Keeping Lights on

KOMPAS/RIZA FATHONI

The Senayan area of Central Jakarta is dark against the background of buildings along Jl. Jendral Sudirman during a blackout on Sunday (4/8/2019). The major power outage that hit Jakarta and its surrounding area disrupted transportation and economic activities for millions of residents.

An electricity crisis has occurred again. A massive power outage hit western parts of Java on Sunday from 11:50 a.m. to late at night. The blackout paralyzed the activities of the people in the capital city of Jakarta and several other areas.

The power disruption occurred because of damage to two power circuits in the northern line of the Java-Bali transmission system. The Java-Bali transmission system consists of two lines, north and south, each with two circuits. The northern line links Rembang, Ungaran and Mandiraja, while the southern link connects Kediri, Kesugihan and Tasikmalaya. The Ungaran-Pemalang network was disrupted.

As the load was low, state electricity company PLN used a circuit in the southern line. The switch of the electricity supply from the eastern to western part of Java through a circuit in the southern line caused a failure in the Kesugihan-Tasikmalaya line. The power supply was cut off and the voltage dropped.

From the supply side, the electricity situation in Java-Bali is safe because there is an excess supply of electricity. According to PLN, the installed capacity of the Java-Bali electricity system is 34,550 megawatts (MW), higher than the electricity demand during peak load, which reaches 27,070 MW.

So far, the Java-Bali transmission system connects a number of regions. According to electricity industry observer Fabby Tumiwa, the electricity interconnection system connects several power plants and substations, as well as high, medium and low voltage networks. Loads are connected to each other.

The interconnection system allows the distribution of electricity through high, medium and low voltage transmission networks. High-voltage transmission networks are called extra-high-voltage overhead power lines (SUTET). On Java, the power lines with a capacity of 150 kV are in the north and those with a capacity of 500 kV are in the south.

The extra-high-voltage substation (GITET) functions as a transmission subsystem. The existence of the substation serves to transform electrical power from extra-high voltage (500 kV) to high voltage (150 kV) and from high voltage to medium voltage (70 kV/20 kV).

The reliability of the interconnection systems is determined by the interoperability (inter-component coordination mechanisms) in each component, the generators, networks, subsystems and loads, as well as in the stable operation of the interconnect system, sufficient transfer capacity and sufficient power supply.

The interconnection system has been implemented in a number of countries, including in Europe. According to electricity observers from Gadjah Mada University, Tumiran, the interconnection guarantees efficiency and reliable supply. For example, if one generator is interrupted, another plant can supply power.

Weaknesses

However, Fabby said there are weaknesses in the interconnection system because of the complexity of the system, which consists of various components and interactions between the various components. That gives the interconnection system a risk of disruption.

To prevent power outages, the distance between the medium voltage transmission lines and trees or buildings below them must be far enough to prevent disruption. Infrastructure security needs to be guaranteed and the operational capability of the transmission network and generating capacity must be maintained.

In addition, the electricity network must be able to distribute, send and receive power. Tumiran emphasized the importance of security coordination so that if there are disturbances, the system can sort out which must be removed from the system so it does not expand.

In addition, technical maintenance must be routinely carried out and there must be a security plan for when there is a supply disruption. So there is a layered backup operating system that considers reliability and fast response, not only paying attention to operational cost efficiency.