What is IEC 61850?

The IEC 61850 stan­dard was a response to the grow­ing need for high­er and deep­er lev­els of con­trol and automa­tion in elec­tri­cal grids. With steadi­ly increas­ing num­bers of devices, device types and data points, fur­ther accel­er­at­ed by dig­i­ti­za­tion, as well as the inte­gra­tion of new, often geo­graph­i­cal­ly dis­trib­uted and het­erege­nous, gen­er­a­tion sources, it became evi­dent that future demands could not be met with the tech­no­log­i­cal lim­its of ser­i­al pro­to­cols like Modbus. 

In order to guar­an­tee inter­op­er­abil­i­ty in the face of rapid tech­no­log­i­cal devel­op­ment and prod­uct inno­va­tion in the indus­try, the IEC 61850 stan­dard not only defines var­i­ous com­mu­ni­ca­tion pro­to­cols and inter­faces, but also pro­vides spec­i­fi­ca­tions con­cern­ing the sub­sta­tion mod­el­ling, con­fig­u­ra­tion lan­guage and data mod­els. For this rea­son, IEC 61850 is com­mon­ly referred to as “not just a pro­to­col” and often called a data mod­el or frame­work instead. 

The scope of the stan­dard allows to map the stan­dard­ized data mod­els and ser­vices onto server­al com­mu­ni­ca­tion pro­to­cols and thus trans­fer the data via Eth­er­net using dif­fer­ent pro­to­cols for dif­fer­ent require­ments and appli­ca­tions, as for exam­ple TCP/IP-based pro­to­cols for clients/server com­mu­ni­ca­tions. For this rea­son, despite its ini­tial focus on sub­sta­tion automa­tion, the flex­i­bil­i­ty of IEC 61850 has spread its use to oth­er appli­ca­tions, such as the inte­gra­tion of dis­trib­uted ener­gy resources (DERs) into the pow­er sys­tem or the com­mu­ni­ca­tion between intel­li­gent devices in Build­ing Man­age­ment Sys­tems (BMS).

The IEC 61850 stan­dard dis­tin­guish­es itself through the fol­low­ing elements:

Abstract Com­mu­ni­ca­tion Ser­vice Inter­face (ACSI)
The ACSI (defined in IEC 61850–7‑2) describes the func­tions and ser­vices for the inter­ac­tion between IEDs in the sys­tem. Exam­ples of IEC 61850 ser­vices include the trans­mis­sion of files, read­ing of data or assig­ni­tion of val­ues. The ACSI can be mapped onto var­i­ous pro­to­cols, includ­ing MMS or web services.

Sys­tem Design and Struc­ture
The func­tions of the IEC 61850 stan­dard are the often-heard log­i­cal nodes, which can sim­ply con­tain device descrip­tions but usu­al­ly rep­re­sent a real phys­i­cal device like switch­es, sen­sors or IEDs, and its entire range of functionalies.

IEC 61850 Pro­to­col Suite
The IEC 61850 stan­dard defines sev­er­al dif­fer­ent pro­to­cols for dif­fer­ent pur­pos­es in sub­sta­tions and oth­er facilities/ util­i­ties.
The stan­dard defines the low-lev­el (process bus) client/server based GOOSE/GSSE (Gener­ic Object Ori­ent­ed Sub­sta­tion Events) pro­to­col to trans­mit event data across net­works at very high speeds. This enables to new pos­si­bil­i­ties for advanced sub­sta­tion automa­tion and pro­tec­tion func­tions and schemes.

It also defines the more com­plex MMS (man­u­fac­tur­ing mes­sage spec­i­fi­ca­tion) pro­to­col for com­mu­ni­ca­tions between servers and clients. It pro­vides a set of func­tions that allows the client to obtain the data mod­el of the serv­er, read or mod­i­fy indi­vid­ual val­ues, or even delete entries as well as to trans­fer files.

The last two pro­to­cols dis­played on the chart com­prise the Sam­pled Val­ues (SV) pro­to­col for the trans­mis­sion of dig­i­tized instan­ta­neous val­ues of pow­er sys­tem quan­ti­ties, main­ly pri­ma­ry cur­rents and volt­ages and time syn­chro­niza­tion pro­to­cols such as SNTP over UDP/IP.