2404
THE NEW ZEALAND GAZETTE.
[No. 48

(e) Bedded and armoured, with or without serving or
braiding over the armour; the bedding, armouring,
and serving or braiding (if any) to be in accordance
with British Standard Specification No. 7.

(f) Sheathed with a closely fitting seamless covering con-
taining not less than 95 per cent. of commercially
pure lead (the remainder consisting of rarer metals)
and in other respects complying with paragraph (c)
of this regulation.

(g) Covered with tough rubber compound in accordance
with the requirements of Regulation 94 hereof.

Paper-insulated Cables.

(h) Sheathed with a closely fitting seamless covering of
commercially pure lead having a smooth exterior
surface and of uniform radial thickness in accordance
with British Standard Specification No. 7.

(i) Lead-covered as in the last preceding paragraph, and
bedded and armoured, with or without serving or
braiding over the armour; the bedding, armouring,
and serving or braiding (if any) to be in accordance
with British Standard Specification No. 7.

(j) Sheathed with a closely fitting seamless covering con-
taining not less than 95 per cent. of commercially
pure lead (the remainder consisting of rarer metals)
and in other respects complying with paragraph (h)
of this regulation.

85. (1) If it is desired to use types of cables insulated
    otherwise than specified in the last preceding regulation,
    sample lengths shall be submitted to the Chief Electrical
    Engineer together with a report from a recognized testing
    authority (such as the National Physical Laboratory in Eng-
    land) as to the behaviour, properties, and life of the insulating-
    materials employed, for consideration by him with a view to
    their use being permitted, provisionally or otherwise, if found
    satisfactory.

(2) Evidence of insulation resistance alone will not be
considered to be sufficient for the purpose of this regulation.

86. (1) Of the types of cables specified in paragraph (a)
    of Regulation 84 hereof, single cables armoured with steel
    wire or tape or encased in a ferrous sheath shall not be used for
    alternating current except in connection with an earthed
    concentric system in which the sheathing forms one conductor.

(2) Where cables of the types referred to in Regulation 84
(c), (f), (h), and (j) are used for alternating current the lead
and return shall be placed as near as possible to each other.

VULCANIZED-RUBBER-INSULATED CABLES, EXCEPT
FLEXIBLE CORDS.

87. (1) Vulcanized-rubber-insulated cables shall be insu-
    lated with a layer of pure rubber next to the conductor, an
    intermediate layer of vulcanizing-rubber, and an outer jacket
    of vulcanizing-rubber. These three layers shall together
    constitute the dielectric, and its radial thickness shall be in
    accordance with British Standard Specification No. 7. The
    dielectric shall be surrounded by a layer of tape, and the whole
    shall be vulcanized together. The maker's name and grade
    of insulation shall be legibly and continuously printed on the
    tape under the outer braiding.

(2) In the case of cables having an outer protective covering
of “tough rubber” in accordance with Regulation 94 hereof
the tape may be omitted, in which case the maker's name
and grade of insulation shall be clearly marked on the cable
at intervals not exceeding 3 ft.

88. Braided cables shall have an exterior braiding of hemp,
    cotton, or jute, thoroughly impregnated with a protective
    compound that will not have any deleterious action on the
    rubber or armouring, as the case may be. The finish of the
    braiding shall be smooth and uniform.

PAPER-INSULATED CABLES.

89. Paper-insulated cables shall be insulated with a covering
    of paper impregnated with a chemically neutral insulating-
    compound. The radial thickness of dielectric shall be in
    accordance with British Standard Specification No. 7.

INSULATION OF FLEXIBLE CORDS.

90. Two kinds of insulation for flexible cords shall be recog-
    nized as standard for the purposes of these regulations—namely
    high insulation and medium insulation.

91. (1) High-insulation flexible cords, the conductors of
    which are composed of plain copper wires, shall be insulated
    by being lapped with cotton and two layers of pure rubber
    overlapped with cotton.

(2) High-insulation flexible cords, the conductors of which
are composed of tin-coated copper wires, shall have such
conductors uniformly and adequately coated with tin free
from all impurities and insulated with one layer of pure
rubber and two layers of vulcanizing-rubber.

