Dr. Nilantha C Sapumanage - Academia.edu (original) (raw)
Papers by Dr. Nilantha C Sapumanage
This study disclosed that the IEC impulse is not an appropriate candidate to benchmark real trans... more This study disclosed that the IEC impulse is not an appropriate candidate to benchmark real transient over-voltages owing to have many discrepancies between them in terms of energy localization and frequencies that host such energies. However, the total energy content of the comparable IEC impulse is higher than the real transient voltages. Thus, once tested and passed the endurance at laboratories such an energy absorbing device would not fail at the field applications against single real transient voltage. However the same cannot be guaranteed against the swarm of impulses as the same cannot be tested at the test bench due to many practical constraints. The study revealed that IEC impulses can accommodate only 2.31% of the total energy until it reaches to 90% of the peak voltage, whereas the selected real transient impulses have shown that they could accommodate nearly 6% to 18% of the total incident energy before they reach to 90 % of the peak voltage. Moreover, when IEC impulse reaches to the peak, it can incident only a 9.71% of the total energy, but real transient voltages demonstrated that they have a capacity to incident nearly 30% to 45 % total energy embedded in the impulse.
2021 35th International Conference on Lightning Protection (ICLP) and XVI International Symposium on Lightning Protection (SIPDA)
This study employed wavelet transformation to disclose the spectrograms of IEC standard impulses ... more This study employed wavelet transformation to disclose the spectrograms of IEC standard impulses and real transient voltages generated by the cloud to ground discharges. The spectral details of each impulse were subdivided into different spectral clusters and the outcome was mapped into respective voltage levels and time to develop correlations. Eventually different protection voltage levels of commercially available surge protection devices (SPDs) and the voltage levels of different spectral clusters were compared to determine whether harmful energy infringements could be possible when the spectral clusters are wrapped by SPDs. This study revealed that all IEC impulses have identical spectral clusters whereas real transient voltages demonstrated that they are inherited with much random spectral distributions. Thus, planning for foolproof through benchmarking real transient impulses against IEC impulses would not produce guaranteed outcomes. Hence, a poor selection of clamping voltages may create a permanent window to infringing a small quantum of harmful energy on a constant basis into sensitive systems to trigger silent killing of basic functional units.
2020 International Symposium on Electromagnetic Compatibility - EMC EUROPE
Surge Protection Devices (SPDs) are being extensively used at present to safeguard electronic equ... more Surge Protection Devices (SPDs) are being extensively used at present to safeguard electronic equipment from lightning generated transient over-voltages. Despite SPDs being employed to protect electronic equipment, every year millions worth damages are being reported. Hence, isolation from the power grid would be considered as the best solution to prevent the infiltration of harmful energy contained in the transient over-voltages. But isolation cannot be performed by humans as they are not sensitive to imminent lightning discharges nor fast enough to respond post lightning events. Thus, there should be an extra-fast mechanism to detect imminent lighting discharge and perform a change-over from the utility supply to a local power supply. This study aims to device a machine learning solution which could be used to overcome such limitations in traditional SPDs. For the convenience of analysis, reported impulses were categorized into three signature types. Namely, pulse-burst, unipolar and bipolar. A data sample was taken which represents all above said signature types, was processed and fed into the Azure Machine Learning Studio in order to train a linear regression model. Such model yielded an R2 value of 0.7547. The strong positive correlation between the strength of the electric field and the magnitude of the induced voltage was thereby confirmed. The deployed solution had a mean accuracy of 87.82% of its predictions, confirming its ability to accurately predict the magnitude of the induced voltages to take proactive action and thereby safeguard electrical and electronic equipment if an incoming induced voltage is beyond the threshold.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study presents the behavior of surge protecting devices (SPDs) against transient over voltag... more This study presents the behavior of surge protecting devices (SPDs) against transient over voltages generated by cloud to ground (CG) flashes. Analysis revealed that lightning generated transient over voltages have a potential to impart detrimental effects on the SPDs. Moreover, it was concluded that comparisons between IEC laboratory impulse and the real transient voltages are remote due to factors such as peculiar time domain voltage profiles, random polarities, multiple surges with very narrow inter pulse durations in the order of microseconds. Further, observed that SPDs would not always retain within the limits specified by the manufactures under all circumstances.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was devised to investigate how the pitching phaser angle and the time domain voltage p... more This study was devised to investigate how the pitching phaser angle and the time domain voltage profile would compel surge protective devices (SPDs) to fall short in providing guaranteed protection. The study showed that the phaser angle at which the transient voltage pitching on the 230 V power frequency signal and its time domain voltage profile play a significant role in deciding the efficiency of the protection array and the amount of incident energy that infiltrates to reach the sensitive loads connected to the low voltage power installation. The analysis managed to prove that the selected SPD array can effectively reduce the harmful energy content of the impulse to around 40% and hence it is always advantageous to have a cascaded array than a single SPD. The study emphasized that it is practically impossible to have a universal protection system that can provide the same degree of protection under all circumstances. Moreover, the study further revealed that it is rational to design a SPD array considering regional and local lightning characteristics.
