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Electromagnetic field evaluation and EMI on board during a marine geophysical data acquisition (COSMEI)
Measurement 147 (2019) 106889
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Electromagnetic field evaluation and EMI on board during a marine geophysical data acquisition (COSMEI) Vincenzo Di Fiore a,⇑, Michele Punzo a, Nicola Pelosi a, Paolo Scotto di Vettimo a, Michele Iavarone a, Francesca Budillon a, Giovanni Zeni b, Fabrizio Lirer a a b
ISMAR – CNR Institute of Marine Sciences, UOS, Naples, Italy IREA – CNR Institute for Electromagnetic Sensing of the Environment, Naples, Italy
a r t i c l e
i n f o
Article history: Received 26 November 2018 Received in revised form 1 July 2019 Accepted 30 July 2019 Available online 2 August 2019 Keywords: EMI EMC Geophysical oceanographic survey Inductance
a b s t r a c t When performing oceanography measurements, it is critical to assess the presence of the noise sources that could affect the measured data and lead to wrong interpretation of the results. This paper report the result of an oceanography survey conducted by ISMAR-CNR, Naples, in the north-eastern marine sector of the Ischia Island and assess the influence of EMI on the measured results. The analyzed measurements of the Electric and Magnetic fields showed values of the E up to 0.82 V/m and of B up to 85 lT. By assuming a standard conductor, an inductance L up to 47 X on the cable corresponding to an induced electromotive force of 1184 mV was calculated. Also the experimental data show the EMI increase in site where the Pearson index correlation is higher. The results demonstrate that in an oceanographic survey planning, a preliminary electromagnetic screening is advisable to optimize the measurement setup. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction With the growing density of electrical and electronic systems onboard contemporary naval platforms, electromagnetic interference and compatibility aspects have acquired great significance. A large number of equipment, emitting signals over a wide range of the electromagnetic spectrum, have to co-exist with sensitive surveillance systems with similar spectrum onboard a warship. Further, in the process of continuous upgrading and modernization of a warship required to keep abreast with emerging technologies, state of the art equipment is installed from time to time to augment/retrofit existing systems in the already dense electromagnetic (EM) environment onboard. Some authors studied Electromagnetic Compatibility (EMC) effect during the ship navigation. Operational problems arising from ship-board Electromagnetic Interference (EMI) generated by installed electrical and electronic system have been of increasing concern to the Navy for many years. By 1972, such problems had grown to serious proportions, as reported from fleet Commanders revealing that shipboard EMI were high to degrade vital functions and system performance [1]. In [2] they showed that the evaluation and optimization model can achieve the overall quantitative ⇑ Corresponding author. E-mail address: [email protected] (V. Di Fiore). https://doi.org/10.1016/j.measurement.2019.106889 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved.
control of electromagnetic compatibility in telecommunication system. As an example, when the interference between two topside antennas is predicted to be above a selected tolerable level, the antennas can be relocated on the ship, consistent with other ship design constraints, and the simulation is then rerun. This process is repeated until a configuration is achieved where the severity of the interference is reduced to a level that is acceptable to ship designers [3]. In [4] a numerical analysis including measurements of the magnetic decoupling between these loops has shown the importance of a low bonding resistance. Because the signal cables can be affected by EMI effect, it is important to study the electromagnetic field which can induce electrical noise. In our case, simultaneous acquisition of geophysical data in addition to sources of electromagnetic fields can generate noise in the measured signals. These sources can produce fields, variable with time, in the electromagnetic spectrum that extends from static fields to infrared radiation. Compatibility and interferences electromagnetic problems can affect the electrical-electronic equipment on board, the engine equipment, as well as the entire ship system. The increasingly widespread use of electronic components and instrumentation and the use of signal equipment coupled with power systems has given rise in recent years to several problems
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concerning many disciplines in the fields of industrial, electrical and electronic engineering considered first disciplines in its own right. Each electric-electronic device must be considered capable of emitting (in a more or less relevant way) electromagnetic radiations that can invest other equipment and in the same way it can be subjected to the radiations present in the environment in which it is installed. The EMC refers to the aptitude of an apparatus or a system to function correctly, in a given environment, without being subject to anomalies or failures caused by electromagnetic radiation present in the environment considered and without producing, in turn, harmful radiation for other equipment or systems present in the same environment. An electromagnetic compatibility problem is a problem of environmental compatibility of an apparatus or of a system with respect to the level of disturbances or with respect to the degree of sensitivity to disturbances of other apparatuses or systems present in the same environment. Therefore, ECM can be seen as a particular case of environmental pollution, where the ‘‘polluting agents” are electromagnetic waves. EMI, on the other hand, can be irradiated by the presence of an ‘‘interference source”, i.e. a device capable of intentionally or not emitting an electromagnetic wave which can be received by electronic systems that are not shielded and therefore insensitive to such radiation. In conduction EMI, there is a physical connection, of parasite type, between devices that should be electrically isolated (i.e. a path of parasitic conductive type is created between two devices); in EMI by induction (diaphony), the problems of EMI are linked to inductive or capacitive coupling between two conductors, in the absence of a direct physical connection. At the lowest frequency, when the fields are characterized by slow variations with time, or, more generally, when the exposure to electromagnetic fields occurs at distances from the short source with respect to the wavelength, the Electric fields (E) and the Magnetic fields (H) are generally considered separately. At higher frequencies or, more generally, at high distances from the source with respect to the wavelength, the electric fields and magnetic fields are closely related to each other: from the measurement of one of them it is generally possible to calculated the other one. At the basis there is the consideration of the physical phenomenon related to the production of a magnetic field by an electric current and, as reported in Table 1 The electromagnetic field sources can be divided into intentional and unintentional radiating sources. The intentional radiators are those that emit electromagnetic waves and have characteristics known in terms of amplitude, polarization, frequency stability and emission of spurious harmonics. The waveform can assume different trends depending on the transmission scheme adopted. Simple cases consist of amplitude (AM), frequency (FM) or phase (PM) signals modulation, and coding techniques for subcarriers as in the OFDM communications. Radars, on the other hand, typically use short microwave pulse packets of duration in the microsecond range. Unintentional radiators are devices that emit electromagnetic waves as a secondary effect (loss of radiation) compared to the purpose for which they are designed as induction and/or radio frequency heating systems, or even applications for industrial processes, such as welding or fusions arc or microwave. The harmonized technical standards for the introduction of products on the market impose severe limitations on unintentional emissions. However, there are cases with non-negligible local effects observed above all in the industrial field due to the nature of a processing or plant with high power. The Ischia Electric Magnetic Seismic Oceanographic Campaign (COSMEI) was born following the seismic event of Mw 3.9 on date 21 August 2017 and time 20:57:51 (Timezone Italy) in region 1 km
Table 1 Analogy between electric field and magnetic field.
Symbol Mathematical operator Force Expression of Field
Driving Force Produces Limited by Favored by
Lorentz Force Law AmpereMaxwell Law Where: ! E ! B q !
v
! J K ! ur Ka Km
l0 e0
! r
Electric field
Magnetic induction field
! E q
! B ! qv K
! ! F ¼ qE ! ! E ¼ K a rq2 ur
! ! ! F ¼ qv K B ! ! ! l q ! ! B ¼ K m rq2 v K ur ¼ 4p0r2 v Kur
Electric circuit
Magnetic circuit
Electromotive Force – EMF Current (I) [Ampere, A] Resistance, q, [ohm, X] Conductivity, r, [Siemens per meter (Sm1)] ! ! ! ! F ¼ q E þ qv xB
Magnetomotive Force – MMF
!
!
r B ¼ l0
Flux (/) [Weber, Wb] Reluctance, R [Henry1, H] Permeance, P, [Henry, H]
! ! J þ e0 ##tB
Electric field vector [Volt per metre, V/m] Induced Magnetic flux density vector [Tesla, T] Electric charge [Coulomb, C] Vector representative of the speed of the moving electric charge Electric current density [Ampere per square metre, A/m2] Vectorial product between vector Position vector Electric constant Magnetic constant Magnetic permeability of free space Electric permeability of free space Curl Operator
SW Casamicciola Terme [5]. The aim of the oceanographic survey was to acquire geophysical data as mono/multichannel seismic data, gradiometer magnetic data and resistivity data in the north-eastern marine sector of the Ischia Island for the reconstruction of tectonic and volcanic structures potentially originating seismic events. During this survey, a study of radio frequency (RF) and low frequency (LF) magnetic fields was also performed. Acquisition data was conducted by oceanographic ship ‘Minerva Uno’ of the National Research Council (Fig. 1).
Fig. 1. Oceanographic Ship ‘‘Minerva Uno”.
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The main aim of the present paper is the evaluation of electromagnetic emission of the devices present on board in terms of electric field E with frequency band 100 kHz–6.5 GHz and the magnetic fluxes density B in the frequency range frequency between 5 Hz and 400 kHz and therefore evaluate the potential interference with the geophysical data signal during the measurement survey. The produced interferences result in disturbances conducted on the cables that are current on power lines (but also in the output and control lines) of the devices. According to the EN55014 standard, the harmonic components from 150 kHz to 30 MHz are relevant, and in these frequency range the common mode disturbances and differential mode disturbances should be classified, and therefore, different filtering techniques are needed. Common mode disturbances (MC, also called: asymmetric mode) propagate with the same phase along two or more conductors to ground. The line disturbance can be imagined as an impulse that equally invests the two conductors by generating a current to ground (as can be caused for example by lightning). Differential mode disturbances (MD, also called: symmetric mode or normal mode) propagate with opposite phases along the phase and neutral conductors so as to close without affecting the ground conductor. Line disturbances can be generated for example by inductive loads that are connected and disconnected, the over voltages that are generated between the two conductors give rise to differential mode disturbances. Generally, differential mode disturbances involve the lower part of the spectrum.
