What is a Transformer device?
The transformer is a device that transfers electrical energy from one circuit to another through the magnetic field without change of frequency.
Types of Transformer
Based on service
- Power Tr
- Distribution Tr.
What is the use of transformer?
In this age of modern transmission system with optimal loss it is necessary to transmit the power at very high level.it is not economical to produce electrical power at such a high voltage.Here comes the vital role of transformer, which enhances the voltage level from generating voltage to such a high level where the loss is minimal.
It is also used as booster in distribution system to give better voltage regulation.
General Fault In Transformer
General Fault in transformer are
- Open circuit Fault
- Over heating
- Winding short circuit fault
- faults due to lightening
Protection For Transformer
- Buchholz Relay
- Earth Fault Relay
- Over current relay
- Differential relay
- Digital relay
Earth Fault Protection
An earth fault usually involves a partial breakdown of winding insulation to earth Under this circumstance it is profitable to employ an earth fault relay One method of protection is core balance protection
Merz price circulating current principle or differential protection is commonly employed for power transformer protection from internal fault.
Points to be noted
The different of current in primary and secondary must be equalized in diff relay by using appropriate turns on CT’s connected with both primary and secondary
The phase difference of current still generates a relay current. To neutralize it is case of healthy condition it is required to connect the CT’s in phase opposition with respect to adjoint.
Protection Against Lightening
It is necessary to provide protection of transformer against transient & surges.The most commonly used devices for protection against lightening surges are
a). Earthing screen
b) Overhead Ground wires
c) Lightning arrestor
Transformer faults & protection type
|Primary winding Phase-Phase fault||Differential; Overcurrent|
|Primary winding Phase-Earth fault||Differential; Overcurrent|
|Secondary winding Phase-Phase fault||Differential|
|Secondary winding Phase-Earth fault||Differential; Restricted Earth Fault (REF)|
|Interturn Fault||Differential; Buchholz|
|Core Fault||Differential; Buchholz|
|Oil tank Fault||Differential; Buchholz; Tank Earth|