IEC 61642:1997 pdf download – lndustrial a.c. networks affectedby harmonics – Application of filters and shunt capacitors

IEC 61642:1997 pdf download – lndustrial a.c. networks affectedby harmonics – Application of filters and shunt capacitors.
IEC 61642 gives guidance for the use of passive ac. harmonic filters and shunt capacitors fOr the limitation of harmonics and power factor correction intended to be used In industrial applications, at low and high voltages. The measures proposed In this standard are applicable to harmonic orders greater than 1 and up to and including 25.
The following capacitors are excluded from this standard:
— capacitors for inductive heat generating plants. operating at frequencies between 40 Hz
and 24000Hz (see IEC 601 10 (1J);
— series capacitors for power systems (see lEG 60143 (21);
— coupling capacitors and capacitor dividers (see IEC 60358 (3J);
— power electronic capacitors (see IEC 61071 (4J):
— AC motor capacitors (see IEC 60252 [51):
— capacitors for use in tubular fluorescent and other discharge lamp circuits (see IEC 61048 [6j and IEC 61049 (7J);
— capacitors for the suppression of radio interference:
— capacitors intended to be used in various types of electric equipment and thus considered as components;
— capacitors intended for use with d c. voltage superimposed on ac, voltage;
— capacitors intended for use with arc furnaces.
The obØct of this standard Is to identify problems and give recommendations for general applications of capacitors and ac. harmonic filters in ac. power systems affected by the presence of harmonic voltages and currents.
1.2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All normative documents are subjected to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
IEC 60050(131): 1978, International Electrotechnical Vocabulary (1EV) — Chapter 131: Electric and magnetic circuits
Harmonic currents in power networks are produced, in general, when the loads are non-linear or time-varying. One of the main sources of harmonics in industrial networks are static converters.
There are two groups of converter ac. current harmonics: characteristic and noncharacteristic. The characteristic harmonics correlate strongly with the converter circuit and have a constant frequency spectrum. Their magnitude is approximately in inverse proportion to the harmonic number,
The main sources of non-characteristic harmonics are frequency changers, although small amounts of non-characteristic harmonics can result from system imbalances (voltage and impedance) and imbalance in the converter firing angle
The rectifiers for d,c. drives produce mostly characteristic harmonics.
The effect of non-linear and time-varying loads can be amplified under certain conditions of the electrical supp4y-network, for example by resonances. Depending on the network conditions and on the amplification effect of the resonances, the supply voltage can be distorted even in electrical installations where non-linear and time-varying loads are absent or represent a small part of the total Ut ility power.
Harmonics Increase the losses in power networks and may affect the correct operation of various equipments, in particular electronic circuits.
To keep the harmonic disturbances to an acceptable level, local requirements and national and International standards may specify limits for the harmonic distortion. For the reduction of harmonic distortion, filters can be used.
142 Reactive power
In general, the reactive power flowing in networks is caused by inductive loads and static converters.
In a network the power factor is determined by the most economical use of the distribution system or is imposed by the utility. Penalties may be imposed through the tariff structure for poor power factor. It is therefore advisable to compensate the inductive reactive power by fitting suitable compensating equipments
For power factor correction shunt capacitors are normally used. If there are harmonics in the network, unwanted overvoltages andor overcurrents can appear. In addition, ripple control installations may be disturbed. In these cases, filters can be used in place of shunt capacitors alone.