Transformers Flashcards
What is a open circuit test for
Iron losses
How is maximum efficiency reached
When copper losses equal iron losses
What needs to be considered when paralleling two transformers
Phase sequence must be the same
Polarity must be the same
Winding resistance must be the same
What is the purpose of the buchole relay
Provides protection against internal faults
What is the purpose of the breather
When the volume of oil is changing inside the tank so is the air. The breather allows air to be taken in and out to prevent the transform deforming
What do bushings do on a transformer
Used to connect the internal connections to the external connection, bushings are usually tapered to shed rain fall
What is the benefit of arcing horns
Protect agents lighting stricks
Air gap is of less resistance then of the transformer core
What are Surge arrestors used for
Advanced method of lighting protection
There massive resistors on top a transformer normally raited to 20kv to 110kv they act as reverse baist diodes only conduct when voltage breaks over them
What is the benefits of transformer oil
Acts as a coolant
Acts as an insulator
Thickness must be low must move around easily
Name the 4 oil tests
Dielectric two electrodes spark
Crackle test for water
Colour clear and no particles
Acidity if acid is present there will be a bitter smell
Two types of transformer core types
The core type wrapped either side or the transformer shell
The shell type wrapped on top of each other
Name the two types of transformer windings
Consendrick winding two wrapped around each other
Sandwiche winding
Name two types of tap changing
On load automatic tap changing
Off load load has to be turned off the tap change
Give three advantages of using instrument transformers
Standardised instruments.
Increased safety.
Use of smaller cables
What is voltage regulation
The difference between voltage on no load and voltage on full load
