Harmonics Impact a Rising Due to Loading and Solution ETAP Using the Distribution Substation Transformer 160 kVA at Education and Training Unit PT PLN

Harmonics is a result of the progress of the use of non-linear loads are used in homes and offices. On the other hand, the energy crisis triggered the increased use of Energy Saving Lamps (LHE), Computer, electronic power equipment that is the cause of harmonics that can interfere with the electrical distribution system including Distribution Transformer (TGD). By performing measurements in the TGD, it is known the existence of harmonic currents which can increase the losses on the TGD. In the measurements made on the TGD Education and Training Unit Lubuk Alung capacity of 160 kVA obtained that influence THDi (Total Harmonic Distortion) currents in the TGD (6.57%) while according to the standard (4%). Shrinkage of 1.22 years of age transformer (4.067%). By using ETAP simulation active capacitor installation of 60 KVAR and 1500 mH obtained THD decline to 8% by neutral currents down to 12 A. From the simulation results ETAP effective current of each phase down 6% while the neutral current down 64%. Transformer derating of these conditions can be avoided and the use of the load can be increased. The impact of harmonics on transformer resulting in transformer losses increased from 3,755 kW to 3.775 kW. The increase in transformer losses (0.16 %) led to decreased work efficiency transformer. This resulted in a decrease in the capacity of the transformer. Keywords— Harmonics; Neutral currents; transformer; ETAP (Electrical Transient Analysis Program)


I. INTRODUCTION
Harmonics is a sinusoidal component of a period of a wave having one frequency which is a multiple of the original number of the fundamental wave as shown below. The waves distorted periodically occurring on the wave of voltage, current, or power. The phenomenon of harmonics on power system was first investigated by Steinmetz in 1916(Grady 2002. This harmonic phenomenon often appears on a three-phase system, because the current balance of each phase will affect the value of neutral current. This raises the iron core saturation in the transformer and electrical machinery, especially in the third harmonics. This saturation is caused by the non-linear load characteristics that burdens non-resistive, causing current and voltage Harmonic Distortion (THDi) and (THDv). THDi occur as a result of the use of non-linear loads (non-linear) on users of electricity. While the total demand distortion TDD is, which is the normal maximum current THD depending on the load current IL. In Table 2 the value of h is harmonic h. For voltage harmonics standard is determined by the voltage of the system used. In a three-phase system, harmonics are generated as a single phase system. Even-numbered harmonics are usually negligible because the resultant harmonic is the fundamental component produces a symmetrical waveform. In the analysis of three phase system harmonics, harmonics are reviewed based on the theory of symmetrical components.
The more harmonics appear in system, then the curve closer to a square shape. Two methods can be utilised to address this problem; first is by reducing the maximum load on the transformer, and second is to use a transformer with higher rating to allow the same load. Both of the aforementioned methods are known as de-rating. A higher rated transformer can supply a higher load current, and the selection of a transformer for a specific load is an important process. For instance, if the demand is less than the load, the system will not be cost effective. Alternatively, if the load is too high, the system will be overloaded. Therefore, in the present study, a method for selecting a transformer's rating based on the amount of THD was developed by assuming that the THD is linearly related to the temperature and rating of the transformer.
In the three-phase system is balanced, the currents of the three-phase balanced harmonic sources can be grouped according to the direction of the rotation phase. Flow distorted on each the phase will have the same waveform, and considered that the current in each phase is an odd function, so that a simple analysis.
Flows in S phase lagging by 1/3 period to the current phase R and phase T lagging 2/3 period of phase R.
In summation harmonic equation: With:  This does not eliminate the harmonic neutral current, but can generate higher neutral current of the phase currents. The first harmonic sequence is positive polarity, the second harmonic sequence of polarity is negative polarity and the third harmonic sequence is zero, the fourth harmonic is positive (repeatedly sequentially onwards) as shown in Table  1 above. Harmonic frequency higher than the operating frequency will result in decreased efficiency or power loss occurred.

A. Technical Effects Harmonics in Transformers
Transformer is designed to deliver the required power to the load with minimum losses at the fundamental frequency. Harmonic currents and voltages significantly would cause more heat. There are three effects cause more heat to the transformer when the load current contains harmonic components: [2] 1) Flow rms. If the transformer kVA capacity is only required for the load, harmonic currents can result rms current transformer becomes greater than its capacity. Increased rms currents cause losses in the conductor also increases.
2) Eddy-current loss. Induced current in the transformer caused by the magnetic flux. This induced current flowing in the winding, at the core, and in other conductive are overwhelmed by the magnetic field of the transformer and causing more heat. Components of this transformer losses increase with the square of the frequency eddy current flow causes. Therefore, it becomes a very important component of loss -loss transformers that cause warming by harmonics.
3) Loss Core. Increase in core loss caused by harmonics depends on the influence of harmonics on the voltage applied and the design of the transformer core. The larger the voltage distortion, the higher the eddy currents in the core laminations. Increase in core loss due to harmonics is not as critical as the two losses on top.

