From Regulation to Grid: Why Every ≥1 MW Power Plant in Spain Requires an IEC 60870–5‑104 RTU

Jul 31, 2026

In Spain, any pow­er gen­er­a­tion facil­i­ty of ≥1 MW must inte­grate an RTU or Gate­way run­ning the IEC 60870–5‑104 pro­to­col to inject and trade ener­gy on the grid.

Grid reg­u­la­tions require real-time teleme­try trans­mis­sion and active remote con­trol capa­bil­i­ty by the Trans­mis­sion Sys­tem Oper­a­tor (Red Eléc­tri­ca de España — REE). Because field equip­ment (invert­ers, relays, meters) com­mu­ni­cates via dis­parate local pro­to­cols such as Mod­bus or DLMS, a cyber­se­cure RTU/Gateway serves as the crit­i­cal bridge that trans­lates local metrol­o­gy into the IEC-104 stan­dard required by Con­trol Centers.

What Is the IEC 60870–5‑104 Protocol and Why Is It the Grid Standard?

The IEC 60870–5‑104 (IEC-104) pro­to­col is part of the inter­na­tion­al stan­dards devel­oped by the Inter­na­tion­al Elec­trotech­ni­cal Com­mis­sion for pow­er sys­tem automa­tion and tele­con­trol (Grid Automation).

Unlike lega­cy indus­tri­al pro­to­cols, IEC-104 pro­vides four crit­i­cal oper­a­tional advantages:

  • Native TCP/IP Com­mu­ni­ca­tion: Designed for long-dis­tance data trans­mis­sion over Eth­er­net, fiber optics, and 4G/5G links using secure VPN tunnels.
  • Event-Dri­ven Trans­mis­sion and High-Pre­ci­sion Time­stamp­ing: Instead of con­tin­u­ous polling that sat­u­rates band­width, the pro­to­col reports state changes or anom­alies at the mil­lisec­ond lev­el, enabling pre­cise post-fault foren­sic analysis.
  • Bidi­rec­tion­al Tele­con­trol via Select Before Oper­ate (SBO): A dual-con­fir­ma­tion safe­ty mech­a­nism that val­i­dates a com­mand before exe­cu­tion, pre­vent­ing unin­tend­ed switch­ing dur­ing remote pow­er set­point adjustments.
  • IEC 62351 Cyber­se­cu­ri­ty Com­pli­ance: Native inte­gra­tion of encryp­tion and authen­ti­ca­tion lay­ers nec­es­sary to pro­tect crit­i­cal ener­gy infrastructure.

 

The Regulatory Framework: From Legislation to Technical Specifications

The require­ment for the IEC-104 pro­to­col in medi­um and util­i­ty-scale pow­er plants is not a dis­cre­tionary deci­sion by the Con­trol Cen­ter, but the direct result of a strict reg­u­la­to­ry chain in Spain:

  • Roy­al Decree (RD) 413/2014 (Art. 7.c): Estab­lish­es the legal oblig­a­tion to send real-time teleme­try for all pow­er gen­er­a­tion facil­i­ties ≥1 MW.
  • Annex II of RD 413/2014: Man­dates that inte­gra­tion must com­ply with the tech­ni­cal spec­i­fi­ca­tions and Oper­at­ing Pro­ce­dures of the elec­tri­cal system.
  • Oper­at­ing Pro­ce­dure 9.2 (P.O. 9.2): Defines the scope of data exchange with REE and reg­u­lates the require­ments for bind­ing to an Autho­rized Gen­er­a­tion and Dis­tri­b­u­tion Con­trol Cen­ter (CCGD).
  • REE Tech­ni­cal Spec­i­fi­ca­tions: Estab­lish the IEC 60870–5‑104 pro­to­col as the offi­cial stan­dard for data exchange and del­e­gat­ed dis­patch.

