Apparatus for Indicating Leakages or Escapes of Current from Electric Conductors.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Apparatus for Indicating Leakages or Escapes of Current from
Electric Conductors.
I, Dr. MARTIN KALLMANN, of 41, Linkstrasse, Berlin, W., in the Empire of
Germany, Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
-
The present invention has for its object to provide a control or check, as
direct as possible, on electrical conductors carrying large quantities of current
with respect to any leakages of current, without interrupting the working cur-
rent. The method which is enabled to be carried out by the new apparatus is
based on a measurement of the differences of current strengths flowing through
conductors between various points of said conductors, by the employment of a
differential method and preferably of the nature of the so-called double bridge
arrangement. The method is general for controlling single conductors and it
is immaterial whether said conductors are carried underground or overground or
consist of wholly or slightly insulated wires, cables, &c., or whether it is applied
to entire installations or to the rails serving for the return current lead of electric
railways.
In this apparatus there is a characteristic features namely that it is possible
to control the insulation value of conductors that are traversed by current without
comparing the potential of the earth or the earth current at the fault itself,
and without said measurement being in general interfered with by other faults
that may exist at other places of the installation.
Figures 1 and 2 illustrate the differential system upon which the method is
based, whilst Figure 3, illustrates the practical application of the same to the
case of a single conductor. Figure 4 illustrates its application to the current
return rail of electric railways. Figure 5, its application for controlling the
insulation of an entire house installation on the two wire system: Figure 6,
illustrates the same installation for a three wire system, and Figure 7, illus-
trates its application for controlling at the same time long distance conductors
and installations.
6
Whereas the so-called zero methods" of measurements have hitherto served
only for determining resistance values with equal current strengths in the resist-
ances to be measured, there are employed in the improved apparatus analogous
methods for determining small differences of current strengths in resistances
which are otherwise of equal value or which are in a constant ratio to each other.
In Figure 1, 1-2 illustrates a resistance w which is traversed by a current i¹
of any desired strength, and 3-4 illustrates for example a resistance w of equal
value but which is traversed by a somewhat different current strength 2. Then
if a differential galvanometer gbe connected with one winding 5-6 (with inter-
position of the rheostats h (1-5) and (2-6) to the points 1 and 2, and with
its other winding 7-8 to the points and 4 (also with the interposition of h
(3-8) and (4-7), this galvanometer will indicate the difference of the current
strengths obtaining in the branch resistances 1-2 and 3-4. If then

page_text: this difference of current be produced by a leakage or other fault &c. existing
between the two points of measurement, then the deflection of will correspond
directly to the escape of current that has taken place.
Analogous, but practically more convenient, is the employment of the double
bridge connection for this general case, (Figure 2), in which the galvanometer
which is connected to the points 5 and 6, need only have a single winding (for
example a millivoltmeter or the like). Resistances in the wire connections
as also transitional resistances are eliminated by the interposition of the rheo-
stats (1-5: 2-6: 4-5: 3–6).
•
If g gives no deflection, that proves the equality of ", consequently no
loss or escape of current has taken place along the path from 2-3. In this
case the points 5 and 6 show equal potential. According as is greater or
smaller than 1, a deflection will take place in the galvanoscope to one side or
to the other. Instead of utilising this deflection directly as the measure of the
escape of current or of the insulation fault the zero method may be further em-
ployed by making the deflection equal to zero by varying the ratio of the rheo-
stats hor of the branch resistances w, that is to say by depriving the galvano-
scope g of current and then using the regulation of the resistance thus effected as
the measure of the escape of current which has taken place.
Instead of making the resistances w, as also the rheostats equally great one
to the other, they may be also brought into any desired ratio to one another,
and then for determining the indications of the well known proportional
formula may be employed. In the further description for the sake of simplicity
only the case of equal resistances in the double bridge will be assumed. For
the purpose of obviating too fine adjustment of the galvanometer resistances and
rheostats, the zero adjustment of the galvanometer may also be conveniently regu-
lated by means of regulating resistance before inserting the apparatus in the
working current circuit.
