JAMALI System exposed to reliability and efficiency threats

The Jawa-Madura-Bali (JAMALI) System powers 70% of Indonesia’s electricity for 160 million people.

DESPITE its critical role, the JAMALI System faces several technical and environmental challenges that threaten its reliability and efficiency as a power network.

The JAMALI System experiences imbalances in the magnitudes of the upper- and lower-phase voltages towards the middle phase. This voltage imbalance affects power quality, leading to significant losses on the side of customers.

More importantly, this can cause irreversible damage to systems equipment, according to Ervin Saputra, specialist of learning at the Transmission and Substation Training and Education Centre PT PLN (Persero).

“If the average load remains low, there is a risk of an excessively high increase, which can cause permanent damage to equipment due to stress beyond its maximum capacity,” Saputra said.

The average distance of 200 km per transmission section between main substations further exacerbates this issue, he added.

Grid synchronisation

Saputra explained that if a disturbance causes 3-phase tripping on two transmission lines simultaneously, it results in a loss of synchronisation between the two sub-islands. The auto-recloser will fail because the synchronisation requirements are unmet, leading to load shedding on both sides.

This unbalanced load source centre results in a remarkably high energy not served (ENS) and long recovery times.

“If a disturbance occurs causing 3-phase tripping on two transmission lines simultaneously, it results in a loss of synchronisation between the two sub-islands,” explained Saputra.

The geographical location of the Indonesian islands presents unique challenges. Islands outside Jawa, Bali, and Madura, such as Sumatra, Kalimantan, Sulawesi, Maluku, and Papua, are located around the equator, which means they experience a high amount of rainfall and frequent lightning strikes.

“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,” said Saputra. 

Local culture can also impact the transmission and substation network. Many communities fly kites using threads made from wire, which can interfere with the network. If the wire breaks, it can cause interference in the 2-line radial transmission.

“Many communities fly kites using threads made from wire. These kites can interfere with the network,” he said.

Technological integration

To address these challenges, several solutions have been implemented. Reclosers like Double Shot Auto Recloser (AR), Multiphase Auto Recloser, and time delay synchronisation are utilised at the High Voltage Bay line transmission between several islands.

Upgrading outdated equipment and devices at substations to digital substations has 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 said. “This reduces outage duration and allows precise decision-making to rectify issues immediately and recover outages.”

The accelerated implementation of large-scale renewable energy (EBT) projects introduces additional concerns. There is a risk that steam power plant assets will gradually become neglected and unproductive.

Also, 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.

“There is concern that steam power plant assets will gradually become neglected and unproductive," Saputra said. “Moreover, creating large-scale EBT and battery banks involves significant investment costs and environmental issues.”

Improve reliability

To improve system reliability, Persero 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,” said Saputra.

For longer lines with several sections at risk of separating and causing synchronisation problems, Multi-Phase Auto Reclose is activated. The goal is to build new lines to create a looped network for better reliability, meeting the n-1 contingency.

Ensuring the right equipment is used, such as modern reclosers, also helps cover blind spots and improve protection in distribution networks.

The JAMALI System is a crucial component of Indonesia’s energy infrastructure, serving millions of people across Jawa, Madura, and Bali. By addressing the technical and environmental challenges and integrating advanced technologies and renewable energy sources, the system's reliability and efficiency can be significantly improved.