Therefore, the electromagnetic field resulting in any observation point is the vectorial sum of many contributions, coming from multiple sources, operating at different frequencies; in the Fourier domain we have [7]:
2. Electric (E) and magnetic (B) field measurement
n X ! ! E tot ðx; t Þ ¼ E ð xi ; t Þ
n X ! ! B tot ðx; t Þ ¼ B ð xi ; t Þ
It is known that B and E fields are connected by Maxwell equation as:
!! @B r ;t !! r E r ;t ¼ @t
!
! qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 2 E ðx; y; z; t Þ ¼ Ex ðtÞ þ Ey ðtÞ þ Ez ðt Þ;
ð1Þ
and
! qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 2 B ðx; y; z; t Þ ¼ Bx ðt Þ þ By ðtÞ þ Bz ðt Þ;
ð2Þ
ð5Þ
! where r is curl operator. The curl is a measure of the rotation of a vector field. Eq. (5) is known as Faraday’s Law of induction. This law establishes that an electric field can be generated from a time variant of the magnetic field induction. In matricial form on the window time WT:
0 i ! @ B ðx; y; z; tÞ B @ ¼ det@ @x @t Ex
The measurements of the electromagnetic fields are normally performed in the frequency domain. They can be classified into broadband and narrowband. The broadband frequencies are performed with the use of instruments which, within a certain frequency interval, have a sensitivity almost independent of the frequency itself and provide the global value of the electric or magnetic field in the considered interval; the narrowband measurements, also called selective, are performed with the use of instruments that can be tuned to a selected frequency and which provide the intensity of the field corresponding to the default frequencies. The components of the electromagnetic field can be measured with the use of antennas as small dipoles in the case of an electric field or, equivalently, with loop sensors in the case of a magnetic field. The isotropic probes for broadband measurements contain three sensible elements (dipoles or loops) arranged in the three orthogonal directions. These probes measure the result of field strength (electric or magnetic) expressed as a square root of the sum of the squares of the field strengths along the three directions of the space (x, y, z) without considering the single phases of the probes themselves. Therefore, the total electric (E) and magnetic (B) fields are given by the following formulas [6]:
ð4Þ
i¼1
The measurement of the intensity of electromagnetic fields can be carried out indirectly using environmental measurements of the following quantities: – Electric Field E (V/m); – Magnetic induction B (lT).
ð3Þ
i¼1
j
k
@ @y
@ @z
Ey
Ez
1 C A
ð6Þ 8t2WT
! @ B ðx; y; z; t Þ @ @ @ ¼ Ez ðt Þbi þ Ey ðtÞ b k þ E ðt Þbj @t @y @x @z x @ @ @ Ex ðt Þ b k þ Ey ðt Þbi þ E ðt Þbj @y @z @x z ! @ B ðx; y; z; t Þ @Ez ðt Þ @Ey ðt Þ b @Ex ðtÞ @Ez ðtÞ b ¼ iþ j @t @ ðyÞ @ ðzÞ @ ðzÞ @ ðxÞ @Ey ðt Þ @Ex ðt Þ b k; þ @ ð xÞ @ ðyÞ
ð7Þ
ð8Þ
Eq. (8) implies that when E is ‘‘conservative” or irrotational, B is constant in (x, y, z, t) domains. 3. Measurement points The ship size and the used materials can influence the electromagnetic propagation; the choice and the sizing of the onboard equipment is depended on the type of ship and its required missions and safety aspects. Considering the ship characteristic, equipment onboard and the power network produced, we used two system sampler-probes and in particular: E field sampler with isotropic/multicomponent probe operating in an overall frequency range between 100 kHz and 6.5 GHz and compatible with electric field strengths up to 350 V/m. B field sampler with isotropic/multicomponent probe operating in an overall frequency range between 5 Hz and 400 kHz and compatible with magnetic field strength up to 1012 lT. Both measurement systems have been calibrated by a certified laboratory. Dataset was acquired by personal laptops connected to the previous instrumentation and exploiting specifically dedicated software. Fig. 2 depicts a block diagram of the measurement set-up. For a complete analysis also the temperature and humidity values were recorded.
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Fig. 2. The measure technique uses both hardware, for the signal acquisition (triazial probe, filters and amplifiers), and software for signal recording and analysis.
Onboard tests were conducted on 66 points differently distributed (Fig. 3a–d) and the measurement taken for 5 days. The measurements were carried out using a tripod stands of dielectric material at 1.6 m from floor. During the measurement, the operators remained at a distance from the probe in order not to influence the measurement of the field and furthermore all the personal communication devices were placed in airplane mode. As far as possible, we tried to maintain the verticality of the probe and in particular the measurements were made by controlling the pitch and roll of the ship (1–5 degrees max). Tables 2–4 show the most important technical characteristics of the instruments used; Table 5 shows instead the data acquisition parameters. Table 6 shows the main technical characteristics of the N/O Minerva Uno. About the electric/magnetic sources present on the ship, we identified the potential source of high frequency E field (Table 7). For electric and diesel engines, a measurement of field B was also carried out in the range that includes 50 Hz (engine room, etc.).
4. Results During the oceanographic survey, different geophysical data were acquired. Specifically: gradiometric/magnetometric data, geoelectrical data, high-frequency single-channel seismic data (CHIRP), multi-channel seismic data and multi-beam data. The critical point is that the data are acquired simultaneously implying a strong vulnerability to the attack of electromagnetic-type external noise. In particular, the geophysics measurements are translated into conversion parameters as micro-tension and field E and B expressed in mV and mT respectively. Therefore, given the magnitude of the value of the data, the measure is sensitive to EMI due inevitably to the instrumentation used for navigation but also for communication and other showing the shielding of the electronic system was not correctly designed. Thirty three measurement stations relative to two bridges (Pagliolo deck and Coperta deck) were selected and the data were collected in areas where research activities were performed. The measurements were performed in accordance with the standard Norma CEI 211-6 [8] and Norma CEI 211-7 [9]. 4.1. Field E (100 k Hz–6.5 MHz) N. 14 measurements were performed at Pagliolo deck (Fig. 4a). For each measure the 50, 75 and 90 percentiles were determined; the average of the values was calculated taking into account the restrictions of the standard deviation set at a maximum of 11% from the average value.
Table 8 shows all the values where it is possible to highlight the significance of the data and in particular the value of the average with the different percentiles. Fig. 4a shows the results of the measurements for the Pagliolo deck (measurements 1–14); the maximum values are evident near point 12, point 5 and point 11. The maximum values in points 5 and 11 are due to the presence of antennas placed at bow and stern respectively, while for point 12 the maximum value is connected to the presence of the acquisition systems of the physical laboratory present at the upper deck (Coperta deck). Fig. 4b shows the contouring of the electric field E for the Coperta deck (measurements 1a-19a). The situation is almost similar to the Pagliolo deck with the difference that in the central area of the ship for measures 6a and 7a there is an extension of the maximum of the field E. 4.2. Magnetic induction field B (5 Hz–400 kHz) The measurement of the field B was carried out in the same location and using the same measurement points of the field E (Table 9). For the Pagliolo deck (Fig. 5a), the maximum B field values, between 50 and 90 lT, are located at the bow (measures 2, 5) and in the left side of the vessel (measures 6, 7, 8, 12). Moreover, on the right ship side, from the bow up to about half of its length, an anomaly of the B field can be observed. The anomalies in the central area on the left side are probably connected with the presence of the engine room, while on the bow area and right side are due to the presence of current generators. For the Coperta deck (Fig. 5b) we find a maximum of 80 mT in the stern area (measure 10a) and in the bow area (measure 11a) and a maximum in the front central area of the ship (measurements 1a and 2a). These maximums are due to the presence of a winch in the stern area, and current generators in other areas. Fig. 6a and b show the Pearson correlation between the field E and the B for each individual deck of the ship. The Pearson product-moment correlation coefficient is a statistical measurement of the correlation (linear association) between two sets of values and is given by the formula:
P ðx xÞð y yÞ ; r ¼ qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi P P ðx xÞ2 ð y yÞ2
ð9Þ
where x and y are sample means of two arrays of values. The areas where the disturbance effect is emphasized are evident; moreover, the zones where the effects of E and B show peak values are clear.
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Fig. 3. a) Instrumentation used for the measurements. NHT310 (sampler), 10B and 01E probes. b) Measurement station indoor the ship. c) Measurement station outside the ship by 01 E probe. d) Measurement station indoor the ship by 10B probe.
Table 2 Technical specification MICRORAD NHT310.
Table 3 Technical specification MICRORAD 01E probe.
