Insulation Coordination System 150kV Substation and Transmission Line against Lightning Surge Interference in Nickel Smelting Plant

Related with the increasing demand for electrical energy at nickel smelting plant, a highly reliable electric power system is needed to be able to supply important loads such as electric furnaces and auxiliary equipment. The electric power system delivers electrical power to consumers through substations and transmission lines. The distribution of electrical power through high voltage overhead lines sometimes goes through areas with a high enough lightning strike potential that it can cause sudden blackouts due to direct strikes and back flashovers. Therefore, it is necessary to insulation coordination of the substation and transmission line to avoid damage to electrical equipment. This research aims to determine the magnitude of the voltage due to lightning strikes on GSW and Conductor by varying the location of the lightning protection system on 150 kV overhead line which is useful for obtaining isolation coordination systems on transmission lines and substations in the nickel smelting plant. This research using the specific methodology and approach with a survey to collect data transmission tower specifications, tower grounding resistance, arrester and other supporting data and then create the data that has been collected into the model that has been developed in ATPdraw Software. Next, a simulation of lightning stroke on GSW and conductors without lightning protection such as Transmission line Arrester (TLA) and direct grounding that connected on GSW. This research was carried out by selecting lightning strikes in the current strike of 40 kA, 80 kA and 100 kA on transmission line and GSW with varying grounding resistance of 5 Ω, 10 Ω and 16 Ω which are simulated using ATPdraw software. This research showed that the installation of lightning protection equipment on high-voltage overhead lines and transmission towers resulted in a significant voltage drop due to lightning strikes and not exceed


Introduction
The 21st century is a very modern era, where technology is developing very rapidly, and electrical energy has become a basic and very important need.Transmission lines are one of the main technological parts in the process of providing electrical energy.If there is interference on the transmission line, it will also cause interference and affect equipment connected to the electric power system [1].
One of the large users of electrical energy is industry, in this case will be discussed as the research object is the nickel smelting industry.The location of the nickel smelting industry is PT Vale Indonesia (PTVI) Sorowako, South Sulawesi which is surrounded by forests, three lakes and mountains that are prone to lightning strikes.The PTVI transmission line is in that location and is often hit by lightning strikes, that the transmission line is a very important asset in distributing electrical energy for the nickel smelting process [2].Based on the Sorowako lightning density map [3] and PT Vale Indonesia's electric power system disturbance data 2009 -2024, 14% is caused by lightning strikes on the transmission line and substation, the Sorowako area has a high lightning density.This is reinforced by several insulators damaged on the 150 kV transmission line due to the over voltage value caused by lightning strikes exceeding the Basic Insulation Level (BIL) of the existing insulator, causing Flash over on the isolator.
Lightning arises due to potential differences between clouds and the earth.Separation of charges in clouds is a process because clouds move continuously and regularly, and during their movement the clouds rub against other clouds, causing negative charges to gather on one side of the cloud (top or bottom), as well as positive charges to gather on the opposite side [4].If the potential magnitude is different enough between the cloud and the earth to a large value, there ISSN 2723-6471 713 will be a discharge of negative charges from the cloud to the earth or vice versa, which is intended to reach equilibrium between the charges.Air is the medium that electrons will pass through in this charge discharge process.
Over voltage occurs on High Voltage transmission line can detained deep time limited.Based on the source, IEC created classification over voltage become over voltage sourced from lightning, over voltage sourced of switching and temporary over voltage.Over voltage sourced from lightning that occurs in the system power electricity due to two types of strike, that is direct strike and indirect strike.On the transmission line, direct strike can occur on the transmission tower parts such as wire phase, ground wire and tower.Meanwhile Indirect is strike to the ground near tower transmission line.For High voltage transmission line 150 kV, interference due to indirect strike can ignored.
When a lightning strike occurs on a high voltage transmission line, the voltage will rise in the line and the surge over voltage will propagate to the end of the line [5].
If the over voltage value exceeds the BIL value of the insulator it will cause Back Flashover.Regarding the threat of traveling waves coming from overhead lines so as not to damage the insulators and equipment in the substation, protection devices such as direct grounding connected to GSW, and surge arresters are needed to cut the traveling waves entering the substation, towers, and transmission line.Correlation between the insulation strength of electrical equipment, electrical circuits, and protective devices so that the insulation of the equipment is protected from the dangers of overvoltage technically and economically.This is referred to as Isolation Coordination in the electric power system [6].Good isolation coordination will be able to guarantee that: the equipment insulation will be able to withstand normal system working voltages and abnormal voltages that may arise in the system, the equipment insulation will fail only if an external overvoltage occurs and if failure occurs, it will only be in places that have been calculated and cause minimum damage.
The research on insulation coordination systems for a 150kV substation and transmission line in a nickel smelting plant offers significant benefits to the field of data science.Firstly, the study involves the collection, processing, and analysis of extensive electrical and environmental data.By leveraging data science techniques, such as statistical analysis and machine learning, researchers can identify patterns and correlations in lightning strike incidents, grounding resistance, and voltage surges.This allows for more accurate prediction models and improved decision-making processes in designing and implementing effective lightning protection systems.Additionally, the use of simulation software like ATPdraw in this research provides a rich dataset that can be used for further data-driven insights.By analyzing the simulation outputs, data scientists can develop optimization algorithms to enhance the performance of insulation coordination systems.This can lead to the creation of predictive maintenance schedules, minimizing downtime and maximizing the reliability of the power system.The integration of data science in this research not only advances the field of electrical engineering but also contributes to the development of smart, data-driven solutions in industrial power systems.
This research aims to determine the magnitude of the voltage on the 150 kV transmission tower which arises due to lightning strikes on GSW and conductors as well as varying the locations of the arresters on 150 kV overhead line which is useful for obtaining isolation coordination systems on transmission lines and substations in PT Vale Indonesia.This research was carried out by selecting lightning strikes in the current strike between 40 kA and 100kA on ground wire and conductor with varying grounding resistance between 5 Ω and 16 Ω with simulation use device Alternative Transient Program draw software [7].from the results of Previous studies showed that the installation of lightning protection equipment on high-voltage overhead lines and transmission towers resulted in a significant voltage drop due to lightning strikes lowering under basic insulation level of existing insulators 9 disc.

