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Substation Automation and Communication Protocols Including IEC 61850
Published in J.C. Das, Power Systems Handbook: Power Systems Protective Relaying, 2017
Most automation systems rely on point-to-multipoint connections for the IEDs. The IEDs that share a common protocol often support a party line communication pathway, where they share the channel. The SA controller uses it as a master–slave communication bus, where an SA controller controls the traffic. All devices on the channel must be addressable so that only one device communicates at one time. RS-485 is the most common point-to-multipoint bus. It may use a shielded copper pair, terminated at each end of the bus with a matching resistor equal to the characteristic impedance of the bus cable. RS-485 can support 32 devices on the channel, maximum channel length being typically 4000′. The longer the bus, the slower it runs. The maximum speed is 1.0 Mbps, though, practically, it runs much slower with a speed of 19.2 kbps. RS-485 bus is linear, and stubs will cause reflections. The TS-485 devices are wired in a daisy chain.
Mobility Solutions for Energy and Utilities
Published in Jithesh Sathyan, Anoop Narayanan, Navin Narayan, K V Shibu, A Comprehensive Guide to Enterprise Mobility, 2016
Jithesh Sathyan, Anoop Narayanan, Navin Narayan, K V Shibu
As the application requirement explicitly calls for off-line data capture, a thick client solution with local data storage is the ideal solution for implementing this requirement. The locally stored data can later be synchronized with the central database, when network connection is available. GPRS or 3G network is used for data communication with the central station. Figure 16.5 illustrates the end-to-end system architecture. The RS-485 interface supports multidrop communication, and up to 32 meters can be connected to a single RS-485 bus. Each customer's meter is assigned a unique ID, and meters in an apartment complex are wired to a single RS-485 bus forming a meter cluster. Short-range wireless technologies, such as Bluetooth, ISM band RF, etc., can be used for building a wireless interface between the RS-485 bus and the mobile device for meter recording. A custom- built or off-the-shelf interface converter module based on any one of the above- mentioned wireless technologies can be used for interface conversion at the RS-485 bus to which the meters are connected. In the current design, Bluetooth technology, which is the cheapest among the available short-range wireless technologies, is selected for building the automatic meter reading wireless interface. Any end device that supports Bluetooth communication interface and device programma- bility (such as smartphones, PDAs, laptops, etc.) can be used for collecting the meter reading programmatically (Figure 16.6).
PLC terms and definitions
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
An open-ended, i.e., free from royalties, communication protocol developed by Modicon systems for transmitting PLC information over serial lines to up to 247 devices. Modbus uses RS485 transmission protocol and cables. The device requesting information is the master, and the device supplying the information is the slave. Information transmission is initiated by the master, and the information is broadcast serially through each device; however, only the addressed device will act on the information. Although the Modbus protocol was developed in 1979, developed versions of the communication method are so robust over long distances and easy to use that Modbus/RS485 is very often used in modern PLC communications. Some other alternatives are Profibus and Ethernet/IP.
Online condition monitoring system for rotating machine elements using edge computing
Published in Australian Journal of Mechanical Engineering, 2023
N. D. Pagar, S. S. Gawde, S. B. Sanap
Vibration measurement is done via a piezoelectric sensor (accelerometer), as they are beneficial in detecting the large forces having relatively small displacement. It has good frequency response and easier to handle because of its compact size. A PZEM004T is a single-phase voltage, current and power sensor used for current measurement as it also contributes to the decision while condition monitoring. The sensing component is a precise AC current transformer coil with an output of 100A/100 mA. Temperature sensor (MAX6675) is used for temperature measurement because any fault that initiates cause friction, which affects the temperature of the equipment. All three sensors are interfaced with the STM32F4 microcontroller board via RS-485 cable. STM32F4 is 32-bit ARM Cortex M4 that takes fewer instruction cycles to execute a function due to its wider data bus (fetch, decode, and execute instructions). This allows to make a FFT with a few simple steps. STM32 series provide instructions for signal processing. It is a high-performance microcontroller with low cost and power consumption. The sensors are connected to the microcontroller circuit using RS-485 cable. It is a differential cable, so the noise-free data transferred through it is not affected by the ground voltage. RS-485 can handle up to 32 devices at once and can travel up to 1200 m, which single-ended cables cannot.