American-style prefabricated substations are divided into two types: those with an operating corridor (operators operate from inside the substation) and those without (operators operate from outside the substation). They feature fully insulated, fully sealed structures, high safety and reliability, and are maintenance-free.
The load switch in an American-style prefabricated substation is placed inside the transformer tank. Oil-immersed three-phase interlocking switches are available in two-position (terminal type) and four-position (ring network type) versions. Because this load switch is located inside the transformer tank, its open/closed position can only be determined by the indication on the external operating panel, and its operation requires a dedicated insulated operating rod, making it relatively complex. From this perspective, its operation is quite inconvenient.
Furthermore, because the opening contacts of the load switch (i.e., the obvious disconnection point) are not visible, it creates a sense of unease after disconnection. Moreover, if the load switch fails, replacement and repair will be extremely difficult. Load switches generally use vacuum circuit breakers.
