Pursuant to Article 116 of the Energy Law

4.2.3.
 
V
OLTAGE
 
4.2.3.1. The facility of transmission system user should permanently remain connected to the 
distribution grid for voltage range as referred to 3.2.3 of the Code.
4.2.3.2. In case voltage deviates outside of the limit from the section 3.2.3. of the Grid Code, 
the facility of the transmission system user stays operationally interconnected to the 
transmission grid for the time period depending on the size of voltage deviation, and 
according to the following conditions: 
- For the generation units in accordance with the point 4.3.8.2.1. 
- For the facilities of end users and distribution facilities for time period which is 
50% longer than time related to the generation units for the same voltage 
deviation. 
4.2.3.3. In case of voltage drop in the transmission grid caused by short circuit the facility of 
transmission system user has to remain connected to the transmission grid according to the 
following conditions: 
- if the voltage at the connecting/inter-connecting point is 0 V, the facility should 
remain connected for 0.15 s; 

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- if the voltage at the connecting/inter-connecting point is U
min
of the nominal 
value, the facility should remain connected for 1.5 s; 
- if the voltage at the connecting/inter-connecting point is higher than U
min
, the 
facility should remain connected until removing failure; 
- for voltage values between 0 and 90% of the nominal values, times are 
determined by linear interpolation in accordance with the Figure 4.1. 
U
min
is the minimal operational voltage for which the facility of transmission system user has 
to remain interconnected with the transmission grid in accordance with the point 4.2.3.2. 
Figure 4.1. 
4.2.3.4. In case of high voltage in the transmission grid, the facility of transmission system 
user has to remain connected to the transmission grid according to the following conditions: 
- for the time period up to 50 ms, the facility stays in operation if the voltage at 
the connection/inter-connection point is lower than or equal to 120% of the 
nominal value; 
- for the time period between 50 ms and 1000 ms, the facility stays in operation 
for voltage that is lower than or equal to the value which is determined based on 
linear interpolation, in accordance with the Figure 4.2, where U
max
is the 
maximum value of voltage in normal working condition, laid down in section 
3.2.3 of the Grid Code.
50
1000
1.20.
0
U
max
t (ms)
U (pu)
short-circuit 
voltage
voltage 
before 
failure 
U (r.j.)
1,5 
t (s) 
U
min
0 
0 
0.15 

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30 
Figure 4.2