The above described differential system of measurement may be employed
quite generally in almost all cases that occur in electrical working where it is
desired to ascertain earth connections or other escape of current by leakage, or
for the purpose of permanently controlling the insulation, or for discovering
any wandering currents of electrical railways etc. The indications of the galvano-
meter correspond to the amount of the current strengths that have escaped, the
arrangement being such that the measurement (as it is a question of the differ-
ence of two current conditions) is independent of the obtaining working
current conditions, that is to say the load, and since the earth potential does
not come in question in this method, in contradistinction to the otherwise usually
employed methods of determining insulation, this method is not influenced by
any variation of the earth potential or by other earth currents of any other earth
connections.
Figure 3 illustrates a case in which it is desired to observe the insulation of
a single conductor, for example a long distance conductor. At the commence-
ment of the conductor for example at the central station, there is inserted
at 1-2 a small strong-current resistance wc, and a similar resistance we at the end
of the conductor at 3-4. The difference in potential obtaining at the terminal
points 3 and 4 of the latter resistance w can be measured by means of the testing
wires which are carried back to the station. This difference of potential
divided by the resistance we would give the strength of the working current which
flows through w (3-4). The current strength obtaining in (1-2) would be
capable of being observed by means of the measuring wires connected to 9
and 10. The measuring wires leading to 1 and 2 and to 3 and 4 respectively,
are, as explained in Figure 2, connected (with the interposition) of the rheo-
stats ) to the galvanometer g (millivoltmeter or the like) at 9-10, and then the
deflection which takes place at g will correspond to the difference of current
strength in the conductor at 1-2, as compared with 3-4; that is to say, since
no current is taken off along the path 2-3: the deflection will correspond to
the amount of the escape of the current which has taken place by leakages for

page_text: example at faults at 5 and 8. Thus the deflection of the galvanometer indicates
directly the amount of the current leakage through the insulation faults at 5
and 8 independently of any other earth connections in the system, for example at
the point 7.
The determination of the earth currents (so-called wandering currents) escap-
ing from the track rails S of electrical railways (Figure 4) is effected in a similar
manner. In this case a definitely limited length of track line, for example equal
lengths of 1-2 and 3-4 replace the branch resistances w in the former cases.
If represents the working current strength flowing in the rail length 1-2,
and the strength of the working current flowing in the rail portion 3-4,
then will represent the amount of the wandering current which has escaped
along the path 2-3 from the rails into the ground, pipes, &c., and which is
now directly indicated by the galvanometer which is connected by measuring
wires P P to the points 1 and 2 and 3 and 4 respectively: in each case with
interposition of h.
If the critical lengths of track, which show or in which it is thought that there
exist considerable amounts of current losses by escape, be connected in the
manner above described by means of insulated measuring wires permanently
to a differential bridge of the kind described that is provided at a suitable point,
then a permanent control of the earth currents can be obtained during the work-
ing of the railway: the arrangement being such that the difference of potential
between 1 and 2, as also the difference between 3 and 4, will each give (after
having been previously measured or gauged once for all) the strength of the
current flowing in the track rails.
Figure 5 shows the application of the method to a two-conductor installation.
In this case the apparatus would be. advantageously included in the two con-
ductors close to the house connection (3-4). The branch resistances (for
example each of one ohm) may if desired be normally short circuited or bridged
over and are only traversed by current at the instant of measurement so as to
obviate unnecessary permanent losses of potential. The earth currents which
escape at 9 and 10 in consequence of insulation faults or the like produce a
difference between the current flowing in w (5-6) and in w (7-8), so that this
difference of current in the forward and return leads, which is measured by the
galvanometer 9 in the manner above described, corresponds to the insulation
fault of the installation.
Figure 6 illustrates the use of this method for installations on the three wire
system. In this case a resistance wo is included in each of the three poles. To
each of these three resistances, the galvanometer is connected with the
interposition of rheostats at 7 and 10 to the + pole: at 8 and 11 to the O pole
or neutral conductor; at 9 and 12 to the pole. Consequently the galvano-
meter measures the difference between the current difference between the plus and
the minus pole (+) as compared with the current io in the neutral conductor:
that is to say the difference of load of the long distance conductors correspond-
ing to the current escape at 13, 14, and 15. If one of the halves of the system
is without current, then in general there will be obtained the case of Figure 5;
namely of the two wire system with a slight modification.
