Shaft current and voltage protection - introduction to solution

SHAFT CURRENT AND VOLTAGE PROTECTION RELAY (SCVP) www.koncar-institut.hr Due to magnetic field asymmetry in the machine, voltage in the shaft is induced, which, depending on the type of machine, its size and load, varies in amplitude and frequency composition. Low circuit impedance consisting of shaft, bearing, oil film and other structural components, causes shaft current flow which eventually leads to the bearing destruction. Shaft Current and Voltage Protection Relay (SCVP) is used to measure/analyze shaft voltage and current that may damage the generator bearing. 3 SCVP (SHAFT CURRENT AND VOLTAGE PROTECTION RELAY) 1- Instrument transformer (shaft current measurement) Operator panel - HMI Ethernet 3 2 - Sliding brush (shaft voltage measurement) 3 - Sliding brush (shaft voltage measurement) 1 2 3 SCVP Features • On-line analysis • Protection based on harmonic composition • Data base (trends, transients, waveforms, alarms …) • Local/remote HMI • Real trending based on process parameters • Advanced automated reporting Analog signals SCVP (CONCEPT) Remote user Web HMI SCVP (SENSORS) Instrument transformer (current measurement): • Transfer ratio: typically 1:1000 • Dimension: depending of shaft diameter • Test winding: yes • Typical transformer curve Sliding brush (voltage measurement) SCVP (SYSTEM CAPABILITIES) SCVP Analog signals (shaft current, shaft voltage) Process parameters (power, …) 1 PROTECTION (based on preset limits and signal frequency composition) 2 MONITORING (measured data are stored into a database. This enables comparison of the measured data with the previously recorded data) 3 FAULT RECOGNITION (based on FEM simulation models the system recognizes some faults and asymmetrical conditions of the machine) SCVP (PROTECTION) Usually the 1st or 3rd harmonic is selected for the protection purpose SCVP (MONITORING) Real-time measurements, spectrums, alarms, trends, transients, setup SCVP (MONITORING) Real trending (restrictive class data storing based on process parameters) n??p (n=1,2,3..) V Voltmeter measuring coil no. 1 measuring coil no. 2 SCVP (MONITORING) Real trending (magnetic field asymmetry as restrictive class parameter) SCVP (AUTOMATED REPORTS) REPORT