Ukraine’s power system continues to suffer from devastating attacks by the aggressor, which have intensified since 2022. As is known, electricity in Ukraine is generated by nuclear, thermal, combined heat and power plants, as well as hydro and pumped storage plants. In addition, there are renewable energy sources — wind and solar power plants — and other small distributed generation facilities.
However, electricity must also be transmitted to consumers through power grids, which include substations and distribution networks. When these critical nodes are damaged, it becomes difficult to deliver generated electricity to end users. As soon as shelling stops, emergency repair crews immediately begin restoration work.
Another option during repair works is to use backup lines connected to other transformers. However, in order to connect them, power to certain consumers must first be cut off, which takes some time.
There is also another challenge — a shortage of electricity in the system. In such cases, operators must act quickly to decide which consumers to disconnect to balance the power system. Otherwise, automatic protection systems could trigger uncontrolled shutdowns.
Therefore, disconnections are necessary to stabilize the energy system. They prevent larger, unplanned blackouts that would take much longer to restore.
To prevent automatic protection from triggering due to overloads or to allow repair work on high-voltage lines and substations, emergency or hourly outage schedules are introduced.
Emergency Outage Schedule (EOS) — is a list of electrical nodes (network points) that may be disconnected upon receiving a corresponding instruction from NPC “Ukrenergo.”
When the Ukrenergo dispatcher sees that consumption is about to exceed available generation or transmission capacity — especially during peak hours — they issue a command to distribution system operators (oblenergos) to apply the emergency outage schedule and specify the volume of restrictions in megawatts.
Since emergencies cannot be predicted or planned, this schedule does not contain specific hours for the start or end of outages.
The schedule is implemented within 15 minutes of receiving the relevant instruction from Ukrenergo. These are operational directives, so regional distribution operators do not have prior information about them. That is why consumers are notified after emergency outages occur.
EOS is introduced mandatorily to prevent a complete power outage in a given region or to avoid uncontrolled, automatic disconnection of the region from the grid (a blackout). In some cases, this involves urgent, immediate disconnections.
Hourly Outage Schedule (HOS) — also called stabilization outages — is developed for use during emergency situations in the power sector. It was introduced on March 25, 2024 (and may be applied individually by region) to stabilize the operation of the power system.
This schedule determines the order of consumer disconnections while ensuring uninterrupted power supply to critical infrastructure facilities. However, the sequence of disconnections may be adjusted upon instruction from Ukrenergo’s dispatcher.
Information about the inclusion of specific localities or streets in the HOS schedule, the order of disconnections by groups, and the hours and reasons for outages may be updated and changed as needed.
