Note: Descriptions are shown in the official language in which they were submitted.
- 2152422
REDA:021
DATA TRL.NSMISSION SYSTEM
This invention, relates to the-field cf electrical
instrumentation and control, and more particularly, to an
instrumentation apparatus which enables the sensing of
physical parameters and the control of operational
functions in a remotely located A.C. powered installation.
Numerous industrial installations exist in which an
A.C. powered motor and pump assembly or other alternating
_.20 current device is operated at a remote location to which
access is difficult, costly and/or impractical, if not
impossible. An example of such an installation is the motor
and pump assembly of a submersible pumping system operating
. near the bottom of a subterranean bore-hole (referred to as
"down-hole"). Tn such an installation, there is.often a
requirement to monitor certain physical parameters present
~in the down-hole environment, particularly the temperature
and pressure therein. Moreover, in such installations,
there will also exist the requirement to remotely control
certain operational functions such as the flow of fluid
through a down-hole solenoid controlled valve.
Prior art solutions to the problem of providing a
communication link between a locally situated control and
monitoring unit and a remotely situated control and
instrumentation unit have included the use of the
conductors of the 3 ~ power supply cable for the
transmission of communication signals thereby precluding
the need for a separate communication pathway. Examples of
such prior art systems are disclosed in U.S. Pat. Nos.
2152422
-2-
3,284,669, 3,340,500, 4,157,535, 4,178,579, 4,788,545, and
4,803,483 issued to Boyd, Boyd et al., Balkanli, McGibbeny
et al., Farque, and Vandervier et al. respectively. Of
these prior art systems, Farque and Vandervier et al. both
transmit the communication signal over one phase of the 3
power supply, Boyd transmits the communication signal
over two phases of the 3 ~ power supply, and Boyd et al.,
McGibbeny et al., and Balkani all transmit the
communication signal over all three phases of the 3 ~ power
supply by means of neutral points at the remote and local
sites.
In those prior art systems that employ the conductors
of the 3 ~ power supply line as a conducting path, the
signal transmission between the local and remote unit
ranges from unidirectional and analog in the case of Boyd,
Boyd et al., Farque, and Vandervier et al., to
bidirectional and analog in the case of McGibbeny et al.
and Balkanli.
Other prior art solutions to the problem of providing
a communication link between a locally situated control and
monitoring unit and a remotely situated control and
instrumentation unit have simply included the use of a
dedicated conductor (or conductors) for the transmission of
data. Examples of such prior art systems are disclosed in
U.S. Pat. Nos. 3, 406, 359 and 3, 991, 611 issued to Welz et
al. and Marshall, III et al. respectively. Of these prior
art systems, Marshall, III et al. utilizes a single
conductor for all communication while Welz et al. utilizes
a different dedicated conductor for each piece of data.
In those prior art systems utilizing a separate
dedicated conducting path for communications, the signal
transmission between the local and remote unit varies from
the bidirectional serial transmission of digital
information in the case of Marshall, III et al. to the
unidirectional parallel transmission of analog data in the
case of Welz et al.
CA 02152422 2001-03-06
73603-4
3
Thus, the prior art solutions to the problem of
communication between a remotely located down-hole unit and a
locally located surface unit have not included: (1) the
transmission of digital data by means of the conductors of the
3 ~ power supply line; (2) the simultaneous bidirectional
transmission of data (whether digital or otherwise); and/or (3)
the generation and transmission of digital data by means of a
modulated analog loop current.
The present invention overcomes these limitations of
the prior art by permitting the simultaneous bidirectional
transmission of digital data, in the form of a modulated D.C.
loop current, between a local surface unit and a remote down-
hole unit by utilizing the conductors of the 3 ~ power supply
line as a signal path thereby precluding the need for a
separate conducting path and at the same time permitting the
rapid and reliable transmission of data between a local and a
remote site.
