Medium Voltage Control Power Transformers

ABOUT MEDIUM VOLTAGE CONTROL TRANSFORMERS - CPTs

Medium Voltage Control Transformers are single phase transformers used to supply low voltage control power in medium voltage switchgear. These reliably, step-down medium voltage inputs which range from 2.4kV to 15kV to low voltages of 120/240 VAC.

These low voltages are used to supply power to a control circuit in electrical panels, where a large variety loads are necessary or there is a need to connect to a primary distribution circuit.

CPT Details

  • Primary taps 3 +/-2.5%
  • For indoor use only
  • Self-cooled cast coil
  • Available as unfused only

Medium Voltage Control Power Transformers (CPTs) are single-phase dry-type transformers used to supply control power in medium voltage switchgear and transformers. They have open construction with an epoxy resin encapsulated coil.

Power ratings of 5, 10 and 15kVA with nominal primary voltages range from 2.4kV to 15kV and secondary voltages typically are configured for 120/240V (series parallel) operation. It is supplied with three +/-2.5% taps above and below nominal voltage on the primary winding.

For low power losses, the magnetic core is wound with grain-oriented electrical steel, and the high-voltage coil is vacuum encapsulated in epoxy resin. In addition to protecting the coil from moisture and foreign particulate matter, the resin epoxy provides a higher ability to withstand mechanical forces during short-circuits, than standard varnished Vacuum Pressure Impregnation (VPI) or “dip in varnish and then bake” process.

The secondary terminals are 1/2"-13 UNC brass bolts. Primary connections are 1/4"-20 UNC brass female terminals. The stainless-steel base of the CPT has 14mm oval holes for mounting in your equipment.

Typical applications include MV Switchgear, MV Motor Control, MV Generator, and Transformer Neutral Grounding.

Standard Control Power Transformers

Primary Voltage Window Size (Inches)/ Voltage Class KVA Model Number GE-ITI Model # ABB Model #
2400 to 14400 5kV, 15kV 5 kVA CPT5 - -
2400 to 14400 5kV, 15kV 10 kVA CPT10 - -
2400 to 14400 5kV, 15kV 15 kVA CPT15 - -

MEDIUM VOLTAGE CTs - CURRENT TRANSFORMERS

Window Type CT

Medium voltage current transformers from 5kV to 35.5kV Class system voltages are available in Bar Type, Window Type, and Wound Primary Type, with primary current rating up to 1000 Amps. CTs are encapsulated with epoxy or polyurethane resin cast construction, and are able to withstand heavy fault conditions, but are not made for exposure to sunlight. The core and coil assemblies are vacuum molded to ensure a homogenous, bubble-free construction. The medium voltage CT construction provides high di-electric and BIL 4.5 to 125 full wave crest kV.

The MV CTs can be supplied with round or rectangle window in the center. This provides easy installation for customers as they can use their primary cable or bus bar through the CT ID. Usually these CTs come with equal-potential shield around the ID surface. This equal-potential screen is attached with a pig tail (lead with connector) which comes out of the ID surface. This arrangement allows uniform distribution of charge (non-concentrated) around the surface, which further ensures that the CTs withstand high current and high voltage environment in long term use.

Bar Type CT

We also provide wound primary medium voltage CTs where primary and secondary terminals are usually taken out from the top surface of the CTs. Customers can make the primary connections using these terminals. The bus bar type MV CT construction usually have resin cast CTs with bus bar built into the construction. Various primary bar arrangements can be supplied to suit most applications. Medium voltage CTs come with or without mounting brackets.

MV CTs are designed to meet IEEE C57.13 or IEC 60044 standards. Partial discharge test is carried out as per Canadian CAN3-C13-M83 or as per IEC 60044. Standard burdens are used to measure accuracies (ratio and phase angle error) on calibrated accuracy test bridges. Hi-pot tests are carried out as per the required standards.

Wound Primary CT
Applications include:
  • Metering and relaying
  • Energy meter panels
  • Medium voltage switch gears and control panels
  • Medium voltage circuit breakers
  • Motor control panels
Download Medium Voltage Current Transformers brochure for information on MV CTs

MEDIUM VOLTAGE POTENTIAL TRANSFORMERS

Medium voltage potential transformers for up to 25kV class system voltages are available. PTs are encapsulated with epoxy or polyurethane resin cast construction.

The core and coil assemblies are vacuum molded to ensure homogenous, bubble-free construction. PT construction provides high di-electric and BIL strength.


MEDIUM VOLTAGE VTs - POTENTIAL TRANSFORMERS - SINGLE-PHASE

Medium voltage indoor PTs are constructed in various configurations – double pole or single pole designs. PTs can be supplied with two fuses, one fuse or no fuse, or internal fuse hub. MV PTs with fuse clips can be provided if required by the customer. Switchgear style design is also available. Usually these PTs are supplied with the metal mounting bracket.

Primary Voltage Ranges:

2400 to 4800, 2400 to 14400, 4160 to 13800, 7200 to 24000, 12000 to 24000, 18000 to 24000, 10200 to 24000, 24000 to 34500, 15240 to 34500. Voltage Class: 5.6kV, 15.5kV, 25.5kV, 36.5kV.

3-phase assembly using single-phase VTs with fuse hub design for a directly earthed primary connection.

MV PTs are designed to meet IEEE C57.13 or IEC 60044 standards. A partial discharge test is carried out as per Canadian CAN3-C13-M83 or as per IEC 60044.

Standard burdens are used to measure accuracies (ratio and phase angle error) on calibrated accuracy test bridges. Hi-pot tests are carried out as per the required standards.


MEDIUM VOLTAGE VTs - POTENTIAL TRANSFORMERS - 3-PHASE

We also offer indoor medium voltage PTs with 3-phase construction. 3-phase MV PTs designed in a single package are typically used for the application where physical size and location are very important. These PTs can be supplied with or without fuses. Terminal locations are clearly marked for proper connections.

Standard Wye-Wye primary connection (L-L) voltages are: 2400, 3300, 6600, 7200, 8400, 11000, 12000, and 13200. Secondary (L-L) voltages of 230, 120 and 110 are possible.

MV PTs are designed to meet IEEE C57.13 or IEC 60044 standards. Partial discharge test is carried out as per Canadian CAN3-C13-M83 or as per IEC 60044. Standard burdens are used to measure accuracies (ratio and phase angle error) on calibrated accuracy test bridges. Hi-pot tests are carried out as per the required standards.