Designing a Rogowski coil with particle swarm optimization

Guillermo Robles; Muhammad Shafiq; Juan Manuel Martínez-Tarifa, Designing a Rogowski coil with particle swarm optimization, November 2018, Proceedings of the 5th International Electronic Conference on Sensors and Applications session Physical Sensors (doi: 10.3390/ecsa-5-05721)

Open access at

Abstract—Rogowski coils are inductive sensors based on Faraday’s and Ampère’s Laws to measure currents through conductors without galvanic contact. The main advantage of Rogowski coils when compared with current transformers is the fact that the core is air so they never saturate and the upper cut-off current can be higher. These characteristics makes Rogowski coils ideal candidates to measure high amplitude pulsed currents. On the contrary, there are two main drawbacks. On the one hand, the output voltage is the derivative of the primary current so it has to be integrated to measure the original signal; and, on the other hand, the transfer function is resonant due to the capacitance and the self-inductance of the coil. The solution is the use of a passive integration with a terminating resistor at the output of the sensor that splits the two complex poles and gives a constant transfer function for a determined bandwidth. The downside is a loss of sensitivity. Since it is possible to calculate the electrical parameters of the coil based on its geometrical dimensions, the geometry can be  adapted to design sensors for different applications depending on the time characteristics of the input current. This paper proposes the design of Rogowski coils based on their geometric characteristics maximizing the gain-bandwidth product using particle swarm optimization and adapting the coil to the specific requirements of the application.

Keywords—Rogowski coils; particle swarm optimization; gain-bandwidth product; current
measurement; magnetic field measurement.


20 puestos de especialización para jóvenes ingenieros y físicos aplicados en la 4ª convocatoria del Spanish Traineeship Programme, CIEMAT-CERN

En los próximos días, se abrirá la cuarta convocatoria del Spanish Traineeship Programme, FTEC-2018, un programa de especialización tecnológica en el CERN, Ginebra, Suiza, destinado a jóvenes ingenieros y físicos aplicados.

La convocatoria tiene como objetivo incrementar la presencia de investigadores y técnicos españoles en el CERN, así como consolidar un colectivo de ingenieros y físicos especializados en tecnologías de los grandes aceleradores de partículas, detectores e infraestructuras asociadas, con la finalidad de una futura incorporación a la industria e instituciones del sector.

Podéis encontrar más información en:


Online condition monitoring of MV cable feeders using Rogowski coil sensors for PD measurements

M. Shafiq, K. Kauhaniemi, G. Robles, M. Isa, L. Kumpulainen, “Online condition monitoring of MV cable feeders using Rogowski coil sensors for PD measurements”, Electric Power Systems Research, Volume 167, February 2019, Pages 150-162, ISSN 0378-7796,

Abstract— Condition monitoring is a highly effective prognostic tool for incipient insulation degradation to avoid sudden failures of electrical components and to keep the power network in operation. Improved operational performance of the sensors and effective measurement techniques could enable the development of a robust monitoring system. This paper addresses two main aspects of condition monitoring: an enhanced design of an induction sensor that has the capability of measuring partial discharge (PD) signals emerging simultaneously from medium voltage cables and transformers, and an integrated monitoring system that enables the monitoring of a wider part of the cable feeder. Having described the conventional practices along with the authors’ own experiences and research on non-intrusive solutions, this paper proposes an optimum design of a Rogowski coil that can measure the PD signals from medium voltage cables, its accessories, and the distribution transformers. The proposed PD monitoring scheme is implemented using the directional sensitivity capability of Rogowski coils and a suitable sensor installation scheme that leads to the development of an integrated monitoring model for the components of a MV cable feeder. Furthermore, the paper presents forethought regarding huge amount of PD data from various sensors using a simplified and practical approach. In the perspective of today’s changing grid, the presented idea of integrated monitoring practices provide a concept towards automated condition monitoring.

Keywords—Condition monitoring; Rogowski coil; Dielectric insulation; Partial discharge; Medium voltage cable; Transformer.

Becas de formación en el Instituto Nacional de Técnica Aeroespacial

Se han convocado 32 becas de formación en el Instituto Nacional de Técnica Aeroespacial para titulados universitarios dotadas con 12.000 euros anuales a razón de 1.000 euros brutos mensuales. La duración de las becas será de dos años, pudiendo ser prorrogadas, por un año más, siempre que el plan formativo lo contemple y exista disponibilidad presupuestaria.

