Automated Monitoring of High-Resistance Connections in the Electrical Distribution System of Industrial Facilities

High-resistance(R) connections due to poor contacts in the electrical distribution system can cause failures due to overheating, reduce efficiency, and pose safety risks in the industrial facility. The methods currently available for detection of high-R connections such as infrared thermography, resistance or voltage unbalance tests are inconvenient since they are off-line or walk-around type tests that do not provide continuous monitoring. In this paper, an automated technique for detecting high-R connections based on existing voltage and current measurements is proposed. The contact resistance, R_HR, of the poor contact is estimated based on the voltage and current variation under startup and/or shutdown of the load for monitoring problems located upstream from the point of voltage measurement. For downstream problems, R_HR is estimated based on the negative sequence current under steady state operation of the load. An experimental study on a 10hp induction motor load performed under simulated high-R circuit conditions verifies that poor contacts that exist upstream and downstream can be reliably detected without additional measurements. It is shown that the proposed technique can provide automated monitoring of the existence, location, and severity of high-R contacts for reliable, efficient, and safe operation of the industrial facility.