive and uninteresting tasks, enabling them to focus on the more critical aspects of network planning.
The graphical interface is used to create or enter different network elements easily: branches, bus-bars, transformers, sub-stations, generation units, loads, etc. The command for creating an element generates both the internal representation of the object in the database and its graphical representation on the screen. By clicking with the mouse on the representation of the object, one can access its record in the database and consult all its associated information.
The central position and role of the database in the GIPSY environment is the guarantee of the coherence of the data. What is stored in the database corresponds exactly to what is displayed on the screen and of the data what will be printed (WYSIWYG “What you see is what you get”).
The database contains a detailed representation of each physical element in the network. This mode of representation allows for optimum adaptation to most planning applications, since the data can be processed at different aggregation levels in line with the requirements of each application.
GIPSY contains three different modules dedicated to calculations of power flows with three different methods adapted to HV, MV and LV systems. The graphical interface provides a clear view of the results, for example, highlighting overloaded branches or nodes where the voltage is abnormal.
The data required by these two models are prepared by the graphical interface which transforms and aggregates the system physical representation into the data needed by these models.
An essential particularity of GIPSY is its capacity to generate both a semi-geographic view of the network and a block diagram highlighting the functional aspects. This results in the possibility of choosing, for each network element, either a synthetic representation, usually in the form of an ordinary square, or a detailed representation.
By applying this principle more generally, the “sub-network” concept allows another scale or a different representation mode to be used for certain parts of the network. For example, a functional, block diagram representation of the internal topology of a complex sub-station can be combined with a semi-geographic view of this sub-station in the context of the entire system.
By making an optimum use of the multiple windows technique, users can work simultaneously on an overall view of the system and in windows presenting certain sub-networks in a more detailed manner, on a different scale and with an appropriate plan background.
GIPSY allows, for each network part, three different representations or views. The first view, called fish-eye view, gives a general overview of the networks under study. The second view, called mid-scale view, gives a geographical view of the networks with a level of details corresponding typically to 1/25000 maps. The third view, called large-scale, gives a detailed geographical view of the system, with a level of details corresponding to 1/2000 maps. The two last views, with different backgrounds and line or cable paths, do not correspond to a simple zooming operation.
The program offers to the users a wide range of features, including lists of standard objects which can be inserted in the scheme, automatic alignment and orthogonal mode drawing, erase functions, as well as functions relative to associating labels with the objects.
One of the more novel characteristics of this program is its capacity to take into consideration different variants (scenarios) of the system being studied and their evolution in time over a determined time period. This means that not only development options can be compared using a “what if” type mode, but also that the future coherence of the studied options can be managed. Variants are also called "worlds".
The concept of “world” is of paramount importance for scenario management. Starting from a root-world that represents the existing system and the information common to all the possible scenarios (e.g. demand data and existing networks), the user can create scenarios of development to be able to satisfy the technical and supply quality requirements of the system during the study period. So, “child”-worlds will be built, derived from the root-world or existing child-worlds. If the system is modified in a specific world, this modification will take place in all its “child” worlds, but not in its “parents” worlds.
The system loads are represented using load curves, either chronological or with a load duration curve and load states. The loads can be introduced or modified directly in the graphical interface or through the interface to spreadsheet file. In this case, each load must be provided with its exact geographical location. GPS (Global Positioning System) data can be used for that purpose. Only such a detailed representation of the load behaviour allows an accurate calculation of energy losses.
Detailed time consideration is a major asset of the GIPSY tool. It is an essential feature for analysis and planning requirements.
In the first place time representation is used for the load curves in each demand node. Further, the representation of the time allows the correct identification of each development strategy of a system. Indeed, a development strategy extends over several years and it is the sequence of investments that actually defines the strategy.
The representation of several periods as the base time concept allows the check of the coherency of the investment sequence. Indeed, for a specific year of the planning period, the network elements are activated only if they are already commissioned. Therefore, it is impossible to connect an element to any other that would not be identified as already commissioned (see further, Coherency checks).
Finally, it is possible to display the networks at a given time, or to display all the periods together, using different colours for investments made at different periods (multi-periode mode : see figure below).
They are 4 types of coherency checks inside the GIPSY software. Topological coherency checks insure that a line is always connected to a node. Inside large-scale (ex: 1/2500) maps, spatial coherency avoids the placing of two network facilities exactly at the same place, or in single line diagrams, to have two equipment with superimposed drawings. With the temporal check, the database is protected against incoherency such as the connection of feeders to a substation that do not (yet or anymore) exist at this time period.
Finally, specific checks are linked to the hierarchical structure of the worlds. The coherency check consists of verifying if an action taken in a world may lead to incoherency in sub-worlds.
GIPSY includes three integrated network analysis tools :
§ The load-flow for MV networks (The FLAGS module)
A specific module targeted to MV networks calculation is completely integrated in the software. Several operating schemes can be memorised and analysed.
§ The load-flow for HV networks (The Echo module)
Calculation of the active energy and reactive energy circulation in a given network. The solution to this problem consists in solving a set of non-linear equations; the method used is the Newton-Raphson iterative method. Short circuit calculations are also made, and the short circuit level at each node is published.
§ The load-flow calculation for LV networks (The Atrebate module)
A completely different calculation algorithm is implemented for the determination of the currents in the LV networks.
The following relation linking the peak power (P) and the energy (E) is the starting point of the calculation algorithm:
The use of a special relation is justified by the fact that the load factor, nearly constant along MV networks (typical value of 0.4), varies considerably along the path of a LV feeder (0.09 to 0.3).
Worlds can be used for storing particular network calculation case. The concept of operation scheme (i.e. mainly MV switch positions) allows the storage and the comparison of different network configurations.
An interface to and from .dxf file is also provided, for map and plan background management purposes.
An interface to and from .xls (Excel) files is also provided to import/export alphanumeric data in the database.
The GIPSY program has been developed using Allegro CL, a dynamic object-oriented programming system from Franz Inc. Allegro CL is based on an ANSI-standard language (Common Lisp and CLOS) which meets all of the Gartner Group's "must-have" and "should-have" criteria for object-oriented languages. The underlying object oriented database system is ObjectStore from Object Design Inc. It runs in the Windows NT environment and is capable to store a large data set including hundred of thousands of network elements.
GIPSY has recently been used in several occasions:
§ In Kenya, under its old name of GRIP, to establish a large scale rural electrification Master Plan. The medium voltage (MV) of the areas studied cover a surface corresponding to some 300 A0 topographical maps (scale 1/50000); they include more than 7,000 MV/LV sub-stations.
§ In the Ivory Coast, as part of the Rural Electrification Master Plan. The impact of the development of rural system on the HV networks was also analysed.
§ In Mauritius, in the context of a distribution networks (urban and rural) Master Plan. The modules supplied in this case were the HV, MV and LV calculation tools.
The following figures illustrate different aspects or key feature of the Gipsy software :
1. A view of the main display with the mid-scale (1/25000), the large-scale (1/2500) and the corresponding fish-eye views.
2. A view of the mid-scale window, with network and background information.
3. A view of an operating scheme (one colour per feeder) in the mid-scale map fish-eye.
4. A view of abnormal voltage drops in red, in the mid-scale map fish-eye.
5. A view of load-flow results (operation scheme and overloads) in the mid-scale window.
6. An example of sub-network.
7. An example of the multi-period mode : existing networks are represented in black, network at different time periods are represented with coloured dotted lines.
 Fast Load-Flow Analysis for Great Systems