T101 or IEC 60870-5-101 (IEC101) is an international standard prepared by TC57 for power system monitoring, control & associated communications.
This is compatible with IEC 60870-5-1 to IEC 60870-5-5 standards and uses standard asynchronous serial tele-control channel interface between DTE and DCE. The standard is suitable for multiple configurations like point-to-point, star, muti-dropped etc.
60870-5-101 or T101 have many features such as the following:
Supports unbalanced (master initiated message) & balanced (master/slave initiated message) modes of data transfer.
Link address and ASDU addresses are provided for classifying the end station and different sectors under the same.
Data is classified into different information objects and each information object is provided with a specific address.
Facility to classify the data into high priority (class-1) and low priority (class-2) and transfer the same using separate mechanisms.
Possibility of classifying the data into different groups (1-16) to get the data according to the group by issuing specific group interrogation commands from the master & obtaining data under all the groups by issuing a general interrogation.
Cyclic & Spontaneous data updating schemes are provided.
Facility for time synchronization
Schemes for transfer of files
Types supported by T101
Distributed Control System components are usually included in SCADA. IEDs, RTUs or PLCs are also commonly used; they are capable of autonomously executing simple logic processes without a master computer controlling it.
A functional block programming language, IEC 61131-3, is frequently used to create programs which run on these RTUs and PLCs. This allows SCADA system engineers to perform both the design and implementation of a program to be executed on an RTU or PLC.
From 1998, major PLC manufacturers have offered integrated HMI/SCADA systems, many use open and non-proprietary communications protocols.
Many third-party HMI/SCADA packages, offering built-in compatibility with most major PLCs, have also entered the market, allowing mechanical engineers, electrical engineers and technicians to configure HMIs themselves.