South Australian Current Regulations South Australian Current RegulationsSchedule 4—Requirements for earthing and electrical protection systems
In this Schedule—
ENA means Energy Networks Association Limited;
listed standards means the standards (both national and international), codes,
guides and other documents, as published from time to time, listed in the
Appendix at the end of this Schedule;
neutral conductor means a conductor or a group of conductors of a multi-wired
system of supply which is maintained at an intermediate and approximate
uniform electrical potential in respect of the other conductors of the same
circuit, or the conductor of a two-wire system that is earthed at its origin;
protective devices or equipment means devices or equipment intended to isolate
the active conductors of a circuit in the event of an electrical fault.
(1) Earthing and
protection systems must be designed to ensure—
(a)
reliable passage of fault and Single Wire Earth Return ( SWER ) load currents
to earth; and
(b)
reliable and speedy operation of circuit protection devices; and
(c)
step, touch and transfer potentials with respect to assets associated with the
circuit are safe; and
(d)
detection and isolation of electrical conditions likely to significantly
increase risk to people or cause significant damage to property,
and so as to comply with the listed standards or achieve, to the satisfaction
of the Technical Regulator, the same or better safety and technical outcomes.
(2) In determining
abnormal electrical service conditions, due care must be given to the
consideration of extremes that may occur, the likelihood of their occurrence
and the associated risks.
All protection equipment must, to ensure safe operational performance, conform
to the listed standards or achieve, to the satisfaction of the Technical
Regulator, the same or better outcomes.
4—Earthing equipment and ancillaries
Earthing systems must be designed to be constructed of material that is—
(a)
copper, copper alloy, stainless steel or some other material having superior
corrosion resistance; and
(b)
electrically conductive.
5—Earthing of low voltage electrical supply networks
(1) The earthing of
low voltage electrical networks of supply must be designed to be a MEN system,
unless otherwise approved by the Technical Regulator.
(2) A MEN system must
be designed so that—
(a) a
continuous neutral conductor connects all customers' premises in accordance
with AS/NZS 3000; and
(b) the
neutral conductor is connected to earth at each distribution substation or
generator.
(3) A direct earthing
system must be approved by the Technical Regulator and must be designed so
that—
(a) a
continuous earthed conductor connects—
(i)
all customers' premises in accordance with
AS/NZS 3000; and
(ii)
the neutral conductor at the distribution substation or
generator; and
(iii)
every surge diverter,
to earth at the generating station or distribution substation only; and
(b) the
earthed conductor is formed from—
(i)
the metallic sheath of an insulated cable providing the
LV supply to the customers' premises; or
(ii)
a separate conductor of an insulated cable providing the
LV supply to the customers' premises; or
(iii)
a separate earthing conductor affixed to structures
supporting the LV supply circuit to the customers' premises; and
(c) the
system is earthed at the substations or generating stations.
6—Earthing of substations
Substations must be designed to have an earthing system that complies with the
listed standards or achieves, to the satisfaction of the Technical Regulator,
the same or better outcomes.
7—Protection systems for low voltage aerial lines and underground lines
Each of the aerial and underground service lines of a transmission or
distribution network must form part of a circuit that is protected by
protective equipment that can isolate each of the active conductors of the
lines.
8—Step and touch potentials and earth potential rise
Uninsulated metal or reinforced concrete that—
(a)
forms part of a circuit in a transmission or distribution network (excluding
the current carrying conductors); and
(b) is
accessible to persons; and
(c) may,
in the event of a primary insulation failure of the circuit, experience a rise
in voltage,
must be effectively earthed to comply with the requirements of the ENA
Guidelines for Design and Maintenance of Overhead Distribution and
Transmission Lines C(b)1, as published from time to time.
9—Installation of earthing and protection systems—general
Earthing and protection systems must be installed in accordance with design
requirements set out in this Schedule and to conform with the listed standards
or achieve, to the satisfaction of the Technical Regulator, the same or better
outcomes.
10—Connections and joints of earthing systems
Terminations to earthing conductors and joints in earthing conductors must be
of a type that utilises materials and techniques specifically developed for
earthing electrical installations so as to comply with the listed standards or
achieve, to the satisfaction of the Technical Regulator, the same or better
outcomes.
