Pursuant to Article 116 of the Energy Law

4.2.11.5. Protection zones 
4.2.11.5.1. Protection system shall be operating by zones in order to trip a limited part of the 
transmission system under the faulty situation. Mandatory principle applied here is 
overlapping of protection zones for reliable protection operation and for every part of the 
transmission system to have its backup protection. 
4.2.11.5.2. Protection zones should be relevant for: 
- topology and conditions of the facility of the transmission system user
- technical requirements at the connection/ interconnection point. 
- 
connection status for the fault of one element of the transmission system. 
- 
4.2.11.6. Clearing times 
4.2.11.6.1. Clearing times in the transmission grid 400 kV, 220 kV, 110 kV shall be set by 
JSC EMS. In order to trip selectively only the transmission system element that is under fault 

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situation, timing of the protection activation shall be set in the so-called “stages” of 
activation. 
4.2.11.6.2. Clearing times of electrically close faults (excluding those with high impact of 
transitional resistance of the fault) on the transmission lines, which shall be tripped within the 
first stage of protection activation, shall be at the maximum of: 
- 100 ms in 400 kV transmission grid; 
- 100 ms in 220 kV transmission grid; 
- 
150 ms in 110 kV transmission grid; 
4.2.11.6.3. Electrically distant faults on the transmission lines, as well as on the neighbouring 
bus bars, shall be tripped in the second stage of distant protection and the trip time shall be at 
the maximum of: 
- 350 ms in 400 kV transmission grid, if the system for simultaneous tripping has 
not been used, i.e. 100 ms if that system is used;
- 500 ms in 220 kV transmission grid, if the system for simultaneous tripping has 
not been used, i.e. 100 ms if that system is used; 
- 
500 ms in 110 kV transmission grid, if the system for simultaneous tripping has 
not been used, i.e. 150 ms if that system is used; 
4.2.11.6.4. Faults on power transformers should be tripped at the maximum of
100 ms by activation of the electric protection from internal faults (differential protection, 
restricted earth fault protection, or alternative "tank" protection). 
4.2.11.6.5. Busbar faults should be tripped at the maximum of: 
- 100 ms if differential protection of bus bars has been installed (local protection); 
- 
time equal to trip of the second stage of distant protection of transmission lines, 
because the faults on them are eliminated by trips of supply lines in 
neighbouring plants (distant protection), i.e. time equal to trip time of the multi 
stage bi-directional distant protection of the transformer which low-voltage side 
is connected to these bus bars.