A substation is a part of an electrical technology, transmission, and distribution device. Substations remodel voltage from excessive to low, or the reverse, or perform any of several other important functions. Between the producing station and consumer, electric power may additionally float through several substations at exceptional voltage stages. A substation may also encompass transformers to alternate voltage levels between excessive transmission voltages and lower distribution voltages, or on the interconnection of two one of a kind transmission voltages.
Substations may be owned and operated by using an electrical utility, or can be owned through a large commercial or commercial client. Generally substations are unattended, counting on SCADA for far flung supervision and control.
The word substation comes from the days before the distribution device became a grid. As central era stations have become larger, smaller generating plants have been converted to distribution stations, receiving their strength supply from a bigger plant instead of using their own turbines. The first substations were linked to handiest one energy station, in which the mills had been housed, and have been subsidiaries of that energy station.
A transmission substation connects or greater transmission traces. The simplest case is in which all transmission strains have the same voltage. In such cases, substation contains high-voltage switches that allow traces to be related or remoted for fault clearance or preservation. A transmission station may additionally have transformers to transform between transmission voltages, voltage manipulate/strength issue correction gadgets such as capacitors, reactors or static VAR compensators and device such as phase shifting transformers to control power glide between adjoining energy systems.
minimal HV station in Germany
Transmission substations can variety from easy to complex. A small “switching station” can be little more than a bus plus a few circuit breakers. The largest transmission substations can cover a large place (several acres/hectares) with more than one voltage stages, many circuit breakers, and a large quantity of safety and control gadget (voltage and modern transformers, relays and SCADA systems). Modern substations may be implemented the usage of international requirements inclusive of IEC Standard 61850.
A distribution substation transfers power from the transmission device to the distribution device of an place. It is uneconomical to at once connect strength customers to the principle transmission network, until they use huge amounts of electricity, so the distribution station reduces voltage to a stage appropriate for neighborhood distribution.
The enter for a distribution substation is normally at least transmission or sub-transmission strains. Input voltage may be, for instance, a hundred and fifteen kV, or whatever is common within the place. The output is a number of feeders. Distribution voltages are commonly medium voltage, between 2.four kV and 33 kV, relying on the dimensions of the vicinity served and the practices of the nearby utility. The feeders run alongside streets overhead (or underground, in some instances) and power the distribution transformers at or close to the client premises.
In addition to remodeling voltage, distribution substations also isolate faults in either the transmission or distribution systems. Distribution substations are usually the points of voltage regulation, although on lengthy distribution circuits (of several miles/kilometers), voltage regulation gadget may also be established alongside the line.
The downtown regions of big cities feature complex distribution substations, with high-voltage switching, and switching and backup structures at the low-voltage side. More usual distribution substations have a switch, one transformer, and minimal centers on the low-voltage aspect.
In distributed generation projects inclusive of a wind farm or Photovoltaic energy station, a collector substation may be required. It resembles a distribution substation even though power glide is inside the contrary direction, from many wind mills or inverters up into the transmission grid. Usually for economic system of production the collector system operates round 35 kV, despite the fact that some collector systems are 12 KV, and the collector substation steps up voltage to a transmission voltage for the grid. The collector substation can also provide strength issue correction if it’s far needed, metering, and manipulate of the wind farm. In a few special instances a collector substation can also incorporate an HVDC converter station.
Collector substations also exist wherein more than one thermal or hydroelectric strength plant life of similar output energy are in proximity. Examples for such substations are Brauweiler in Germany and Hradec inside the Czech Republic, in which electricity is gathered from close by lignite-fired strength plant life. If no transformers are required for increasing the voltage to transmission stage, the substation is a switching station.
Converter substations may be associated with HVDC converter vegetation, traction modern-day, or interconnected non-synchronous networks. These stations comprise power electronic gadgets to change the frequency of modern, or else convert from alternating to direct present day or the reverse. Formerly rotary converters changed frequency to interconnect systems; nowadays such substations are rare
A switching station is a substation without transformers and working best at a single voltage degree. Switching stations are occasionally used as collector and distribution stations. Sometimes they’re used for switching the present day to back-up strains or for parallelizing circuits in case of failure. An example is the switching stations for the HVDC Inga–Shaba transmission line.
Switchyard at Grand Coulee Dam, United States, 2006
Former high-voltage substation in Stuttgart, Germany, now 110 kV switching station. The 220 kV level is eliminated for grid simplification.
A switching station can also be referred to as a switchyard, and these are commonly positioned directly adjoining to or nearby a power station. In this case the generators from the power station supply their strength into the yard onto the Generator Bus on one aspect of the backyard, and the transmission strains take their strength from a Feeder Bus on the other aspect of the backyard.
An crucial characteristic achieved by means of a substation is switching, that’s the connecting and disconnecting of transmission strains or other components to and from the gadget. Switching events may be deliberate or unplanned. A transmission line or other factor can also want to be de-energized for preservation or for new production, for instance, including or removing a transmission line or a transformer. To maintain reliability of supply, groups purpose at keeping the device up and walking while performing preservation. All paintings to be done, from recurring checking out to including entirely new substations, ought to be done at the same time as keeping the whole system running.
Switchyard at Grand Coulee Dam, United States, 2006
Former excessive-voltage substation in Stuttgart, Germany, now one hundred ten kV switching station. The 220 kV level is eliminated for grid simplification.
Unplanned switching occasions are resulting from a fault in a transmission line or any other factor, for example:
• a line is hit by way of lightning and develops an arc,
• a tower is blown down by way of excessive wind.
The feature of the switching station is to isolate the defective portion of the machine in the shortest viable time. De-energizing defective device protects it from further damage, and keeping apart a fault helps hold the relaxation of the electric grid running with stability.
Elements of a substation
Substations usually have switching, protection and control gadget, and transformers. In a massive substation, circuit breakers are used to interrupt any quick circuits or overload currents that might also occur at the network. Smaller distribution stations may additionally use recloser circuit breakers or fuses for protection of distribution circuits. Substations themselves do not normally have mills, despite the fact that a strength plant might also have a substation nearby. Other gadgets which include capacitors, voltage regulators, and reactors may also be located at a substation.
Substations may be at the surface in fenced enclosures, underground, or located in special-purpose buildings. High-upward thrust buildings may additionally have several indoor substations. Indoor substations are usually determined in urban areas to reduce the noise from the transformers, for motives of appearance, or to defend switchgear from extreme weather or pollution conditions.
A grounding (earthing) device have to be designed. The general ground ability upward thrust, and the gradients in capability all through a fault (known as contact and step potentials), should be calculated to shield passers-through throughout a quick-circuit within the transmission system. Earth faults at a substation can cause a ground ability rise. Currents flowing in the Earth’s floor for the duration of a fault can purpose metal objects to have a considerably different voltage than the ground under a person’s feet; this contact capability affords a hazard of electrocution. Where a substation has a metal fence, it ought to be well grounded to defend humans from this hazard.
The main issues facing a energy engineer are reliability and cost. A good design attempts to strike a stability between these two, to achieve reliability with out excessive cost.