Ivan Gašparac

Bluetooth wireless communication and 1-wire digital temperature sensors in synchronous machine rotor temperature measurement

This paper addresses the usage of digital temperature sensors in rotor temperature measurement. A rotor temperature measurement system had to be developed because of the complete synchronous machine thermal analysis. Rotor temperatures are measured using multiple DS18B20 digital thermometers and sent via a wireless link to the host. The measurement system has been mounted on a 400 kVA synchronous generator and the temperature measurements in rotation are presented.

Comparison of expected and measured values of luminance sensors in dual-axis photovoltaic positioning system

A dual-axis photovoltaic positioning system has a primary task of directing a PV module towards the optimal light source. The idea of positioning a loop requires proper information on the PV module direction in order to get more insolation, i.e. more energy. The assumption of a proper luminance sensor distribution and position is described in this paper. With this distribution every angle position is described by a unique combination of luminance sensor readings. This paper compares expected readings and measured readings of a real mechanical model.

Some problems of synchronous hydro-generator temperature measurement

During complex measurements on synchronous hydro-generator 35 MVA, among other measurements, temperature measurement of stator winding end was realized. The real aim of this temperature measurement was to determine influence of excitation winding on armature windings during different operation points. This paper describes the measurement procedure, measurement system and some problems that occurred during this measurement.

Structure of physical model for research of traction parameters of electrical vehicle

This paper will present a laboratory model for research of traction parameters of electrical vehicle. Closely, this laboratory model is used for research of electrical drive. The detailed description of laboratory model and some recorded data will be presented.

Large turbogenerator's synchronous reactance's load dependence determined by measurements

The paper presents research on underexcited turbogenerator operation capability. Measurements of basic electrical values for various loads have been carried out in case of 247 MVA turbogenerator. Synchronous reactance for various loads has been determined from measurements. Its influence on underexcited operation limits has been evaluated.

Measurement Systems for Electrical Machine Monitoring

Monitoring systems on electrical machines, nowadays largely present on new electrical rotating (synchronous generators) and non rotating machines (transformers) have to endure harsh conditions such as vibrations and electromagnetic disturbances. Also, especially for rotating machines, rotor physical quantities (temperature, strain, current…), have to be transferred to the standstill part of the measurement system without galvanic contact. Therefore, monitoring systems should be, and usually are, designed for a specific purpose and for a specific machine. Some essential parts are the same but most of the monitoring system should be custom made especially if one takes into consideration that there is a small serial production of large electrical machines in the world and that most of the large units are unique. Modern monitoring of big transformers covers permanent on-line monitoring of electrical, magnetic and mechanic quantities. It is specific when compared to rotational electrical machines because it also usually includes monitoring of dissolved gasses in transformer oil. This information, with proper interpretation, represents an important element for transformer state determination. However, transformer monitoring systems are not the focus of this chapter. This chapter deals with all problems, obstacles and solutions applied to two measurement systems installed on a 35 MVA hydro-generator and a 250 MVA turbo-generator. Large electric machines justify investment in measurement systems for several reasons. Usually, measurement systems for bearings are installed. In such systems vibrations and oil parameters (pressure and temperature) are monitored to help maintenance. Measurements of stator and less often rotor currents are also present as parts of different systems. For example, a differential stator current measurement is present for protection purposes and enables detection of current leakage (short circuit between phase windings). Monitoring systems that incorporate all necessary measurements and, of course, interpretations of those measurements are almost non existing and very rare. This chapter will concentrate on synchronous generators.

Vehicle drive wheel torque computer modeling

In modern automobile industry a vital part of development and research is based on computer simulations and computer aided design. Building physical models of vehicle and testing them in different situations is highly expensive and requires a lot of time and effort. To reduce the time to market, development and research costs computer simulations and models are used. These computer models have to be evaluated. This paper describes the process and problems of creating computer model of a vehicle traction system in a Matlab/Simulink graphical simulation language and comparison of real vehicle drive wheel torque measurement with values in computer model.

Ensuring synchronous generator special standstill tests

During extensive testing of 35 MVA synchronous generator, some tests in standstill were conducted. For those tests rotor was blocked and different DC currents were driven through excitation and armature winding. In order to ensure all necessary conditions for such tests lots of preparations were made. This paper will thoroughly explain all problems that come out of such request and solutions for them.

Overvoltages and power oscillations in hydro generators

The paper describes two specific transient phenomena of different characteristic frequencies. First, a short overview of a calculation of overvoltages in the generator main electrical circuit of a hydro power station is presented. A case of a generator connected to the step-up transformer through encapsulated lines has been studied. The most critical cases have been considered: overvoltages at a single phase earth fault in the generator circuit and temporary overvoltages due to the single phase earth fault followed by the load rejection. The calculations have been carried out by EMTP-ATP and MicroTran program. Second, electric power oscillations in hydro power plants are not rare. The paper shows two cases in two different power plants. Each power plant has different generator positions (one vertical and one horizontal bulb type) and therefore different reasons for power oscillations. An overview of those cases is presented supported by measurements and calculated by Matlab.

Effects of interruption in power supply of induction motors in isolated electrical grid

The aim of this paper is to analyse effects of power supply interruption on dynamics of induction motors connected to a synchronous generator in an autonomous operation. A complex mathematical model has been developed, whose components are: a diesel engine, a synchronous generator, a mechanical connection, and two unregulated induction motors which are fed directly from the synchronous generator terminals.