B. Harmonic Impact on Transformer
Current harmonic distortion (THDi) and voltage harmonic distortion (THDv) flowing in the transformer may cause an impact, as follows: Shrinkage (losses) increased load; Power is able to decrease and Reducing the economic life

C. Losses Increase in Transformer
The increase in transformer losses due to harmonics can be formulated as follows: Losses ∆ = Increase transformer losses due to harmonics (kW) PTot-H = total transformer losses due to harmonics (kW) PTot-R = Loss total transformer fundamentals (kW)

D. Impact Decreased Ability Power Transformer
Under the influence of current harmonics on the transformer causes an increase transformer losses. Due to the increase in loss causes a decrease in the power transformer capable transformer, where:

E. Impact of Economic Decline Transformer Age
Under the influence of current harmonics on transformer cause additional temperature rise of the real in the transformer. Due to the additional rise in the temperature of the transformer is actually probable cause conductor transformer winding hot spot temperature exceeds technical. Conductor temperature of hot spots which go beyond technical temperatures will damage the insulation, so that it will impact on the economic life of the transformer. Age determination is based on a reference temperature of 110˚ C with normal age (normal life) of 20.6 years. Factor Accelerated Ageing (FAA) for the hot spot temperature over ambient (ΘH) above 110˚ C, is

F. Identification Harmonics
To identify the presence of harmonics in the distribution system, it can be seen through the following steps: (1) Type the load supplied, for example, what equipment is used by consumers. When the amount of equipment that has a main component made of semiconductor materials such as computers and supporting equipment, variable speed motors, or other devices that use direct current harmonic problems, it can be estimated that there are installed by consumers. (2) Transformer serving non-linear loads in unbalanced load conditions. If the neutral current is greater, then it can be estimated for trilen harmonics and possible decline in the performance of the transformer. (3) Examination of Neutral Voltage Land. If there is a voltage difference Neutral-to-Ground at 2 volts at load state, then there are indications that the problem of harmonics in the load.

G. Harmonic Distortion
Distortion is a change in the form of waves that occur, if the response transfer system output electrical signal or mechanical stimulus input cannot produce perfectly. Distortions diverse as amplitude distortion, frequency distortion and inter-modulation distortion.
In the electric power system harmonic distortion caused by non linear loads. Current wave containing harmonic components called distorted flow. The content of the current and voltage harmonic wave can be expressed in a measure that is commonly used is THD (Total Harmonic Distortion). Similarly, harmonic distortion measurements to Individual Harmonic Distortion (IHD), which is the ratio between the RMS value of the individual harmonics and the RMS value of the fundamental. And can be expressed as follows: The relationship between THD with IHD can be seen from the following equation: IL is the maximum load current is needed in the fundamental frequency (fundamental) at the point of connection together.
Large harmonic voltage rms value is: Large harmonic current rms value is:

H. Load Loss (PLL) Trafo
To calculate the transformer load loss in per unit, can be searched by the following formula: [5]:

I. Measurement
Measurement of harmonics influence on TGD 160 kVA distribution transformers made on Education and Training Unit in PT PLN using a measuring instrument Fluke 43B Harmonics Aanalizer type.   Table 4.    Calculation results of the effects of harmonics on the distribution transformer TGD 160 kVA on Education and Training Unit in PT. PLN, obtained a decrease to 8 % THD with neutral currents down to 12 A.
The simulation results ETAP effective current of each phase down 6 % while the neutral current down 64 %. Derating transformer of these conditions can be avoided and the use of the load can be increased.

A. Running ETAP Simulation
ETAP simulation using harmonic measurement (Electrical Transient Analysis Program) Harmonic spectrum can be illustrated using the histogram, as in Figure 6, where each harmonic spectrum (h1, h2, and so on) is the ratio of current or voltage frequency current or voltage harmonics of the fundamental frequency (fundamental).

B. Efforts to Reduce Harmonics
Immediate action can be taken to reduce the effects of harmonics on power transformers are: (1) Network, The raising the neutral wire impedance value, namely by increasing the cross-sectional conductors. (2) Transformer, Reduce the capacity of the power supply transformer (transformer derating).

IV. CONCLUSIONS
The impact of harmonics on transformer resulting in transformer losses increased from 3,755 kW to 3.775 kW. The increase in transformer losses (0.16 %) led to decreased work efficiency transformer. This resulted in a decrease in the capacity of the transformer.