Vol: 1 Issue: 1
HARMONIC ANALYSIS AND EVALUATION OF 52 BUS IN NIGERIA TRANSMISSION NETWORK
Moyosoluwalorun Sonola, Gertrude Fischer, Eke Asuquo
1. INTRODUCTION
The Electrical Power sector plays an important role in the socioeconomic development of a nation. However, in the case of Nigeria, the power network is facing multifaceted challenges that demand intervention. The power system is overloaded, supplying beyond nominal capacity. With a growing population, the demand for electrical energy has surged exponentially, outpacing the capacity of the existing infrastructure. Generation stations situated far from load centres transmit their electrical energy via long, radial and not up-to-standard transmission lines [1]. This noticeable demand-supply gap has resulted in a strain on the power system, giving rise to voltage fluctuations, equipment overheating and diminished power quality, ultimately compromising the overall reliability of the grid [2]. However, the urgency for a comprehensive system analysis of the electrical network in Nigeria cannot be overstated as she’s at an all-time peak of industrial production and thus ensuring a stable power supply is crucial to sustain this growth.
Incorporated in the existing 330kV Nigeria grid network are complex equipment such as transmission lines, transformer tappings, various alternators, reactors, compensators, phase shifters, synchronous condensers, static capacitors, etc, and Power quality meters which serve as the medium for data collection. With the availability of the data comes the avenue for system status and operation assessment, analysis by network designers, and network system forecast [3]. This work used the harmonic analysis method of analysing power systems to evaluate the improved 52-bus Nigeria 330kV power network.
The harmonic analysis offers a granular perspective on the power system in the frequency domain as opposed to the time domain, pinpointing sources of distortion and hence enabling the development of mitigation strategies that enhance power quality [4]. Using Electrical transient and analysis program (ETAP), one of the best tools to study harmonics in the power system, this work navigated the complexities of the 52-Bus Nigeria Transmission Network evaluating the network performance, effectiveness and alternative plans for network reconfiguration. The level of harmonic distortion in the system is indicated by the Total Harmonic Distortion (THD) index, which is used to measure current and voltage dimensions.
THD is defined as the root mean square (rms) value of the hth harmonic component divided by the respective rms value of the fundamental component, multiplied by 100% [5]. The THD of current can vary from 5% to 100%, while THDs of voltage less than 5% are generally considered acceptable. Values exceeding 5% may indicate problematic equipment, devices, or arrangements [6].
Harmonic modelling in power networks is a crucial aspect of electrical engineering that involves the analysis and understanding of harmonic distortions within an electrical system. These harmonic distortions emerge from the operation of various equipment and inductive and capacitive loads in the system causing problems such as voltage distortion, overheating and power quality issues. To address these problems, we use harmonic modelling to identify possible sources of harmonics in a particular system. Key steps needed to conduct a harmonics study come from research experience and practical insights. However, these steps encompass the acquisition of a single-line diagram of the network, pinpointing the point of common coupling, identifying harmonic sources, conducting harmonic measurements, and modelling network components using simulation software like ETAP. After, there is a comparison of the results with national standards.
In order to create a reliable harmonic model for any network, it is imperative to accurately represent all the network components. To conduct comprehensive harmonic modelling and simulation of a given system, two critical considerations have been identified and reviewed to bridge the gap and yield more dependable results. ETAP is employed, and on-site measurements of harmonic currents are used to fine-tune computer-based harmonic current models to match and validate the measured data. The Power System Computer Aided Design/Electromagnetic Transients including DC (PSCAD/EMTDC) software is utilized to build simulation models based on laboratory-measured waveforms. A generalised model for distribution systems has been successfully implemented for practical case studies, using verified simulation models for a range of industrial and household electrical equipment and appliances. Similarly, DigSilent/PowerFactory serves as the simulation software used to assess future levels of harmonic distortion in the power grid, based on the present harmonic current source model developed from measured data [7].