REPORT ON STUDENT INDUSTRIAL WORK EXPERIENCE SCHEME (SIWES) AT Transmission Company of Nigeria (TCN), 330/132/33kV, Ganmo Works Centre PMB 1463, Afon Road, Ganmo, Kwara State Email: pmtganmowc@yahoo.com Website: www.tcn.ng.org BY TAOFEEQ OLAWALE, SA’AD 14/67EC/552 Electrical and Computer Engineering, College of Engineering and Technology, Kwara State University, Malete. Being a report submitted to the SIWES unit, Kwara State University, Malete, Nigeria, in partial fulfilment of the requirements for the Student Industrial Work Experience Scheme (SIWES). August, 2018 DEDICATION To my wonderful mother, who taught me that even the largest task can be accomplished if it done one step at a time ii ABSTRACT This report is based on Student Industrial Work Experience Scheme (SIWES) held at Transmission Company of Nigeria (TCN), Ganmo Work Centre, Afon road, Kwara. It gives brief explanation about the SIWES program vis-à-vis its history, objectives and aims, while also provides a brief description, roles and functions of TCN Ganmo Work Centre. It further focuses more on the technical exposure and experience gained from various departments such as Electrical Maintenance Department (EMD), System Operation Department (S/O) and Protection, Control and Metering Department (PC&M) at TCN Ganmo Work centre. It finally gives an account of the equipments used; types and their function respectively as well as some of the problems and challenges faced and provide recommendations that can further improve the program. iii ACKNOWLEDGEMENT All praise and adoration is to God Almighty my creator, my strong pillar, my source of inspiration, wisdom, knowledge and understanding. He has been source of my strength throughout this program. I owe thanks to my parents for their unwavering support, co-operation, encouragement and understanding throughout the span of this programme and many other close friends and family members. I have taken effort in this report. However, it would not have been possible without the kind of roles played by all the technical staffs of TCN Ganmo for their relentless supports, guidance, constant supervision and explanation of work(s) done despite the fact that the work was so hectic. Other members of staff of TCN Ganmo who contributed in one form or the other are deeply appreciated and to the people who have willingly helped me out with their abilities and resources. I would like to extend my sincere thanks to all of them My appreciation also goes the Principal Manager Engr. K. O. Adelakun and to HODs of the departments I visited; A.A. Adetoyinbo (Electrical Maintenance Department), S. K. Ibukun (System Operation), R. A. Odemakinde (Protection Control and Metering Department) respectively. Finally, I wish to express my sincere appreciation R.A Odemakinde and to all the staff of PC&M department for their care, support, understanding and hospitality while the course lasted you are wonderful to me. Thanks iv DECLARATION I hereby declare that, I from Electrical and Computer Engineering Department, College of Engineering and Technology, Kwara State University, Malete, Nigeria underwent the six months Students Industrial Work Experience Scheme (SIWES) at Transmission Company of Nigeria(TCN), Ganmo Works Centre, PMB 1463, Afon Road, Ganmo Kwara State, from 22nd of January to 6th July 2018. I also declare that to the best of my knowledge, all sources of knowledge used have been duly acknowledged. --------------------------------------Taofeeq Olawale, SA’AD 14/67EC/552 v TABLE OF CONTENTS TITLE PAGE DEDICATION ABSTRACT ACKNOWLEDGEMENTS DECLARATION i ii iii iv v CHAPTER ONE: THE SIWES 1.1 INTRODUCTION 1 1.2 OBJECTIVES 2 1.3 IMPORTANCE OF SIWES 2 CHAPTER TWO: TRANSMISSION COMPANY OF NIGERIA (TCN) 2.1 POWER SYSTEM IN NIGERIA 3 2.2 ABOUT TRANSMISSION COMPANY OF NIGERIA (TCN) 4 2.2.1 VISION AND MISSION 4 2.2.2 SCOPE OF ACTIVITIES 5 2.3 BRIEF HISTORY OF TCN GANMO WORKS CENTRE 5 2.4 THE ORGANIZATIONAL STRUCTURE OF TCN, GANMO 6 2.5 THE DEPARTMENTS AT TCN, GANMO AND THEIR FUNCTIONS 7 2.6 THE POSTED DEPARTMENTS AT TCN, GANMO 9 CHAPTER THREE: THE WORK DONE AND WORKs EXPERIENCE 3.1 INTRODUCTION 11 3.2 ELECTRICAL MAINTENANCE DEPARTMENT (EMD) 11 3.2.1 MATERIALS AND EQUIPMENT USED 12 3.2.2 WORK DONE AND EXPERIENCE GAINED 13 3.2.2.1 Battery Bank Maintenance 13 3.2.2.2 Switchyard Lightning 14 3.2.2.3 Troubleshooting of Ganmo/Osogbo/Offa/Omu-Aran 132kV Line Circuit Breaker 14 3.2.2.4 Rehabilitation of Red and Yellow phase of Oshogbo/Ganmo 330kV circuit breaker 15 vi 3.2.2.5 T2A 150MVA 330/132/0.415KV Grounding Transformer II Panel 3.3 SYSTEM OPERATION DEPARTMENT 16 17 3.3.1 MATERIALS AND TOOLS USED 18 3.3.2 WORK DONE AND EXPERIENCE GAINED 19 3.4 PROTECTION CONTROL AND METERING PC&M DEPARTMENT 20 3.4.1 MATERIALS AND EQUIPMENT USED 21 3.4.2 WORK DONE AND EXPERIENCE GAINED 21 3.4.2.1 Carrier Signaling Test 22 3.4.2.2 Installation of Current Transformer (CT) at Omu-Aran T/S: 23 3.4.2.3 Schedule Maintenance of T2A 150MVA 330/132/0.415kV diverter switch 27 3.4.2.4 Installation of Digital multimeter on 33kV OLAM feeder in Ganmo W/C 28 3.4.2.5 Installation of EDMI MK6 Energy Meter 2000-6EXX Series on 33kV OLAM feeder 29 3.4.2.6 Pre-commissioning test of transformers at KAM 132kV Substation at Jimba Oja 30 3.4.2.7 Comprehensive test on 33kV Feeder 5 CTs at Ganmo W/C 37 3.4.2.8 Protection trip and Calibration test on 33kV Feeders at Ganmo Work Centre 38 CHAPTER FOUR: THE EQUIPMENT 4.1 Introduction 40 4.2 AUTO-TRANSFORMER AND ITS FUNCTIONS 40 4.2.1 Introduction 40 4.2.2 Function of Auto-Transformer 41 4.2.3 Usages of Auto-Transformer in TCN Ganmo Works Centre 41 4.3 OMICRON CPC 100 + CP TD1 42 4.3.1 Introduction and application 42 4.4 INSTRUMENT TRANSFORMERS 43 4.4.1 Introduction 43 4.4.2 Types of Instrument Transformers Used in TCN Ganmo Works Centre 43 4.4.3 Functions of Instrument Transformers 43 4.4.4 Usages of Voltage Transformer (VT) and Capacitor Voltage Transformers (CVT) 43 4.4.5 Usages of Current Transformer (CT) 44 vii 4.5 CIRCUIT BREAKERS 44 4.5.1 Introduction 44 4.5.2 Functions of Circuit Breaker 45 4.5.3 Usages of Circuit Breaker 46 4.6 RELAYS 46 4.6.1 Introduction 46 4.6.2 Types, Functions and Usages of Relays 46 4.6.2.1 Voltage Sensitive Relay 46 4.6.2.2 Differential 47 4.6.2.3 Power (Phase) Sensitive Relay 47 4.6.2.4 Current Sensitive Relay 48 4.7 WAVE TRAP 49 4.7.1 Functions of Wave Trap 49 4.8 SECONDARY CURRENT INJECTION TEST SET 50 4.8.1 Functions of Secondary Current Injection Test Set 50 4.8.2 Usage and/or Application Secondary Current Injection Test Set 50 4.9 INSULATION RESISTANCE TESTER (MEGGER) 51 4.9.1 Introduction 51 4.9.2 Functions of Megger 51 4.9.3 Usage of Megger 51 4.10 LEAKAGE CURRENT TESTER (CLAMP ON) 52 4.10.1 Introduction 52 4.10.2 Functions of Clamp On 52 4.10.3 Usage of Leakage Current Tester 52 4.11 EARTHING TRANSFORMER AND EARTH REACTOR 52 4.11.1 Introduction 52 4.11.2 Functions and Usages of Earthing Transformer 52 4.12 SCADA SYSTEM 53 4.12.1 Functions and Usages of SCADA System 53 4.12.2 Applications or Usages of SCADA System 54 viii 4.12.3 Feeder Control using SCADA 56 CHAPTER FIVE: SUMMARY, CONCLUSION AND RECOMMENDATIONS 5.1 SUMMARY AND CONCLUSION 57 5.2 PROBLEM FACED DURING THE SIWES 57 5.3 SUGGESTION FOR IMPROVEMENT OF THE SCHEME 58 REFERENCES 59 APPENDIX I: GLOSSARY A APPENDIX II: LIST OF RESULTS C APPENDIX III: PICTURE GALLARY M ix SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 CHAPTER ONE: THE SIWES 1.1 INTRODUCTION The Students Industrial Work Experience Scheme (SIWES) is the accepted skills training programme, which forms part of the approved minimum Academic Standards in the various degree programmes for all the Nigerian Universities. It is funded by the Federal Government of Nigeria and jointly co-ordinate by the Industrial Training Fund (ITF) and the National Universities Commission (NUC) [1]. It is also designed to expose and prepare students of Universities, Polytechnics, Colleges of Technology, Colleges of Agriculture and Colleges of Education for the industrial work situation they are likely to meet after graduation. The scheme also affords students the opportunity of familiarizing and exposing themselves to the needed experience in handling equipment and machinery that are usually not available in their Institutions. Before the establishment of the scheme, there was a growing concern among our industrialists that graduates of our Institutions of higher learning lacked adequate practical background studies preparatory for employment in Industries. Thus, the employers were of the opinion that the theoretical education going on in higher institutions was not responsive to the needs of the employers of labour. It is against this background that the rationale for initiating and designing the scheme by the Industrial Training Fund (ITF) during its formative years – 1973/74 was introduced to acquaint students with the skills of handling employers’ equipment and machinery. The ITF solely funded the scheme during its formative years. But as the financial involvement became unbearable to the Fund, it withdrew from the Scheme in 1978. The Federal Government handed over the scheme in 1979 to both the National Universities Commission (NUC) and the National Board for Technical Education (NBTE). Later the Federal Government in November 1984 revert the management and implementation of the SIWES Programmed to ITF and it was effectively taken over by the Industrial Training Fund in July 1985 with the funding being solely borne by the Federal Government [2]. 1 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 1.2 OBJECTIVES Specifically, the objectives of the Students Industrial Work Experience Scheme (SIWES) are to: Provide an avenue for students in institutions of higher learning to acquire industrial skills and experience in their course of study, which are restricted to Engineering and Technology including Environmental studies and other courses that may be approved. Courses of NCE (Technical), NCE Agriculture, NCE (Business), NCE (Fine and Applied Arts) and NCE (Home Economics) in Colleges of Education are also included. Prepare students for the industrial work situation they are to meet after graduation. Expose students to work methods and techniques in handling equipment and machinery that may not be available in their institutions. Make the transition from school to the world of work easier, and enhance students’ contacts for later job placement. Provide students with an opportunity to apply their knowledge in real work situation thereby bridging the gap between theory and practice. Enlist and strengthen employers, involvement in the entire educational process and prepare students for employment in Industry and Commerce. Provide students the opportunity to develop attitudes conducive to effective interpersonal relationships. Ernest placement and strengthen employees involvement in the educational process of preparing student for employment in industries [2, 3]. 1.3 IMPORTANCE OF SIWES It provides students with an opportunity to apply their theoretical knowledge in real life situations. It exposes students to more practical work methods and techniques. It strengthens links between the employers, universities and industrial training fund (ITF). It also prepares the students for the labour market after graduation [3]. 2 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 CHAPTER TWO: TRANSMISSION COMPANY OF NIGERIA 2.1 POWER SYSTEM IN NIGERIA When we press switch electricity come on, appliances work and large industries manufacture products. Have we ever wondered how this is done? There are actually processes involved in getting electricity to our homes and offices. This has to do with the processes involved in Generation, Transmission and Distribution of power in Nigeria as shown in the figure below. Figure 1: Process involved from power generation to distribution [4] a) GENERATION: In Nigeria, Electricity production over the last 40years has varied from gas-fired, oil fired, hydroelectric power stations to coal fired stations with hydroelectric power systems and gas fired systems taking precedence. Electricity is generated at between11.5–16kV and stepped up by a step-up transformer to 330kV at the Power stations. This is done so as to take care of power losses (I2R losses) along the line of transmission since the electricity generated is to be transmitted over long distances. Power generated at various generating stations in the Nation is connected to the National Grid and then transmitted. b) TRANSMISSION: The next phase of getting power to the consumer is Transmission. Transmission begins with the transportation of voltage, 330kV along transmission lines ( otherwise referred to as conductors) and is stepped down by a transformer to 132kV at 3 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 the Transmission substation, this voltage is further transported along transmission lines to Injection substations and stepped down to 33kv c) DISTRIBUTION: Distribution of electricity starts at this point. The voltage is stepped down by a distribution transformer to 11 kV which in turn is stepped down to 0. 415kV and further stepped down to 240V before it gets to our homes or offices [4]. 2.2 ABOUT TRANSMISSION COMPANY OF NIGERIA (TCN) Transmission Company of Nigeria (TCN) manages the electricity transmission network in the country and was incorporated in November, 2005. TCN emerged from the then National Electric Power Authority (NEPA) as a product of the merger of Transmission and Operations Sectors in April 1, 2004. Being one of the 18 unbundled Business Units under Power Holding Company of Nigeria (PHCN), the company was issued a Transmission license on 1st of July, 2006 [6]. TCN is presently fully owned and operated by the government and as part of the reform programme of the government, it is to be reorganized and restructured to improve its reliability and expand its capacity. The Transmission Company of Nigeria (TCN) Ganmo Works Centre was the station where this attachment was conducted. It is located along Afon Road, Ganmo, Kwara State. It is headed by the Works Centre Principal Manager PM (T), Engr. K.O Adelakun and the Centre is under the Osogbo region. TCN’s licensed activities include: electricity transmission, system operation and electricity trading. It is responsible for evacuating electric power generated by the electricity generating companies (GenCos) and wheeling it to distribution companies (DisCos). It provides the vital transmission infrastructure between the GenCos and the DisCos’ Feeder Sub-stations [5]. 2.2.1 VISION AND MISSION The Company’s vision is to be “a Transmission Company with a solid reputation for delivering reliable, cost-effective Electric power to end users in Nigeria and in West Africa Sub-region”. Its mission statement is “to cost effectively provide, operate and maintain the 4 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 required assets, equipment and transmission grid network for evacuating and dispatching high quality Electricity with minimal losses” [7]. 2.2.2 SCOPE OF ACTIVITIES Activities carried out by TCN include: Electricity transmission, System operation, and Electricity trading which is ring-fenced. Its major function is to collect generated Electric Power from Generating Companies and wheel it to Distribution Companies. TCN comprises of nine Transmission Regions and the National Control Centre (NCC), viz: Bauchi, Kaduna, Shiroro, Benin, Osogbo, Enugu, Lagos, Kwara and Port Harcourt [7]. 