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Патент USA US2403414

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July 2, 1946.
o. c. TRAVER
2,403,414
PROTECTIVE SYSTEM
Filed Jan. 27, 1944
Inventor:
' O I iver C. Tr'aver,
l'b H WW
6:2
HIS Attorney.
Patented July 2, 1945
UNl'l‘ED STATES PATENT DFFICE
2,403,414:
PROTECTIVE SYSTEM
Oliver 6. Travel‘, Drexel Hill, Pa, assignor to
General Electric Company, a corporation of
New York
I
Application January 2'7, 19%, Serial No. 519,928
31 Claims. (Cl. 175-—294)
My invention relates to protective systems for
electric circuits and more particularly to protec~
tive systems employing a relay of the distance
type for protecting against ground faults.
There has existed for a long time the demand
for ground fault distance relays which will give
substantially the same distance response on all
faults involving but a single conductor. In order
to get satisfactory operation a single ground dis~
2
ing in which Fig. 1 is a schematic diagram of a
protective system embodying my invention, Figs.
2 and 3 are curve diagrams to aid one in under—
standing my invention, Fig. 4 is a schematic dia
gram of a protective system embodying a modi
fication of my invention, and Fig. 5 is a vector
diagram to aid one in understanding my inven
tion.
Referring now tov Fig. 1 of the drawing, I have
tance relay has been provided with sWitCJlllg 10 illustrated
a ground fault protective system of
means responsive to the occurrence of a ground
the distance type for a polyphase circuit is in
which overvoltage alone is used to control an
ergization
fault on the
of system
the distance
for affording
relay. Usually
the proper
distance
electroresponsive device which operates in a time
relays are energized in response to both a cur~
proportional to the distance of the electrore
rent and a voltage quantity so as to give an im~
15 sponsive device from the ground fault. The elec
pedance or so-called distance response, and the
troresponsive device is assumed to be at the point
satisfactory prior art devices having only a single in
the circuit Where the voltage quantity used
relay required both a switching of the current
for energization purposes is obtained. Protected
and potential quantities for the same distance
response on all the ground faults involving but 20 polyphase circuit I9 is illustrated as a three
phase circuit comprising phase conductors lElA,
a single conductor which might occur on the
I03, and I to, respectively, and connected to an
polyphase circuit being protected. Such an ar~
associated electric circuit H by means of a suit
rangement is disclosed and claimed in a cop-end
able circuit interrupting means l2. Associated
ing application of Albert R. Van C. Warrington,
Serial No. 423,681, ?led December 19, 1941, and 25 circuit ll is illustrated as comprising phase con~
assigned to the same assignee
plication.
the present ap
It is an object of my invention to provide a
ductors “A, He, and Ho respectively. Circuit
interrupting means 12 has been speci?cally ‘illus
trated as a latched closed circuit breaker hav
ing a trip coil l3 and an “a” switch M, which
new and improved ground fault distance relay
which is simple and compact, and which oper» 30 is closed when the circuit breaker is closed and
open when the circuit breaker is open. The sys
ates satisfactorily on ground faults.
tem comprising circuits l0 and Il should be
Still another object of my invention is to pro—
grounded through any suitable grounding means
vide a new and improved protective system in
which overvoltage alone is used to cause opera
tion of an electroresponsive device in a time pro‘
portional to the distance from the electrorespona
sive device to the fault.
which is illustrated in Fig. l as a Y connected
generator l5 having the neutral it thereof
grounded through an impedance l'l.
On electric systems upon which a ground fault
exists there is, of course, also present a zero se
A further object of my invention is to pro~
quence voltage. It is a well known fact that
vide a ground fault distance relay which oper»
ates in response to the first power of a voltage 40 with a uniform impedance per unit of distance
this zero sequence voltage is a maximum at the
quantity of the circuit.
fault and decreases in a substantially linear man
Another object of my invention is to provide
ner from the fault to the generating source.
a new and improved ground fault distance relay
Within the source, distance loses its meaning.
in which operation thereof is obtained in re’
sponse to the Zero sequence voltage of the circuit ‘
modi?ed by the area of a voltage triangle of said
circuit.
Further objects and advantages of my inven“
My invention is particularly concerned with
an arrangement in which an overvoltage or, in
other words, an increase in the zero sequence
voltage above a predetermined value, as for ex
ample in protected circuit I8, is used to indicate
scription proceeds and the features of novelty 50 the distance to, the ground. fault and consequent
which characterize my invention will be pointed
ly to cause operation of circuit interrupting means
out with particularity in the claims annexed to
52 on a single line to ground fault, that is, a
and forming a part of this speci?cation.
ground fault involving only a single conductor
For a better understanding of my invention,
in a time proportional to the distance of the
reference may be had to the accompanying draw
fault from circuit interrupting means 12 which
tion will become apparent as the following de
2,403,414
3
4
tity proportional to the voltage existing on cir
cuit 10 adjacent the electroresponsive device, I
ergization of the trip coil 13. It should be under
stood that circuit controlling inembc' 23 which is
schematically illustrated may be an electronic
device or maybe operated by means of a suitable
electronic relay if desired. If circuit controlling
member
is controlled by a mechanical relay, it
provide a transformer [8 including a Y con
would
to be very
preferably
sensitive
be of
and
thesopolarized
as to prevent
type soany
is assumed to be substantially at the same place
as the electroresponsive device controlling the
same, to be described hereinafter.
