|DESS 7||Overview||Why Use DESS|
DESS is comprised of a series of individual modules which are available independently so that you can license only what you need. The core editor/display module is required, but each of the analysis modules is optional depending on your needs. The modules in DESS are:
Core Module (required) – functionality for editing data, viewing maps and viewing and saving analysis results
Load Flow Analysis Module – load flow, motor starting, SCADA load flow and related analyses
Feeder Analysis Module – capacitor optimization and phase balancing
Open Point Optimization Module – optimization of open points (including switches) for loss reduction
Short Circuit Module – fault analysis to determine fault currents and impedances
In addition to the main modules listed above, DESS also allows the creation of plugins which provide additional custom functionality. Available plugins are described here.
The Core Module in DESS provides the main interface for entering and editing data, and also provides access to running and showing results for the different analysis modules. All licenses must include a DESS Core Module.
Geographic Representation and Mapping
By default, DESS shows electrical system data using a geographic view. This allows you to display background maps (produced using GIS or CAD systems) containing streets, land parcels and other points of interest. This also means that as you draw new lines, the lengths are automatically measured. You can display coordinate systems of X,Y metres, yards, feet (including for use with UTM earth projections) as well as latitude/longitude. If desired you can also create a schematic system view with manually entered line lengths.
Data Entry and Editing
Although data can be imported from GIS, you will need to manually edit the data to enter small systems or for what-if type analyses. Manually adding and editing data is quick and intuitive. It is as easy as drawing a network of nodes (busses) and connecting them using lines (conductors). Then add electrical system elements such as loads, transformers, regulators and switches. Repetitive data entry for common technical data such as conductor and transformer parameters is avoided by referring to a library of reference data that is user editable.
Circuit Tracing and Queries
Connectivity through the system data is handled invisibly and automatically updates itself as you add or edit lines, switches or phasing. The robust connectivity model handles the most complicated cases, including 3-phase to single-phase to 3-phase connectivity and partially opened 3-phase switches.
A collection of tracing and query tools make it easy to query your data for items of interest (e.g. find all 50kVA transformers or all red phase underground lines) and to make bulk changes to data values (e.g. change a group of conductors to a different size). Queries include up and downstream tracing, selecting network loops and de-energized sections and custom selection using any data property. This type of functionality is critical to working with large sets of data (i.e. most distribution systems).
Intuitive User Interface
DESS provides a simple yet powerful interface for editing data and understanding result data. The uncluttered main window uses a modern interface design for familiarity and ease of use. Features such as slide out sidebars, mouse-overs and mouse wheel support provide quick access to data with minimal clicking. Decluttering, colored themes, customizable labels and transparency allow you to control which data is shown and how to show it. Tooltips, a useful help system, and undo/redo help you get your data entered and correct mistakes.
DESS lets you enter and view time-current curves for overcurrent protection. A library of curves is defined for a range of common devices, and data for new devices is easy to add. You can use the light table view of the protection data in conjunction with the short circuit analysis to help ensure that devices coordinate correctly.
DESS gives you a wide range of features for controlling the appearance of the system. The visibility and transparency of each map layer can be controlled. You can choose custom rule-based symbols (symbol, size, color, etc) for any item in the system, and you can choose custom styles for lines. This allows you to set up a DESS system to appear exactly the same way you currently view your data.
DESS provides a range of tools to help you view and interpret results from analyses. Thematic displays show data such as voltage or current on coloured overlays and make it easy for you to identify problem areas in your system. Mouse-overs show detailed data for each node and line in the system allowing you fast access to detailed data without lots of clicking or cluttered screens. HTML based reports provided formatted printable results for you records. You can also export results to a file or to the clipboard for use in other software.
Load Flow Analysis
The load flow analysis is probably the most important tool for system planning and design. Given system configuration, supply voltages and loading, a load flow analysis will calculate voltages, current flows and losses throughout the entire system. This module contains a normal load flow analysis along with a number of other analyses based on the load flow including motor starting, an ‘energy’ load flow and a load flow that incorporates real measurement data for improved accuracy.
