Parallel Operation of Transformers; Conditions for Parallel operation of Transformers

By -

Parallel Operation of Transformers: Benefits and Conditions

Transformers are the backbone of electrical systems in industries and utilities. To ensure reliability, efficiency, and flexibility, it is often advisable to connect transformers in parallel. This article explains the advantages of using transformers in parallel and the essential conditions that must be satisfied for safe and effective operation.



Benefits of Using Transformers in Parallel

1. Improved System Availability

When multiple transformers are connected in parallel, the system becomes more reliable. If one transformer fails or is taken out of service for maintenance, the load can be transferred to the remaining transformers. This ensures continuous power supply and higher availability of the electrical system.

2. Higher System Efficiency

Transformers operate at maximum efficiency near their full load. With parallel operation, the load can be distributed among fewer transformers during light load periods, keeping them closer to full capacity. As demand increases, additional transformers can be switched on. This leads to optimized efficiency across varying load conditions.

3. Greater Flexibility for Load Growth

Parallel operation allows easy adaptation to future load changes. Instead of replacing an existing transformer with a larger unit, additional transformers can be connected in parallel. This provides scalability and operational flexibility in the power system.

4. Improved System Economy

Adding transformers in parallel is often more economical than installing a single large transformer. It avoids the cost of replacing existing equipment while ensuring effective utilization of available transformers. This approach also reduces the risk of under-utilization of oversized transformers.

Conditions for Parallel Operation of Transformers

While parallel operation offers many advantages, it is only effective when certain technical conditions are met. Failure to follow these requirements can lead to circulating currents, unequal load sharing, overheating, or even equipment failure.

1. Identical Voltage Ratio

Transformers connected in parallel must have the same voltage ratio.

  • If ratios differ, circulating currents will flow between transformers even under no-load conditions.

  • Since transformer impedance is very low, even a small voltage mismatch can cause large circulating currents and excessive I²R losses.

2. Equal Impedance and X/R Ratio

  • Transformers should have the same per-unit (p.u.) impedance to ensure proportional load sharing according to their ratings.

  • If the X/R ratio differs, one transformer may operate at a higher power factor than the other, leading to unequal load distribution.

  • This condition is especially critical in three-phase banks of single-phase transformers.

3. Same Polarity

Transformers must have the same polarity before connection.

  • Opposite polarity results in induced voltages of opposite directions, which can cause short circuits or dangerously high circulating currents at the output.

4. Same Phase Sequence

In three-phase systems, all transformers must follow the same phase sequence.

  • A mismatch in sequence leads to severe short circuits.

  • This condition is of utmost importance for safe parallel operation.

Conclusion

Parallel operation of transformers enhances system reliability, efficiency, flexibility, and economy. However, strict adherence to technical conditions such as identical voltage ratio, impedance, polarity, and phase sequence is essential. By following these guidelines, industries can ensure safe and effective use of transformers in parallel operation.

👉 For detailed explanation of the Tan Delta (Loss Angle) Test, click here.
👉 For specifications of Oil Type 990 KVA Transformers, visit this link.


Comments

Post a Comment

Popular posts from this blog

A2XWY; A2XFY Cables meaning; XLPE cables advantages over PVC cables

By -
Image
🏗 ️ Technical Specification of Aluminium Cables (IS 7098: Part 1 – 1988) When specifying aluminium cables, you will often come across codes like A2XWY . This code represents the construction, insulation, armouring, and sheath of the cable. 🔑 Cable Nomenclature Codes Code Meaning A Aluminium Conductor 2X XLPE (Cross-linked Polyethylene) Insulation Y PVC Outer Sheath W Steel Round Wire Armour F Steel Strip Armour WW Double Steel Round Wire Armour FF Double Steel Strip Armour Wa Non-Magnetic Round Wire Armour Fa Non-Magnetic Strip Armour AW Aluminium Wire Armour 👉 Example: A2XWY = Aluminium conductor + XLPE insulation + Steel round wire armour + PVC outer sheath. 📌 Note: For Copper Cables , no pref...
Read more

YWY, AYFY, AYY, AYCY, A2XCY Cables Meanings

By -
Image
📘 Cable Nomenclature Explained (PVC & XLPE Cables) Cable designations like YWY, AYFY, A2XCY might look confusing at first glance. But once you understand the logic behind each letter , reading technical specs becomes straightforward. 1. Basic Conductor Material ·          A → Aluminium conductor ·          (If “A” is absent, it means Copper conductor) 2. Insulation Material ·          Y → TROPODUR = PVC insulation ·          2X → TROPOTHEN-X = XLPE insulation 3. Armouring Types ·          W → Round Steel Wire Armouring ·          WW → Double Round Steel Wire Armouring ·          F → Flat (formed) Steel Strip Armouring ·       ...
Read more

Cable size and current carrying capacity

By -
Image
Cable size and current carrying capacity for XLPE insulated cable, non-armored, Twin or multicore cable is as below:- Conductor operating temperature is 90 degree Celsius Ambient temperature: 30 degree Celsius. Cable size and current carrying capacity for XLPE insulated, Armored, Twin or multicore cable is as below:- Conductor operating temperature is 90 degree Celsius Ambient temperature: 30 degree Celsius. For air and 20 degree Celsius for ground for installations require to comply with BS: 7671 Correction factors:- For Ambient temperature: Ambient temperature in degree Celsius Correction Factor 25 1.02 30 1.00 35 0.96 40 0.91 45 0.87 50 0.82 55 0.76 60 0.65 65 0.58 70 0.50 75 0.41 80 Ground Temperature Ambient temperature in degree Celsius Correction F...
Read more