Data transmission system

A data transmission system which may be used in any industrial installation in which an A.C. powered device is remotely located and in which it is desired (i) to monitor certain parameters, and/or (ii) to control certain operational functions at the remote site. The power cable used to carry A.C. power to the remotely operating device is also used to carry instrumentation, communication, and control signals from the local control and readout equipment located at the surface to an instrumentation and control package installed at the remote site in the down-hole location. The present invention comprises means for the simultaneous bidirectional transmission of digital data between the local and remote sites by means of a modulated D.C. loop current to thereby accomplish the required monitoring and control functions.

BACKGROUND OF THE INVENTION 
1. Field of the invention 
This invention relates to the field of 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. 
2. The Prior Art 
Numerous industrial installations exist in which an A.C. powered motor and 
pump assembly or other alternating 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"). In 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 .phi. 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. 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 .phi. power supply, Boyd transmits the communication signal over two 
phases of the 3 .phi. power supply, and Boyd et al., McGibbeny et al., and 
Balkani all transmit the communication signal over all three phases of the 
3 .phi. 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 .phi. 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 dam. 
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 dam. 
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 at. 
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 .phi. 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 dam, 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 .phi. 
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. 
SUMMARY OF THE INVENTION 
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 
instrumentation 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 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 digital data provides a relatively simple 
(i.e. inexpensive), rapid, and reliable means of data transmission.

DETAILED DESCRIPTION OF THE INVENTION 
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 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. The 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, Okla., 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 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. 
Power 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 which 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 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 resistor 214=75 .OMEGA.; 
Second preset resistor 244=150 .OMEGA.; 
Reference resistor 250=250 .OMEGA.; 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 250, a first serial output 
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 first 
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 dam. The conversion of 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 40 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, Calif. 
The second current measurement circuit 230 includes a second current 
sensing resistor 232 and a second current 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 dam. 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 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 in the art. This invention, therefore, is not 
intended to be limited to the particular embodiments herein disclosed.