Electromagnetic field device – microrad NHT310
Microrad 01E probe
Fields Frequency Values Dynamic range
Fields Frequency range Measurement range Dynamic range Sensor type Directivity
E, B, H Hz DC – 40 GHz mW/cm2, W/m2, V/m, A/m, Tesla dB 144
V/m Hz V/m dB
Electric (E) 100 kHz–6.5 GHz 0.20–350 66 Diode dipoles Isotropic
5. EMI evaluation EMC is typically achieved by the decoupling of Common Mode (CM) current loops at the inside and outside of current boundaries. This can even be made by cable terminations instead of shielding
walls, to create a barrier for these currents. It is known that EMI coupling is the transfer of EM energy from the terminals of a transmitting system into the terminals of a receiving system. Generally, EMI coupling in the far-field region of an antenna depends on the
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Table 4 Technical specification MICRORAD 10B probe. Microrad 10B probe Fields Frequency range Measurement range Dynamic range Sensor type Directivity
lT
Magnetic (B) 5 Hz–400 kHz 0.1–1012 80 Coils Isotropic
Hz lT dB
Table 5 Acquisition parameters. Data acquisition parameters Parameters Acquisition Time Sample Time Viewable quantity
E, B, Temperature, Humidity min 30 s 5 Instantaneous ACT, Maximum and Average
Table 6 N/O ‘‘Minerva Uno” main technical features (from: http://www.sopromar.it/it/minervauno.htm). Parameters
Quantity
Length overall Width overall Full load draft Suez gross (net) Gross tonnage Main Engines Max (average) speed Class Category
46.6 m 9.0 m 4.60 m 700 t 615 TS Maximum power 2 746 kW at 1800 RPM 12.5 (10.8) kN Special Service Regional
Frequency range
VHF MF HF INMANSAT RADAR GPS NAVTEX
156.05 MHz 1.605 MHz 4 MHz 1626.5 MHz 8000 MHz 1575.42 MHz 0.518 MHz
162.5 MHz 3.8 MHz 27.5 MHz 1660.5 MHz 12000 MHz 1227.6 MHz 0.490 MHz
gain of the transmitting antenna, gain of the receiving antenna and free space propagation losses, and it is given by [10,11]:
Cðf ; t; d; pÞ ¼ Gt ðf ; t; d; pÞ þ Gr ðf ; t; d; pÞ Lp ðf ; t; d; pÞ
ð10Þ
where Cðf ; t; d; pÞ is the coupling between a transmitter and receiver, as a function of frequency (f), time (t), distance (d) and polarization (p); Gt ðf ; t; d; pÞ is the transmitting antenna gain in the direction of the receiver; Gr ðf ; t; d; pÞ is the receiving antenna gain in the direction of the transmitter; Lp ðf ; t; d; pÞrepresents the propagation losses. The interference margin (IM) can be used to determine whether an undesired transmitting signal can cause intolerable level of interference in a receiver. This is done by comparing the power available in a receiver’s input terminal to the power required to cause interference in that particular receiver. IM is obtained by subtracting the power required to cause interference from the power available in the input terminal of a receiver.
IM ¼ ðf ; t; d; pÞ Pi ðf ; tÞ
EMF ¼
du dt
ð12Þ
The induced electromotive force (EMF), is opposed to the cause that generated it and, as such, it is equivalent to a voltage drop along the loop. It results:
u ¼ L i;
ð13Þ
with L self-inductance coefficient or inductance of the loop and therefore EMF is given by [13]:
EMF ¼
du di ¼ L : dt dt
ð14Þ
To estimate the order of magnitude of this type of disturbance in the case of a simple shielded copper conducting wire, the inductance L per units of length l of a wire with a circular section of diameter d and its resistance R, are considered
Table 7 Description of the electromagnetic sources present on board. Device
where PA ðf ; d; pÞ is the power available in the input terminals of a receiver and Pt ðf ; t Þis the transmit power [12]. All these parameters are measured in dB. If IM is positive, then there is potential for an interference problem. Negative IM indicates no or very little potential for interference. As an example, we calculated the inductance in our system taking into account the effects on a standard signal cable. Even if the cables have an adequate shielding some effects on the terminations could be found. It is recognized that the termination of the cables are critical for correct shielding. In case of a common copper wire with standard shielding, the impedances involved are typically determined from the frequency, and therefore the inductive component increases in importance as the frequency increases. For example, a magnetic field H is present around a current-driven loop and, consequently, a magnetic induction field B. The flow / concatenated with the coil is variable over time as the current which sustains it; therefore, it induces in the loop an electromotive force given by:
ð11Þ
L 4l l 0:778d nH=cm 2 ln 1 þ r þ i d 2l 4 R¼
1
l
r pd2 =4
;
ð15Þ
ð16Þ
In our study, we consider a copper wire (relative magnetic permeability mr = 1, conductivity r = 58 106 S/m) with 2 mm diameter and length 100 cm, we obtain L 1370 nH, while its resistance is about R 5.5 mX. The impedance (Z) value of the wire, for example at the frequency of 10 MHz, is [14,15]:
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 jZ j ¼ jR þ jpfLj ¼ 5:5 103 þ p 108 1370 109 ffi 4:3X
ð17Þ
This means (Table 10) that if the previous circuit has a current transient with a frequency of 10 MHz and an amplitude of 10 mA, (a square wave, with a rise time of about 35 ns), a peak of voltage (spike) of amplitude V = |ZI| 107 mV appear on the circuit powering. We show an example of spontaneous potentials (SP) data acquired during the COSMEI survey. Acquisition system was placed in two different points on board and the same GPS point; in particular, at site 1 near the laboratory and at site 2 near the stern (Fig. 7a). Acquisition cable consisted of 16 channels with graphite electrodes charged by 12 V battery. The electric marine cable was immersed in sea water up to 80 m depth in a vertical position.
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Fig. 4. Mean isotropic field E in RF 100 kHz–6.5 GHz. a) Pagliolo deck; b) Coperta deck.
Table 8 Electric field E (V/m) values measured with the 100 kHz–6.5 GHz probe. Point
Place
Percentile 50
Percentile 75
Percentile 90
Average
Standard Deviation
Standard Deviation %
9 1 2 1A 2A 3A 4A 3 13A 12A 5A 6A 7A 4 5 8A 9A 14 13 12 15A 10A 11A 6 7 8 14A 11 10 16A 17A 18A
Engine Bow Hallway Pagliolo cold room hallway hallway in front of the kitchen hallway in front of the kitchen bis Coperta hallway stern Coperta hallway bow Pagliolo hallway bow kitchen Wet laboratory Electrical laboratory Physical laboratory Physical laboratory Laundry Bautruster place Crew Mess hall Researcher Mess hall Helm (right side) Helm (left side) Engine room (left side) Deck Castello est near winch External stern Cala nostromo bow Engine room – power generator Stern Engine room Bow Engine room Meeting room Wheelhouse Stern hold Sparker hold (during operation) Near dredging winch Near stern crane
0.38 0.40 0.48 0.45 0.38 0.38 0.40 0.37 0.37 0.37 0.37 0.51 0.80 0.38 0.73 0.38 0.40 0.44 0.40 0.57 0.41 0.51 0.82 0.38 0.37 0.37 0.37 0.56 0.38 0.41 0.44 0.82
0.41 0.43 0.52 0.54 0.41 0.41 0.43 0.38 0.38 0.38 0.38 0.56 0.90 0.40 0.75 0.42 0.42 0.46 0.42 0.58 0.43 0.53 0.83 0.41 0.38 0.38 0.38 0.59 0.39 0.43 0.46 0.84
0.46 0.47 0.55 0.58 0.43 0.44 0.47 0.39 0.40 0.41 0.40 0.58 0.83 0.42 0.76 0.43 0.44 0.48 0.44 0.61 0.45 0.55 0.83 0.43 0.40 0.40 0.40 0.60 0.41 0.46 0.47 0.87
0.39 0.42 0.48 0.52 0.39 0.39 0.41 0.37 0.37 0.39 0.37 0.53 0.82 0.38 0.75 0.41 0.41 0.45 0.41 0.59 0.43 0.53 0.82 0.39 0.37 0.37 0.37 0.56 0.38 0.42 0.44 0.85
0.04 0.03 0.03 0.06 0.04 0.04 0.03 0.02 0.03 0.04 0.03 0.05 0.06 0.02 0.05 0.02 0.03 0.04 0.04 0.04 0.02 0.03 0.02 0.03 0.02 0.02 0.03 0.06 0.02 0.04 0.04 0.06
10.3 7.1 6.3 11.5 10.3 10.3 7.3 5.4 8.1 10.3 8.1 9.4 7.3 5.3 6.7 4.9 7.3 8.9 9.8 6.8 4.7 5.7 2.4 7.7 5.4 5.4 8.1 10.7 5.3 9.5 9.1 7.1
The measurements were made to the various dipoles with a frequency of 10 Hz. The Fig. 7b reports 1 min of SP recording; the black line is referred to site 1 while the red line to site 2. The presence of spikes
events in the signal recorded in site 2 it is very clear (Fig. 7b). Evidences of EMI in site 2 signal are also found in the Fourier domain (Fig. 7c). In the site 2 spectrum, a higher presence of low signal frequencies is present which shows a consistent offset (Fig. 7c).
