Generation of High A.C. Voltages Cascaded Transformer - High Voltage Engineering

Summary

This video discusses high voltage generation through the use of potential and cascaded transformers. It explains how potential transformers can step up voltage for testing equipment in single and three-phase systems, while emphasizing the need for high voltage cascaded transformers when voltages exceed 400 kV. The cascading method not only facilitates easier transportation and installation but also manages insulation costs. Each stage in a cascaded transformer setup contributes to higher output voltage, and the design considerations for power loading on various windings are highlighted, showcasing the complexity and importance of transformer configurations in high voltage applications.

Takeaways

• ⚡ Potential transformers can step up voltage for both single-phase and three-phase systems, essential for testing equipment in transmission and distribution.
• 🔍 Testing transformers are designed for short-term testing of high voltage equipment with low power ratings.
• 📊 Current requirements vary by equipment type, with insulators needing 0.1 to 0.5 ampere and cables requiring 1 ampere or more.
• 🏗️ Cascaded transformers are used for generating voltages above 400 kV, offering advantages in weight and cost reduction for transport and installation.
• 🧱 Heavy insulation is necessary for high voltage levels, and its cost is proportional to the square of the operating voltage.
• 🔗 Each stage of a cascaded transformer typically consists of primary, secondary, and tertiary windings, except for the last stage, which has only two windings.
• 🔄 The total voltage output of cascaded transformers is cumulative, with each stage contributing to the overall voltage.
• ⚖️ Lower stages of cascaded transformers handle more load, affecting the design and current flow through the system.
• 📏 Current in each winding can be calculated using the formula I = P/V, indicating how power and voltage relate to current flow.
• 🔍 The main difference between potential transformers and cascaded transformers is that potential transformers typically have only two windings, while cascaded transformers require multiple windings to achieve higher voltages.

Q & A

What is the primary purpose of a potential transformer?

A potential transformer is used to step up voltage for testing and measurement in single-phase and three-phase systems.

What are the typical current requirements for testing high voltage equipment?

The current required for testing various equipment is generally between 0.1 to 1 ampere, depending on the specific equipment being tested.

How does a testing transformer differ from a potential transformer?

While a potential transformer steps down voltage for measurement, a testing transformer steps up voltage for testing purposes.

What is a cascaded transformer and why is it used?

A cascaded transformer consists of multiple transformers connected to generate high voltages, making transport and installation easier while reducing costs.

How does insulation cost relate to the voltage of a transformer?

The cost of insulation for transformers becomes proportional to the square of the operating voltage, making higher voltage units more expensive to insulate.

What is the significance of the tertiary winding in a cascaded transformer?

The tertiary winding in a cascaded transformer helps in transferring energy between stages and ensures the voltage induced on the primary is effectively utilized.

What is the loading challenge in cascaded transformers?

In cascaded transformers, lower stages are loaded more heavily compared to upper stages, requiring careful design to manage power distribution.

Why is a two-winding transformer used in the uppermost stage of a cascaded transformer?

The uppermost stage of a cascaded transformer only needs two windings to connect to the lower stages, simplifying its design and function.

How does the output voltage change in a cascaded transformer system?

The output voltage increases with each stage; for example, with three stages, the total output voltage can be three times the input voltage of the first stage.

What considerations must be taken into account when designing the windings of cascaded transformers?

Designers must account for the power loading on each winding and ensure that the current flow aligns with the total power requirements across all stages.