Ground Fault Tolerant Downhole Data Communication System
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Solution Overview
Problem
Existing downhole communication systems for ESPs rely on large inductive isolation chokes and high voltage capacitors, which limit data transfer rates and are unreliable, and fail to protect sensitive electronics during ground faults.
Innovation Solution
A power and bi-directional data communication system using a megger test diode and high voltage protection circuit located below the downhole motor's wye point, which limits voltage to safe levels during ground faults, eliminating the need for large inductive chokes and high voltage capacitors, and enables reliable communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large inductive isolation chokes are used to protect downhole electronics from high voltage events, then reliability is improved, but device complexity and data transfer rate are worsened
Solution Approach 1:
The patent removes the large inductive isolation choke from the system by implementing a ground fault detection mechanism that identifies ground faults and isolates the affected phase, thereby eliminating the need for bulky inductive chokes while maintaining protection functionality
Solution Approach 2:
The patent replaces the mechanical/inductive isolation approach (large chokes) with an electronic control approach using ground fault detection circuitry and controlled isolation, substituting physical isolation components with intelligent detection and control mechanisms
2Reliability
If high voltage capacitors are used between the downhole instrument and motor wye point, then protection from high voltage is improved, but device complexity and cost are worsened
Solution Approach 1:
The patent eliminates high voltage capacitors from the system by using ground fault detection and controlled phase isolation to protect the instrument, removing the need for expensive and complex high voltage capacitor components
Solution Approach 2:
The patent uses lower voltage, less expensive components that can be replaced or protected through control mechanisms, rather than relying on expensive high voltage capacitors, thereby reducing overall system cost and complexity
3Use of energy by moving object
If DC power is tapped from the wye point of the motor, then power supply is improved, but vulnerability to ground faults is worsened
Solution Approach 1:
The patent implements ground fault detection circuitry that continuously monitors the power lines for ground faults and provides feedback control to isolate the instrument from affected phases, thereby maintaining power supply while protecting against ground fault damage
Solution Approach 2:
The patent performs preliminary ground fault detection before damage can occur, identifying potential ground faults early and activating protection mechanisms in advance to prevent damage to the instrument's power supply
4Reliability
If semiconductor devices with voltage clamps are used to protect downhole electronics, then protection is improved, but device complexity is worsened due to large inductive chokes still being required
Solution Approach 1:
The patent removes the large inductive choke from the protection circuit by using ground fault detection and controlled isolation methods, eliminating the need for bulky inductive components while maintaining protection functionality
Solution Approach 2:
The patent changes the protection approach from passive inductive isolation to active electronic control with ground fault detection, fundamentally altering the protection mechanism parameters to eliminate complex inductive components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system protects downhole electronics from high voltage events, allows continuous communication during ground faults, and achieves high data transfer rates without the need for expensive or unreliable components.
Implementation Method 1
A megger test diode located below the wye point of a downhole motor assembly blocks current in case a negative voltage is applied to it
Implementation Method 2
The circuit limits the voltage at its output to a lower value (preferably no greater than 80 V) and, therefore, protects the downhole electronics while still allowing communication
Data Source
AI summary
This invention relates to a data communication system/method for use in a downhole application wherein electrical energy is supplied over a multiple-conductor power cable to a motor assembly of a downhole tool such as an electric submersible pump. A power leg coupling interfaces a surface controller of a downhole instrument to the conductors of the tool's power cable. Uplink communication of telemetry data occurs via current modulation generated by the downhole instrument and interpreted by a surface controller. Downlink communication of downhole instrument data occurs over a different communication scheme supported by the downhole and surface controllers. Downlink communication scheme provides a supply of power to the downhole instrument. Protection of downhole electronics and continuity of communication is ensured in the event of a ground fault on the power cable. Both downlink and uplink communication frequencies are adaptive based on frequencies and voltages present on the power cable.