Improvements in Apparatus for Testing Leakage and Insulation of Electrical Conductors.
Year: 1890

page_text: Date of Application, 2nd May, 1890
Complete Specification Left, 2nd Feb., 1891-Accepted, 25th Apr., 1891
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Testing Leakage and Insulation of
Electrical Conductors.
I, ARTHUR BROMLEY HOLMES, of 36, Princes Avenue, in the City of
Liverpool, Civil Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention has for its object a convenient and simple arrangement of apparatus
for testing the insulation of and leakage from electrical conductors.
The apparatus consists broadly of a voltmeter, an ammeter and an automatic cut-
out combined with a variable resistance fixed in the circuit of the ammeter, also a
registering device by which the indications of the voltmeter and ammeter, or of
either of them, are automatically, continuously or intermittently registered by
clockwork or other means.
The automatic cut-out consists preferably of an ordinary magnetic cut-out
having connected parallel with it a series of resistance coils of known value
and an arrangement for cutting any desired number of these coils out of the
circuit
I may sometimes combine with the above apparatus an indicating device con-
sisting of one or more incandescent lamps connected with the conductors to be
tested and with the earth.
Dated this 1st day of May 1890.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Patent Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Apparatus for Testing Leakage and Insulation of
Electrical Conductors.
1, ARTHUR BROMLEY HOLMES, of 36, Princes Avenue, in the City of
Liverpool, Civil Engineer, do hereby declare the nature of this invention, and
in, what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
This invention has for its object a convenient and simple arrangement of
apparatus for testing the insulation of or leakage from electrical conductors.
The invention is best described by the accompanying diagrammatic drawing, which
represents an actual apparatus.
A, is a board on which a registering voltmeter, a magnetic cut-out, and an
ammeter are arranged as shown; also 3 two-way switches and a resistance coil.
These are connected with the two mains and the earth by means of wires, as shown,
and two lamps, which afford a rough, inspectional test, and safety fuses are placed
on a circuit connecting the two mains. As will be seen by the drawing, switch B
is used to connect either main to switch C. This switch connects the main, which
has been put in connection with it, either with the voltmeter or with the ammeter,
as desired. Each of them is connected, by means of the magnetic cut-out, with
switch D, and, by this means, when desired, with the earth. This switch D can be
used to connect the two-lamp circuit, at a point between the two lamps, with the
earth, as shown. The magnetic cut-out is connected parallel with a series of
resistance coils of known value, and an arrangement for cutting any desired number
of these coils out of the circuit may be provided. As such an arrangement is well
known and in every day use. I have simply shown diagrammatically a single coil to

page_text: represent this series of resistance coils. Both the voltmeter and the ammeter, if
desired, can be provided with a pencil and a web of paper caused to travel
continuously or intermittently by clockwork or other means whereby registration
can be effected. Instead of one voltmeter I may use two voltmeters in series, a
point between the two voltmeters being connected to carth when desired. These
instruments are of the ordinary character, and not of my invention, so I have shown
the diagrammatically.
The method of using the apparatus is as follows:-1st. If it is desired to obtain
a rough inspectional test, the switch D is moved to the position marked lamps, thus
connecting the ronductor which joins the two lamps to earth. Then as one of the
lamps is connected to the positive, and the other to the negative main the relative
brightness of the two lamps indicates roughly the relative insulation resistance of
the two mains. 2nd. If it is desired to obtain the definite values for the insulation
resistancy the switch 1) is moved to the position marked instruments, and in this
position connects one terminal of the voltmeter and one terminal of the ammeter
(through the magnetic cut-out and resistance) to the earth. The witch B is
placed so as to complete the circuit from the instruments to one of the mains, say
the positive.
The switch in it- normal position (which is as shown on the drawing, and
marked voltmeter) completes the connection of the voltmeter in the switch 1 and
consequently to the main.
After the voltmeter realing has been taken, the key C is moved to its second
position marked ammeter breaking the voltmeter circuit and completing the
ammeter cirenit. By moving the switch B to its second position, connection is
made with the negative main and the above tests are repeated. The two voltmeter
readings, taken as above, indicate the ratio of the insulation resistance of the two
mains and the electrical pressure between the two mains being known, the ammet er
readings enable the actual insulation resistame to be calculated.
In the event of a bad earth fault on the mains, the ammeter is protected from
risk of damage from excess current by the magnetic cut-out which breaks the
circuit leaving the only path for the current through the resistance cuils,
The exact resistance of these coils and the pressure between the mains being
known, the resistance of the earth fault can be calculated from the ammeter
readings.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
An apparatus for testing leakage and insulation of electric conductors, consisting
of a voltmeter or voltmeters, an aimeter and a magnetic cut-out or its equivalent,
arranged in one apparatus with the necessary wires, switches, teele ra, substantially
as herein described, whereby the leakage and insulation of either main can be
tested.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Patent Agents for the Applicant.