Safety controls for electrical submersible pump systems
Safety control apparatus for limiting voltages on electrical conductors included in a motor power cable that are connected to a motor of an electrical submersible pump assembly are described. The safety control apparatus include circuitry, which when electrically coupled to the electrical conductors of the motor power cable, is configured to controllably connect and disconnect the electrical conductors to and from, respectively, a motor load element, to provide a braking function limiting the motor rotational speed, and thereby limit the voltage level that the rotation of the motor may induce onto the electrical conductors.
1 . A system comprising:
a safety control apparatus configured to be electrically coupled to a motor power cable of a motor, the motor configured to operate a submersible pump, the motor and the submersible pump configured to be deployed downhole in a wellbore and operated to pump a fluid present within the wellbore into a production tubing or conduit extending within the wellbore,
wherein the safety control apparatus comprises a controller coupled to a switching device, the controller configured to operate the switching device to controllably connect and disconnect a set of electrical conductors of the motor power cable to and from, respectively, one or more motor loads in order to maintain a voltage level present on the set of electrical conductors of the motor power cable at or below a threshold voltage level when the motor is not being electrically powered to operate the submersible pump and when the motor is being mechanically rotated by a flow of fluid passing through the submersible pump.
2 . The system of claim 1 , wherein the safety control apparatus further comprises a rectifier configured to be electrically coupled to the set of electrical conductors of the motor power cable, the rectifier configured to rectify the voltage level present on the set of electrical conductors and to rectify the voltage level to provide a direct current output voltage as a DC output.
3 . The system of claim 2 , wherein the safety control apparatus is configured to operate the switching device based on a comparison of the DC output to a predetermined value of a threshold voltage limit.
4 . The system of claim 1 , wherein operation of the switching device to controllably connect and disconnect the motor power cable to and from, respectively, the one or more motor loads comprises providing a pulse-width-modulated signal generated by the controller to an input of the switching device.
5 . The system of claim 4 , wherein a width of a pulse of the pulse-width-modulated signal is determined by a time period when a sensed voltage level that is present on the set of electrical conductors of the motor power cable is at or above a maximum threshold voltage level.
6 . The system of claim 1 , wherein the one or more motor loads comprise an electrical resistor.
7 . The system of claim 1 , wherein the one or more motor loads comprise an electrical energy storage device.
8 . The system of claim 1 , wherein the switching device comprises an insulated-gate bipolar transistor.
9 . The system of claim 1 , wherein the safety control apparatus is configured to limit a speed of rotation of the motor using the one or more motor loads.
10 . The system of claim 1 , wherein the threshold voltage level is 50 volts.
11 . A method comprising:
electrically coupling a safety control apparatus to a set of electrical conductors of a motor power cable that are coupled to a motor of an electrical submersible pump apparatus, the electrical submersible pump apparatus configured to be positioned within a wellbore and configured to be operated by the motor in order to provide an artificial lift of formation fluids from within the wellbore;
monitoring, by the safety control apparatus, a voltage level that is present on the set of electrical conductors of the motor power cable; and
controllably connecting and disconnecting, using at least one switching device, the set of electrical conductors of the motor power cable to and from, respectively, a motor load configured to limit the voltage level that is present on the set of electrical conductors to a predetermined threshold voltage level based on the monitoring of the voltage level present on the set of electrical conductors of the motor power cable when the motor is not being electrically powered to operate the submersible pump and when the motor is being mechanically rotated by a flow of fluid passing through the submersible pump.
12 . The method of claim 11 , wherein the monitoring of the voltage level on the set of electrical conductors of the motor power cable comprises rectifying voltages present on the set of electrical conductors to provide a direct current (DC) output voltage, and monitoring a level of the DC output voltage.
13 . The method of claim 11 , wherein controllably connecting and disconnecting the set of electrical conductors of the motor power cable to and from, respectively, the motor load comprises providing a pulse-width-modulated signal to an input of the at least one switching device.
14 . The method of claim 11 , further comprising controllably connecting and disconnecting the set of electrical conductors of the motor power cable to and from, respectively, the motor load to limit a speed of rotation of the motor.
15 . The method of claim 11 , wherein the predetermined threshold voltage level is 50 volts.
16 . The method of claim 11 , wherein a connection between the set of electrical conductors of the motor power cable and the motor load is made based on a determination that the voltage level present on the set of electrical conductors of the motor power cable has reached the predetermined threshold voltage level, and a disconnection of the set of electrical conductors of the motor power cable from the motor load is made based on a determination that the voltage level present on the set of electrical conductors of the motor power cable is below the predetermined threshold voltage level.
17 . The method of claim 11 , wherein electrically coupling the safety control apparatus to the set of electrical conductors of the motor power cable further comprises:
monitoring an electrical line source that is coupled to the set of electrical conductors of a motor power cable to determine that the electrical line source is providing electrical power to the set of electrical conductors of the motor power cable; and
automatically, using a disconnect switch, disconnecting the set of electrical conductors of the motor power cable from the electrical line source and connecting the set of electrical conductors of the motor power cable to the safety control apparatus.
18 . A non-transitory, computer-readable medium having instructions stored thereon that are executable by a processor to perform operations comprising:
monitoring, using one or more output signals received from one or more sensors, a voltage level that is present on a set of electrical conductors of a motor power cable coupled to a motor of an electrical submersible pump assembly; and
providing an output signal to controllably connect and disconnect, using at least one switching device, the set of electrical conductors of the motor power cable to and from, respectively, a motor load configured to limit the voltage level present on the set of electrical conductors to a predetermined threshold voltage level based on the monitoring of the voltage level present on the set of electrical conductors when the motor is not being electrically powered to operate the submersible pump and when the motor is being mechanically rotated by a flow of fluid passing through the submersible pump.
19 . The non-transitory, computer readable medium of claim 18 , wherein monitoring the voltage level present on the set of electrical conductors of the motor power cable comprises rectifying voltages present on the set of electrical conductors to provide a direct current (DC) output voltage, and monitoring a level of the DC output voltage.
20 . The non-transitory, computer readable medium of claim 18 , wherein the operations further comprise controllably connecting and disconnecting the set of electrical conductors of the motor power cable to and from, respectively, the motor load to limit a speed of rotation of the motor.