SPE International Hydraulic Fracturing Technology Conference and Exhibition, 2018
In this work, we assess the historical well performance for a mature gas condensate field in Oman... more In this work, we assess the historical well performance for a mature gas condensate field in Oman (the field name is designated as "BHA," where "BHA" is a pseudonym). The reservoirs of the BHA field are complex and have low permeabilities which results in substantial uncertainty in reserves estimation, which in turn has resulted in regular modifications of the booked volumes. To confine these booked volumes, we employed two techniques: "time-rate" analysis (or Decline Curve Analysis (DCA)) and "time-rate-pressure" analysis (or Rate Transient Analysis (RTA)). To perform the decline curve analysis work we used Microsoft Excel to match data using both the Modified Hyperbolic (MH) and Power-Law Exponential (PLE) DCA relations. We also used the Kappa Engineering product "Topaze" to conduct the Rate Transient Analysis (or RTA) by first estimating reservoir parameters and then performing a simulation history match of both the rate and press...
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was aimed at finding the performance of commercially available earth enhancing compoun... more This study was aimed at finding the performance of commercially available earth enhancing compound (EEC) under lightning conditions. Further to that, this is an extension of a previous study conducted by the same authors referring to the same EEC. The selected material seems to perform impressively under lightning conditions passing considerably large current values.The prepared EEC mixture and the setup was tested under dry conditions and exhibited low dynamic impedance characteristics for lightning impulse voltages. Ten-stage Marx-generator was used for the experiment, and due to high conductive nature of the material, HV supply between the sample was unable to increase more than few kV. Thus the 12 cm gap inside the material was complemented with an external air gap of 90 cm. The study was a comparison between “air-gap breakdown” and “air-gap plus materialgap breakdown”. The results confirmed a low impedance characteristic for the selected EEC and suggested a very low electric field inside the material gap. An approximate value for the impedance of the test setup was calculated from the collected data. A time window was selected during the steady current discharge appeared just after the point of current peak and the impedance curves for both experiments were compared at a previously defined point at the time axis. The impedance value for EEC setup was estimated to be in the region of 1 - 2 Ω.
IEEE Transactions on Electromagnetic Compatibility, 2019
This paper presents a study performed on time, frequency, and energy correlations of transient vo... more This paper presents a study performed on time, frequency, and energy correlations of transient voltages generated by the cloud to cloud discharges. It revealed that the energy embedded in transient voltages have been lumped over few segments of time domain voltage profile than uniquely scattering over the time span. The study further determined that the energy concentration becomes higher in and around the vicinity of the time domain voltage maxima or minima, and such high energy-concentrated segments confined to a minute time span in comparison to the total time span of the transient voltage. The study also established that there is a small time lead or lag between the time domain voltage maxima or minima and the time of energy maximize. Moreover, the analysis deduced that the time lead or time lag phenomenon, is not sensitive to the orientation of the time domain voltage profile, but fuelled by the pulse type. The response time of surge protective devices can become crucial if the stipulated clamping voltages of the protection devices fall close to local peaks of the transient voltages.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was conducted to understand what inherent limitations are associated with SPD arrays i... more This study was conducted to understand what inherent limitations are associated with SPD arrays in confronting with real transient over voltages. To devise the study 403 transient voltages were selected with different physical attributes covering a range of peak-to-peak voltages, starting from 175 V up to 2861 V. The sample comprises 218 cloud-to-clouds and 185 clouds to ground generated transient voltages with mean and median values of 676.80 V and 551.00 V respectively. Impulses were segregated into three subclasses based on their physical attributes and assessed the tendency to drift through the protection array once they placed at the+90, zero and -90 phaser angles. The study revealed that 100% of positive impulses in the sample could drift through the selected array once pitched at any phaser angle on 230 V, 50 Hz utility signal. It was observed that out of the negative pulses, 90.35% at +90, 74.39 % at zero and 42.21% at -90 phaser angles, could freely move through the array. ...
