Electric Power Grid

flowchart LR
G1[Generator\n11–25 kV] --> SU[Step-up\ntransformer]
SU --> T[Transmission\n400–765 kV]
T --> SD1[Substation\nstep-down]
SD1 --> Sub[Subtransmission\n66–132 kV]
Sub --> SD2[Distribution\nsubstation]
SD2 --> Pri[Primary distribution\n4–35 kV]
Pri --> SD3[Pole / pad transformer]
SD3 --> Sec[Secondary\n120 / 240 / 400 V]
Sec --> Cust[Customers]
classDef hv fill:#fee2e2,stroke:#991b1b;
classDef mv fill:#fef3c7,stroke:#92400e;
classDef lv fill:#dcfce7,stroke:#166534;
class T,SU hv
class Sub,Pri,SD1,SD2 mv
class Sec,Cust,SD3 lv