Improved Means for Securing Safety in Electrical Supply Systems.
Year: 1891

page_text: Date of Application; 16th Mar., 1891
Complete Specification Left 16th Dec. 1891-Accented 12th Mar. 1892
PROVISIONAL SPECIFICATION.
Improved Means for Securing Safety in Electrical Supply Systems.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, Electrician, do hereby declare the nature of this invention
to be as follows:-
:―
In order to obtain increased safety in the working of electrical supply systems
I provide means for preventing undue rise of pressure between the poles of a
circuit or between a circuit and earth and for indicating whenever a leak occurs.
I effect this by providing :
―
1. Apparatus which will disconnect the circuit from the supply mains on an
abnormal rise of pressure, from any cause, occurring between its two poles.
2. Apparatus which will disconnect it from the supply mains on one of the poles
becoming connected to earth, or on one of the poles having a higher potential
above earth than normal.
3. Apparatus which will put a circuit to earth when its pressure above earth
exceeds a given value.
4. Apparatus which will put either one or both poles to earth through an
abnormal increase of pressure between the two poles, occurring, or a leak occurring
from one pole.
5. Indicators, with or without relays, which will show leakage from a branch of
a parallel system.
6. Apparatus, which on a leakage from a branch or a circuit exceeding a certain
amount, will cut out that circuit from the main supply system.
7. Apparatus which will show to an inspector whether a circuit is properly
insulated.
8. Small subsidiary transformers, for magnifying the effects of increased current
through fuse wires, caused by either an abnormal increase between the two poles
of the circuit, or through a leak from one pole.
To effect this employ a fuse wire which may be coupled at its centre to earth
and placed in series between two impedence or resistance coils placed as a shunt
across the poles of the circuit to be protected to normally retain out of action
contact apparatus which when allowed to come into action short circuits the poles
of the circuit and puts them to earth and may at the same time actuate a throw
off switch to disconnect from the supply mains. The fuse wire may be employed
to hold up a heavy weight, spherical conical or of other suitable shape hanging
over two or more contact pieces so arranged that when the weight falls it shall
rest on these contacts-or a spring might be used instead of depending on
gravity.
The action of this device is as follows:-
In the first place should an abnormal rise of pressure take place between the
two poles the current through the resistance and fuse wire, connected across the
secondary, will be abnormally increased, the wire will then break and the suspension
weight will fall on to the contacts connected to both poles of the circuit, thus
short-circuiting them and causing the main converter fuse to go, or actuating a
throw off switch to disconnect from the maius at the same time the weight
being now or already connected to earth puts the whole circuit into good con-
nection therewith.
Should an earth occur on either side of the circuit the pressure between the
centre of the fuse wire and the good pole of the circuit will be increased abnormally,
or in other words an abnormal current will flow from one end of the fuse wire to

page_text: its centre-this will cause the wire to break and the weight to fall and effect the
protection mentioned above.
Should a connection occur between the primary and secondary and there be
an earth on either side of the primary the fuse wire would again break owing
to there being a greater difference of pressure between the fuse and one or both
of the secondary poles than normal.
Instead of using impedence or resistance coils on each side of the fuse wire, the
fuse wire may be connected to the secondary poles of a small subsidiary trans-
former the primary of which is fed with current from the circuit to be protected
and put to earth at its centre. Or two small transformers the primaries of which
are in series can be used the secondary of each holding up by a fuse wire a plug
or other contact mechanism. Then on either of these fuse wires going its plug
will short circuit the circuit poles.
By this means the waste of energy in the resistances on each side of a fuse wire
is avoided and by suitably winding the small converter or converters the quantity
of current passing through the fuse wire or wires can be multiplied to any
extent thus enabling a rise of pressure which without the transformer or trans-
formers would not fuse a very extremely small fuse wire to be so multiplied as
to fuse a wire of sufficient strength as to be commercially practicable.
In installations or circuits when one pole is put to earth then similar apparatus
could be used but in that case it would only work with a rise of pressure above
normal.
Instead of the fuse and weight or spring, the passing of current through the
impedence coils or through a subsidiary transformer may either with or without a
relay be made to actuate contact mechanism in other ways for effecting the above
objects or may actuate an indicator or sound an alarm to call the notice of
attendant.