La cumplimentación y presentación de las solicitudes se realizará, preferentemente, a través de los medios electrónicos habilitados para ello en la Sede Electrónica Central del Ministerio de Defensa en la dirección en el enlace “Procedimientos” “INTA-Becas” (se recomienda utilizar CL@VE). La fecha límite es el día 16 de noviembre de 2018.

La solicitud estará cumplimentada, correctamente una vez que se haya firmado la solicitud y se obtenga un justificante en pdf con el sello del registro electrónico del Ministerio de Defensa. También podrán presentarse en el Registro General del INTA en Ctra. de Torrejón-Ajalvir Km. 4, 28850-Torrejón de Ardoz (Madrid), o en cualquiera de los lugares previstos en el artículo 16.4 de Ley 39/2015, de 1 de octubre, del Procedimiento Administrativo Común de las Administraciones Públicas.

Más información en:

Y en el BOE del sábado 27 de octubre.


Partial Discharge Signal Propagation in Medium Voltage Branched Cable Feeder

M. Shafiq, K. Kauhaniemi, G. Robles, G. A. Hussain and L. Kumpulainen, “Partial discharge signal propagation in medium voltage branched cable feeder,” in IEEE Electrical Insulation Magazine, vol. 34, no. 6, pp. 18-29, November-December 2018.

doi: 10.1109/MEI.2018.8507714

Abstract— Rising global and regional electricity use is accelerating the need to upgrade networks. The adoption of sustainable ways of energy generation (renewables energy resources) is the top priority of today’s grid, and these resources are predominantly embedded within the distribution networks that are mostly connected by medium voltage (MV) cables. Driven by urbanization trends, negative land value impacts, public safety, environmental aesthetics, and network reliability, the resistance to overhead lines in distribution networks is gradually increasing in many countries. Either choosing the proactive path considering the operational superiority of underground cables compared with overhead lines or following the ongoing legislative policies, the use of cables has been increasing rapidly over the past 30 years. This trend is likely to accelerate.

Keywords— Power cables; Partial discharges; Power cable insulation; Cable shielding; Current measurement; Voltage measurement; Medium voltage; Condition monitoring; Cables; Branch; Joint; Diagnostic; Sensor},


Energy harvesting for a smart sensor with NFC capability

Autor/Author: Javier Molina
Director/Supervisor: Guillermo Robles
Master Thesis Document in pdf.


Abstract – Modern life’s concerns regarding unnecessary energy wasting and the unstoppable development of electrical engineering gave birth to the concept of energy harvesting. All this, along with an overwhelming number of internet connected devices, make necessary new smart devices to make easier our lives not only at home but also in industrial environments. Throughout this project, the feasibility of using a Peltier cell as a thermoelectric generator is discussed in order to scavenge energy from a heat source. This project aims at using this system in dicult access locations to create a smart sustainable system that can keep track of relevant parameters such as temperature, pressure or radiation. By implementing this self-powered system, there is no need to replace batteries when fully discharged, it is only necessary collect the data when required. In particular, this Peltier cell supplies an energy harvester module that powers a standalone microcontroller to establish a communication with a NFC module. This device embedded with a NFC tag will store the parameters measured by a sensor. This novel approach is intended to allow any NFC enabled device such as any modern smartphone to access this data to be subsequently analised and take action when needed.


Resumen – Las preocupaciones de hoy en da con respecto al consumo abusivo energetico sumado al gran desarollo reciente de la ingeniera electrica y electronica han dado como fruto el concepto de energy harvesting. Ademas, el mundo en el que vivimos con un mayor numero de dispositivos conectados a internet hacen necesario dispositivos inteligentes para facilitar nuestras vidas, no solo en casa, si no tambien en el entorno industrial. En este proyecto se expone la viabilidad de usar una celula Peltier que es un dispositivo termoeléctrico para proporcionar energa a partir de una fuente de calor. Este proyecto persigue usar este sistema en sitios de difcil acceso y crear un sistema sostenible que lleve a cabo un sistema de recogida de datos, como temperatura o presion. La ventaja que ofrece un sistema como este es que no es necesario cambiar la batera, puesto que el sistema se autoalimenta. Concretamente, la celula Peltier suministra energa a un modulo de almacenamiento que establece una comunicacion con un modulo NFC. Este dispositivo contiene una etiqueta NFC que almacena los datos recogidos por un sensor. Este enfoque permite a cualquier operario con un dispostivo que permita la lectura de etiquetas NFC, como por ejemplo cualquier smartphone moderno, acceder a estos datos para analizarlos y tomar decisiones si es necesario.