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Table 9 Magnetic field B (mT) values measured with the 5 Hz–400 kHz probe. Point
Place
Percentile 50
Percentile 75
Percentile 90
Average
Standard Deviation
Standard Deviation %
9 1 2 1A 2A 3A 4A 3 13A 12A 5A 6A 7A 4 5 8A 9A 14 13 12 15A 10A 11A 6 7 8 14A 11 10 16A 17A 18A
Engine Bow Hallway Pagliolo Cold room hallway Hallway in front of the kitchen Hallway in front of the kitchen bis Coperta hallway stern Coperta hallway bow Pagliolo hallway bow kitchen Wet laboratory Electrical laboratory Physical laboratory Physical laboratory Laundry Bautruster place Crew Mess hall Researcher Mess hall Helm (right side) Helm (left side) Engine room (left side) Deck Castello est near winch External stern Cala nostromo bow Engine room – power generator Stern Engine room Bow Engine room Meeting room Wheelhouse Stern hold Sparker hold (during operation) Near dredging winch Near stern crane
30.74 32.16 40.35 48.86 46.54 22.16 33.20 31.71 26.78 22.67 23.11 17.46 21.38 16.25 38.17 27.73 12.12 21.38 22.16 33.25 20.93 43.01 32.26 49.25 36.55 34.90 22.89 20.44 21.41 33.18 22.23 83.96
31.45 33.00 42.12 49.70 48.25 24.66 33.76 32.95 28.11 23.37 25.08 20.98 24.74 16.76 40.15 28.43 12.85 41.66 39.45 37.12 21.68 43.86 32.68 50.19 38.44 36.08 24.06 44.96 36.29 33.84 22.88 85.94
32.08 33.68 43.24 50.25 49.71 25.17 34.32 33.66 29.21 24.08 26.08 29.50 30.19 17.23 42.03 28.97 14.06 45.36 44.76 46.29.63 22.09 44.56 33.12 51.09 42.15 47.63 26.48 49.33 40.52 34.26 23.41 88.45
30.72 31.91 41.12 48.40 45.25 22.45 33.25 32.03 27.29 22.83 20.88 18.22 21.16 16.28 39.75 26.85 12.20 26.35 27.27 37.01 21.00 43.14 32.18 49.33 37.56 36.90 21.12 28.65 34.25 33.16 21.60 85.21
1.03 1.52 0.85 1.69 1.34 1.86 0.87 1.34 2.83 0.85 1.24 1.31 1.44 0.84 1.19 1.88 1.24 1.81 2.06 1.12 0.83 1.09 0.80 1.30 2.01 1.44 2.07 2.35 2.76 0.85 1.63 2.03
3.4 4.8 2.1 3.5 3.0 8.3 2.6 4.2 10.4 3.7 5.9 7.2 6.8 5.2 3.0 7.0 10.2 6.9 3.0 3.0 4.0 2.5 2.5 2.6 5.3 3.9 9.8 8.2 8.0 2.6 7.5 2.4
Fig. 5. Mean isotropic field B 5 Hz–400 kHz. a) Pagliolo deck; b) Coperta deck.
Table 11 instead shows the values of the statistical parameters determined for the two signals. It is clear that site 2 with respect to site 1 presents: an average value higher than 30% (from 13.41 to
19.06) and a P-P value increased up to 200% (from 124 to 58). Also the three percentiles values confirm in site 2 a general increment trend of the EMI.
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Fig. 6. Pearson index correlation calculated between the isotropic field E and the isotropic field B. a) Pagliolo deck; b) Coperta deck.
Table 10 Some examples of Z and V calculated for different d, F and current of 25 mA.
lr
r (S/m)
d (mm)
l (cm)
F (Hz)
L (nH)
R (mX)
Z (X)
V (mV)
1 1 1 1 1 1
58106 58106 58106 58106 58106 58106
1.0 1.5 2.0 1.0 1.5 2.0
100 100 100 100 100 100
106 106 106 107 107 107
1509 1427 1370 1509 1427 1370
21.2 9.8 5.5 22 9.7 5.5
4.7 4.5 4.3 4.7 4.5 4.3
118 112 107 1184 1120 1075
6. Conclusion The present study has shown that in the case of data acquisition with conventional digital systems (with metallic conductors), the sampled signals may be subject to electromagnetic disturbances of various nature. In fact, it is well known that an electric field is generated by both stationary and moving charges and that at the same time a magnetic field can be produced both by magnetic bodies and by charges in motion; moreover, fluctuating electric/magnetic fields can produce electromagnetic waves. We analyzed the measurements of an electric field E (100 k Hz– 6.5 MHz) with potentially disturbing frequencies and the magnetic flux density B (5 Hz–400 kHz) also including the low frequency connected to power signal (50 Hz). The results provided interesting indications showing values of the field E up to 0.82 V/m and of the field B with values up to 85 lT. All the measurements were performed taking into account the statistical significance by comparing the average values obtained both with the various percentiles (50, 75, 90) and with the standard deviations. Observing the anomalies maps (Figs. 4 and 5), it is possible to identify areas for which it would be advisable to avoid the passage
of signal lines and housing of data acquisition devices. Assuming the field E and B values obtained in this study, considering a standard conductor with diameter 1–2 mm and frequencies range of 106–107 Hz, we observed an inductance L up to 47 X on the cable corresponding to an EMF of 1184 mV. Observing the experimental SP data acquired in two onboard site (Fig. 7a–c) and the relative statistical parameters reported in Table 11, it is shows the EMI increment in site 2 where the Pearson index correlation calculated between the isotropic field E and the isotropic field B is higher than in site 1. Therefore, we believe that in an oceanographic survey planning, because the onboard acquisition systems are potentially affect by electromagnetic fields noise, a preliminary electromagnetic screening is needed to optimize the measurement setup where the E and B fields are expected to exhibit relatively low values and results in low distortions of the intended measurements.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Fig. 7. (a) SP sites measurement on board; (b) SP time series referred to site 1 (black line) and site 2 (red line); (c) Fourier spectra at the site 1 (black line) and site 2 (red line). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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V. Di Fiore et al. / Measurement 147 (2019) 106889 Table 11 Statistical parameters referred to SP time series acquired in the site 1 and 2. SP site
Average(mV)
SD(mV)
P-P max(mV)
P50(mV)
P75(mV)
P95(mV)
1 2
13.41 19.06
7.07 11.04
58 124
12 17
18 26
24 29
Acknowledgments The authors would like to thank the DSSTTA and in particular the Director Dr. Fabio Trincardi for supporting the survey planning. We would also like to thank the Minerva Uno crew and Sopromar Spa, the shipping company, for the availability and patience shown during the data acquisition phases and in particular during difficulties moments. Prof. Michele Meo is acknowledged for his comments that helped us in improving the manuscript. The research activities were carried out within the RITMARE Flagship that is one of the National Research Programmes funded by the Italian Ministry of University and Research - Sub Project ‘‘Forecasting and control of on-board electromagnetic emissions” – SP1_WP3_AZ6_UO01. References [1] H.M. Judson, The shipboard operating environment – a design challenge, Naval Eng. J. 94 (5) (2009) 41–45. [2] P. Xu, S. Hao, Y. Geng, T. Jiang, Research on EMC evaluation for communication systems on board, IEEE Xplore (2016), https://doi.org/10.1109/ ROPACES.2016.7465353. [3] S.T. Li, J.C. Logan, J.W. Rockway, Ship EM design technology, Naval Eng. J. (1988). [4] B.J.A.M. Van Leersum, D.W.P. Thomas, J.G. Bergsma, J. van der Graa, F.B.J. Leferink, Cable crosstalk and separation rules in complex installations, in:
[5]
[6] [7]
[8]
[9]
[10] [11] [12]
[13] [14] [15]
Electromagnetic Compatibility (EMC EUROPE), 2012 International Symposium on, Sept 2012, 2012, pp. 1–6. V. Di Fiore, F. Lirer, F. Budillon, N. Pelosi, M. Punzo, G. Zeni, M. Iavarone, P. Scotto di Vettimo, C. Barbalucca, Campagna Oceanografica Sismica, Magnetica ed Elettrica - Ischia (COSMEI) Technical Report, Solar-CNR, 2018, http:// eprints.bice.rm.cnr.it/id/eprint/18136. R.K. Wangsness, Electromagnetic Fields, 2nd ed., Wiley, 1986, ISBN 0-47181186-6. F. Zare, Electromagnetic Interference Issues in Power Electronics and Power Systems, Bentham Books, 2011, p. 117, ISBN: 978-1-60805-388-9, DOI: 10.2174/97816080524001110101. Norma CEI 211-6 (2001-01) Guida per la misura e per la valutazione dei campi elettrici e magnetici nell’intervallo di frequenza 0 Hz 10 kHz, con riferimento all’esposizione umana, Norma CEI 211-7 (2001-01) ‘‘Guida per la misura e per la valutazione dei campi elettrici e magnetici nell’intervallo di frequenza 10 kHz–300 GHz, con riferimento all’esposizione umana”. W.G. Duff, Designing Electronic Systems for EMC, SciTech Publishing Inc, Raleigh NC, 2011. H.W. Ott, Noise Reduction Techniques in Electronic Systems, 2nd ed., Wiley & Sons, New York, 1988. A. Gharib, H.D. Griffiths, D.J. Andrews, Prediction of topside electromagnetic compatibility in concept-phase ship design, IEEE Trans. Electromagn. Compat. 59 (1) (2017) 67–76, https://doi.org/10.1109/TEMC.2016.2606414. M. Bueno, A.K.T. Assis, Equivalence between the Formulas for Inductance Calculation, NRC, Canada, 1997, pp. 357–362. E. Bava, G. Galzerano, M. Norgia, R. Ottoboni, C. Svelto, Misure elettroniche di laboratorio, Pitagora, 2005, Anno edizione. E. Bava, R. Ottoboni, C. Svelto, Fondamenti della misurazione, Esculapio, 2005, Anno edizione.
