Introduction
The voltage drop is a critical parameter in distribution system. Since, the supply of the voltage should remain constant with tolerance ±6% according KM regulation to avoid any failures in electrical appliances such as air condition, motors and lighting. According to KM regulation [19] the voltage drop must not exceed 4% from transformer until the distribution board, also from distribution board to final circuit the voltage drop level should not exceed more than 2%. Therefore, the overall voltage drop should not exceed 6%.
Voltage Drop Calculation
In order to calculate the voltage’s drop for the cable, the following equation should be manipulated in order to get the voltage drop in percentage:
For calculating the voltage drop for the cable the following parameter must be consider:
Power factor= 0.9, R= Resistance of cable (Ω/m) , X = Reactance of the cable(Ω/m) ,VL-L = Base voltage
L: length of the cable. I: maximum load current
According to Doha cable, all LV cable does not have any reactance, therefore, the value of X=0, and the values of R and X are per meter. [20].
- Voltage drop from TX until stadium LV panel
The value of Resistance of 800mm2 cable according to Doha cable = 0.0292 Ω/km
The length of the cable = 1.5 (TX to wall) + 0.75 (LV to wall) + 2*0.7(depth) +0.2 (wall thickness) = 3.85m = 0.00385 km
I = 868.12 A
- Voltage drop from stadium LV panel to parking and street Distribution board
The value of Resistance of 240mm2 cable according to Doha cable = 0.099 Ω/km
The length of the cable = 115.8m = 0.1158
I = 379.4 A
Summary
Table 4-4 summarizes the voltage drop for each cable. And as table (4-4) shows all cables satisfy the condition of the voltage drop to be under 4%, hence, all selected cables were can be applied to the project.
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Voltage Drop |
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Cable coordination |
Cable Specification |
Voltage Drop % |
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|
TX until LV panel |
Current (A) | Resistance (Ω/km) | Distance (km) | ||||
| Stadium LV panel | 868.12 | 0.0292 | 0.00385 |
0.0367 |
|||
|
Sport activity LV panel |
991.23 | 0.0292 | 0.00385 | 0.0419 | |||
| LV panel until distribution board | |||||||
| Sport activity LV panel | AC | 488.65 | 0.0519 | 0.05 |
0.4763 |
||
|
Socket + pump |
248 | 0.197 | 0.15 | 2.7527 | |||
|
Lighting |
458.3 | 0.0642 | 0.15 |
1.6578 |
|||
| Firefighting | 270.8 | 0.16 | 0.16 |
2.6040 |
|||
|
Stadium LV panel |
AC + change room |
100.35 | 0.927 | 0.075 | 2.6207 | ||
| Audience + bathroom | 239.25 | 0.248 | 0.075 |
1.6716 |
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|
Poles (1+2) |
484.54 | 0.0519 | 0.075 | 0.7085 | |||
|
Poles (3+4) |
484.54 | 0.0519 | 0.153 |
1.4453 |
|||
| Parking+ street | 379.4 | 0.099 | 0.1158 |
1.6338 |
|||
|
Firefighting |
294.83 | 0.129 | 0.075 |
1.0715 |
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Total Voltage Drop from Transformers to the Loads |
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|
Loads |
Voltage Drop % |
|
| Sport activity LV panel |
AC |
0.52 |
| Socket + pump |
2.79 |
|
|
Lighting |
1.70 | |
| Firefighting |
2.65 |
|
|
Stadium LV panel |
AC + change room |
2.66 |
|
Audience + bathroom |
1.71 |
|
| Poles (1+2) |
0.75 |
|
|
Poles (3+4) |
1.48 | |
| Parking+ street |
1.67 |
|
|
Firefighting |
1.11 |
|