Assessment of Low-Voltage Motor Ride Through: A Comparison of Solutions for Critical Processes in the Oil and Gas Industry

Abstract

Voltage sags initiated by utility transmission system faults cause nuisance trips of low-voltage (LV) motors, due to contactors dropping off as a result of the undervoltage condition. Since voltage disturbances by utility systems cannot be prevented, it is essential to mitigate the impact of LV motors trips on critical process systems in the oil and gas industry, such as lubrication and shaft-sealing systems. To address this challenge, there is a tendency in the industry to modify standard LV motor control schemes to hold contactors closed during voltage sags to maintain process continuity. This approach will be evaluated against restarting schemes and sag correction devices in terms of their impact on motor performance and motor controller design. A simulation model was developed using Power Systems CAD to assess motor performance and subsequent current and torque profiles associated with various ride-through solutions. The reliability and safety aspects of modifications associated with different ride-through solutions were evaluated and benchmarked against relevant international standards and industrial practices.