2.3 BRIEF HISTORY OF TCN GANMO WORKS CENTRE Transmission Company of Nigeria, Ganmo was commissioned by late President Umar Musa Yar’adua GCFR under the administration of Dr. Bukola Saraki, Kwara State Governor. The Ganmo Works Centre was commissioned on 27th of July, 2009 after about two years of construction. It comprises of the switch yard see Appendix III, control room see Appendix III and a block for offices. The commissioned was based on the insufficient power supply in the vicinity of the Kwara State and its laboring states. The Ganmo Works Centre is the Area Control Centre (ACC) and has two sub-transmission stations under its supervision; Ilorin Transmission station and Omu-Aran Transmission Station [7]. Transmission Company of Nigeria (TCN), Ganmo operating at 330/132/33kV, The TCN Ganmo is a substation under Oshogbo National Grid, it received High Voltage Alternating Current (HVAC) of 330kV from Jebba generating station (code name J3G) and Oshogbo National Grid station (code name H3G). TCN Ganmo step-down the 330kV to 132kV and 33kV, the 132kV are sent to substations under TCN Ganmo which are Transmission Company of Nigeria, Sawmill, Ilorin operating at 132/33kV abbreviated as Ilorin TS and Transmission Company of Nigeria, Omu-Aran operating at 132/33kV abbreviated as Omu-Aran TS. In each of the stations, the 33kV is now feeds to the districts or Distribution Companies as well as the special industries. 5 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 2.4 THE ORGANIZATIONAL STRUCTURE OF TCN, GANMO The organizational structure of TCN Ganmo is as below; Figure 2: organization structure of TCN, Ganmo Works Centre 6 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 2.5 THE DEPARTMENTS AT TCN, GANMO AND THEIR FUNCTIONS The TCN Ganmo is divided into units of various departments, namely; 1. Administration Department 2. Accounting Department 3. Protection Control and Metering (PC&M) Department 4. Electrical Maintenance Department (EMD) 5. Mechanical Department 6. System Lines Department 7. System Operations Department (SO) 8. Communication Department The functions of the departments above are as follow; ADMINISTRATION DEPARTMENT: provide essential administrative support to the executives and department managers (HODs) of the Transmission Company of Nigeria (TCN), Ganmo. With their computer, communication and data entry skills, administrative assistants are able to assist with both complex and general administrative duties, allowing their supervisors more time to carry out their managerial tasks. The department is responsible for data processing, file maintenance, communication and clerical of the TCN Ganmo. ACCOUNTING DEPARTMENT: the primary purpose of every accounting function is that of ongoing financial record keeping. Monetary information all types—operational expenses, salaries, donations, capital expenditures, investments, cash-flow, utilities all of which should be tracked on a monthly basis at a minimum. The ongoing result is the creation of the Transmission Company of Nigeria (TCN) financial history that can be used in a variety of ways, as it gives managers a snapshot of the firm’s financial health and wealth at any given time. PROTECTION CONTROL AND METERING (PC&M) DEPARTMENT: the function of the department is to maintain the electrical and electronics equipment, protects the life personnel and maintain and/or configure the metering equipment of the Ganmo Works Centre and the substations under the TCN Ganmo Works Centre. The PC&M department is 7 SIWES REPORT responsible for Taofeeq Olawale, SA’AD: 14/67EC/552 installations, commissioning and decommissioning, maintaining, troubleshooting and repairing the critical system used for detecting and responding to power system faults, controlling system devices, metering schemes and data voice transfer throughout the region/area that Transmission Company of Nigeria, Ganmo i.e. the substations under Ganmo Works Centre namely Transmission Company of Nigeria, Omu-Aran and Transmission Company of Nigeria, Ilorin both of which are operating at 132/33kV. ELECTRICAL MAINTENANCE DEPARTMENT (EMD): the department functions are to install, commissioning and decommissioning, troubleshoot, maintain, and protects the life of the equipment in the TCN Ganmo Works Centre and the two substations under the company which are TCN Omu-Aran and TCN Ilorin both operating at 132/33kV. The department and its crew are usually on the field doing the works. The department also maintains the wiring of the office blocks and control room. MECHANICAL DEPARTMENT: the department is responsible for the installation or mounting of breaker’s stands and Circuit Breakers itself, Current Transformers and Voltage Transformers stands and mounting on the switch yards either at Ganmo Works Centre or the substations (most especially the substations). The department also provides a reliable ways of transportation for the TCN Ganmo personnel and maintenance crew by means of maintaining the vehicles use by the company. SYSTEM LINES DEPARTMENT: the functions of this department are to maintain the transmission lines wires in a way of avoiding earth tripping from the feeder’s relay, maintaining the transmission lines poles, cutting the elongated trees that is disturbing the spaces between the transmission lines wire that cause the feeder to trip on earth fault. The department is also responsible for the tightening and maintenance of the lines conductors on the switch yards and repairing the hotspots identified by the operators on duties of the TCN Ganmo and its substations. SYSTEM OPERATION DEPARTMENT: manages the flow of electricity throughout the power system from generation to distribution companies. The SO has the responsibility for 8 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 ensuring that the transmission grid lines are reliable and maintaining the technical stability of the grid through its operations of planning, dispatch, and control of the electricity on the grid [5]. They are responsible for the functioning and monitoring the systems of the whole TCN Ganmo works center and protecting the equipment of the station by monitoring and operates the whole system which includes GENCOs and DISCOs i.e. decides which power station comes on and when and by how many Mega- Watts (MW), decides which transmission line or transmission station should be supplied what quantity of Mega-Watts (MW) i.e. load shedding and also enforce Grid discipline. COMMUNICATION DEPARTMENT: this department is responsible for sending and receiving information necessary for the operation of the station, monitor activities going on within the station and other activities outside the station that influencing it, helps to improve the quality of job done in and relating to the station, and the equipment and the control and protection scheme employ communication in order to function. 2.6 THE POSTED DEPARTMENTS AT TCN, GANMO The departments that I was posted to and the duties are as follow; Electrical Maintenance Department (EMD) where 5 weeks were spent and part of the responsibilities along with the maintenance crew is to: Carrying out schedule maintenance of power transformer of various ratings and capacities; Conduct insulation test, Dielectric strength test on transformer oil and circuit Breakers; Service, maintain and repair power circuit breakers such as oil circuit breaker, Sulphur hexafluoride (SF6) circuit breaker, and conduct insulation and performance test on same and maintenance of battery and charger; Carry out construction and installation works on a new substation as per the design and physical positioning of the substation equipment such as CBs, Transformers, Isolators as well as preparation and processing of monthly maintenance report etc. System Operation Department where 4 weeks were spent and part of the responsibilities along with the operators is to: Prepare and effect work and test permit 9 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 for maintenance staff; Maintain and effect voltage and frequency dispatch control of the grid system; Prepare and effect scheduled outages; Keep up to date record of the system’s parameters on hourly basis and relaying of all reports to the necessary quarters; Guaranteed safety of the maintenance staff and the equipment etc; Raise trouble report on defective equipment and operation to appropriate maintenance section and carrying out routine maintenance as well as daily inspection of all the equipment in the switchyard respectively etc. Protection Control and Metering (PC&M) Department where 16 weeks were spent and part of the responsibilities along with the maintenance crew is to: carry out Precommissioning tests on all power transformers, Circuit Breakers, Instrument transformers (CTs and VTs), Relays, Tripping Unit (Chargers and Battery banks); Design protection schemes for new installed transformers and feeders; Carry out all relay settings and coordination; Conduct Secondary and primary injection tests on all station protective relays; Carry out insulation tests, ratio test, polarity test, magnetization test on power and instrument transformers as well as processing of Daily Activity Report Chart (DARC), Monthly Progress Report (MPR), Schedule Annual Preventive Maintenance (SAPM), Key Performance Index (KPI) etc. 10 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 CHAPTER THREE: THE WORK DONE & WORKs EXPERIENCE 3.1 INTRODUCTION This chapter covers the discussion of the work done and the experience gained during the course of the training in each of the department visited or attached. The first and foremost most important experience gained is the important and very significant of safety because any single mistake makes at switch yard will leads to instant death by electrocution, there is no second chance of mistake at TCN because of the Very High Voltage dealing with. So emphasis and precautions were always taken before entering the switch yard to perform any kind of work done even for inspection purposes. One must be issue permit letter by the operator in charge before stepping into switch yard. The scope of work done and experience gained will be analyzed below on each of the department visited in order of visitation. 3.2 ELECTRICAL MAINTENANCE DEPARTMENT (EMD) The period spent in this department was 5 weeks (22nd January to 23rd February, 2018). The department is headed by A.A. Adetoyinbo as the Senior Manager (HOD). The Electrical maintenance department is responsible for all maintenance of equipment within the Area Control. There exist preventive maintenance and corrective maintenance. Preventive maintenance is procedures carried out on the equipment to ensure proper functioning and avoid breakdown. For example: changing of silica gel, filling of gas or changing of oil in a circuit breaker, transformer oil filtration, electrolyte topping in lead acid batteries et cetera. Corrective maintenance is a type of maintenance that is carried out to correct a problem on hand. For example: clearing of hotspot, changing of leaking gasket, changing of lightning bubs, changing of circuit breakers, bleeding of the transformer, et cetera. 11 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 3.2.1 MATERIALS AND EQUIPMENT USED The major materials and equipment that are employed during maintenance in this department are as follows: 1. Battery hydrometer: A hydrometer is used to test the state of charge of a battery cell. This is performed by measuring the density of the electrolyte, which is accomplished by measuring the specific gravity of the electrolyte. The greater the concentration of sulfuric acid, the more dense the electrolyte becomes 2. Grounding stick/lead and wire: this is used to provide a temporal ground for conductors that may be partially charged due to induction, around the working site to avoid electrocution. 3. High Voltage Insulation Resistance Tester (Megger): The Megger is the instrument uses for measuring the resistance of the insulation. It works on the principle of comparison, i.e., the resistance of the insulation is compared with the known value of resistance. If the resistance of the insulation is high, the pointer of the moving coil deflects towards the infinity, and if it is low, then the pointer indicates zero resistance. The accuracy of the Megger is high as compared to other instruments. 4. Funnel and Bucket: this is used during jobs that involve oil or battery electrolyte. 5. Hand Pump: this is used for pumping oil from drum to equipment (e.g. oil circuit breaker, current transformer, voltage transformer, conservator tank, et cetera 6. Hose: usually connected to the hand pump during oil jobs. 7. Gas kit: this contains the gas pipes and nozzles, for the purpose of filling or refilling Sulphur-hexa-fluoride (SF6) into power circuit breaker. 3.2.2 WORK DONE AND EXPERIENCE GAINED The scope of major work done as well as the experience gained at EMD includes the following: Ganmo Battery Bank Maintenance (two 110V and 50V DC). Switchyard Lightning. Annual preventive Maintenance Transformer T1B and T2B 60MVA 132/34.5kV Rehabilitation of Oshogbo/Offa/Omua-Aran 132kv circuit breaker. Rehabilitation of Red and Yellow phase of Osogbo/Ganmo 330kv circuit breaker. 12 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 3.2.2.1 Battery Bank Maintenance The electrolyte inside the batteries of the battery banks at Ganmo Works Centre was observed to be low and required toping up. The battery house consists of two different Battery Banks, one of which is 2 x 110VDC and one of 50VDC all of which are wet cells. The 110VDC banks is used for powering the protective relays which indirectly control the transmission line circuit breakers at the switch yards for 330kV circuit network, 132kV circuit and 33kV circuit, while the remaining 50VDC is for communication equipment powering. Each of the batteries output voltage is 2.03V. 110VDC Banks consist of 55 batteries each connected in series that add up to 110V while the 50VDC Bank consist of 25 batteries connected in series added up to 50V. The process of the maintenance involves checking the level and specific gravity of the electrolyte and measuring the output voltage of each battery after they have been fully charged with an Avo-meter and see whether the expected voltage value is displayed, else the battery needs to be repaired if it cannot be replaced. Figure 3 topping the low level electrolyte with distilled water EXPERIENCE GAINED Experience gained is that when the electrolyte of the batteries got lower and lower, the overall performance of the batteries is also reduced (i.e. low voltages). The electrolyte is subjected to the voltage induced by the electrolysis. This is rectified by topping the low level electrolyte cells with distilled water up to required level respectively. 13 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 3.2.2.2 Switchyard Lightning Switchyard illumination lights ware out of services at 33kV switch yard of Ganmo Works Centre. During the course of troubleshooting, it was discovered that some bulbs were faulty while in some other places it was either the choke is bad, or the igniter or the capacitor and even all the three were spoilt in some cases Figure 4: Troubleshooting and changing of switch yard lightning bulbs at 33KV switch yard EXPERIENCE GAINED Experience gained during the course of this work is how to successfully carry out troubleshooting problems by identifying and segmenting different session of the system and testing each segmented position for faults as well as functions of choke, igniter, and capacitor and how to bypass choke and different types of bulb which are direct and indirect bulb respectively. 