IEC 61660-1:1997 pdf download – Short-circuit currents in d.c.auxiliary installationsin power plants and substations – Part 1: Calculation of short-circuit currents

IEC 61660-1:1997 pdf download – Short-circuit currents in d.c.auxiliary installationsin power plants and substations – Part 1: Calculation of short-circuit currents.
This part of IEC 61660 describes a method (or calculating short-circuit currents in d.c. auxiliary systems In power p’ants and substations. Such systems can be equipped with the following equipment, acting as short-circuit current sources:
— rectifiers in three-phase a-c. bridge connection for 50 Hz;
— stationary leadacld batteries;
— smoothing capacitors;
— d.c. motors with independent excitation.
NOTE — Rectillets in Ihree.piase ac. bridge connection for 60 Hz are under consideration. The dale ol other equipment may be eiv.n by th. nianufc1ur.r
This standard is only concerned with rectifiers in three-phase a.c. bridge connection. It is not concerned with other types of rectifiers.
The purpose of the standard is to provide a generally applicable method of calculation which produces results of sufficient accuracy on the conservative side. Special methods, adjusted to particular circumstances, may be used if they give at least the same precision. Short-circuit currents, resistances and inductances may also be ascertained from system tests or measurements on model systems. In existing d.c. systems the necessary values can be ascertained from measurements taken at the assumed short-circuit location. The load current is not taken into consideration when calculating the short-circuit current. It is necessary to distinguish between two different values of short-circuit current:
— the maximum short-circuit current which determines the rating of the electrical equipment;
— the minimum short-circuit current wtiich can be taken as the basis for fuse and protection ratings and settings.
1.2 Normative references
The following normative documents contain provisions which, through reference In this text. constitute provisions of this part of IEC 61660. At the time of publication, the edition indicated was valid. All normative documents are subject to revision, and parties to agreements based on this part of lEG 61660 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below Members of lEG and ISO maintain registers of currently valid International Standards.
lEG 60038: 1983, IEC standard voltages
lEG 60896-1:1987. Stationary lead-acid batteries — General lequirements and methods of test
— Part 1: Vented types Amendment 1 (1988) Amendment 2 (1990)
IEC 60909: 1988. Short-cIrcuit current calculation in three-phase a.c. systems
lEG 61660-2: 1997. Short-circuit currents in d.c. auxiliary installations in power plants and substations — Part 2: Calculation of ellects
1.3 Definitions
For the purpose of this part of IEC 61660. the following definitions apply.
1.3.1 short circuit: The accidental or intentional connection, by a relatively low resistance or impedance, of two or more points in a circuit which are normally at different voltages.
(1EV 151-03-41J
NOTE — In this standard the connection is assumed to hayS zero impedance.
1.3.2 short—cIrcuit current: An over-current resulting from a short circuit due to a fault or an Incorrect connection in an electric circuIt. [1EV 441.11.07J
NOTE — II is necessary to distinguish between the short-circuit current at the short-circuit location and In the network branches.
13.3 partial short-circuit current: The short-Circuit current at the short-circuit location being fed from one source with all other sources disconnected.
1.3.4 common branch: A network branch with several partial short-circuit currents from different sources.
1.3.5 Initial symmetrical short-circuit current l: The r.m,s, value of the a.c. symmetrical component of a prospective short-circuit current applicable at the instant of short circuit it the impedance remains at zero time value.
1.3.6 p.ak short-circuit current l: The maumum possible instantaneous value of Ihe prospective short-circuit current at the d.c. side (figures 1 and 2>.
1.3.7 quasi steady-stale short-circuit current : The value of the short-circuit current at the d.c. side 1 s after the beginning of the shorl circuit
1.3.8 tIme to peak : The interval between the initiation of the short Circuit and the peak value of the short-circuit current (figures 1 and 2).
1.3.9 short-circuit duration Tk: The time interval between the initiation of the short circuit and the breaking of the d.c. short-circuit current.
13.l0 nominal system voltage U: Voltage (line-to-line) by which a three-phase s.c. system is designated and to which certain operating characteristtcs are referred, Values are given in IEC 60038.