Finally Figure 7 illustrates a combination of Figure 3 and Figure 5. In
this case (Figure 7) the current loss by leakages at 9, 10, 11, 12 on the long
distance conductors and in the installation at 13 and 14 is shown on the galvano-
meter.
In this case, the four resistances w (which are equal to each other) are included
at 1-2 and 5-6 at the commencement, and at 3-4 and 7-8 at the end of the
line conductors. The current loss in the installation through the faults u and v
is shown by the difference of potential at the points 15-16 (between the rheo-
stats) at the end of the line conductor (beginning of the installation): these
points 15-16 are connected by means of the testing wires P P to the galvano-
meter situated at the station and which galvanometer is also connected to the

page_text: points 17-18 (also between rheostats h) at the commencement of the line con-
ductors. The galvanometer thus measures, when it is only connected to 17-18,
the whole of the current escapes at x, y, z, on the line and at u, v in the installa-
tion. If g is only connected at 15-16 by means of the testing wires P P, then
it measures only the earth connections u, r of the installation. But if g
is con-
nected simultaneously to 17 and 18 and to 15 and 16, it indicates the difference
of the two values, that is to say only the current losses that occur in the line
at x, y, z.
The application of this case to three wire systems would be carried
out in an analogous manner.
In indicating insulation faults of the two poles of an installation of the kind
shown in Figures 5, 6, 7, the simultaneous occurrence of further earth con-
nections in the system constitutes the presumption for the use of the differential
measuring system above described, because the current which escapes for example
from the earth line flows back through the earth into a place of earth connection
of the other pole in the system to the return pole, that is to say without making
use of the return conductor of the installation wires. This presumption of the
presence of other considerable earth connections is generally correct in the case
of networks of conductors: but otherwise, for example for the purpose of mea-
surement one pole should be placed at the entrance of the installation to the
machine, or in the network directly, or for example with interposition of a lamp,
to earth for the purpose of allowing the current leakage of the installation to
use this direct earth path which forms the preliminary condition for the exist-
ence of a difference between the current strength of the forward and return paths,
and consequently for the differential method. When the insulation resistance
of the two poles are equal, the galvanometer at first gives no deflection, and it
is therefore necessary to make a second measurement with a known central
resistance, or by momentarily interrupting one pole, whereby a direct indica-
tion is received in this case also. From the foregoing statements, it will be
seen that the system of differential current measurement indicates directly the
escapes of current by reason of leakages or faults of any kind or position during
the working, independently of the existing load on a conductor in the installa-
tion and without being affected by other earth connections, çarth currents, &c.
and by the use of a contact device on the sufficiently sensitive galvanometer
which is to be used, (millivoltmeter of highest possible resistance) it also indicates
the escapes of current automatically.
:ת
1
1
Ր T
1000
MARKS & CLERK,
18, Southampton Buildings, London, W.C., Agents.
COMPLETE SPECIFICATION.
Apparatus for Indicating Leakages or Escapes of Current from
Electric Conductors.
I, Dr. MARTIN KALLMANN, of 41, Linkstrasse, Berlin, W., in the Empire of
Germany, Electrical 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:-
The present invention has for its object to provide a control or check, as
direct as possible, on electrical conductors carrying large quantities of current
with respect to any leakages of current, without interrupting the working cur-

page_text: rent. The method which is enabled to be carried out by the new apparatus is
based on a measurement of the differences of current strengths flowing through
conductors between various points of said conductors, by the employment of a
differential method and preferably of the nature of the so-called double bridge
arrangement. The method is general for controlling single conductors and it
is immaterial whether said conductors are carried underground or overground or
consist of wholly or slightly insulated wires, cables &c. or whether it is applied
to entire installations or to the rails serving for the return current lead of electric
railways.
In this apparatus there is a characteristic feature viz. that it is possible
to control the insulation value of conductors that are traversed by current without
comparing the potential of the earth or the earth current at the fault itself,
and without said measurement being in general interfered with by other faults
that may exist at other places of the installation.
