Bonginkosi Thango

University of Johannesburg | uj · Department of Electrical and Electronic Engineering Technology

This article presents an ultramodern modelling algorithm for predicting the remnant cellu- lose life cycle for oil-submerged power transformers based on the adaptive neuro-fuzzy interference system (ANFIS). The polymer characteristics, degree of polymerization (DP), and 2-furaldehyde (2FAL) of 100 power transformers were measured and collated, whic...

In South Africa, the growing power demand, challenges of having idle infrastructure, and power delivery issues have become crucial problems. Reliability enhancement necessitates a life-cycle performance analysis of the electrical power transformers. To attain reliable operation and continuous electric power supply, methodical condition monitoring o...

In this work, the application of a feed-forward artificial neural network (FFANN) in predicting the degree of polymerization (DP) and loss of life (LOL) in oil-submerged transformers by using the solid insulation evaluation method is presented. The solid insulation evaluation method is a reliable technique to assess and predict the DP and LOL as it...

Distribution transformers are commonly designed and manufactured to operate at fundamental frequency and to facilitate sinusoidal loads. The operation of loads that draw distorted currents culminate in higher losses, hotspot temperatures, degradation of insulation materials and declined service life. To avert these technical challenges, the continu...

Oil-submerged transformer is one of the inherent instruments in the South African power system. Transformer malfunction or impairment may interpose the operation of the electric power distribution and transmission system, coupled with liability for high overhaul costs. Hence, recognition of inchoate faults in an oil-submerged transformer is indispe...

The increasing demand for electricity in South Africa has led to a rise in the deployment of solar photovoltaic systems. The integration of these systems requires the installation of power transformers to convert the generated DC power into AC power that can be fed into the grid. However, the high cost of these transformers can hinder the widesprea...

In the Southern African Development Community (SADC), transmission lines facilitate power utilities in distributing a considerable amount of electricity from generation stations to end users. Long conductors used in transmission lines can cover great distances. However, they are susceptible to various environmental and weather conditions which can...

Electrical power transformers are the most exorbitant and tactically prominent components of the South African electrical power grid. In contrast, they are burdened by internal winding faults predominantly on account of insulation system failure. It is essential that these faults must be swiftly and precisely uncovered and suitable measures should...

Despite the significant slowdown of economic activity in South Africa by virtue of the COVID-19 outbreak, load shedding or scheduled power outages remained at a high level. The trend of rising load-shedding hours has persisted throughout most of the year 2022. Operational issues within the South African power utility inflamed the unpredictable natu...

The life expectancy of power transformers is primarily determined by the integrity of the insulating oil and cellulose paper between the conductor turns, phases and phase to earth. During the course of their in-service lifetime, the solid insulating system of windings is contingent on longstanding ageing and decomposition. The decomposition of the...

In South Africa, distribution transformers (DTs) facilitating solar photovoltaic applications represent the highest percentage of total ownership cost investment for independent power producers (IPPs). One of the most indispensable variables that regulate DTs’ operational life span is the hotspot temperature. The prevailing analytical approaches de...

In the new era of the renewable energy market in South Africa, there is a knowledge gap in the technical standards relating to distribution transformers, which are exclusively intended to serve in large-scale solar photovoltaic (PV) applications. The problem arises from the reality that these transformers are compelled to facilitate an environment...

The electricity production opus in South Africa has transformed over the last few years from predominantly coal power generation to a blend of renewable energy generation. The necessity emerges to ascertain whether electrical transformer design philosophies in local manufacturers are contemporary in reference to customer specifications, under incre...

A frequency response analysis (FRA) is a well-known technique for evaluating the mechanical stability of a power transformer’s active part components. FRA’s measuring practices have been industrialised and are codified in IEEE and IEC standards. However, because there is no valid coding in the standard, the interpretation of FRA data is still far f...

South Africa is currently facing shortage of electricity, as the national utility is forced to implement routine load shedding stages. To tackle this problem, the country has planned to boost its electricity infrastructure through the systematic development of renewable energy independent power projects to provide additional capacity for the nation...

In the last decade, South Africa has attracted and attained more investment by means of the Renewable Energy Independent Power Producer Procurement Programme (REI4P), which is, a structured invitation to Independent Power Producers (IPPs) to submit a bid to generate and supply power to the electrical grid. In spite of REI4P’s undeniable triumph, a...

The ageing of oil-immersed power transformers triggers several defects and damages in the insulating materials, particularly in the cellulose insulation. The decomposition of the cellulose paper produces dissolved gases into the insulating oil, in which the Dissolved Gas Analysis (DGA) of the oil samples can provide insights to incipient faults sus...

The transformer cellulose insulating material is a key benchmark for evaluating the remnant transformer service lifetime. The decomposition of the cellulose paper may be assessed by using the degree of polymerization (DP) which necessitates that paper samples be extracted from the unit in- service. Whereas, extracting the cellulose paper is particu...

With the evolution of solar photovoltaics, the capacity of solar photovoltaic transformers is increasing. The winding conductor succumb to larger dimensions, to be able to withstand the extreme operational condition of solar photovoltaic application. The magnetic flux leakage responsible to produce Eddy currents in windings and other metallic compo...

Stray gassing of transformer oil is a convoluted physical phenomenon, in which several parameters act simultaneously thus making the understanding of Dissolved Gas Analysis (DGA) more daunting. Historically, prudent maintenance strategies are better conceived by studying the condition of units in service. To alleviate transformer management and dec...

Preventive maintenance endeavors in transformers aim to appraise the risk by means of the computation and surveillance of the health index of transformers in service. A prevalent method employed in the preventive maintenance and assessment of the health index of transformers is the Dissolved Gas Analysis (DGA). A contemporary trend is to utilize an...

