Analysis of the Effect of an Installation of a Single Tuned Passive Filter on Harmonics and Distribution Transformers

Non-linear loads on power systems cause harmonics and losses in distribution transformers. Results of the measurements on the two distribution transformers showed several phase transformer test-driven development (TDD) values above the standard SPLN D5.004-1: 2012. The values were 5.58% in the phase transformer, T 1 and 5.48% and 6.10% in S and T phases of the second transformer, respectively. In the calculations, the transformer losses due to harmonic currents were 1.64 kW in the phase transformer T 1, and 1.64 kW and 1.82 kW in the S and T phases of transformer 2, respectively. Designing a single-tuned passive filter based on the characteristics of the current, voltage, power, and power factor in the phase transformer with a value above the TDD standard can reduce the harmonics and losses. A filter with different specifications in each filtered phase transformer was obtained. The filter reduced the TDD value on the phase transformer T 1 to 3.55% and to 3.88% and 3.43% on the on phase T and S phases of transformer 2.  Moreover, it reduced the losses to 0.73 kW on phase transformer T 1, and 1.02 kW and 0.92 kW on the S and T phases of transformer 2. 


INTRODUCTION
Power quality disturbances, such as voltage sag and harmonic distortion, have increased in the past few decades. One of the factors that cause decline in the quality of electrical power distribution is the use of electric utilities that are non-linearly loaded. Non-linear load causes the emergence of harmonics on the power system. Harmonics cause a deviation in the frequency current or voltage, which is an important aspect in determining the quality of the electric power [1][2][3][4][5]. Determine the number of harmonics generated by the nonlinear load in the residential, commercial and office loads in the feeder distribution and the usefulness of energy due to the harmonic. Natural modelling techniques that model non-linear loads are Norton equations. Harmonic equations harmonic equations models are used from the most accurate devices generated from the experiments. A distribution feed of 20 kV/400V district to analyze from the nonlinear load at distortion level and harmonic loss. The initialization model is "bottom-up", starting from Norton end user device and then modelling residential, commercial and office load. The result of the harmonic distortion in the Distribution system can increase power by up to 20% [6]. The concept of improving the quality of power reduces harmonic distortion with a power distribution system consisting of a balanced and unbalanced non-linear load type. Improved power quality using dual active power filter (APF's) in grid-connected distributed generation scheme. Active power filters effectively produce compensated signals for harmonic elimination and APF to compensate for the current to be inducted into the distribution network for harmonic elimination under balanced and unbalanced non-linear load conditions. APF is controlled using instant P-Q theory and DG inverters are controlled using a simple control strategy. The proposed system was developed and the results were obtained using MATLAB / SIMULINK software [7].
Distribution transformer is a device in the power system that is directly affected by harmonics. Harmonics in the distribution transformer increase power loss (losses), which reduces transformer performance [8]. To overcome these problems, a filter is installed to reduce harmonics. The filter used is a single-tuned passive filter. Single-tuned passive filters are low-cost filters, which help improve the power factor and compensate the reactive power [9]. The transformers used in the study are two 3-phase distribution transformers of 400 kVA (Faculty of Engineering, University of Riau). Transformer 1 has a phase (T) with a current harmonic value above the standard. Transformer 2 has two phases, namely, phases S and T.

