Metering
Measurement of residual currents on a distribution feeder
The measurement of the earth fault or residual currents on a distribution system feeder can be done by the so-called summation connection, where the three current transformers, one in every phase, are connected and the summated current is brought to… Read more
Jan 22, 2016 | By Edvard Csanyi
Energy and Power
Underground substations – Out of sight, out of mind
Underground substations help to bring high voltage electricity directly into the city center. The stations are environmentally friendly, almost unnoticeable, and have none of the planning problems encountered by surface-built solutions. Building new transformer substations in inner-city zones or expanding… Read more
Jan 09, 2016 | By Edvard Csanyi
Transformers
The Worst Transformer Inrush Current Occurs When…
When a transformer is first energized or reenergized after a short interruption, the transformer may draw inrush current from the system due to the core magnetization being out of sync with the voltage. The inrush current may approach short-circuit levels,… Read more
Dec 09, 2015 | By Edvard Csanyi
Protection
HV/MV/LV Transformer Protection Schemes
Transformer protection should take into account the power, voltage, vector group and the importance of the unit within a particular system. Depending on these factors, the transformers can be assigned to one of the two general groups. Let’s see these… Read more
Nov 28, 2015 | By Edvard Csanyi
Energy and Power
Stop Transformer Noise With These Rules and Techniques
There are a number of basic installation precautions and transformer mounting techniques which if carefully noted and followed, will minimize the audible sound level (noise) of energized transformers. Some of the more pertinent ones are noted below. 6 rules to… Read more
Nov 07, 2015 | By Edvard Csanyi
Testing and Commissioning
Eight Recommended Periodic Inspections of a Substation Transformer
The following periodic tests and inspections are recommended for routine maintenance of the medium power substation transformer. Gauge readings Cooling fans Control wiring Paint finish Fluid dielectric test Bushing and surge arrester insulators Bushing terminals Gaskets Gauge readings, ambient temperature,… Read more
Sep 02, 2015 | By Edvard Csanyi
Electrical Lectures
Practical Considerations of Transformer Heat and Noise
In addition to unwanted electrical effects, transformers may also exhibit undesirable physical effects, the most notable being the production of heat and noise. Transformer noise is primarily a nuisance effect, but heat is a potentially serious problem because winding insulation… Read more
Jul 31, 2015 | By Edvard Csanyi
Testing and Commissioning
12 Transformer Factory Tests Briefly Explained
The remainder of the twelve factory tests are briefly summarized below. The details of the test set connections and formulas of some of the listed tests are already described in separatly published articles, and for the rest you are directed… Read more
Jun 29, 2015 | By Edvard Csanyi
Energy and Power
Take into account these losses when purchasing power transformer
Losses and purchase price should be considered when deciding which transformer to purchase. The purpose of this technical article is to present a uniform approach that can be used to determine the dollar value of these losses over the life of the transformer…. Read more
Jun 26, 2015 | By Edvard Csanyi
Testing and Commissioning
Procedure for transformer lightning impulse test
The purpose of the impulse voltage test is to secure that the transformer insultations withstand the lightning overvoltages which may occur in service. Where: C1 – Impulse capacitor Rc – Charging resistor Rs – Series resistor Ra – Low-ohmic discharging resistor for… Read more
Jun 12, 2015 | By Edvard Csanyi
Metering
Understanding the ratios of magnetic HV instrument current transformers
The primary winding is a part of the network, carrying the actual load current. The transformer’s secondary circuits usually consist of several units, each of them having its own magnetic core and winding. The transformer has a rated current transforming… Read more
May 22, 2015 | By Edvard Csanyi
Maintenance
What to do if transformer has an excessive moisture content
The term “moisture” in the transformer industry is commonly used to indicate water which is absorbed in the paper or dissolved in the oil. Occasionally, the terms “water” or “water content” are used as an alternative way to describe the… Read more
Apr 24, 2015 | By Edvard Csanyi
Energy and Power
4 power transformer protection devices explained in details
The power transformer protection is realized with two different kinds of devices, namely the devices that are measuring the electrical quantities affecting the transformer through instrument transformers and the devices that are indicating the status of the physical quantities at… Read more
Apr 20, 2015 | By Edvard Csanyi
Transformers
Network distribution transformers serving grid and spot networks
Network transformers, the distribution transformers that serve grid and spot networks, are large three-phase units. Network units are normally vault-types or subway types, which are defined as (ANSI C57.12.40-1982): Vault-type transformers // Suitable for occasional submerged operation Subway-type transformers // Suitable for… Read more
Apr 08, 2015 | By Edvard Csanyi
Maintenance
Maintenance of transformer load tap changers (LTC)
LTC maintenance is the basis for the regulating transformer’s high level of reliability. The background for maintenance recommendations is as follows: Oil: For LTCs where oil is used for arc-quenching, the arcing at the arcing switch or arcing tap switch… Read more
Mar 25, 2015 | By Edvard Csanyi