3.2.2.3 Troubleshooting of Ganmo/Osogbo/Offa/Omu-Aran 132kV Line Circuit Breaker Troubleshooting of Ganmo/Omua-Aran/Offa/Osogbo 132kV circuit breaker commenced on the faulty three phase breaker mechanisms that could not close fully due to miss-alignment of the pull rod, the miss-aligned pull rod was re-aligned and breaker pole tested okay but during the cause of testing, another fault was discovered on the Red phase. The work was later suspended. Therefore the breaker could not be closed both remote and locally due to 14 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 mechanism fault. However, the line is in service via the 132kV line centre breaker since MAY 2014 Figure 5: Correcting the miss-aligned pull rod of Ganmo/Omu-Aran/Offa/Osogbo 132kV line breaker mechanisms EXPERIENCE GAINED Experience gained during the course of this work is how to successfully carry out breaker mechanisms alignment to prevent over/under drive, how to spring charge a circuit breaker both local electrical and mechanically, as well as physical of identification of breaker component vis-à-vis alignment pull rod, tripping coil, closing coil, motor, auxiliary contact, alignment mechanisms, relays, and how to manually spring a circuit breaker respectively. 3.2.2.4 Rehabilitation of Red and Yellow phase of Oshogbo/Ganmo 330kV circuit breaker Osogbo-Ganmo 330 Red and Yellow phase line breaker mechanism. The faulty Red and Yellow phase mechanism box was removed and replaced with the good one brought from Kanji T/S. The breaker pull rod was connected and tested okay on local/ mechanical operation; continuity test carried out also confirmed the pole to be okay. Following the replacement, wiring of the new 330kv mechanisms carried out okay by PC&M department. Functional test and further troubleshooting of the remote and SCADA operation 15 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 of the equipment continue tomorrow. Meanwhile, local electrical closing and opening carried out okay. Work was later suspended due to logistics. Figure 6: Removing and replacing the faulty H3G breaker mechanisms with the aid of Hayab Machine EXPERIENCE GAINED Experience gained during the course of this work is how to successfully carry out decommissioning and commissioning of breaker mechanisms, how to established continuity test on a circuit breaker with the aid of grounding leads, grounding sticks and Avo-meter, as well as physical of identification of breaker component vis-à-vis tripping coil, closing coil, motor, auxiliary contact, alignment mechanisms, relays, and how to manually spring a circuit breaker respectively. 3.2.2.5 T2A 150MVA 330/132/0.415KV Grounding Transformer II Panel Following the reported tripping of T2A 150MVA Grounding Transformer, comprehensive troubleshooting was conducted and it was discovered that the auxiliary switch control mechanisms was faulty due to misalignment of the switch mechanisms. The fault was clear; the auxiliary switch control was restored back to normal, tested and confirm okay. The equipment was thereafter released back to service. 16 SIWES REPORT Figure 7: (a) Short circuit fault on T2A GT transformer Taofeeq Olawale, SA’AD: 14/67EC/552 (b) troubleshooting the auxiliary control switch mechanisms EXPERIENCE GAINED Experience gained during the course of this work is how to successfully carry out troubleshooting problems by identifying and segmenting different session of the system and testing each segmented position for faults as well as physical identification of auxiliary switch mechanisms. 3.3 SYSTEM OPERATION DEPARTMENT This was the last department visited and the period spent is 4 weeks (26th February to 23rd March, 2018). The department was headed by Engr. S. K. Ibukun as the Principal Manager. The System Operations Department is responsible for carrying out any sort of operations on equipment in the switchyard and control room. Various types of operations carried out include: 1. Electrical Operation: this involves operating equipment using the Electrical interfaces e.g. switches and knobs on the control panel. 2. Remote Operation: this involves operating equipment from a distant position from the equipment. 17 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 3. Mechanical Operation: e.g. spring charging the motor of a circuit breaker by manual rotation of the motor to charge the springs. 4. SCADA (System Control and Data Acquisition) operation: SCADA is one of the solutions available for data acquisition, monitoring and control system covering large geographical areas. It refers to the combination of data acquisition and telemetry. SCADA systems are mainly used for the implementation of monitoring and control system of an equipment or a plant in several industries like power plants, oil and gas refining, water and waste control, telecommunications. Use in TCN Ganmo for control and monitoring e.g. opening and closing of a circuit breaker using the SCADA system from the computer. Also using this system, data as relates to the condition of an equipment can be acquired easily e.g. voltage and current reading on a transformer as well as the power consumption monitoring. 5. Another major aspect of activities carried out in this department is system control and stability. System control involves the monitoring of the values of energy generated and comparing with energy consumed; to ensure there is a balance. When this balance is not there, two things could be done depending on the cause of imbalance. Load is reduced if energy consumption is greater than generation or load is increased if energy consumption is less than generation; this activity is referred to as system stabilizing. 3.3.1 MATERIALS AND TOOLS USED The major tools and/or equipment used are: 1. Hourly Reading Sheet: this is used for taking hourly readings, which include transformer voltage and current levels, transformer winding temperature, system frequency at that hour, load on every available feeder in the station et cetera 2. Frequency Monitor: this helps to read the frequency of the system at a particular instance. It fluctuates with increase or decrease in system frequency due to variations in generation and consumption energy values at that time. 3. Log Book: this is a book in which activities taking place in the system are recorded, for proper system control and stability, and also for reference purposes. Activities such as when a feeder is out for any reason, application and issuance of station guarantee, when reports are received from sub-stations under the area control, when reports are passed to 18 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 the regional control centre, raising of a trouble report et cetera are recorded in the log book. 4. Operating Forms: these are booklets that are used during the course of operation. Examples are the daily log sheet(O. F. 56), trouble and repair report(O. F.19), application for protection guarantee(O. F.1), order to operate(O.F. 17), station guarantee (O. F.4), hourly reading sheet, daily inspection sheet(0.F. 57), energy meter reading sheet, transformers and feeders daily load flow, work permit(O. F. 2), work and test permit (O. F. 3) et cetera 5. Circuit Breaker Spring Charging Handle: this is used to manually spring charge the circuit breaker in case of failure of the springs to charge automatically. 6. Isolating rod: this is used to carry out isolation manually; some isolators can be operated remotely (mostly for high voltage levels-132KV and 330KV). 7. A Desktop Computer System: this is a normal PC with normal windows operating system used for data collections and cataloguing of data acquired from the SCADA system for recording purposes and some other utilities of the use of PC computer e.g. Load Flow. 3.3.2 WORK DONE AND EXPERIENCE GAINED Figure 8: Performing isolating and grounding of 33kV SF6 gas breaker at 33kV switchyard 19 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 The major work done and experience gathered during the attachment in this department are as follows: Breaker operation: learnt various means of operating circuit breaker vis-a-vis mechanical operation, local electrical operation, remote operation or through automation (i.e. using SCADA network) Inspection and daily checks: this involves a walk around the switchyard by the operator, inspecting and checking the working conditions of the equipment, ensuring the pressure in the SF6 gas circuit breakers are normal, taking readings of the temperature of the windings of the transformers in the station, test-running the standby generator to ascertain its working capability so that it can serve as a backup for the station in a case when the station is out of supply, and checking the electrolyte level in the batteries (for batteries that use electrolyte) so it does not get below the minimum, also inspecting the terminals for corrosion. Taking hourly readings from the SCADA system form all the outgoing terminal feeders. Receiving and passing reports: reports including tripping and transformer and feeder load flow are received from substations within the area control; reports of the station activities are also passed to the Regional Control Centre (RCC). How to apply for, and issue station guarantee for several purposes. Also learnt how to isolate and de-energize a line, also to lift isolation and energize. 3.4 PROTECTION CONTROL AND METERING PC&M DEPARTMENT The period spent in this department was 15 weeks (26th March to 6th July, 2018). The department is headed by Engr. Odemakinde R. A. as the Senior Manager (HOD). The Protection, Control and Metering department is responsible for the monitoring of equipment and system activities and providing safety to life and equipment. They make use of relays and instrument transformers majorly to perform its responsibilities. And they mostly do corrective maintenance of the Circuit Breaker, Instrument Transformers and their respective control panels. 20 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 3.4.1 MATERIALS AND EQUIPMENT USED The major materials and equipment that are employed during maintenance in this department includes: 1. Clamp on Ammeter: Clamp-on ammeter or simply 'clamp meter' is an instrument that is used to measure the current flowing through a conductor. 2. Secondary/Primary Current Injection Test Set (SCITs/PCITs): This equipment is used for simulation of faults by injecting a known value of signal into the circuit under investigation. 3. Avo-meter: This is used to measure voltage, current, or resistance during work. 4. Tools Box: This contains a lot of tools used for work which include: spanners of various size sand types (flat, ring, ball and socket), pliers, screw drivers, hack saw, Allen key, file, punch, chisels of various sizes et cetera. 5. Cable Belt, Ferro, Gland and Lugs: These are material used on cables during installation. Cable Belt is used to hold cables together or to the wall of the panel, they come in different sizes. Cable Ferro is a small ring-like material on which numbers or alphabets are written; used for cable identification. Cable Gland is used to hold the cable firmly, usually at the entrance of the cable from the bottom of the panel from the trench. Cable Lug is used to terminate a cable neatly and safely; also come in various sizes depending on the size of the cable. 6. As-built drawings: These are the drawings that were used during the installation of equipment in the station and serve as reference during work on such equipment 3.4.2 WORK DONE AND EXPERIENCE GAINED The scopes of major works done as well as the experience gained in PC&M department are as follow; 1. Carrier Signaling Test 2. Installation of Crompton Greaves 33kV Current Transformer Ratio 600/300/1/1A at Omu-Aran transmission sub-station on Omu-Aran Township Feeder 3. Maintenance of T2A 150MA 330/132/0.415kV diverter switch in Ganmo W/C 4. Installation of Digital multimeter on 33kV OLAM feeder in Ganmo W/C 5. Installation of EDMI MK6 Energy Meter 2000-6EXX Series on 33kV OLAM feeder 21 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 6. Pre-commissioning test on KAM 20MVA and 40MVA transformers at Jimba Oja 7. Comprehensive test on 33kV Feeder 5 at Ganmo W/C. 8. Protection Trip and Calibration Test of Idofian G.R.A, and Industrial 33kV feeders at Ganmo W/C 3.4.2.1 Carrier Signaling Test This involves sending signal on the 330kV circuit from one end to another, this is to ascertain the true state of a given circuit protection. It is expected that whenever distance related faults occurs, a signal is sent and received by the stations of both ends. The carrier signal is transmitted along the power line via the communication network. The test involves sending a carrier signal from the station along the line to the source and confirming the signal reception at the source; and vice versa. There is a special panel design for the test at control room in Ganmo W/C. The test is performed on every first working day of the week and the process is as follows: 1. The operator in charge of the respective source stations (Jebba and Oshogbo) had been communicated and on standby for the tests. 2. The IN and OUT was switch to OUT, signal was sent along the line by pressing green push button LAMP TEST for continuity test as shown in the figure below. It was confirmed okay from each of the respective sources. The switch was then switch to IN, a signal was received from the respective sources by the indicating red LAMP. 3. Second current was sent along the line as the signal. Both sent and received signal was also confirmed okay by following the same procedure in 1-2 except the push button used for sending the current was CARRIER PB, 4. The report on the carrier signaling test was recorded on system operation log book. 22 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Figure 9: carrier signaling test EXPERIENCED GAINED Experience gained during the course of this work is how to successfully carry out carrier signaling test on 330kV circuit in order to ascertain the true state of the circuit protection since it is expected that whenever distance related faults occurs a signal is sent and received by the station involves. 3.4.2.2 Installation of Current Transformer (CT) at Omu-Aran T/S: Following the reported Omu-Aran CT that was defective, PC&M crew decommissioned the bad CT and installed a new Crompton Greaves 1200/800/600/400/1A CT for Omu-Aran 33kV Red phase Line Feeder. Visual checks, Insulation resistance test, Ratio test as well as Polarity test and verification of markings were carried out on the current transformer with satisfactory results. Upon completion of the CT installation, the calibration of the Over-current and Earthfault relays on Omu-Aran 33kv feeder was also carried out okay. Omu-Aran 33kv feeder breaker was tested on remote, local and protection trip okay. Prior to the installation of the new CT, the existing defective R-phase CT was decommissioned and the decommissioning diagram prepared. New Current Transformers CTs (Crompton Greaves) was commissioned for installation at Omu-Aran T/S for Omu-Aran 33kV Red phase Line Feeder. The CTs are for instrumentation and metering service as well as for protections. Each phase of the line (i.e. Red, Yellow and Blue phases) are to be installed with separate CT i.e. single CT for a single phase. The installation process involved is as follow; [12] 23 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 1. Visual check: inspect for physical damages such as cracks on porcelain, oil leakages, oil level, etc to ascertain the physical condition of the equipment. 