In order to obtain a zero phase sequence quan»
nected primary winding l9 having a grounded
possibility of holding up on a reverse current in
neutral 20 and a broken delta secondary wind
Electroresponsive t'cvico
also in
ing 2| including a pair of terminals 22. Pri 10 winding
mary winding I9 may be suitably connected to
cludes
and 31 awhich
variable
are resistor
connected
55 having
across terminals
terminals 22
the end of circuit l0 adjacent circuit interrupt»
broken
elta
secondary
winding
2! of poten"
ing means I2 or as illustrated, to circuit ll adja“
tial trans
may it through a s iitablo full wave
cent to circuit II], the voltage of which would be
W ding 3'1,
15 recti?er generally indicated at t.»“
substantially the same.
the
energization
of
which
controls
circuit
or con—
In order to be sure that the ground fault dis
tact controlling member
is connected across a
tance electroresponsive device to be described
source of direct current potential in series with
hereinafter operates only for faults occurring on
variable resistor
and the normally closed con“
protected circuit I0, I provide a directional relay
23 including a pair of windings 24 and 25 respec 20 tacts 21 of directional relay or starting unit 23.
rJonsequently, as long as contact controlling momtively. Directional relay 23 includes a contact
her 235 of directional relay 23 bridges contacts 21,
controlling element 26 which is adapted to con
winding St is energized and contacts 32 are open
trol normally closed contacts 21 and normally
The variable resistor 35
do indicated in Fig. l.
open contacts 28. A suitable spring 29 is provided
adjustable to determine the portion of the
to bias contact controlling member 26 into on
zero sequence potential which is to appear across
gagement with contacts 21. Winding 25 of relay
terminals 36 and El, the purpose of which will
23 is connected across terminals 22 of broken
become apparent from the following description.
delta secondary winding 2| of potential trans
Electroresponsivo device 3! lurther includes a
former l8 so as to be energized in response to the
capacitor 39 connected across the source of direct
zero phase sequence voltage existing 0n the ad
current potential in parallel with serially con
jacent end of protected circuit I0.
nected resistor 35 and winding
In addition.
Winding 24 on the other hand, in order to give
I also provide an adjustable discharge resistor
electroresponsive device 23 a directional char
49 connected across capacitor ?ll. Capacitor 33,
acteristic, is energized in response to the zero
as will become apparent from the following cle
sequence current flowingr in protected circuit Ill.
scription, provides the timing means by which
To this end each of the phase conductors Ill/i,
electroresponsive device ill is caused to operate
Ills, and lllc are provided with a current trans
in a time dependent upon the distance ol‘ the
former designated respectively as 3%, BBB, and
clcctroresponsive device ‘from the fault.
300. The secondary windings of each of these
Under normal. conditions, as indicated in Fig.
transformers 30A, 30B, and 30c are connected in 40
1, the capacitor 33 is charged to the potential of
parallel with each other and to winding 24 of
the direct current source since it is connected
directional relay or starting unit 23 so that wind
across this source of direct cur'ent potential as
ing 26 is energized with a zero sequence current
indicated through the contacts 21 of directional
quantity. As long as no ground fault exists on
relay 23. In the event of a ground fault occur
protected circuit In, no zero sequence current will
ring on protected circuit Ill zero sequence quan
?ow in winding 24 to cause contact controlling
tities will exist to cause the operation of direc
member 26 to move away from contacts 21.
tional relay 23 to open contacts 21. Immediately
Whenever a line to ground fault occurs on the
vhereafter, capacitor 39 will begin to discharge
system other than on circuit Hi, any zero sequence
‘hrough resistor
the potential across this
current ?owing in winding 24 will, in coopera~
capacitor and resistor tends to m intain the cur
tion with the zero sequence voltage existing in
rent flowing through winding 34 and consequently
winding 25, cause a torque on contact controlling
tends to maintain contacts
in the c; - condi
member 26 to aid spring 29 in holding contact
tion, The voltage across capacitor 39 with respect
controlling member 26 against contact 21‘. Only
to time starting with 231‘0 time at the instant
when a ground fault occurs on circuit Ill will the
contacts 2 are opened is represented by the
zero sequence current in winding 24 cause the
curve of Fig. 2. It will be observed that from
power directional relay, or starting unit 23, to be
sero~tirne to. time equals ‘t1 that the capacitor
energized so as to open contacts 21 and close
discharge curve is substantially linear. It will
contacts 28.
The electroresponsive device of my invention 60 be understood that if circuit controlling member
33 is controlled by electronic means substantially
which is adapted to respond solely in dependence
all the discharge current will ?ow through re
upon an overvoltage, and speci?cally in depend
sistor M, which may be adjusted to produce the
ence upon the increase in zero sequence voltage,
desired shape of the curve of Fig.
