Compressor Grid Fault Detection to Prevent Stall and Overload
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Solution Overview
Problem
Compressors connected to electrical grids experience rapid current increases due to voltage drops during grid faults, leading to potential stalling and thermal overload, which can cause further grid instability and false shutdowns, as the existing solutions fail to promptly and accurately detect grid faults at the individual compressor level.
Innovation Solution
A compressor monitoring system that includes current and voltage monitors, averaging modules, and a control module to detect grid faults by calculating ratios of average current and voltage values, generating a fault signal when specific thresholds are exceeded, and deactivating the motor to prevent stalling and thermal overload, while also considering mass flow, temperature, and power factor changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor continues to operate during grid voltage drops, then the compressor remains productive, but the current increases dramatically causing thermal overload and potential stalling
Solution Approach 1:
The system performs preliminary detection of grid faults by monitoring voltage and current ratios before thermal overload or stalling occurs. The control module calculates the ratio of average current to average voltage and compares it against a threshold, enabling early intervention to prevent harmful effects while maintaining productivity.
Solution Approach 2:
The system continuously monitors compressor operation and grid conditions, calculating real-time ratios of average current to average voltage. This feedback mechanism allows the control module to detect grid faults promptly and adjust operation to prevent thermal overload and stalling, resolving the contradiction between continuous operation and preventing harmful effects.
2Reliability
If the compressor is deactivated immediately upon detecting high current, then thermal overload is prevented, but false shutdowns occur due to normal startup current spikes
Solution Approach 1:
The system calculates the ratio of average current to average voltage as a preliminary indicator of grid faults. By using this ratio rather than absolute current values, the system can distinguish between grid-induced current increases (which require shutdown) and normal startup spikes (which are transient and proportional to voltage), thereby preventing false shutdowns while maintaining reliable protection.
Solution Approach 2:
The system transforms the protection criterion from monitoring absolute current values to monitoring the ratio of average current to average voltage. This parameter change allows the system to account for normal voltage-current relationships during startup while detecting abnormal ratios indicative of grid faults, thus preventing false shutdowns while maintaining thermal overload protection.
3Measurement precision
If existing grid fault detection methods are used, then general grid issues are identified, but individual compressor-level grid faults are not promptly detected
Solution Approach 1:
The system implements compressor-level segmentation of grid fault detection by monitoring each compressor's individual current and voltage ratios separately. This granular approach enables prompt detection of grid faults affecting specific compressors without waiting for broader grid-wide detection mechanisms, thereby improving both measurement precision and reducing detection time.
Solution Approach 2:
The control module continuously calculates and monitors the ratio of average current to average voltage as a preliminary indicator of grid faults at the individual compressor level. This ongoing preliminary detection enables immediate identification of grid issues before they propagate or cause damage, improving both detection accuracy and speed compared to existing methods.
Data Source
AI summary
A compressor monitoring system includes current and voltage monitors, current and voltage averaging modules, a control module, and a switch. The current monitor measures a current drawn by a motor of a compressor. The current averaging module generates first and second average current values based on the current measured by the current monitor. The voltage monitor measures a utility power voltage. The voltage averaging module generates first and second average voltage values based on the voltage measured by the voltage monitor. The control module selectively generates a fault signal when a first ratio is greater than a first predetermined threshold and a second ratio is less than a second predetermined threshold. The first ratio is based on the first and second average current values. The second ratio is based on the first and second average voltage values. The switch deactivates the motor when the fault signal is generated.