A temperature sensor 31A for bolted connections 8A, includes a thermally conductive housing 30 having a skirt portion 62 with an opening shaped to fit on a portion of a bolted connection of a bus bar. The skirt portion of the housing is configured to be in thermal contact with the bolted connection when the skirt portion is fitted on the bolted connection of the bus bar. The temperature sensor further includes a temperature transducer 70 in thermal contact with the housing. The temperature transducer is configured to sense a temperature of the housing which relates to a temperature of the bolted connection and to output signals to a data collector 1 via wireless or wireline communication.