Power transformers must maintain a steady output voltage even when grid load and supply conditions keep changing. An onload tapchanger (OLTC) achieves this by altering the number of active turns in a transformer winding without interrupting the load current. CTR Manufacturing Industries Private Limited has produced intank onload oil tapchangers since 1997 to the design of ELIN OLTC GmbH.The range now covers ratings up to 400 kV and 500 MVA.
How an HT Capacitor Bank Works
An HT capacitor bank is a group of medium and high voltage capacitors connected to the supply at levels such as 3.3 kV, 6.6 kV and 11 kV, and up to 33 kV. The capacitors produce leading reactive power, which cancels the lagging reactive power drawn by the load. The current taken from the source then falls, the power factor moves closer to unity, and losses and voltage drop in the network come down.
In an automatic system, an HT APFC control panel monitors the load and switches capacitor stages in and out through vacuum contactors as demand changes. CTR’s MV/HV Reactive Power Compensator follows this approach, operating in auto and manual modes across 2 to 16 stages. Around the capacitors sit current limiting or harmonic filter reactors, residual voltage transformers, current and potential transformers, lightning arresters, and enclosures with mounting structures. CTR builds its systems with oil cooled, low loss capacitors that are type, endurance and life tested at NABL accredited laboratories.
Types of HT Capacitor Banks
The first choice is between plain and detuned banks. A plain bank suits networks with few harmonics. Where harmonics are present, a capacitor can resonate with the network and become overloaded, so a series reactor is added to shift the resonance point away from the dominant harmonic orders. CTR supplies magnetically shielded air core reactors in copper or Aluminium windings, available from 1.1 kV up to 40 kV, for this purpose.
The second choice is between fixed and automatic banks. A fixed bank supplies a constant amount of reactive power and suits steady loads. An automatic bank adds or removes stages as the load varies, which suits plants where demand changes through the day. For loads that change faster than contactor-switched stages can follow, a dynamic compensator can work alongside the bank to fine-tune the power factor.
Applications
HT capacitor banks are used wherever large inductive loads operate at medium or high voltage. Steel plants with furnaces, cement and mining operations,paper mills, chemical units and installations with large motors all benefit from them. Utilities use them at substations, and renewable energy plants use them to manage reactive power at the point of connection. In each case the aim is the same: keep the power factor close to the target and keep the network within its limits.
Choosing Right HT Capacitor Bank
The right selection depends on system voltage, required kVAR, present and target power factor, harmonic levels, load behaviour and whether the installation is indoor or outdoor. CTR manufactures medium and high voltage capacitors up to 40 kV and 50 MVAR, designed to IS 13340:1993, and can combine them with reactors and control panels into a complete system. To discuss your requirement, contact CTR through the enquiry form.