 

Practical Nuance for the 1 MW to 5 MW Range:

His­tor­i­cal­ly, facil­i­ties between 1 MW and 5 MW oper­at­ed with cer­tain flex­i­bil­i­ty regard­ing pas­sive teleme­try report­ing. How­ev­er, the oper­a­tional evo­lu­tion of P.O. 9.2 and the need for grid sta­bil­i­ty dur­ing over­sup­ply events or volt­age sags have uni­fied cri­te­ria: today, the required tech­ni­cal solu­tion for grid mar­ket par­tic­i­pa­tion demands active reg­u­la­tion via del­e­gat­ed dis­patch under the IEC-104 protocol.

 

What Does the System Operator Protect Through This Requirement?

REE’s man­date address­es fun­da­men­tal physics and indus­tri­al safe­ty concerns:

Over fre­quen­cy Con­trol (Black­out Pre­ven­tion): When renew­able gen­er­a­tion sig­nif­i­cant­ly exceeds demand, the grid fre­quen­cy (50 Hz) ris­es. With­out remote cur­tail­ment capa­bil­i­ty, the sys­tem risks cas­cad­ing outages.

Local Tech­ni­cal Con­straint Man­age­ment: Detect­ing capac­i­ty bot­tle­necks on spe­cif­ic dis­tri­b­u­tion lines and apply­ing selec­tive pow­er reduc­tions before pro­tec­tion trips occur.

Volt­age Sta­bil­i­ty (Reac­tive Pow­er Con­trol): Man­ag­ing reac­tive pow­er injec­tion or absorp­tion at the Point of Inter­con­nec­tion (POI) to main­tain volt­age with­in reg­u­la­to­ry limits.

 

On-Site Challenge: Heterogeneous Field Protocols vs. Grid Standards

The pri­ma­ry chal­lenge for engi­neer­ing firms and devel­op­ers lies in the coex­is­tence of mul­ti­ple indus­tri­al com­mu­ni­ca­tion pro­to­cols with­in the same con­trol cabinet:

 

The Technical Solution: Cybersecure Multiprotocol RTUs and Gateways

To bridge the gap between plant-lev­el diver­si­ty and grid-lev­el com­pli­ance, the facil­i­ty requires a Remote Ter­mi­nal Unit (RTU) or Com­mu­ni­ca­tions Gateway.

This device per­forms three simul­ta­ne­ous tasks:

1. Local Mul­ti­pro­to­col Data Inges­tion: Main­tains active ser­i­al or Eth­er­net links with field equipment.

2. Data Nor­mal­iza­tion: Maps local reg­is­ter address­es to the mem­o­ry struc­ture required by P.O. 9.2.

3. IEC 60870–5‑104 Serv­er: Main­tains an encrypt­ed VPN tun­nel to the Con­trol Cen­ter, trans­mit­ting teleme­try and exe­cut­ing con­trol set­points with­in milliseconds.

 

 

Simplified Integration with iGrid T&D’s iGW Series

At iGrid T&D, we design and man­u­fac­ture spe­cial­ized solu­tions for grid automa­tion and remote man­age­ment. Our iGWs and iRTUs stream­line the inte­gra­tion of renew­able assets under the high­est mar­ket standards:

• Native Mul­ti­pro­to­col Con­ver­sion: Con­cen­trates data from Mod­bus, IEC 61850, DLMS, or DNP3 direct­ly into IEC 60870–5‑104 with­out extra controllers.

• DIN-Rail Indus­tri­al Hard­ware: Com­pact, low-pow­er hard­ware fea­tur­ing high elec­tro­mag­net­ic com­pat­i­bil­i­ty (EMC) immu­ni­ty and extend­ed oper­at­ing tem­per­a­ture ranges.

• Cyber­se­cu­ri­ty by Design: Engi­neered for crit­i­cal IP net­works using IPsec/OpenVPN tun­nels and secu­ri­ty pro­files aligned with IEC 62351.