(3) The radial thickness of rubber insulation as aforesaid
shall be not less than that specified in column 2 or column 3
of Table VIII in the Third Schedule hereto, as may be required
by the insulating-material used.

(4) Where conductors other than copper are used in flexible
cords they shall be insulated in such manner as the Chief
Electrical Engineer approves.

92. The insulation of medium-insulation flexible cords
    shall be similar to that of high-insulation flexible cords, save
    that in the case of tin-coated conductors the layer of pure
    rubber prescribed by subclause (2) of the last preceding
    regulation may be omitted, and the radial thickness of rubber
    insulation shall be not less than that prescribed in column 4
    or column 5 of the said Table VIII, as may be required by the
    insulating material used.

PROTECTIVE COVERING OF FLEXIBLE CABLES AND CORDS.

93. Flexible cables and cords shall be provided with one of
    the following protective coverings, but none of the coverings
    mentioned in paragraphs (a), (b), (c), and (g) of this regu-
    lation shall be used where the cable or cord is liable to the
    risk of mechanical damage:—

(a) Natural or non-ignitable artificial silk braiding.

(b) Glace cotton braiding.

(c) Hemp, cotton, or jute braiding thoroughly compounded.

(d) Wire armouring, comprising a flexible braiding of
galvanized steel or phosphor-bronze wire, in addition
to the covering specified in the last preceding para-
graph.

(e) Hard-cord braiding in addition to the covering specified
in paragraph (c) of this regulation.

(f) Tough rubber compound in accordance with Regulation
94 hereof applied directly to the insulated core or
to two or more such cores laid up together.

(g) Asbestos or fire-resisting braiding approved by the
Chief Electrical Engineer.

TOUGH RUBBER COMPOUND.

94. (1) Tough rubber compound, when used as a protection
    to vulcanized-rubber-insulated cables, shall form a closely
    fitting sheath filling the external irregularities of the laid-up
    cores in the case of multicore cables and concentric with the
    conductor when single core, and shall be capable of offering a
    high degree of resistance to abrasion, acids, oils, and alkalis.

(2) The radial thickness of this sheath shall not be less than
that specified in British Standard Specification No. 7.

TESTS OF DIELECTRIC OF CABLES.

95. (1) Except in the case of flexible cords, the dielectric of
    cables, insulated with vulcanized rubber or impregnated paper,
    shall withstand the pressure test and other tests specified in
    British Standard Specification No. 7. Subsequent to such
    pressure test, and whilst the cable is still immersed in water,
    the insulation resistance at a temperature of 60° F., after one
    minute's electrification at a pressure of at least 500 volts,
    shall not be less than that given in Table IX in the Third
    Schedule hereto.

(2) In addition, and subject to the tests prescribed by the
last preceding subclause, vulcanized rubber insulated cables
shall be submitted to the following tests: A sample of the
vulcanized rubber, not less than 4 in. in length, shall be cut
from the cable with a sharp knife held tangent to the con-
ductor. Marks shall be placed on the sample 2 in. apart.
The sample shall be stretched until the marks are 6 in. apart,
and then immediately released. One minute after such
release the distance between the marks made as aforesaid
shall be measured, and if the distance between them is then
more than 2⅜ in. the cable shall not be used. If such distance
is not more than the said 2⅜ in. the sample shall then be
stretched, and if it breaks before the marks are at least 9 in.
apart it shall not be used.

96. The insulation resistance of each insulated conductor
    of a multicore cable, except flexible cords, shall not be less
    than that given in the said Table IX for single conductors of
    the same sectional area.

97. The insulation resistance of the dielectric separating the
    two conductors of a concentric cable shall not be less than that
    given in the said Table IX for single conductors having the
    same diameter as the inner conductor.

98. (1) Except in the case of high-insulation cords with
    vulcanized-rubber insulation as specified in Regulation 91
    hereof, the dielectric of multicore flexible cords shall withstand
    for fifteen minutes the alternating pressure and frequency set
    out in column 3 of Table X in the Third Schedule hereto
    for the respective kinds of insulation indicated therein. The
    test shall be made between conductors, and the flexible cord
    shall be in a dry state at the time of test.

(2) In the case of high-insulation cords with vulcanized-
rubber insulation the test shall be made between each con-
ductor and earth. Any conductor not under pressure shall