Movimiento en acimut y altura controlado por gestos mediante un acelerómetro conectado a Arduino

Autor: Sánchez Hernández, Víctor Manuel
Director: Robles Muñoz, Guillermo


A lo largo de este documento se describe el estudio de diversas soluciones dirigidas a la regulaci´on mediante gestos en altura y acimut de un dispositivo. Debido a la existencia de posibles escenarios que imposibilitan el trabajo humano directo, existe la necesidad de controlar procesos de forma remota a trav´es de una interfaz humano-m´aquina. Con el objetivo de hacer dicho control m´as ergon´omico e intuitivo, se pretende realizar el mismo mediante gestos. En este caso concreto, para ilustrar un posible entorno de trabajo, se estudia el control remoto de la posici´on de una antena de medida de descargas parciales en aislantes el´ectricos. Para dicho fin se utilizar´a un microcontrolador Arduino en varias configuraciones constituyendo dos m´etodos distintos de adquisici´on de datos de posici´on. La primera configuraci´on constar´a de un sensor capacitivo construido con planchas de papel de aluminio, modificando la posici´on de la antena en funci´on de la variaci´on de la capacidad percibida por dicho sensor. En la b´usqueda de una soluci´on m´as precisa y con una mayor probabilidad de implantaci´on industrial, se valorar´a la utilizaci´on de un aceler´ometro para llevar a cabo la funci´on descrita con anterioridad. Ambas configuraciones se utilizar´an para actuar sobre servomotores que componen el elemento de regulaci´on.

Palabras clave: Arduino, gestos, instrumentaci´on, aceler´ometros, sensores capacitivos, interfaz humano-m´aquina.

Documento en pdf (Spanish)



The present document describes the research made with the aim of the regulation of height and azimuth through gestures, taking into account diverse solutions. Due to the existence of possible enviroments where human manual work is not possible, there is the need of remote control of processes through an man-machine interface. As a consequence, gesture control is introduced to make this operation more intuitive and convenient. This document in particular carries out the study of the adjustment of an measuring antenna for partial discharges inside electrical insulators. In order to reach this goal, an Arduino microcontroller is used in different configurations, establishing two different methods of position acquiring. The first configuration includes a capacitive sensor based on aluminium films. Changes in capacitance are translated into position adjustments. Trying to achieve better accuracy and an easier industrial implementation, an accelerometer is used to detect this variety of gertures. Both configurations are used to control several servomotors which integrate the regulation method.

Keywords: Arduino, gestures, Instrumentation, accelerometer, capacitive sensors, man-machine interface (MMI).

Controlling a stepper motor via WiFi with an ESP8266 and Android

The idea of this work is to control the rotation direction, speed and position of a NEMA23 stepper motor remotely via WiFi. The application running in Android should send the parameters to the ESP8266 and this microcontroller would send the signals to the driver of the motor.

You can download the code in C for the ESP8266 here and the code in App Inventor for the application in Android to communicate with the ESP8266 here.

Stepper motor

Stepper motors are widely used in 3D printers so there is a large variety of models and manufacturers. The acronym NEMA stands for National Electrical Manufacturers Association and the nomenclature after the name refers to the size of the motor. It should be standarized so 23 would correspond to 2.3 x 2.3 inches, but most manufacturers do not follow these exact dimensions and, though they are close to the correct size, there may be differences. The selected motor for this application is a JK57HS56-2804 with the following data:

Step Angle: 1.8 degrees
Motor Length: 56 mm (close to 2.3 inches)
Current per phase: 2.8 A
Resistance per phase: 0.9 ohm
Inductance per phase: 2.5 mH
Holding Torque: 1.26 N·m
Number of Leads: 4
Detent Torque: 350
Rotor Inertia: 280 g·cm^2
Mass: 0.68 Kg

The interesting parameters in most applications are the current per phase which will condition the selection of the driver and the holding torque that would be determined by the application of the motor. In this case, we need a fairly high torque to move the rig described in this paper which consists on a horizontal rod and a vertical shaft connected directly to the stepper motor.

