ANALISIS GANGGUAN LISTRIK DI PLTU NAGAN RAYA MENGGUNAKAN DIAGRAM KENDALI EXPONENTIALLY WEIGHTED MOVING AVERAGE DAN DECISION ON BELIEF

Abstract

Electricity production quality can be measured and controlled using statistical methods, namely control charts.  Exponentially Weighted Moving Average (EWMA) control chart analyzes the state of quality control system using attribute and variable data, whereas Decision On Belief (DOB) control chart uses univariate attribute data.  Monthly data on electricity disturbances counts at PLTU Nagan Raya, Aceh during 2018-2020 is used in this study.  Shutdown losses of 326 times was the most common type of disturbance at PLTU Nagan Raya during this period.  Factors that affect disturbances are material, methods, environment, equipment, and human error.  Using the EWMA control chart, there was one point below the lower control limit, i.e. at point 3; whereas there were two points below the lower control limits at points 2 and 3 when DOB control chart is used.  This shows that the power disturbance data at PLTU Nagan Raya have not been statistically controlled.  Using the Fisher exact test, a p-value of 1 shows that there was no significant difference between the EWMA and DOB control charts in detecting data outside the control limits. The ARL EWMA value of 2.2539 means that on average, EWMA control chart can detect the first uncontrollable condition at point 2.2539.