An installation leak detector may be made on similar principles and may be
described as follows:-The centre of the secondary of the transformer feeding
the installation circuit or the electric centre of the generating or transforming
apparatus used (by electric centre I mean the point which is at the same potential
as carth) is put to earth through the primary of a very small subsidiary trans-
former, the secondary of which is connected to two ends of a short piece of fuse
wire, which supports in the manner described above a heavy metallic weight or
other contact mechanism above two or more contact pieces. Two of these are
respectively connected to the poles of the circuit it is desired to protect, and the
weight or the third is connected to earth. Now should a leak occur on one of the
poles of the circuit the current will pass through this leak and back to the centre
of the house transformer through the primary of the subsidiary transformer and
will generate sufficient current to pass through the secondary of this latter
transformer and through the fuse wire to cause the fuse wire to break and let go
the weight, which will then short circuit the two poles and put them to earth, at
the same time causing the main transformer fuse to go and cut off the installation
from the main supply.
Or in place of the electric centre being put to earth through the primary of a
small converter it may be put to earth through a fusible wire to earth the fuse
wire being arranged to support a weight over 3 contact points, 2 of which arc
connected to the 2 poles of the circuit, and the 3rd to earth; then on a leak
occurring on either pole, the current through the fuse wire will increase and fuse
it the plug falling to short circuit the poles of the installation, and thereby cause
it to be cut out. Other forms of switch may also be used instead of the weight
to effect the same objects.
Instead of having to connect the centre of the tran-former directly to earth, the
following modification of apparatus can be used.
Two small subsidiary transformers with their primaries in series connected
across the poles of the circuit and put to earth between the transformers and with
their secondaries in series, but these latter opposing one another, and in series

page_text: with a small fuse wire, then on the pressure between the poles of the two primaries
being equal no current can flow through the secondaries, and through the fuse
wire in series with them, but on the least difference in pressure between the two
poles of these two transformers occurring current will flow through their secondaries
and on this arriving at a definite amount the fuse wire will go, causing the plug
or switch to drop and short circuit and put to earth the installation. This arrange-
ment is obviously a more sensitive form than the single transformer. Another
additional protection can be effected by making the first and last turns of the
primary of very thick wire, and in close contiguity with one another, the middle
turns being of thin wire. Should a sufficient current go through these transformers,
and the fuse or apparatus from some cause refuse to act, then the fine wire of the
little transformer will be burnt up, these thick turns will short circuit one another
and put the installation to earth through no resistance.
:
In cases where the electric supply is from a station at a distance and where
the current is sent by a conductor which is enclosed by the return and which
return is lightly or less insulated than the inuer one or lead and makes good earth
at one end similar safety mechanism may be used to put the other end to earth
in case the outer insulation is strained above the pressure due to loss on the line
by the inner conductor or a current therefrom going to earth through the
apparatus. The outer or protecting tube which contains the conductors I also
use for making an additional earth to which all the earth connections may also
be made.
The difference between ingoing and outgoing currents may also be made to give
indication of any leakage to earth taking place either by telephone if alternate
currents are used or by ringing a bell or actuating other indicator either direct or
through a relay.
For example a telephone may be placed between two coils one on one main and
the other on the other. With equal currents in both the telephone would not
sound but if a leak took place to earth the telephone would at once commence to
rattle or a coil with fuse or relay or alarm apparatus might be placed between
he two coils instead of the telephone.
Similar means to those hereinbefore described may also be used for ensuring
afety when working with continuous current circuits.
To enable an inspector or householder to tell whether the circuits are in good
rder, a three coil transformer can be used the two poles of the house circuit
assing through two of them but in inverse directions and the third being con-
ected to a telephone or other apparatus. On the current going in and ont of the
nstallation being equal there will be no sound in the telephone, but on their
ecoming unequal by reason of a fault through one of the leads, more current will
o in at one coil than goes in at the other, therefore current will be generated in
he 3rd coil, which will either sound a telephone, work a relay or solenoid switch,
the two poles of the circuit may be passed through a differential coil, and on
inspector applying a form of portable suspended needle in the centre of this
il, he would be able to find out whether the ingoing current is equal to the
tgoing current.