However,
upon the occurrence, of a ground fault in a time
under certain conditions the resistor llil may be
proportional to the distance of the fault (as
dispensed with and the discharge of capacitor
measured by impedance) from the electrore
39 controlled by resistor 35» at somewhat reduced
sponsive device is generally indicated at 3! . This
degree of accuracy.
electroresponsive device includes a pair of con
The recti?ed zero phase sequence voltage ap
tacts 32 which are connected in series with the
contacts 28 and in series with the trip coil l3 70 pearing across terminals 35 and 31 of resistor 35
is in opposition to the potential across resistor
across a suitable source of direct current poten
40. That is, the difference in these two potentials
tial. A circuit controlling member 33 which is
appears across relay winding 34. From Fig. 3
illustrated as being controlled in response to the
which assumes a uniform impedance per unit of
energization of a winding 34 is adapted to con
distance, it will be obvious that for points between
trol the contacts 32 and consequently the en—
"a
2,403,414:
5
the electroresponsive devices and the fault, the,
nearer the ground fault is to electroresponsive de
vice 3|‘ the higher the zero phase sequence volt
age across resistor 35 will be. If the fault is on
6
Fig. 1 will be obvious to those skilled in the art
and no further discussion will be included.
As has been suggested above, substantial
changesin the system setup will affect the oper
ation of electroresponsive device 3!. I have dis
protected circuit ii]v so that directional relay 23
opens its contacts 21, capacitor 39 will begin to
covered, however, that for many systems, particu
discharge in accordance with the curve of Fig. 2.
larly those which are preponderantly inductive
When the voltage across resistor 4i‘? substantially
such as those in which the system neutral is
equals the opposing zero sequence voltage across
solidly grounded or where the current is limited
resistor 35, winding 34 is deenergized so as to 10
by inductive reactance, that at the point of fault
permit contact controlling member 33 to close
the ratio of the area de?ned by the three line
contacts 32 and cause the operation of circuit
to line voltages of the three phase system divided
interrupting means l2. Since the ?rst part of the
by the zero phase sequence voltage (hereafter ex~
drop in voltage of capacitor 39 is substantially
pressed as EA/EO) is approximately equal to a
linear as is illustrated in Fig. 2 and the zero se
constant regardless of the system setup or the
quence voltage across resistor 35 is linear with
changes made thereon. The above ratio is, for
respect, to distance from the fault as indicated in
practical purposes, constant regardless. of the
Fig. 3, the operating or null point in the potential
location of the fault and whether it is near the
across relay Winding 34 will be reached and con~
generating source or remote therefrom. At any
tacts 32 will be closed when a single line to ground 20 other point on the circuit between the fault and
fault occurs on protected circuit H3 in a time pro
the source, the residual voltage which is three
portional to the distance of the fault from electro
times the zero phase sequence voltage decreases
responsive device 3!. On account of the internal
with the line drop between the point in question
impedance of recti?er 3B, the drop across re“
and the point of the fault as was pointed out
sister 35 will vary with its ohmic value. For this 25 above.
and other reasons, resistor 35 will be adjusted so
In Fig. 4 I have disclosed a protective system
that for faults occurring on circuit Hi imme
in which I have provided a ground fault distance
diately adjacent electroresponsive device 3i, op~
relay ‘whose principle of operation is based upon
eration of electroresponsive device 3! will occur
the ratio of EA/EO at the fault being equal to a
without any delay. In other words, the recti?ed
constant for a predominantly inductive system
zero phase sequence voltage across resistor 35 for
grounded solidly or through reactance. The cor
these conditions should be equal to the initial
responding
parts of Fig. 4 have been designated
charge on capacitor 39.
by the same reference numerals as in Fig. 1.
It will be observed that elect-roresponsive device
Referring now to Fig. 4 I have illustrated an
35 operates substantially in response to the ?rst
electroresponsive device 4| having inherent direc
power of the zero sequence voltage since contacts
tional characteristics as will be described herein
32 are closed when the zero sequence voltage
after which is adapted to control contacts 42 con
across resistor
approximately equals the volt~
nected in series with trip coil iii of circuit breaker
age across resistor 45!. In other words, operation
l2. Electroresponsive device 4!, which operates
of electroresponsive device 3! occurs at a null
in response to the ?rst power of the zero phase
point which is dependent solely on substantially
sequence voltage and is restrained from opera
tion in response to the area of the voltage tri
the ?rst power of the zero phase sequence voltage
of the protected circuit.
It should be understod that other distance re
lays farther out on protected circuit
.3; cp
erate to isolate the fault prior to the onset-ion
angle referred to above and represented by the
expression EA, is similar in construction to the
electroresponsive device disclosed and claimed in
United States Reissue Patent 21,813, Verrall,
granted May 2'7, 1941, and assigned to the same
of electroresponsive device 35, in which case the
zero phase sequence voltage will return to normal
and the directional relay
will returnto its orig
inal position so that the apparatus will be re
stored to the condition illustrated in Fig. 1 where»
by tripping of circuit interrupting means 12 will
not occur. It will be understood that additional
means will be provided if necessary to protect
circuit iii against faults involving more than one
phase conductor. Since the zero phase sequence
voltage at terminals 22 of potential transformer
i8 is usually lower on a ground fault involving
50
assignee as the present application. As illustrated
in Fig. 4 this electroresponsive device ti includes
a hollow magnetic stator 43 having a plurality of
inwardly projecting salients 4:3 to 55 inclusive.
The salients 49 and 5% have a relatively small
cross section for a purpose which will become ap~
parent as the following description proceeds.
