1. Load calculation principles:
1.1 Load estimation can be performed based on electric vehicle parking spaces during the scheme design stage; during the preliminary design and construction drawing design stage, the required coefficient method should be used for load calculation.
1.2 The capacity of the transformer should be considered when charging facilities are installed in existing parking spaces. The transformer load rate during peak hours should not exceed 100% when single busbar wiring is used, and should not exceed 60% when single busbar segmented wiring is used.
1.3 When the overload of the distribution transformer is caused by the access to charging facilities, technical means should be adopted to improve it. It is advisable to give priority to optimizing the control of charging power and charging time period. If necessary, the capacity of the distribution facilities should be increased and transformed. When increasing the capacity, it should be combined with the development of surrounding loads and leave appropriate margins.
1.4 The meaning of 100% construction of charging facilities or reserved construction and installation conditions for parking lots in newly built residential buildings:
a) It is advisable to set up a dedicated substation separately, with 20% configuration in the near term and 45% configuration in the long term to reserve high and low voltage distribution devices, transformers and other locations, and build in stages (i.e., the substation is configured with civil engineering conditions at 45% and all designs are installed at 20%).
b) There are three forms of regional distribution cabinets, terminal distribution boxes and pipeline designs: ① All designs are installed at 100%; ② All designs are installed at 20% (regional distribution cabinet-terminal distribution box-charging pile), and the other 80% only consider routing, civil engineering and other conditions; ③ Only the regional distribution cabinet is designed and installed at 20%, the terminal distribution box is cancelled, and the regional distribution cabinet directly supplies power to the charging pile, and the other 80% only consider routing, civil engineering and other conditions.
2. Calculation of the capacity of the dedicated transformer for charging facilities:
SΣ=KtKxCn(KnPn+KmPm)/(ηcosΦ)
SΣ: Total installed capacity of the transformer (kVA)
η: Transformer load rate, take 0.7～0.75
cosΦ: Power factor after compensation, take 0.95
Pn: AC charging pile (slow charging) installed power 7kW; (fast charging) installed power 40kW;
Pm: DC charging pile (fast charging) installed power, (generally 60kW, 120kW)
Kn: The coefficient of the number of slow-charging parking spaces (i.e., the actual number of slow-charging parking spaces/the number of parking spaces planned in the community) is 0.2 in the short term and 0.45 in the long term
Km: The coefficient of the number of fast-charging parking spaces (i.e., the actual number of fast-charging parking spaces/the number of parking spaces planned in the community) is 0.02 in the short term and 0.045 in the long term
Kx: Charging pile requirement coefficient, the number of charging piles (slow charging + fast charging), 0.75-0.85 for 5-10; 0.55-0.65 for 10-50; 0.4-0.45 for more than 50
Kt: Charging pile simultaneous use coefficient, the number of charging piles (slow charging + fast charging), 0.85-0.9 for 5-50; 0.6-0.7 for more than 50
Cn: The number of parking spaces planned in the community
The selection of Kt and Kx is mainly related to the following factors:
2.1 Use of electric vehicles: Currently, the overall number of electric vehicles is small, and the utilization rate of charging equipment itself is not high; the specific conditions of each building are different.
2.2 Even if charging at the same time, the battery status and performance of each electric vehicle are different.
2.3 In addition, slow charging and fast charging in the community are generally used at different times.