Power Substation
6 Transformer Types You Can See In Commercial Installations
Transformers in commercial installations are normally used to change a voltage level from a utility distribution voltage to a voltage that is usable within the building, and are also used to reduce building distribution voltage to a level that can… Read more
Mar 16, 2015 | By Edvard Csanyi
Testing and Commissioning
Do Not Energize Oil-Filled Transformer Without Performing These 15 Tests and Checks!
The following tests and checks should be performed at a minimum to ensure that the transformer is ready to be energized. Do not energize the transformer without performing these tests and checks. If any of below explained tests fail and… Read more
Feb 23, 2015 | By Edvard Csanyi
Testing and Commissioning
Basic Transformer Routine Test – Measurement of Winding Resistances
The resistance between all pairs of phase terminals of each transformer winding are measured using direct current. Furthermore the corresponding winding temperature is measured. The measured resistances are needed in connection with the load loss measurement when the load losses… Read more
Feb 20, 2015 | By Edvard Csanyi
Energy and Power
4 Essential Features of Transformer On-Load Tap Changer (OLTC)
On-load tap changers (or circuit tap changers), as the name suggests, permit tap changing and hence voltage regulation with the transformer on-load. Tap changing is usually done on the HV winding for two reasons: Because the currents are lower, the… Read more
Jan 28, 2015 | By Edvard Csanyi
Protection
An example of transformer overload and short circuit protection
Transformer protection consists of both overload protection and short circuit protection. Overload protection is usually accomplished via proper selection of the secondary overcurrent protective device. NEC Article 450 gives specific primary and secondary overcurrent device ratings that may not be… Read more
Jan 21, 2015 | By Edvard Csanyi
Transformers
Why cooling is essential for long transformer life?
As you already know, cooling is really essential for long transformer life. Most transformers are designed for 55°C or 65°C rise. Using newer insulations such as Nomex, temperatures of 95°C and higher can be achieved. These temperatures can only be… Read more
Jan 09, 2015 | By Edvard Csanyi
Testing and Commissioning
Transformer routine test – Partial discharge measurement
This routine test aims to measure the partial discharges which may occur in the transformer insulation structure during test. Partial-discharges are electrical arks which form the surges between electrodes of any area of the insulating media of a transformer between… Read more
Dec 15, 2014 | By Edvard Csanyi
Energy and Power
Mineral oil-filled distribution transformer as one of the main part of electrical supply system
As you already know, this is the most common type of distribution transformer. It is one of the most important part and can be found on electrical supply systems in every country of the world. Although the insulating oil is… Read more
Nov 19, 2014 | By Edvard Csanyi
Maintenance
Maintenance and inspection of the transformer bushings
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… Read more
Aug 01, 2014 | By Edvard Csanyi
Testing and Commissioning
Testing of Power Transformer – Measurement of Zero-Sequence Impedance
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… Read more
Jul 21, 2014 | By Edvard Csanyi
Protection
Protection Against Overexcitation Of a Transformer
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… Read more
Jul 02, 2014 | By Edvard Csanyi
Transformers
An Example Of Transformer Tap-Changer Correct Adjustment
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… Read more
Jun 13, 2014 | By Edvard Csanyi
Maintenance
A transformer is only as strong as its weakest link
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… Read more
May 26, 2014 | By Edvard Csanyi
Metering
Instrument transformers (CTs, VTs) in the system
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… Read more
May 19, 2014 | By Edvard Csanyi
Maintenance
The most common accessories you can find on oil filled transformer
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… Read more
May 16, 2014 | By Edvard Csanyi
