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Papers by John Prousalidis

Journal of Marine Engineering & Technology, 2014

Journal of Marine Engineering & Technology, 2015

Power supply quality (PSQ) problems in ship electrical systems are a major concern nowadays due t... more Power supply quality (PSQ) problems in ship electrical systems are a major concern nowadays due to the electrification of most equipment on board. Among PSQ problems, voltage transients and spikes are probably the most important as they can cause a range of malfunctions and even damage. The most efficient method of protection against spikes and transients is the installation of surge protection devices (SPDs). This paper presents a holistic methodology of selecting the most appropriate installation points in the ship's electricity grid on the one hand while not resulting in new problems on the other.

In this paper, an effort is made to identify the problems encountered during studying and modelin... more In this paper, an effort is made to identify the problems encountered during studying and modeling ship electric propulsion schemes. It is shown that where no existing models are available in programs like ATP/EMTP, new ones can be developed, with the new ones being able to cooperate with the rest of the computer package. In this way, several phenomena can be studied like those related to power quality on shipboard.

Electric power system simulation and analysis software has been used by energy utilities for the ... more Electric power system simulation and analysis software has been used by energy utilities for the analysis of power quality problems for many years. Power quality problems can be simplistically defined as cases where the electric quantities (voltage or current) diverge from the ideal. Power quality issues involve virtually all aspects of the power system operation, from steady state voltage regulation to the control of high-frequency transients caused by lightning or system switching operations. Since many power quality problems involve complex interactions between the power system, control systems and industrial equipment, simulation tools can be very helpful toward developing an understanding of the dynamics of power quality problems and then evaluating the effectiveness of various solution alternatives. The electric power grid of a ship can be regarded as a small-scale industrial power system. A ship’s electric energy system consists of a generator set and a distribution cabling s...

International Journal of Ocean Systems Management, 2008

Power Supply Quality (PSQ) has become an important concern for ship electric systems. Thus, devia... more Power Supply Quality (PSQ) has become an important concern for ship electric systems. Thus, deviations of voltage from nominal values and wave-shapes could cause several problems onboard. Considering that ship system electrification eventually dominates according to the All Electric Ship concept, PSQ will be a key-factor of the normal operation, survivability and safety aboard. The paper provides a coherent description and categorisation of the PSQ phenomena (causes, consequences, characteristic parameters etc.) highlighting similarities and differences between terrestrial systems and ship systems in terms of these phenomena. This overview is enriched by cross-references to relevant standards applied in shipboard applications.

Proceedings of Marine Electrical and Control Systems Safety Conference (MECSS), 2019

Following the global concern and IMO directives, in particular for greener shipping, ships and po... more Following the global concern and IMO directives, in particular for greener shipping, ships and ports tend to become more efficient in terms of environmental friendliness, energy consumption as well as services provided. This paper deals with facing the challenges emerged within this framework, as in the ship case, certain retrofitting works have to take place onboard a ship such as the installation of water ballast treatment systems, scrubbers, cold-ironing facilities, and LED lights. The paper discusses the necessity to perform a number of studies (e.g. harmonic distortion, short-circuit, arc-flash etc) so that major safety requirements are met, while on the other hand, the electric energy system has to be tuned to a significant extent so that it operates in an optimum manner which is most often interpreted as minimum fuel consumption and emissions. Further, the paper makes a similar discussion for the case of the ports.

Journal of Marine Engineering & Technology, 2008

Journal of Marine Engineering & Technology, 2010

, specialises in electric energy systems and electric propulsion schemes on shipboard installatio... more , specialises in electric energy systems and electric propulsion schemes on shipboard installations. Investigating the influence of zero sequence impedance in ship ungrounded electric networks * According to marine electrical literature, the term 'High Voltage' refers to voltage levels above 1000V (1kV).