2. Insulation Resistance test: To check the status of the insulation of HV winding and LV winding with respect to Earth and between the windings or determine the leakage current resistance of the insulation this is inversely proportional to the impurities/moisture content. We injected 5000V into the windings (i.e. Primary to ground, and secondary to ground) using High Voltage Insulation Tester (KYORITSU) for about 30seconds to one minute and measure and record the corresponding resistance respectively Figure 10: Insulation Resistance Test using KYORITSU High Voltage Insulation Tester 3. Ratio test: The test is used to check the ratio of the primary to secondary current under no –load and compare it with name plate rating the transformer ratio test was performed on the CTs respectively by injecting a known current in ampere (A) through the primary terminal of the CT using the Injection Machine. The second terminal was shorted (i.e. 1S11S3, 2S1-2S3, 3S1-3S3, and 4S1-4S3 respectively) and Clamp-on Leakage Current Tester was used to measure the leaking current in milliamp (mA). The formula used in calculating the number of turns is equal to the ratio of injected current at primary terminal to the leakage current measured at secondary terminal i.e. Calculated secondary current = Applied Primary Current CT ratio on name plate 24 SIWES REPORT % 𝐸𝑟𝑟𝑜𝑟 = Taofeeq Olawale, SA’AD: 14/67EC/552 | 𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑆𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 − 𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑆𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 | × 100 𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑠𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 Precaution: When large currents of 500 A and above are applied, the leads from the booster C.T to the test C.T should be capable of withstanding this current and the test must be conducted quickly to prevent overheating of the leads [12]. 4. Polarity test and verification of markings: The test is used to determine the current polarity of the CT and is conducted with a battery cell and a low range D.C. ammeter. Connect a low range D.C. Ammeter to the secondary windings with S1 to +ve and S2 to – ve. Connect the +ve of a battery cell to P1 and just touch the negative to P2. Observe the kick of the ammeter needle. If it is in the forward +ve direction then terminal P1 corresponds to S1. Figure 11: Schematic diagram showing polarity test using batter and Analog multimeter 5. CT Magnetization/Excitation/Saturation Test: To determine the knee point voltage at which the CT core saturates. The Secondary Current Injection Test set (SCITs) is connected to a suitable source of power and grounded, Connect the test equipment secondary to the CT secondary core in series with a digital multimeter. Start the test by gradually increasing the voltage in steps of 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 25 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 220, 240V etc. until the CT is in saturation. Read and record the corresponding current values (mA) on the digital multimeter. Figure 12: Saturation/Excitation test using SCITs and Clamp Ammeter 6. Car crane was used to carry the CTs and to its respective mounting place and bolts and nuts was used to tighten it. 7. The lines conductors were connected to the primary terminals of the CTs respectively, 8. The secondary connector cables were also connected to each of the CTs secondary terminal respectively. Figure 13: Tighning of CT bolt and nuts, and connecting lines conductors 9. Test-run was performed on the circuit using secondary injector. 26 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 10. The CTs was put into service and observed for a while. EXPERIENCED GAINED Experience gained during the course of this installation is how to successfully carry out different type of pre-commissioning test on 33kV current transformer (Crompton Greaves), carefully preparing as met drawing before decommissioning the faulty breaker, and the process involves in conducting a comprehensive calibration test vis-avis over current fault, earth fault and protection trip test and functional test of the all the protective equipment before the breaker was released for service. 3.4.2.3 Schedule Maintenance of T2A 150MVA 330/132/0.415kV diverter switch Comprehensive preventive maintenance was carried out on T2A 150MVA 330/132/0.415kV diverter switches on all its three number On-Load Tap-Changers. The diverters switches brought out and properly cleaned after all the carbonized oil were removed. The compartments were flushed with new transformer oil and the diverter switches were returned vis-à-vis comprehensive maintenance of the protection scheme, functional test of the mechanical protection, Buchholz relay, pressure relief, On-Load Tap Changer (OLTC) oil surge alarm, and trip signals confirmed okay. Breaker test tripped both remotely and local electrical and the transformer were restored for service. (see Appendix III for more pictures) This involved the following (a) Un-mounting the diverter structure of the three phases, one at a time (b) Thorough cleaning of the diverter and washing with new transformer oil (c) Draining of the carbonized oil from the three diverter chamber (d) Thorough Cleaning of the chamber and replacement of new oil (e) Installing the diverter device back into the oil-filled chamber. 27 SIWES REPORT Figure 14: (a) Diverter switch with carbonized oil Taofeeq Olawale, SA’AD: 14/67EC/552 (b) cleaning of Diverter chamber (c) cleaned Diverter chamber EXPERIENCED GAINED Experience gained during the course of this work is the process of isolating a transformer, physical identification of diverter switch vis-a-vis diverter chamber, pressure relief chamber, Buchholz relay, and process of removing the diverter switches, cleaning as well as flushing of diverter chamber with new transformer oil 3.4.2.4 Installation of Digital multimeter on 33kV OLAM feeder in Ganmo W/C Installation of new digital multimeter on OLAM 33kV feeder to replace the existing inaccurate ones, this is with a view to improve system accuracy in Ganmo T/S. The connection is as follows: terminals no 13 and 14 was connected to AC source supply (H1 and H2); terminal no 2, 4, and 6 was looped together and connected to the neutral leg of the Voltage transformer (D70); terminal no 1, 3, and 5 was connected to Red, Yellow and Blues phase (D10, D30, and D50) of the secondary of the voltage transformer respectively. The multimeter was tested and all the readings on the meter were confirmed okay, therefore the multimeter was released for service. 28 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Figure 15: Wiring diagram of OLAM digital multimeter and front view of the ammeter EXPERIENCED GAINED The experience gained was the significance of labeling (i.e. Core or Ferro label) on the wire vis-à-vis identification of Ferro code such C for Control, D for metering, E for voltmeter, K for control and H for AC source respectively as well as the needs for the preparation as met drawing before decommissioning of the previous multimeter and the needs to carefully follow the drawing diagram during the course of installation. 3.4.2.5 Installation of EDMI MK6 Energy Meter 2000-6EXX Series on 33kV OLAM feeder Decommissioning of the malfunctioning Itron OLAM energy meter, wiring and installation of a new energy meter. The connection deployed during the installation is 3phase 4wire drawing and A, B, C, & N on the drawing diagram denotes Red, Yellow, Blue & Neutral respectively. The terminals 2, 5, 9 & 13 (i.e. Va, Vb, Vc, & Vn) are connected to the Red, Yellow, Blue, & Neutral point of the secondary of the voltage transformers respectively, while terminals 1&3, 4&6, and 8&10, are all connected in series to Red, Yellow and Blue phase of the secondary of the current transformer. Readings were checked okay on the three phase energy meter vis-à-vis frequency, power factor, and energy consumption in MW. 29 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Figure 16: (a) wiring diagram description (b) 3phase, 4wire connected energy meter EXPERIENCED GAINED The experience gained during the course of this installation is the importance of inspection in relation to preparation of as met drawing before decommissioning of the previous energy meter, as well as importance of labeling (i.e. core or Ferro label) on the wire and the process of installation of the energy meter in accordance with the drawing. 3.4.2.6 Pre-commissioning test of transformers (20MVA & 40MVA) at KAM 132kV Substation at Jimba Oja After the installation of power transformer, several pre-commissioning tests were to be done before putting the transformer in service. The pre-commissioning test needs to be carefully programmed so that they take place in a logical and efficient order, in order that no equipment is disturbed again during subsequent tests. Before starting the test, it is essential to ensure that the assembly of the particular item being tested has been completed and checked vis-à-vis analysis of the wiring diagrams to confirm the polarity of connections, positive and negative sequence rotation, a general inspection of the equipment, physically verifying all the connections, at both the relay and panel terminations. 30 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 In addition, the lists of the tests carried out on the two transformers (i.e. 20MVA and 40MVA) at KAM 132kV substation arranged in a chronological order together with any precautions that need to be taken into account are briefly described below. 1. Tan Delta Test: Tan delta is the insulation power factor and is equal to the ratio of power dissipated in the insulation in watts to the product of effective voltage & current in volt ampere when tested under sinusoidal voltage. The condition of the bushings and the overall insulation of power transformers can be investigated by measuring the capacitance and dissipation factor, also known as the tangent delta, or power factor. Aging and decomposition of the insulation, or the ingress of water, increases the losses and thus more energy is turned into heat in the insulation. The procedure for tan delta is as follows: Figure 17: Tan Delta test setup with OMICRON CPC100 + CP TD1 The equipment was isolated, working grounds was also applied to all incoming and outgoing cables (so as to remove any residual charges on the cables) and disconnect all incoming and outgoing cables from the transformer bushing terminals. Disconnected cables should have sufficient clearance from the switchgear terminals greater that the phase spacing distance. Nylon rope or aluminum conductor was used to hold cable away from incoming and outgoing terminals as required. The neutral bushing of the transformer grounding bar was isolated. 31 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 All high voltage bushing (i.e. Red, Yellow and Blue phase) terminals was short circuit together with the aid of copper wire. Also all low voltage bushing (i.e. Red, Yellow and Blue phase) terminals and the neutral bushing terminal was short circuit together with the aid of copper wire. Connect the capacitance and dissipation factor test set i.e. The OMICRON Transformer Diagnostic System CPC 100 + CP TD1 refer to figure below i.e. the big and small cable of the equipment was connected to the shorted high voltage bushing and low voltage bushing respectively for grounded and select GSTg-A model on the equipment Record the current, frequency, capacitance and dissipation factor values for different values of voltage. The above steps were repeated for ungrounded except that the big and small cable of the equipment was connected to the shorted low voltage bushing and high voltage bushing this time around, UST-g model was used instead and all the station earth on the transformer was also removed. Record the current, frequency, capacitance and dissipation factor values for different values of voltage for ungrounded as well 2. Insulation Resistance Test (IR): Insulation resistance test of transformer is essential type test; it is carried out to ensure the healthiness of overall insulation system of an electrical power transformer. The following are the procedure used to carry out insulation resistance test of transformers (40MVA & 20MVA) at KAM 132 substation. First, we disconnect all the line and neutral terminals of the transformer. Megger leads was connected to LV and HV bushing studs to measure and record the insulation resistance IR value in between the LV and HV windings. Megger leads was then connected to HV bushing studs and transformer tank earth point to measure and record the insulation resistance IR value in between the HV windings and earth. Megger leads was lastly connected to LV bushing studs and transformer tank earth point to measure and record insulation resistance IR value in between the LV windings and earth. 32 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Figure 18: Insulation Resistance test using 10kV Megger MIT1020/2 on 20MVA transformer at KAM 132kV substation NB: It is unnecessary to perform insulation resistance test of transformer per phase wise in three phase transformer. IR values are taken between the windings collectively as because all the windings on HV side are internally connected together to form either star or delta and also all the windings on LV side are internally connected together to form either star or delta. Since the IR value of transformer insulating oil may vary with temperature. IR values to be recorded at intervals of 15 seconds, 1 minute and 10 minutes. 3. Polarization Index Test (PI): The insulation resistance and polarization index tests of transformers has been regarded as a useful tool in evaluating its windings for buildup of dirt or moisture, deterioration of the insulation, fitness for high potential tests and suitability for further operation. The procedure for polarization index test on transformers (40MVA & 20MVA) at KAM 132 substation is as follows: First we disconnect all the line and neutral terminals of the transformer. Short- circuit all high voltage HV bushing terminals together i.e. Red, Yellow, & Blue phase shorted. Megger leads was connected to the shorted HV bushing studs and transformer tank earth point to measure and record resistance value in between the HV windings and earth. 