AS 3851-1991 (R2015)

Abstract

Specifies standard methods for the calculation of short-circuit currents in three-phase a.c. systems, both radial and meshed with and without contribution from generators and motors, which are suitable for either computer or manual calculation.
RECONFIRMATION NOTICE
Technical Committee EL-007 has reviewed the content of this publication and in
accordance with Standards Australia procedures for reconfirmation, it has been
determined that the publication is still valid and does not require change.
Reconfirmed documents cannot be amended, but may be formally revised and a new
edition published.
Certain documents referenced in the publication may have been amended since the
original date of publication. Users are advised to ensure that they are using the latest
versions of such documents as appropriate, unless advised otherwise in this
Reconfirmation Notice.
Approved for reconfirmation in accordance with Standards Australia procedures for
reconfirmation on 18 May 2015.
Reconfirmed documents cannot be amended, but may be formally revised and a new
edition published.
The following are represented on Technical Committee EL-007:
Ausgrid
Australian Industry Group
Energy Networks Association
Engineers Australia
The University of New South Wales

Scope

This Standard specifies a standardized procedure for the calculation of prospective short-circuit currents in the fault for-
(a) low voltage a.c. systems; and
(b) high voltage three-phase a.c. systems, operating at a nominal frequency of 50 Hz.
The procedure is intended to be, as far as possible, in a form to facilitate its use by non-specialist engineers.
NOTE: The procedure is applicable generally to other frequencies close to 50 Hz; however, care should be exercised in the use of frequency-dependent factors.
Except in Appendix A, the basis of the calculation procedure in this Standard is ohmic. Appendix A converts this procedure to per-unit calculation.
NOTE: Worked examples are provided in Appendices D and E on ohmic and per unit basis respectively.
The current, calculated in this Standard forms the basis for the determination of the currents in the paths feeding the fault.
This Standard specifies a standardized method for the calculation of the joule integral (I2t) of a short-circuit current.
This Standard does not cover-
(i) short-circuits deliberately created under controlled conditions as in short-circuit testing stations;
(ii) short-circuits in the electrical installations of ships and aircraft;
(iii) non-simultaneous short-circuits, which can lead to higher aperiodic components of short-circuit current; or
(iv) methods for analysis of short-circuit currents in non-linear systems.

General Product Information

Published
Document Type	Standard
Status	Current
Publisher	Standards Australia
ProductNote	Reconfirmed 18/05/2015. This standard as been reconfirmed in Australia in 2015 and remains current in New Zealand. Reconfirmation Notice 18/05/2015
Pages
ISBN
Committee	EL-007
Supersedes	DR 88077