According to one broad aspect the invention may be
defined as a data transmission and instrumentation system in
which electrical energy is passed from a surface location to a
down-hole location over a cable including a plurality of
conductors to energize equipment at the down-hole location,
comprising: a down-hole assembly positioned at the down-hole
location, comparing, a first balanced inductor network coupled
to the conductors, said first balanced inductor network having
a first neutral point, and a down-hole unit coupled between a
reference potential and the first neutral point in the first
inductor network; and a first digital data transmission
assembly operably coupled to said cable to transmit digital
data to the surface unit over said cable conductors; and a
CA 02152422 2001-03-06
73603-4
3a
surface assembly positioned at the surface location,
comprising, a second balanced inductor network coupled to the
conductors, the inductors in the second network being disposed
and connected in a configuration substantially similar to that
of the inductors in the first network and having a second
neutral point, and a surface unit coupled between the reference
potential and the second neutral point in the second inductor
network, the second neutral point being held substantially at
the same relative potential as the first neutral point; and a
second digital data transmission assembly operably coupled to
said cable to transmit digital data to the down-hole unit over
said cable conductors; wherein said first and second digital
data transmission assemblies are each configured to be operable
to transmit digital data as current is communicated on the
cable conductors and regardless of whether the other trans-
mission assembly is transmitting data.
The present invention finds utility in industrial or
other installations wherein (i) an A.C. powered device is
remotely located; (ii) it is desired to monitor certain
parameters of interest, such as temperature or pressure, at the
remote site; and/or (iii) it is desired to remotely control
certain operational functions there. This invention enables
the accurate sensing of such parameters of interest and the
control of functions at the remote site by means of the
bidirectional transmission of digital data between a locally
controlled surface unit and a remotely located down-hole unit.
Digital data is transmitted between the control and monitoring
equipment at the local site on the surface and the instru-
mentation and control equipment remotely located in the down-
hole location by means of the power cable which carries the
A.C. power to the remotely located A.C. device; thus, there
CA 02152422 2001-03-06
73603-4
3b
is no requirement for any additional electrically conducting
instrumentation and/or control lines to the remote location.
Further, the use of a modulated analog loop current for the
transmission of the
2152422
-4-
digital data provides a relatively simple (i.e.
inexpensive), rapid, and reliable means of data
transmission.
FIG. 1 is a schematic diagram of a three phase A.C.
powered system in which an apparatus in accordance with the
present inrEntion is installed.
FIG. 2 is a schematic diagram illustrating the
operation of the embodiment of the apparatus depicted in
Figure 1.
FIG. 3 is a schematic diagram of the surface unit of
the apparatus of Figure 1.
FIG. 4 is a schematic diagram of the down-hole unit of
the apparatus of Figure 1.
A data transmission and instrumentation system and
apparatus'~is described which is particularly useful for (i)
remotely sensing physical characteristics of interest such
as, for example, the pressure and temperature in a down
hole or submersible well pumping system, (ii) remotely
controlling the state of switching, or other control
devices, such as, for example, solenoid actuated valves or
solenoid latches, and/or (iii) providing a reliable means
of bidirectional communication between a locally positioned
control and monitoring unit and a remotely positioned
control and instrumentation unit. As will be apparent from
the following detailed description, the inventive concepts
disclosed herein are applicable to numerous other
instrumentation applications. In the description, like
elements in the various FIGURES will be designated by the
same numerical designations.
A presently preferred embodiment of the invented
apparatus is used advantageously in an electric motor
powered submersible pumping system to: (i) monitor certain
down-hole parameters, such as pressure and temperature,
(iii) control certain down-hole equipment, and (iii) to
provide bidirectional communication between the down-hole
2152422
_5_
location and surface location to enable the required
monitoring and control functions.
The presently preferred embodiment of the subject
invention is now described with reference to FIG. 1. The
submersible pumping system includes a submersible motor and
pump assembly 10. "_'h' motor is shown symbolically by three-
phase A.C. windings 20, Y-connected (a balanced inductor
network) and having a neutral, ungrounded node 30; the
'pump, operatively coupled to the motor, is not individually
shown. Although many types of motors and pumps may be
operated through use of the present invention, one
exemplary combination would be a model DN 280 pump,
manufactured and sold by Reda, of Bartlesville, Oklahoma,
operated 'by a 540 series motor, manufactured and sold by
Reda. The-~motor operates on 2350 Volts, drawing 26 Amps,
and provides 100 Hp.
A down-hole unit 40, described more fully below, is
electrically coupled to (i) the neutral node 30 of motor
windings 20 by a large inductor 35, and (ii) to earth
ground 50. The large inductor 35 filters out the motor A.C.
from interfering with communications signals transmitted
between the down-hole unit 40 and a surface unit 100.