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Electromagnetic field evaluation and EMI on board during a marine geophysical data acquisition (COSMEI) Vincenzo Di Fiore a,⇑, Michele Punzo a, Nicola Pelosi a, Paolo Scotto di Vettimo a, Michele Iavarone a, Francesca Budillon a, Giovanni Zeni b, Fabrizio Lirer a a b
ISMAR – CNR Institute of Marine Sciences, UOS, Naples, Italy IREA – CNR Institute for Electromagnetic Sensing of the Environment, Naples, Italy
a r t i c l e
i n f o
Article history: Received 26 November 2018 Received in revised form 1 July 2019 Accepted 30 July 2019 Available online 2 August 2019 Keywords: EMI EMC Geophysical oceanographic survey Inductance
a b s t r a c t When performing oceanography measurements, it is critical to assess the presence of the noise sources that could affect the measured data and lead to wrong interpretation of the results. This paper report the result of an oceanography survey conducted by ISMAR-CNR, Naples, in the north-eastern marine sector of the Ischia Island and assess the influence of EMI on the measured results. The analyzed measurements of the Electric and Magnetic fields showed values of the E up to 0.82 V/m and of B up to 85 lT. By assuming a standard conductor, an inductance L up to 47 X on the cable corresponding to an induced electromotive force of 1184 mV was calculated. Also the experimental data show the EMI increase in site where the Pearson index correlation is higher. The results demonstrate that in an oceanographic survey planning, a preliminary electromagnetic screening is advisable to optimize the measurement setup. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction With the growing density of electrical and electronic systems onboard contemporary naval platforms, electromagnetic interference and compatibility aspects have acquired great significance. A large number of equipment, emitting signals over a wide range of the electromagnetic spectrum, have to co-exist with sensitive surveillance systems with similar spectrum onboard a warship. Further, in the process of continuous upgrading and modernization of a warship required to keep abreast with emerging technologies, state of the art equipment is installed from time to time to augment/retrofit existing systems in the already dense electromagnetic (EM) environment onboard. Some authors studied Electromagnetic Compatibility (EMC) effect during the ship navigation. Operational problems arising from ship-board Electromagnetic Interference (EMI) generated by installed electrical and electronic system have been of increasing concern to the Navy for many years. By 1972, such problems had grown to serious proportions, as reported from fleet Commanders revealing that shipboard EMI were high to degrade vital functions and system performance [1]. In [2] they showed that the evaluation and optimization model can achieve the overall quantitative ⇑ Corresponding author. E-mail address: [email protected] (V. Di Fiore). https://doi.org/10.1016/j.measurement.2019.106889 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved.
control of electromagnetic compatibility in telecommunication system. As an example, when the interference between two topside antennas is predicted to be above a selected tolerable level, the antennas can be relocated on the ship, consistent with other ship design constraints, and the simulation is then rerun. This process is repeated until a configuration is achieved where the severity of the interference is reduced to a level that is acceptable to ship designers [3]. In [4] a numerical analysis including measurements of the magnetic decoupling between these loops has shown the importance of a low bonding resistance. Because the signal cables can be affected by EMI effect, it is important to study the electromagnetic field which can induce electrical noise. In our case, simultaneous acquisition of geophysical data in addition to sources of electromagnetic fields can generate noise in the measured signals. These sources can produce fields, variable with time, in the electromagnetic spectrum that extends from static fields to infrared radiation. Compatibility and interferences electromagnetic problems can affect the electrical-electronic equipment on board, the engine equipment, as well as the entire ship system. The increasingly widespread use of electronic components and instrumentation and the use of signal equipment coupled with power systems has given rise in recent years to several problems
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concerning many disciplines in the fields of industrial, electrical and electronic engineering considered first disciplines in its own right. Each electric-electronic device must be considered capable of emitting (in a more or less relevant way) electromagnetic radiations that can invest other equipment and in the same way it can be subjected to the radiations present in the environment in which it is installed. The EMC refers to the aptitude of an apparatus or a system to function correctly, in a given environment, without being subject to anomalies or failures caused by electromagnetic radiation present in the environment considered and without producing, in turn, harmful radiation for other equipment or systems present in the same environment. An electromagnetic compatibility problem is a problem of environmental compatibility of an apparatus or of a system with respect to the level of disturbances or with respect to the degree of sensitivity to disturbances of other apparatuses or systems present in the same environment. Therefore, ECM can be seen as a particular case of environmental pollution, where the ‘‘polluting agents” are electromagnetic waves. EMI, on the other hand, can be irradiated by the presence of an ‘‘interference source”, i.e. a device capable of intentionally or not emitting an electromagnetic wave which can be received by electronic systems that are not shielded and therefore insensitive to such radiation. In conduction EMI, there is a physical connection, of parasite type, between devices that should be electrically isolated (i.e. a path of parasitic conductive type is created between two devices); in EMI by induction (diaphony), the problems of EMI are linked to inductive or capacitive coupling between two conductors, in the absence of a direct physical connection. At the lowest frequency, when the fields are characterized by slow variations with time, or, more generally, when the exposure to electromagnetic fields occurs at distances from the short source with respect to the wavelength, the Electric fields (E) and the Magnetic fields (H) are generally considered separately. At higher frequencies or, more generally, at high distances from the source with respect to the wavelength, the electric fields and magnetic fields are closely related to each other: from the measurement of one of them it is generally possible to calculated the other one. At the basis there is the consideration of the physical phenomenon related to the production of a magnetic field by an electric current and, as reported in Table 1 The electromagnetic field sources can be divided into intentional and unintentional radiating sources. The intentional radiators are those that emit electromagnetic waves and have characteristics known in terms of amplitude, polarization, frequency stability and emission of spurious harmonics. The waveform can assume different trends depending on the transmission scheme adopted. Simple cases consist of amplitude (AM), frequency (FM) or phase (PM) signals modulation, and coding techniques for subcarriers as in the OFDM communications. Radars, on the other hand, typically use short microwave pulse packets of duration in the microsecond range. Unintentional radiators are devices that emit electromagnetic waves as a secondary effect (loss of radiation) compared to the purpose for which they are designed as induction and/or radio frequency heating systems, or even applications for industrial processes, such as welding or fusions arc or microwave. The harmonized technical standards for the introduction of products on the market impose severe limitations on unintentional emissions. However, there are cases with non-negligible local effects observed above all in the industrial field due to the nature of a processing or plant with high power. The Ischia Electric Magnetic Seismic Oceanographic Campaign (COSMEI) was born following the seismic event of Mw 3.9 on date 21 August 2017 and time 20:57:51 (Timezone Italy) in region 1 km
Table 1 Analogy between electric field and magnetic field.
Symbol Mathematical operator Force Expression of Field
Driving Force Produces Limited by Favored by
Lorentz Force Law AmpereMaxwell Law Where: ! E ! B q !
v
! J K ! ur Ka Km
l0 e0
! r
Electric field
Magnetic induction field
! E q
! B ! qv K
! ! F ¼ qE ! ! E ¼ K a rq2 ur
! ! ! F ¼ qv K B ! ! ! l q ! ! B ¼ K m rq2 v K ur ¼ 4p0r2 v Kur
Electric circuit
Magnetic circuit
Electromotive Force – EMF Current (I) [Ampere, A] Resistance, q, [ohm, X] Conductivity, r, [Siemens per meter (Sm1)] ! ! ! ! F ¼ q E þ qv xB
Magnetomotive Force – MMF
!
!
r B ¼ l0
Flux (/) [Weber, Wb] Reluctance, R [Henry1, H] Permeance, P, [Henry, H]
! ! J þ e0 ##tB
Electric field vector [Volt per metre, V/m] Induced Magnetic flux density vector [Tesla, T] Electric charge [Coulomb, C] Vector representative of the speed of the moving electric charge Electric current density [Ampere per square metre, A/m2] Vectorial product between vector Position vector Electric constant Magnetic constant Magnetic permeability of free space Electric permeability of free space Curl Operator
SW Casamicciola Terme [5]. The aim of the oceanographic survey was to acquire geophysical data as mono/multichannel seismic data, gradiometer magnetic data and resistivity data in the north-eastern marine sector of the Ischia Island for the reconstruction of tectonic and volcanic structures potentially originating seismic events. During this survey, a study of radio frequency (RF) and low frequency (LF) magnetic fields was also performed. Acquisition data was conducted by oceanographic ship ‘Minerva Uno’ of the National Research Council (Fig. 1).
Fig. 1. Oceanographic Ship ‘‘Minerva Uno”.
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The main aim of the present paper is the evaluation of electromagnetic emission of the devices present on board in terms of electric field E with frequency band 100 kHz–6.5 GHz and the magnetic fluxes density B in the frequency range frequency between 5 Hz and 400 kHz and therefore evaluate the potential interference with the geophysical data signal during the measurement survey. The produced interferences result in disturbances conducted on the cables that are current on power lines (but also in the output and control lines) of the devices. According to the EN55014 standard, the harmonic components from 150 kHz to 30 MHz are relevant, and in these frequency range the common mode disturbances and differential mode disturbances should be classified, and therefore, different filtering techniques are needed. Common mode disturbances (MC, also called: asymmetric mode) propagate with the same phase along two or more conductors to ground. The line disturbance can be imagined as an impulse that equally invests the two conductors by generating a current to ground (as can be caused for example by lightning). Differential mode disturbances (MD, also called: symmetric mode or normal mode) propagate with opposite phases along the phase and neutral conductors so as to close without affecting the ground conductor. Line disturbances can be generated for example by inductive loads that are connected and disconnected, the over voltages that are generated between the two conductors give rise to differential mode disturbances. Generally, differential mode disturbances involve the lower part of the spectrum.
