Protection circuitry for a downhole measurement tool

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.

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.