Spanish Power Outage - The Official Report

[Crossy]

 

 

https://euroweeklynews.com/2025/06/18/spains-blackout-cause-finally-revealed/

 

 

The report itself https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_ 28A_SpanishPeninsularElectricalSystem_18june25.pdf

From here https://www.ree.es/en/operation

 

Interestingly: - 

"The incident was NOT caused by a lack of system inertia. Rather, it was triggered by a voltage issue and the cascading disconnection of renewable generation plants, as previously indicated. Higher inertia would have only resulted in a slightly slower frequency decline. However, due to the massive generation loss caused by voltage instability, the system would still have been unrecoverable."

 

The TL;DR sequence of events is summarised in the report as follows: -

 

(Note: The generation that must comply with P.O. 7.4 regulates, in a mandatory way, voltage dynamically and independently of the active power they are generating, thus it ensures stable voltages in the network.

and

RCW = Renewable, Cogeneration, and Waste)

1. Forced oscillation at 0.6 Hz, possibly originating in a photovoltaic power plant in the province of Badajoz,triggers system-altering protocolized actions. Shunt reactors are operated, lines are coupled due to oscillations, and schedules are modified. (N-1)

2. Natural oscillation at 0.2 Hz triggers further system-altering protocolized actions. Shunt reactors are operated, lines are coupled due to oscillations, and schedules are adjusted. (N-2).

3. Generation under P.O. 7.4 does not absorb the required reactive power. (N-3).

4. Variations in RCW generation during active power regulation affect voltage control and many of them don't fulfil their obligations. (N-4).

5. The conventional generation requested after the oscillations was not connected.

6. Generation loss in distribution: P < 1 MW and self-consumption of 435 MW before 12:32:57 (N-5).

7. Inappropriate tripping of a generation transformer in Granada (N-6).

8. Inappropriate tripping of solar thermal generation (Badajoz) and tripping of photovoltaic (Badajoz) withoutpoint-of-interconnection data from transmission network (N-7).

9. Inappropriate tripping of a photovoltaic power plant connected also in the province of Badajoz but in a different transmission substation (N-8).

10. Tripping of three wind farms (Segovia) without point-of-interconnection data from transmission network.

11. Tripping of one wind farm and a PV plant located at the province of Huelva, without point-of-interconnection data from transmission network.

12. Inappropriate tripping of photovoltaic power plant in Seville (N-9).

13. Inappropriate tripping a PV generation located in the province of Cáceres (N-10).

14. Tripping of PV generation connected to a 220 kV substation located in the province of Badajoz, withoutpoint-of-interconnection data from transmission network.

15. Tripping of one CCGT unit located at Valencia (N-11).

16. Load shedding of pumping units and loads due to underfrequency results in increased system voltage.

17. The HVDC link operating in constant power mode continues exporting 1,000 MW to France.

18. Tripping of Nuclear Power Plant. (N-12)

 

 

[Muhendis]

There's a whole load of technical double talk in there which explains in grandiose detail what only experts can understand. 

Anything to keep the politicians out.

I strikes me that there should be an independent frequency source to control national grid frequency nationwide rather than relying on generator frequencies pulling each other into line.

Each generator has to be phase locked to this national frequency.

[johng]

In other words  the "green energy"  isn't reliable  and we should keep

the coal, oil and gas  which is.  Nuclear  as a last resort  as it is not very clean or cheap.

[johng]

Apparently UK also came close to grid shutdown this January for the same stupid reasons..I mean come on North sea oil and gas..its a no brainer..but instead they will buy in energy from France who also have their own problems.

[lom]

3 hours ago, johng said:

In other words  the "green energy"  isn't reliable  and we should keep

the coal, oil and gas  which is.  Nuclear  as a last resort  as it is not very clean or cheap.

 

I guess you didn't understand this:

 

On 6/19/2025 at 7:37 AM, Crossy said:

"The incident was NOT caused by a lack of system inertia. Rather, it was triggered by a voltage issue and the cascading disconnection of renewable generation plants, as previously indicated. Higher inertia would have only resulted in a slightly slower frequency decline. However, due to the massive generation loss caused by voltage instability, the system would still have been unrecoverable."

 

[johng]

2 minutes ago, lom said:

guess you didn't understand this:

What I understand is that a national power grid needs stability and that solar and wind power source's are not stable.