Certain experiments which have been made before for a similar purpose have
related only to investigations in multiple conductors, but even then they were
not made with the use of a measuring apparatus which would be suitable by
reason of its sensitiveness and simplicity such as is provided by the bridge con-
nection in accordance with the present invention.
In the drawings filed with the Provisional Specification
Figures 1 and 2 illustrate the differential system upon which the method is
based, whilst Figure 3 illustrates the practical application of the same to the
case of a single conductor.
Figure 4 illustrates its application to the current return rail of electric rail-
ways.
Figure 5 its application for controlling the insulation of an entire house in-
stallation on the two wire system.
Figure 6 illustrates the same installation for a three wire system &
Figure 7 illustrates its application for controlling at the same time long dis-
tance conductors and installations.
Whereas the so called zero methods" of measurements have hitherto served
only for determining resistance values with equal current strengths in the resist-
ance to be measured there are employed in the improved apparatus analogous
methods for determining small differences of current strengths in resistances
which are otherwise of equal value or which are in a constant ratio to each other.
In Figure 1, 1-2 illustrates a resistance which is traversed by a current i¹
of any desired strength, and 3-4 illustrates for example a resistance of equal
value but which is traversed by a somewhat different current strength. Then
if a differential galvanometer be connected with one winding 5-6 (with inter-
position of the rheostats (1-5) and 2-6) to the points 1 and 2. and with
its other winding 7-8 to the points 3 and 4 (also with the interposition of h
(3—8) and (4—7), this galvanometer will indicate the difference of the current
strengths obtaining in the branch resistances 1-2 and 3-4. If then
this difference of current be produced by a leakage or other fault &c. existing
between the two points of measurement, then the deflection of will correspond
directly to the escape of current that has taken place.
Analogous, but practically more convenient, is the employment of the double
bridge connection for this general case, (Figure 2). in which the galvanometer g
which is connected to the joints 5 and 6, need only have a single winding (for
example a millivoltmeter or the like). Resistances in the wire connections,
as also transitional resistances are eliminated by the interposition of the rheo-
stats (1-5 2-6: 4-5: 3–6).
If gives no deflection, that proves the equality of -, consequently no
loss or escape of current has taken place along the path from 23. In this
case the points 5 & 6 show equal potential. According as is greater or
smaller than ", a deflection will take place in the galvanoscope to one side or
to the other. Instead of utilising this deflection directly as the measure of the

page_text: escape of current or of the insulation fault the zero method may be further em-
ployed by making the deflection equal to zero by varying the ratio of the rheo-
stats or of the branch resistances w, that is to say by depriving the galvano-
scope g of current and then using the regulation of the resistance thus effected as
the measure of the escape of current which has taken place.
For
Instead of making the resistance. , as also the rheostats equally great one
to the other, they may be alse brought into any desired ratio to one another,
and then for determining the indications of the well known proportional
formula may be employed. In the further description for the sake of simplicity
only the case of equal resistances in the double bridge will be assumed.
the purpose of obviating too fine adjustment of the galvanometer resistances and
rheostats the zero adjustment of the galvanometer may also be conveniently regu-
lated by means of regulating resistance before inserting the apparatus in the
working current circuit.
The above described differential system of measurement may be employed
quite generally in almost all cases that occur in electrical working where it is
desired to ascertain earth connections or other escape of current by leakage, or
for the purpose of permanently controlling the insulation, or for discovering
any wandering currents of electrical railways etc. The indications of the galvano-
meter correspond to the amount of the current strengths that have escaped, the
arrangement being such that the measurement (as it is a question of the differ-
ence of two current conditions) is independent of the obtaining working
current conditions, that is to say the load, and since the earth potential does
not come in question in this method, in contradistinction to the otherwise usually
employed methods of determining insulation, this method is not influenced by
any variation of the earth potential or by other earth currents or any other earth
connections.
