Category Archive for: «Transformers»

Page 1 of 1212345»10 Last »

Maintenance and inspection of the transformer bushings

Six different inspections There are six different inspections to be performed on the bushings of the power transformer: Routine inspection Regular inspection (Once every two years) Inspection due to excessive partial heatings Local damages inspection (fissures) on the bushings Inspection for oil leaks Storage 1. Routine inspection Excessive local heating Pay attention to the clamping […]

Read More

Testing of Power Transformer – Measurement of Zero-Sequence Impedance

Earth-fault protection Purpose of the measurement The zero-sequence impedance is usually measured for all star-connected windings of the transformer. The measurement is carried out by supplying a current of rated frequency between the parallell connected phase terminals and the neutral terminal. The zero-sequence impedance per phase is three times the impedance measured in this way. […]

Read More

Protection Against Overexcitation Of a Transformer

Increase of the magnetizing current Overexcitation of a transformer means that the magnetic flux in the core is increased above the normal design level. This will cause an increase of the magnetizing current and the transformer can be damaged if this situation isn’t taken care of. For step-up transformers connected to generators during start-up, overexcitation […]

Read More

An Example of Transformer Tap-changer Correct Adjustment

Example A 13800V/4160 V transformer has five taps on the primary winding giving -5%, -2 1/2 %, nominal, +2 1/2 % and +5 % turns. If, on-load, the secondary voltage reduces to 4050 V then, which tap, should be used to maintain 4160 V on-load (assuming the supply voltage remains constant)? The following answer results: […]

Read More

A transformer is only as strong as its weakest link

Transformer rating Capacity (or rating) of a transformer is limited by the temperature that the insulation can tolerate. Ratings can be increased by reducing core and copper losses, by increasing the rate of heat dissipation (better cooling), or by improving transformer insulation so it will withstand higher temperatures. A physically larger transformer can dissipate more […]

Read More

Instrument transformers (CTs, VTs) in the system

Three main tasks of CTs and VTs The three main tasks of instrument transformers are: To transform currents or voltages from a usually high value to a value easy to handle for relays and instruments. To insulate the metering circuit from the primary high voltage system. To provide possibilities of standardizing the instruments and relays to […]

Read More

The most common accessories you can find on oil filled transformer

Accessories Every oil filled transformer has a variety of accessories for different purposes. Here, I’ll try to name the most common of them, together with picture and description. Note that pictures can be different depending on manufacturer. Also, you will notice an absence of transformer protection relay. I have written about it few times about […]

Read More

Earthing (grounding) transformer – Voltages during a ground fault

Protection from fault current Earthing Transformer or grounding transformer is the neutral grounding transformer - star connected on the primary and has an open delta on secondary. Open Delta has two terminals. A resistor is connected across these two terminals. This voltage drop will be sensed by the earthing transformer connected across this resistor. At the […]

Read More

Inspection and Test procedures for Instrument Transformers

Procedures to follow: Visual and Mechanical Inspection Electrical Tests: Electrical Tests – Current Transformers Electrical Tests – Voltage Transformers Electrical Tests – Coupling-Capacitor Voltage Transformers Electrical Tests – High-Accuracy Instrument Transformers (Reserved) Test Values: Test Values: Visual and Mechanical Test Values: Current Transformers – Electrical Test Values:Voltage Transformers – Electrical Test Values: Coupling Capacitor Voltage […]

Read More

Testing of power transformer – Measurement of impedance voltage and load loss

Purpose of the measurement The measurement is carried out to determine the load-losses of the transformer and the impedanse voltage at rated frequency and rated current. Apparatus and measuring circuit On Figure 1 above (Circuit for the impedance and load-loss measurement) there are following figures: G1 – Supply generator T1 – Step-up transformer T2 – […]

Read More
Page 1 of 1212345»10 Last »


FOLLOW EEP!

Subscribe to Weekly Download Updates: (free electrical software, spreadsheets and EE guides)

EEP's Android Application
Electrical Engineering Daily Dose
Daily dose of knowledge and news from
Electrical Engineering World

Advertisement