33 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Short- circuit all low voltage LV bushing terminals together i.e. Red, Yellow, & Blue phase shorted. Megger leads was then connected to the shorted LV bushing studs and transformer tank earth point to measure and record resistance value in between the LV windings and earth. Polarization index was then calculated using the formula below. Polarization Index, PI R10 min utes R1 min utes Figure 19: Polarity test between secondary bushing and earth Interpretation of Polarisation Index results S/N 1 PI Condition 0<1.0 Interpretation of results Hazardous 2 1 - 1.5 Bad 3 1.5 - 2.0 Doubtful 4 2.0 - 3.0 Adequate 5 3.0- 4.0 Good 6 > 4.0 Excellent N.B: A low value of PI indicates that the windings may have been contaminated with oil, dirt etc or absorbed moistures. PI was developed to make interpretation of results less sensitive to temperature. PI is the ratio of two IR at two different times. Temperature of the winding does not rise during the test period of 10 minutes. So it is fairly assumed that both R10 and R1 are measured at same winding temperature. Then the temperature correction factor will be same for both cases and will be cancelled during the calculation of Pl. 34 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 4. Voltage Ratio Test: This test is done to check both the transformer voltage ratio; defects in tap changer; to find out if there is any open circuited turns, or short circuited turns in transformer winding and other internal fault. The voltage ratio is equal to the turn’s ratio 𝑉1 𝑁1 in a transformer(𝑉2 = 𝑁2). Voltage Ratio Test is done at various tap position on no-load condition by applying 3 phases (415V) supply on HV side of Power transformer. At Various taps, applied voltage and resultant voltages LV side between various phases and phases to neutral measured with precision voltmeter. Below is the process for voltage ratio test: First, the tap changer of transformer is kept in the lowest position i.e. on tap level 1 and LV terminals are kept open. Three phases 415V was applied on HV (high voltage side) i.e. on Red, Yellow and Blue bushing of primary in this case. Then we measured and recorded the voltages applied on each phase (Phase-Phase i.e. R-Y, R-B and Y-B respectively) on HV and induced voltages at LV terminals (i.e. r-y, r-b, and y-b) simultaneously with the aid of digital multimeter. The tap changer of transformers was raised by one position and the voltages at HV and LV terminals was measured and recorded respectively. The above steps were repeated for each of the tap position separately up to the last tap (which is tap level 21 in this case) and the corresponding voltages at HV and LV terminals was also measured and recorded respectively. Figure 20: Voltage ratio test on transformer with Digital multimeter N.B: At other taps values will be as per the percentage raise or lower at the respective tap positions. 35 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 5. Magnetic Current Test: Magnetizing current test of transformer is used to detect any defects in the magnetic core structure, shifting of windings, failure in turn to turn insulation or problem in tap changers. These conditions change the effective reluctance of the magnetic circuit, thus affecting the electric current required to establish flux in the core. The process is as follows: First, the tap changer of transformer is kept in the lowest position i.e. on tap level 1 and LV terminals are kept open. The secondary bushing of the transformer (low voltage side) was short circuited with the aid of MCB. Three phases 415V was applied on HV (high voltage side) i.e. on Red, Yellow and Blue bushing of primary in this case. Then we measured and recorded the currents applied on each phase (i.e. IA, IB and IC respectively) on HV and induced currents at LV terminals (i.e. Ia, Ib and Ic) simultaneously with the aid of digital multimeter. The tap changer of transformers was raised by one position and the currents at HV and LV terminals was measured and recorded respectively. The above steps were repeated for each of the tap position separately up to the last tap (which is tap level 21 in this case) and the corresponding currents at HV and LV terminals was also measured and recorded respectively. Figure 21: Magnetization test with the aid of MCB and multimeter 6. Vector Group Test: The vector group of transformer is an essential property for successful parallel operation of transformers. Hence every electrical power transformer must undergo through vector group test of transformer at factory site for ensuring the 36 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 customer specified vector group of transformer. The phase sequence or order, in which the phases reach their maximum positive voltages, must be identical for two paralleled transformers. Otherwise, during the cycle, each pair of phases will be short circuited. Procedures follows during vector group test is as follows: Connect neutral point of star connected winding with earth. Join 1U of HV and 2U of LV together. Apply 415 V, three phase supply to HV terminals i.e. 1U, 1V, 1W respectively. Measure voltages between terminals 2U-1N, 2V-1N, 2W-1N, that means voltages between each LV terminal and HV neutral. Also measure voltages between terminals 2V-1V, 2W-1W and 2V-1W. For vector group test, the following condition must be met: 1. 1U-2W + 1N-2W ≈ 1U-1N 2. 2U-1N > 2V-1N > 2W-1N 3. 2V-1W > 2V-1V or 2W-1W. N.B: The vector group on the name plate of the two transformers is YNd 11 and U, V, W represent Red, Yellow and Blue phase bushing respectively. 7. Checking the operation of the protection tripping and alarm circuits: This is done to ensure that all the function of the equipment are working accordingly incase if there is any fault so as to isolate the equipment, functional tests was done such as checking the tripping signal, alarms signals, windings temperature, and oil temperature respectively EXPERIENCED GAINED The experience gained during the course of this installation is the importance of precommissioning tests and the needs to be carefully programmed so that they take place in a logical and efficient order, in order that no equipment is disturbed again during subsequent tests and how to carefully carry out the pre-commission test one after the other. 3.4.2.7 Comprehensive test on 33kV Feeder 5 CTs at Ganmo W/C Comprehensive test was carried out on all the CTs on 33kV feeder 5 at 33kV switchyard in Ganmo work centre. The tests include ratio test, magnetization test and insulation resistance test respectively. 37 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Ratio test was conducted by injecting current into the CTs primary with the aid of Secondary Injection Current Test Sets (SCITS 100) and the corresponding current at the secondary of the CTs was measured with the aid of clamp on ammeter as explained in section 3.4.2.2 page 24. Magnetization test was also conducted by injecting certain ranges of voltages into the CTs secondary using SCITS 100 and clip on ammeter which was connected in series with the test set equipment was used to measure the corresponding current at each stage as explained in section 3.4.2.2 page 24-25. Insulation was carried out as well by injecting 5000V with the aid of KYORITSU High Voltage Insulation Resistance tester for about 30seconds to one minute and the corresponding resistance was measured and recorded as described in section 3.4.2.2 page 25 Figure 22: (a) Ratio test on 33kV Feeder 5 (b) Insulation Resistance test on 33kV Feeder 5 3.4.2.8 Protection trip and Calibration test on 33kV Feeders at Ganmo Work Centre Protection trip and calibration test: this was done by disconnecting the three phases and neutral that comes from the secondary of the CTs into the protective relay. Secondary Current Injection Test Set kit was used to inject fault current (which will be more than the CT’s secondary current i.e. 1A) to the relay to see the response of protective relay which includes the speed of operation, the sensitivity, and the reliability of the relay when there exist a fault current be it over current or earth fault and see if the time scheduled for the alarm (tripping) to come up is still intact. The process is as follows: 38 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 The test set equipment i.e. Secondary Current Injection Test Set was connected to 220V AC supply. Lead was connected to the station ground and equipment was grounded as well. Current transformer secondary cable was removed from the terminals of the protective relay on the terminal block. One lead was connected to common; the other to 0-24V, 0-100A terminal on the equipment and the other end of the leads was connected to terminals of the protective relay i.e. phase to phase for over current and phase to neutral for earth fault. Plug Setting (P.S), Pick Up (P.U) time and Time Multiplier Setting (TMS) was checked from the relay settings and recorded respectively both for over current and earth fault. Two leads were connected to the breaker protection terminal on the equipment; the other end was connected to the trip coil of the breaker on the terminals block respectively and the circuit breaker was kept in open position. This equipment is used for simulation of faults by injecting a current double the plug setting value both for over current and earth fault and record the neTMS value for both. Protection trip test was carried out by closing the circuit breaker; ensure that the circuit breaker control knob is on remote and injecting current above the plug setting on the protective relay to check if the circuit breaker trips on over current and earth fault respectively. The CT’s secondary terminal was connected back to the relay, and the feeder was restored back to service. Figure 23: Protection trip and calibration of protective relay on 33kV feeders at Ganmo W/C 39 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 CHAPTER FOUR: THE EQUIPMENT 4.1 Introduction This chapter entails the equipment used, the functions of the equipment used and the descriptions of their usage during the course of this attachment at Transmission Company of Nigeria, Ganmo. The equipments used are as follow; 1. Auto-Transformer 2. OMICRON CPC100 + CP TD1 3. Instrument Transformers 4. Circuit Breaker 5. Relays 6. Wave Trap 7. Secondary/Primary Current Injection Test kit 8. Insulation Resistance Tester (Megohmmeter otherwise known as Megger) 9. Leakage Current Tester (Clamp on) 10. Grounding/Earthing Transformer 11. Earthing Reactor 12. SCADA System 4.2 AUTO-TRANSFORMER AND ITS FUNCTIONS 4.2.1 Introduction A transformer is a static machine used for transforming power from one circuit to another without changing frequency. Auto-transformer is a single-winding transformer with taps. With primary voltage applied to the primary terminals, the required secondary voltage from zero volts to the rated primary volts can be availed from the secondary by varying the taps. 40 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Figure 24: 150MVA 330/132/0.415kV Auto transformer 4.2.2 Function of Auto-Transformer 1. Auto-transformer is a power transformer that has incorporated into it a higher level of control techniques and is mostly used in transmission station. An autotransformer is used mainly for the adjustment of line voltages to either change its value or keep it constant. 2. It functions as step down transformer and it keeps the output voltage i.e. secondary voltage constant by the use of tap-changer feature of the auto-transformer. 3. It is a power transformer used in electrical power stations 4.2.3 Usages of Auto-Transformer in TCN Ganmo Works Centre The following are various ways by which Auto-transformers are being used in TCN Ganmo Works Centre: 1. The usage of autotransformer in Transmission Company of Nigeria is to step down the HVAC to a certain values and maintain a constant output voltage i.e. secondary voltage by tap-changing the winding inside the transformer using the Tap-Changer built with the transformer for the ability to change the position of the secondary winding to maintain a constant output secondary voltages. There are two power autotransformers of the different capacity (Power) used in TCN Ganmo namely (i) 150MVA Transformer for stepping down the 330kV incoming line voltage to 132kV which in turn are transmitted to the two substations under TCN Ganmo 41 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 namely to Ilorin TS and Omu-Aran TS. (ii) 60MVA Transformer for stepping down 132kV to 33kV which can now be transmitted to District Stations (Distribution Stations) for domestic and industrial use. 2. Auto-transformers are frequently used in power applications to interconnect systems operating at different voltage classes, for example 330kV to 132kV for transmission. 3. On long rural power distribution lines, special autotransformers with automatic tapchanging equipment are inserted as voltage regulators, so that customers at the far end of the line receive the same average voltage as those closer to the source. The variable ratio of the autotransformer compensates for the voltage drop along the line. 4.3 OMICRON CPC 100 + CP TD1 4.3.1 Introduction and its application(s) The CPC 100 + CP TD1 are used to perform power/dissipation factor and capacitance measurements from 15Hz to 400Hz. This frequency sweep increases the sensitivity of the test and helps you to better assess the insulation condition and detect defects at an early stage [15]. CP TD1 is an optionally available high precision test system for on-site insulation tests of high voltage systems like power and measuring transformers, circuit breakers, capacitors and isolators. With the add-on device CP TD1, CPC 100 increases its range of possible applications into high voltage measurements. CP TD1 comes with its own test card named TanDelta (Tangent Delta), which provides highly accurate measurements of the capacitance Cx and the dissipation factor tanδ (DF) or power factor cosϕ (PF), respectively. Both the dissipation factor and the power factor grant information about possible losses in the insulation material, which are increasing with age and water content. A change of Cx is a warning indicator for partial breakdowns between the layers of a bushing or a capacitor. It can also detect: 1. Insulation failures 2. Aging of insulation 3. Contamination of insulation liquids with particles 42 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 4. Water in solid and liquid insulation 5. Partial discharges [16]. 4.4 INSTRUMENT TRANSFORMERS 4.4.1 Introduction Instrument transformers are primary used to provide isolation between the main primary circuit and the secondary control and measuring devices. This isolation is achieved by magnetically coupling the two circuits. In addition to isolation, levels in magnitude are reduced to safer levels. 4.4.2 Types of Instrument Transformers Used in TCN Ganmo Works Centre Instrument transformers are divided in to two categories: 1. Voltage Transformers (VT): VT has a successor called Capacitor Voltage Transformers (CVT). The primary winding of VT is connected in parallel with monitoring circuit, 2. Current Transformers (CT): the primary winding of the CT is connected in series with monitoring circuit. 4.4.3 Functions of Instrument Transformers 1. To transform currents or voltages from a usually high value to a value (usually 5A/1A or 110V AC) suitable for relays and instruments to handle. 2. To insulate the metering circuit from the primary high voltage system. 3. To provide possibilities of standardizing the instruments and relays to a few rated currents and voltages. 4.4.4 Usages of Voltage Transformer (VT) and Capacitor Voltage Transformers (CVT) 1. The secondary windings proportionally transform the primary levels to typical values of 110V phase to phase 43 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 2. The secondary voltage can be used in switchgear compartments, where it may be used to drive motors that open and close circuit breakers. 3. The secondary voltage can be used in voltage regulators, where it can power a tapchanging drive motor of the Power Autotransformer above. 4. It used for protections of both the equipment in the station and personnel. 