Each of these salients is provided with a wind»
ing designated by the corresponding reference
numeral marked with a prime. Stator 43 also in
cludes a central magnetic member 52 concentri
cally positioned with respect to the ends of the
more than one conductor, operation on double
line to ground faults though in correct sequence 60 salients 44 to 5| inclusive so as to form an air
gap between the ends of the salients and the
would be materially delayed and additional pro
central magnetic member 52. A suitable cup
tective apparatus should be provided for any such
faults.
shaped rotor 53 is adapted to rotate in this area
and is connected to a contact controlling element
It will be observed that with the arrangement
54 for bridging contacts 42 connected in the
described above a distance relay is provided which
trip circuit of circuit breaker l2. A relatively
operates in a time proportional to the distance
weak spring 55 may be provided to bias contact
between the relay and the fault and which is de—
controlling member 54 away from contacts 62.
pendent solely upon an overvoltage to give a re~
The windows 435’, 49’, 50’ and 5:’ energize
spouse in a time proportional to the distance
the corresponding salients so as to produce fluxes
from the fault, and preferably dependent solely
which interact to produce an operating torque
upon the ?rst power of the magnitude of the
tending to close contacts 42. As has been pointed
Zero phase sequence voltage.
out above, it is desired for this operating torque
In view of the detailed description included
to be substantially proportional to the ?rst power
above, the operation of the protective system of 7 of the zero phase sequence voltage E0. To this
2,403,414
8
to produce a torque proportional to the area of
end the windings 49' and 50’ which are polarizing
the
triangle ABN of Fig. 5, while the energiza
windings similar to the winding 24 of directional
tion of windings 45' and 46’ tends to produce a
relay 23 are energized with the zero phase se
torque proportional to the area BCN in Fig. 5,
quence current ?owing as the output of the par
and the energization of windings 48’ and 41’ tends
allel connected secondary windings of current
to produce a torque proportional to the area CAN
transformers 36A, 30B, and 300 respectively. The
of Fig. 5. Since these torques are all in the same
windings 48' and 5|’, on the other hand, are
direction with respect to contact controlling ele
energized with the zero phase sequence voltage
ment
54 and rotor 53, a total restraining torque
appearing across the terminals 22 of potential
transformer l8 through a variable resistance 55, 10 proportional to the sum of the areas of these
three triangles, or in other words, proportional to
normally open contacts 51 of a starting unit, nor
the area of triangle ABC of Fig. 5 represented as
mally open contacts 13, capacitor 53, and the
EA is obtained. It will be observed that the torque
adjustable winding 59 of a combined transformer
and reactor 60 well known in the art as a trans
actor, all of which will be described in greater
detail hereinafter. The interaction of the ?uxes
produced by the windings 48’ to 5|’ inclusive
produce a torque proportional to the zero phase
produced by virtue of the energization of windings
44’ and 5i’ is neutralized by the equal and oppo
site torque produced by the energization of wind
ings 4.1’ and 48'.
Since, as was pointed out above, the ratio of
sequence voltage and since salients 49 and 59 are
the area of the voltage triangle EA to the zero
connected windings so that variation of the re
sistance 56 will produce a linear change insofar as
the energization of windings 4B’ and 5]’ is con
as near the far end of the line.
and any needed correction can be made.
as if both quantities were compensated for the
considerably restricted in size, saturation occurs 20 phase sequence voltage E0 is substantially con
stant at the fault regardless of any system
so that a substantially constant flux is produced
changes which might occur, this ratio can be
thereby causing the operating torque to be sub
re?ected back to the relay by compensating for
stantially proportional to the ?rst power of the
the line drop due to the residual current, there
zero phase sequence voltage over that range with
which we are concerned. The capacitor 58 is 25 by reflecting this constant ratio back to the re
lay, when the fault is at a limiting position such
provided to neutralize the inductance of the series
Although not
illustrated in Fig. 4, it should be understood that
any suitable line drop compensation for the sev
cerned. Ordinarily the reactance of adjustable 30 eral phase currents may also be used to secure
compensation for EA. I have discovered, how
winding 59 is small in comparison with the re
ever, that for some systems, by using an in
actance of the rest of this series circuit so that
creased amount of compensation for the E0
changes in its adjustment will not materially
quantity and no compensation for the EA quan
change the total. If, however, in any case this is
not true, the capacitor 58 can be made variable 35 tity, approximately the same results are obtained
Other
line drop between the relay and the fault. In
Fig. 4 therefore, I have merely compensated for
the line drop insofar as it eifects the zero phase
D’Arsonval element having a permanent magnet
40 sequence voltage, and this is accomplished by
?eld.