Therefore, the electromagnetic field resulting in any observation point is the vectorial sum of many contributions, coming from multiple sources, operating at different frequencies; in the Fourier domain we have [7]:
2. Electric (E) and magnetic (B) field measurement
n X ! ! E tot ðx; t Þ ¼ E ð xi ; t Þ
n X ! ! B tot ðx; t Þ ¼ B ð xi ; t Þ
It is known that B and E fields are connected by Maxwell equation as:
!! @B r ;t !! r E r ;t ¼ @t
!
! qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 2 E ðx; y; z; t Þ ¼ Ex ðtÞ þ Ey ðtÞ þ Ez ðt Þ;
ð1Þ
and
! qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 2 B ðx; y; z; t Þ ¼ Bx ðt Þ þ By ðtÞ þ Bz ðt Þ;
ð2Þ
ð5Þ
! where r is curl operator. The curl is a measure of the rotation of a vector field. Eq. (5) is known as Faraday’s Law of induction. This law establishes that an electric field can be generated from a time variant of the magnetic field induction. In matricial form on the window time WT:
0 i ! @ B ðx; y; z; tÞ B @ ¼ det@ @x @t Ex
The measurements of the electromagnetic fields are normally performed in the frequency domain. They can be classified into broadband and narrowband. The broadband frequencies are performed with the use of instruments which, within a certain frequency interval, have a sensitivity almost independent of the frequency itself and provide the global value of the electric or magnetic field in the considered interval; the narrowband measurements, also called selective, are performed with the use of instruments that can be tuned to a selected frequency and which provide the intensity of the field corresponding to the default frequencies. The components of the electromagnetic field can be measured with the use of antennas as small dipoles in the case of an electric field or, equivalently, with loop sensors in the case of a magnetic field. The isotropic probes for broadband measurements contain three sensible elements (dipoles or loops) arranged in the three orthogonal directions. These probes measure the result of field strength (electric or magnetic) expressed as a square root of the sum of the squares of the field strengths along the three directions of the space (x, y, z) without considering the single phases of the probes themselves. Therefore, the total electric (E) and magnetic (B) fields are given by the following formulas [6]:
ð4Þ
i¼1
The measurement of the intensity of electromagnetic fields can be carried out indirectly using environmental measurements of the following quantities: – Electric Field E (V/m); – Magnetic induction B (lT).
ð3Þ
i¼1
j
k
@ @y
@ @z
Ey
Ez
1 C A
ð6Þ 8t2WT
! @ B ðx; y; z; t Þ @ @ @ ¼ Ez ðt Þbi þ Ey ðtÞ b k þ E ðt Þbj @t @y @x @z x @ @ @ Ex ðt Þ b k þ Ey ðt Þbi þ E ðt Þbj @y @z @x z ! @ B ðx; y; z; t Þ @Ez ðt Þ @Ey ðt Þ b @Ex ðtÞ @Ez ðtÞ b ¼ iþ j @t @ ðyÞ @ ðzÞ @ ðzÞ @ ðxÞ @Ey ðt Þ @Ex ðt Þ b k; þ @ ð xÞ @ ðyÞ
ð7Þ
ð8Þ
Eq. (8) implies that when E is ‘‘conservative” or irrotational, B is constant in (x, y, z, t) domains. 3. Measurement points The ship size and the used materials can influence the electromagnetic propagation; the choice and the sizing of the onboard equipment is depended on the type of ship and its required missions and safety aspects. Considering the ship characteristic, equipment onboard and the power network produced, we used two system sampler-probes and in particular: E field sampler with isotropic/multicomponent probe operating in an overall frequency range between 100 kHz and 6.5 GHz and compatible with electric field strengths up to 350 V/m. B field sampler with isotropic/multicomponent probe operating in an overall frequency range between 5 Hz and 400 kHz and compatible with magnetic field strength up to 1012 lT. Both measurement systems have been calibrated by a certified laboratory. Dataset was acquired by personal laptops connected to the previous instrumentation and exploiting specifically dedicated software. Fig. 2 depicts a block diagram of the measurement set-up. For a complete analysis also the temperature and humidity values were recorded.
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Fig. 2. The measure technique uses both hardware, for the signal acquisition (triazial probe, filters and amplifiers), and software for signal recording and analysis.
Onboard tests were conducted on 66 points differently distributed (Fig. 3a–d) and the measurement taken for 5 days. The measurements were carried out using a tripod stands of dielectric material at 1.6 m from floor. During the measurement, the operators remained at a distance from the probe in order not to influence the measurement of the field and furthermore all the personal communication devices were placed in airplane mode. As far as possible, we tried to maintain the verticality of the probe and in particular the measurements were made by controlling the pitch and roll of the ship (1–5 degrees max). Tables 2–4 show the most important technical characteristics of the instruments used; Table 5 shows instead the data acquisition parameters. Table 6 shows the main technical characteristics of the N/O Minerva Uno. About the electric/magnetic sources present on the ship, we identified the potential source of high frequency E field (Table 7). For electric and diesel engines, a measurement of field B was also carried out in the range that includes 50 Hz (engine room, etc.).
4. Results During the oceanographic survey, different geophysical data were acquired. Specifically: gradiometric/magnetometric data, geoelectrical data, high-frequency single-channel seismic data (CHIRP), multi-channel seismic data and multi-beam data. The critical point is that the data are acquired simultaneously implying a strong vulnerability to the attack of electromagnetic-type external noise. In particular, the geophysics measurements are translated into conversion parameters as micro-tension and field E and B expressed in mV and mT respectively. Therefore, given the magnitude of the value of the data, the measure is sensitive to EMI due inevitably to the instrumentation used for navigation but also for communication and other showing the shielding of the electronic system was not correctly designed. Thirty three measurement stations relative to two bridges (Pagliolo deck and Coperta deck) were selected and the data were collected in areas where research activities were performed. The measurements were performed in accordance with the standard Norma CEI 211-6 [8] and Norma CEI 211-7 [9]. 4.1. Field E (100 k Hz–6.5 MHz) N. 14 measurements were performed at Pagliolo deck (Fig. 4a). For each measure the 50, 75 and 90 percentiles were determined; the average of the values was calculated taking into account the restrictions of the standard deviation set at a maximum of 11% from the average value.
Table 8 shows all the values where it is possible to highlight the significance of the data and in particular the value of the average with the different percentiles. Fig. 4a shows the results of the measurements for the Pagliolo deck (measurements 1–14); the maximum values are evident near point 12, point 5 and point 11. The maximum values in points 5 and 11 are due to the presence of antennas placed at bow and stern respectively, while for point 12 the maximum value is connected to the presence of the acquisition systems of the physical laboratory present at the upper deck (Coperta deck). Fig. 4b shows the contouring of the electric field E for the Coperta deck (measurements 1a-19a). The situation is almost similar to the Pagliolo deck with the difference that in the central area of the ship for measures 6a and 7a there is an extension of the maximum of the field E. 4.2. Magnetic induction field B (5 Hz–400 kHz) The measurement of the field B was carried out in the same location and using the same measurement points of the field E (Table 9). For the Pagliolo deck (Fig. 5a), the maximum B field values, between 50 and 90 lT, are located at the bow (measures 2, 5) and in the left side of the vessel (measures 6, 7, 8, 12). Moreover, on the right ship side, from the bow up to about half of its length, an anomaly of the B field can be observed. The anomalies in the central area on the left side are probably connected with the presence of the engine room, while on the bow area and right side are due to the presence of current generators. For the Coperta deck (Fig. 5b) we find a maximum of 80 mT in the stern area (measure 10a) and in the bow area (measure 11a) and a maximum in the front central area of the ship (measurements 1a and 2a). These maximums are due to the presence of a winch in the stern area, and current generators in other areas. Fig. 6a and b show the Pearson correlation between the field E and the B for each individual deck of the ship. The Pearson product-moment correlation coefficient is a statistical measurement of the correlation (linear association) between two sets of values and is given by the formula:
P ðx xÞð y yÞ ; r ¼ qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi P P ðx xÞ2 ð y yÞ2
ð9Þ
where x and y are sample means of two arrays of values. The areas where the disturbance effect is emphasized are evident; moreover, the zones where the effects of E and B show peak values are clear.
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Fig. 3. a) Instrumentation used for the measurements. NHT310 (sampler), 10B and 01E probes. b) Measurement station indoor the ship. c) Measurement station outside the ship by 01 E probe. d) Measurement station indoor the ship by 10B probe.
Table 2 Technical specification MICRORAD NHT310.
Table 3 Technical specification MICRORAD 01E probe.