5. The secondary voltage is used for metering and operating protection relays such as Over Voltage protection, Under Voltage protection, Over frequency protection, Under frequency protection, Distance Protection, Transformer Differential protection et cetera. 6. The CVT is also useful in communication systems. CTVs in combination with wave traps are used for filtering high-frequency communication signals from power frequency. This forms a carrier communication network throughout the transmission network. 4.4.5 USAGES OF CURRENT TRANSFORMER (CT) 1. To transforms the current on the line to that which is suitable for the meters and relays to function. 2. Metering of power to track energy use. 3. Monitoring of current flow through a circuit. This can be used to monitor the amount of current drawing by are line and the maximum allow current can be set on relay to trip on over current protection. 4. Relay of power through an energy grid. 5. Control of the state of circuit (open or closed) in a ground fault circuit interrupter. 6. Protection of instruments and appliances connected to AC power supplies as well the personnel working at TCN. 4.5 CIRCUIT BREAKERS 4.5.1 Introduction Electrical circuit breaker is a switching device which can be operated manually as well as automatically for controlling and protection of electrical power system respectively. As the 44 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 modern power system deals with huge currents, the special attention should be given during designing of circuit breaker to safe interruption of arc produced during the operation of circuit breaker. There are four type of circuit breaker namely; Air Circuit Breaker (ACB), Oil Circuit Breaker (OCB), SF6 Circuit Breaker and Vacuum Circuit Breaker. They types that is employed at TCN Ganmo and its substations are Oil Circuit Breaker (OCB) and SF6 Circuit Breaker 4.5.2 Functions of Circuit Breaker The main functions of circuit breakers are; Sense the current flowing in the circuit Measure the current flowing in the circuit Compare the measured current level to its pre-set trip point Act within a predetermined time period by opening the circuit as quickly as possible to limit the amount of energy that is allowed to flow after the trip point has been reached. 4.5.3 Usages of Circuit Breaker This equipment is used to make or break a circuit or segment of it, for the purpose of preventing Electrical Energy from getting to certain segments of the transmission and/or station. The circuit breaker can operate under normal (when it is operated deliberately) and abnormal conditions (when its contacts open on discovery of a fault within its jurisdiction). Its contacts are embedded in a medium which function as insulation and arc quenching during operation. Its contacts are not visible to the human eyes; however it could have an indicator telling whether the circuit breaker is open or closed. The medium could be air, oil, gas (Sulphur hexafluoride SF6 gas is widely used), vacuum (absence of oxygen eliminates combustion). The advantages of Gas Circuit Breaker (GCB) over the Oil Circuit Breaker (OCB) are as follows; Oil is combustible and could cause fire outbreak if arcing current is very high. Carbonization of the oil takes place when the contacts are made or broken due to arcing. When the contacts are made or broken, the oil gradually reduces in insulation strength and may result in breakdown, or must be changed regularly. The gases used in the GCB are usually more efficient than using the OCB. 45 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 The GCB provides neater working environment around the breaker than the OCB. In addition, the mode of operation of a circuit breaker could be hydraulic or by spring action (mostly used). 4.6 RELAYS 4.6.1 Introduction A relay is automatic device which senses an abnormal condition of electrical circuit and closes its contacts. These contacts in turns close and complete the circuit breaker trip coil circuit hence make the circuit breaker tripped for disconnecting the faulty portion of the electrical circuit from rest of the healthy circuit. There are two type of protective relays used in TCN which are Electromagnetic type of relay and digital type relay modern ones which is mostly used now a days. 4.6.2 Types, Functions and Usages of Relays 4.6.2.1 Voltage Sensitive Relay Voltage relays identify overvoltage, under voltage, or both. They can only detect an abnormal condition on the line side of where the relay is connected. This allows the device to provide prestart protection. Voltages relays are easy to install, do not require current transformers, and are therefore less expensive. These require only voltage connections so that they may be applied independent of the system load [8]. 1. Under voltage: Under voltage relays trip when the voltage drops below a set point. An under voltage is a sustained system voltage below transformer, motor, generator, or voltage ratings that can lead to equipment failure. They can be caused by a system overload or equipment failures. Special care should be given for under voltages because many power systems loads are MVA loads (motors, uninterrupted power supplies, etc.). This means that as the voltage decreases, the load current increases while the power system transfer capability decreases. Under voltage relays are usually instantaneous devices and should complete their function every time input voltage 46 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 drops below the set point. Load transfer, voltage regulation, and motor protection are all applications for under voltage protection relays [8]. 2. Overvoltage: Overvoltage relays trip when a voltage rises above a set point. An overvoltage is a sustained system voltage in excess of transformer capacitor, motor, generator, or reactor voltage rating. Overvoltage’s can lead to equipment failure or be due to equipment failure, such as failure of a load tap changer controller or by a sudden loss of customer load. Overvoltage relays may be instantaneous or time-delayed devices. Voltage regulation, bus and back- up protection, and generator protection are applications for overvoltage protective relays [8]. 4.6.2.2 Differential Relays Differential voltage relays respond to the difference between incoming and outgoing voltages associated with the protected apparatus. The electrical quantities entering and leaving the system are compared by current transformers. If the net between the circuits is zero, then there is no fault or problem. If the net is not zero then an internal problem can be identified. This type of relay is applicable to all parts of the power system and is often the primary choice for protection [8]. 4.6.2.3 Power (Phase) Sensitive Relay Power or phase-sensitive relays can monitor phase sequence, phase reversal, ground or earth fault, power factor, phase failure or loss, and phase unbalance. 1. Phase Failure (loss) - The relay monitors for voltage with the incorrect phase sequence, or one or more phases open. Failure may occur because of a blown fuse, a mechanical failure of the switching equipment, or if one of the power lines opens. Phase failure involves three phases where there are three wires. If a three-phrase motor is started on a single phase, the motor will not start. If one wire gets disconnected, it is identified as a loss of phase. It is suggested that a device monitoring phase failure be combined with a device that can detect phase angle displacement. This is because voltage sensing devices which monitor only the voltage magnitude may not provide protection when the motor is running. 2. Phase-reversal - Phase-reversal relays monitor for a change of one-half cycle or 180° in phase. A reversal in phase is often due to miss-wiring, faulty incoming power from 47 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 modifications made to the power distribution system, or when power restoration results in a different phase sequence than before the power outage. This protection is required on all equipment transporting people, such as escalators or elevators. 3. Phase-sequence - Phase-sequence relays monitor for correct phase sequence if two wires have their connection reversed and become out of sequence. The device is used to ensure the sequence is correct when connecting three phase loads. If the phase sequence is incorrect, the relay will de-energize preventing the start of incorrectly connected machinery. 4. Phase unbalance - The relay operates when the magnitude of one current excesses the magnitude of another current by a predetermined degree. Voltage balance operates in a similar manner. 5. Power factor - In AC power transmission and distribution, power factor is the cosine of the phase-angle between the voltage and the current. This deals with the different in real and apparent power. A bad power factor can lead to a distorted waveform and higher power use. 6. Ground earth (fault) - Ground fault (earth) relays detect any undesired current path from a point of differing potential to ground [8]. 4.6.2.4 Current Sensitive Relay Protective relays and monitoring relays include current-sensitive relays. Current sensing relays offer an advantage over voltage sensitive relays because they do not respond to back electromotive force (EMF), which accompanies a phase failure on motor loads. They can detect a problem on either the line side or the load side in a branch circuit in which the relay is used. 1. Under-current - Under-current relays trip when the current drops below a set point. Undercurrents can occur if there is a fault with the power supply, or if a loaded motor becomes unloaded. Often an overvoltage situation will cause under-current and can cause damages to the equipment. 2. Over-current – Over-current relays trip when a current rises above a set point. Overcurrent can be caused by either the load or the supply such as a sudden increase in load 48 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 due to faulty electronics or physical load on a motor. Additionally, a drop in voltage could also cause an over-current situation. 3. Differential current conditions - Differential current relays respond to the difference between incoming and outgoing currents associated with the protected apparatus. The principle of differential relays is the same for a station bus and for generators; the device monitors for the sum of all the currents into and out of the bus or generator to be equal to zero. If there is a fault then there will be a net flow of current and the differential relay will be triggered [8]. 4.7 WAVE TRAP 4.7.1 Introduction Wave trap, its name indicates that it is used to trap some waves. They are used at substations to prevent the transmission of high frequency carrier signal of power line communication to unwanted destinations, wave trap also called line trap. They are part of PLCC (Power Line Communication Carrier) used to transmit communication signal over transmission lines. 4.7.2 Functions of Wave Trap The carrier energy on the transmission line must be directed toward the remote line terminal and not toward the station bus and it must be isolated from bus impedance variations. This task is performed by the line trap. A parallel resonant circuit has high impedance at its tuned frequency, and it then causes most of the carrier energy to flow toward the remote line terminal. The coil of the line trap provides a low impedance path for the flow of the power frequency energy. Since the power flow is rather large at times, the coil used in a line trap must be large in terms of physical size. Hence a line trap unit/Wave trap is inserted between bus bar and connection of coupling capacitor to the line. It is a parallel tuned circuit comprising of inductance (L) and capacitance (C). It has low impedance (less than 0.1Ω) for power frequency (50 Hz) and high impedance to carrier frequency. This unit prevents the high frequency carrier signal from entering the neighbouring line. 49 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 4.8 SECONDARY CURRENT INJECTION TEST SET It is a method of connecting a secondary injection test set to a trip unit (trip device, over current module, protection device, OCR, ETU etc.) on a circuit breaker, VT and CT, and injecting a simulated current to prove it works at different levels. 4.8.1 Functions of Secondary Current Injection Test Set 1. Circuit protection is a critical factor in any electrical system. For safety and security it is essential that all protection devices are tested effectively. Testing circuit breakers at their full operating voltages and currents (primary testing) can be impractical and unnecessary. In this situation secondary current injection testing is performed. 2. Primary and secondary current injection tests are normally conducted to check the operation of breaker and their protective relays/devices. 3. The protective devices installed vary from circuit to circuit depending on the protection needs but typical relays/devices include overload, over current, reverse power, earth fault, differential protection, et cetera. 4.8.2 Usage and/or Application Secondary Current Injection Test Set 1. Secondary injection testing is normally conducted when the circuit breaker is closed but is not carrying any current through its main poles. It involves connection of the circuit breaker to a test set that can inject and measure the current required in the device relay to cause it to operate. 2. Secondary injection testing normally involves disconnection of the protective device from its normal VT/CT and connection to a specialist test set that can inject and measure/record the required operating signal directly into the protective device relay to cause it to operate the circuit breaker. 3. The testing involves with CT and VT is to disconnect the lines from their main poles and injects currents and voltages respectively for simulations of the state of the CT and VT respectively. 4. At the same time it tells us CT ratio by measuring CT secondary current and dividing it with known applied rated current or leakage current measured with Clamp on meter. 50 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 4.9 INSULATION RESISTANCE TESTER (MEGGER) 4.9.1 Introduction The Megger is the instrument uses for measuring the resistance of the insulation. It works on the principle of comparison, i.e., the resistance of the insulation is compared with the known value of resistance. If the resistance of the insulation is high, the pointer of the moving coil deflects towards the infinity, and if it is low, then the pointer indicates zero resistance. The accuracy of the Megger is high as compared to other instruments 4.9.2 Functions of Megger Insulation resistance quality of an electrical system degrades with time, environment condition i.e. temperature, humidity, moisture & dust particles. It also get impacted negatively due to the presence of electrical & mechanical stress, so it’s become very necessary to check the IR (Insulation resistance) of equipment at a constant regular interval to avoid any measure fatal or electrical shock. 4.9.3 Usage of Megger A Megohmmeter usually is equipped with three terminals. The "LINE" (or "L") terminal is the so called "hot" terminal and is connected to the conductor whose insulation resistance you are measuring. The tests are performed with the circuit de-energized. The "EARTH" (or "E") terminal is connected to the other side of the insulation, the ground conductor. The "GUARD" (or "G") terminal provides a return circuit that bypasses the meter. For example, if you are measuring a circuit having a current that you do not want to include, you connect that part of the circuit to the "GUARD" terminal. Figure 25: IR test application or usage procedure 51 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 4.10 LEAKAGE CURRENT TESTER (CLAMP ON) 4.10.1 Introduction Clamp-on ammeter or simply 'clamp meter' is an instrument that is used to measure the current flowing through a conductor. 