Evaluation of Distribution Transformer Placement Optimal Based on Load Balance

The distribution system is divided into primary and secondary distribution networks. The primary distribution network is the network from the main substation transformer (GI) to the distribution substation, while the secondary is the channel network from the distribution substation transformer to the consumer or load. The primary distribution network is better known as the medium voltage network (JTM 20kV) while the secondary distribution is the low voltage network (JTR 220/380V). The distribution network is the part of the electric power system that is closest to customers or loads compared to the transmission network. Currently, network electricity conditions throughout Indonesia are experiencing a decline of 5% which is due to various factors such as the medium-scale diameter of the conductors used, so at the farthest SR the value of overvoltage is 10%, the allowable voltage drop and must anticipate an increase in electrical load of 22.7 %, the placement of the transformer is not optimal and the distance the electrical energy travels from the transformer to the load is not paid enough attention so that the capacity of a transformer is not optimal and the voltage drop is also greater. Given these conditions, re-evaluation and planning is needed that takes into account planning criteria such as allowable voltage drops and continuity of electricity services so that optimization of the network used can emerge.

The distribution network is the part of the electric power system that is closest to customers or loads compared to the transmission network.Currently the condition of the electricity network throughout Indonesia has decreased by 5% which is caused by various factors such as the large diameter of the conductors used, so that at the furthest SR the overvoltage value is 10%, the allowable voltage falls and must anticipate an increase in electricity load of 22.7% , the placement of the transformer is less than optimal so that the transformer capacity and voltage are not optimal.Given these conditions, a re-evaluation is needed that takes into account planning criteria such as allowable voltage drops so that optimization of the network used can emerge.After optimization on the SRL01.014feeder the voltage dropped from 6.06 V to 5.76 V.

INTRODUCTION
Electric power systems require a continuous balance of energy in the prime mover with the electrical load in order to operate stably.Electrical loads continue to vary, such as lighting loads, electrical equipment, or electric motors.Changes in a load may be relatively small compared to the electrical power system as a whole, but every time the load increases or decreases it must be accompanied by a change in power in the generator's initial drive.If the mechanical power on the initial drive shaft does not immediately adjust to the magnitude of the electrical load, the frequency and voltage will shift from the normal position.Worse situations can occur if there is a loss of generation or large loads in the system, such as transmission lines.The presence of control equipment such as a governor on the turbine and a voltage regulator is expected to return the voltage and frequency to a normal position or within acceptable limits.However, oscillations generally occur around the final position.In most cases this oscillation will be damped and the system will return to stability.If instability occurs, it can disrupt the continuity of power services to some or even all consumers.
One of the methods used to analyze load balance is by calculating the values of losses and drop voltage on the distribution network conductors, calculating the voltage drop and voltage losses in the KTL feeder SRL01 area so as to obtain the values of losses and VD from the number of transformers installed on the line.By knowing the calculation results, the load balance between the loaded phases can be described so that the load on each phase is at least balanced.The image displayed is a diagram of a 20 kV single line UPJ South Semarang which can be phase shifted to achieve load balance and reduce the value of losses.

METHODOLOGY
Basic Calculation of Voltage Drop in the Electricity Orderly Area (KTL) feeder SRL01 Srondol South Semarang This voltage drop calculation is only specifically for calculating the channel from GI Srondol SRL01 Srondol, for example to the channel (Feeder) entering the Slawi network unit.What will be calculated here is the line on SRL01 to the transformer furthest from the GI in the Orderly Electricity Area (KTL), namely from the three-phase 20 kV main line, single-phase branching.The VD (voltage drop) formula is: The following is the calculation of cos Ø recorded on June 2023 from the SRL01 transformer (data taken from the 20 kV UPJ South Semarang single line diagram) at night peak load.Is known : With the nominal voltage determined by PLN, the minimum voltage and maximum voltage permitted are known so that the reliability of electricity distribution to consumers can be stable.Therefore, the maximum and minimum allowable voltage drop can be calculated as follows:

Calculation of Maximum and Minimum Voltage Drop Values
Table 6.VD Calculation

Real Power
After calculating the optimization value for the maximum and minimum voltage drop (VD) to obtain the maximum and minimum distance after optimization so that fairly small losses are obtained and reliability is getting better according to field data, then calculate the real power after the balance value is entered as in the table below:

CONCLUSION AND RECOMMENDATIONS
In calculating the voltage drop from the South Semarang Srondol GI as in the table, there is a difference between each feeder before it is balanced and after it is balanced.On the SRL01.014feeder the VD drops from 6.06490887 V to 5.761663427 V as the maximum limit and 5.458417983 V as the minimum limit.Feeder SRL01.019VD decreased from 3.7237644 V to 3.53757618 V as the maximum limit and 3.35138796 V as the minimum limit.Feeder SRL01.020VD decreased from 3.4019576 V to 3.23185972 V as the maximum limit and 3.06176184 V as the minimum limit.Feeder SRL01.021.B001 VD decreased from 1.42859233 V to 1.357162714 V as the maximum limit and 1.285733097 V as the minimum limit.Feeder SRL01.021.B005 VD decreased from 11.09773736 V to 10.54285049 V as the maximum limit and 9.987963624 V as the minimum limit.Feeder SRL01.021.B011 VD decreased from 2.4480303 V to 2.325628785 V as the maximum limit and 2.20322727 V as the minimum limit.Feeder SRL01.021.B004.U005's VD decreased from 3.25829385 V to 3.095379158 V as the maximum limit and 2.932464465 V as the minimum limit.

Table 1 .
Then the power factor at load and other times is calculated in the manner above and the results are entered in the table below: Primary data on Power Factor in June 2023 As a further note, a table will be shown which states the standard provisions for main line voltage drop, branches which are compared with the results of the calculations.

Table 2 .
Comparison of Standard Voltage Drop with Calculation Results Voltage Drop CalculationFrom the calculation of the branching feeder, a table of results for the current and voltage drop calculations is produced.

Transformer Placement Optimization Calculations Based on VD Based
on the known voltage drop value, the PLN decision is:

Table 5 .
Table of Allowable PLN Voltage Determinations

Table 7 .
Table Based on Allowable PLN Voltage After calculating the optimization values for the maximum and minimum voltage drop (VD) to obtain the maximum and minimum distances after optimization, the losses are quite small and the reliability is getting better according to field data.Next, calculate the losses after entering the balance values as in the table below: Comparison of Losses Values Before and After Optimization

Table 8
Comparison of Real Power Values Before and After Optimization After calculating the optimization values for the maximum and minimum voltage drop (VD), the maximum and minimum distances are obtained after optimization so that fairly small losses are obtained and reliability is getting better according to field data.Next, calculate the Secondary Phase Voltage after entering the balance value as in the table below :

Table 9 .
Comparison of Phase Voltages Before and After Optimization