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Title Harmoniske forstyrrelser i lavspændingsnettet, nu og i fremtiden
Translated title Harmonic distortions in the low voltage grid, now and in the future
Author Morrison, Steffan Ladegaard (Ingeniørhøjskolen i København, IHK)
Supervisor Isbrandt, Gunner
Knutz, Boye C.
Jensen, Morten Møller
Institution Ingeniørhøjskolen i København, IHK, DK-2750 Ballerup, Denmark
Thesis level Bachelor thesis
Education Diplomingeniør, Stærkstrøm
Education Bachelor of Engineering
Publication date 2010-06
Abstract Today there are no major problems with harmonics in the electrical low voltage grid, but this might alter in the near future, as it might bring electric cars and heat pumps to the private homes. This report deals with a part of the problem, as heat pumps can provide emissions of harmonic currents in the low voltage grid
The report contains a theoretical part, which gives the reader an understanding of the concept of harmonic currents and voltages. After the theory part, a method for measuring harmonic current and -voltages in the low voltage grid is described. A series of measurements performed in a se-lected low voltage grid, consisted of up to 40 data sets, with minimum, average and maximum values for all three phases. To handle all of the data sets a VBA script was coded to automatically generate graphs, which saved a big amount of time. Some of the measurement data were used to form a harmonic base load to use for NEPLAN calculations.
The base load model was the basics for finding the margin, which is also described in the report, between the measured harmonic current and the NEPLAN calculated maximum emissions, re-sulting in a too high total harmonic distortion. The model for NEPLAN to calculate on was made using LineTrace, which makes low voltage grids graphical, and shows the necessary informa-tion’s for each element in the grid, needed by NEPLAN.
After that, two fictitious heat pump loads was invented to use in NEPLAN, with the emission limits set by the standards for items respectively below and above 16A. The heat pumps were modeled in the grid, with a penetration of 34 %, distributed across customers. Then new margins were calculated, and describing how much more emissions from heat pumps the grid can handle, without exceeding the standard for voltage quality at the point of delivery.
The report contains three cases. Case 1 shows margins from the current level and up to the limit of the grid. Case 2 shows the margins at a given penetration degree of small heat pumps. Case 3 shows the margins at a given penetration degree of large heat pumps.
To confirm whether the harmonics represents actual problems, before other criteria’s like load currents in the cables and voltage levels at the point of delivery. The load current should not be exceeding the cables maximum current value and the voltage level should be no less than 90 % of 230V. Calculations for these two criteria’s have been made, to ensure the values are not reaching the limits.
After the margins have been calculated, an analysis of future loads in the private homes has been made, to see what might need a closer look in the near future. In the perspective section, rec-ommendations for future measurements and work have been made.
Finally there’s a conclusion to the problems and questions described in the report.
Pages 91
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Admin Creation date: 2010-06-08    Update date: 2013-07-10    Source: ihk    ID: ihk-6797355    Original MXD