International Journal of Engineering Inventions e-ISSN: 2278-7461, p-ISSN: 2319-6491 Volume 11, Issue 10 [October. 2022] PP: 186-197 www.ijeijournal.com Page | 186 ImprovedProtectionon162MVA, 330/132kV Power Transformer in Afam IV Transmission Station Atebor Mohammed Zuberu, Prof. D. C. Idoniboyeobu, Dr. S. L. Braide. ElectricalEngineeringDepartment, RiversStateUniversity, Port-Harcourt, Nigeria. ABSTRACT: This work is based on improved protection on 162 MVA, 330 kV/132 kV power transformer in Afam IV transmission station. This is achieved by using Differential Protectionin determining the overcurrent, Restricted Earth Fault (REF).Electrical Transient Analyzer Program (ETAP) is used for the simulation. The result shows that the three (3) phase fault outside the differential relay protection zone on the primary side of the 162MVA power transformer did not penetrate inside the primary side of the transformer and so, the relay did not operate. The three (3) phase fault within the differential relay protection zone on the primary side of the 162MVA power transformer shows that the fault penetrates inside the primary side of the transformer and so, the relay operates.The three (3) phase fault within the differential relay protection zone on the secondary side of the 162MVA power transformer shows that the fault penetrates inside the secondary side of the transformer and thus, the relay operates. The three (3) phase fault outside the differential relay protection zone on the secondary side of the 162MVA power transformer indicates that the fault did not penetrate inside the secondary side of the transformer therefore, the relay did not operate. Differential relay has the inherent ability to differentiate between through-fault and internal fault current, the protection operational time (0.03s) and the coordination inside the differential relay protection zone. The simulated network of Afam IV transmission station network worked optimally without fault when the differential relay protection of the 162MVA power transformer is established through the application of the differential current as the difference between the primary side current and the secondary side current of the 162MVA power transformer. Key Words: Improved, protection, 162MVA, 330/132kV, transformer, Afam IV, transmission station. --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 15-10-2022 Date of Acceptance: 31-10-2022 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Power transformers are one of the most important equipment in power systems that are subjected to faultssimilar to any other component of the power system, thus transformer protection is of critical importance since they are indispensable element of power system. According to [1], power transformer which is also called backbone of the power transmission systems, high reliability of the transformer is therefore essential to avoid disturbances in transmission of power. Transformer has an important role to play in the power system where it may be used to level up the voltage for transmission, distributing the energy to consumers, it has to live long and operate stably [2].The transformers in high voltage networks are always protected by one main protection device and at least one back-up protection device[3]. The major concern in power transformer protection is to avoid mal-operation of protective relays due to transient phenomena including magnetic inrush current, simultaneous inrush with internal fault and external faults with current transformer (CT) saturation. The main problem in the degradation of life of transformer is the degradation of insulation in the transformer, it happens in the transformer because of several factors, some of them are included in electrical stresses and thermal stresses. These are voltage level, harmonics, use of power electronic devices, evolution of gasses, heating, water content etc. The insulation used for the transformer may be inorganic and organic, dry or oil insulation, or solids insulation which include concrete blocks, spacers etc. Life of the transformer depends upon the condition of insulating material [4]. About 10% of the faults take place inside the transformers and 70% of these faults are caused by short circuits in the windings [5]. According to [6],when a fault occurs in a transformer, the damage is proportional to the fault time. The transformer should therefore be disconnected from the network as soon as possible. In the view of [7], the impact of a transformer fault is often more serious than a transmission line outage. [8] say that to prevent faults and to minimize the damage in case of a fault, transformers are equipped with both protective relays and monitors. According to [9], the choice of protective