Relai REF (Restricted Earth Fault) digunakan sebagai peralatan pengaman dari gangguanhubung singkat satu phasa ke tanah, agar arus gangguan tidak mengalir ke titik netral trafo saatputusnya kawat NGR (Neutral Ground Resistor). Arus hubung singkat satu phasa ke tanahsebelum putusnya Pengawatan NGR sebesar 288,67 Ampere, sedangkan arus hubung singkatsesudah putusnya Pengawatan NGR sebesar 884,15 Ampere. Hasil analisis pemasangan relaiREF pada trafo 60 MVA terhadap gangguan hubung singkat satu phasa ke tanah saat putusyapengawatan NGR mempunyai kemampuan proteksi yang baik berdasarkan dari perhitungansimulasi gangguan saat putusnya Pengawatan pentanahan NGR, dengan arus hubung singkatsebesar 884,15 Ampere, maka besar arus yang mengalir pada relai REF sebesar 0,263Ampere, sedangkan relai REF di setting pada 0,233 Ampere, maka dapat di pastikan relai REFsudah bekerja, karena waktu kerja relai REF adalah 0 detik atau tanpa waktu tunda.

Monitoring temperature and humidity in cold storage is very important to prevent damage to food raw materials. Checking the temperature in the cold storage is carried out every 4 hours with the results manually written on the log sheet by the working staff and also sometimes there are staff who do not close the cold storage door tightly so that it causes an increase in temperature. Therefore an IoT-based cold storage temperature monitoring system is created using Wemos D1 R2 in real time which is very necessary. The design of this prototype uses hardware, namely the WeMos D1 R2 microcontroller because it is based on ESP8266 which can be connected to WiFi, DHT22 temperature sensor, and HC-SR501 PIR sensor. The software used is blynk and google spreadsheet. The results of this prototype design are being able to read the cold storage temperature and humidity properly which can be seen in the blynk application on a smartphone by displaying the temperature and humidity values. This prototype also has a feature that sends notifications to smartphones when the temperature is read more than 5°C and has temperature data stored on Google spreadsheets. The conclusion of this study has succeeded in designing and making a prototype of an IoT-based cold storage temperature monitoring system. The testing of the prototype can work well. The results of applying the prototype to cold storage Room 21 obtained an average temperature of 2.9°C and an average humidity of 86%.

Gangguan 1 fasa ke tanah dapat menyebabkan terjadinya gangguan sympathetic trip yang menimbulkan arus urutan nol (arus residu) pada fasa yang terganggu. Penyulang yang memiliki sistem jaringan paralel seperti penyulang Ngurah Rai I dan Ngurah Rai II sangat rentan terjadinya gangguan sympathetic trip, karena relay GFR (Ground Fault Relay) pada penyulang Ngurah Rai I dan Ngurah Rai II tidak bisa mengamankan gangguan tersebut, maka untuk mengatasi gangguan  sympathetic trip pada penyulang Ngurah Rai I dan Ngurah Rai II pemasangan relay DGR (Directional Ground Relay) akan mencegah terjadinya gangguan tersebut, dan sistem keandalan penyulang Ngurah Rai I dan Ngurah Rai II tetap terjaga. Hasil analisis perhitungan relay DGR untuk menangani gangguan sympathetic trip didapatkan besar nilai setting relay yaitu = 9.334 A, SI, Waktu trip Arus gangguan t = 0.297, ZCT = 1 A, GPT = 34.64 kV. Jadi untuk mengatasi gangguan sympathetic trip, relay DGR sangat diperlukan jika jaringan atau penyulang beroprasi secara loop dan letaknya berdekatan satu bus.

The use of distance relays in the system SUTT 150 kV network, is expected to help the reliability of the transmission system. Setting the value of the distance relay network systems SUTT 150 kV GI Kapal-GI Pemecutan kelod specified by PLN, to do research to obtain the new distance relay settings. Value setting relays within the network system SUTT 150 kV GI Kapal-GI Pemecutan kelod: Zone 1: (R = 0.977, X = 2.684, Z = 2.86), Zone 2: (R = 1.341, X = 3684, Z = 3.92), zone 3: (R = 2,107, X = 5789, Z = 6.16). Methods used to determine the return value of the distance relay settings for securing network systems SUTT 150 kV GI Kapal-GI Pemecutan kelod is a method of Artificial Neural Network. Application of the method backpropagation Artificial Neural Network is used to determine the value of setting relays within the network system SUTT 150 kV GI Kapal-GI Pemecutan kelod obtained from the method of Artificial Neural Network is zone 1

Short circuit causing over current problem and can might causing interference of the equipment performance such as distribution transformers also causing widespread disruption occurred. In resolving such interference is required as protection system on the distribution system. Seeing all above is needed coordination between the supporting component of the protection system which is consisted of Over Current Relay (OCR) and Ground Fault Relay (GFR). The research was conducted at PT. PLN (Persero) South Bali Area Network, INDONESIA on recloser in the feeder line of Penebel. OCR setting between the Relay feeder of Penebel, Recloser Celagi, Recloser Bakisan, and Recloser Benana still less selective, with time value coordination between average security was still less than 0,2 second. Then OCR setting and GFR relay feeder of Penebel, Recloser Celagi, Recloser Bakisan, and Recloser Benana was recommended for re-setting in order to minimize disruption and electric power distribution system to be reliable.