In electrical industry, companies are looking for ways to reduce costs while improving and maintaining reliability of equipment in repair and maintenance category. In this paper condition-based maintenance model in parallel electricity distribution network is studied. A single control limit is determined for all components to minimize a total expected cost during planning horizon subject to reliability constraint of the whole parallel system. Considering the covariate values on the component’s deterioration, proportional hazard model is adopted and we provide a closed-form of analytical solution for the reliability of tampered failure rate load-sharing system. It means failure of one component will affect the failure rate of other components. In this research between both inspection points, if component fails, a minimal repair action must be performed, so we have two cost types for each component; the cost of minimal repair and the cost of replacement. At each inspection point, the failure rate is measured and compared with the optimal control limit decided in the previous step. If it exceeds the control limit, the system must be replaced and the replacement cost is considered, but if it does not exceed the control limit, it will continue to work until the next inspection point without performing any maintenance. Inspection points are performed based on amount of failure age-dependent and the value of covariate variables in time intervals. Modeling a multi-component system is challenging due to the interdependence of the failure behavior among the components and determining the optimal control limit for preventive replacement. Although different research works have been done in the literature on condition-based maintenance models, there is a research gap in considering the failure dependency of components. Most of them consider independent failure between the components or the degree of failure dependency is precisely specified.  It can cause inefficient analysis and incorrect assessment of the situation.
The proposed nonlinear programming model has been evaluated with MATLAB software. This plan helps the technicians to control the reliability of the system and the operation of the components at a higher level by considering the failure dependency between the components during the inspection periods. Furthermore, they are informed about failures earlier, before incurring the replacement costs. The results show that the network reliability of the proposed model has a better performance than the basic model. At the end, in order to confirm the effectiveness of the approach, a case study of the electrical panel is examined.