THEORETICAL AND RESEARCH METHOD
Harmonics is a disorder that occurs in power distribution systems because of current and voltage waveform distortions. Current and voltage waveform distortions are caused by the formation of waves with frequency integer multiples of the fundamental frequency [10].
The ratio of each component of the harmonic frequency of the fundamental frequency (50 Hz) is an n-order harmonic, which is defined as [11]: where h is the order (order harmonics), fh is the nth harmonic frequency, f is the fundamental frequency (50 Hz). Harmonic wave is the wave of the 2 nd to the h-order. The wave with a fundamental frequency (50 Hz) is not a harmonic wave. Harmonics arise because of the non-linear loads connected to the distribution system. A non-linear load is an electronic device with many semiconductor components, which act as the switch that works of any wave cycle of the voltage source in the working process. The effects of harmonics are as follows: (i) excessive heat production, which damages the insulation; (ii) malfunction of the labor power equipment, control systems, and energy measurement tools; (iii) reduction in the power rating (derating) of transformers; (iv) reduction in the power factor; and (v) shrinkage of the network [10]. Total harmonic distortion (THD) is the ratio of the value of the current or voltage harmonic components to the value of the current or voltage on the frequency base, and is usually calculated in percentages [9].
where THD is the total harmonic distortion (%), Mh is the RMS value of the current or voltage harmonic h (A or V), and M1 is the RMS value of the current or voltage at the fundamental frequency (A or V). Individual harmonic distortion (IHD) is the ratio of the value of the current or voltage of individual harmonics to the fundamental value of the current or voltage [9]. and where IHDi is the individual harmonic current distortion (%), IHDv is the individual voltage harmonic distortion (%), Ish is the harmonic currents of h (A), Vsh is the voltage harmonics of h (V), I1 is the fundamental current (A), and V1 is the fundamental voltage (A). Some analysts try to avoid difficulties by finding the THD at the peak load current fundamental frequency rather than the instantaneous sample at the fundamental frequency, which is called the total where Ih is the harmonic current order, IL is the maximum load current at the fundamental frequency at the point of common coupling (PCC). IL can be measured in two ways. First, the burden that has been installed in the system is determined, and then the average value of the maximum load current of the previous twelve months is calculated. Second, IL is estimated in the new system based on the load profile that will be installed. The IL value can be determined by the following equation [12]: where kW is the average power demand, PF is the power factor, and kV is the line to line voltage at PCC. The three-phase short circuit at the PCC can be determined by the following equation [9]: where MVA and kV represent the three-phase short circuit capacity in the megavolt ampere and the voltage line-to-line at PCC, respectively. One of the parameters that affect the performance of the distribution transformer is the power loss (losses). Losses may arise because of harmonic distortions. The copper losses in the distribution transformer caused by harmonics can be expressed as follows [9]: is the copper losses (pu), h is the harmonic order (pu), and Ih is the current order (A). Increased iron losses in the transformers caused by the harmonic distribution can be expressed as follows [9]: where Z is the impedance of the single-tuned filter (Ω), R is the resistance (Ω), L is the inductance (H), and C is the capacitance (F). The stages in this study are as shown in Figure 1. Filters were designed based on the electrical characteristics of the phase transformer harmonic current value that exceeds the standards and the tuned harmonic order. In this study, the phases, which have values above the standard TDD, were referred to as the phase transformer T 1, Transformer S phase 2, and phase T Transformer 2 with harmonic orders of 3, 5, and 3, respectively. The sample calculations to determine the filter specification of the phase transformer T 1 tuned into the 3rd order are as follows: 1) Determine the amount of the reactive power compensation required [14].
On the basis of the results, the value of the reactive power in the smallest QVAr phase transformer T 1 was 12.7 kVAr. The exact value of the reactive power compensation is necessary to search for the magnitude of the power factor improvement.  The entire filter design specification phase transformer can be seen in Table 1. The comparison of the results of all the phase transformers can be seen in Table 2. The results showed that no work amount exceeded the standard set. The harmonic current absorbed by the filter reduced the value of the TDD on the transformer, which owns the parameters that measure the current harmonics. The unfiltered current TDD value was obtained from direct measurement using a power quality analyzer. The filtered TDD was calculated based on equation (5). The current value after filtering in-phase transformers T 1 is calculated as follows: The short-circuit impedance of the system (Ω) [9]: To calculate the filtered value of the reactance L and C in order harmonics: The reactance L in order harmonics-3 is calculated as follows: To calculate the value of the short circuit resistance and reactance-3 in the harmonic order: Resistance value ℎ (1) = ℎ (3) = 0.4 Ω, while the short circuit reactance in the harmonic 3rd-order transformer is as follows: The value of the short circuit impedance Z system on 3rd-order harmonics is calculated as follows: The harmonic currents on the 3rd order after the installation of the filter is The current and TDD transformer on another phase can be seen in Table 3. The calculation of transformer losses caused by harmonics filter installation is the same as the calculation of the losses before the installation of the filter. The losses will be reduced by the reduced current harmonic filter that was designed based on the orders described previously. In addition to reducing the order harmonics, the single-tuned passive filter mounted in parallel also absorbs power from the system. This will certainly cause filter assembly losses. The magnitude of the losses resulting from the installation of filters on phase transformer T 1 is as follows: Power absorbed by the filter in phase transformer T 1: = 66.86 2 × 0.00587 Ω = 0.026

Tables 3. Current Value and TDD Transformers Before and After the Filter Installation
The P value is the result of the mounting losses at 66.86 A filter, a fundamental flow filter, and a 5.87 mΩ resistance value filter. The amount of filter with X fund power factor of 3.34 Ω can be calculated as follows. In the filter phase transformer T 1, the reactive power of 12.7 kVAr is the power capacitor used to compensate the reactive power in the system. Therefore, the losses in the filter are as follows:  Table 4. It shows that using one single-tuned passive filter in each phase can considerably reduce the losses.