Keywords: SVG, XML, User Interface, Electric Network, Training
Paul J. Nolan holds a PhD degree in Electrical Engineering from McMaster University, Ontario and is Professor of Mechanical Engineering at the National University of Ireland, Galway. His main interests are Expert Systems, Simulation and Web-based training. He is a director of ASTech.
Michael Murphy has a worked as a Senior Trainer at the ESB's Distribution System Training Centre in Portlaoise, Ireland. He has recently joined ESB's Network Business as a Senior Analyst.
Arthur Byrne is a graduate in electronic engineering from University College Dublin and has held a number of senior positions at the Electricity Supply Board (ESB) In Ireland. He is currently Manager of Training for both IT and Electrical Distribution within the ESB.
Domhnall Walsh has been involved at a high level in the development of a number of web-based training and technical documentation projects with Atlantic Simulation & Training Technologies since 1997, with a heavy focus on XML and related technologies. He holds a B.Eng in Electronic Engineering from National University of Ireland, Galway and is currently pursuing an M.Eng.Sc. from the same institution.
Much of the time and expense invested in training electrical network technicians in the area of power generation and distribution is given to teaching and testing the technician on his/her knowledge of standard switching procedures. Due to the potentially drastic consequences of any error while carrying out electrical switching operations in a high voltage environment, trainers must ensure that technicians have an adequate understanding of the procedures involved; this requires a considerable amount of "on-the-job" training. It also involves very considerable time being spent performing paper-based exercises where switching plans are developed to meet specified criteria.
This paper describes the replacement of the paper-based exercises for developing switching plans with an electronic version using SVG. The system, NOSTRA (Network Operation Switching TRaining Aid) was developed for ESB (Irish Electricity Supply Board)'s network training school. The web-based package is designed both as an instructional aid and as an assessment tool.
At the heart of NOSTRA is the network diagram, rendered in SVG, displaying a synthetic system with a mixture of both 3-phase and single-phase distribution network (including underground cable), transformers, switching kiosks and so on. As each step in the switching plan is entered during an exercise, the user may navigate through the diagram (including zooming and panning) and look up hyperlinked material (e.g. procedural manuals, safety rules, equipment photographs and so on). The SVG diagram is annotated with additional graphic symbols (e.g. earth symbol added), and this information is updated in response to changes in the status of the network during an exercise.
2. NOSTRA (Network Operation Switching TRaining Aid)
3. TECHNOLOGIES USED
3.3 Rule Based Expert System
4. IMPLEMENTATION DETAILS
4.1 User Interface
4.2 Back-End & Expert System
4.3 SVG Network Representation
4.4 Task Representation
5. OPERATION OF NOSTRA
5.1 Usage Scenarios
5.2 Browsing The Network
5.3 Typical Exercise
6.2 Future Work
One-line diagrams are used extensively in the electric utility industry to show installed equipment (generators, transformers, busbars, circuit breakers etc.) and interconnecting transmission and distribution networks. Such diagrams are used in both planning and operation applications. The electronic display of such diagrams has largely replaced hard copy. Traditionally, such diagrams have shown static data (e.g. network parameters) or are annotated to show calculated data such as results of a load flow, short circuit calculations and so on. AutoCAD (DXF or DWG) or native GIS formats have been used. The advantage of using XML for common data exchange has been recognised through the XML-based Power System Information Exchange programme agreed by EPRI (Electric Power Research Institute) for CCAPI (Control Center Application Program Interface).
Increasingly, applications are being delivered via web interfaces. Users demand that their web applications display and interact with rich graphics. Moving from the static bitmaps of today's web towards a more scalable, dynamic and interactive web content is demanded. The answer is Scalable Vector Graphics (SVG), which allows us to describe two-dimensional graphics, such as utility one-line diagrams, in terms of an XML grammar. These can be manipulated with CSS or XSL style sheets or processed directly as XML, and feature advanced styling functionalities such as colour gradients and filter effects. SVG is the W3C-recommended, XML-based, standards-compliant alternative to similar proprietary formats. Developers can create Web displays that integrate data-aware graphics on top of maps. Raster as well as vector data sets can be included and in addition to the usual panning, zooming, and object selection, animations and sophisticated interactivity can also be incorporated. Thus the static one-line diagram for a power system becomes a scalable and dynamic interactive web document.
This paper describes the replacement of the paper-based exercises for developing switching plans with an electronic version using SVG. The system, NOSTRA (Network Operation Switching TRaining Aid) was developed for ESB's network training school. The web-based package is designed both as an instructional aid and as an assessment tool. The SVG diagram, comprising a synthetic system with a mixture of both 3-phase and single-phase distribution network (including underground cable), transformers, switching kiosks and so on, can be zoomed and panned. A lookup function allows individual pieces of equipment to be identified on the map. Hyperlinks on the network diagram connect to digital photographs describing the equipment at each location.