Figure 3 illustrates a case in which it is desired to observe the insulation of
a single conductor, for example a long distance conductor. At the commence-
ment of the conductor for example at the central station, there is inserted
at 1-2 a small strong current resistance and a similar resistance w at the end
of the conductor at 3-1. The difference in potential obtaining at the terminal
points 3 and 4 of the latter resistance can be measured by means of the testing
wires which are carried back to the station. This difference of potential
divided by the resistance w would give the strength of the working current which
flows through w (3-4). The current strength obtaining in w (1-2) would be
capable of being observed by means of the measuring wires connected to 9
and 10. The measuring wires leading to 1 and 2 and to 3 and 4 respectively,
are, as explained in Figure 2, connected (with the interposition) of the rheo-
stats to the galvanometer g (millivoltmeter or the like) at 9-10, and then the
deflection which takes place at g will correspond to the difference of current
strength in the conductor at 1-2, as compared with 3-4: that is to say, since
no current is taken off along the path 2-3: the deflection will correspond to
the amount of the escape of the current which has taken place by leakages for
example at faults at 5 and 8. Thus the deflection of the galvanometer indicates
directly the amount of the current leakage through the insulation faults at 5
and 8 independently of any other earth connections in the system, for example at
the point 7.
The determination of the earth currents (so called wandering currents) escap-
ing from the track rails S of electrical railways (Figure 4) is effected in a similar
manner. In this case a definitely limited length of track line for example equal
lengths of 1-2 and 3-4 replace the branch resistances to in the former cases.
If
represents the working current strength flowing in the rail length 1-2
and the strength of the working current flowing in the rail portion 3-4.
then will represent the amount of the wandering current which has escaped
along the path 2-3 from the rails into the ground, pipes, &c., and which is

page_text: now directly indicated by the galvanometer 9 which is connected by measuring
wires P P to the points 1 and 2 and 3 and 4 respectively; in each case with
interposition of h.
If the critical lengths of track, which show or in which it is thought that there
exist considerable amounts of current losses by escape, be connected in the
manner above described by means of insulated measuring wires permanently
to a differential bridge of the kind described that is provided at a suitable point,
then a permanent control of the earth currents can be obtained during the work-
ing of the railway; the arrangement being such that the difference of potential
between 1 and 2, as also the difference between 3 and 4, will each give (after
having been previously measured or gauged once for all) the strength of the
current flowing in the track rails.
Figure 5 shows the application of the method to a two-conductor installation.
In this case the apparatus would be advantageously included in the two con-
ductors close to the house connection (3-4). The branch resistances w (for
example each of one ohm) may if desired be normally short circuited or bridged
over and are only traversed by current at the instant of measurement so as to
obviate unnecessary permanent losses of potential. The earth currents which
escape at 9 and 10 in consequence of insulation faults or the like produce a
difference between the current flowing in w (5-6) and in w (7-8), so that this
difference of current in the forward and return leads, which is measured by the
galvanometer 9 in the manner above described, corresponds to the insulation
fault of the installation.
-
Figure 6 illustrates the use of this method for installations on the three wire
system. In this case a resistance w is included in each of the three poles. To
each of these three resistances w, the galvanometer y is connected with the
interposition of rheostats at 7 and 10 to the + pole: at 8 and 11 to the O' pole
or central conductor: at 9 and 12 to the pole. Consequently the galvano-
meter measures the difference between the current difference between the plus and
the minus pole (ii) as compared with the current io in the neutral conductor;
that is to say the difference of load of the long distance conductors correspond-
ing to the current escape at 13, 14, and 15. If one of the halves of the system
is without current, then in general there will be obtained the case of Figure 5:
namely of the two wire system with a slight modification.
Finally Figure 7 illustrates a combination of Figure 3 and Figure 5. In
this case (Figure 7) the current loss by leakages at 9, 10, 11, 12 on the long
distance conductors and in the installation at 13 and 14 is shown on the galvano-
meter.
