A prefabricated substation puts the transformer and the switchgear into a cabin prepared in the factory, which shortens delivery, reduces the footprint and limits the work on site. Those advantages bring limitations with them. The inside of the cabin is laid out compactly, and the space needed for an oil treatment machine is often tight. The transformer is small, so the power available inside the station is limited as well. After commissioning the maintenance radius is usually longer. Where these conditions come together, the configuration of the oil treatment equipment cannot simply be copied from a conventional substation.
First condition: does the space take the machine
The dimensions of the ZYD-100 are 1200×1400×1800 mm and the weight is approx. 720 kg. That volume is not large in a conventional oil treatment room, but beside a prefabricated cabin it may well be. What has to be established on site is not the size of the machine itself but the working space around it: the front door has to open fully, the filter housings have to be withdrawable, and the oil draining port at the bottom has to take a container. Where the working space next to a prefabricated cabin is taken up by access routes, a fixed machine no longer fits there.
The mobile TYG-100 has a flow rate of 6000 L/h and needs no permanent position; it moves on once the work is finished. The JL series cart type oil purifier has a filtration accuracy of 10–25 μm, is small and can be wheeled to where it is needed, which makes it a suitable everyday tool in the operating room outside the cabin.
Second condition: does the supply carry the load
The total power of the ZYD-100 is 72 + 5 kW and the power supply is three-phase 380V / 50Hz. That load is rarely a problem in a conventional substation, but on a prefabricated substation it has to be checked in advance: the capacity of the transformer serving the cabin, the headroom left in the internal distribution circuit, and the length of the cable run to the machine. Where the capacity falls short there are two ways forward, either bringing in a separate supply for the machine or choosing a configuration with a lower demand.
A plate and frame filter press is another route. The LY-200 has a flow rate of 4800 L/h, is fitted with 40 sets of 300×300 filter frames and has an 11 kW motor, a load well below that of a vacuum degassing set, which suits sites with little power headroom that still need a strong filtration capacity. What it does not do is vacuum degassing, so the water content and the gas content have to be handled separately.
Third condition: environment and altitude
The environmental temperature range of the equipment is -20–45 °C, so an outdoor prefabricated site has to confirm that the local winter and summer extremes fall within it. Altitude affects the vacuum level: at high altitude the ultimate vacuum that the same vacuum pump can reach becomes poorer and the degassing result falls with it. This has to be confirmed when the site is selected, not discovered after the machine has been delivered.
Outdoor installation also has to account for protection. The electrical cabinet needs rain protection, the door seal has to be intact, and the phase failure and phase sequence protection has to be in operation, otherwise a single voltage fluctuation can stop the machine.
Fourth condition: how long is the maintenance window
| Condition on site | Direction for the configuration | What has to be confirmed |
|---|---|---|
| Space is available and the supply has headroom | A fixed vacuum degassing set with its own pipework | Position of the inlet and outlet connections, the slope of the pipework, the power circuit |
| Space is tight and the work is concentrated | A mobile machine brought in when needed | Access for the machine, a temporary power connection, the floor loading |
| Power headroom is limited | A filtration configuration with a lower demand | Capacity available on site, whether a separate supply is needed |
| Routine volumes are small | A cart type oil purifier for everyday work | Element specification, where it is stored, who operates it |
Looking at all four conditions together
Of the four conditions, the power capacity and the available space are hard constraints, the maintenance window is a constraint on time, and the environment is a correction term. If any one of them is not met, the configuration or the process route has to change; it cannot be resolved by coordination on site.
For a particular site, the information needed is: the power capacity available inside the station, the transformer rating, the usable floor area and the width of the access routes, the local extreme ambient temperatures and the altitude, and the length of the last maintenance window. Once these are assembled, there is a basis for discussing the model and the flow rate.
Selecting for a prefabricated site is not about finding a better machine; it is about finding a configuration that fits the conditions exactly.