Dated this 16th day of March 1891
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improved Means for Securing Safety in Electrical Supply Systems.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, Electrician, 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 :-
In order to obtain increased safety in the working of electrical supply systems 1

page_text: provide means for preventing undue rise of pressure between the poles of a circuit
or between a circuit and earth and for indicating whenever a leak occurs.
I effect this by providing
1. Apparatus which will disconnect the circuit from the supply mains on an
abnormal rise of pressure, from any cause, occurring between its two poles.
2. Apparatus which will disconnect it from the supply mains on one of the poles
becoming connected to earth, or on one of the poles having a higher potential above
earth than normal.
3. Apparatus which will put a circuit to earth when its pressure above earth
exceeds a given value.
4. Apparatus which will put either one or both poles to earth through an
abnormal increase of pressure between the two poles, occurring, or a leak occurring
from one pole.
5. Indicators with or without relays which will show leakage from a branch of a
parallel system.
6. Apparatus, which on a leakage from a branch or a circuit exceeding a certain
amount, will cut out that circuit from the main supply system.
7. Apparatus which will show to an inspector whether a circuit is properly
insulated.
8. Small subsidiary transformers, for magnifying the effects of increased current
through fuse wires, caused by either an abnormal increase between the two poles
of the circuit, or through a leak from one pole.
To effect this employ a fuse wire which may be coupled at its centre to earth
and placed in series between two impedence or resistance coils placed as a shunt
across the poles of the circuit to be protected to normally retain out of action
contact apparatus which when allowed to come into action short circuits the poles
of the circuit and puts them to earth and may at the same time actuate a throw-off
switch to disconnect from the supply mains. The fuse wire may be employed to
hold up a heavy weight, spherical conical or of other suitable shape hanging over two
or more contact pieces so arranged that when the weight falls it shall rest on these
contacts or a spring might be used instead of depending on gravity.
Diagram A shews such an arrangement.
In this diagram A is part of the high pressure supply circuit-B a converter-
C the low pressure circuit say 100 volts-D D and E are three contact blocks, one
block D is in connection with one pole of the low pressure circuit C and the other
block in connection with the other pole-whilst the block E is connected to earth-
Fis a weight held suspended above the space between the three contact blocks by
a fuse wire G-the weight is shewn as being put to earth by being coupled by a
conductor to the block E-H H are resistances one on either side of the fuse
wire and placed as a shunt across the low pressure circuit C-I 1 are lamps on
this circuit.
The action of this device is as follows:-
In the first place should an abnormal rise of pressure take place between the two
poles the current through the resistance and fuse wire, connected across the
secondary, will be abnormally increased, the wire will then break and the suspension
weight will fall on to the contacts connected to both poles of the circuit, thus short-
circuiting them and causing the main converter fuse to go, or actuating a throw off
switch to disconnect from the mains at the same time the weight being now or
already connected to earth puts the whole circuit into good connection therewith.
Should an earth occur on either side of the circuit the pressure between the
centre of the fuse wire and the good pole of the circuit will be increased abnormally,
or in other words an abnormal current will flow from one end of the fuse wire to its
centre this will cause the wire to break and the weight to fall and effect the
protection mentioned above.
Should a connection occur between the primary and secondary and there be an
earth on either side of the primary the fuse wire would again break owing to there

page_text: Demg a greater difference of pressure between the fuse and one or both of the
secondary poles than normal.
Instead of using impedence or resistance coils on each side of the fuse wire, the
fuse wire may as shown in Diagram B be connected to the secondary poles of a
5 small subsidiary transformer the primary of which is fed with current from the
circuit to be protected and put to earth at its centre.
A is part of the high pressure supply circuit-B a converter-C the low pressure
circuit to be protected-D D and E three contact blocks the two blocks D being
connected to the two poles of the circuit and the block E to earth as in Diagram A-
Fis a weight held suspended by a fuse wire which is in circuit with the secondary
coil of a small transformer H the primary of which is fed with current from the
circuit (and put to earth at its centre.
Or two small transformers the primaries of which are in series can as shown in
Diagram Cbe used the secondary of each holding up by a fuse wire a plug or
other contact mechanism. Then on either of these fuse wires going its plug will
short circuit the circuit poles.