Untimely failures of Distributed Photovoltaic Power Generation System (D2PGS) Transformers has been reported by various utility owners in spite of designing in accordance to the technical criteria and practices of the existing technical standards during the design phase and manufactured units passing the Factory Acceptance Tests (FATs) to corrobora...

The integration of classical transformer design procedures with the staggering speed and coherent versatility of modernistic computational methods to evaluate and manage stray losses in transformers incite better understanding into the transformer design philosophy especially for renewable energy (RE) application. This is on account of tools suchli...

The rapidly increasing demand for Distributed Photovoltaic Power (DPVP) generation system transformers and the rise in the construction of solar photovoltaic plants in South Africa, present technical challenges in the latter involving high top-liquid and hotspot temperatures problems during their service lifetime. The winding Eddy current loss harm...

In the recent multifaceted transformation dawn of low-carbon power generation markets and escalated growth of the renewable energy technologies in South Africa, a comprehensive analysis of the technical and economic performance of transformers has been under-explored as a result of insufficient knowledge in this study area. The Transformer Total Ow...

Transformers are habitually designed and manufactured for operation at a fundamental frequency of 50Hz and sinusoidal load current. Transformers are susceptible to non-linear loads. The inception of switching action characterises Non-linear loads and consequently nonsinusoidal load current which brings about higher transformer service losses, hotsp...

Distributed Solar Photovoltaic (DSP) Plants are one of the fastest growing renewable energy systems in South Africa. The primary components forming an integral part of the point of common coupling (PCC) are, the inverter used to convert dc voltage to ac voltage and step-up transformers which step-up low voltage input to the desired output level. Ho...

The rapid transformation of the energy sector in South Africa towards renewable energy (RE) production calls for the management of assets to keep pace with the ongoing developments in a reliable manner. Aging assets, increasing energy needs and reliable supply of energy without load shedding are some of the challenges utilities are facing in South...

South Africa is aiming to achieve a generation capacity of about 11.4GW through wind energy systems, which will contribute nearly 15.1% of the country’s energy mix by 2030. Wind energy is one of the principal renewable energy determinations by the South African government, owing to affluent heavy winds in vast and remote coastal areas. In the desig...

To this extent, the delineation of techno-economic evaluations for transformers becomes more intricate through a lens of Distributed Solar Photovoltaic (DSPV) market in South Africa. Essentially, the transformer price and loss evaluation techniques should be tailored for calculating the Total Ownership Cost (TOC) of transformers facilitating decent...

In this day and age, there is a proliferate concern from all governments across the globe to barricade the environment from the greenhouse gases, which absorb infrared radiation. As a result, solar photovoltaic (PV) energy has been an expeditiously growing renewable energy source and will eventually undertake a prominent role in the global energy g...

The presence of harmonic currents as a result of switching action of inverters, intermittent sunlight, and resonances triggered by the connection of the solar photovoltaic plant to the electrical network has spread the realization of the prospective rapid depletion of a transformer’s intended service lifetime owing to increased service losses and t...

In 2010, South Africa introduced the Renewable Energy Independent Power Producer Procurement Programme to invigorate low-carbon energy generation using renewable energy resources. Amongst the development of wind and hydro plants; Distributed Solar Photovoltaic (DSPV) plants then took off rapidly. The volume of DSPV plants connected to the grid in 2...

In the last decade, solar photovoltaic energy generation has emerged as one of the leading vanguards of renewable energy source generation in South Africa. The considerable growth in the deployment of solar photovoltaic plants has grabbed the attention of worldwide project developers, investors and stakeholders. In the way indicated, more devised e...

Over the last decade, South Africa has witnessed a generous amount in the number of failure rates in distribution solar photovoltaic (DSPV) energy transformers that has been derived from the knowledge deficit of the criterion for designing and an appropriate manner of specifying these transformers. Solar photovoltaic producers have underlined a con...

A surge in harmonics and distortion in the South Africa’s electric power system has come to the fore in the early phases of integrating renewable energy resources to the national electric grid. Having said that, in this day and age a considerable number of harmonic producing apparatus are present. On the basis of their beneficial effects in efficac...

South Africa has established one of the most reputable renewable energy programmes in the world. The latter presents a new energy mix in the country, and as a consequence it is important to acknowledge the operational characteristics of each power utility. Subsequently, it is crucial then to evaluate the service lifetime cost of each kilowatt as fa...

In this paper, a method for estimating the winding Eddy Loss based on an improved harmonic loss factor for transformers under harmonic conditions is presented. The method considers the skin depth of penetration of the field at higher harmonic orders, leading to a greater degree an accurate estimation of the winding Eddy losses under harmonic condit...

South Africa has achieved a substantial amount in the country’s energy generation capacity through distributed photovoltaic systems. A much-discussed hindrance on this development has been related to the rich penetration of harmonics and distortion in the connected transformers, which drives a temperature rise and generation of hotspots in the acti...

�� ���� � ���� ������� ���������� ��� ���������� ���� ���� ������ ����� �������� ������ ��� �� �� ���� ��!� ������������������� � ����������"�� ��������������� � ��"�����"#� � �� "� ��� ��!��� ��� ��� ����� ���� � ���� ���"$� "����� ���!������ ���"�������%������� ��� #�&���!��� �����"����� '� ���"��������������� ����������(��������)���"��� �������...

In the past decade, South Africa has acquired more renewable energy (RE) generation capacity than the rest of the Sub-Saharan countries. This development has led to increasing concerns about problems associated with electrical equipment connected with the RE technologies, especially in wind and solar. These RE technologies have intermittent generat...