Fault Tree-Based Root Cause Analysis Used to Study Mal-Operation of a Protective Relay in a Smart Grid

This chapter presents how root cause analysis based on fault tree technique can be used to study mal-operation of protective relay in a smart power grid. This approach is used to identify disturbances first and root cause of mal operation of protective relays which may lead to unnecessary tripping and hence to blackout. Once the critical root causes are identified, mitigation measures first such as blocking protection functions and digital filters may be used in view of increasing the reliability of the considered protection system. The proposed approach has many advantages as it allows obtaining an important quantitative figure (security). These permits to strongly strengthen the elements of the protecting system which are most likely appropriate to failure and hence the impact on the overall system's cost is significant. Another main advantage is that it takes into account the reliability of the software part of the system which is considered to have a significant contribution in the overall reliability of the protecting system.

Identifikasi Pemborosan Aktivitas di Lantai Produksi PSR Menggunakan Process Activity Mapping dan Waste Assessment Model

Salah satu produsen ban terbesar di Indonesia dalam proses produksinya memiliki beberapa family produk seperti Passenger Tires, Commercial Tires, dan Industrial Tires. Passenger Tires atau PSR merupakan family produk dengan penjualan terbesar, akan tetapi dalam perkembangannya terdeteksi adanya penurunan performa produksi yang mempengaruhi optimalisasi penjualan perusahaan. Berdasarkan studi pendahuluan teridentifikasi adanya beberapa aktivitas pemborosan di lini produksi ban PSR. Mapping aktivitas bertujuan untuk menemukan jenis waste yang tepat pada setiap departemen produksi maupun workstation. Mapping dilakukan dengan menggunakan diagram Swimlane dan Process Activity Mapping (PAM). Hasil mapping mengidentifikasi aktivitas yang tidak memberikan nilai tambah dengan persentase aktivitas sebesar 48%. Waste assessment model (WAM) dipakai untuk menentukan peringkat seven waste. Dari hasil analisis dengan menggunakan metode WAM diperoleh tiga waste kritis utama yaitu waiting, motion, dan overproduction dengan proporsi masing-masing waste sebesar 22%, 18%, dan 16%. Setelah diketahui waste kritis maka dilakukan analisis akar masalah penyebab waste dengan menggunakan fishbone chart diagram dan root cause analysis.