On 27 November 2011 at 10:20 am (Astana time), an emergency outage of 500 kV lines occurred in the Kyrgyzstan power grid at the Toktogulskaya HPP–Bishkek OHTL section, and at 10:25 am at the 500 kV Tashkent GRES–Shymkent interconnection OHTL at the Kazakhstan and Uzbekistan border.
The Kazakhstan North–South transit line was de-energized due to the cascade character of the emergency, the subsequent power surge and actuation of the emergency control automation.
Short-term shortages in the power supply to southern parts of the Unified Power System of Kazakhstan reached 912 MW and affected Almaty, Zhambyl, Shymkent and Kzyl-Orda oblasts.
The load shedding in the IPS of Central Asia amounted to 1287 MW (Uzbekenergo state JSC: 925 MW; Kyrgyzenergo OJSC: 362 MW).
By 10:49 am the operating personnel of the System Operator had synchronised the operation of the Zone South with the IPS of Central Asia and UPS of Kazakhstan. The power supply in the Almaty power unit was restored at 11:32 am (Astana local time).
As the 2011–2012 autumn–winter season started, non-observance of the interstate net power flows, power consumption and unstable parallel operation of the Integrated Power System of Central Asia has been registered at the border of the Unified Power System of Kazakhstan.