[lom]

3 hours ago, Muhendis said:

I strikes me that there should be an independent frequency source to control national grid frequency nationwide rather than relying on generator frequencies pulling each other into line.

Each generator has to be phase locked to this national frequency.

 

It was not a grid frequency problem, it was a problem with the frequency of grid reconfiguration. They occurred to fast, were to many  to many in a short time period making the grid voltage going quickly up and down (oscillating).

They just had a bad algorithm  for the automatic grid reconfiguration.

[novacova]

On 6/19/2025 at 7:37 AM, Crossy said:

 

 

https://euroweeklynews.com/2025/06/18/spains-blackout-cause-finally-revealed/

 

 

The report itself https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_ 28A_SpanishPeninsularElectricalSystem_18june25.pdf

From here https://www.ree.es/en/operation

 

Interestingly: - 

"The incident was NOT caused by a lack of system inertia. Rather, it was triggered by a voltage issue and the cascading disconnection of renewable generation plants, as previously indicated. Higher inertia would have only resulted in a slightly slower frequency decline. However, due to the massive generation loss caused by voltage instability, the system would still have been unrecoverable."

 

The TL;DR sequence of events is summarised in the report as follows: -

 

(Note: The generation that must comply with P.O. 7.4 regulates, in a mandatory way, voltage dynamically and independently of the active power they are generating, thus it ensures stable voltages in the network.

and

RCW = Renewable, Cogeneration, and Waste)

1. Forced oscillation at 0.6 Hz, possibly originating in a photovoltaic power plant in the province of Badajoz,triggers system-altering protocolized actions. Shunt reactors are operated, lines are coupled due to oscillations, and schedules are modified. (N-1)

2. Natural oscillation at 0.2 Hz triggers further system-altering protocolized actions. Shunt reactors are operated, lines are coupled due to oscillations, and schedules are adjusted. (N-2).

3. Generation under P.O. 7.4 does not absorb the required reactive power. (N-3).

4. Variations in RCW generation during active power regulation affect voltage control and many of them don't fulfil their obligations. (N-4).

5. The conventional generation requested after the oscillations was not connected.

6. Generation loss in distribution: P < 1 MW and self-consumption of 435 MW before 12:32:57 (N-5).

7. Inappropriate tripping of a generation transformer in Granada (N-6).

8. Inappropriate tripping of solar thermal generation (Badajoz) and tripping of photovoltaic (Badajoz) withoutpoint-of-interconnection data from transmission network (N-7).

9. Inappropriate tripping of a photovoltaic power plant connected also in the province of Badajoz but in a different transmission substation (N-8).

10. Tripping of three wind farms (Segovia) without point-of-interconnection data from transmission network.

11. Tripping of one wind farm and a PV plant located at the province of Huelva, without point-of-interconnection data from transmission network.

12. Inappropriate tripping of photovoltaic power plant in Seville (N-9).

13. Inappropriate tripping a PV generation located in the province of Cáceres (N-10).

14. Tripping of PV generation connected to a 220 kV substation located in the province of Badajoz, withoutpoint-of-interconnection data from transmission network.

15. Tripping of one CCGT unit located at Valencia (N-11).

16. Load shedding of pumping units and loads due to underfrequency results in increased system voltage.

17. The HVDC link operating in constant power mode continues exporting 1,000 MW to France.

18. Tripping of Nuclear Power Plant. (N-12)

 

 

The scenario describes a cascading series of power system disturbances with multiple events triggering protocolized actions and equipment tripping. A concise analysis of the events and their implications, based on power system dynamics and standard protocols:

1. **Forced Oscillation (0.6 Hz, Badajoz PV Plant, N-1)**: A photovoltaic (PV) power plant in Badajoz introduces a forced oscillation at 0.6 Hz, likely due to control system issues or equipment malfunction. This triggers system-altering actions, including operating shunt reactors to manage reactive power and coupling lines to stabilize the grid. Schedule modifications indicate adjustments to generation or load to dampen oscillations. This is classified as an N-1 contingency (single element failure).

2. **Natural Oscillation (0.2 Hz, N-2)**: A lower-frequency natural oscillation at 0.2 Hz emerges, possibly due to system-wide resonance or insufficient damping. Further shunt reactor operations and line coupling are enacted, with additional schedule adjustments. This N-2 event suggests a second contingency compounding the initial disturbance.