2018 34th International Conference on Lightning Protection (ICLP)
This paper presents an analysis done on the transient behavior of an external lightning protectio... more This paper presents an analysis done on the transient behavior of an external lightning protection system (LPS). The study was devised by modeling a Faraday's cage type LPS of a five-storied building on a MATLAB based electrical nodal network and simulating it against the 10/350 μ s lightning impulse with a peak current of 30 kA. The study focused on the down conductor material cross section area, ground impedance and the number of down conductors in the LPS to establish which factor or factors have more influence on the LPS performance. The simulation concludes that under the transient conditions the voltage dissipation on the LPS can reach several thousand volts and the peak branch current disbursements in the network are in the order of 2-2.5 kA. However, under poor ground conditions and less number of down conductors, voltage rise on the LPS system can elevate alarmingly, and branch currents tend to increase close to 7.5 kA. The study proved that the performance of the LPS and the magnitudes of the negative consequences of the associated secondary effects such as electromagnetic compatibility issues and risk associated with high step voltage issues, etc., have a close correlation with the ground impedance and the number of down conductors than that of the cross-section area of the down conductors.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was conducted to understand what inherent limitations are associated with SPD arrays i... more This study was conducted to understand what inherent limitations are associated with SPD arrays in confronting with real transient over voltages. To devise the study 403 transient voltages were selected with different physical attributes covering a range of peak-to-peak voltages, starting from 175 V up to 2861 V. The sample comprises 218 cloud-to-clouds and 185 clouds to ground generated transient voltages with mean and median values of 676.80 V and 551.00 V respectively. Impulses were segregated into three subclasses based on their physical attributes and assessed the tendency to drift through the protection array once they placed at the+90, zero and -90 phaser angles. The study revealed that 100% of positive impulses in the sample could drift through the selected array once pitched at any phaser angle on 230 V, 50 Hz utility signal. It was observed that out of the negative pulses, 90.35% at +90, 74.39 % at zero and 42.21% at -90 phaser angles, could freely move through the array. ...
IEEE Transactions on Electromagnetic Compatibility
— In modern world electronic and electrical appliances are used in abundance and such devices are... more — In modern world electronic and electrical appliances are used in abundance and such devices are constantly plugged onto the low voltage power installations (LVPI). Thus, savvy on amount of energies incident by induced voltages on overhead utility lines is important in protecting such equipment. In this paper, preliminary observation of incident energy by induced overvoltage signals on the interface between overhead utility lines and LVPI by cloud flashes is presented. Recorded waveforms were first segregated into cloud to ground (CG) and cloud to cloud (CC), then all recorded CC discharges categorized under three distinct wave shapes unipolar, bipolar and pulse-burst as described previously by [3] and [4]. Observed highest energy corresponding to the unipolar, bipolar and pulse-burst pulses were 0.56 J, 1.51 J and 7.30 J against the peak to peak voltages of 405 V, 662 V and 1056 V with pulse durations of 33.64 µs, 95.00 µs and 222.69 µs respectively. It was further observed that overall mean values of incident energies for unipolar and bipolar were 0.25 J and 0.69 J respectively, compared to 1.46 J observed for pulse-burst pulses. Analysis revealed that profile of the induced voltages and the pulse duration play a major role in deciding the magnitude of the incident energy. It was observed that common mode (CM) induced voltages with pulse-bursts type signatures inherently having longer pulse durations and hence contains comparatively higher energy than lenient pulses. Further, it was observed that in many occasions, there were multiple induced voltages appeared in the 200 ms window. Therefore, the outcome of the study lead to valid conclusions that CC discharges could incident sufficiently high energies to harm sensitive electronics and great attention should be made to confront with CC discharges with special attention to pulse burst type induced voltages.
—Investigations on the energy incident on low voltage power installation (LVPI) due to cloud to c... more —Investigations on the energy incident on low voltage power installation (LVPI) due to cloud to cloud (CC) discharges [3] revealed that incident energy can be driven microprocessor systems and electronic devices to malfunction, fault conditions or complete failure status. Therefore, it is worthwhile to investigate the energy concentration of the electric fields and common mode (CM) induced voltages on time-frequency common domain. The wavelet transformation technique is one of the proven tools that frequently use in many fields to investigate diverse natural phenomena [1], [2] and [4]. Accordingly wavelet technique was employed in this study to map the energy content of the selected signals onto time and frequency domains. This analysis revealed that energy content of the signal reach to its maximum just after the time domain voltage signal reach its local maximum or local minima. Also analysis indicates that equipment to be protected may become vulnerable to incoming surges if protection devices unable to clip the peak of the surge or delay to cut off the peak of the incoming signal.
— In modern world electronic and electrical appliances are used in abundance and such devices are... more — In modern world electronic and electrical appliances are used in abundance and such devices are constantly plugged onto the low voltage power installations (LVPI). Thus, savvy on amount of energies incident by induced voltages on overhead utility lines is important in protecting such equipment. In this paper, preliminary observation of incident energy by induced overvoltage signals on the interface between overhead utility lines and LVPI by cloud flashes is presented. Recorded waveforms were first segregated into cloud to ground (CG) and cloud to cloud (CC), then all recorded CC discharges categorized under three distinct wave shapes unipolar, bipolar and pulse-burst as described previously by [3] and [4]. Observed highest energy corresponding to the unipolar, bipolar and pulse-burst pulses were 0.56 J, 1.51 J and 7.30 J against the peak to peak voltages of 405 V, 662 V and 1056 V with pulse durations of 33.64 µs, 95.00 µs and 222.69 µs respectively. It was further observed that overall mean values of incident energies for unipolar and bipolar were 0.25 J and 0.69 J respectively, compared to 1.46 J observed for pulse-burst pulses. Analysis revealed that profile of the induced voltages and the pulse duration play a major role in deciding the magnitude of the incident energy. It was observed that common mode (CM) induced voltages with pulse-bursts type signatures inherently having longer pulse durations and hence contains comparatively higher energy than lenient pulses. Further, it was observed that in many occasions, there were multiple induced voltages appeared in the 200 ms window. Therefore, the outcome of the study lead to valid conclusions that CC discharges could incident sufficiently high energies to harm sensitive electronics and great attention should be made to confront with CC discharges with special attention to pulse burst type induced voltages.