11—Mechanical strength and protection of earthing systems
Earthing conductors and other components of an earthing system must be
installed in a manner that provides protection against likely mechanical
damage, inadvertent interference and chemical deterioration.
(1) Protection and
earthing systems must be maintained to be in a safe operating condition.
(2) A system of
maintenance must be instituted for protection and earthing systems and their
components, including—
(a)
predetermined processes to confirm the safe state of components; and
(b)
managed replacement programs for components approaching the end of their
serviceable life.
(3) Maintenance
programs must be carried out in accordance with the listed standards.
13—Inspection and testing of earthing systems
(1) Earthing systems
must be inspected and tested from time to time to ensure that the design
requirements of—
(a)
resistance to the general mass of earth; and
(b)
electrical capacity; and
(c)
step, touch and transfer potentials; and
(d)
corrosion resistance,
are being maintained.
(2) The condition of
earthing systems must be verified by instruments designed for that purpose.
14—Inspection and test results of earthing systems
The results of visual inspections and resistance readings must be recorded and
audited to identify changes that would influence the frequency of inspections,
tests and maintenance.
15—Inspection and testing of protection systems
(1) Protection systems
must be inspected and tested from time to time as required according to the
risk of damage to, or aging of, components or changes in the network
electrical parameters, to ensure that—
(a)
detection sensitivity; and
(b)
speed of operation; and
(c)
discrimination of load currents; and
(d)
co-ordination with other protection systems,
of the systems are being maintained.
(2) The performance of
protection systems must be verified by instruments designed for that purpose.
16—Inspection and test results of protection systems
The results of visual inspections and performance tests must be recorded and
audited to identify changes that would influence the frequency of inspections,
tests, maintenance and replacements.
Appendix—Standards, codes, guides and other documents relating to
earthing and electrical protection systems
|
In this Appendix— (a) ENA
means Energy Networks Association Limited; (b) IEEE
means Institute of Electrical and Electronic Engineers. | |
|
Protection | |
|
All or nothing relays |
AS 2481 |
|
Voltage transformers for measurement and protection
|
AS 1243 |
|
Current transformers for measurement and protection
|
AS 1675 |
|
Low voltage switchgear and controlgear - General rules
|
AS 60947 |
|
Low voltage switchgear and controlgear - Switches, disconnectors,
switch-disconnectors and fuse-combination units |
AS/NZS 3947 |
|
Low voltage switchgear and controlgear - Contactors and motor starters -
Electromechanical contactors and motor starters |
AS 60947 |
|
Low voltage switchgear and controlgear - Control circuit devices and switching
elements - Electromechanical control circuit devices
|
AS 60947 |
|
Low voltage switchgear and controlgear - Control circuit devices and switching
elements - Proximity switches |
AS 60947 |
|
Earthing | |
|
Switchgear assemblies and ancillary equipment for alternating voltages above
1 kV |
AS 2067 |
|
Guide for safety in AC substation grounding |
IEEE 80 |
|
Electrical installations |
AS/NZS 3000 |
|
Relocatable premises (including caravans and tents) and their site
installations |
AS/NZS 3001 |
|
Guidelines for the design and maintenance of overhead distribution and
transmission lines— | |
|
(a) Stay
wires |
ENA C(b)1 |
|
(b) Step
and touch potentials |
ENA C(b)1 |
|
Switchgear assemblies and ancillary equipment for alternating voltages above
1 kV |
AS 2067 |
|
AS/NZS 3835 Earth potential rise - Protection of telecommunications network
users, personnel and plant | |
|
Maintenance | |
|
Switchgear assemblies and ancillary equipment for alternating voltages above
1 kV |
AS 2067 |
|
Electrical installations |
AS/NZS 3000 |
|
Guide to safety in AC substation grounding |
IEEE 80 |
|
ENA Guidelines for design and maintenance of overhead distribution and
transmission lines |
ENA C(b)1 |
|
AS/NZS 3835 Earth potential rise - Protection of telecommunications network
users, personnel and plant | |
|
Testing | |
|
Electrical installations - Earthing |
AS/NZS 3000 |
|
Guide for safety in AC substation grounding |
IEEE 80 |
|
ENA Guidelines for design and maintenance of overhead distribution and
transmission lines |
ENA C(b)1 |