3. **Reactive Power Absorption Failure (P.O. 7.4, N-3)**: Generation units under operating condition P.O. 7.4 (likely a specific grid code or protocol) fail to absorb required reactive power, exacerbating voltage control issues. This indicates non-compliance or equipment limitations, further stressing the system.

4. **RCW Generation Issues (N-4)**: Renewable (likely wind or solar, RCW = Renewable Control Wind or similar) generation units exhibit variations during active power regulation, impacting voltage control. Many units fail to meet grid obligations, suggesting control or communication issues, adding to system instability.

5. **Conventional Generation Failure (N-5)**: Requested conventional generation (e.g., thermal or gas units) to mitigate oscillations does not come online, likely due to delays, outages, or scheduling errors, leaving the system vulnerable.

6. **Generation Loss in Distribution (N-5)**: A minor generation loss (P < 1 MW) and significant self-consumption (435 MW) before 12:32:57 indicate distributed energy resources (e.g., small-scale PV or loads) are not contributing as expected, further straining the grid.

7–14. **Multiple Inappropriate Trippings (N-6 to N-10, N-12 to N-14)**: A series of inappropriate trippings occur across various generation types and locations:
   - Granada generation transformer (N-6).
   - Solar thermal and PV plants in Badajoz (N-7, N-8, N-14).
   - PV plants in Seville and Cáceres (N-9, N-10).
   - Three wind farms in Segovia and one wind farm plus a PV plant in Huelva (N-10, N-11).
   Many lack point-of-interconnection data, indicating missing telemetry or communication with the transmission system operator (TSO), which complicates system monitoring and control.

15. **CCGT Unit Tripping (Valencia, N-11)**: A combined-cycle gas turbine (CCGT) unit trips, removing a significant dispatchable power source, further reducing system stability.

16. **Load Shedding and Voltage Increase**: Underfrequency triggers load shedding of pumping units and other loads, reducing demand but causing an unintended increase in system voltage due to reduced reactive power absorption.

17. **HVDC Link Operation**: The HVDC link to France continues exporting 1,000 MW in constant power mode, unaffected by local disturbances. This may exacerbate local instability by prioritizing export over domestic stabilization.

18. **Nuclear Power Plant Tripping (N-12)**: A nuclear plant trips, a critical event given its large capacity and baseload role, significantly worsening the system’s stability and capacity margin.

### System Implications
- **Oscillations**: The 0.6 Hz forced and 0.2 Hz natural oscillations suggest poorly damped inter-area or local modes, likely exacerbated by high renewable penetration and inadequate reactive power support.
- **Cascading Failures**: The sequence of events (N-1 to N-12) indicates a cascading failure, where initial disturbances (PV-related oscillations) trigger widespread equipment trippings due to protection settings, lack of coordination, or missing telemetry.
- **Reactive Power and Voltage Issues**: Repeated failure to manage reactive power (N-3, N-4, N-16) points to insufficient voltage control resources or non-compliance with grid codes.
- **Data Gaps**: Missing point-of-interconnection data for multiple tripped units (N-7, N-8, N-10, N-11, N-14) highlights a critical issue in TSO visibility, hindering real-time response.
- **Export Strain**: The HVDC link’s constant 1,000 MW export reduces local flexibility, potentially worsening underfrequency and stability issues.

### Recommended Actions
1. **Oscillation Damping**: Deploy power system stabilizers (PSS) on remaining conventional units and tune renewable controllers to dampen 0.2–0.6 Hz oscillations.
2. **Reactive Power Management**: Enforce grid code compliance for renewable units (P.O. 7.4) and activate additional reactive power resources (e.g., SVCs or synchronous condensers).
3. **Telemetry Improvement**: Address missing point-of-interconnection data by mandating real-time telemetry for all generators, especially renewables.
4. **Protection Coordination**: Review and adjust protection settings to prevent inappropriate trippings, particularly for PV, wind, and thermal units.
5. **Contingency Planning**: Enhance N-1 and N-2 contingency plans to prioritize local stability over exports, including dynamic HVDC control adjustments.
6. **Load and Generation Balance**: Restore conventional generation and adjust load shedding schemes to balance frequency and voltage.
7. **Post-Event Analysis**: Conduct a root cause analysis of the Badajoz PV oscillation and subsequent trippings to prevent recurrence.