means of securing a ?rst power voltage torque
would include its recti?cation and use in a
In order to obtain a restraining torque sub
stantially proportional to the area of the tri
angle formed by the line to line voltages of the
protected circuit still utilizing potential trans
former IS, the windings 44' to 41' have been ener
means of the transactor 60 having a primary
winding 6| connected so as to be energized with
the output of the current transformers 30A, 30B,
and 300 respectively which have their secondary
45 windings connected in parallel. The output of
the secondary winding 53 which is a compensa
tion voltage proportional to the zero phase se
quence line drop when transactor 6D is properly
adjusted, is superimposed on the zero phase se
quence voltage obtained across the terminals 22
of potential transformer [8. Since protected cir
sented by the vector Ema. Similarly, the voltage
cuit I0 is assumed to be predominantly inductive
between phase conductors His and Hie is repre~
in character, it is only necessary to compensate
sented by the vector EEG and the voltage between
for the inductive drop and consequently adjust
phase conductors llic and IDA is represented by
the vector EGA- The normal line to ground volt 55 able winding 59 is adjusted to introduce a voltage
component proportional to the zero phase se
ages of Fig. 5‘ are represented by vectors EAN,
quence voltage drop between the relay and the
Fun and Eon respectively. Since potential trans
maximum distance at which a fault may occur
former l8 does not permit one to readily obtain
on the line and for which tripping of circuit
line to line voltage quantities therefrom, but does
permit one to readily obtain line to ground quan 60 breaker I 2 is response to operation of electro
responsivc device 4! is desired. It should be
tities therefrom, it will be obvious from Fig. 5
understood that winding 59 will be adjusted to
that the area EA of the voltage triangle ABC
add three or more times the line drop of the re
may readily be obtained by a summation of the
sidual voltage if compensation for the area of
areas of the three triangles of Fig. 5 designated
the voltage triangle is not to be used.
as ABN, BCN, and CAN. It should be observed
In order to obtain a time proportional to dis
that although transformer I8 is illustrated as be~
tance quantity, or response, ‘in the same manner
ing connected to circuit II, it is connected to
as in Fig. 1, I have provided a timing unit gen
circuit ll closely adjacent to circuit ill so that
erally indicated at 62, which comprises a. motor
for all practical purposes, the voltages obtained
element 63 connected in series with the polariz~
from potential transformer l8 are the voltages
ing windings 49’ and 58’ of electroresponsive de
existing on the near end of protected circuit In.
vice M. Whenever a ground fault occurs, there
Accordingly, I have illustrated the windings M’,
fore, the zero sequence current flowing in wind
45’, 46’ and 41' energized respectively with the
ing of the motor element 53, will cause the motor
voltages Em, EBN, Eon and EAN respectively. With
element to operate and wind up spring 64. The
this arrangement, the windings 44' and 45' tend
gized with particular line to ground potentials.
From Fig. 5 it will be obvious that the line to line
potentials of protected circuit l0 form the tri
angle ABC, the area of which is EA. The voltage
between phase conductors IOA and I013 is repre 50
2,403,414.
9
energy stored in spring G41 will be dissipated
trated a simple voltage relay 12 which is ener
through a timing element 65 so as to cause a cir
gized across the open terminals of broken delta
winding 2| of transformer 18 and whose contacts
l3 control the energization of windnigs 48’ and
5|’ of electroresponsive device ?ll. On a system
cuit controlling element 66 to move with uni
form speed to successively engage contacts ill, 68,
69, and ‘i8, thereby varying the resistance 53
and consequently changing the reach of distance
electroresponsive device Iii. As the resistance
56 is progressively cut out of the circuit, a given
residual voltage across terminals 22 of trans
having a su?icie-nt amount of reactance in cur
rent limiting reactor I'l, this relay 72 would be
picked up on a single line to ground but not on
a double line to ground fault.
former is will cause a progressively increasing
The operation of the protective system of Fig. 4
operating torque to be applied to rotor 53 so that
will be obvious to those skilled in the art in View
operation in a time dependent upon the distance
of the detailed description included above. It
will be observed that I have provided a ground
Motor element 63, when deenergized, is reset
fault distance relay which operates in a time
by spring 75 and, when energized, also moves a 15 dependent upon the distance of the electro
contact controlling element ‘it so as to engage
responsive device from the fault, which practi
contacts 5'! and thereby act as a starting unit in
cally is not affected by system changes when
some respects similar to directional relay 2% of
applied to a predominantly reactive system and
Fig. 1. No single conductor to ground fault can
which is sturdy in construction and also is
effect operation of electroresponsive device 4| 20 simple and economical both to manufacture and
until a zero phase sequence current exists in pro
to install.
While I have shown and described several
tected
and close
circuit
contacts
iii to57.energize
Contacts
motor
51 are
element
not es
embodiments of my invention, it will be obvious
sential. ri‘hey are useful though to conserve the
to those skilled in the art that various changes
energy to be taken from the potential trans
and modi?cations may be made without de
former l8 which, being connected to the bus, can
parting from my invention, and I, therefore, aim
thereby be the source of supply to a. large num
in the appended claims to cover all such changes
ber of ohm units 4i protecting the same number
and modi?cations vas fall within the true spirit
of circuits such as it. Since only those units
and scope of my invention.
between the fault and the relay will be obtained.
having the requisite amount of residual current
What 1' claim as new and desire to secure by
in coil 63 will close their contacts 5‘! to use the
Letters Patent of the United States is:
potential from terminals 22, the potential trans~
formers is need be only large enough to supply
just the limited number that can be so connected
comprising an electroresponsive device, and
means for ‘energizing said electroresponsive
1. Controlling means for an electric circuit
at any one time.
A ground fault involving more than one con
ductor can cause operation of electroresponsive
device from said circuit so as to be dependent
solely on overvoltage to effect a circuit control
ling action upon the occurrence of a ground
fault on said circuit in a time proportional to the
device 4! since under such fault conditions the
restraining torque proportional to EA decreases
to zero at the fault.
Accordingly for a fault in
volving two conductors to ground and with line
drop compensation in each phase conductor, we
distance of said device from said fault.