When Alex Ferguson assumed duties in Manchester United club was belongs to Country Club status an... more When Alex Ferguson assumed duties in Manchester United club was belongs to Country Club status and his first challenge was to bring the club towards the Middle of the road and then to drive towards the team leader status. Sir Alex Ferguson did revolutionary changes in attitudes of club members, in disciplinary code, composition and combination of players and comprehensive training schemes etc., to uplift the levels of the players and reputation of the club. Alex Ferguson unleashed his born leadership skills in all domains to reshape the club structure, attitude and skill of the players to ultimate success to achieve long awaited dreams.
Sir Alex Ferguson is born leader having unbelievable mix of leadership skills. When he assumed the duties in United he had to start from grassroots level. To reshape the club to today’s level he applied his visionary leadership skill to imagine is way forward. To execute his vision, implement change and manage change he had an Autocratic and commanding leadership skill and sound transformational leadership skills to a great extent. In achieving his short term and long term objectives he had to employ his participative and delegative leadership very much strategically over the period of quarter century. Further Ferguson broadly demonstrated his situational, affiliative and coaching leadership skills in uplifting youngsters and groomed them to take the responsibilities in club.
“Safety” one of the most heard words from childhood and later as elders one of the most uttered ... more “Safety” one of the most heard words from childhood and later as elders one of the most
uttered words in anyone’s life. Further, countries in West, America and Australia have
been given top priority and implemented practical measures to ensure safety in all
aspects. But in Asian countries including Sri Lanka still safety is not considered as
integrated part of day to day life and hence repeatedly neglect basic safety norms and pay
the penalty by invaluable lives. Generally, most of the Lankans do not entertain safety
norms and the values of the lives, hence carelessly ignored basic minimum rules that
they should adhere to ensure self-protection, protection of the family circle and protection
of the general public.
The outcome of the analysis revealed that fatalities reported due to electricity is
alarmingly high in Sri Lanka comparing to the global yardstick. In much precious terms
Sri Lankan electrocution index is six times higher than global benchmark. According to
the outcomes of the research, carelessness and lack of awareness appeared to be the most
contributing factors for reported electrocutions and shown causality of more than 91%
and more than 54% respectively. Further, it also revealed that nearly 88% of the victims
are male. The analysis further surfaced that the majority of the victims are working age
population. It was observed that most of the electrocutions have been taken place in domestic
environment due to unsafe use of electricity for the day to day activities. Poor wiring and
increased usage of substandard equipment and accessories impart most of the domestic
level fatalities. In addition to that unsafe extension within the home and close vicinity of
the home also contributed a significant number of incidences. Further illegal power
connections obtained to electrification too involved domestic electrocutions as such
temporary installation does not inherently having necessary protection mechanisms to
switch off under electricity leakages electrical short circuiting
Number of electrocutions reported outside the home also much significant. Illegal use of
electricity to kill wild animals and cultivation safety has been contributed a lot to
increase the number of reported electrocutions in the country. It was also observed that
in April and December illegal power tapping reached to maximum analogues to the other
months.
Electrocution due to electricity usage at working places and working sites also found
contributing at large. Hired persons and employees became victims due to absence of
proper protective mechanisms at working places and work sites. Further breaching
minimum electrical line clearance when engaging with construction works, tree cutting,
building construction, etc., also found as some of the prominent reasons for electrocution
in Sri Lanka. In addition to that fault and negligence of electricity supply authorities also imparted
fatalities to some Sri Lankan. Fallen live wires, unprotected distribution boxes and
transformers etc., few such examples.
According to the analysis it was observed that house owners and illegal power tappers
were the most responsible groups for reported electrocutions. In addition to that
employers and area engineers also held some responsibility of reported electrocution.
Electrocutions reported in Sri Lanka have a prominent seasonal effect. Every year in the
month of April there is a huge local park has been reported and during the months of
November and December too, another distributed combined peak is available.
Further, in Sri Lanka there are 13 different root causes identified. Out of which 7 root
causes concluded as prominent and having a high significance to electrocutions, two root
causes are having medium significance and another 4 are having low significance
towards the reported electrocutions in Sri Lanka from 2008 to 2013.