 

Frequently Asked Questions (FAQ) on IEC-104 Compliance in Renewable Plants

Can a 1.5 MW solar plant send Mod­bus teleme­try direct­ly to a Con­trol Cen­ter?
No. The Sys­tem Oper­a­tor (REE) and Autho­rized Con­trol Cen­ters do not accept direct Mod­bus con­nec­tions for del­e­gat­ed dis­patch. Exter­nal com­mu­ni­ca­tions must strict­ly use the IEC 60870–5‑104 protocol.

What hap­pens if the RTU los­es its IEC-104 link to the Con­trol Cen­ter?
A pro­longed com­mu­ni­ca­tion loss can trig­ger auto­mat­ed cur­tail­ment orders or tem­po­rary grid dis­con­nec­tion under P.O. 9.2 rules. This is why deploy­able Gate­ways and RTUs must be cer­ti­fied for harsh grid envi­ron­ments. To elim­i­nate sin­gle points of fail­ure, iGrid T&D’s iGW and iRTU series include built-in hard­ware redundancy—such as dual-hom­ing IEC-104 chan­nels, redun­dant Eth­er­net ports, and cel­lu­lar failover (4G/5G)—ensuring con­tin­u­ous teleme­try and pre­vent­ing unex­pect­ed downtime.

Can the same RTU send data to REE and the own­er’s Cloud plat­form simul­ta­ne­ous­ly?
Yes. Cer­ti­fied Gate­ways like the iGW series sup­port inde­pen­dent, mul­ti-des­ti­na­tion data pro­cess­ing. They trans­mit real-time teleme­try to the Con­trol Cen­ter via IEC-104 for reg­u­la­to­ry com­pli­ance, while con­cur­rent­ly stream­ing oper­a­tional met­rics to Cloud mon­i­tor­ing plat­forms using IIoT pro­to­cols like MQTT or HTTP REST APIs with­out affect­ing grid communications

 

The Cost of Non-Compliance: Operational & Financial Risks

In today’s evolv­ing pow­er sys­tem, com­pli­ance with P.O. 9.2 reg­u­la­tions and the IEC 60870–5‑104 stan­dard is not an option­al feature—it is a strict legal and tech­ni­cal require­ment for grid operation.

Oper­at­ing a pow­er plant with­out ded­i­cat­ed tele­con­trol hard­ware and reli­able pro­to­col trans­la­tion intro­duces crit­i­cal vulnerabilities:

  • Tem­po­rary or Per­ma­nent Grid Dis­con­nec­tion: The Trans­mis­sion Sys­tem Oper­a­tor (REE) can restrict or sus­pend mar­ket access if active real-time observ­abil­i­ty and remote reg­u­la­tion are not guaranteed.
  • Rev­enue Loss from Forced Cur­tail­ment: Fail­ing to respond with­in mil­lisec­onds to remote active or reac­tive pow­er set­points leads to unbilled gen­er­a­tion hours and severe mar­ket penalties.
  • Cyber­se­cu­ri­ty Breach­es and Sys­tem Insta­bil­i­ty: Rely­ing on gener­ic con­vert­ers or soft­ware patch­es expos­es crit­i­cal infra­struc­ture to cyber threats and unex­pect­ed com­mu­ni­ca­tion outages.

Equip­ping your gen­er­a­tion facil­i­ty with pur­pose-built RTUs and Gate­ways goes beyond ful­fill­ing a reg­u­la­to­ry mandate—it is the ulti­mate assur­ance to safe­guard plant avail­abil­i­ty, pro­tect your cap­i­tal assets, and guar­an­tee long-term project profitability.

 

Need to Adapt Your Gen­er­a­tion Asset to P.O. 9.2 Require­ments?
We spe­cial­ize in pow­er grid automa­tion and tele­con­trol solutions.

👉 Con­sult with our engi­neer­ing team at iGrid T&D to eval­u­ate the opti­mal com­mu­ni­ca­tions archi­tec­ture for your project [email protected].