The Load Flow Analysis in DESS allows you to determine conditions including voltage, current flow and losses for all points on the system. The modeling for this analysis (as for all analyses in DESS) fully represents single-phase and unbalanced components. Detailed modeling for voltage regulation, distributed generation and capacitor bank control is also included. Powerful load modeling with load curve definitions allows you run the analysis for a full range of load conditions for different times of day and different seasons and not just peak load.
The Load Flow Analysis is the key tool for system planning and for identifying problem areas on a system. The load flow analysis lets you evaluate the voltage profile of a feeder under different conditions. You can also find overloaded lines and evaluate the effect of different conductoring. You can compare the losses of different supply options to new loads, test the effects of distributed generation, simulate voltage conversion on older parts of the system or evaluate a proposed new substation. As you perform these types of evaluation the load flow results will provide you with the accurate data you need to confidently plan improvements to your distribution system and justify the decisions you make.
DESS uses a sweep type algorithm for solving the load flow. For distribution networks this gives a number of advantages over traditional generic algorithms such as Newton-Raphson and Gauss-Seidel. Naturally, it also solves networked and looped systems. Stability is excellent even on systems that are traditionally hard to solve, and performance is very good even on large systems (50,000+ busses).
Motors, especially induction machines, can draw substantially higher loads under starting conditions. The Motor Starting Analysis helps you to determine the voltage conditions on the system during starting and to compare voltages before and during starting in order to identify the magnitude and location of sags on nearby parts of the system. You can control the starting parameters of the motor and you can also include generators or multiple machines in the starting simulation.
Annual Load Flow
The Annual Load Flow analysis works by running a series of load flows covering every loading condition throughout a year. Instead of looking at a single condition like the basic load flow, you can now look at the range of voltages you will see at a specific point, the range of currents on a line, and the total energy lost to line or transformer losses. This allows you to calculate energy consumption and losses in a way which can be useful for life cycle economic costing.
The losses on a system caused by an individual load vary depending on where that load is located and on the location of other loads and the existing feeder structure. The Load Loss Analysis calculates the percentage real and reactive system losses caused by an incremental load at a specified location. This can help with an economic evaluation of the lifecycle cost of losses associated with a load. This is especially important in a jurisdiction where these costs are passed on to the customer or need to be justified to a regulator.
SCADA Load Flow
The SCADA Load Flow Analysis lets you supplement the default load model in DESS with a set of real measurements (e.g. from SCADA data). This additional data is used to dynamically scale supplied loads in order to match the measured values. For example, a default load flow might predict a current flow of 120A on one phase of a feeder. If the real measurement data recorded a flow of 100A, then all the loads downstream of that point would be dynamically scaled so that the resulting feeder current matched the measured value.
Simulating real system loads is one of the biggest challenges in system modeling. Even though DESS provides detailed load modeling for representing typical load changes over a day or a season it cannot capture inherent day to day variation. By combining real measurement data with a model built on historical data you can create a very accurate snapshop of the system at any given point in time. The algorithm used by DESS can match current flow, real and reactive power flows and multiple measurements along a feeder can be used simultaneously where data is available.
The Feeder Analysis Module contains analyses to help improve the design and operation of feeders in a distribution system. This includes optimization tools such as Capacitor Optimization Analysis and Phase Balancing Analysis.
Capacitor banks can help to reduce losses and improve voltages on a system. The Capacitor Optimization Analysis helps you find the optimal location for placing capacitor banks in order to reduce losses. It allows you to specify the size and constrain the maximum number of banks you want to allow, and it then determines where these banks should be located.
There are a number of different parameters you can set to control the optimization. You can choose to use only fixed capacitor banks or to allow switched banks. You can optimize for a specific loading condition or for the full range of yearly conditions. You can restrict capacitor placement to a single feeder, station or voltage, or can allow placement anywhere in the entire system. The analysis results show the incremental effect of each additional bank so you can easily identify which banks produce the greatest improvement.