4.10.2 Functions of Clamp On In any electrical installation, some current will flow through the protective ground conductor to ground. This is usually called leakage current. Leakage current most commonly flows in the insulation surrounding conductors and in the filters protecting electronic equipment around the home or office. So what's the problem? On circuits protected by GFCIs (Ground Fault Current Interrupters) e.g. Circuit Breaker, leakage current can cause unnecessary and intermittent tripping. In extreme cases, it can cause a rise in voltage on accessible conductive parts. 4.10.3 Usage of Leakage Current Tester The Clamp-on is use in TCN to detect leakage current in secondary terminal of a CT while performing maintenance and detecting the start of the windings and insulation of the CT. The Clamp-on is clamp on the shorted secondary terminals of the CT while a known current has been injected to the primary side of the CT to test. 4.11 EARTHING TRANSFORMER AND EARTH REACTOR 4.11.1 Introduction The general purpose of earthing system is to protect life and property in the event of 50/60 Hz faults (short-circuit) and transient phenomena (lightning, switching operations). 4.11.2 Functions and Usages of Earthing Transformer This is used as earthing for the auto transformer and likewise as auxiliary supply for station. The earthing transformer serves as the neutral for the secondary of the transformer as step down of the 33KV at the tertiary to 415V, which is used for station auxiliary supply. For cases where there is no neutral point available for Neutral Earthing (e.g. for a delta winding), an earthing transformer may be used to provide a return path for single phase fault currents. 52 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 In such cases the impedance of the earthing transformer may be sufficient to act as effective earthing impedance. Additional impedance can be added in series if required. A special ‘zigzag’ transformer is sometimes used for earthing delta windings to provide a low zero sequence impedance and high positive and negative sequence impedance to fault currents. In a three phase delta connected AC system, an artificial neutral grounding system may be used. Although no phase conductor is directly connected to ground, a specially constructed transformer (a "zigzag" transformer) blocks the power frequency current from flowing to earth, but allows any leakage or transient current to flow to ground. 4.12 SCADA SYSTEM Nowadays, computer control is one of the most cost effective solutions for improving reliability, optimum operation, intelligent control and protection of a power system network. Having advanced data collection capabilities, SCADA system plays a significant role in power system operation. Supervisory Control and Data Acquisition or simply SCADA is one of the solutions available for data acquisition, monitor and control systems covering large geographical areas. It refers to the combination of data acquisition and telemetry. 4.12.1 Functions and Usages of SCADA System SCADA is a means of controlling from remote location by using communication technology. It is used to collect data and control processes at the supervisory level. The SCADA monitored system could be just about an oil refinery plant, a power generation system, a communication network or even a simple switch. To monitor and control the automation system, the SCADA collects data from the system and issue commands accordingly. By using sensors (discrete or analogue) and control relays, the SCADA collects information about processes and control individual equipment. The system is supervised by a SCADA master station which collects data from monitoring devices and issues controls accordingly (either automatically or at the request of human operators). The SCADA system comprises of, Sensors (either digital or analogue): Sensors control relays that directly interface with the managed system. 53 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Remote telemetry units (RTU): These are small computerized units deployed in the field at specific sites and locations. It serves as local collection points for gathering information from sensors and delivering commands to control relays. Communications network: It connects the SCADA master station to the RTU. SCADA master units: These are larger computer consoles that serve as the central processor for the SCADA system. Master units provide a human interface to the system and automatically regulate the managed system in response to sensor inputs. Remote communication server (RCS): The RCS communicates with the RTU and collect information which is also called master station. The master station, an HMI (Human Machine Interface) or an HCI (Human Computer Interface) performs data processing on information gathered from sensors [9]. The functions of SCADA are discussed below; 1. Data acquisition: Data acquisition refers to acquiring, or collecting, data. This data is collected in the form of measured analogue current or voltage values or the open or closed status of contact points. Acquired data can be used locally within the device collecting it, sent to another device in a substation, or sent from the substation to one or several databases for use by operators, engineers, planners, and administration [10]. 2. Supervision: Computer processes and personnel supervise, or monitor, the conditions and status of the power system using this acquired data. Operators and engineers monitor the information remotely on computer displays and graphical wall displays or locally, at the device, on front-panel displays and laptop computers [10]. 3. Control: Control refers to sending command messages to a device to operate the Instrumentation and control system and power-system devices. Traditional supervisory control and data acquisition (SCADA) systems rely on operators to supervise the system and initiate commands from an operator console on the master computer. Field personnel can also control devices using front-panel push buttons or a laptop computer [10]. Some of the functions of SCADA in power distribution system are given below. Improving power system efficiency by maintaining an acceptable range of power factor Limiting peak power demand 54 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Continuous monitoring and controlling of various electrical parameters in both normal and abnormal conditions Trending and alarming to enable operators by addressing the problem spot Historian data and viewing that from remote locations Quick response to customer service interruptions 4.12.2 Applications or Usages of SCADA System 1. Over current Protection: All lines and all electrical equipment must be protected against prolonged over current. If the cause of the over current is nearby then automatically that current is interrupted immediately. But if the cause of the over current is outside the local area then a backup provision automatically disconnects all affected circuits after a suitable time delay. 2. Supervisory Control and Data Acquisition: A supervisory control and data acquisition system (SCADA) transmits and receives logic or data from events of controls, metering, measuring, safety and monitoring of process devices such as Electrical equipment, Instrumentation devices, telecommunication on industrial applications. Power system elements ranging from pole-mounted switches to entire power plants can be controlled remotely over long distance communication links. Remote switching, tele-metering of grids (showing voltage, current, power, direction, consumption in kWh, etc.), even automatic synchronization is used in some power systems. 3. Substation Control using SCADA: In substation automation system, SCADA performs the operations like bus voltage control, bus load balancing, circulating current control, overload control, transformer fault protection, bus fault protection, etc. SCADA system continuously monitors the status of various equipment in substation and accordingly sends control signals to the remote control equipment. Also, it collects the historical data of the substation and generates the alarms in the event of electrical accidents or faults [11]. 55 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 4.12.3 Feeder Control using SCADA This automation includes feeder voltage or VAR control and feeder automatic switching. Feeder voltage control performs voltage regulation and capacitor placement operations while feeder switching deals with remote switching of various feeders, detection of faults, identifying fault location, isolating operation and restoration of service. In this system, SCADA architecture continuously checks the faults and their location by using wireless fault detector units deployed at various feeding stations. In addition, it facilitates the remote circuit switching and historical data collection of feeder parameters and their status. The figure below illustrates feeder automation using SCADA. Figure 26: SCADA System of the entire network of TCN Ganmo Different feeders are automated with modular and integrated devices in order to decrease the number and duration of outages. Underground and overhead fault detection devices provide accurate information about transient and permanent faults so that at the remote side preventive and corrective measures can be performed in order to reduce the fault repeatability. Ring main units and Remote Control Units (RTUs) of underground and overhead network responsible for maintenance and operational duties such as remote load switching, capacitor bank insertion and voltage regulation. The entire network is connected with a communication medium in order to facilitate remote energy management at the central monitoring station [11]. 56 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 CHAPTER FIVE: SUMMARY, CONCLUSION AND RECOMMENDATIONS 5.1 SUMMARY AND CONCLUSION The whole experience gained during the attachment at TCN Ganmo Work Centre was very enlightening. The basic practical skills as well as the real practical skills were exposed to and the opportunity to relate with typical situations relating to the Electrical Energy Transmission. These experiences have successfully broadened my understanding and interest in Electrical and Electronics Engineering as a profession especially in the field of Electrical Power. The training was worthwhile has it accorded me the privilege of gaining insight into job preparation as well as what it meant to carry out proper inspection and also working condition under stress which in a way prepares undergraduates for the outside world after school [3]. The program gave me the privilege to relate with senior professionals and other students from different institutions. … and this experience makes me appreciate the nature, benefits and intricacies of my chosen field of study both in the classroom and in the society at large while also gives me the opportunity to put into practice the theoretical knowledge acquired throughout my stay in school. The program has given me the rare privilege of gaining practical knowledge and widened my knowledge about the application of Electrical and electronics engineering in the world… especially in the field of electrical power [14]. I was fortunate to learn the significance of preventive maintenance and corrective maintenance of electrical power equipments used at TCN G/W; installation of circuit breaker (SF6 type) as well as various pre-commissioning tests for power transformer to mention but few which helped me in relating the knowledge obtained from class to real life scenarios which in turn has built a good degree of confidence especially in my ability to perform under stress. 5.2 PROBLEM FACED DURING THE SIWES Some the problems experienced during the course of the SIWES program. These are as stated below; Limited orientation before starting the program. The workload is too broad to the extent that engineers were unable to explain the importance of work done on particular equipment to me as well as how it relates to the theoretical knowledge garnered. 57 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 There is also difficulty in getting a placement since placement letter was not issued on time. The main problem encountered during the program was problem of transportation. It is difficult to get to the TCN Ganmo every working day. Since remuneration or allowance is not given, so it is very difficult during the time of government owing our parents salaries [3] coupled with road construction going on en route to Ganmo. 5.3 RECOMMENDATIONS Base on the experience and knowledge acquired at the course of the SIWES training, I hereby give the following recommendation base on my observations; Proper orientation should be given to the students by the university before they go on SIWES at least before mid-semester break of first semester. The placement letter should be given to students early enough so as to avoid attachment in irrelevant organization. I recommend that substantial percent of the National budget should go into the development, improvement and sustenance of the power sector. Doing this would help improve Electricity production and in turn improve development and industrialization and subsequently, the income the country generates. Transmission Company of Nigeria should put safety into great consideration; providing adequate safety wears for staff and ensuring their usage; putting in mind that the health of the staff influences its efficiency and delivery, and subsequently profit output. Transmission Company of Nigeria should also ensure that any newly recruited technical staff goes for a technical training course before they should be allowed to work on the field because electrical power maintenance require a careful and wellhandled personnel [3]. Student should avoid prioritizing money over work and experience and should develop a good attitude, good work ethics and be a good ambassador of the university they are representing. 58 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 Institution and ITF should ensure that students are attached at relevant establishment for effective training, experience and exposure related to their course of study in the university. 