Electrical rotating machines must fulfill ever increasing requirements of electrical power systems and at the same time optimize electrical energy production. Any malfunctions or unnecessary and unplanned outages can cause extensive material damage. The way to alleviate or even prevent such events is implementation of various modes of rotating machines monitoring and protection systems. They can enable better asset management, prolong the lifetime of the machines and reduce costs caused by unplanned downtime and unnecessary maintenance.
Through detailed processing of the measured data the causes of occurrence of shaft currents and voltages can be identified. The main purpose of shaft current and voltage protection (SCVP) system is to detect shaft currents and voltages that may damage the generator bearing, and thus prevent greater economic damages.
Through detailed processing of the measured data the causes of occurrence of shaft currents and voltages can be identified. The main purpose of shaft current and voltage protection (SCVP) system is to detect shaft currents and voltages that may damage the generator bearing, and thus prevent greater economic damages.
HOW DO PROBLEMS DEVELOP AND PROGRESS?
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. These asymmetries can cause a potential difference between two points on the shaft which leads to shaft voltage and thus eventually shaft current flow.
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.
The problem usually progresses with the following scenario:
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. These asymmetries can cause a potential difference between two points on the shaft which leads to shaft voltage and thus eventually shaft current flow.
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.
The problem usually progresses with the following scenario:
Generator damage resulting from shaft currents depends on amplitude and duration of current flow. For larger generators currents less than 1A should not cause greater damage. However, monitoring of the smaller currents over a certain time period has proven that there are cases when shaft current flow causes problems to the generators.
SOLUTION - SHAFT CURRENT AND VOLTAGE PROTECTION RELAY (SCVP)
Bearings damaged by shaft currents will eventually show increased vibrations which means that the damage is already done. The main advantage of our SCVP system is that it indicates a problem before major bearing damage has occurred. This is the reason why SCVP is recommended as additional monitoring system along with the classic protection relay function.
Our solution in form of an easy-to-install protection relay provides measurement and analysis of shaft voltage and current which may damage the generator bearing. Monitoring of shaft currents and a quick response to increasing amplitude of these currents is an easy way to protect the expensive power generation equipment.
Our solution in form of an easy-to-install protection relay provides measurement and analysis of shaft voltage and current which may damage the generator bearing. Monitoring of shaft currents and a quick response to increasing amplitude of these currents is an easy way to protect the expensive power generation equipment.
SYSTEM CONCEPT AND DESIGN
Architecture of SCVP system is a multi-channel processing unit with the real time controller combined with input and output analogue and digital modules. Processing unit is a fast and reliable industrial PLC, designed for harsh conditions and environments. It has all the necessary certificates and references for use with electrical machines.
SCVP system has a wide measuring range, signal frequency range up to 10 kHz and very low measuring error. High sensitivity for input currents and voltages allows measuring of relatively small signal amplitudes. The shaft current is measured by the special current measuring transformer installed around the shaft, usually under lower generator bearing.
The solution can be used with all types of current measuring transformers. The processing unit conducts FFT analyses of the input signal with high resolution and sampling frequency. Depending on the chosen configuration, if the analyzed data exceeds certain value, the appropriate signals are forwarded to the digital outputs or are stored in a database.
SCVP system has a wide measuring range, signal frequency range up to 10 kHz and very low measuring error. High sensitivity for input currents and voltages allows measuring of relatively small signal amplitudes. The shaft current is measured by the special current measuring transformer installed around the shaft, usually under lower generator bearing.
The solution can be used with all types of current measuring transformers. The processing unit conducts FFT analyses of the input signal with high resolution and sampling frequency. Depending on the chosen configuration, if the analyzed data exceeds certain value, the appropriate signals are forwarded to the digital outputs or are stored in a database.
RESEARCH AND KNOW-HOW BEHIND THE SCVP SOLUTION
Example of a generator 3D model with magnetic field distribution
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Mathematical calculations on generator models were the basis for development of SCVP system. In cooperation with a manufacturer of rotating machines, KONCAR – Generators and Motors Inc., complex 3D models of the generator have been developed. Using Finite Element Method (FEM) calculations on these 3D models electromagnetic conditions of the machine are determined.
These models are used to capture distribution of the magnetic field in the generator and to determine influence of magnetic field asymmetries on occurrence and signal waveform of the shaft currents and voltage. By using 3D models it is possible to simulate different conditions which occur in the operating generator. This allows for analysis of how such conditions influence the wave forms and spectrum of shaft current and voltage signals. |
SOFTWARE INTERFACE
SCVP system is accessed via a control cabinet on-site and remote online from any computer.
On-site HMI showing the SCVP options
Benefits for the users.
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EASY IMPLEMENTATION
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CONNECTIVITY
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USER FRIENDLY
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PROTECTION
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See for yourself why SCVP is the right solution for you by choosing one of the options below or simply contact us.