Literature Review
The 150 kV high voltage transmission line will be represented in the form of surge impedance or inductance.The overvoltage that occurs in the tower as surge impedance is directly proportional to the peak current, while in the tower as inductance the overvoltage is directly proportional to the steepness of the current.The surge impedance of the tower is derived from the geometric shape of the tower [8].In transmission lines there are three types of towers, namely The tower used in the research is type A. Based on figure 2, the transmission tower surge impedance modeling is divided into several parts, namely, modeling the tower legs, and modeling the tower arms and according to [9].The formula used to determine the value of each item in the tower: Note: Zti = Tower surge Impedance; Vt =Surge propagation velocity (300   ); ℽ=Attenuation coefficient (0.7); α=Damping coefficient (1); R: Damping resistance; L= Damping inductance.

Figure 2. Transmission Tower Model
A transmission tower as a cylinder and considering that the depth of true ground below earth's surface can be disregarded and h>>r [9], its surge impedance is simplified and given by: In electric power systems, arresters are one of the main equipment for insulation coordination.When a surge arrives at substation, the arrester will release abnormal electrical charges and voltages that will affect the substation and its equipment so that interference can be reduced [12].Arrester equipment has thermal resistance, which is able to withstand energy from current continuation, and must be able to break it [13].
For modeling the lighting arrester in ATP draw, the IEEE standard model [14] is used as shown in figure 3 below:  This research began with a survey to collect data such as transmission tower specifications, BIL of several electrical equipment in substation (average 750kV) and other supporting data.Then model the transmission line parameters into the ATP software and enter the data that has been collected into the model that has been developed [16], [17], [18].Next, create simulation with lightning stroke 40 kA, 80 kA and 100kA on GSW near tower 1 with grounding resistance is 5 Ω, 10 Ω, and 16 Ω with and without installing direct grounding connected to the GSW and then create simulation with lightning stroke 40 kA, 80 kA and 100kA with grounding resistance is 5 Ω, 10 Ω and 16 Ω on phase conductors with and without TLA.Then view and analyze the over voltage readings in each simulation that has been carried out.
Figure 5 illustrates the modeling of a 150 kV transmission line from tower 1 to tower 6 with a lightning strike model connected to the GSW near tower 1 using ATP draw software without installing a TLA on the tower and direct grounding connected to ground wire.For compare results chart from for circuits that use arresters and do not use arresters, a comparison formula is used: Note: V1 = peak voltage value before installing the arrester; and V2 = peak voltage value after installing the arrester.

Results and Discussion
In this study, a direct strike was carried out on tower because a direct strike on the tower can cause greater damage than an indirect strike.A direct lightning strike is where a lightning strikes directly at the tower, the strike at the tower can hit the ground wire and the phase wire.The simulation is carried out with the condition of lightning striking a ground wire which is assumed to be in 2 scenarios, namely the scenario before using protection and the scenario after using protection (TLA and direct ground) with the face time and tail time of the lightning current according to IEC standards is 8/20 µs.The analysis is carried out by looking at the voltage characteristics when lightning strikes the ground wire and conductor before and after installing the lightning protection system.

