Pursuant to Article 116 of the Energy Law

4.3.9.
 
B
EHAVIOUR OF THE GENERATION UNIT IN CASE OF DISTURBANCE
 
4.3.9.1. Transient stability in case of short circuits in the transmission grid  
4.3.9.1.1. Protection in the transmission grid must ensure that electrically close faults are 
turned off in not longer than 150 ms, to avoid generation unit tripping due to instability (it is 
assumed that before the short circuit the generator is within the limits of permitted power 
supply diagram) if the short circuit power on the high-voltage side of step-up transformer 
exceeds the level of at least 6 times nominal power of the generator. It is also assumed that in 
the described situation redirecting of the auxiliary supply of the generator is not taking place. 
4.3.9.2. Transient stability due to small disturbances  
4.3.9.2.1. Oscillations of active power flows in the transmission grid must not result in 
generator tripping of the grid by application of protection devices nor to reduction of active 
power generation. 
4.3.9.2.2. Turbine- generation device for secondary control must not react to power 
oscillation in the grid. 
4.3.9.3. Generator tripping to auxiliary supply 
4.3.9.3.1. Turbo-generation unit with nominal power above 100 MW must be capable to 
exercise the following in case of frequency or voltage deviation and under the requirements 
defined in paragraph 4.3.8. of the Code:
- to switch to auxiliary supply mode, or 
- to reconnect to the grid within 15 minutes after the tripping caused by the 
mentioned voltage or frequency deviation.
4.3.9.3.2. Capability of the generation unit from item 4.4.9.3.1. to switch to auxiliary supply 
mode shall be guaranteed also in the case of transmission grid disturbance in line with the 
protection activation scheme. 
4.3.9.3.3. After the power unit has switched to auxiliary supply mode, turbo-generation unit 
shall be capable of operating under the given regime for at least 60 minutes. 
4.3.9.3.4. Hydro-generation unit, regardless of the installed power, shall meet all 
requirements set in items 4.3.9.3.1.- 4.3.9.3.3. for the turbo-generation unit.