Modeling the Reliability Characteristics of Contact Devices of Low-Voltage Grid

The paper presents a models elaboration and development algorithm for determining the distribution laws of the low-voltage contact devices' reliability index using the example of magnetic starters based on random samples during the device failures observations in operation. The modeling and calculation of the sample value indicators of the accumulated failure density in accordance with the operating time is presented, taking into account the randomly (using a random number generator) selected contact devices. As a calculations result, functional dependences of the low-voltage contact devices' performance parameters on the number of on-off cycles for Gaussian, lognormal and exponential distribution laws were obtained, as well as for the Weibull distribution with the selective correlation rate determination for each of the distribution laws. It was found that the highest correlation rate equal to 0.9107, which characterizes the Gaussian law, is the reliability index of the applied distribution law. As a result of the research, the Gaussian law accuracy for low-voltage contact devices was confirmed as in the case of magnetic starters for an operation period of 10-12 years. A simulation model is presented that allows calculating the low-voltage electrical contact devices' fixed failure rates from random samples.