The Jawa-Madura-Bali (JAMALI) System is the largest electricity network in the Indonesian archipelago, accounting for approximately 70 percent of the country's total generation capacity.

This network provides a steady supply of electricity and energy to nearly 160 million people across Jawa, Madura, and Bali. However, according to Ervin Saputra, Specialist of Learning at Transmission and Substation Training and Education Centre PT PLN (Persero), the radial system faces three major challenges.

"Firstly," he explains, "there is an imbalance in the magnitude of the upper- and lower-phase voltages towards the middle phase. This affects power quality and causes significant losses on the customer’s side. If the average load remains low, there's a risk of an exceedingly high increase, potentially causing permanent damage to equipment due to stress beyond its maximum capacity. Even the average distance of 200km per transmission section between main substations has an impact."

"Secondly," he continues, "if a disturbance occurs causing 3-phase tripping on two transmission lines simultaneously, it results in a loss of synchronization between the two sub-islands. The auto-recloser will fail because the synchronization requirements are unmet, leading to load shedding on both sides. With an unbalanced load source centre, the energy not served (ENS) will be remarkably high, leading to long recovery times."

The third challenge relates to the geographical location of the Indonesian islands. Saputra notes, "Sumatra, Kalimantan, Sulawesi, Maluku, Papua... All these islands outside Jawa, Bali, and Madura are located around the equator, which means a high amount of rainfall and frequent lightning strikes."

Saputra further highlights that local culture can impact the transmission and substation network, even inadvertently. "Many communities fly kites using threads made from wire. These kites can interfere with the network, and if the wire breaks, it can cause interference in the 2-line radial transmission."

To address these challenges, solutions such as reclosers, Double Shot Auto Recloser (AR), Multiphase Auto Recloser, and time delay wait to get synchronization have been implemented at the High Voltage Bay line transmission between several islands. Upgrading outdated equipment and devices at substations to digital substations has also helped eliminate hard wiring in control and protection systems. "We use digital communication, such as Telegram and WhatsApp, to receive automatic notifications generated by Python and gateway IEC 61850 on any fault type trip and location of faults at every asset," Saputra explains. "This reduces outage duration and allows precise decision-making to rectify issues immediately and recover outages."

Beyond these primary challenges, the accelerated implementation of large-scale renewable energy (EBT) projects introduces additional concerns. "There is concern that steam power plant assets will gradually become neglected and unproductive," Saputra says. "Moreover, creating large-scale EBT and battery banks involves significant investment costs and environmental issues, such as handling EBT waste and obsolete solar panels. Comprehensive strategies for sustainable disposal and recycling are needed."

Improving System Reliability

To improve system reliability, PT PLN has undertaken several measures. These include transposing the transmission section’s substation gantry and installing bay reactors or bay capacitors, depending on whether the voltage is too high or too low. "We turn on Double Shot AR and 2nd Stage AR in areas with frequent brief issues in the power lines," says Saputra. "For longer lines with several sections at risk of separating and causing synchronization problems, we activate Multi-Phase Auto Reclose. Our big plan is to build new lines to create a looped network for better reliability, meeting the n-1 contingency."

To implement double-shot Auto Reclose, second stage Auto Reclose, and Multi-Phase Auto Reclose, it is essential to ensure that the switch-on-to-fault function is set for permanent disturbances leading to the final trip. Additionally, Block Auto Reclose should be enabled when the Circuit Breaker is not ready, and Direct Transfer Trip should be used when Circuit Breaker Failure can still be relied upon. These measures will help prevent malfunctions in the auto reclose scheme.

This strategy enhances reliability when dealing with temporary disturbances, such as lightning strikes, kites, animals, and foreign objects, as well as permanent disturbances like falling trees.

The Right Equipment for the Job

Ensuring system reliability also involves selecting the right equipment, such as modern reclosers to cover blind spots and improve protection in distribution networks. Similar to the JAMALI System, Tonga Power Limited (TPL) faced issues with the high penetration of solar and wind in their distribution network, including blind spots for feeder protection. These issues were resolved with the introduction of G&W Electric’s Teros recloser, which features a simplified mechanism with integrated sensors, making it ideal for distribution automation applications. The Teros recloser offers high-speed clearing of temporary faults and radial overcurrent protection, enhancing reliability through sectionalizing and load break switching.

"With growing populations, increased demand for reliable power, new construction, reliance on technology, and the effects of climate change, utilities are working hard to save customers from the expenses and inconveniences of frequent outages," says John Mueller, chairman and owner of G&W Electric. "Reclosers have become the global market solution to the expansion and modernization of distribution networks for enhanced reliable power."

Read more about TPL’s implementation of the Teros recloser here.