The Phase Balancing Analysis is used on three phase systems that contain single-phase spurs or loads. It recommends changes to the system to reduce feeder imbalance. Unbalanced feeders have increased losses, reduced capacity and can lead to poor power quality.
The algorithm finds the best changes to spur or distribution transformer phasing that reduces losses. The result is a feeder that is optimally balanced along the entire length of the feeder, not just at the substation. The benefits of this analysis can be realized without any capital investment.
Open Point Optimization
Most distribution systems are organized into a radial network in order to make the system more practical to operate. The selection of open point location has a powerful effect on the losses and voltage profile of the system. The Open Point Optimization Analysis recommends the best changes to make to open point locations in an existing distribution system in order to reduce real power losses.
The analysis lets you choose whether to optimize either existing switches, or to allow the evaluation of new open point locations. By comparing these two options you can determine whether the addition of new switches is required and is cost-effective. You can choose how many switch changes you want to consider and the algorithm will find the best changes. The analysis also lets you specify the maximum allowable loading on conductors and transformers.
To try to optimize manually is relatively simple for a single loop (one switch). However, on a complete system with many switches, the problem becomes exponentially more complex. On a modest system with 100 open points you would have to test around 10^60 different alternatives to identify the true optimum. The optimization module of DESS uses an efficient optimization technique to find the best switching configuration. This advanced technique allows you to optimize a complete system, including all supplies and all voltage levels simultaneously, even for systems with thousands of switches. This is very important because changes to flows on one feeder affect neighboring feeders, and changes to feeders of one voltage will affect connected feeders at other voltages. You cannot obtain a true optimum state for a system unless you optimize the entire system at once. This module does just that, quickly and accurately.
The primary benefit of optimizing the location of open points is to reduce losses without the need for any capital investment. Series losses on a typical distribution system can be 2-4% of the total energy delivered. The loss reduction achieved by optimizing the open points can be substantial and is frequently greater than can be obtained from more capital-intensive loss reduction strategies such as use of capacitor banks or reconductoring. The greatest benefits can usually be realized on systems with larger numbers of open points and more meshed networks. Other typical benefits of open point optimization include a flatter system voltage profile and a system configuration where feeders have an increased capacity to pick up extra load. Use of this analysis alone can provide a very attractive return on investment for analysis software.
The short circuit module helps you determine how the system will behave under fault conditions. The results of the analyses are key to designing and setting protective devices to protect your system and protect equipment and personel. Results of these analyses also form the basis for conducting protection coordination and arc flash studies.
General Short Circuit
The general short circuit analysis determines fault currents and impedances due to system faults. The results of the analysis include fault currents for all types of fault (phase-ground, phase-phase, 3-phase and phase-phase-ground) along with the Thevenin impedances of the faulted system.
The short circuit analysis gives results for maximum and minimum fault levels at each node included in the analysis. DESS allows you to specify both maximum and minimum source impedances when representing supplies from the transmission system and you can also choose whether to automatically exclude generation and motors when calculating minimum fault levels.
You can also choose to use values based on ANSI/IEEE C37 fault analysis or to use IEC 60909 correction factors when calculating fault values.
Specific Short Circuit
This analysis provides detailed information for system conditions during a specific fault condition. You choose the fault condition by specifying the location of the fault, the type of fault (phase-ground, three-phase, phase-phase, phase-phase-ground) and the faulted phases. You can also choose whether to calculate conditions for a bolted fault or for a specified fault impedance.
The analysis determines the fault paths and currents and voltages along these paths. If the system contains multiple sources of fault current (such as networked systems, large motors or distributed generation)then it shows the contributions from each source and the path of the current.
The fault current results can be used to set overcurrent and directional protection, and the voltage results can be useful for choosing settings for undervoltage relays.