By the above described means the waste of energy in the resistances on each
side of a fuse wire is avoided and by suitably winding the small converter or con-
verters the quantity of current passing through the fuse wire or wires can be
multiplied to any extent-thus enabling a rise of pressure which without the
transformer or transformers would not fuse a very extremely small fuse wire to be
so multiplied as to fuse a wire of sufficient strength as
practicable.
to be commercially
In installations or circuits when one pole is put to earth then similar apparatus
could be used but in that case it would only work with a rise of pressure above
normal.
Diagrams B B shew arrangements for effecting this.
one pole of the circuit to be protected should pressure rise above a fixed standard.
In these diagrams C is
His a resistance coupled at one end to this pole and to earth.
In Diagram B'a fuse wire G suppporting the weight F is interposed between the
resistance and earth connection. In B' the primary of a small transformer H is
interposed and the fuse wire G supporting the weight F is placed in the circuit of
the secondary coil.
Instead of the fuse and weight or spring, the passing of current through the
mpedence coils or through a subsidiary transformer may either with or without a
elay be made to actuate contact mechanism in other ways for effecting the above
bjects or may actuate an indicator or sound an alarm to call the notice of
ttendant.
An installation leak detector may be made on similar principles as shown in
Diagram D, and may be described as follows:-The centre of the secondary of the
ransformer feeding the installation circuit or the electric centre of the generating
r transforming apparatus used (by electric centre I mean the point which is at the
ame potential as earth) is put to earth through the primary of a very small subsidiary
ansformer H the secondary of which is connected to two ends of a short piece of
se wire G which supports in the manner described above a heavy metallic
eight For other contact mechanism above two or more contact pieces. Two of
ese D D are respectively connected to the poles of the circuit it is desired to
rotect, and the weight or the third is connected to earth.
cur on one of the poles of the circuit the current will pass through this leak and
Now should a lenk
ck to the centre of the house transformer through the primary of the subsidiary
ansformer II and will generate sufficient current to pass through the secondary
this latter transformer and through the fuse wire G to cause the fuse wire to
eak and let go the weight, which will then short circuit the two poles of the
pressure circuit (and put them to earth, at the same time causing the main
nsformer fuse to go, and cut off the installation from the main supply:
Or in place of the electric centre being put to earth through the primary of a
all converter it may as shewn in Diagram E be put to earth through a fusible

page_text: wire G the fuse wire being arranged to support a weight over 3 contact points,
2 of which D are connected to the 2 poles of the circuit, and the 3rd E to earth;
then on a leak occurring on either pole, the current through the fuse wire will
increase and fuse it the plug falling to short circuit the poles of the installation,
and thereby cause it to be cut out. Other forms of switch may also be used instead
of the weight to effect the same objects.
Instead of having to connect the centre of the transformer directly to earth, the
following modification of apparatus shewn in Dingram F can be used.
Two small subsidiary transformers with their primaries in series connected across
the poles of the circuit and put to earth between the transformers and with their
secondaries in series, but these latter opposing one another, and in series with a
small fuse wire, then on the pressure between the poles of the two primaries being
equal no current can flow through the secondaries, and through the fuse wire in
series with them, but on the least difference in pressure between the two poles of
these two transformers occurring current will flow through their secondaries and on
this arriving at a definite amount the fuse wire will go, causing the plug or switch
to drop and short circuit and put to earth the installation. This arrangement is
obviously a more sensitive form than the single transformer. Another additional
protection can be effected by making the first and last turns of the primary of very
thick wire, and in close contiguity with one another, the middle turns being of thin
wire. Should a sufficient current go through these transformers, and the fuse or
apparatus from some cause refuse to act, then the fine wire of the little transformer
will be burnt up, these thick turns will short circuit one another and put the
installation to earth through no resistance.
In cases where the electric supply is from a station at a distance and where the
current is sent by a conductor which is enclosed by the return and which return is
lightly or less insulated than the inner one or lead and makes good earth at one
end; similar safety mechanism may be used to put the other end to earth in case
the outer insulation is strained above the pressure due to loss on the line by the
inner conductor or a current therefrom going to earth through the apparatus. The
outer or protecting tube which contains the conductors I also use for making an
additional earth to which all the earth connections may also be made.
The difference between ingoing and outgoing currents may also be made to give
indication of any leakage to earth taking place either by telephone if alternate
currents are used or by ringing a bell or actuating other indicator either direct or
through a relay.
