Outdoor Substation are erected outside in open air. So for the protection of outdoor substations lighting arr-esters are installed over the High Tension line to protect the transformer form the surges. Earthing must be done in two or more phases. High tension fuse unit is installed for protection of high tension side and to control low tension side iron clad low tension switch of suitable capacity with fuses is installed.
This can be sub-divided into two types;
1. Pole Mounted Substations:
They are erected for distribution of power in localities. They can be 1 stout pole or H- pole and 4 pole structures with suitable platforms employed for transformers of capacity up to 25KVA, 125 KVA, and above 125KVA ( up to 250KVA) respectively.
Pole Mounted Substations are step down substations i.e. distribution transformer of capacity 250KVA where all the equipment is mounted on poles. This substation is used whenever a high voltage line is running and from it a small load such as a village or a small locality or factory is to be supplied. This substation are quite simple and cheap as no building for housing as in indoor substation. The equipment is required but because of increase in number of transformers, total KVA is increased, no load losses increases and the cost per KVA is thus more.
2. Foundation Mounted Substations:
Foundation Mounted Substations are normally for voltage 33 KV and above. This is recommended because large air clearances is required for above 33 KV. This substation are either situated near a power station i.e. Step-Up Substation or near a large load center i.e. Step-Down Substation. In this substation all equipment lies open in the air. This is usually enclosed by a fence from the point of view of safety.
Site Selection:
Following points should be keep in mind while selection of site for Outdoor Substations:
a. There must be easy access for heavy transport.
b. The clearances and spacing are not only to be governed by the operating voltage but also from the consideration of encroachment from outside.
This can be sub-divided into two types;
1. Pole Mounted Substations:
They are erected for distribution of power in localities. They can be 1 stout pole or H- pole and 4 pole structures with suitable platforms employed for transformers of capacity up to 25KVA, 125 KVA, and above 125KVA ( up to 250KVA) respectively.
Pole Mounted Substations are step down substations i.e. distribution transformer of capacity 250KVA where all the equipment is mounted on poles. This substation is used whenever a high voltage line is running and from it a small load such as a village or a small locality or factory is to be supplied. This substation are quite simple and cheap as no building for housing as in indoor substation. The equipment is required but because of increase in number of transformers, total KVA is increased, no load losses increases and the cost per KVA is thus more.
2. Foundation Mounted Substations:
Foundation Mounted Substations are normally for voltage 33 KV and above. This is recommended because large air clearances is required for above 33 KV. This substation are either situated near a power station i.e. Step-Up Substation or near a large load center i.e. Step-Down Substation. In this substation all equipment lies open in the air. This is usually enclosed by a fence from the point of view of safety.
Site Selection:
Following points should be keep in mind while selection of site for Outdoor Substations:
a. There must be easy access for heavy transport.
b. The clearances and spacing are not only to be governed by the operating voltage but also from the consideration of encroachment from outside.