Protection circuitry for a downhole measurement tool
Systems and methods corresponding to a downhole measurement tool to balance fault current in a protective inductor are disclosed herein. A triggerable network is provided which keeps an alternating current balanced in a protective choke during a phase-to-ground fault condition in a power cable or a downhole motor of an electrical submersible pump. The triggerable network causes a conducting of current during negative polarity voltage portion(s) of the phase-to-ground fault condition via a silicon-controlled rectifier having an anode and a cathode on a path of current conduction for the negative polarity voltage during the phase-to-ground fault condition and one or more Zener diodes, where an ending cathode of the one or more Zener diodes is coupled to a gate of the silicon-controlled rectifier and an ending anode of the one or more Zener diodes is coupled to the anode of the silicon-controlled rectifier.
1. A downhole system capable of balancing an alternating current between a power cable or a downhole motor of an electrical submersible pump and a downhole measurement tool during a phase-to-ground fault condition, the downhole system comprising:
an electrical connection between a Y-point of the downhole motor of the electrical submersible pump and the downhole measurement tool; and
a triggerable network that selectively conducts during an application of a negative polarity voltage to the downhole measurement tool during the phase-to-ground fault condition, the triggerable network comprising:
a silicon-controlled rectifier having an anode and a cathode on a first path of current conduction for the negative polarity voltage during the phase-to-ground fault condition; and
one or more first Zener diodes, wherein an ending anode of the one or more first Zener diodes is coupled to a gate of the silicon-controlled rectifier and an ending cathode of the first one or more Zener diodes is coupled to the anode of the silicon-controlled rectifier.
2. The downhole system capable of claim 1 , wherein the one or more first Zener diodes comprises a plurality of Zener diodes coupled in series.
3. The downhole system capable of claim 1 , wherein a trigger current for the silicon-controlled rectifier at the gate of the silicon-controlled rectifier occurs through the one or more first Zener diodes during the application of the negative polarity voltage.
4. The downhole system capable of claim 3 , wherein the trigger current occurs based on a magnitude of the negative polarity voltage.
5. The downhole system capable of claim 1 , further comprising a diode providing a second path of current conduction for a positive polarity voltage during the phase-to-ground fault condition and one or more second Zener diodes configured to limit a magnitude of the positive polarity voltage.
6. The downhole system capable of claim 5 , wherein the one or more second Zener diodes comprises a plurality of Zener diodes coupled in series.
7. The downhole system capable of claim 1 , further comprising an inductor coupled to the Y-point of the downhole motor of the electrical submersible pump and the downhole measurement tool, the inductor being of a selected inductance for filtering alternating current ripple voltage from the downhole motor of the electrical submersible pump to the downhole measurement tool, wherein:
the anode of the silicon-controlled rectifier is coupled to a ground; and
the cathode of the silicon-controlled rectifier is coupled to the inductor.
8. The downhole system capable of claim 1 , wherein the triggerable network further comprises a blocking diode, and wherein the ending anode of the one or more first Zener diodes and the gate of the silicon-controlled rectifier are coupled through the blocking diode.
9. A downhole measurement tool having circuitry capable of balancing an alternating current during a phase-to-ground fault condition, the downhole measurement tool capable of being coupled to a Y-point of a three-phase downhole motor of an electrical submersible pump, the circuitry of the downhole measurement tool comprising:
a triggerable network that selectively conducts during an application of a negative polarity voltage to the downhole measurement tool, the triggerable network comprising:
a silicon-controlled rectifier having an anode and a cathode on a first path of current conduction for the negative polarity voltage during the phase-to-ground fault condition; and
one or more first Zener diodes, wherein an ending anode of the one or more first Zener diodes is coupled to a gate of the silicon-controlled rectifier and an ending cathode of the first one or more Zener diodes is coupled to the anode of the silicon-controlled rectifier; and
an inductor commutating circuit to limit a magnitude of a positive polarity voltage during the phase to-ground fault condition.
10. The downhole measurement tool of claim 9 , wherein the one or more first Zener diodes comprises a plurality of Zener diodes coupled in series.
11. The downhole measurement tool of claim 9 , wherein a trigger current for the silicon-controlled rectifier at the gate of the silicon-controlled rectifier occurs through the one or more first Zener diodes during the application of the negative polarity voltage.
12. The downhole measurement tool of claim 11 , wherein the trigger current occurs based on a magnitude of the negative polarity voltage.
13. The downhole measurement tool of claim 9 , wherein the inductor commutating circuit comprises a diode providing a second path of current conduction for the positive polarity voltage during the phase-to-ground fault condition and one or more second Zener diodes.
14. The downhole measurement tool of claim 13 , wherein the one or more second Zener diodes comprises a plurality of Zener diodes coupled in series.
15. The downhole measurement tool of claim 9 , further comprising an inductor coupled to the Y-point of the downhole motor of the electrical submersible pump and the downhole measurement tool, the inductor being of a selected inductance for filtering alternating current ripple voltage from the downhole motor of the electrical submersible pump to the downhole measurement tool, wherein:
the anode of the silicon-controlled rectifier is coupled to a ground; and
the cathode of the silicon-controlled rectifier is coupled to the inductor.
16. The downhole measurement tool of claim 9 , wherein the triggerable network further comprises a blocking diode, and wherein the ending anode of the one or more first Zener diodes and the gate of the silicon-controlled rectifier are coupled through the blocking diode.
17. A method of balancing a phase-to-ground fault condition between a power cable or a three-phase downhole motor of an electrical submersible pump and a downhole measurement tool, the method comprising:
coupling a Y-point of the downhole motor of the electrical submersible pump to the downhole measurement tool;
selectively conducting through a triggerable network during an application of a negative polarity voltage to the downhole measurement tool during the phase-to ground fault condition, wherein the triggerable network comprises:
a silicon-controlled rectifier having an anode and a cathode on a first path of current conduction for the negative polarity voltage during the phase-to-ground fault condition; and
one or more first Zener diodes, wherein an ending anode of the one or more first Zener diodes is coupled to a gate of the silicon-controlled rectifier and an ending cathode of the first one or more Zener diodes is coupled to the anode of the silicon-controlled rectifier; and
providing a second path of current conduction for a positive polarity voltage during the phase-to-ground fault condition.
18. The method of claim 17 , wherein the one or more first Zener diodes comprises a plurality of Zener diodes coupled in series.
19. The method of claim 17 , wherein a trigger current for the silicon-controlled rectifier at the gate of the silicon-controlled rectifier occurs through the one or more first Zener diodes during the application of the negative polarity voltage.
20. The method of claim 19 , wherein the trigger current occurs based on a magnitude of the negative polarity voltage.
21. The method of claim 17 , wherein the second path of current conduction for the positive polarity voltage comprises a diode and one or more second Zener diodes configured to limit a magnitude of the positive polarity voltage.
22. The method of claim 21 , wherein the one or more second Zener diodes comprises a plurality of Zener diodes coupled in series.
23. The method of claim 21 , wherein:
the Y-point of the downhole motor of the electrical submersible pump is coupled to the downhole measurement tool through an inductor of a selected inductance for filtering alternating current ripple voltage from the downhole motor of the electrical submersible pump to the downhole measurement tool;
the anode of the silicon-controlled rectifier is coupled to a ground; and
the cathode of the silicon-controlled rectifier is coupled to the inductor.
24. The method of claim 21 , wherein the triggerable network further comprises a blocking diode, and wherein the ending anode of the one or more first Zener diodes and the gate of the silicon-controlled rectifier are coupled through the blocking diode.