Different Types of Substations

Substations are where electrical wires are connected and switched and where the voltage changes from high to low and vice versa. The outdoor structure consists of wooden poles, truss towers, tubular frames, etc. If there is enough space and the visual appearance is not a problem, truss towers are usually installed to support the wires. Instead. Where appearance is more important, low-profile substations may be required. For example, the surface of an urban substation can be polished to give it a more attractive appearance and to fit in better with the nearby urban architecture.

Types of substations

The substation is an important element of an electrical power transmission system with transformers (and other power system components). Transformers in substations can be divided into different (possibly non-intersecting) groups according to the voltage level (power level), function in the grid, insulation level, or construction.

1. Transmission substations: used to connect two or more transmission lines via grid circuit breakers. These transformers are inserted into the grid system to improve the power efficiency of the system by reducing transmission line losses.

2. Distribution substations: Distribution transformers are used in order to reduce the power level of consumers at the distribution level.

Prefabricated Substation

3. Collector substations: usually step-up transformers, typically connected at the generation level to increase the power level, for example in wind farms for high power level consumers.

4. Converter stations: these devices can change important parameters such as the frequency of the applied signal.

5. Converter stations: Prefabricated substations are electrically connected by cables or bus bars. All high and low-voltage power distribution devices and transformers are conventional-shaped products. Prefabricated substations have a small size, small footprint, are lightweight, low cost, reliable, and are also called "Box-type substations" or "pre-installed substations".

Functions of the substation earthing electrode system

Substation earthing electrode systems provide a means of transmitting current to earth and dissipating it under normal and short-circuit conditions. In addition, they are designed to provide a degree of safety for personnel working or walking near grounded equipment from the risk of serious electric shock. In providing earthing points for the various types of equipment associated with substations, the substation earthing electrode system must meet the following requirements.

The resistance of the earthing electrode system to remote earthing must be sufficiently low to ensure the operation of protective relays in the event of an earth fault in the substation and in the lines and cables connected to it.

Low Voltage Fixed-mounted Switchgear          

(ii) The gradient of earthing potential within and near the substation shall be such that the "step" and "contact" voltages are limited to safe levels in the event of an earth fault.

The earthing electrode system must be isolated from services entering the substation so that any rise in the substation earth voltage (which may sometimes be in kilovolts) is not 'transferred' to telephones, water pipes, railway sidings, etc.

(d) The earthing electrode system should be such that the non-current carrying parts of the electrical equipment (e.g. sheathing and armoring of low voltage power and control cables) are not subjected to large fault currents.

(f) The earthing electrode system shall be capable of carrying the maximum earth fault current without overheating, mechanical damage, or excessive drying of the soil around the buried earth electrode and conductor.

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