No abstract

Stability is one of the requirements of an electrical power system which can be considered good/ideal, One disturbance that can affect stability is the outage of the system generator. To overcome this problem, load shedding is performed, The load is released in a simulation aimed at bringing the frequency back to the authorized value after the disturbance has occurred. The power plant that experienced a trip in this study was the largest Lampung unit of the generator Tarahan 4. When the generator Tarahan 4 has been tripped, the frequency system is falls and stabilize at 48.8 Hz. Thereforeits necessary to release the load so that the system frequency returns to the authorized value, which is from 49,8 Hz to 50.2 Hz. Based on the results of simulation after setting the frequency relay, by releasing a load of 152.2 MW, the frequency was stable at 50.074 Hz. So it can be concluded that the frequency relay setting has been able to return the system frequency to allowable value.

Relai Rate of Change of Frequency (ROCOF) bekerja berdasarkan kecepatan perubahan frekuensi (df/dt) yang merupakan indikasi langsung dari ketidakseimbangan beban dengan pembangkit pada sistem. Dengan karakteristik ini pemanfaatan relai ROCOF sebagai relai pelepasan beban sangat menjanjikan. Pada penelitian ini bertujuan untuk menganalisa kemampuan skema relai ROCOF untuk pemanfaatan sebagai relai pelepasan beban frekuensi rendah. Skema relai ROCOF yang diusulkan terdiri dari lima tahap pelepasan dan disupervisi oleh relai frekuensi untuk mencegah maloperasi pelepasan beban saat kejadian hubung singkat. Skema relai ROCOF diuji melalui simulasi pelepasan pembangkit dengan kontingensi N-1, N-2 dan N-2-1. Simulasi dilakukan menggunakan Digsilent Powerfactory dan dibandingkan dengan skema UFR. Untuk kontingensi N-1 dan N-2, hasil simulasi menunjukkan skema relai ROCOF dapat mengembalikan frekuensi ke nilai yang lebih baik dan dalam waktu yang lebih cepat dari pada skema UFR. Namun terdapat permasalahan dalam pengaturan sensitifitas relai ROCOF melalui setting delay waktu. Untuk kondisi kekurangan pembangkitan ringan dan sedang dibutuhkan setting delay yang cukup besar untuk memperoleh nilai df/dt yang sebenarnya dari nilai df/dt yang cenderung berosilasi. Namun untuk kekurangan pembangkitan yang parah, setting delay yang besar menyebabkan relai menjadi kurang sensitif sehingga sebagian kecil relai tidak bekerja pada semua tahap yang diharapkan.

No abstract

The reliability of power distribution of PT PLN (Persero) branch of Padang especially in Rayon Tabing most of the repeaters is still not optimal. This is due to an uncoordinated protection relay on each feeder. One effort made to improve the reliability of electric power is to rearrange the protection of overcurrent relays and ground disturbance relays on the feeder. So coordinated with each other well and is expected if there is interference in one of the repeater will not bring black out on other repeater.In this research we analyzed short circuit current at 20 kV side. From the analysis results obtained new relay protection settings based on the calculation of short-circuit current settings and compare the results with existing protection relays. By making efforts to improve the reliability of electric power is to rearrange the protection relay on each feeder. Based on short circuit current analysis on each repeater, the largest short circuit in 3 phase, 2 phase, and 1 phase disturbance is located at 1% disturbance location and the smallest disturbance is at 100% disturbance location. It can be concluded that the farther the location of the disturbance that occurs the smaller the disturbance, and vice versa, if the location of the disturbance that occurs closer then the greater the noise flow.