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In the power grid, efficient coordination among electricity generation, transmission, distribution and consumption processes call for integration of the advances in Information and Communication Technologies (ICT) to the physical components of the grid. The need for coordination and control becomes even more pronounced when the additional loads of the Plug-In Hybrid Electrical Vehicles (PHEVs) are considered. PHEVs are anticipated to be widely adopted in the following years, and this will increase the load on the power grid since the batteries of the PHEVs will be charged mostly from the grid supplied power. In this case, avoiding mismatch between generation and consumption is one aspect of the problem, whereas to avoid overloading the distribution system components, e.g. transformers, is another equally important challenge. In this paper, we consider an architecture where the status of the grid is monitored by the utility and translated into an amount of provisioned energy for each distribution system serviced by a substation. The substation employs an admission control mechanism for the PHEV charge demands based on the provisioned energy amount. We provide the theoretical analysis of this admission control scheme by calculating the blocking probability of the PHEV demands. We also propose a mechanism to reduce the load without increasing the blocking probability. We introduce an activity factor in the model and show that it can be used to reduce the load. We show by theoretical analysis and simulations that our PHEV admission control mechanism decreases the overall load in the system, and hence increases the resilience of the smart grid. Meanwhile, we show that load reduction can be implemented without increasing the blocking probability, thus customer satisfaction is not degraded.