Simulation of lightning strikes on GSW
The simulation results of a lightning strike 100 kA with grounding resistance 10 Ω on a ground wire without direct grounding connected to the GSW can be seen in Figure 9, and with direct grounding installed, it can be seen in Figure 10.

Figure 8. Voltage wave due to lightning strikes on GSW without direct grounding
From the graph in figure 9, it is obtained: near tower 1 phase A :833 kV, phase B=778 kV and phase C 724 kV.This value comes from the voltmeter reading on the ATP draw modeling which is installed near the insulator of each phase.

Figure 9. Voltage wave due to lightning strikes on GSW with installing direct grounding
From the graph in figure 10, it is obtained: near tower 1 phase A :319 kV, phase B=308 kV and phase C 287 kV Figure 9 shows the increase in voltage on the phase A tower arm of 833 kV due to lightning strike 100 kA on the GSW without any additional protection on the tower, and the voltage value on the phase A will cause a back flashover [19], [20].The voltage value measured on the phase A exceeds the BIL of the 9 insulator pieces is BIL 730 kV that installed on the transmission tower so that it can cause short circuit disturbances in the electrical system.Meanwhile, figure 10 shows the voltage drop on tower 1 is 62% with value 319 kV by installing direct grounding connected to the GSW, so that it does not cause back flashover in the electrical system.
Based on the modeling in figure 5 and 6, the simulation then continues by injecting lightning currents of 40 kA, 80kA and 100 kA on GSW with varying grounding values of 5 Ω, 10 Ω and 16 Ω.The simulation is carried out with 2 conditions, namely when there is no direct grounding installed which is connected to the ground wire at transmission tower No. 1 and the substation, see table 1 and when direct grounding is installed, see table 2 the results of this simulation can be seen in the following tables: The table above shows that a lightning strike on a ground wire of 100 kA with a ground resistance value of 10 Ω and 16 Ω and a lightning strike of 80 kA with a ground resistance of 16 Ω causes BFO.Meanwhile, lightning currents of 40 kA with a grounding resistance of 5 Ω,10 Ω,16 Ω and 80 kA lightning strikes with a grounding resistance of 10 Ω and 16 Ω, as well as 100 kA lightning strikes with a grounding resistance of 5 Ω do not cause BFO in the electrical system.
The grounding resistance has the effect of reducing the peak lightning voltage with surge current 100kA from 1047 kV (16 Ohm) to 649 kV (5 ohm) to prevent BFO on the existing insulator.The table above shows that after installing direct grounding connected to the GSW on tower 1 and the substation close to the power transformer, there are no lightning strikes on the ground wire of 80 kA and 100 kA with grounding resistance values of 5 Ω, 10 Ω and 16 Ωs causing BFO insulators on the transmission line.

Simulation of Lightning Strikes on Phase Conductors
The simulation results of lightning strike 100 kA with grounding resistance 10 Ω on phase wires or conductors phase A without TLA installation can be seen in figure 11, and also the effect of TLA performance installed on transmission towers 1 and substation is shown in figures 12.  From the graph in figure 12, it is obtained: near tower 1 phase A :129 kV, phase B: -64 kV and phase C: -60 kV.
Figure 11 shows the increase in voltage on the phase A tower arm of 855 kV due to lightning strike 100 kA on the conductor phase A without any additional protection on the tower, and the voltage value on the phase A will cause a back flashover.The voltage value measured on the phase A exceeds the BIL of the 9 insulator pieces is BIL 730 kV that installed on the transmission tower so that it can cause short circuit disturbances in the electrical system.Meanwhile, figure 12 shows the voltage drop on tower 1 is 85% with value 129 kV phase A by installing TLA on tower 1 and substation, so that it does not cause back flashover in the electrical system [19], [20].
Based on the modeling in figure 7 and 8 [21], the simulation then continues by injecting lightning currents of 40 kA, 80 kA and 100 kA into the conductor phase A on the transmission line with varying grounding values of 5 Ω, 10 Ω and 16 Ω.The simulation is carried out with 2 conditions, namely when there is no TLA installed which is connected to the conductor at transmission tower No. 1 and the substation, see table 3 and when TLA is installed, see table 4. The results of this simulation can be seen in the following tables: The table above shows that a lightning strike on a conductor phase A of 40 kA, 80 kA, 100 kA with a ground resistance value of 5 Ω, 10 Ω and 16 Ω causes BFO on the transmission line with a value exceed of the BIL existing insulator 9 disc.
The grounding resistance has the effect of reducing the peak lightning voltage with surge current 100kA from 888kV (16 Ohm) to 824 kV (5 ohm), but still affect to BFO on the existing insulator.The table above shows that after installing TLA on tower 1 and arrester in the substation Larona, there are no lightning strikes on the ground wire of 100 kA with grounding resistance values of 5 Ω, 10 Ω and 16 Ωs causing BFO insulator on the transmission line.

