Ny favoritt jule album,og så har den topp lyd i mine ører
Slakk i draget i dag,men valgte allikevel en av de tyngste motbakkene
Var strømstans noen timer i går.
Dyttet noen målepinner inn i kabelen til poweramp og målte litt,to kurser,den korteste og den lengste.
Dette blir da helt ned til kiosken til netteier.
Her en kjenning,greit med ikke for mange kilder mener nå jeg.
Målingene her er delt opp,ikke som over der det kun måles til endes.
KABLERS PÅVIRKNING
Og her en rapport som også omtaler supraharmonics og kabler,fra Rönnberg og Bollen.
Klipper ut deler,som de av oss som er ufaglærete får ett lite innblikk i hva det dreier seg om,
mye tungt stoff som er for de viderekommne.
To use the term Harmonic together with a prefix is already common practice in the field of Power Quality. The term “Interharmonics” refers to frequency components that fall outside the harmonics, i.e. non-integer multiples of the fundamental frequency. The term “Subharmonics” is often used for frequency components below the fundamental frequency. Adding the prefix supra (meaning above or beyond the limits off 1) when describing components in the frequency range 2 to 150 kHz seems appropriate and coherent with existing terminology within the Power Quality field.
How supraharmonic currents will propagate depend on the impedance at every branch seen by the source, as is the case with currents at any frequency. Considering an installation, like the installation in a detached house, there will be impedances introduced by the wiring, the devices that are connected within the installation and by the grid to which the installation is connected. The wiring will offer impedance that is mostly resistive and inductive. It will vary with length and frequency but it will be static over time (i.e. the impedance will not change with time).
In many cases the impedance of the grid is higher than the impedance of neighboring devices and supraharmonic emission does not propagate outside the installation to any great extent. However, there are exceptions when the grid impedance is small e.g. due to a resonance and the grid is not always “emission free” either.
At the resonance frequency the only thing left to damp a signal is the resistive part of the circuit. Inside an installation like a detached house, capacitances will be present in the form of appliances (in their EMC filter or in the form of the dc-side capacitor behind a diode rectifier) and inductances in the form of wires and some appliances (directly-connnected motors). The resistive elements are present in the wiring and in some appliances (e.g. espresso machines and tea-water cookers). The latter contribution is reducing in number, among others by the replacement of incandescent lamps with electronic lighting. A
In [78] a series of measurements were conducted to see the impact from the wires on the impedance in an installation. It was shown that by varying the length of the wires (and as a result also the inductance) to an appliance equipped with a capacitor at its terminals the frequency dependent impedance changed consequently. The length of the power cord was altered from 0 to 46 meters and as a result the frequency with minimum impedance shifted from 78.6 kHz to 38 kHz, all the time within the supraharmonic range. In [79] it was shown that a common mode resonance is likely to occur in the frequency range 2 to 150 kHz between parallel connected EMC-filters.
Based on the theory that the wires in an installation can have an effect on the resonance in the higher frequency range, some calculations and simulations were performed. In all cases the appliances are considered as a current source behind a capacitor, in the same way as in [15]. The case of a single appliance connected to the grid via a wire is shown in Figure 23 where I0 and C1 represent the appliance responsible for the primary emission, L1 represents the wire, R1 the wave impedance of the grid, R2 and L2 the low frequency resistance and inductance of the grid. The impedance of the grid, ZGrid would hence be R1 in parallel with R2 and L2 and the external impedance, Zext, seen by the appliance consequently a series connection of L1 and ZGrid.
A longer wire would shift the resonance peak to a lower frequency and somewhat increase the amplification. Both transfer function and transfer impedance show a decrease with increasing cable length.
When a second appliance in form of a capacitor C2 is connected, through a wire with inductance L3; as shown in Figure 24 an additional resonance frequency will appear.
As seen in Figure 25 it is feasible that the connection of a second appliance will create a resonance point at a frequency between 10 kHz and 20 kHz; moreover the simulations show that the length of the wire will shift this resonance frequency. The figure also shows that depending on the length of the wire connecting the second appliance, the primary emission from the first appliance can vary by a factor of more than 10. The primary emission from an appliance can thus not be considered as constant, but instead it depends on the properties of the grid and of other appliances connected in the neighborhood.