The web-based interface allows users to select a particular exercise and subsequently a second window is used to enter the switching plan. The plan uses a standard task grammar requiring the user to specify who is performing each action, the location at which the exercise is being carried out, the particular device involved and the name of the operation. Each of these is selected from a drop-down list which is populated with all of the various possibilities. As each step in the switching plan is entered, the user may navigate through the diagram, look up hyperlinked material (procedural manuals, safety rules, photographs of equipment and so on). The SVG diagram is annotated with additional graphic symbols (e.g. earth symbol added) or with colour or other changes to show changing status. Various levels of feedback are possible and switching exercises can be arbitrarily complex, including alternative correct solutions. At the end of the exercise a switching plan conforming to the company's standard is printed. All user inputs are logged to the database.
NOSTRA allows the technician to experiment on a simulation of various training networks used by distribution departments of electrical utilities. It allows the user to create switching plans and can then determine the validity of the plan. The system will also log student performance and actions for further reference and analysis.
The task grammar used adheres to that of the utility - each action requires: (i) Role (ii) Location, (iii) Device and (iv) Operation
The following are the main features:
The network diagram is shown in Figure 2 . Zooming, panning, searching for individual equipment items and locations, updated annotations showing status of flags and so on is discussed below.
A number of technologies, both web-centric and otherwise, have been used in its development. These are outlined in the following sections.
In addition, the ASP engine within IIS makes use of the MSXML engine for XML manipulation and XSLT transforms, both of which are used extensively within NOSTRA.
XML has been employed heavily in the development of this system in both the front and the back end. It is used to store much of the metadata associated with the network diagram, as well as containing the solutions to exercises and the definition of the task grammar. XSLT stylesheets are employed by NOSTRA on the server to transform parts of this data into formats used by various other parts of the NOSTRA system:
SVG has been used for two major user interface elements in NOSTRA:
In basic training, most of the plans involve a fixed number of actions which must be carried out in a specified sequence. For more complex switching operations, there will be some actions which must be completed as part of a plan but where the sequencing is not critical. Additionally there may be equally valid alternative actions. Also there will often be optional actions, which are not strictly required but which could arguably be part of solution.
The utility uses a specific task grammar to describe each step in the switching operation. The overall plan comprises a number of such tasks in a correct sequence. A flow diagram (prepared by the SVG task editor already described) is used to represent the overall plan. The approach used is similar to that employed in [ARRGPK] .
The topology and logic gates used in the flow diagram are used to explicitly define the expert system rules.
While there are a number of functionally similar Expert System shells (environments) available, integrating any such shell with a web-based interface is generally non-trivial. However, two systems are available based on the CLIPS Expert System shell [CLIPS] that ship complete with a network/web-friendly interface:
Because CAPE is not specifically geared towards web operation (being instead more generally network-centric, not concentrating on http protocols), and because it must be compiled before use (a non-trivial task on the Windows platform, as needed for IIS and ASP) WebCLIPS was chosen as the preferred option.
A small Expert System has been prototyped using WebCLIPS for this application. It can:
The Expert System is hosted on the server. This avoids the difficulty of (and considerable limitations placed on) implementing complex software at the client, while also allowing the power and flexibility of an Expert System to be brought to bear on the task.
NOSTRA is made up of three essential parts:
While the web pages that form the user interface are generated on the server, it is client-scripting that is used to implement much of NOSTRA's user interaction.
Some aspects of NOSTRA's user interface, for example, manipulating the SVG network diagram, are only practicable using client-side script. Others, such as the code that manages the tabular display of inputted steps, could easily be performed at the server, reducing the client's workload, but using client-side scripting and DHTML instead makes for a more responsive interface.
Apart from a certain amount of client-side scripting used to implement some user interface, most of the important tasks carried out by NOSTRA are done at the server. The web pages that form the user interface, including the scripting elements referred to in the previous section, are generated dynamically using ASP (Active Server Page) scripts.
The Exercise Editor relies on server-side XSLT processing to dynamically generate SVG based on the steps inputted by the user; again, this is implemented as an ASP page.
An RDBMS database system is used to record all attempts at all exercises for later review and/or statistical analysis.
The Expert System used by NOSTRA, also hosted on the server, responds to user requests as and when they are made, accepting proposed steps and exercise data as HTML form elements and returning results in the form of web pages. In order for the Expert System to be able to function in its assigned role, however, it must be provided with a description of the exercise's solution; this is achieved using another ASP script, which applies an XSLT transform to XML data on the server to generate the correct WebCLIPS-friendly data.
To validate a step, it is necessary for NOSTRA to collate, format and supply the following exercise data to WebCLIPS:
The conversion of an existing CAD representation of the network diagram to SVG would be relatively straightforward; however, to retain as much as possible of the semantic information, the SVG diagram was developed base on a high-level representation of the network objects.
