Smart Grid substations rely on conventional Supervisory Control and Data ‎Acquisition (SCADA) systems ‎for remote supervision and control. However, these ‎systems are limited in the geographical area ‎they cover. Recently, the ‎Internet of ‎Things (IoT) has paved the way for connecting a vast number of devices to the ‎‎Internet, which would be effective and beneficial for power system automation ‎and ‎data acquisition. In this paper, an intelligent low-‎cost SCADA system based on ‎IoT for transmission line fault diagnosis is proposed. In the first ‎step of the ‎proposed scheme, voltage and current signals at the relaying point are preprocessed ‎‎and analyzed using Discrete Cosine Transform (DCT). Next, signal energy ‎components are ‎extracted and sent to a Boosted Decision Tree (BSDT), a reliable ‎and fast ensemble classifier, to identify fault type and, accordingly, a specific ANN ‎is ‎activated to estimate fault location. The diagnosis data is sent to a ‎microcontroller to be ‎displayed, trip the load circuit, and allow communication with ‎Cloud ThingSpeak platform via ‎the ESP8266 wi-fi communication module which ‎makes data available anywhere all over the world. ‎The approach is applied on a ‎real-world HV transmission line, located between Samalut and ‎Cairo, Egypt, where ‎more than 16000 faults cases are well tested. The results show the ‎reliability, ‎validity, and effectiveness of the proposed approach. ‎