40
2. Ground ifault controlling means for
-
an
electric circuit having a grounded neutral, com
prising an electroresponsive device, and means
for energizing said electroresponsive device from
will have zero restraint on windings 414' to ill’
of relay 4! , if the fault is at that limiting position
said circuit so as to be responsive to the ratio of
on protected circuit iii for which the line drop 45 the area de?ned by the triangle formed by the
compensation has been set. Furthermore, for
line-to-line voltage vectors of said circuit to the
any other such fault between that limiting posi
?rst power of the zero phase sequence voltage
tion and the relay, there will be an excess in com
existing on said circuit upon the occurrence of a
pensation which, in the case of a two conductor
ground fault thereon so as to effect a controlling
to ground fault, will result in the reversal of the 50 action in a time proportional to the distance of
said device from said ground fault.
effective phase rotation of the three phase Volt-1
age connected to windings M’ to M”, and EA
3., Controlling means for an electric circuit
comprising a distance responsive device ener
will, therefore, become an operating torque in
stead of a restraint and will properly cause the
gized from said circuit including a movable con
closure of contacts 52 of relay Iii without any
tact controlling member, and means for effecting
assistance from windings £28’ and iii’. In this
a circuit controlling action of said contact
respect the protected system of Fig. 4 differs from
the protective system of Fig. 1. Consequently, if
controlling member dependent solely upon the
zero phase sequence voltage existing on said
a fault to ground involving more than one phase
circuit with the occurrence of a ground fault
conductor of protected circuit is can occur, 60 thereon in a time proportional to the distance of
means such as relay contacts ‘is may be provided
said device from said fault.
to modify or prevent operation of electrorespon
4. vControlling means for an electric circuit
sive device ill on such ground faults involving
comprising an electroresponsive device, a source
more than one conductor. Various means for
of control potential, means for normally
distinguishing between a single line to ground 65 energizing said device from said source, a
and a double line to ground fault are known.
capacitor, means for charging said capacitor
One such arrangement which might advanta
from said source, means for disconnecting said
geously be used in connection with Fig. 4 is dis
source from said device and from said capacitor
closed and claimed in copending application Se
rial No. 453,661-Neher, ?led August 5, 1942, and
assigned to the same assignee as the present
application.
Another means for distinguishing
upon the occurrence of an abnormal condition on
said circuit, and means for maintaining said
electroresponsive device energized from said
charge on said capacitor for a variable time after
the occurrence of said abnormal condition.
line to ground fault, for example, is disclosed in
5. Controlling means for an electric circuit
Hanna Patent 2,272,991. In Fig. 4 I have illus 75 comprising an electroresponsive device, a source
between a double line to ground and a single
2,403,414
11
12
of control potential, means for normally
as to produce an operating torque on said device
proportioned to the zero sequence voltage of said
energizing said device from said source, a
capacitor, means for charging said capacitor
circuit and a restraining torque proportioned to
from said source, means for disconnecting said
the area de?ned by the triangle formed by the
source from said device and from said capacitor CI line-to-line voltage vectors of said circuit, and
upon the occurrence of a ground fault on said
means for compensating for the line drop pro
circuit, and means for maintaining said electro
duced by the flow of a predetermined current in
responsive device energized from said charge on
said circuit between said device and a fault at a
said capacitor for a time dependent upon the
predetermined position on said circuit.
12. A ground fault protective arrangement for
distance of said fault from said device.
6. A protective arrangement for an alternating
a three-phase electric circuit, comprising a dis
current electric circuit comprising an electro
tance relay including windings, means for ener
responsive device, a capacitor, a source of
gizing said windings from said circuit so as to
control potential, means for normally energizing
operate in response to the difference between a
said device and said capacitor from said source, 15 torque proportional to the zero sequence voltage
means for obtaining a recti?ed zero sequence
of said circuit and a torque proportional to the
quantity from said circuit for energizing said
area de?ned by the triangle formed by the line
device upon the occurrence of a ground on said
‘to-line voltage vectors of said circuit, and means
circuit, means for disconnecting said source from
for compensating for the zero phase sequence
said device and from said capacitor upon the 20 current flowing in said circuit between said de
occurrence of said ground fault, and means for
vice and a limiting fault position on said circuit
maintaining said electroresponsive device ener
so as to indicate the approximate voltage at the
gized from said charge on said capacitor for a
fault for a fault at said limiting position.
time dependent upon the magnitude of said
13. A ground fault protective arrangement for
recti?ed quantity.
a three-phase electric circuit, comprising an elec
7. A protective arrangement for a polyphase
troresponsive device including windings, and
alternating current electric circuit subject to
means for energizing said windings from said cir
ground faults thereon, comprising an e1ectrore_
sponsive device, a source of control potential,
means for normally energizing said device from
said source, a capacitor, means for charging said
capacitor from said source, means responsive to
the direction of power ?ow in said circuit for
disconnecting said source from said device and
from said capacitor upon the occurrence of said
ground fault, and means for maintaining said
cuit so as to produce an operating torque on said
device proportioned to the ?rst power of the zero
sequence voltage of said circuit and a restraining
torque proportioned to the area de?ned by the
triangle formed by the line-to~line voltage vec
tors of said circuit.
