Electrical Transformation Centers: Components and Classifications

Posted on Mar 25, 2025 in Geology

Electrical Transformation Centers (CT) facilitate the installation or transformation of voltage (d1 + d). Transformers reduce high to low tension, complementing the switchgear and precise work. Their function is to distribute electrical energy at different voltages while allowing connection to the line and network at any point.

CT Classification:

  • Feeding: (in a point and in step)
  • Property: (company-owned or customer-owned)
  • Location: (outdoor or indoor)
  • Construction: (conventional, prefabricated, compact)

CT Feeding Types:

  • Feeding in a Point: Disposes of one feeding line and referral, connected to the core network, constituting the DIXA network endpoint.
  • Feeding in Step: Has one input line and one output towards another center.

CT Ownership:

  • Company CT: Properties of the supplier company.
  • Subscriber or Customer CT: Customer properties, with feeding voltage conditioned by the supplying company’s network.

CT Location:

  • Outdoor CT: Typically consist of a transformer not exceeding 160kVA, protected by fuses and sitting.
  • Internal CT: Located in closed areas with two variants:
    • Surface: Has a level access from the street, potentially part of a building.
    • Underground: Not installed under the public highway.

CT Construction:

  • Conventional CT: Located inside enclosures constructed of bricks, stone, or concrete.
  • Panel CT: Meet the need for small sizes, easy transport and installation, and maximum atmospheric resistance to agents. Can be surface or underground.

Modular Cell Types:

  • CML-d cell: Line cell
  • CMP-F cell: Protecting and fuses cell
  • CMP-to-cell: Automatic switch cell
  • CMIP-cell: Switch cell
  • CMM-d cell: Media cell
  • WRC-cell: Lift cell

Transformers

Two types of low voltage: b1 (231/133V), b2 (420/242V).

EBT Constitution:

  • Medium Voltage Bushings: Responsible for interconnecting the transformer windings with the medium voltage network.
  • Low Voltage Bushings: Responsible for the transformer windings’ interconnections with the BT network output.
  • Cuba: The deposit contains the refrigerant liquid where the nucleus and transformer windings are immersed. It closes with an upper lid perimeter screwed to the Cuba, serving as support for the active part of the transformer.
  • Expansion Deposit: Located in the upper part of Cuba and communicating with it, safeguarding against inundation. It also serves as an expansion chamber for oil due to temperature variations.
  • Oil Level Indicator: A window to observe the oil level, placed on both sides of the expansion tank.
  • Desiccator: Located in the communication line with the atmosphere, its mission is to ensure dry air enters the transformer as the oil level diminishes. This can be due to oil leakage or temperature lowering. It contains silica gel gravel.
  • Thermostat: Can be column type (indicating only transformer oil temperature) or sphere type (which, in addition to the above, has adjustable contacts for any desired value to cause fire alarms or transformer shutdown).

Internal Constitution:

  • Magnetic Core: Constitutes the road which establishes magnetic flow and is formed by sheets of ferromagnetikas steel alloy 0.35 mm thick at base d d silicium etween 3 and 5% and isolated electricament each other.
  • Windings: Constituted by copper coils of rectangular or circular section.

General Characteristics:

  • Primary Tension: The feeding tension of the transformer.
  • Maximum Service Tension: The highest voltage level the transformer can produce and operate in steady state (24kV-36kV).
  • Rated Secondary Network Tension: B1-230/127V; B2-400/230V.
  • Primary Rated Current: The current that runs through the transformer primary when it is supplying rated power.
  • Voltage Short Circuit: The voltage that must be applied to the transformer primary circuit for the short-circuited secondary to circulate its rated current.
  • Rated Secondary Current: The current that runs through the transformer secondary when it provides nominal power.
  • Orario Index: Defines the angle between the primary and secondary voltages. This number corresponds to the position of the small hand on a clock.
    • 0 degrees gap, orario index: 0
    • 330 degrees gap, orario index: 11
    • 180 degrees gap, orario index: 6
    • 150 degrees gap, orario index: 5