In search of power network reliabilityAuthor Jari Åberg
It is of utmost importance for owners and operators of electrical networks to always have up-to-date and accurate knowledge regarding the status and safety of their networks. According to new directives and standards they are required to ensure that basic safety standards are met already in the design phase of projects. When implementing projects abroad unfamiliar standards place additional demands on design. In all cases comprehensive documentation is of crucial importance. New power network calculation software tools on the market significantly ease the design and management of power networks.
The owners and operators of electrical networks have to ensure that their networks are safe to use and that human life and property is protected in all network connection situations and possible failure situations.
Economically efficient networks a primary goal
Power distribution networks constitute significant long-term investments. For this reason it is essential that the network is reliable, easy-to-manage and adaptable to changes in future power requirements.
In order to ensure uninterrupted power distribution the electrical magnitude of the distribution network needs to be calculated and dimensioned and the results need to be thoroughly analysed. Accurate network calculation avoids the over-dimensioning of network parts and makes room for future needs in the right way.
If the network has been designed correctly it should facilitate quick fault location, enable operators to limit the areas affected by faults and reduce the length of possible resultant downtime. Comprehensive documentation that allows the easy location of device and network information eases the work of operators considerably.
Well-designed protective elements guarantee safety
Failure situations in power networks can occur as the result of adverse weather conditions or inadvertent or deliberate human action. Inaccurate dimensioning can also lead to the overloading of a part of the network and subsequent device failure.
In order to design protective elements that are effective sufficient knowledge of load levels and operational uses of the different parts of the network is required. The method of implementation depends greatly on how different parts of the network are used in different situations.
For some network parts it may be necessary to use temporary connectors to reduce the size of the failure area. Protecting elements should work in these situations as well and should be adaptable to expected increases in future power needs.
Regulations prescribe requirements for failure disconnection in relation to operational time. In other words, the failure needs to be disconnected within a prescribed time depending on the failure type and its effect on the environment. The failure may result in humans touching electrified parts or being exposed to excessive electro-magnetic fields or electric arcs.
Power network protecting elements should be implemented selectively: the area affected by the failure should be minimized as close to the failure point as possible.
New software tools ease network calculation
Designers of electrical networks need to able to quickly manage changing directives and standards. With the help of network design software even large amounts of information can be managed reliably and network changes and additions can be implemented later with ease. Software programs can also be used as supporting tools in e.g. managing connector changes.
Such software packages allow different network solutions to be studied. This allows the optimization of the network’s power distribution and related costs. It also facilitates managing different countries’ IEC standards and requirements, as well as the presentation of calculation materials in the correct formats.
The software enables the efficient management of very large amounts of documentation. The network structure can be described in graphs or scale maps and the shielding can be shown graphically or in tables.
An example of this kind of software is NEPLAN, which is used in Elomatic’s power network design projects. A particular advantage of the software is that it allows the calculation of both low and very high voltage networks as well as DC networks. This means that it can be effectively used to manage and calculate public distribution networks and factory networks.
In Marine industry electrical and offshore projects different standards apply than those of common power networks. In NEPLAN the standards can be selected before starting calculations, which results in the correct documentation and information for the intended purpose.
Don’t forget the man behind the machine
A software tool is however only that, a tool. It still needs a skilled and experienced power network expert to interpret and analyse the results correctly. By combining advanced software tools and top expertise with reliable initial data about networks and their future requirements both safe and economically viable networks can be designed, implemented and operated.
If project planning has been conducted properly and modern tools have been used in the process the networks should serve both their present and future needs.
The original text was published in our 2/2014 Top Engineer magazine
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