<p><em>A power transformer is electrical power equipment that works to transmit power or electrical power from high voltage to low voltage or on the contrary. In the operation of distributing electricity, the transformer can be said to be the heart of transmission and distribution. In this condition, a transformer is expected to operate optimally according to its function.. If the isolation state of the transformer deteriorates, it can have an impact on operating failure and the most fatal of which is that the transformer is damaged which can cause disturbances in the electrical system. To overcome this, it is necessary to analyze the isolation resistance.</em></p><p><em>This study analyzes the isolation resistance on a transformer using the polarization index, tangent delta and oil breakdown voltage methods to determine the quality of the isolation on the transformer. This study took data at the 150 Kv substation Tegal. The data used include polarization index test data, tangent delta data, bottom oil breakdown voltage test data, and OLTC oil. After the data is obtained, then calculations and analyzes are carried out to obtain accurate results.</em></p><p><em>The test results at the 150 Kv substation Tegal showed the polarization index value with the lowest IP of 1.26 in the primary-ground section and the highest IP of 1.97 in the primary-secondary section is still in good condition. The results of the tangent delta test are still in good condition, only in the CHT mode experienced a negative delta tan deterioration of 0.07%. The result of the average oil test is still suitable for use with 69.9 Kv of bottom oil and 53.3 Kv of OLTC oil.</em></p>

<p><em>  In the construction of multi-storey buildings, every aspect must be considered in accordance with the rules set out in the Act. Article 7 Paragraph 3 of Law 28/02 states that building construction must meet four aspects, namely safety, health, comfort, and convenience. To support the realization of these aspects, it is necessary to have a building utility. The Joint Lecture Building (GKB) of Sultan Agung Islamic University in Semarang, is a building that has 10 floors and is a busy building because it is used by several faculties, such as the PGSD Faculty, Language Faculty, Communication Faculty, and Nursing Faculty. In the operation of the GKB building, there are several complaints that occur in the GKB such as electricity that often goes out, some rooms have less lighting / dark, queues of elevator users are piling up and visually, the GKB building has the potential of being struck by lightning because it has high above average.</em></p><p><em>Seeing these conditions, the authors conducted a study to evaluate the reliability of buildings based on the utility of the building with methods that have been used in other studies, namely the scoring method that is based on visual inspection and by adding measurement methods, and calculations. From these results found the reliability value of the GKB building on the criterion of health scores got a score of 81, the health and comfort criteria scored 99, the ease criterion scored a score of 98. So the reliability of the GKB building got a score of 92 and was included in the unfit category.</em></p>

<p>The use of electricity with large capacity sometimes faces various kinds of problems. These problems include network losses and voltage drops that occur in the channel. Improvement of electric power factor at PT. Karya Toha Putra is expected to improve the quality of electric power. This improvement is also expected to reduce the cost of electricity bills at PT. Karya Toha Putra. To be able to implement improvements in the quality of the electric power, it is necessary to calculate the reactive power compensated. In this case the power factor to be achieved is 0.95. After doing these calculations, the determination of the capacitor value will be used. By doing these stages, it is expected that the installation of capacitor banks can improve the quality of electric power. Bank capacitors are collections of capacitors used to provide reactive power compensation to improve the electrical power factor. From the results of the study showed that the amount of compensation needed to improve the power factor at PT. Karya Toha Putra is 50 kVAR, divided into 5 steps with one step, a capacitor of 10 kVAR.</p>

<div class="WordSection1"><p align="center"><em>According to energy observers from the Institute for Essential Services Reform (IESR) the number of electricity consumers in Indonesia has increased by an average of 6-7% annually followed by an increase in the area of its services.</em><em> An increasingly broad network is directly proportional to the potential for interference with the transmission and distribution system. The 150 KV Rembang substations is part of the Java-Bali Interconnection electrical system in northern Central Java that supplies electricity to the Rembang and surrounding areas. Rembang 150 KV substation on May 24, 2019, RBG 01 feeder experienced a disturbance behind the RB1-32 recloser and it was recorded that in 2019 PMT it had been tripped 4 times. Besides, there has been a change in equipment in the form of transformer II. These problems indicate the potential for interference that is not anticipated by the protection system, namely Over Current Relay and recloser.</em><em>  This study evaluates the setting of an outgoing 20 KV OCR protections and recloser on transformer II RBG 01 feeder Rembang 150 KV substation. The scenarios used are calculations with large variations of short-circuit current based on% distance, as well as the calculation of OCR and recloser settings with IEC 60255 standards. Setting currents in the protection equipment is regulated based on current conductivity (KHA) and load current on the recloser. The coordination of the protection settings resulting from this resetting will be compared to the conditions on the ground.  </em><em>Existing (field) OCR outgoing feeder RBG 01 condition TMS OCR value = 0.228 seconds, Iset = 480 A, and t op = 0.3 seconds. The existing OCR recloser condition TMS OCR value = 0.120 seconds and Iset = 400 A. The results of OCR coordinating outgoing feeder RBG 01 obtained TMS OCR value = 0.135 seconds, Iset = 585 A, and t operation = 0.3 seconds. OCR recloser resetting conditions obtained TMS OCR value = 0.10 seconds, Iset = 240 A and t operation = 0.198 seconds. The resetting conditions have met the IEC 60255 standard because recloser working time is smaller than outgoing work time.</em></p></div>