engleski

Contactless transducer for simple and effective current measurement

In this paper is described the specific protection relay for all types of generators using new contactless transducer for current measurement. Namely, Shaft Current and Voltage Protection Relay (SCVP) that is developed at KONCAR – Electric Engineering Institute Inc. The most important parts of every electric power system are electrical rotating machines, especially those involved in the production of electrical energy. Nowadays electrical rotating machines must fulfill more complex requirements of electrical power system which are constantly increasing and at the same time the production of electrical energy must be optimized. On the other hand, longer lifetime and increased reliability of the machines is expected. Various monitoring and protection systems represent solutions for owners of expensive electrical machines and enable better asset management. This can prolong the lifetime of the machines and reduce costs caused by unplanned downtimes and unnecessary maintenance. Problems that can occur in electrical machines are shaft currents and voltages. Due to the asymmetry of the magnetic field in the machine, a voltage in the shaft can be induced, which depending on the type of machine, its size and load, varies in amplitude and frequency composition. Low impedance of the circuit consisting of shaft, bearing, oil film and other structural components, can cause shaft current flow which leads to bearing destruction. Continuous measurement and analysis of shaft currents and voltages can prevent major faults. Through detailed processing of the measured data the causes of occurrence of shaft currents and voltages can be identified. The main purpose of SCVP system is to detect shaft currents and voltages that may damage the generator bearing, and thus prevent greater economic damages. The aim of this paper is to present new contactless transducer that enables easier, simple and effective current measurement. This transducer is based on the Rogowski coil principle and PCB technology. This design enables sensor axial thickness of just a few millimeters and because of that the current transducer is lighter and thinner in comparison with widely used shaft current transformer.

Rogowski coil, SCVP, contactless transducer, PCB technology, shaft current measurement, shaft voltage measurement

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