Inductor 35 may, in an embodiment depicted herein, be a 140
Henry inductor.
On the surface 120, a conventional A.C. power source
55 supplies power via conductors 75 to the motor windings
20 in the motor and pump assembly 10 and also to an
auxiliary three-phase, Y-connected (a balanced inductor
network) surface set of windings 90 having a neutral,
ungrounded node 70. The surface windings 90 are connected
in a configuration identical to that of the motor windings
20; this ensures that the neutral nodes 30 and 70 are held
at the same relative potential. Also shown on the surface
120 is the surface unit 100, described more fully below.
The surface unit 100 is electrically coupled to the neutral
node 70 by a large inductor 110. The large inductor 110
212422
-6-
serves to filter out the motor A.C. from interfering with
communications signals transmitted between the surface unit
100 and the down-hole unit 40. Once again, inductor 110, in
an exemplary embodiment as depicted herein, may be a 150
Henry inductor.
Pow~z from the power source 55 is carried to the down-
hole motor windings 20 by a power cable 115 which extends
into the bore-hole 80. Thus, the down-hole unit 40 is
electrically coupled to the surface unit 10 through a
circuit comprised of large inductor 35, motor windings 20,
power cable 115 with conductors 75, auxiliary windings 90,
large inductor 110, and earth ground 50.
With reference to FIG. 2, the operation of the
depicted embodiment is now described, in particular the
means by'vihich the surface unit 100 and the down-hole unit
40 communicate information with one another simultaneously
in a bidirectional fashion.
The down-hole unit 40 includes a first current
measurement circuit 200, a reference resistor 250, and a
first serial output circuit 210. The first current
measurement circuit 200 includes a first current sensing
resistor 202 and a first current measurement signal
generator 204. The first serial output circuit 210 includes
a first switch assembly 212 and a first preset resistor
214.
The surface unit 100 includes a D.C. power supply 220,
a second current measurement circuit 230, and a second
serial output circuit 240. The second current measurement
circuit 230 consists of a second current sensing resistor
232 and a second current measurement signal generator 234.
The second serial output circuit 240 includes a second
switch assembly 242 and a second preset resistor 244. D.C.
power supply 220 provides power for the downhole electronic
components. D.C. power supply 220 has a small constant
current draw such as on the order of 5 mA. This current
212422
draw is largely insignificant relative to the current
consumed by the preset resistors.
In operation, the current measurement circuits 200 and
230 provide a measurement of the analog loop current 260
which will vary as a function of the position of the
switches 242 and 212. This permits each unit (surface unit
100 and down-hole unit 40) to simultaneously transmit and
receive digital information. This is accomplished by
measuring the analog loop current 260 and transmitting
serial data by means of the switches 212 and 242. For
example if we assign the following values:
First preset res~.stor 214 - 75 S2;
Second preset resistor 244 = 150 f2;
Reference resistor 250 = 250 S2; and
~~ D.C. power means 220 = 10 V
The following analog loop current measurements (including
the above-referenced constant D.C. power supply current of
approximately 5 mA) will be determined as a function of the
position of the switches 212 and 242:
Analog Loop
First Switch 212 Second Switch 242 Current 260
OPEN OPEN - 26 mA
CLOSED OPEN 36 mA
OPEN CLOSE 31 mA
CLOSED CLOSE 45 mA
Since each unit 40 and 100 measures the analog loop current
260, each may determine whether a digital "0" or "1" is
being transmitted by the other unit even if the respective
unit is itself simultaneously transmitting data via the
power cable 115 to the other unit.
With reference to FIG. 3, the operation and specific
elements of down-hole unit 40 is now described. The down-
hole unit 40 includes a first current measurement circuit
200, a reference resistor 2~0, a first serial output
.~ 212422
_g_
circuit 210, and a first microprocessor controller 300. The
first microprocessor controller 300 may be a CDP 1805
microprocessor manufactured by Harris.
The first current measurement circuit 200 consists of
a first current sensing resistor 202 and a first current
measurement signal generator 204 in the form of a first
differential amplifier. The first serial output circuit 210
consists of a first switch assembly 212 in the form of a
f_irst~FET switch and a first preset resistor 214.