Driver DRV8825

The driver to control the rotation of a bipolar motor with four leads is a DRV8825 with a maximum current rating of 2.5 A as long as the circuit is refrigerated. Otherwise, the temperature protection will prevent the integrated circuit (IC) from working continuously. I used a forced ventilation with a small fan connected to 12 VDC and the current through the coils reached 2 A. All information about this driver can be found in the Pololu web page, but the most important is the connection pinout:

It is important to notice that both NOT_RESET and NOT_SLEEP are connected to high (or 5 V). I didn’t connect the 100 \muF capacitor to the power supply that was set to 25-30 V. The inputs M0, M1 and M2 are connected to low or high depending on the selected microstepping. There is a nice table in the Pololu web page and in the datasheet of the IC, however, I have to say the microstepping doesn’t work as expected: for instance, when you set a 1/16 microstep, the motor will turn for correctly for 8 microsteps and then it will jolt to the final position without continuing with the 8 remaining microsteps. This behavior seems to be common to the DRV8825 as it is also commented by Moritz Walker in his web page.


Finally, the STEP and DIR pins are connected to the GPIO4 (general purpose input-output 4) and GPIO5, respectively, of the ESP8266 microcontroller. The next figure shows the layout of the NODEMCU v1.0 which is a development board for the ESP8266 microcontroller. GPIO4 and GPIO5 are pins D2 and D1 respectively. When programming the NODEMCU, these pins should be defined as outputs. The DIR pin would be high to turn the motor clockwise and the STEP pin would receive a square wave with a predefined frequency to control the rotation speed. The higher the frequency, the higher the angular speed, so this square wave will be also a parameter that has to be defined.

Resultado de imagen de nodemcu ESP8266 pinout

The NODEMCU is natively programmed in LUA, however, I am more familiar with C and the Arduino IDE, so there is a possibility of using these tools with a plugin for Arduino, you just need to follow the instructions detailed here.

Now, the ESP8266 will work as a soft access point so it will create its own Wi-Fi network and we will connect our mobile app to this network and pass data to the MCU as shown in the next figure taken from this excellent page.

ESP8266 operating in the Soft Access Point mode

To do so, it is necessary to include this piece of code which also includes the definition of the pins as outputs and the additional variables that define the movement of the stepper motor.


#include "ESP8266WiFi.h"        //I can connect to a Wifi
#include "ESP8266WebServer.h"   //I can be a server 'cos I have the class ESP8266WebServer available
#include "WiFiClient.h"

const char *ssid = "ESPap";  //Credentials to register network defined by the SSID (Service Set IDentifier)
const char *password = "yourpassword"; //and the second one a password if you wish to use it.
ESP8266WebServer server(80);    //Class ESP8266WebServer and default port for HTTP

const int dirPin = 5; //This pin corresponds to GPIO5 (D1) (Yellow wire)
const int stepPin = 4; //This pin corresponds to GPIO4 (D2) (Orange wire)
int steps = 0; //This variable is related to the number of turns. If microstepping is disabled, 200 corresponds to a complete turn.
int stepDelay = 0; //This variable is the pulse duration in milliseconds and it is related to the rotation speed. Without microstepping, 1.8º are stepDelay ms.
bool dir = HIGH; //Rotation direction. HIGH is clockwise.

// Configure NODEMCU as Access Point
Serial.print("Configuring access point...");
WiFi.softAP(ssid); //Password is not necessary
IPAddress myIP = WiFi.softAPIP(); //Get the IP assigned to itself.
Serial.print("AP IP address: "); //This is written in the PC console.

void setup() {
pinMode(dirPin, OUTPUT); // Pins are outputs
pinMode(stepPin, OUTPUT);

Serial.begin(115200); //I can debbug through the serial port

The address will be written in the PC console, however, it has always been whenever I have used it.