In this case the four resistances w (which are equal to each other) are include l
at 1-2 and 5-6 at the commencement, and at 3-4 and 7-8 at the end of the
line conductors. The current loss in the installation through the faults u and v
is shown by the difference of potential at the points 15-16 (between the rheo-
stats h) at the end of the line conductor (beginning of the installation): these
points 15-16 are connected by means of the testing wires P P to the galvano-
meter 9 situated at the station and which galvanometer is also connected to the
points 17-18 (also between rheostats h) at the commencement of the line con-
ductors. The galvanometer thus measures, when it is only connected to 17-18,
the whole of the current escapes at x y z on the line and at u, in the installa-
tion. If is only connected at 15-16 by means of the testing wires P P, then
it measures only the earth connections, of the installation. But if g is con-
nected simultaneously to 17 and 18 and to 15 and 16, it indicates the difference
of the two values, that is to say only the current losses that occur in the line
at x, y, z.
The applications of this case to three wire systems would be carried
out in an analogous manner.
In indicating insulation faults of the two poles of an insulation of the kind
shown in Figures 5, 6, 7, the simultaneous occurrence of further earth con-

page_text: nections in the system constitutes the presumption for the use of the differential
measuring system above described, because the current which escapes for example
from the earth line flows back through the earth into a place of earth connection
of the other pole in the system to the return pole, that is to say without making
use of the return conductor of the installation wires. This presumption of the
presence of other considerable earth connections is generally correct in the case
of networks of conductors: but otherwise, for example for the purpose of mea-
surement one pole should be placed at the entrance of the installation to the
machine, or in the network directly, or for example with interposition of a lamp,
to earth for the purpose of allowing the current leakage of the installation to
use this direct earth path which forms the preliminary condition for the exist-
ence of a difference between the current strength of the forward and return paths,
and consequently for the differential method. When the insulation resistance
of the two poles are equal, the galvanometer at first gives no deflection, and it
is therefore necessary to make a second measurement with a known central
resistance, or by momentarily interrupting one pole, whereby a direct indica-
tion is received in this case also. From the foregoing statements, it will be
seen that the system of differential current measurement indicates directly the
escapes of current by reason of leakages or faults of any kind or position during
the working, independently of the existing load on a conductor in the installa-
tion and without being affected by other earth connections, earth currents, &c.
and by the use of a contact device on the sufficiently sensitive galvanometer
which is to be used, (millivoltmeter of highest possible resistance) it also indicates
the escape of current automatically.
.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed I declare that what
I claim is:-
1. An arangement for indicating the leakage of electricity substantially as
hereinbefore described.
2. An arrangement for indicating the leakage of electricity due to defective
insulation or the like in a single electrical conductor, whereby the difference of
current strengths at points before and after the fault, corresponding to the amount
of leakage is shown on a galvanometer suitably introduced into the circuit, a
resistance being inserted at the commencement and end of the conductor or the
resistances being replaced by rail portions, testing wines leading thence to the
galvanometer, substantially as herein before set forth and illustrated with refer-
ence to Figs. 3 and 4.
3. An arrangement for indicating the leakage of electricity due to defective
insulation or the like in an installation on the two wire system, whereby the
difference of current strengths at points before and after the fault, corresponding
to the amount of leakage, is shown on a galvanometer in the measure of a double
bridge arrangement introduced into the circuit, the branch resistances being in-
serted in the two conductors, substantially as herein before set forth and illustrated
with reference to Fig. 5.
4. An arrangement for indicating the leakage of electricity to defective insula-
tion or the like in an installation on the three wire system, whereby the differ-
ence of current strengths at points before and after the fault, corresponding to
the amount of leakage, is shown on a galvanometer in the measure of a double
bridge arrangement introduced into the circuit, a resistance being inserted in
each of three poles which are all connected up with a galvanometer by the inter-
position of rheostats, substantially as hereinbefore set forth and illustrated with
reference to Figure 6.
5. An arrangement for indicating the leakage of electricity due to defective
insulation or the like in electrical conductors or installations, whereby the
difference of current strengths at points before and after the fault, corresponding
to the amount of leakage is shown on a galvanometer in the measure of a double

page_text: bridge arrangement introduced into the circuit, a combination of four equal
resistances being inserted at the commencement and end of the line conductors,
substantially as hereinbefore set forth and illustrated with reference to Figure 7.
Dated this day of February 1800
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and 25, Cross Street, Manchester,
Agents.