This study disclosed that the IEC impulse is not an appropriate candidate to benchmark real trans... more This study disclosed that the IEC impulse is not an appropriate candidate to benchmark real transient over-voltages owing to have many discrepancies between them in terms of energy localization and frequencies that host such energies. However, the total energy content of the comparable IEC impulse is higher than the real transient voltages. Thus, once tested and passed the endurance at laboratories such an energy absorbing device would not fail at the field applications against single real transient voltage. However the same cannot be guaranteed against the swarm of impulses as the same cannot be tested at the test bench due to many practical constraints. The study revealed that IEC impulses can accommodate only 2.31% of the total energy until it reaches to 90% of the peak voltage, whereas the selected real transient impulses have shown that they could accommodate nearly 6% to 18% of the total incident energy before they reach to 90 % of the peak voltage. Moreover, when IEC impulse reaches to the peak, it can incident only a 9.71% of the total energy, but real transient voltages demonstrated that they have a capacity to incident nearly 30% to 45 % total energy embedded in the impulse.
2021 35th International Conference on Lightning Protection (ICLP) and XVI International Symposium on Lightning Protection (SIPDA)
This study employed wavelet transformation to disclose the spectrograms of IEC standard impulses ... more This study employed wavelet transformation to disclose the spectrograms of IEC standard impulses and real transient voltages generated by the cloud to ground discharges. The spectral details of each impulse were subdivided into different spectral clusters and the outcome was mapped into respective voltage levels and time to develop correlations. Eventually different protection voltage levels of commercially available surge protection devices (SPDs) and the voltage levels of different spectral clusters were compared to determine whether harmful energy infringements could be possible when the spectral clusters are wrapped by SPDs. This study revealed that all IEC impulses have identical spectral clusters whereas real transient voltages demonstrated that they are inherited with much random spectral distributions. Thus, planning for foolproof through benchmarking real transient impulses against IEC impulses would not produce guaranteed outcomes. Hence, a poor selection of clamping voltages may create a permanent window to infringing a small quantum of harmful energy on a constant basis into sensitive systems to trigger silent killing of basic functional units.
2020 International Symposium on Electromagnetic Compatibility - EMC EUROPE
Surge Protection Devices (SPDs) are being extensively used at present to safeguard electronic equ... more Surge Protection Devices (SPDs) are being extensively used at present to safeguard electronic equipment from lightning generated transient over-voltages. Despite SPDs being employed to protect electronic equipment, every year millions worth damages are being reported. Hence, isolation from the power grid would be considered as the best solution to prevent the infiltration of harmful energy contained in the transient over-voltages. But isolation cannot be performed by humans as they are not sensitive to imminent lightning discharges nor fast enough to respond post lightning events. Thus, there should be an extra-fast mechanism to detect imminent lighting discharge and perform a change-over from the utility supply to a local power supply. This study aims to device a machine learning solution which could be used to overcome such limitations in traditional SPDs. For the convenience of analysis, reported impulses were categorized into three signature types. Namely, pulse-burst, unipolar and bipolar. A data sample was taken which represents all above said signature types, was processed and fed into the Azure Machine Learning Studio in order to train a linear regression model. Such model yielded an R2 value of 0.7547. The strong positive correlation between the strength of the electric field and the magnitude of the induced voltage was thereby confirmed. The deployed solution had a mean accuracy of 87.82% of its predictions, confirming its ability to accurately predict the magnitude of the induced voltages to take proactive action and thereby safeguard electrical and electronic equipment if an incoming induced voltage is beyond the threshold.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study presents the behavior of surge protecting devices (SPDs) against transient over voltag... more This study presents the behavior of surge protecting devices (SPDs) against transient over voltages generated by cloud to ground (CG) flashes. Analysis revealed that lightning generated transient over voltages have a potential to impart detrimental effects on the SPDs. Moreover, it was concluded that comparisons between IEC laboratory impulse and the real transient voltages are remote due to factors such as peculiar time domain voltage profiles, random polarities, multiple surges with very narrow inter pulse durations in the order of microseconds. Further, observed that SPDs would not always retain within the limits specified by the manufactures under all circumstances.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was devised to investigate how the pitching phaser angle and the time domain voltage p... more This study was devised to investigate how the pitching phaser angle and the time domain voltage profile would compel surge protective devices (SPDs) to fall short in providing guaranteed protection. The study showed that the phaser angle at which the transient voltage pitching on the 230 V power frequency signal and its time domain voltage profile play a significant role in deciding the efficiency of the protection array and the amount of incident energy that infiltrates to reach the sensitive loads connected to the low voltage power installation. The analysis managed to prove that the selected SPD array can effectively reduce the harmful energy content of the impulse to around 40% and hence it is always advantageous to have a cascaded array than a single SPD. The study emphasized that it is practically impossible to have a universal protection system that can provide the same degree of protection under all circumstances. Moreover, the study further revealed that it is rational to design a SPD array considering regional and local lightning characteristics.