A design issue of ship electric power systems, conventional or All Electric Ship (AES), is to mod... more A design issue of ship electric power systems, conventional or All Electric Ship (AES), is to moderate power quality problems caused by the so-called "pulsed loads", i.e loads with periodic high power consumption in short time intervals, causing the relative power supply quality phenomenon referred to as "voltage/frequency modulation". Voltage/frequency modulation may affect the operation of several sensitive electrical ship subsystems. NATO standard, STANAG 1008, imposes certain design constraints for pulsed loads, so that in a Low Voltage (LV) ship service power supply system the voltage and frequency modulation do not exceed 2% and 0,5%, respectively. These constraints are related with two inequalities involving the power factor of the pulsed load and the ratio between the apparent power of the pulsed load and the full rated apparent power of the supply at the occurrence of the pulse. In a former work of the authors, it was shown that STANAG 1008 guideline for conventional ship electric systems seems to be a method leading to a rough estimation of pulsed loads limits, because it does not take into account certain parameters of the pulsed load and the power grid affecting the entire phenomenon, e.g. the periodicity, the duty cycle of the pulsed load etc. In this paper, an effort is made to examine and validate the aforementioned STANAG 1008 design constraints in the frame of the All Electric Ship (AES) concept. The voltage and frequency modulation in the LV sub-networks of a AES is studied via simulations in Matlab / Simulink, taking into account various parameters affecting the entire phenomenon such as: pulsed load period, duty cycle and point connection, the technical characteristics of the generators (like subtransient reactance, intertia) and their associated frequency and voltage controllers (like governor and automatic voltage regulator (AVR) gains etc), the service load factor of the generator at the time of the pulsed load occurrence, the equivalent length of the cable between the pulsed load and the generator etc. The respective results are presented and the effects of the respective parameters on the pulsed load limit curve of STANAG 1008 are commented comparing three different cases of power systems: conventional ship, AES with pulse load connected to low voltage system, AES with pulse load connected to high voltage system. Finally, general conclusions are derived for the effect of the aforementioned parameters on voltage/frequency modulation and on maximum acceptable pulsed load installed power.

2009 IEEE Electric Ship Technologies Symposium, 2009

The target of this paper is twofold: primarily to highlight the significant effect of certain pow... more The target of this paper is twofold: primarily to highlight the significant effect of certain power supply quality problems on the normal operation of the entire ship grid, namely inrush currents and voltage dips due to manoeuvring thruster motor starting-ups. At a second stage, the paper aims at recommending some amelioration of standardization status. Hence, the authors suggest the exploitation of existing experience on pulsed load standardizing, taking into account the resemblance between the systems. The study is enriched by actual case studies and simulations in PSCAD computer program. .

Journal of Marine Engineering & Technology, 2014

Journal of Marine Engineering & Technology, 2015

Power supply quality (PSQ) problems in ship electrical systems are a major concern nowadays due t... more Power supply quality (PSQ) problems in ship electrical systems are a major concern nowadays due to the electrification of most equipment on board. Among PSQ problems, voltage transients and spikes are probably the most important as they can cause a range of malfunctions and even damage. The most efficient method of protection against spikes and transients is the installation of surge protection devices (SPDs). This paper presents a holistic methodology of selecting the most appropriate installation points in the ship's electricity grid on the one hand while not resulting in new problems on the other.

In this paper, an effort is made to identify the problems encountered during studying and modelin... more In this paper, an effort is made to identify the problems encountered during studying and modeling ship electric propulsion schemes. It is shown that where no existing models are available in programs like ATP/EMTP, new ones can be developed, with the new ones being able to cooperate with the rest of the computer package. In this way, several phenomena can be studied like those related to power quality on shipboard.

Electric power system simulation and analysis software has been used by energy utilities for the ... more Electric power system simulation and analysis software has been used by energy utilities for the analysis of power quality problems for many years. Power quality problems can be simplistically defined as cases where the electric quantities (voltage or current) diverge from the ideal. Power quality issues involve virtually all aspects of the power system operation, from steady state voltage regulation to the control of high-frequency transients caused by lightning or system switching operations. Since many power quality problems involve complex interactions between the power system, control systems and industrial equipment, simulation tools can be very helpful toward developing an understanding of the dynamics of power quality problems and then evaluating the effectiveness of various solution alternatives. The electric power grid of a ship can be regarded as a small-scale industrial power system. A ship’s electric energy system consists of a generator set and a distribution cabling s...

International Journal of Ocean Systems Management, 2008

Power Supply Quality (PSQ) has become an important concern for ship electric systems. Thus, devia... more Power Supply Quality (PSQ) has become an important concern for ship electric systems. Thus, deviations of voltage from nominal values and wave-shapes could cause several problems onboard. Considering that ship system electrification eventually dominates according to the All Electric Ship concept, PSQ will be a key-factor of the normal operation, survivability and safety aboard. The paper provides a coherent description and categorisation of the PSQ phenomena (causes, consequences, characteristic parameters etc.) highlighting similarities and differences between terrestrial systems and ship systems in terms of these phenomena. This overview is enriched by cross-references to relevant standards applied in shipboard applications.

