A potential transformer resin cast refers to a specific type of dry-type voltage transformer where the essential components are fully encased within hardened epoxy resin.
Potential transformers (PTs), also known as voltage transformers (VTs), are crucial for accurately measuring high voltages and providing isolation in electrical power systems. A key characteristic of a resin cast potential transformer is its construction method, which utilizes a protective resin enclosure for its active parts.
According to the provided reference:
Resin Cast Potential Transformers are dry type transformers the active part of which is completely embedded in quartz loaded Epoxy Resin by using vacuum moulding technique. After moulding the resin is hardened by polymerisation. The main insulation between Primary and Secondary & Earth is obtained by this epoxy resin.
Let's break down the key elements of this definition:
Key Characteristics of Resin Cast Potential Transformers
- Dry Type: Unlike oil-filled transformers, these transformers do not use liquid insulation.
- Active Part Embedding: The core components (windings) are fully enclosed.
- Material: This embedding is done using quartz loaded Epoxy Resin. The quartz filler adds mechanical strength and controls thermal expansion.
- Method: A vacuum moulding technique is employed to ensure the resin penetrates all voids and eliminates air bubbles, which could compromise insulation.
- Resin Hardening: After being moulded around the active parts, the resin undergoes polymerisation, a process where the resin molecules link together to form a rigid, solid material.
- Insulation: The hardened epoxy resin serves as the main insulation barrier. It provides the necessary electrical separation between:
- The high-voltage primary winding.
- The low-voltage secondary winding.
- Earth (ground).
Why Use Resin Casting?
The resin casting technique offers several advantages for potential transformers:
- Improved Insulation: The solid epoxy resin provides excellent dielectric strength and is less prone to partial discharge than air or oil insulation in certain applications.
- Mechanical Protection: The hard resin protects the windings from physical damage, vibration, and environmental factors like humidity and dust.
- Safety: Being a dry-type transformer, there is no risk of oil leaks or fire hazards associated with flammable liquids.
- Compact Design: Often allows for a more compact and lighter design compared to traditional oil-filled transformers for similar voltage levels.
- Maintenance-Free: Generally require less maintenance than oil-filled units.
In essence, a potential transformer resin cast is a modern, dry-type voltage transformer built for reliability and safety, primarily used in medium to high voltage substations and switchgear for metering and protection purposes. The core technology relies on embedding and insulating the active components within a durable, solidified epoxy resin block formed through vacuum moulding and polymerisation.