SPE International Hydraulic Fracturing Technology Conference and Exhibition, 2018
In this work, we assess the historical well performance for a mature gas condensate field in Oman... more In this work, we assess the historical well performance for a mature gas condensate field in Oman (the field name is designated as "BHA," where "BHA" is a pseudonym). The reservoirs of the BHA field are complex and have low permeabilities which results in substantial uncertainty in reserves estimation, which in turn has resulted in regular modifications of the booked volumes. To confine these booked volumes, we employed two techniques: "time-rate" analysis (or Decline Curve Analysis (DCA)) and "time-rate-pressure" analysis (or Rate Transient Analysis (RTA)). To perform the decline curve analysis work we used Microsoft Excel to match data using both the Modified Hyperbolic (MH) and Power-Law Exponential (PLE) DCA relations. We also used the Kappa Engineering product "Topaze" to conduct the Rate Transient Analysis (or RTA) by first estimating reservoir parameters and then performing a simulation history match of both the rate and press...
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was aimed at finding the performance of commercially available earth enhancing compoun... more This study was aimed at finding the performance of commercially available earth enhancing compound (EEC) under lightning conditions. Further to that, this is an extension of a previous study conducted by the same authors referring to the same EEC. The selected material seems to perform impressively under lightning conditions passing considerably large current values.The prepared EEC mixture and the setup was tested under dry conditions and exhibited low dynamic impedance characteristics for lightning impulse voltages. Ten-stage Marx-generator was used for the experiment, and due to high conductive nature of the material, HV supply between the sample was unable to increase more than few kV. Thus the 12 cm gap inside the material was complemented with an external air gap of 90 cm. The study was a comparison between “air-gap breakdown” and “air-gap plus materialgap breakdown”. The results confirmed a low impedance characteristic for the selected EEC and suggested a very low electric field inside the material gap. An approximate value for the impedance of the test setup was calculated from the collected data. A time window was selected during the steady current discharge appeared just after the point of current peak and the impedance curves for both experiments were compared at a previously defined point at the time axis. The impedance value for EEC setup was estimated to be in the region of 1 - 2 Ω.
IEEE Transactions on Electromagnetic Compatibility, 2019
This paper presents a study performed on time, frequency, and energy correlations of transient vo... more This paper presents a study performed on time, frequency, and energy correlations of transient voltages generated by the cloud to cloud discharges. It revealed that the energy embedded in transient voltages have been lumped over few segments of time domain voltage profile than uniquely scattering over the time span. The study further determined that the energy concentration becomes higher in and around the vicinity of the time domain voltage maxima or minima, and such high energy-concentrated segments confined to a minute time span in comparison to the total time span of the transient voltage. The study also established that there is a small time lead or lag between the time domain voltage maxima or minima and the time of energy maximize. Moreover, the analysis deduced that the time lead or time lag phenomenon, is not sensitive to the orientation of the time domain voltage profile, but fuelled by the pulse type. The response time of surge protective devices can become crucial if the stipulated clamping voltages of the protection devices fall close to local peaks of the transient voltages.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was conducted to understand what inherent limitations are associated with SPD arrays i... more This study was conducted to understand what inherent limitations are associated with SPD arrays in confronting with real transient over voltages. To devise the study 403 transient voltages were selected with different physical attributes covering a range of peak-to-peak voltages, starting from 175 V up to 2861 V. The sample comprises 218 cloud-to-clouds and 185 clouds to ground generated transient voltages with mean and median values of 676.80 V and 551.00 V respectively. Impulses were segregated into three subclasses based on their physical attributes and assessed the tendency to drift through the protection array once they placed at the+90, zero and -90 phaser angles. The study revealed that 100% of positive impulses in the sample could drift through the selected array once pitched at any phaser angle on 230 V, 50 Hz utility signal. It was observed that out of the negative pulses, 90.35% at +90, 74.39 % at zero and 42.21% at -90 phaser angles, could freely move through the array. ...
2018 34th International Conference on Lightning Protection (ICLP)
This paper presents an analysis done on the transient behavior of an external lightning protectio... more This paper presents an analysis done on the transient behavior of an external lightning protection system (LPS). The study was devised by modeling a Faraday's cage type LPS of a five-storied building on a MATLAB based electrical nodal network and simulating it against the 10/350 μ s lightning impulse with a peak current of 30 kA. The study focused on the down conductor material cross section area, ground impedance and the number of down conductors in the LPS to establish which factor or factors have more influence on the LPS performance. The simulation concludes that under the transient conditions the voltage dissipation on the LPS can reach several thousand volts and the peak branch current disbursements in the network are in the order of 2-2.5 kA. However, under poor ground conditions and less number of down conductors, voltage rise on the LPS system can elevate alarmingly, and branch currents tend to increase close to 7.5 kA. The study proved that the performance of the LPS and the magnitudes of the negative consequences of the associated secondary effects such as electromagnetic compatibility issues and risk associated with high step voltage issues, etc., have a close correlation with the ground impedance and the number of down conductors than that of the cross-section area of the down conductors.
