power systems loss

Typical Loss for Amorphous-Metal Core Distribution Transformers. The losses shown in the table are the typical values of a amorphous-metal cored distribution transformers. Core loss and Winding loss (watts) varies relatively as with the increase of the distribution transformer's kVA capacity. Also shown are he respective kilo-watthour loss in annual basis for different transformer capacity in 30% and 40% load factor. Annual kwh are based on peak transformer kW loading equal to kVA size.

Typical Loss for Silicon-Core Distribution Transformers The losses shown in the table are the typical values of silicon-cored distribution transformers. Core loss and Winding loss (watts) varies relatively as with the increase of the distribution transformer's kVA capacity. Also shown are he respective kilo-watthour loss in annual basis for different transformer capacity in 30% and 40% load factor. Annual kwh are based on peak transformer kW loading equal to kVA size.

How Instrument transformer contributes to system losses? Like any other transformer in general, Instrument transformers are intended to convert current or voltage from the high level in the transmission and distribution systems to the low levels that can be used by low voltage metering devices. Three primary applications for which instrument transformers are usually known: metering (for energy billing and revenue purposes); protection control (for system protection and protective relaying function); and load survey (for economic management of industrial loads).

(From npsc2010.uceou.edu ) The performance of transformer, the most ancient power system static element, is affected due to presence of distortion in the input supply voltage and non-linearity in the load current. Due to extensive use of modern power electronics controlled devices, the degree of non-linearity in the load current has increased in recent years. 

TRANSFORMER LOSSES AND THE EFFECT OF HARMONIC CURRENTS ON THESE LOSSES TUTORIAL DISCUSSION (From ANNEX D of IEEE STD C57.110-1998) Power transformers with ratings up to 50 MVA are almost always of core form construction. High-voltage and low-voltage windings are concentric cylinders surrounding a vertical core leg of rectangular or circular cross section. The vertical core legs and the horizontal core yoke members that constitute the magnetic circuit are made up of thin steel laminations. In the top and bottom yoke regions there are usually external clamping structures (clamps) that may be made of either metallic or insulating materials. Oil-immersed transformers are contained within a steel tank, while dry-type transformers may be either freestanding or surrounded by a metal enclosure. If direct current is passed through the transformer winding conductors, a simple I 2R loss will be produced, where R is the dc resistance of the winding. However, if an alternating current (ac) of the

HARMONICS EFFECT TO TRANSFORMER LOSSES How does harmonics contributes to transformer losses? Harmonics or harmonic distortion in electrical definition is a type of disturbance both found in the voltage and current waveform. Most common source of this distortion is primarily associated with non-linear loads like electronic loads. These electronic loads can either be from a single phase or three-phase form. Harmonics is said to be caused by a non-sinusoidal load currents usually are blamed from commercial power supplies and motor drives like personal computers and other electronically driven devices. Harmonic distortions to either voltage or current are also reflective to the other according to the ohm’s law principle. Previously we have discussed that transformer loss are usually categorized as no-load loss (referred sometimes as excitation loss), load loss (also called as impedance loss), and total loss (the sum of no-load loss and load loss). If you try to recall our discussions re

GUIDE FOR THE EVALUATION OF LARGE POWER TRANSFORMER LOSSES This guide is from United States Department of Agriculture Rural Utilities Service RUS Bulletin 1724-301. Stated in this guide is that Losses and Purchase price should be considered when deciding which transformer to purchase. The purpose of this bulletin is to present a uniform approach that can be used to determine the dollar value of these losses over the life of the transformer. The three different types of transformer losses that should be evaluated separately are: a. Load losses (sometimes called copper or coil losses); b. No-load losses (sometimes called core or iron losses); and c. Auxiliary losses (electric fan losses, other such equipment losses).

EFFECTS OF TRANSFORMER LOADING TO LOSSES Transformers, especially substation transformers are subjected everyday to loads that varies in any given period of time. The behaviour of its transformer loading is dependent to the nature of customers that are connected to it. The load profile of residential loads is not identical to the commercial ones the same with the commercial loads not identical to the industrial ones. It is also a given fact that a substation caters a mixture of these loads thus we can conclude that the transformer loading behaviour of one substation will not be necessarily similar to its adjacent substations. Sample of Transformer Loading Profile

AUXILIARY LOSSES IN POWER TRANSFORMER Beside Load loss and No load loss, another type of loss concerning substation transformers and are usually applicable to power transformers that are rated 5000kVA and above is the auxiliary loss. Auxiliary loss is a type loss that represents the electrical load of the transformer auxiliaries. This are the one that are utilize to operate the cooling fans and pumps of the transformer as discussed in our Load Loss topic. Although some utilities disregard this due to the fact that it does not impact the system’s loss in comparison to the Load and No-load losses, still technically they are still considered as losses. On the other hand, some electric utilities installs meters to properly account the power used in operating its substation auxiliaries thus, this can no longer be considered as losses.

NO-LOAD LOSS IN POWER TRANSFORMER NO LOAD LOSS is the other type of transformer loss which is also known as CORE LOSS. Core loss exists for the reason that transformers of any kind requires electrical currents and magnetic fields that is needed to magnetize the core of the transformer, the sad part is that they are present whenever the transformer is energized whether loaded or unloaded. Unlike the winding loss, core loss requires a constant value regardless of the transformer load; in short, core loss does not vary as transformer load changes. For example, if a power transformer has a core loss of 24kW, 24kW of power must be drawn from the source of supply to cover these losses at all times when the transformer is energized, even if the transformer load side are open.

LOAD LOSS IN POWER TRANSFORMER LOAD LOSS also known as winding loss is similar to the analysis of a transmission line represented by the I squared R formula. Load loss is called this way because the losses here vary with the square of the load current. Higher load means higher loss and lower load means lower loss. In the past, load loss is referred to as copper loss but later this has been corrected since modern transformers now use aluminium windings in substitute for copper. Losses occurring in transformers are mostly load losses, so the maximization of the transformer use with respect to losses is a very vital form of analysis.  

SUBSTATION TRANSFORMER LOSSES The primary function of a power transformer is to transform system voltage from one nominal level to another. The transformer has to be capable of carrying (within the guidelines of ANSI/IEEE Std. C57.92) the power flow for its particular location in the system under various operating conditions and contingencies, such as line or transformer outages. After we have discussed the contribution of transmission lines and its effects to the level of system’s loss in every utility, we now move to the next part of our discussion which is the Power Transformer. Unlike transmission lines, the functions of power transformer in the system are somewhat more complicated. Power transformers, also known as substation transformers, steps down voltage level received from transmission lines from a higher voltage down to primary distribution levels. This exists in every electric utility due to the fact that most distributors purchase wholesale electricity at transmission vol