1
electroresponsive device energized from said
iii. A ground fault protective arrangement for
an electric circuit having a grounded neutral,
comprising
electroresponsive device, means for
energizing said clectroresponsive device from said
charge on said capacitor for a time dependent
circuit so as to be responsive to the ratio of the
upon the distance of said fault from said device.
area de?ned by the triangle formed by the line
to-linc voltage vectors of said circuit to the ?rst
power of the zero phase sequence voltage existing
8. A protective arrangement for an electric
circuit, comprising a normally charged capaci
tor, means for obtaining from said circuit a volt
age proportional to the zero sequence voltage
of said circuit, means responsive to a ground on
on said circuit upon the occurrence of a ground
fault thereon, and means for compensating for
said circuit for causing said capacitor to dis
said
the line
zerodrop
phaseinsequence
said circuit
voltage
at least
is concerned.
in so far
charge at a predetermined rate, and means re
sponsive to a predetermined relation between said
obtained voltage and the Voltage across said ca
an electric circuit having a grounded neutral,
comp-rising an electroresponsive device, means for
pacitor.
energizing said electroresponsive device from said
9. A protective arrangement for an electric cir
cuit, comprising a normally charged capacitor,
means for obtaining from said circuit a voltage
proportional to the zero sequence voltage of said
circuit, means responsive to a ground on said
circuit for causing said capacitor to discharge at
a predetermined rate, and means responsive to
the voltage across said capacitor decreasing to a
predetermined value relative to said obtained
voltage.
15. A ground fault protective arrangement for
circuit so as to be responsive to the ratio of the
area de?ned by the triangle formed by the 1ine~
to-line voltage vectors of said circuit to the ?rst
power of the zero phase sequence voltage existing
on said circuit upon the occurrence of a ground
fault thereon, and means for compensating for
the line drop in said circuit due to the current
flowing in said circuit.
16. A ground fault protective arrangement for
a polyphase circuit, comprising an electrorespo-n
10. A ground fault protective arrangement for 60 sive device having a movable member, means
connected to said circuit for exerting on said
a three-phase electric circuit, comprising an elec
member an operating torque proportional to the
troresponsive device including windings, means
residual current in said circuit, and means con
for energizing said windings from said circuit so
nected to said circuit for exerting on said mom"
as to operate in response to a quantity propor
her a restraining torque proportional to the area
tional to the Zero sequence Voltage of said circuit
modified by a quantity proportional to the area
de?ned by the triangle formed by the line-to-line
de?ned by the triangle formed by the line-to-line
voltage vectors of said circuit.
1'7. A ground fault protective arrangement for
voltage vectors of said circuit, and means for
a polyphase circuit, comprising an electrorespom
compensating for the line drop in said circuit
between said electroresponsive device and a fault 70 sive device having a movable member, means
connected to said circuit for exerting on said
at a predetermined position on said circuit.
member an operating torque proportional to a
11. A ground fault protective arrangement for
function of the product of the residual current
a three-phase electric circuit, comprising an elec
and the residual voltage of said circuit, and
troresponsive device including windings, means
for energizing said windings from said circuit so 75 means connected to said circuit for exerting on
13
2,403,414
the area de?ned by the triangle formed by the
said member a restraining torque proportional to
line-to-line voltage vectors of said circuit.
18. A ground fault protective arrangement for
a polyphase circuit, comprising an electrorespon Ci
sive device having a movable member, means
connected to said circuit for exerting on said
member an operating torque proportional to the
residual voltage of said circuit, means connected
r
14
to the area de?ned by the triangle formed by the
line-to-line voltage vectors of said circuit, and
means responsive to the residual current in said
circuit for connecting said operating torque ex
erting means to said circuit so that it exerts a
torque proportional to the residual voltage of said
circuit.
24. A ground fault protective arrangement for
a polyphase circuit, comprising an electro-respon10 sive device having a movable member, means for
straining torque proportional to the area de?ned
exerting on said member an operating torque,
by the triangle formed by the line-to-line volt
to said circuit for exerting on said member a re
means connected to said circuit for exerting on
age vectors of said circuit, and means connected
said member a restraining torque proportional
to said circuit for controlling the operation of
one of said torque exerting means in accordance 15 to the area de?ned by the triangle formed by the
line-to-line voltage vectors of said circuit, and
with the number of conductors involved in a fault
on said circuit.
19. A ground fault protective arrangement for
means responsive to a predetermined electric con
to said circuit for exerting on said member a re“
25. In a ground fault protective arrangement
for a polyphase circuit, a single distance relay di~
rectly operable in response to a fault to ground
on any conductor of said polyphase circuit, and
means connected to said circuit for modifying the
operation of said single distance relay in accord
ance with the number of conductors involved in a
fault on said circuit.
26. In a protective system for an electric cir
cuit subject to the occurrence of fault conditions
dition of said circuit indicative of a ground fault
involving less than a predetermined number of
a polyphase circuit, comprising an electrorespon
sive device having a movable member, means 20 line conductors of said circuit l or connecting said
operating torque exerting means to said circuit
connected to said circuit for exerting on said
so that it exerts a torque proportional to the
member an operating torque proportional to the
residual voltage of said circuit.
residual voltage of said circuit, means connected
straining torque proportional to the area de?ned
by the triangle formed by the line-to~line volt
age vectors of said circuit, and means connected
to said circuit for controlling the operation of
said ?rst mentioned torque exerting means in
accordance with the number of conductors in
volved in a fault on said circuit.