2018 34th International Conference on Lightning Protection (ICLP), 2018
This study was conducted to understand what inherent limitations are associated with SPD arrays i... more This study was conducted to understand what inherent limitations are associated with SPD arrays in confronting with real transient over voltages. To devise the study 403 transient voltages were selected with different physical attributes covering a range of peak-to-peak voltages, starting from 175 V up to 2861 V. The sample comprises 218 cloud-to-clouds and 185 clouds to ground generated transient voltages with mean and median values of 676.80 V and 551.00 V respectively. Impulses were segregated into three subclasses based on their physical attributes and assessed the tendency to drift through the protection array once they placed at the+90, zero and -90 phaser angles. The study revealed that 100% of positive impulses in the sample could drift through the selected array once pitched at any phaser angle on 230 V, 50 Hz utility signal. It was observed that out of the negative pulses, 90.35% at +90, 74.39 % at zero and 42.21% at -90 phaser angles, could freely move through the array. ...
IEEE Transactions on Electromagnetic Compatibility
— In modern world electronic and electrical appliances are used in abundance and such devices are... more — In modern world electronic and electrical appliances are used in abundance and such devices are constantly plugged onto the low voltage power installations (LVPI). Thus, savvy on amount of energies incident by induced voltages on overhead utility lines is important in protecting such equipment. In this paper, preliminary observation of incident energy by induced overvoltage signals on the interface between overhead utility lines and LVPI by cloud flashes is presented. Recorded waveforms were first segregated into cloud to ground (CG) and cloud to cloud (CC), then all recorded CC discharges categorized under three distinct wave shapes unipolar, bipolar and pulse-burst as described previously by [3] and [4]. Observed highest energy corresponding to the unipolar, bipolar and pulse-burst pulses were 0.56 J, 1.51 J and 7.30 J against the peak to peak voltages of 405 V, 662 V and 1056 V with pulse durations of 33.64 µs, 95.00 µs and 222.69 µs respectively. It was further observed that overall mean values of incident energies for unipolar and bipolar were 0.25 J and 0.69 J respectively, compared to 1.46 J observed for pulse-burst pulses. Analysis revealed that profile of the induced voltages and the pulse duration play a major role in deciding the magnitude of the incident energy. It was observed that common mode (CM) induced voltages with pulse-bursts type signatures inherently having longer pulse durations and hence contains comparatively higher energy than lenient pulses. Further, it was observed that in many occasions, there were multiple induced voltages appeared in the 200 ms window. Therefore, the outcome of the study lead to valid conclusions that CC discharges could incident sufficiently high energies to harm sensitive electronics and great attention should be made to confront with CC discharges with special attention to pulse burst type induced voltages.
—Investigations on the energy incident on low voltage power installation (LVPI) due to cloud to c... more —Investigations on the energy incident on low voltage power installation (LVPI) due to cloud to cloud (CC) discharges [3] revealed that incident energy can be driven microprocessor systems and electronic devices to malfunction, fault conditions or complete failure status. Therefore, it is worthwhile to investigate the energy concentration of the electric fields and common mode (CM) induced voltages on time-frequency common domain. The wavelet transformation technique is one of the proven tools that frequently use in many fields to investigate diverse natural phenomena [1], [2] and [4]. Accordingly wavelet technique was employed in this study to map the energy content of the selected signals onto time and frequency domains. This analysis revealed that energy content of the signal reach to its maximum just after the time domain voltage signal reach its local maximum or local minima. Also analysis indicates that equipment to be protected may become vulnerable to incoming surges if protection devices unable to clip the peak of the surge or delay to cut off the peak of the incoming signal.
— In modern world electronic and electrical appliances are used in abundance and such devices are... more — In modern world electronic and electrical appliances are used in abundance and such devices are constantly plugged onto the low voltage power installations (LVPI). Thus, savvy on amount of energies incident by induced voltages on overhead utility lines is important in protecting such equipment. In this paper, preliminary observation of incident energy by induced overvoltage signals on the interface between overhead utility lines and LVPI by cloud flashes is presented. Recorded waveforms were first segregated into cloud to ground (CG) and cloud to cloud (CC), then all recorded CC discharges categorized under three distinct wave shapes unipolar, bipolar and pulse-burst as described previously by [3] and [4]. Observed highest energy corresponding to the unipolar, bipolar and pulse-burst pulses were 0.56 J, 1.51 J and 7.30 J against the peak to peak voltages of 405 V, 662 V and 1056 V with pulse durations of 33.64 µs, 95.00 µs and 222.69 µs respectively. It was further observed that overall mean values of incident energies for unipolar and bipolar were 0.25 J and 0.69 J respectively, compared to 1.46 J observed for pulse-burst pulses. Analysis revealed that profile of the induced voltages and the pulse duration play a major role in deciding the magnitude of the incident energy. It was observed that common mode (CM) induced voltages with pulse-bursts type signatures inherently having longer pulse durations and hence contains comparatively higher energy than lenient pulses. Further, it was observed that in many occasions, there were multiple induced voltages appeared in the 200 ms window. Therefore, the outcome of the study lead to valid conclusions that CC discharges could incident sufficiently high energies to harm sensitive electronics and great attention should be made to confront with CC discharges with special attention to pulse burst type induced voltages.
