Spanish developer Grenergy has asked Chile's National Electricity Coordinator to revoke the order limiting to 15% of installed capacity the output of eight of its small distributed generation plants (PMGD), all solar plants in central Chile. In a letter sent on 12 November, the company argued that those plants tripped as a consequence of the fault on Sunday 8 November and were not its cause, Electrominería reported on 13 November.
The request targets the measure the Coordinator ordered on 9 November, in force since the 10th, after some 520 MW of PMGD plants disconnected within seconds in the Metropolitan, Valparaíso and O'Higgins regions. The case tests how the protections of thousands of small plants connected to distribution networks are set.
View the data as a table
| Plants affected | 8 |
| Maximum output allowed | 15% |
| Fault duration | 75 ms |
| Anti-islanding setting | 18° |
Grenergy's eight PMGD plants under the cap
The plants affected are GR Alcón Solar, Santa Teresita, Chiloé, La Paz, Malloco, Argomedo, Lo Miguel and Javiera Carrera. According to the Coordinator's technical registry (Infotécnica), four are in the Metropolitan Region (Lampa, Pudahuel, Peñaflor and Buin), three in O'Higgins (Marchigüe, Quinta de Tilcoco and Rengo) and one in Maule (Curicó). Seven are listed under the GR Palmas de Cocalán group, whose name matches Palmas, Grenergy's cluster of solar PMGD plants in central Chile; Javiera Carrera is registered to GR Torres del Paine.
View the data as a table
| Plants | |
|---|---|
| Metropolitana | 4 · Lampa, Pudahuel, Peñaflor, Buin |
| O'Higgins | 3 · Marchigüe, Quinta de Tilcoco, Rengo |
| Maule | 1 · Curicó |
| GR Alcón Solar | Marchigüe | O'Higgins |
| Argomedo | Quinta de Tilcoco | O'Higgins |
| Lo Miguel | Rengo | O'Higgins |
| Chiloé | Curicó | Maule |
| Santa Teresita | Lampa | Metropolitana |
| La Paz | Pudahuel | Metropolitana |
| Malloco | Peñaflor | Metropolitana |
| Javiera Carrera | Buin | Metropolitana |
PMGD plants are up to 9 MW and connect to distribution companies' networks rather than to transmission. Capping them at 15% means a 9 MW plant can deliver only 1.35 MW at midday, when it produces most. Grenergy did not say in its letter how much energy it has been unable to inject since 10 November, nor has the Coordinator published the total capacity of the plants included in the order.
Grenergy's argument: the PMGD anti-islanding protection worked as required
Using the oscillography records the Coordinator requested, Grenergy explained that the disconnections were caused by the voltage vector shift (VVS) protection in the reclosers that connect each plant to the distribution grid. It is an anti-islanding function: it detects sudden changes in the voltage angle and disconnects the plant so it does not keep energising a section of network that has separated from the system, which is dangerous for utility workers.
According to the company, the protection was set at 18 degrees, in line with the Technical Standard for PMGD Connection and Operation (CNE Exempt Resolution No. 69 of 2026), and reacted automatically to the fault on the transmission grid, which was cleared in about 75 milliseconds. It added that the settings were updated and verified in August by a class A electrical installer, ahead of regulatory deadlines.
| Point | What Grenergy says |
|---|---|
| Cause of the disconnection | The voltage vector shift protection in the reclosers tripped |
| Protection setting | 18°, per the PMGD Technical Standard (CNE Res. 69/2026) |
| Original fault | On the transmission grid, cleared in ~75 ms |
| Settings verified | August 2026, by a class A installer |
| Risk to the system | Its plants do not warrant the exceptional measures of DS 88 |
| Proposal | Review the selectivity of anti-islanding settings with the distributors |
Source: Grenergy's letter to the National Electricity Coordinator of 12 November 2026, via Electrominería.
What the Coordinator ordered after the 8 November fault
The order relies on Supreme Decree No. 88 of 2019, the regulation for small generators, which allows exceptional measures when a plant puts the security of supply at risk. The Coordinator asked the owners of the PMGD plants named in the order to send, by 13 November, the output they had just before and after the event, the make and model of their protections, their settings and the records explaining the disconnection, as detailed in our story on the 15% cap on PMGD plants.
The Coordinator's concern has grounds: the fault pushed system frequency down to 48.93 Hz, against a nominal 50 Hz, and the 520 MW loss exceeded by about 30% the primary frequency control reserve, of roughly 400 MW, according to academics quoted by Electrominería. If many small plants switch off at once in response to a distant fault, the system suddenly loses generation it has to replace within seconds.
- 8 Nov, 14:54220 kV faultBetween Chena and Cerro Navia; 520 MW of PMGD trip.
- 9 NovCoordinator's order15% cap on the PMGD plants that tripped.
- 10 NovCap takes effect
- 12 NovGrenergy's letterSubmits oscillography records and asks to lift the cap.
- 13 NovData deadline
| 8 November fault | Value |
|---|---|
| Time | 14:54 |
| Facility | 220 kV lines between the Chena and Cerro Navia substations |
| Clearing time | ~75 milliseconds |
| PMGD disconnected | 520 MW (Metropolitan, Valparaíso and O'Higgins) |
| Minimum frequency | 48.93 Hz |
| Primary control reserve | ~400 MW |
Source: National Electricity Coordinator daily report and University of Santiago academics, via Electrominería (11 and 12 November 2026).
The underlying dilemma: protecting the grid without tripping PMGD plants
The case reflects a well-known technical tension in systems with lots of distributed generation. Anti-islanding protections must be sensitive enough to cut a plant off if its section of network is isolated, but if they are too sensitive they also react to transmission disturbances that do not affect them directly. Grenergy offered to review with distributors the selectivity of those settings, so that they can tell a real island from a distant fault.
The PMGD segment totalled 3,820 MW in May 2026, according to the Chilean Renewable Energy and Storage Association (Acera), and is at the centre of a regulatory debate over new curtailment-sharing rules and its new stabilised prices set by the CNE, as we explained in our story on PMGD stabilised prices. Grenergy is also one of the country's largest solar developers: in October it closed US$457 million in financing for its Algarrobal and Palmas projects, as we reported in our story on Grenergy's financial close.
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See advertising optionsWhat comes next
The Coordinator must review the information sent by Grenergy and the other PMGD owners before deciding whether to keep, change or lift the restriction, which has no end date. It will also have to deliver its fault analysis report, which should specify how many plants disconnected, why and with what settings. Meanwhile, the eight plants keep operating under a 15% ceiling.
Frequently asked questions
What did Grenergy ask the Coordinator?
To revoke the order capping at 15% of capacity the output of eight of its solar PMGD plants, in force since 10 November 2026.
Why did the PMGD plants disconnect on 8 November?
According to Grenergy, the voltage vector shift anti-islanding protection, set at 18° under the technical standard, tripped in response to a fault on a 220 kV line in Santiago that was cleared in about 75 milliseconds.
What is a PMGD?
A small distributed generation plant: a power plant of up to 9 MW connected to a distribution company's grid. In Chile most of them are solar.
Where are the capped plants?
Four in the Metropolitan Region (Lampa, Pudahuel, Peñaflor and Buin), three in O'Higgins (Marchigüe, Quinta de Tilcoco and Rengo) and one in Maule (Curicó), according to the Coordinator's registry.
