Generally Transformer can be classified into two. They are
1. Based on service as:
i) Transformer substations (Primary and Secondary).
a) Transmission substation. b) Distribution substation.
ii) Switching substation.
iii) Industrial substation.
iv) Synchronous substation or power factor correction.
v) Frequency changer substation.
2. Based on design it can be classified as:
i) Indoor type substation.
ii) Outdoor substation.
In installation, most of the substations are involved with dynamic of the voltage level of electrical provide (stepping up or stepping down). These are called electrical device substations as a result of electrical device is that the major part won’t to amendment the voltage levels.
Fig below represents the block diagram of typical electric supply system indicating the position of various types of transformer substations.
A transmission station connects two or additional transmission lines. The best case is wherever all transmission lines have the same voltage. In such cases, the station contains high-voltage switches that enable lines to be connected or isolated for fault clearance or maintenance. A transmission station could have transformers to convert voltage levels between two transmission voltages, voltage control/power issue correction devices such as capacitors, reactors or static volt-ampere compensators and instrumentation such as section shifting transformers, to manage power flow between two adjacent power systems. It additionally contains giant quantity of protection and management instrumentation (voltage and current transformers, relays and SCADA systems).
A distribution station transfers power from the gear mechanism to the distribution system of a region. It’s uneconomical to directly connect electricity customers to the most transmission network, unless they use giant amounts of power, thus the distribution station reduces voltage to a worth appropriate for native distribution.
The input for a distribution station is usually at least two transmission or sub-transmission lines. Input voltage could be, as an example, 115 kV, or no matter is common in the space. The output is variety of feeders. Distribution voltages are usually medium voltage, between 2.4 and 33KV, relying on the size of the space served and also the practices of the native utility. The feeders line streets overhead (or underground, in some cases) and power the distribution transformers at or close to the client premises.
In addition to remodeling voltage, distribution SS additionally isolate faults in either the transmission or distribution systems. Distribution substations are usually the points of voltage regulation, though on long distribution circuits (of many miles/Kilometers), voltage regulation instrumentality may additionally be put in on the road.
In distributed generation comes such as a wind farm, a collector station might be needed. It somewhat resembles a distribution station though power flow is in the opposite direction, from several wind turbines up into the transmission grid. Sometimes for economy of construction the collector system operates around thirty five kilovolt and the collector station steps up voltage to a transmission voltage for the grid. The collector station will conjointly offer power issue correction if it is required, metering and management of the wind farm. In some special cases a collector station will conjointly contain AN HVDC (high voltage direct current) static electrical converter plant. Collector substations jointly exist wherever multiple power or electricity power plants of comparable output power square measure in proximity.
A switching station is a station that will not contain transformers and operates solely at a single voltage level. Switching substations square measure typically used as collector and distribution stations. Typically they're used for change the present to back-up lines or for parallelizing circuits just in case of failure.