When Alex Ferguson assumed duties in Manchester United club was belongs to Country Club status an... more When Alex Ferguson assumed duties in Manchester United club was belongs to Country Club status and his first challenge was to bring the club towards the Middle of the road and then to drive towards the team leader status. Sir Alex Ferguson did revolutionary changes in attitudes of club members, in disciplinary code, composition and combination of players and comprehensive training schemes etc., to uplift the levels of the players and reputation of the club. Alex Ferguson unleashed his born leadership skills in all domains to reshape the club structure, attitude and skill of the players to ultimate success to achieve long awaited dreams.
Sir Alex Ferguson is born leader having unbelievable mix of leadership skills. When he assumed the duties in United he had to start from grassroots level. To reshape the club to today’s level he applied his visionary leadership skill to imagine is way forward. To execute his vision, implement change and manage change he had an Autocratic and commanding leadership skill and sound transformational leadership skills to a great extent. In achieving his short term and long term objectives he had to employ his participative and delegative leadership very much strategically over the period of quarter century. Further Ferguson broadly demonstrated his situational, affiliative and coaching leadership skills in uplifting youngsters and groomed them to take the responsibilities in club.
“Safety” one of the most heard words from childhood and later as elders one of the most uttered ... more “Safety” one of the most heard words from childhood and later as elders one of the most
uttered words in anyone’s life. Further, countries in West, America and Australia have
been given top priority and implemented practical measures to ensure safety in all
aspects. But in Asian countries including Sri Lanka still safety is not considered as
integrated part of day to day life and hence repeatedly neglect basic safety norms and pay
the penalty by invaluable lives. Generally, most of the Lankans do not entertain safety
norms and the values of the lives, hence carelessly ignored basic minimum rules that
they should adhere to ensure self-protection, protection of the family circle and protection
of the general public.
The outcome of the analysis revealed that fatalities reported due to electricity is
alarmingly high in Sri Lanka comparing to the global yardstick. In much precious terms
Sri Lankan electrocution index is six times higher than global benchmark. According to
the outcomes of the research, carelessness and lack of awareness appeared to be the most
contributing factors for reported electrocutions and shown causality of more than 91%
and more than 54% respectively. Further, it also revealed that nearly 88% of the victims
are male. The analysis further surfaced that the majority of the victims are working age
population. It was observed that most of the electrocutions have been taken place in domestic
environment due to unsafe use of electricity for the day to day activities. Poor wiring and
increased usage of substandard equipment and accessories impart most of the domestic
level fatalities. In addition to that unsafe extension within the home and close vicinity of
the home also contributed a significant number of incidences. Further illegal power
connections obtained to electrification too involved domestic electrocutions as such
temporary installation does not inherently having necessary protection mechanisms to
switch off under electricity leakages electrical short circuiting
Number of electrocutions reported outside the home also much significant. Illegal use of
electricity to kill wild animals and cultivation safety has been contributed a lot to
increase the number of reported electrocutions in the country. It was also observed that
in April and December illegal power tapping reached to maximum analogues to the other
months.
Electrocution due to electricity usage at working places and working sites also found
contributing at large. Hired persons and employees became victims due to absence of
proper protective mechanisms at working places and work sites. Further breaching
minimum electrical line clearance when engaging with construction works, tree cutting,
building construction, etc., also found as some of the prominent reasons for electrocution
in Sri Lanka. In addition to that fault and negligence of electricity supply authorities also imparted
fatalities to some Sri Lankan. Fallen live wires, unprotected distribution boxes and
transformers etc., few such examples.
According to the analysis it was observed that house owners and illegal power tappers
were the most responsible groups for reported electrocutions. In addition to that
employers and area engineers also held some responsibility of reported electrocution.
Electrocutions reported in Sri Lanka have a prominent seasonal effect. Every year in the
month of April there is a huge local park has been reported and during the months of
November and December too, another distributed combined peak is available.
Further, in Sri Lanka there are 13 different root causes identified. Out of which 7 root
causes concluded as prominent and having a high significance to electrocutions, two root
causes are having medium significance and another 4 are having low significance
towards the reported electrocutions in Sri Lanka from 2008 to 2013.