20. A ground fault protective arrangement for
a polyphase circuit, comprising an electrorespon
sive device having a movable member, means
thereon, switching means for interrupting said
circuit, and means dependent upon the magni
tude of the residual potential of said circuit for
distinguishing between double line to ground and
single line to ground faults on said circuit for
controlling the operation of said switching means.
2'7. A ground fault relay for an electric circuit
?ned by the triangle formed by the line-to-line 4-0
comprising an operating winding, means con
voltage vectors of said circuit, and timing means
nected to said circuit for energizing said Winding
responsive to a ground fault on said circuit for
in response to the ?rst power of the zero phase
varying the response of one of said torque exert
sequence voltage at a predetermined point on said
ing means.
circuit, and means responsive to a ground fault
21. A ground fault protective arrangement for
on said circuit for varying the energization of
a polyphase circuit, comprising an electrorespon
said winding to effect the operation of said relay
sive device having a movable member, means
in a time dependent upon the distance between
connected to said circuit for exerting on said
the fault and said predetermined point.
member an operating torque proportional to the
28. A ground fault relay for an electric circuit
residual voltage of said circuit, means connected 50
comprising a movable circuit controlling element
to said circuit for exerting on said member a
having a normal position and a circuit controlling
restraining torque proportional to the area de
position, and means for moving said element im
?ned by the triangle formed by the line-to-line
mediately to said circuit controlling position in.
voltage vectors of said circuit, and timing means
connected to said circuit for exerting on said
member an operating torque proportional to the
residual voltage of said circuit, means connected
to said circuit for exerting on said member a
restraining torque proportional to the area de
responsive to a ground fault on said circuit for
varying the response of said operating torque
exerting means.
22. A ground fault protective arrangement for
a polyphase circuit, comprising an electrorespon
sive device having a movable member, means for.
exerting on said member an operating torque,
means connected to said circuit for exerting on
response to a ground fault within a predeter
mined distance of a predetermined point on the
circuit including means adapted when connected
to said circuit at said point for exerting on said
element a restraining torque which is propor
tional to the area de?ned by the triangle formed
by the line-to-line voltage vectors of said circuit
and Which is in a direction to oppose movement
of said element from said normal position to said
said member a restraining torque proportional
circuit controlling position, and means adapted
to the area de?ned by the triangle formed by the
line-to-line voltage vectors of said circuit, and 65 when connected to said circuit at said point for
exerting on said element in a direction to effect
means responsive to a ground fault on said cir
movement thereof to said circuit controlling posi
cuit for connecting said operating torque exerting
tion a torque which is proportional to the zero
means to said circuit so that it is energized by
phase sequence voltage at said point and which
the residual voltage of said circuit.
exceeds said restraining torque when the zero
23. A ground fault protective arrangement for
a polyphase circuit, comprising an electrorespon 70 phase sequence voltage at said point exceeds a
predetermined value below the value existing at
sive device having a movable member, means for
said point When a ground fault occurs at said
exerting on said member an operating torque,
point.
means connected to said circuit for exerting on
29. A directional ground fault relay for an
said member, a restraining torque proportional 75
electric circuit comprising a movable circuit con
2,403,414
15'
trolling member, two electromagnets cooper
atively arranged to exert on said member a torque
proportional to a function of the product of the
?uxes of said electromagnets, means for exerting
on said, member a torque in a direction to restrain Cl
said member from moving in a circuit controlling
direction, means for energizing one of said e1ec—
tromagnets from said circuit with a current
which is proportional to a zero phase sequence
voltage of said circuit, and means for energizing 10
the other of said electromagnets from said circuit
with a current which is proportional to the
residual current in said circuit, said other of said
electromagnets being saturated by its energizing
16
of said circuit, and means for energizing the
other of said electromagnets from said circuit
with a current which is proportional to the re
sidual current in said circuit, said other of said
electromagnets being saturated by its energizing
current when the residual current in said circuit
exceeds a predetermined value.
31. A directional ground fault relay i or an elec
tric circuit comprising a movable circuit control»
ling member, two electromagnets cooperatively
arranged to exert on said member a torque pro
portional to a function of the product of the
fluxes of said electromagnets, means for exerting
on said member a torque in a direction to restrain
said member from moving in a circuit controlling
direction, means for energizing one of said elec
exceeds a predetermined value.
tromagnets from said circuit with a current
30. A directional ground fault relay for an
which is proportional to a Zero phase sequence
electric circuit comprising a movable circuit con
voltage of said circuit, means for energizing the
trolling member, two electromagnets cooperative~
other oi‘ said electromagnets from said circuit
1y arranged to exert on said member a torque 20
With a current which is proportional to the re
proportional to function of the product of the
sidual current in said circuit, said other of said
?uxes of said electromagnets, means connected
electrom agnets being saturated by its energizing
to said circuit for exerting on said member in a
current when the residual current in said circuit
direction to restrain said member from moving
exceeds a predetermined value, and timing means
in a circuit controlling direction a torque propor~
responsive to a ground fault on said circuit for
tional to the area de?ned by the triangle formed
varying the energization of one of said electro
by the line-to-line voltage vectors of said cir
magnets a predetermined time after the ground
cuit, means for energizing one of said electro
fault occurs.
magnets from said circuit with a current which
OLIVER C. TRAVER.
is proportional to a zero phase sequence voltage 30
current when the residual current in said circuit >
s
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