FEATURE ELECTRICAL DESIGN SOFTWARE Protection moves with the times
Many readers of Electrical Engineering magazine will probably remember a time when protective device manufacturers printed time current characteristics for each device on a sheet of tracing paper. Noel O’Connor of Amtech suggests a better way
T
he sheets of tracing paper previously used for protective
devices would traditionally have to be placed on top of each other to provide a rudimentary system for determining the circuit co-ordination. Although this fairly basic procedure
worked, it was certainly a system that had a number of limitations. However, modern electrical design software offers a better approach. This is particularly true when using modern adjustable breakers which concern many elements within a protection curve. In these circumstances, tracing paper would have no chance. At the same time, of course, adjustable devices offer some very clear benefits. In particular, they enable the designer to tailor the protection characteristics to the circuit it protects. This potentially reduces the overload setting on a protective device and reduces the required cable size accordingly. So getting around this challenge by
simply avoiding the use of adjustable breakers isn’t really a viable or sensible option. The answer is to find an easy way of working with these devices - and the more advanced software packages will do just that. In fact, they make the process so easy and intuitive that you can often involve more colleagues in the process and make better use of your in-house resources. As a result, there is less need to sub- contract protection co-ordination. A further benefit is that any changes to the specification are quickly accommodated in the software.
HOW DOES IT WORK? Some software packages make it very quick and easy to select the exact device you are using by incorporating a large database of protective devices. Once the device has been selected it can then simply be dropped into the system. Clearly this is a vast improvement over using ‘generic’ devices. Another advantage is that the time current characteristic for each device stored in the software is supplied direct from the device manufacturer -
8 SEPTEMBER 2014 | ELECTRICAL ENGINEERING
In fact some software will go as far as automatically determining the overload settings depending on the design current in the circuit. The purpose of this type of software is to turn complex, time consuming tasks into simple and far more intuitive processes, such as validating adjustable breakers in seconds with complete confidence that your calculations are accurate. Nor do the benefits end there, as not only can the time current discrimination be shown visually on screen, the whole circuit can also be checked instantly at the touch of a button. The beauty of this is that it
accommodates familiar ways of working, so you design your project in the usual way, typically building a schematic by selecting symbols from the on screen library and dragging them into
the project on screen. The software contains a large database of
Above and below: many of the people who use electrical design software on a regular basis are unaware of the sort of capabilities it is capable of
eliminating tedious searches through catalogues. Some packages even include manufacturers’ data sheets and graphical trip unit images. In terms of ease of use, it is also very
important that adjustments to protective devices can be made very simply within the software. One method that is proving particularly popular is to use a simple graph view of the devices in the circuit, with the characteristics of each device shown on one screen alongside another. This method allows overload, short circuit, instantaneous and earth fault settings to be changed simply by increasing or decreasing the values on screen until the co-ordination is acceptable. All of the changes are reflected instantly on-screen so you can continually see the effects of any adjustments as you make them.
cables, busbars and protective devices so these can be easily selected and added instantly to the project. Again, the specifications of these components are often supplied from the manufacturers so the information is up to date, accurate and specific to that device. Then, when you are happy with your design, you simply click the ‘Discrimination Check’ button and the software will automatically check the discrimination. If an overlap is found, the software displays one or more error messages. When you click on one of the error messages you are taken directly to the relevant part of the graph so you can see where the error is instantly and rectify it in seconds.
SUMMARY Interestingly, even many of the people who use electrical design software on a regular basis are unaware of the sort of capabilities that have been described here. Spending a little time in exploring the functionality of your system could therefore prove to be a very worthwhile exercise. Of course, if the software you are using does not have this functionality, that may be an argument for looking further afield.
Amtech
www.amtech.co.uk T: 0800 028 2828
Enter 201 / ELECTRICALENGINEERING
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