Electromagnetic field device – microrad NHT310
Microrad 01E probe
Fields Frequency Values Dynamic range
Fields Frequency range Measurement range Dynamic range Sensor type Directivity
E, B, H Hz DC – 40 GHz mW/cm2, W/m2, V/m, A/m, Tesla dB 144
V/m Hz V/m dB
Electric (E) 100 kHz–6.5 GHz 0.20–350 66 Diode dipoles Isotropic
5. EMI evaluation EMC is typically achieved by the decoupling of Common Mode (CM) current loops at the inside and outside of current boundaries. This can even be made by cable terminations instead of shielding
walls, to create a barrier for these currents. It is known that EMI coupling is the transfer of EM energy from the terminals of a transmitting system into the terminals of a receiving system. Generally, EMI coupling in the far-field region of an antenna depends on the
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Table 4 Technical specification MICRORAD 10B probe. Microrad 10B probe Fields Frequency range Measurement range Dynamic range Sensor type Directivity
lT
Magnetic (B) 5 Hz–400 kHz 0.1–1012 80 Coils Isotropic
Hz lT dB
Table 5 Acquisition parameters. Data acquisition parameters Parameters Acquisition Time Sample Time Viewable quantity
E, B, Temperature, Humidity min 30 s 5 Instantaneous ACT, Maximum and Average
Table 6 N/O ‘‘Minerva Uno” main technical features (from: http://www.sopromar.it/it/minervauno.htm). Parameters
Quantity
Length overall Width overall Full load draft Suez gross (net) Gross tonnage Main Engines Max (average) speed Class Category
46.6 m 9.0 m 4.60 m 700 t 615 TS Maximum power 2 746 kW at 1800 RPM 12.5 (10.8) kN Special Service Regional
Frequency range
VHF MF HF INMANSAT RADAR GPS NAVTEX
156.05 MHz 1.605 MHz 4 MHz 1626.5 MHz 8000 MHz 1575.42 MHz 0.518 MHz
162.5 MHz 3.8 MHz 27.5 MHz 1660.5 MHz 12000 MHz 1227.6 MHz 0.490 MHz
gain of the transmitting antenna, gain of the receiving antenna and free space propagation losses, and it is given by [10,11]:
Cðf ; t; d; pÞ ¼ Gt ðf ; t; d; pÞ þ Gr ðf ; t; d; pÞ Lp ðf ; t; d; pÞ
ð10Þ
where Cðf ; t; d; pÞ is the coupling between a transmitter and receiver, as a function of frequency (f), time (t), distance (d) and polarization (p); Gt ðf ; t; d; pÞ is the transmitting antenna gain in the direction of the receiver; Gr ðf ; t; d; pÞ is the receiving antenna gain in the direction of the transmitter; Lp ðf ; t; d; pÞrepresents the propagation losses. The interference margin (IM) can be used to determine whether an undesired transmitting signal can cause intolerable level of interference in a receiver. This is done by comparing the power available in a receiver’s input terminal to the power required to cause interference in that particular receiver. IM is obtained by subtracting the power required to cause interference from the power available in the input terminal of a receiver.
IM ¼ ðf ; t; d; pÞ Pi ðf ; tÞ
EMF ¼
du dt
ð12Þ
The induced electromotive force (EMF), is opposed to the cause that generated it and, as such, it is equivalent to a voltage drop along the loop. It results:
u ¼ L i;
ð13Þ
with L self-inductance coefficient or inductance of the loop and therefore EMF is given by [13]:
EMF ¼
du di ¼ L : dt dt
ð14Þ
To estimate the order of magnitude of this type of disturbance in the case of a simple shielded copper conducting wire, the inductance L per units of length l of a wire with a circular section of diameter d and its resistance R, are considered
Table 7 Description of the electromagnetic sources present on board. Device
where PA ðf ; d; pÞ is the power available in the input terminals of a receiver and Pt ðf ; t Þis the transmit power [12]. All these parameters are measured in dB. If IM is positive, then there is potential for an interference problem. Negative IM indicates no or very little potential for interference. As an example, we calculated the inductance in our system taking into account the effects on a standard signal cable. Even if the cables have an adequate shielding some effects on the terminations could be found. It is recognized that the termination of the cables are critical for correct shielding. In case of a common copper wire with standard shielding, the impedances involved are typically determined from the frequency, and therefore the inductive component increases in importance as the frequency increases. For example, a magnetic field H is present around a current-driven loop and, consequently, a magnetic induction field B. The flow / concatenated with the coil is variable over time as the current which sustains it; therefore, it induces in the loop an electromotive force given by:
ð11Þ
L 4l l 0:778d nH=cm 2 ln 1 þ r þ i d 2l 4 R¼
1
l
r pd2 =4
;
ð15Þ
ð16Þ
In our study, we consider a copper wire (relative magnetic permeability mr = 1, conductivity r = 58 106 S/m) with 2 mm diameter and length 100 cm, we obtain L 1370 nH, while its resistance is about R 5.5 mX. The impedance (Z) value of the wire, for example at the frequency of 10 MHz, is [14,15]:
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 jZ j ¼ jR þ jpfLj ¼ 5:5 103 þ p 108 1370 109 ffi 4:3X
ð17Þ
This means (Table 10) that if the previous circuit has a current transient with a frequency of 10 MHz and an amplitude of 10 mA, (a square wave, with a rise time of about 35 ns), a peak of voltage (spike) of amplitude V = |ZI| 107 mV appear on the circuit powering. We show an example of spontaneous potentials (SP) data acquired during the COSMEI survey. Acquisition system was placed in two different points on board and the same GPS point; in particular, at site 1 near the laboratory and at site 2 near the stern (Fig. 7a). Acquisition cable consisted of 16 channels with graphite electrodes charged by 12 V battery. The electric marine cable was immersed in sea water up to 80 m depth in a vertical position.
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V. Di Fiore et al. / Measurement 147 (2019) 106889
Fig. 4. Mean isotropic field E in RF 100 kHz–6.5 GHz. a) Pagliolo deck; b) Coperta deck.
Table 8 Electric field E (V/m) values measured with the 100 kHz–6.5 GHz probe. Point
Place
Percentile 50
Percentile 75
Percentile 90
Average
Standard Deviation
Standard Deviation %
9 1 2 1A 2A 3A 4A 3 13A 12A 5A 6A 7A 4 5 8A 9A 14 13 12 15A 10A 11A 6 7 8 14A 11 10 16A 17A 18A
Engine Bow Hallway Pagliolo cold room hallway hallway in front of the kitchen hallway in front of the kitchen bis Coperta hallway stern Coperta hallway bow Pagliolo hallway bow kitchen Wet laboratory Electrical laboratory Physical laboratory Physical laboratory Laundry Bautruster place Crew Mess hall Researcher Mess hall Helm (right side) Helm (left side) Engine room (left side) Deck Castello est near winch External stern Cala nostromo bow Engine room – power generator Stern Engine room Bow Engine room Meeting room Wheelhouse Stern hold Sparker hold (during operation) Near dredging winch Near stern crane
0.38 0.40 0.48 0.45 0.38 0.38 0.40 0.37 0.37 0.37 0.37 0.51 0.80 0.38 0.73 0.38 0.40 0.44 0.40 0.57 0.41 0.51 0.82 0.38 0.37 0.37 0.37 0.56 0.38 0.41 0.44 0.82
0.41 0.43 0.52 0.54 0.41 0.41 0.43 0.38 0.38 0.38 0.38 0.56 0.90 0.40 0.75 0.42 0.42 0.46 0.42 0.58 0.43 0.53 0.83 0.41 0.38 0.38 0.38 0.59 0.39 0.43 0.46 0.84
0.46 0.47 0.55 0.58 0.43 0.44 0.47 0.39 0.40 0.41 0.40 0.58 0.83 0.42 0.76 0.43 0.44 0.48 0.44 0.61 0.45 0.55 0.83 0.43 0.40 0.40 0.40 0.60 0.41 0.46 0.47 0.87
0.39 0.42 0.48 0.52 0.39 0.39 0.41 0.37 0.37 0.39 0.37 0.53 0.82 0.38 0.75 0.41 0.41 0.45 0.41 0.59 0.43 0.53 0.82 0.39 0.37 0.37 0.37 0.56 0.38 0.42 0.44 0.85
0.04 0.03 0.03 0.06 0.04 0.04 0.03 0.02 0.03 0.04 0.03 0.05 0.06 0.02 0.05 0.02 0.03 0.04 0.04 0.04 0.02 0.03 0.02 0.03 0.02 0.02 0.03 0.06 0.02 0.04 0.04 0.06
10.3 7.1 6.3 11.5 10.3 10.3 7.3 5.4 8.1 10.3 8.1 9.4 7.3 5.3 6.7 4.9 7.3 8.9 9.8 6.8 4.7 5.7 2.4 7.7 5.4 5.4 8.1 10.7 5.3 9.5 9.1 7.1
The measurements were made to the various dipoles with a frequency of 10 Hz. The Fig. 7b reports 1 min of SP recording; the black line is referred to site 1 while the red line to site 2. The presence of spikes
events in the signal recorded in site 2 it is very clear (Fig. 7b). Evidences of EMI in site 2 signal are also found in the Fourier domain (Fig. 7c). In the site 2 spectrum, a higher presence of low signal frequencies is present which shows a consistent offset (Fig. 7c).
