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)

www.koncar-institut.hr

3

How Do Problems Develop And Progress?

Bearing insulation and insulation stability of the bearing oil film deteriorate with usage

The impedance of the circuit consisting of shaft, bearing, oil film and other structural components decrease

Reduced impedance leads to current flow through the bearing

The current flow causes serious damage to the bearing

The proper and reliable work of the generator is jeopardized!!!!

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)

np

(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

www.koncarmonitoring.com