Review of power system simulation software tools

Power system simulation

Man at deskA power system simulation software models the behaviour of electrical networks, from low voltage distribution networks (typically 110 and 240 V) to very high voltage grids (up to 800 kV). They are mathematical models based on the electrical laws, offering a user interface specifically developed to represent networks equipment: substations, transformers, overhead lines, underground cables, generators, including renewable energy sources like wind farms and photovoltaic panels, circuit breakers, SVC, etc.

Large choice

DigSilentIt is difficult to know which are the most used in the world. Network simulation software developers do no publish the number of sold licences. Additionally, they propose different approaches and user interface functionalities, depending on their targeted clients. Utilities have different needs and objectives than consulting engineers or project developers, for instance. Different types of software are therefore available on the market. They all propose same kind of mathematical models (line and cable parameter calculation, load flow, neplanshort-circuit, stability, protection coordination, harmonics, etc.), but the user interface can be quite different.

etapAccording to my experience, the most used include Siemens PSS/E, Neplan, PowerFactory from DigSilent and ETAP. Other are EMTPEurostagCYMENAPPaladin DesignBase, CAPE, cymePowerWorldSimPow and Aspen, for instance. The list is not exhaustive and not ordered. Sorry for the ones that are not in the list. Feel free to add them by commenting this post.

In the past century

The first power system simulation software tools were developed in the 70’s. Some of them survive until today, going through punched cardsDOS, Windows 3.x, Windows 95 and subsequent versions, Fortran and procedural programming languages in general, floppy disksobject-oriented programming and now cloud computing and punch_cardprobabilistic methods. The most famous is certainly PSS/E, originally developed in the USA in 1976, now belonging to the German company Siemens, after being sold and transferred several times.

Thirty years ago, PSS/E reigned supreme amongst a few commercial available software tools. Many electrical engineers developed their own software tool too. Some of them evolved into commercial tools, increasing the number of PSS/E competitors. The majority remained in the office where they were created. The big majority of these tools, commercial or not, were developed in Fortran on DOS.

When Microsoft placed Windows 95 on the market in August 1995, some of the software developers made the effort to upgrade. The majority of them just added a windows user interface, without modifying the calculation modules. A minority took the opportunity to completely redesign their tools. New incomers also showed up with brand new tools. For instance, ETAP claims on its website that “in 1996 ETAP released the first, true 32-bit, power system analysis program on the market for Windows.” I am not sure it is true, but ETAP was surely amongst the Windows 95 pioneers in the power sector. But the real first-movers were the very few companies that developed windows user interfaces for such software on Windows 3.x, in the early 1990s.

mac_questionIt is interesting to note that all commercial power system simulation software tools are running on Microsoft Windows. None is running on MacOS. Is it a potential market for developers?

Tough competition

When the majority of power sector companies finally acquired Microsoft Windows in the late 1990s, early 2000s, software editors were forced to follow the move. PSS/E for instance released its first Windows version only in 2004, almost ten years after the release of Windows 95. And it was not a good one. Some data sets were still defined in per unit, for instance line characteristics (resistance, reactance, etc.). It is known that the power sector is conservative, but concerning IT, it is extremely conservative.

Now, commercial power system simulation software tools are modern and try to make the most of available IT technologies. In fact, natural selection catches up the others, the ones that didn’t evolve.

Better, but not good enough

psse_exportBut for the survivor, there is still room for improvement. The biggest problem for the user is data portability: it is a headache to export and import data between software. There is no standard exchange format. There were some attempt, but they all failed. Every company developed its own database and data organisation. In the best case, they propose import tools from competitors formats. But they are not working well, or they don’t work at all. I know that if power system simulation software editors will read this, they will claim it is not true. But as a user, and an experimented one, I feel comfortable writing it.

User interfaces also need makeover. Menus organisation is often absurd. I was also software developer, I know it is not an easy task, but they should put some effort on it. In a training session on one of these software tools, the trainer, an excellent senior employee working since many years for the editor, couldn’t find the menu activating a special functionality one of the trainee wanted to see. He had to ask several colleagues before finding one who knows where to find the right button on a windows one reaches after many clicks. Not to mention that it was not explained in the user documentation.

I will be nice. I will not show you screenshots showing how old fashion can be some interfaces.

Printing is apparently also a challenge for this type of software. If you succeed to get the font you want, the line thickness you want, the arrow size you want, on the paper size you want, all that at the same time, you are then sure that you are an expert user.

Last but not least, the price

pigI don’t know what is your opinion, but several ten thousands dollars for this kind of software is too much. I know the market is not so big, and they the number of sold licences is limited. But the price is a barrier to acquire more licences. I have seen many companies with one licence shared by several employees, only because it is too expensive to acquire one licence per employee. Declining prices are generally proposed when buying several licences, but the proposed discount is no a sufficient incentive. Opinion from software editors is here welcome to explain us their price strategy.

A quiet revolution 

To finish on a positive remark, let’s look at the progress we made. Forty years ago, it took about a minute for simulating a  medium-sized network, plus the time necessary to prepare the data in the right format in ASCII files. Now, it is possible to calculate hundreds of load flow simulations in a few seconds. And databases allow us to organise the data for us.

Gauthier Dupont
Dupont Energy Consulting GmbH