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V. Di Fiore et al. / Measurement 147 (2019) 106889
Table 9 Magnetic field B (mT) values measured with the 5 Hz–400 kHz probe. Point
Place
Percentile 50
Percentile 75
Percentile 90
Average
Standard Deviation
Standard Deviation %
9 1 2 1A 2A 3A 4A 3 13A 12A 5A 6A 7A 4 5 8A 9A 14 13 12 15A 10A 11A 6 7 8 14A 11 10 16A 17A 18A
Engine Bow Hallway Pagliolo Cold room hallway Hallway in front of the kitchen Hallway in front of the kitchen bis Coperta hallway stern Coperta hallway bow Pagliolo hallway bow kitchen Wet laboratory Electrical laboratory Physical laboratory Physical laboratory Laundry Bautruster place Crew Mess hall Researcher Mess hall Helm (right side) Helm (left side) Engine room (left side) Deck Castello est near winch External stern Cala nostromo bow Engine room – power generator Stern Engine room Bow Engine room Meeting room Wheelhouse Stern hold Sparker hold (during operation) Near dredging winch Near stern crane
30.74 32.16 40.35 48.86 46.54 22.16 33.20 31.71 26.78 22.67 23.11 17.46 21.38 16.25 38.17 27.73 12.12 21.38 22.16 33.25 20.93 43.01 32.26 49.25 36.55 34.90 22.89 20.44 21.41 33.18 22.23 83.96
31.45 33.00 42.12 49.70 48.25 24.66 33.76 32.95 28.11 23.37 25.08 20.98 24.74 16.76 40.15 28.43 12.85 41.66 39.45 37.12 21.68 43.86 32.68 50.19 38.44 36.08 24.06 44.96 36.29 33.84 22.88 85.94
32.08 33.68 43.24 50.25 49.71 25.17 34.32 33.66 29.21 24.08 26.08 29.50 30.19 17.23 42.03 28.97 14.06 45.36 44.76 46.29.63 22.09 44.56 33.12 51.09 42.15 47.63 26.48 49.33 40.52 34.26 23.41 88.45
30.72 31.91 41.12 48.40 45.25 22.45 33.25 32.03 27.29 22.83 20.88 18.22 21.16 16.28 39.75 26.85 12.20 26.35 27.27 37.01 21.00 43.14 32.18 49.33 37.56 36.90 21.12 28.65 34.25 33.16 21.60 85.21
1.03 1.52 0.85 1.69 1.34 1.86 0.87 1.34 2.83 0.85 1.24 1.31 1.44 0.84 1.19 1.88 1.24 1.81 2.06 1.12 0.83 1.09 0.80 1.30 2.01 1.44 2.07 2.35 2.76 0.85 1.63 2.03
3.4 4.8 2.1 3.5 3.0 8.3 2.6 4.2 10.4 3.7 5.9 7.2 6.8 5.2 3.0 7.0 10.2 6.9 3.0 3.0 4.0 2.5 2.5 2.6 5.3 3.9 9.8 8.2 8.0 2.6 7.5 2.4
Fig. 5. Mean isotropic field B 5 Hz–400 kHz. a) Pagliolo deck; b) Coperta deck.
Table 11 instead shows the values of the statistical parameters determined for the two signals. It is clear that site 2 with respect to site 1 presents: an average value higher than 30% (from 13.41 to
19.06) and a P-P value increased up to 200% (from 124 to 58). Also the three percentiles values confirm in site 2 a general increment trend of the EMI.
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V. Di Fiore et al. / Measurement 147 (2019) 106889
Fig. 6. Pearson index correlation calculated between the isotropic field E and the isotropic field B. a) Pagliolo deck; b) Coperta deck.
Table 10 Some examples of Z and V calculated for different d, F and current of 25 mA.
lr
r (S/m)
d (mm)
l (cm)
F (Hz)
L (nH)
R (mX)
Z (X)
V (mV)
1 1 1 1 1 1
58106 58106 58106 58106 58106 58106
1.0 1.5 2.0 1.0 1.5 2.0
100 100 100 100 100 100
106 106 106 107 107 107
1509 1427 1370 1509 1427 1370
21.2 9.8 5.5 22 9.7 5.5
4.7 4.5 4.3 4.7 4.5 4.3
118 112 107 1184 1120 1075
6. Conclusion The present study has shown that in the case of data acquisition with conventional digital systems (with metallic conductors), the sampled signals may be subject to electromagnetic disturbances of various nature. In fact, it is well known that an electric field is generated by both stationary and moving charges and that at the same time a magnetic field can be produced both by magnetic bodies and by charges in motion; moreover, fluctuating electric/magnetic fields can produce electromagnetic waves. We analyzed the measurements of an electric field E (100 k Hz– 6.5 MHz) with potentially disturbing frequencies and the magnetic flux density B (5 Hz–400 kHz) also including the low frequency connected to power signal (50 Hz). The results provided interesting indications showing values of the field E up to 0.82 V/m and of the field B with values up to 85 lT. All the measurements were performed taking into account the statistical significance by comparing the average values obtained both with the various percentiles (50, 75, 90) and with the standard deviations. Observing the anomalies maps (Figs. 4 and 5), it is possible to identify areas for which it would be advisable to avoid the passage
of signal lines and housing of data acquisition devices. Assuming the field E and B values obtained in this study, considering a standard conductor with diameter 1–2 mm and frequencies range of 106–107 Hz, we observed an inductance L up to 47 X on the cable corresponding to an EMF of 1184 mV. Observing the experimental SP data acquired in two onboard site (Fig. 7a–c) and the relative statistical parameters reported in Table 11, it is shows the EMI increment in site 2 where the Pearson index correlation calculated between the isotropic field E and the isotropic field B is higher than in site 1. Therefore, we believe that in an oceanographic survey planning, because the onboard acquisition systems are potentially affect by electromagnetic fields noise, a preliminary electromagnetic screening is needed to optimize the measurement setup where the E and B fields are expected to exhibit relatively low values and results in low distortions of the intended measurements.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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V. Di Fiore et al. / Measurement 147 (2019) 106889
Fig. 7. (a) SP sites measurement on board; (b) SP time series referred to site 1 (black line) and site 2 (red line); (c) Fourier spectra at the site 1 (black line) and site 2 (red line). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
11
V. Di Fiore et al. / Measurement 147 (2019) 106889 Table 11 Statistical parameters referred to SP time series acquired in the site 1 and 2. SP site
Average(mV)
SD(mV)
P-P max(mV)
P50(mV)
P75(mV)
P95(mV)
1 2
13.41 19.06
7.07 11.04
58 124
12 17
18 26
24 29
Acknowledgments The authors would like to thank the DSSTTA and in particular the Director Dr. Fabio Trincardi for supporting the survey planning. We would also like to thank the Minerva Uno crew and Sopromar Spa, the shipping company, for the availability and patience shown during the data acquisition phases and in particular during difficulties moments. Prof. Michele Meo is acknowledged for his comments that helped us in improving the manuscript. The research activities were carried out within the RITMARE Flagship that is one of the National Research Programmes funded by the Italian Ministry of University and Research - Sub Project ‘‘Forecasting and control of on-board electromagnetic emissions” – SP1_WP3_AZ6_UO01. References [1] H.M. Judson, The shipboard operating environment – a design challenge, Naval Eng. J. 94 (5) (2009) 41–45. [2] P. Xu, S. Hao, Y. Geng, T. Jiang, Research on EMC evaluation for communication systems on board, IEEE Xplore (2016), https://doi.org/10.1109/ ROPACES.2016.7465353. [3] S.T. Li, J.C. Logan, J.W. Rockway, Ship EM design technology, Naval Eng. J. (1988). [4] B.J.A.M. Van Leersum, D.W.P. Thomas, J.G. Bergsma, J. van der Graa, F.B.J. Leferink, Cable crosstalk and separation rules in complex installations, in:
[5]
[6] [7]
[8]
[9]
[10] [11] [12]
[13] [14] [15]
Electromagnetic Compatibility (EMC EUROPE), 2012 International Symposium on, Sept 2012, 2012, pp. 1–6. V. Di Fiore, F. Lirer, F. Budillon, N. Pelosi, M. Punzo, G. Zeni, M. Iavarone, P. Scotto di Vettimo, C. Barbalucca, Campagna Oceanografica Sismica, Magnetica ed Elettrica - Ischia (COSMEI) Technical Report, Solar-CNR, 2018, http:// eprints.bice.rm.cnr.it/id/eprint/18136. R.K. Wangsness, Electromagnetic Fields, 2nd ed., Wiley, 1986, ISBN 0-47181186-6. F. Zare, Electromagnetic Interference Issues in Power Electronics and Power Systems, Bentham Books, 2011, p. 117, ISBN: 978-1-60805-388-9, DOI: 10.2174/97816080524001110101. Norma CEI 211-6 (2001-01) Guida per la misura e per la valutazione dei campi elettrici e magnetici nell’intervallo di frequenza 0 Hz 10 kHz, con riferimento all’esposizione umana, Norma CEI 211-7 (2001-01) ‘‘Guida per la misura e per la valutazione dei campi elettrici e magnetici nell’intervallo di frequenza 10 kHz–300 GHz, con riferimento all’esposizione umana”. W.G. Duff, Designing Electronic Systems for EMC, SciTech Publishing Inc, Raleigh NC, 2011. H.W. Ott, Noise Reduction Techniques in Electronic Systems, 2nd ed., Wiley & Sons, New York, 1988. A. Gharib, H.D. Griffiths, D.J. Andrews, Prediction of topside electromagnetic compatibility in concept-phase ship design, IEEE Trans. Electromagn. Compat. 59 (1) (2017) 67–76, https://doi.org/10.1109/TEMC.2016.2606414. M. Bueno, A.K.T. Assis, Equivalence between the Formulas for Inductance Calculation, NRC, Canada, 1997, pp. 357–362. E. Bava, G. Galzerano, M. Norgia, R. Ottoboni, C. Svelto, Misure elettroniche di laboratorio, Pitagora, 2005, Anno edizione. E. Bava, R. Ottoboni, C. Svelto, Fondamenti della misurazione, Esculapio, 2005, Anno edizione.