For example a telephone may be placed between two coils one on one main and
the other on the other as shewn in Diagram G in which A is a lamp circuit and Ba
telephone placed between coils in the two mains. With equal currents in both, the
telephone would not sound but if a leak took place to earth the telephone would at
once commence to rattle or a coil with fuse or relay or alarm apparatus might be
placed between the two coils instead of the telephone.
Similar means to those herein before described may also be used for ensuring
safety when working with continuous current circuits. For example a needle
indicator may be used as shown at 1 in Diagram H.
To enable an inspector or householder to tell whether the circuits are in good
order a three coil transformer can be used as indicated in Diagram I the two poles
of the house circuit passing through two of them but in inverse directions and the
third being connected to a telephone or other apparatus. On the current going in
and out of the installation being equal there will be no sound in the telephone, but
on their becoming unequal by reason of a fault through one of the leads, more
current will go in at one coil than goes in at the other, therefore current will be
generated in the 3rd coil, which will either sound a telephone, work a relay or
solenoid switch, or the two poles of the circuit may be passed through a differential
coil and on an inspector applying a form of portable suspended needle in the centre
of this coil, he would be able to find out whether the ingoing current is equal to the
outgoing current。

page_text: 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:
1. For the protection of an electric circuit the combination of a fuse wire in
series between two impedence or resistance coils placed across the poles of the
circuit and contact apparatus normally retained out of action by the wire and which
when the wire is fused makes contacts which cause the supply of current to the
circuit to be arrested either by short circuiting the poles of the circuit and putting
them to earth or otherwise or cause a warning to be given of any undue rise of
pressure.
2. The same arrangement with the centre of the fuse wire put to earth to give
protection from any undue rise of pressure between the circuit and earth.
3. For the protection of an electric circuit the employment in combination with
a fuse wire of a transformer for multiplying the quantity of current with which it
is desired to actuate the fuse so that a thicker fuse wire may be used - thus making
a practical fuse which will work with very little current.
4. Where a circuit is fed with alternating current by a converter putting the
centre of the secondary coil to earth either through a fuse which is normally
retaining contact mechanism out of action or through the primary of a small
converter which has the fuse in the circuit of the secondary.
5. For protecting a circuit fed with alternating current placing the primary of a
protecting converter across the poles of the circuit and putting it to earth at the
centre and placing in the circuit of the secondary coil of the converter a fuse which
is normally retaining contact mechanism out of action.
6. For protecting a circuit fed with alternating current the combination of two
small protecting converters with their primaries in series and put to earth between
the converters and with their secondaries in series but opposing one another and in
circuit with a small fuse wire which is normally retaining contact mechanism out
of action.
7. For protecting one pole of a circuit fed with alternating current the com-
bination of a resistance leading from the pole to earth through a fuse which is
normally retaining contact mechanism out of action or through the primary of a
small converter in the circuit of the secondary of which is a fuse normally retaining
contact mechanism out of action.
8. Making the first and last turns of the primary coils of the protecting con-
verters of thick wire and in close contiguity with one another and the middle turns
of thin wire which will fuse when sufficient current goes through and short circuit
the thicker turns.
9. The combination with an electric main in which a conductor is enclosed by
the return and which return is lightly or less insulated than the inner conductor
and makes good earth at one end, of safety mechanism such as herein before
described to put the other end to earth in case the outer insulation becomes unduly
strained.
10. For securing safety when an electric main is used composed of two con-
centric conductors enclosed within an outer protecting tube the employment of
this tube for making an additional earth to which all the earth connections may be
made.
11. For giving indication of any leakage to earth from electric conductors in
any particular house or branch circuit forming part of a network of electric supply
mains the combination of two coils through one of which the ingoing current and
through the other the outgoing current passes and mechanism acted upon by both
coils for giving indication when the action of the current in one coil is not
neutralized by the action of the current in the other coil either by a telephone
placed within both coils or by ringing a bell or actuating other indicator either
direct or through a relay.
12. For giving indication of any leakage to earth from electric conductors in

page_text: any particular house or branch circuit forming part of a network of electric supply
mains the combination of a three coil transformer through two of the coils of
which the two poles of the house or other branch circuit are made to pass but in
inverse directions and the third connected to a telephone or other alarm apparatus
to enable an inspector or householder or other person to tell whether the circuits
are in good order.
Dated this 16th der of December 1901