Now, we have to define the handling functions that will be accessed in the path of the server. For instance, the root path direct to a function called handleRootPath and the /init path to another function called handleInit.

server.on("/", handleRootPath); 
server.on("/Init", handleInit); 

server.begin(); //Let's call the begin method on the server object to start the server.
Serial.println("HTTP server started");

And this code finishes the void setup() function.

Finally, the server is started. The loop function will only have a recursive function called:

void loop() {

that will handle the incoming of HTTP requests.

The function in the root path will inform that everything is ok when accessed by returning the code 200 and a plain text.

void handleRootPath() {
 server.send(200, "text/plain", "Ready, player one.");

The other function will parse the data sent by the app in the mobile phone and will send the outcome to pins DIR and STEP defined previously in the code and returns a message to the app showing that everything has been understood.

void handleInit() {// Handler. 192.168.XXX.XXX/Init?Dir=HIGH&Delay=5&Steps=200 (One turn clockwise in one second)
steps = 0; //Motor stopped if the arguments are wrong.
stepDelay = 0;
String message = "Initialization with: ";

if (server.hasArg("Dir")) {
 digitalWrite(dirPin, server.arg("Dir") == "HIGH"); //This is a cunning way of checking the value of the argument Dir.
 message += "Direction: ";
 message += server.arg("Dir");
 if (server.hasArg("Delay")) {
 stepDelay = (server.arg("Delay")).toInt(); //Converts the string to integer.
 message += " Delay: ";
 message += server.arg("Delay");
 if (server.hasArg("Steps")) {
 steps = (server.arg("Steps")).toInt();
 message += " Steps: ";
 message += server.arg("Steps");
 server.send(200, "text/plain", message); //It's better to return something so the browser don't get frustrated+ 
 for (int i = 0; i < steps; i++) { //Create a square wave signal with the incoming data.
 digitalWrite(stepPin, HIGH);
 digitalWrite(stepPin, LOW);

The data is sent as arguments in the URL 192.168.XXX.XXX/Init?Dir=HIGH&Delay=5&Steps=200 (One turn clockwise in one second).

Now, the objective of the app in the mobile phone is simply create the string with the URL based on the preferences of the user. This is easily done with MIT AppInventor.


The first step is to define the layout of the application and the elements in the screen. We need a button to connect to the access point defined by the NODEMCU, and another button to send the data introduced in two textboxes. The decision on what direction of rotation is done by ticking the desired choice in two check boxes.


Statistical correlation between partial discharge pulses magnitudes measured in the HF and UHF range

J.M. Martínez-Tarifa, G. Robles, J.M. Fresno and J.A. Ardila-Rey. Paper accepted in the International Conference on Dielectrics (ICD) 2018 — 2nd, 5th July — Budapest — Hungary

Abstract—Partial discharge (PD) detection using antennas has become a useful technique for condition monitoring of highvoltage equipment. However, one of its main drawbacks is the lack of knowledge for the quantification of the PD magnitudes, which is possible when conventional capacitive dividers or highfrequency
current transformers (HFCT) are used. This paper studies a possible relation between PD pulses measured in the HF and RF range. Different types of PD events were measured in the HF range using an HFCT and in the VHF/UHF range using two types of antennas. The peak value and the energy of each PD pulse have been studied for both HF and radio-frequency (RF) sensors, representing them in graphics. In addition, the possible
statistical dependence between variables (peak-energy; peakpeak; energy-energy) has also been quantified.

Keywords—Partial discharges, UHF measurements, HF measurements, Antennas, IEC60270, Correlation.

Los trabajadores del Sector de suministro de energía eléctrica tienen el sueldo medio más alto

Según la Encuesta anual de estructura salarial que tiene en cuenta la serie de años desde 2008 a 2016 publicada por el Instituto Nacional de Estadística – INE, la ganancia media anual por trabajador del Sector de suministro de energía eléctrica, gas, vapor y aire acondicionado es la mayor de España con casi 51.000 €. Le siguen el Sector de actividades financieras con algo más de 42.500 € e Información y comunicaciones por un lado e industrias extractivas por el otro con unos 32.400 € de media.

En la Universidad Carlos III de Madrid puedes cursar el Grado en Ingeniería Eléctrica que forma profesionales cuyo perfil coincide con el demandado por las empresas de suministro de energía eléctrica.

Ambos sexos
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