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Medium Voltage

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We supply and install outdoor prefabricated substation type “Kiosk”.

We choose the “Kiosk” type because

  • No building construction is required and therefore a building permit.
  • They can be easily relocated.
  • They are of great resale value.
  • They are delivered with complete detailed mechanical and electrical drawings as well as support base construction drawings.
  • They also integrate  the low voltage distribution panel.
  • They include certified medium and low voltage panels.
  • They can be up to 5000 kVA in rating.
  • They have a floor providing protection against rodent entry.
  • They have independent spaces with separate access doors for the medium voltage, the oil or dry type transformer as well as the low voltage.
  • They have automatic indoor lighting, sockets and fans controlled by thermostat.
  • They have a lightning protection system for roof of type cage.
  • They have walls and a roof with insulation.
  • They can also include capacitor banks.
  • They can have space for a generator.
  • They can have aluminum doors.

We have “Kiosks” of EATON (Ulusoy Elektrik), AEG and Schneider Electric.

Medium Voltage Transformers of Oil and Dry (Cast Resin) Type.

Oil type medium voltage transformers contain:

  • Double-float Buchholz relays
  • Two contact thermometer
  • Dehumidifier Silica-gel
  • 5-position voltage selector (± 2×2.5%)
  • Expansion tank
  • Oil level indicator
  • Rolling Wheels
  • Lifting hooks
  • Quick pressure relief valve
  • Insulators MV – LV
  • Ground terminals
  • Power Plate

Dry (cast resin) type medium voltage transformers contain:

  • Rolling Wheels
  • Lifting holes
  • Connection busbars MV – LV
  • Ground terminals
  • 5-position voltage selector (± 2×2.5%)
  • RTD sensors PT100
  • Terminal box
  • Electronic protection relay against overheating with the ability to program four contacts (alarm, disconnection, error indication, fan control)
  • Power Plate

We have medium voltage transformers of EATON (Ulusoy Elektrik), AEG and Schneider Electric.

We supply and install:

  • Medium voltage distribution panels 7,2KV – 36KV.
  • Medium voltage motor control panels.
  • Medium voltage reactive power compensation banks.
  • Control panels for Photovoltaic substations and other R.E.S.

We have:

  • Input cubicles of PPC supply with or without lightning protection.
  • Protection cubicles for the medium voltage transformers.
  • Cubicles with fuse-disconnector or circuit breaker SF6 or vacuum.
  • Measurement cubicles of electrical units.
  • The cubicles are modular and connected to each other in order to create a complete medium voltage panel with a specific mission and power.

We have cubicles of EATON (Ulusoy Elektrik), AEG and Schneider Electric.

Buchholz Protection Relays for Oil Type Transformers

One of the most important parts of a medium voltage substation is the transformer protection relays for the safe operation of the substations and they must be checked for preventive maintenance.

Buchholz protection relay is placed between the transformer expansion tank and its oil tank and has two contacts, one for ALARM indication and one for TRIP disconnection. The Buchholz relay is activated in the following cases:

  • By collecting bubbles inside. So when the volume of the gas exceeds a certain limit, it first gives an alarm indication and if the volume is still increasing, it gives a disconnection command.
  • With the intense flow of oil in the pipe that connects the expansion tank to the transformer oil tank with a disconnection command.
  • With the drop of oil level (due to leakage etc.). When the oil level drops below the allowable limit, it initially gives an alarm signal and if the level still drops and falls below the safety limit, then it gives a disconnection command.

The detection of the above is critical and in case of non-operation there is a risk of destruction of the transformer.

In case of internal error in oil transformer, e.g. short circuit between coils in medium or low voltage coils, due to insulation failure, in place the oil temperature rises sharply as a result:

  • its evaporation and the creation of bubbles that go upwards.
  • the intense flow of oil.

We have Buchholz relays of Schneider Electric, ABB etc.

Temperature Controller for Oil and Dry Type Transformers.

One of the most important inspection tasks of oil or dry type transformers (cast resin) is to check their temperature, so that it does not exceed the limits set by the manufacturer of the transformer.

In oil transformers, oil thermometers are used to monitor the temperature of the transformer’s upper oil layer, which must not exceed 100 ° C. This thermometer is equipped with two contacts. When the temperature exceeds the first limit then the first contact closes and initially gives an ALARM indication command and if the temperature continues to rise, a TPIP disconnection command.

In dry type transformers (cast resin) there are thermistors PTC or PT100 placed in the low voltage windings whose resistance changes with their temperature. These thermistors work together with an electronic protection controller that displays the operating temperatures of the windings and monitors the operating temperature of the transformers, initially giving an ALARM indication command at the first level and if the temperature continues to rise, a TPIP disconnection  command. These relays also have the ability to control the ventilation of the substation.

We have temperature controllers od the Italian DIEL (MT200, MT300, etc.)

Protection Controllers of Electrical Units of Measurement

These controllers are devices designed to continuously monitor electrical units of measurement such as voltage, voltage, frequency, etc. in a part of the electrical installation. If the electrical unit exceeds the monitoring limits, then they automatically give the necessary commands (usually a TRIP command), in order to prevent damage or malfunction of the substation.

In some applications, such as Photovoltaic Parks, the protection controllers contribute to the operation of the photovoltaic station by monitoring the PPC network. So when the network is found outside the predetermined values, they disconnect the supply and connect it again when the values are again within the desired limits.

We have protection controllers SEPAM and MiCOM of Schneider Electric.

Medium voltage fuses for thermal and magnetic protection. With low cost and zero maintenance, medium voltage fuses are an excellent solution for protecting electrical equipment in the public and industrial distribution network up to 630kVA.

We have medium voltage fuses of ΕΑΤΟΝ (Bussmann).

Cold Shrink Medium Voltage Terminations 24KV outdoor and indoor for various cable cross sections.

  • Cold shrink termination is an easy and safe solution for terminating medium voltage cables up to 24 kV.
  • The electric field control device is pre-installed in the insulating body.
  • No tools required for installation.
  • Wide range of cable cross sections
  • 3-phase quorum.

We have medium voltage terminations of 3M and ENIA.

Indoor and outdoor surge arresters of Raychem to protect equipment from over-voltage transients.

  • Indoor surge arresters for medium voltage cubicles
  • Outdoor surge arresters for medium voltage cubicles
  • Outdoor surge arresters on the medium voltage side of the transformer
  • Safety helmets
  • Self-filtering masks for gases and dust
  • Insulated gloves up to 36KV
  • Insulating mat up to 36KV
  • Signaling plates
  • Voltage presence detectors 10-36KV
  • Earthing and short circuit equipment single and three phase
  • Medium voltage fuse disconnecting poles

We have complete range of Sofamel.