59 SIWES REPORT Taofeeq Olawale, SA’AD: 14/67EC/552 REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] G. Okwaraoh, "A report of work done at Home Base Development Limited, Real Estate Developers", 2017, [Online]. Available: http://www.unn.edu.ng/publications/files. [Accessed: 11Feb-2018] P. O. Akerejola, “Students Industrial Work Experience Scheme (SIWES),” Information and Guidelines for Students Industrial Work Experience Scheme, no. 04-04-2012, pp. 5-6, 2012. A.A. Olayinka, “Student Industrial Work Experience Scheme (SIWES),” held at Transmission Company of Nigeria, November, 2015. Nsong.org, “The Nigeria Electricity System Operator,” Nsong.org, 2018, [Online]. Available: http://www.nsong.org/Pages/ContentPageLink1.aspx. [Accessed: 14-Mar-2018] Nercng.org, “Transmission”, Nercng.org, 2018, [Online]. Available: http://www.nercng.org/index.php/home/nesi/404-transmission. [Accessed: 14-Mar-2018] Transmission Company of Nigeria, “About Transmission Company of Nigeria”, Tcnorg.com, 2018. [Online]. Available: http://www.tcnorg.com/index.php/find-tickets/258-about-transmissioncompany-of-nigeria. [Accessed: 14-Mar-2018] E. E. A. A. PM, Director, Transmission Company of Nigeria. [Film]. Nigeria, Kwara State: Power Holding Company of Nigeria (PHCN), 2015. Engineering360, “IHS ENGINEERING 360,” IHS, [Online]. Available: http://www.globalspec.com/learnmore/electrical_electronic_components/relays_timers/protecti vemonitoring_relays. [Accessed: 15-Mar-2018]. R. B. Roy, “Controlling of Electrical Power System Network by using SCADA”, International Journal of Scientific & Engineering Research, vol. 3, no. October 10, p. 6, 2012. Wikipedia, “Wikipedia,” 24 02 2015. [Online]. Available: https://www.en.wikipedia.org/wiki/Powersystemautomation. [Accessed 06 12 2015]. E. Technology, “Electrical Technology,” 14 September 2015. [Online]. Available: http://www.electricaltechnology.org/2015/09/scada-systems-for-electrical-distribution.html. [Accessed: 4 November 2015]. P. C. & M. Department, “Basic Power Relaying Protection Course-P1 (manual),” National Power Training Institute of Nigeria-NAPTIN, 2013, pp. 168-180. R. O. Kolawole, “Student Industrial Work Experience Scheme (SIWES),” held at Transmission Company of Nigeria, June, 2017. A. B. Olaoye, “Student Industrial Work Experience Scheme (SIWES),” held at Transmission Company of Nigeria, June, 2017. OMICRON, “CPC 100 + CP TD1-OMICRON,” [Online]. Available: http://www.omicronenergy.com/en/products/cp-td1/. [Access: 12-August-2018] User Equip, “CP TD1 Reference Manual,” [Online]. Available: http://userequip.com/files/specs/6022/CP%20TD1%20Refrence%Manual.pdf. [Access: 12-August2018] 60 APPENDIX I: GLOSSARY Lightning Arrester: used to arrest voltage surges harmful to the transformer and transfer them to the general mass of the earth. Isolators: This is used to segregate a section of the station from Electricity supply. It can operate only under normal conditions and must be operated by someone. There could be various types of isolators depending on the nature of isolation it carries out; e.g. line, bus, bus-tie, transformer secondary et cetera Earthing Switch: this is used for discharging a previously charged line by transferring the residual charges to the general mass of the earth. Bus: this is a conductor or group of conductors that serves as a common connection between circuits. There exist the 330KV, 132KV, and 33KV bus (peculiar to this station). Insulators: this used to prevent electricity supply from reaching a particular area. This is what I mean, insulators a place on towers between the conductor and the gantry to prevent electricity getting to the gantry, thereby protecting persons in the switchyard who may accidentally or deliberately come in contact with the gantry. Some insulators are made of porcelain while others are made of glass. Gantry: this is a structure made by sets of angle irons arranged to form a structure; which forms a support for equipment. Sky Wire: this is a cable usually made of galvanized steel or galvanized steel with optic cables embedded in them; it is placed at the topmost of the towers and acts as lightning arrester for the power lines. Station Permanent Earth: this is an underground earthing system, prepared so as to enhance the earthing capacity of the station. The body of all the equipment in the station is connected to the station permanent earth. Tower/Pylon: this is a set of angle irons arranged in such a manner to form a structure which forms a support for conductors (usually the bus). Conductors: these are metals used for transmission of electrical energy. They come in different sizes and types depending on the voltage level as well as its used. Copper conductors are the most A effective but expensive and bulky. Copper conductors are used mostly where high conductivity is required e.g. for earthing purposes. Aluminium conductors are mostly used because it is cheaper and lighter in weight. Marshalling Kiosk: It is a box containing terminal blocks where all the control and protection of the transformer are wired to. It also houses gauges for reading the winding and oil temperature. Hot Spot: this is a type of problem majorly found on conductors whereby the conductor gives a red glow spot at some points on the conductor especially at its terminals. This problem results when there is so much load on the conductor than it can take; or when there is partial contact which would result in current losses dissipated as heat. The heat builds up over time and if not quickly attended to could cause explosion. Permit: this is a document given to a person representing a group of people who are to carry out work in a section of the station and have requested for a station guarantee. The person who holds the permit is referred to as the permit holder. The permit holder must surrender the permit at the control room at the end of work before restoration of the feeder that had to be out due to the work. Capacitor Voltage Transformer: Capacitor Voltage Transformers (CVT) is used for voltage metering and protection in high voltage network systems. They transform the high voltage into low voltage adequate to be processed in measuring and protection instruments secondary equipment, such as relays and recorders). A Voltage Transformer (VT) isolates the measuring instruments from the high voltage of the monitored circuit. VTs are commonly used for metering and protection in the electrical power industry B APPENDIX II: LIST OF RESULTS 1. CURRENT TRANSFORMER INSTALLATION AT OMUARAN T/S TEST RESULTS Make: Serial No: Year of Manufacture: Current Ratio: Burden VA: Crompton Greaves 20120552 2012 1200/800/600/400/1/1 20 1.1 Insulation Resistance Test Results Termainals 1S1 – Primary 2S1 – Primary 3S1 – Primary 4S1 – Primary Primary – Earth 1S1 – Earth 2S1 – Earth 3S1 – Earth 4S1 – Earth IR Value ∞ ∞ ∞ ∞ ∞ 600 MΩ 1000 MΩ 800 MΩ 500 MΩ Analysis of Result From the test results of table 3.3, all readings are greater than the acceptable limit of 100MΩ, hence the CT passed the insulation resistance test and it is okay for installation. 1.2 Current Ratio Test Results Applied Pry. Current (A) 20 40 60 80 20 40 60 80 20 40 60 80 20 40 60 Calculated Sec. Current (A) Measured Sec. Current (mA) 1S1-1S3, 600/1A 0.033 32.9 0.067 70.2 0.100 104.2 0.133 136.4 1S1-1S2, 400/1A 0.050 50.3 0.100 100.2 0.150 150.9 0.200 201.2 2S1-2S3, 600/1A 0.033 33.6 0.067 69.0 0.100 103.0 0.133 136.0 2S1-2S2, 400/1A 0.050 50.0 0.100 100.4 0.150 150.5 % Errors 0.3 4.78 4.20 2.56 0.60 0.20 0.60 0.60 1.82 2.99 3.00 2.26 0.00 0.40 0.33 C 80 20 40 60 80 20 40 60 80 20 40 60 80 20 40 60 80 0.200 200.3 3S1-3S3, 600/1A 0.033 32.8 0.067 70.0 0.100 103.3 0.133 135.7 3S1-3S2, 400/1A 0.050 49.6 0.100 100.8 0.150 149.7 0.200 200.5 4S1-4S3, 600/1A 0.033 33.6 0.067 67.4 0.100 101.5 0.133 136.4 4S1-4S2, 400/1A 0.050 49.9 0.100 101.0 0.150 151.2 0.200 200.7 0.15 0.61 4.48 3.30 2.03 0.80 0.80 0.20 0.25 1.82 0.60 1.50 2.56 0.20 1.00 0.80 0.35 Analysis of Result For all values on the table above, the % error met the acceptable CT ratio error… limit of the CT thus passed the RATIO test and is okay for installation. 1.3 Polarity test Result 1S1-1S2 2S1-2S2 3S1-3S2 4S1-4S2 Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay Deflected okay D 2. Pre-Commissioning Test on 20MVA transformer at KAM 132kV Substation Make: Serial No: Year of Manufacture: Rated Power (kVA): Rated Voltage (kV): TBEA POWER TRANSFORMER 17016166 2017 20000/20000 (132± 128 ×1.25%)/33 Vector Group: Cooling Mode: YNd11 ONAN 2.1 Voltage Ratio test Result TAP Primary Voltage (V) Secondary Voltage (V) NO R-Y R-B Y-B r-y r-b y-b Ia Ib Ic 1 354 361 359 78 79 82 0.3 0.1 0.3 2 380 381 377 87 88 88 0.3 0.1 0.3 3 381 380 385 88 89 89 0.4 0.1 0.3 4 375 379 383 88 89 90 0.3 0.1 0.3 5 375 378 382 89 90 89 0.3 0.1 0.3 6 374 378 381 90 92 91 0.4 0.1 0.3 7 375 379 382 91 92 92 0.4 0.1 0.4 8 369 368 375 90 95 92 0.4 0.1 0.4 9 352 356 365 89 89 92 0.4 0.1 0.4 10 369 368 383 94 96 96 0.3 0.1 0.4 11 379 379 385 95 98 91 0.3 0.1 0.3 12 378 380 387 97 98 100 0.3 0.1 0.3 13 368 381 376 98 100 97 0.4 0.1 0.4 14 378 380 388 93 84 102 0.4 0.1 0.4 15 376 380 385 101 104 99 0.3 0.1 0.3 16 368 372 380 102 100 104 0.5 0.1 0.5 17 366 385 379 103 102 105 0.6 0.2 0.5 18 377 385 380 106 107 108 0.6 0.2 0.6 19 371 383 371 107 108 109 0.6 0.2 0.6 20 367 384 380 108 106 111 0.6 0.2 0.6 21 367 370 378 109 111 112 0.6 0.2 0.6 E Primary Current (mA) 2.2 Magnetization Test Result TAP Primary Current (mA) Secondary Current (mA) N0 IA IB IC Ia Ib Ic 1 1.4 1.3 1.4 7.2 7.2 7.7 2 1.6 1.5 1.6 8.3 8.3 8.4 3 1.7 1.6 1.7 8.6 8.6 8.6 4 1.7 1.6 1.7 8.5 8.5 8.7 5 1.7 1.7 1.7 8.7 8.7 8.8 6 1.8 1.8 1.8 8.9 8.9 9.0 7 1.9 1.8 1.9 9.0 9.0 9.1 8 1.9 1.9 2.0 9.1 9.1 9.4 9 2.1 2.0 2.0 9.4 9.4 9.7 10 2.1 2.1 2.1 9.4 9.4 9.6 11 2.2 2.1 2.2 9.8 9.9 10.2 12 2.3 2.2 2.3 9.7 10.1 10.3 13 2.4 2.3 2.4 10.2 10.3 10.5 14 2.4 2.4 2.4 10.1 10.5 10.2 15 2.4 2.5 2.6 10.5 10.6 10.4 16 2.7 2.6 2.7 10.5 10.8 10.6 17 2.6 2.7 2.7 10.6 10.9 10.8 18 2.8 2.7 2.7 11.0 10.9 10.8 19 2.7 2.8 2.9 10.9 11.2 11.3 20 2.8 2.9 2.9 11.0 11.1 11.3 21 2.9 2.9 2.9 11.4 11.3 11.2 2.3 Insulation Resistance test Result Equipment: Megger MIT1020/2 Injected Voltage: 5000V Primary Bushing to Ground S/N PHASE Resistance (GΩ) 1 R-g 30.10 2 Y-g 29.50 3 B-g 27.30 Secondary Bushing to Ground 4 r-g 21.46 5 y-g 18.50 F 6 b-g 23.40 Primary to Secondary 7 B-b 38.80 2.4 Polarization Index Test Result Equipment: Megger MIT1020/2 Injected Voltage: 5000V S/N TIME PRIMARY SECONDARY RESISTANCE (GΩ) RESISTANCE (GΩ) 1 10sec. 6.31 9.93 2 30sec. 7.72 16.3 3 1mins. 9.73 17.6 4 2mins. 10.4 22.4 5 5mins. 11.6 31.9 6 7mins. 10.4 31.0 7 10mins. 12.4 28.0 8 20mins. 16.3 32.3 9 30mins. 20.1 42.8 2.5 Tan Delta Test Result S/N Voltage (V) Current (µA) Frequency (Hz) HV-LV Grounded Capacitance (nF) % ? Model: GSTg-A 1 505 414.63 50 2.61014 0.3424 n/a 2 506 415.58 50 2.61005 0.3393 n/a 3 504 414.14 50 2.61010 0.3414 n/a 4 503 413.31 50 2.61006 0.3404 n/a 5 504 413.87 50 2.60978 0.3824 n/a LV-HV Grounded Model: GSTg-A 6 504 1.0405 50 6.56672 0.3486 n/a 7 504 1.0407 50 6.56659 0.3478 n/a 8 504 1.0396 50 6.56658 0.3475 n/a 9 503 1.0390 50 6.56656 0.3461 n/a 10 503 1.0390 50 6.56653 0.3473 n/a HV-LV Ungrounded Model: UST-g 1 505 557.85 50 3.51680 0.2082 n/a 2 503 556.19 50 3.51674 0.2083 n/a 3 505 558.16 50 3.51674 0.2094 n/a G 4 505 557.65 50 3.51666 0.2080 n/a 5 504 556.37 50 3.51671 0.2080 n/a LV-HV Ungrounded Model: UST-g 1 505 557.88 50 3.51687 0.2087 n/a 2 505 557.63 50 3.51689 0.2079 n/a 3 504 556.83 50 3.51681 0.2084 n/a 4 506 558.93 50 3.51677 0.2088 n/a 5 503 555.93 50 3.51685 0.2078 n/a 2.6 Vector Group Test Result S/N Terminal Voltage (V) 1 1U2W 98.5 2 1N2W 130.6 3 1W2W 322.7 4 1W2V 413 5 1U2V 308.1 6 1V2W 308.1 7 1U1N 230.6 CONDITIONS TO BE MET 1. 1U2W + 1N2W = 1U1N 98.5 + 130.6 = 230.6 229.1 ≈ 230.6 Remarks: Good 2. 3. 1W2W < 1W2V 322.7 < 413 Remarks: Good 1U2V = 1V2W 308.1 = 308.1 Remarks: Good H 3. Pre-Commissioning Test on 40MVA transformer at KAM 132kV Substation Make: Serial No: Year of Manufacture: Rated Power (kVA): Rated Voltage (kV): TBEA POWER TRANSFORMER 18016345 2017 40000/40000 (132± 128 ×1.25%)/33 Vector Group: Cooling Mode: YNd11 ONAN 3.1 Voltage Ratio test Result TAP Primary Voltage (V) Secondary Voltage (V) NO R-Y R-B Y-B r-y r-b y-b Ia Ib Ic 1 393 396 392 88 89 89 3.2 1.4 3.4 2 392 395 391 89 90 90 3.2 1.5 3.5 3 393 398 391 90 91 91 3.3 1.5 3.7 4 392 398 392 91 92 92 3.4 1.5 3.8 5 387 394 388 92 93 93 3.5 1.6 3.8 6 392 399 390 93 949 94 3.6 1.6 4.0 7 391 399 390 94 96 96 3.7 1.7 4.0 8 392 399 390 96 97 97 3.9 1.7 4.2 9 391 397 390 97 96 96 3.9 1.8 4.3 10 391 399 390 98 99 99 4.0 1.9 4.4 11 391 398 389 99 100 100 4.1 1.9 4.5 12 390 396 389 100 102 102 4.2 1.9 4.5 13 390 395 388 102 103 103 4.3 2.0 4.7 14 390 396 385 103 104 104 4.4 2.1 4.9 15 389 395 386 104 105 105 4.5 2.2 5.0 16 389 396 387 105 108 108 4.7 2.2 5.2 17 388 397 387 107 109 109 4.8 2.3 5.3 18 388 397 388 108 110 110 5.0 2.4 5.5 19 388 395 388 110 112 112 5.1 2.4 5.6 20 389 396 388 112 114 114 5.2 2.5 5.7 21 388 395 388 113 115 115 5.3 2.6 5.9 I Primary Current (mA) 3.2 Magnetization Test Result TAP Primary Current (mA) Secondary Current (mA) N0 IA IB IC Ia Ib Ic 1 3.7 3.5 3.7 17.3 17.4 17.9 2 3.8 3.6 3.8 17.6 17.7 18.2 3 3.9 3.8 3.9 18.0 18.2 18.6 4 4.0 3.9 4.1 18.3 18.5 18.8 5 4.3 4.1 4.3 18.6 18.9 19.3 6 4.5 4.2 4.4 19.1 19.2 19.8 7 4.6 4.4 4.5 19.5 19.6 20.2 8 4.7 4.5 4.7 19.9 20.0 20.5 9 1.6 4.7 4.9 20.3 20.4 20.9 10 5.1 4.8 5.0 20.7 20.8 21.3 11 5.2 5.0 5.1 21.1 21.2 21.7 12 5.3 5.0 5.3 21.4 21.4 21.9 13 5.4 5.3 5.4 21.7 21.8 22.2 14 5.6 5.5 5.7 22.1 22.1 22.6 15 5.8 5.7 5.8 22.4 22.5 23.0 16 6.0 5.8 6.0 22.7 22.8 23.3 17 6.1 6.0 6.2 23.0 23.2 23.7 18 6.3 6.2 6.3 23.2 23.4 24.0 19 6.5 6.4 6.5 23.6 23.7 24.2 20 6.6 6.4 6.7 23.8 23.9 24.4 21 6.8 6.7 6.9 24.0 24.2 24.4 3.3 Insulation Resistance test Result Equipment: Megger MIT1020/2 Injected Voltage: 5000V Primary Bushing to Ground S/N PHASE Resistance (GΩ) 1 R-g 19.3 2 Y-g 19.5 3 B-g 20.8 Secondary Bushing to Ground 4 r-g 11.5 5 y-g 11.9 6 b-g 11.3 J Primary to Secondary 7 B-b 25.9 3.4 Polarization Index Test Result Equipment: Megger MIT1020/2 Injected Voltage: 5000V S/N TIME PRIMARY SECONDARY RESISTANCE (GΩ) RESISTANCE (GΩ) 1 10sec. 6.31 9.93 2 30sec. 7.72 16.3 3 1mins. 9.73 17.6 4 2mins. 10.4 22.4 5 5mins. 11.6 31.9 6 7mins. 10.4 31.0 7 10mins. 12.4 28.0 8 20mins. 16.3 32.3 9 30mins. 20.1 42.8 3.5 Tan Delta Test Result S/N Voltage (V) Current (µA) Frequency (Hz) HV-LV Grounded Capacitance (nF) % ? Model: GSTg-A 1 504 444.45 50 2.80489 0.2938 n/a 2 504 444.97 50 2.80489 0.2922 n/a 3 504 444.92 50 2.80491 0.2977 n/a 4 503 444.03 50 2.80481 0.2935 n/a 5 504 444.36 50 2.80470 0.2979 n/a LV-HV Grounded Model: GSTg-A 6 505 1.3981 50 8.81291 0.4706 n/a 7 504 1.3971 50 8.81280 0.4661 n/a 8 504 1.3972 50 8.81268 0.4622 n/a 9 505 1.3986 50 8.81251 0.4639 n/a 10 504 1.3972 50 8.81270 0.4722 n/a HV-LV Ungrounded Model: UST-g 11 506 779.10 50 4.89964 0.1968 n/a 12 503 773.64 50 4.89964 0.1953 n/a 13 504 775.94 50 4.89963 0.1957 n/a 14 504 776.26 50 4.89959 0.1956 n/a K 15 506 779.39 50 LV-HV Ungrounded 4.89963 0.1964 n/a Model: UST-g 16 504 776.29 50 4.89970 0.1947 n/a 17 504 775.35 50 4.89970 0.1953 n/a 18 503 774.98 50 4.89967 0.1954 n/a 19 503 774.49 50 4.89966 0.1956 n/a 20 505 777.99 50 4.89962 0.1954 n/a 3.6 Vector Group Test Result S/N Terminal Voltage (V) 1 1U2W 98.0 2 1N2W 128.9 3 1W2W 314.5 4 1W2V 406.0 5 1U2V 309.3 6 1V2W 307.9 7 1U1N 226.7 CONDITIONS TO BE MET 4. 5. 6. 1U2W + 1N2W = 1U1N 98 + 128.9 = 226.7 226.9 ≈ 226.7 Remarks: Good 1W2W < 1W2V 314.5 < 406.0 Remarks: Good 1U2V = 1V2W 309.3 ≈ 307.9 Remarks: Good L APPENDIX III: PICTURE GALLERY 3phase 33kV Current Transformer 3phase 132kV Current Transformer OMICRON CPC100 + CP TD1 Multimeter 3phase 132kV Voltage Transformer Lightning Arrester on 60MVA and 150MVA transformers respectively Wave Trap Hard hat M Secondary Current Injection Test Kit 60MVA 132/34.5kV Power transformer 33/0.415kV Grounding Transformer 3phase 330kV Capacitive VT (CVT) 150MVA 330/132/0.415kV Auto-transformer Earthing Reactor Marshalling Kiosk 150MVA Transformer Diverter Chamber N Battery Hydrometer 150MVA Transformer Diverter Switch Electric Hand Pump Machine Frequency Monitor High Voltage IR Tester Pressure Relief Device 110V DC Battery Bank Battery charger Control panels Gantry O Sky Wire Buchholz Relay Buchholz Relay