Proceedings of Marine Electrical and Control Systems Safety Conference (MECSS), 2019

Following the global concern and IMO directives, in particular for greener shipping, ships and po... more Following the global concern and IMO directives, in particular for greener shipping, ships and ports tend to become more efficient in terms of environmental friendliness, energy consumption as well as services provided. This paper deals with facing the challenges emerged within this framework, as in the ship case, certain retrofitting works have to take place onboard a ship such as the installation of water ballast treatment systems, scrubbers, cold-ironing facilities, and LED lights. The paper discusses the necessity to perform a number of studies (e.g. harmonic distortion, short-circuit, arc-flash etc) so that major safety requirements are met, while on the other hand, the electric energy system has to be tuned to a significant extent so that it operates in an optimum manner which is most often interpreted as minimum fuel consumption and emissions. Further, the paper makes a similar discussion for the case of the ports.

Journal of Marine Engineering & Technology, 2008

Journal of Marine Engineering & Technology, 2010

, specialises in electric energy systems and electric propulsion schemes on shipboard installatio... more , specialises in electric energy systems and electric propulsion schemes on shipboard installations. Investigating the influence of zero sequence impedance in ship ungrounded electric networks * According to marine electrical literature, the term 'High Voltage' refers to voltage levels above 1000V (1kV).

A design issue of ship electric power systems, conventional or All Electric Ship (AES), is to mod... more A design issue of ship electric power systems, conventional or All Electric Ship (AES), is to moderate power quality problems caused by the so-called "pulsed loads", i.e loads with periodic high power consumption in short time intervals, causing the relative power supply quality phenomenon referred to as "voltage/frequency modulation". Voltage/frequency modulation may affect the operation of several sensitive electrical ship subsystems. NATO standard, STANAG 1008, imposes certain design constraints for pulsed loads, so that in a Low Voltage (LV) ship service power supply system the voltage and frequency modulation do not exceed 2% and 0,5%, respectively. These constraints are related with two inequalities involving the power factor of the pulsed load and the ratio between the apparent power of the pulsed load and the full rated apparent power of the supply at the occurrence of the pulse. In a former work of the authors, it was shown that STANAG 1008 guideline for conventional ship electric systems seems to be a method leading to a rough estimation of pulsed loads limits, because it does not take into account certain parameters of the pulsed load and the power grid affecting the entire phenomenon, e.g. the periodicity, the duty cycle of the pulsed load etc. In this paper, an effort is made to examine and validate the aforementioned STANAG 1008 design constraints in the frame of the All Electric Ship (AES) concept. The voltage and frequency modulation in the LV sub-networks of a AES is studied via simulations in Matlab / Simulink, taking into account various parameters affecting the entire phenomenon such as: pulsed load period, duty cycle and point connection, the technical characteristics of the generators (like subtransient reactance, intertia) and their associated frequency and voltage controllers (like governor and automatic voltage regulator (AVR) gains etc), the service load factor of the generator at the time of the pulsed load occurrence, the equivalent length of the cable between the pulsed load and the generator etc. The respective results are presented and the effects of the respective parameters on the pulsed load limit curve of STANAG 1008 are commented comparing three different cases of power systems: conventional ship, AES with pulse load connected to low voltage system, AES with pulse load connected to high voltage system. Finally, general conclusions are derived for the effect of the aforementioned parameters on voltage/frequency modulation and on maximum acceptable pulsed load installed power.

2009 IEEE Electric Ship Technologies Symposium, 2009

The target of this paper is twofold: primarily to highlight the significant effect of certain pow... more The target of this paper is twofold: primarily to highlight the significant effect of certain power supply quality problems on the normal operation of the entire ship grid, namely inrush currents and voltage dips due to manoeuvring thruster motor starting-ups. At a second stage, the paper aims at recommending some amelioration of standardization status. Hence, the authors suggest the exploitation of existing experience on pulsed load standardizing, taking into account the resemblance between the systems. The study is enriched by actual case studies and simulations in PSCAD computer program. .