The described case study concerns application of wireless sensor networks to the smart control of power supply substations. The solution proposed for metering is based on the modular principle and has been tested in the intersystem communication paradigm using selectable interface modules (IEEE 802.3, ISM radio interface, GSM/GPRS). The solution modularity gives 7 % savings of maintenance costs.The developed solution can be applied to the control of different critical infrastructure networks using adapted modules. The proposed smart metering is suitable for outdoor installation, indoor industrial installations, operation under electromagnetic pollution, temperature and humidity impact. The results of tests have shown a good electromagnetic compatibility of the prototype meter with other electronic devices. The metering procedure is exemplified by operation of a testing company’s workers under harsh environmental conditions.