In operation the first microprocessor controller 300
. . _ receives analog inputs 310 and digital inputs 320 and
transmits analog outputs 330 and digital outputs 340
locally in the bore-hole location. The first microprocessor
controller 300 further communicates with the surface~unit
100 by means of the first current measurement circuit 200
and the first serial output circuit 210.
The first current measurement circuit 200 permits the
first microprocessor controller 300 to measure the analog
loop current 260 by means of the first current sense
resistor 202 and the first.differential amplifier 204. In
a manner commonly known in the art, the first differential
amplifier 204 produces a first analog loop current
measurement signal 370 at its output as a function of the
analog loop current 260. The first analog current
measurement signal 370 is then received by the first
microprocessor controller 300 and converted via software in
a conventional manner to digital data. The conversion of
212422
_g_
the first analog current measurement signal 370 to digital
data could also, of course, be accomplished through
conventional hardware.
The first serial output circuit 210 permits the first
microprocessor controller 300 to transmit digital data by
means of the first FET switch 212 and the first preset
resistor 214. The operation of the first FET switch 212 is
controlled in a manner commonly known in the art by means
of a first serial data output signal 360 to open or close
the current path ,through the first FET switch 212 to
thereby permit the transmittal of digital data by varying
the resistance of the first serial output circuit 210
between two discrete values. As already discussed above, by
varying the resistance of the first serial output circuit
210 the analog loop current 260 is also varied, thereby
permitting the bidirectional transmission of digital data
between the down-hole unit 4.0 and the surface unit 100.
With reference to FIG. 4, the operation and specific
elements of surface unit 100 are now described. The surface
unit 100 includes a D.C. power supply 220, a second current
measurement circuit 230, a second serial output circuit
240, and a second microprocessor controller 400. Once
again, the second microprocessor controller 400 may be a
80C196 microprocessor manufactured by Intel Corporation of
San Jose, California.
The second current measurement circuit 230 includes a
second current sensing resistor 232 and a second current
'~- 2152422
-10-
measurement signal generator 234 in the form of a second
differential amplifier. The second serial output circuit
240 includes a second switch assembly 242 in the form of a
second FET switch and a second preset resistor 244.
In operation the second microprocessor controller 400
receives digital inputs 430 and transmits analog outputs
410 and digital outputs 420 locally at the surface
location. The second microprocessor controller 400 further
communicates with the down-hole unit 40 by means of the
second current measurement circuit 230 and the second
serial output circuit 240.
The second current measurement circuit 230 permits the
second microprocessor controller 400 to_measure the analog
loop current 260 by means of the second current sense
resistor 232 and the second differential amplifier 234. In
a manner commonly known in the art, the second differential
amplifier 234 produces a second analog loop current
measurement signal 440 at its output as a function of the
analog loop current 260. The second analog current
measurement signal 440 is then received by the second
microprocessor controller 400 and converted via software in
a conventional manner to digital data. The conversion of
the second analog current measurement signal 440 to digital
data could also, of course, be accomplished through
conventional hardware.
The second serial output circuit 240 permits the
second microprocessor controller 400 to transmit digital
_2152422
data by means of the second FET switch 242 and the second
preset resistor 244. The operation of the second FET switch
242 is controlled in a manner commonly known in the art by
means of a second serial data output signal 450 to open or
close the current path through the second FET switch 242 to
thereby permit the transmittal of digital data by varying
the resistance of the second serial output circuit 240. As
already discussed above, by varying the resistance of the
second serial output circuit 240 the analog loop current
260 is also varied, thereby permitting the bidirectional
transmission of digital data between the down-hole unit 40
and the surface unit 100.
A data transmission and instrumentation apparatus has
been described for remote use with alternating current
devices, such as, for example, a down-hole submersible
motor and pump assembly. All communication between the
local and remote site is accomplished through the power
cable, which carries power to the A.C. device, without the
use of additional communication lines.
While the invention has been particularly shown and
described with reference to preferred embodiments for use
in a submersible pumping application, it should be
understood that persons skilled in the art may make various
changes in form and detail of the present invention without
departing from the spirit and scope of the invention; and
further, that the principles disclosed are susceptible of
other applications which will be apparent to those skilled
~''~ 212422
-12-
in the art. This invention, therefore, is not intended to
be limited to the particular embodiments herein disclosed.