The approach was:
The end result of this process is an SVG diagram depicting the network.
When working on a distribution network, every individual action the technician performs should be recorded and approved before it is carried out. These tasks are defined in terms of four key components: the role, detailing the person responsible for the task, usually the on-site technician or "Operator"; the location of the device being worked on, the device itself - either the name of a device, or (in the case of interconnects) their position relative to other network locations (such as "Pole 2 Side") and finally the operation - the action to be performed.
For a given network, there is a known, fixed, list of locations, and at each location, there is a known list of devices. In turn, there is a known list of actions that can be considered "correct" for a given device. In addition, the manpower requirements for any task to be performed is also known, allowing a list of Roles to be drawn up. Using this information it is possible to draw up four lists detailing every possible role, location, device and operation, that can as a result define any task to be performed on the network they describe. This is known as the system's task grammar.
Each role, location, device and operation is assigned a unique number; this simplifies all references to the system's task grammar.
Of course, not all combinations of these four properties are valid - for example, not all device types will be available at a given location, and not all operations are valid for any given device. While this may be apparent while on-site, this is not necessarily the case when performing the same task on a simulated environment. As such, it is necessary to provide the trainee with some assistance in this regard, by filtering what inputs they can specify to remove nonsense combinations. However, in an effort not to oversimplify matters, the filter will allow a certain proportion of incorrect combinations - "false positives" - chosen by the trainers in the belief that they may prove convincing to trainees - to ensure that the simulation is no easier than the real-life situation it represents.
NOSTRA implements two such filters; one, filtering available devices based on the user's choice of location, and the other filtering operations based on the user's choice of device.
|Any||Cangort 10kV Line Pole 1||Cangort 10kV Line Pole 3||Cangort 10kV Line Pole 4||Coan 10 KV Line Pole 2||Corbally 10kV Line Pole 6||Corbally 10kV Line Pole 8||Corbally||Derry LV Pole 1||Derry transformer|
|Apply Earths||Apply Hold Off Notice||Check For Loss Of Voltage||Check For Voltage||Check Phasing||Check Rotation||Check Stay Wire||Close||Compare Rotation||Cover N/O Notice|
In many situations, the switching plan will involve a linear sequence of tasks. More complicated exercises will involve branching. Logic gates, and, as required, procedural blocks, can be used to connect the tasks.
An example of a more complex exercise is shown in Figure 4 . This shows a plan where there are some optional steps and where logic has to be included to check out the validity of subsequent tasks depending on whether these optional tasks have been performed.
Figure 5 shows the task builder implemented in SVG. The expert system rules are later generated automatically from this description.
In a production environment there would normally be many different switching exercises carried out by a large number of trainees, who could each possibly make more than one attempt at a given exercise. This will generate a substantial volume of data.
The solution employed here is to use a SQL-compliant database to store all this information. In addition to providing reliable, structured storage for the data, queries can be made against the database to generate reports, usage statistics and provide other useful information to the training school.
The developed system can be used in 3 main ways:
After logging in to NOSTRA, and selecting a network, the NOSTRA main screen ( Figure 2 ) will appear. At this point, it is possible to peruse the network map, pan and zoom to get a more detailed view, as shown in Figure 7 , or view details on significant locations on the map by selecting items from the Location List in the top-right of the window and clicking "Details" ( Figure 8 ).
To perform an exercise in NOSTRA, a selection is made from the list at the top-left of the main window.
Once the trainee has chosen an exercise, he/she chooses a level of feedback; in other words, how much intervention NOSTRA will provide while the trainee enters steps. The options are:
Step Level is the most commonly used setting here.
Having specified a feedback level, the steps for the exercise are entered; this is done by specifying the role, location, device and operation for each step and adding it to the list (see Figure 11 and Figure 12 ).
The current state of the switching plan, as it would appear on paper in the field, can be seen by clicking on the "Preview" button; an example can be seen in Figure 1 .
Finally, the exercise can be submitted to the server for storage and/or later examination by clicking "Submit".
These screen captures illustrate selected views of NOSTRA in action.
In the next version of NOSTRA, an explanation facility will be added.
NOSTRA can be used for assessment of the ability of network technicians to generate valid switching plans. In this case immediate feedback on user actions is disabled and the technician gets no feedback until the overall plan has been generated.
In the case of partially correct plans, the expert system is used provide an assessment. As described already all user plans are stored in the database.
The current version of NOSTRA fulfils the original project goals.
The following summarises the main features of NOSTRA:
Some of the suggestions for future work involve incorporating:
Special thanks are due to the trainees at DTTS Portlaoise for their valuable usability feedback.
Thanks are also due to Diarmuid Ryan (ASTech) and Michael Murphy (ESB) for earlier work on a the original NOSTRA system based on DXF graphical elements.
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