Insulation Resistance Monitoring in an Electrical Network with an Isolated Neutral: Data Processing in a Device with Impulse Test Voltage

• Published in: Russian electrical engineering 2023, Vol.94 (1), p.13-18
• Main Authors: Malafeev, S. I., Malafeev, S. S.
• Format: Article
• Language: English
• Subjects: Algorithms; Alternating current; Circuits; Control equipment; Data processing; Electric equipment; Electric potential; Electrical installations; Electrical networks; Electrical resistance; Engineering; Error analysis; Insulation; Leakage current; Machines; Manufacturing; Mining machinery; Processes; Signal monitoring; Sliding; Thyristors; Voltage
• ISSN: 1068-3712; 1934-8010
• DOI: 10.3103/S1068371223010078

An algorithm for processing insulation resistance measurement data in an electrical network with an isolated neutral is proposed. The features of continuous monitoring of insulation resistance in electrical networks with semiconductor energy converters are considered. A description of a technical solution that meets the requirements of regulatory documents for mining equipment and provides an increase in the speed of the insulation resistance control procedure and protection of electrical equipment is given. The device-operation algorithm is based on the use of a periodic test signal. The test voltage source generates bipolar pulses of a special shape into an AC network. During each period of the test signal, two procedures are performed: charging the capacitance of the electrical network and directly measuring the leakage current in the steady-state mode for the measuring current. Based on the results of leakage current measurements at positive and negative test voltage values, the insulation resistance that is used in the protective disconnection circuit is determined. The decrease in the measurement error is provided by interference compensation during algebraic summation of signals proportional to the leakage current, but is shifted in time by half the period of the test signal. The insulation resistance is calculated by averaging the calculated insulation resistance value over a sliding interval equal to the voltage period of the monitored network. The signal averaged over a sliding interval is continuous; therefore, the measurement result is also formed continuously. The delay in determining when the insulation resistance drops is approximately half the period of the test voltage. Continuous monitoring of insulation resistance in dual-current electrical installations is the basis for safe operation of personnel and equipment. Results of modeling the operation of the insulation resistance control device in an electrical network with thyristor rectifiers are presented.