# Wireless Communication Technologies for Smart Grid Distribution Networks +
## 4 Previous Studies on Selecting Suitable Technologies for Power Line Monitoring  
Although the field of WNSs is currently highly developed, there are few works that address the issue of wireless link quality or the experimental performance of different WSN technologies at the Transmission and Distribution (T&D) level [13]. The most significant efforts in applying previous theoretical frameworks of WSNs to practical scenarios are summarized in this section. [PERSON] et al. [16] introduced a self-powered WSN for underground HV power lines. The authors addressed one of the challenges in developing WSNs for power lines and presented the design of a protocol and network. The main objective of this work involved measuring temperatures and currents in underground conductors, as well as monitoring and controlling the capacity of transmissions (overall ampacity). Wireless sensors were deployed due to the large gaps that the information must travel to reach the gateway. The second challenge of the project was the necessity of finding a way to encapsulate the data from the sensor to transmit them in a minimal number of packages. Each sensor node consisted of an XBee-PRO 802.15.4 module, including an MC9S08 GT60 MCU and an MC13193 RF chip. The backend server was connected to the last node through a GPRS module. The energy harvesting device was magnetic, but the sensor also incorporated a battery. The proposed protocol for communications was based on the Freescale Simple Media Access Controller (SMAC). The WSN used a 10 ms time slot for communication between two consecutive nodes, as well as Time Division Multiple Access (TDMA). The limit of transmission was 123 B, encapsulated according to the HDLC standard protocol, to be added to the 802.15.4 package. Each node's frame of data had a length of 12 B. To maintain accurate clock synchronization and minimize power consumption, the protocol was based on the IEEE 1588 standard. As network reliability was a concern, the protocol provided redundancy, where each node was required to communicate with at least two consecutive nodes. Under normal conditions and at a sampling rate of 10 s, the WSN achieved synchronization after 5 min; after 10 min, all odd nodes disconnected. The power consumption of the battery, in case the line was off, allowed for a duration of 2 weeks for each node. [PERSON] et al. [17] designed a sensor net for overhead transmission lines to transmit the local information of sensor modules peer-to-peer back to a master node, far away from local sensors, which is powered via a magnetic harvesting device clamped onto the power line. Digi's ZigBee-PRO RF module is used, implementing 802.15.4. It was noted that the protocol specifies Direct Sequence Spread Spectrum(DSSS) and Offset Quadrature Phase-Shift Keying (O-QPSK) to modulate the RF carrier, which helps enhance communication immunity to ambient noises, especially those with wide frequency bandwidth, such as impulse noises commonly observed in high-voltage power line environments. The topology is a cluster tree, along with a central coordinator RF module to provide synchronization services and end routers to connect to the higher subnet. It uses 128-bit encryption. The module is complemented with a TMS320F2812 DSP. The results show an outdoor range of 1.6 km, a data rate of 250 kbps, and a packet transmission rate of 50 packets per second (20 ms per packet), each containing 100 bytes of data. The device was tested on a power line conductor. It was shown to be autonomously powered by a primary-side current ranging from 100 to 1000 A. To test the communication performance, a host PC was used to continuously transmit a data stream (32 bytes/packet) to the module, and the communication performance was evaluated by receiving the same data stream looped back from the remote PLS module. For the communication performance, two criteria were evaluated: the Received Signal-Strength Indicator (RSSI) and the Percentage of Successful Reception (PSR).