Impact and Implementation on Data Science Knowledge
The findings of this research have profound implications for the application of data science in the optimization and management of high-voltage transmission lines and substations.The significant voltage drop observed after installing lightning protection equipment, as demonstrated in the simulations, provides a valuable dataset for data scientists to develop predictive models.These models can forecast potential overvoltage scenarios and suggest proactive measures to mitigate the impact of lightning strikes.By continuously monitoring and analyzing data from these systems, data scientists can create real-time alerts and automated response systems to enhance the resilience of the power infrastructure.
Furthermore, the study highlights the importance of grounding resistance in reducing the peak voltage during lightning strikes.This insight can be utilized to develop machine learning algorithms that optimize the placement and specifications of grounding systems based on historical data and environmental conditions.Such data-driven approaches can lead to more efficient and cost-effective designs, ensuring the safety and reliability of electrical equipment in harsh conditions like those in a nickel smelting plant.
The research also opens avenues for advanced data analytics in the context of environmental factors affecting electrical systems.By incorporating data on weather patterns, geographical features, and lightning density maps, data scientists can enhance the accuracy of risk assessments and develop more robust insulation coordination strategies.This holistic approach ensures that the power system is well-equipped to handle varying environmental challenges, thereby reducing the likelihood of power outages and equipment failures.
Lastly, the integration of data science in this research promotes a deeper understanding of the interactions between different components of the electrical system.By analyzing the data from various simulations and real-world scenarios, data scientists can uncover hidden patterns and dependencies that may not be apparent through traditional analysis methods.This comprehensive understanding enables the development of more effective and innovative solutions for lightning protection and insulation coordination, ultimately contributing to the advancement of both electrical engineering and data science fields.

Conclusion
Modeling transmission line systems, transmission towers and lightning strikes using ATP draw version 7.2 is very useful to determine the value of overvoltage due to lightning strikes on high-voltage overhead lines and substations by

Figure 1 .
Figure 1.Transmission tower type ) Note: Zt = Tower Impedance (Ω); R'= equivalent radius of the tower (m); and H = Tower Height (m) Activities to minimize the occurrence of internal and external disturbances to prevent damage to equipment caused by lightning strikes is to install arresters.An arrester is installation safety device resulting from overvoltage disturbances caused by lightning strikes or electrical surges.The arrester is tasked with protecting the insulation or securing the Vol. 5, No. 2, May 2024, pp.712-723 ISSN 2723-6471 715 installation from overvoltage disturbances caused by lightning strikes or high transient voltages from electrical equipment [10], [11].

Figure 4 .
Figure 4. Source of Lightning Strike in ATPdraw

Figure 5 .
Figure 5. Transmission line and lightning strike modeling using ATP draw without TLA and direct grounding

Figure 6 .
Figure 6.Transmission line and lightning strike modeling using ATP draw with direct grounding.

Figure 7
Figure 7 illustrates the modeling of 150 kV transmission line from tower 1 to tower 6 with a lightning strike model connected to the phase conductor near tower 1 using ATP draw software without installing Transmission line arrester.

Figure 6 .Figure 7 .
Figure 6.Transmission line and lightning strike at Conductor modeling using ATP draw without installing TLA Figure 8 illustrates the modeling of 150 kV transmission line from tower 1 to tower 6 with a lightning strike model connected to the conductor near tower 1 using ATP draw software with installing Transmission line Arrester on tower 1 and substation.

Figure 10 .
Figure 10.Voltage wave due to lightning strikes on Conductor without TLA From the graph in figure 11, it is obtained: near tower 1 phase A :855 kV, phase B=324 kV and phase C 293 kV.

Figure 11 .
Figure 11.Voltage wave due to lightning strikes on Conductor Phase A with installing TLA tower 1 and Substation Larona

Table 1 .
Voltage peak due to lightning strikes on GSW near tower 1 without direct grounding Note: < Basic Insulation Level of Existing insulator 9 disc (730 kV); >Basic Insulation Level of existing insulator 9 disc(730kV)

Table 2 .
Voltage peak due to lightning strikes on GSW near tower 1 with installing direct grounding

Table 3 .
Voltage peak due to lightning strikes on Conductor Phase A near tower 1 without TLA Note: < Basic Insulation Level of Existing insulator 9 disc (730 kV); >Basic Insulation Level of existing insulator 9 disc(730kV)

Table 4 .
Voltage peak due to lightning strikes on Conductor Phase A near tower 1 with TLA in Tower 1 and arrester in Substation Larona