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Condition Based Monitoring Specialist
Offiline Diagnostics Testing
Covers Insulation Resistance, Winding Resistance, Turns ratio, Tangent Delta, Partial Discharge, etc.
DC INSULATION RESISTANCE (IR)
DC Insulation Resistance (IR) is commonly used to determine overall insulation quality owing to contamination, absorbed moisture or severe cracking due to aging. This test is time dependent, and a time resistance test to see if insulation resistance deteriorates with time provides a good indication of the insulation condition.
A Polarization Index (PI) test is generally performed at the same voltage as the Insulation Resistance (IR) test. Where the IR test is performed for a period of one minute, the PI test is performed over a period of ten minutes. This gives the absorption (polarization) current ample time to decay, and reveals a more detailed indication of the total leakage and conduction current. As such, PI is a good indication of winding contamination, moisture ingress (leakage currents), and/or bulk insulation damage (conduction currents).
DC Insulation Resistance (IR) is commonly used to determine overall insulation quality owing to contamination, absorbed moisture or severe cracking due to aging. This test is time dependent, and a time resistance test to see if insulation resistance deteriorates with time provides a good indication of the insulation condition.
A Polarization Index (PI) test is generally performed at the same voltage as the Insulation Resistance (IR) test. Where the IR test is performed for a period of one minute, the PI test is performed over a period of ten minutes. This gives the absorption (polarization) current ample time to decay, and reveals a more detailed indication of the total leakage and conduction current. As such, PI is a good indication of winding contamination, moisture ingress (leakage currents), and/or bulk insulation damage (conduction currents).
TRANSFORMER TURNS RATIO (TTR)
Transformer Turns Ratio (TTR) is one of the most common test used to assess the condition of the transformer’s windings and core. It is performed as a part of acceptance and maintenance test procedure to determine any problems due to poor design, assembly, handling, overloading, fault conditions or poor maintenance. TTR results are compared against the nameplate ratings to determine any possible insulation deterioration, shorted turns, core heating or any other winding or core abnormalities.
Transformer Turns Ratio (TTR) is one of the most common test used to assess the condition of the transformer’s windings and core. It is performed as a part of acceptance and maintenance test procedure to determine any problems due to poor design, assembly, handling, overloading, fault conditions or poor maintenance. TTR results are compared against the nameplate ratings to determine any possible insulation deterioration, shorted turns, core heating or any other winding or core abnormalities.
TRANSFORMER WINDING RESISTANCE
Transformers are subject to vibration. Problems or faults occur due to poor design, assembly, handling, poor environments, overloading, or poor maintenance. Measuring the winding resistance of the windings assures that the connections are correct and the resistance measurement indicates that there are no severe mismatches or opens.
Transformers are subject to vibration. Problems or faults occur due to poor design, assembly, handling, poor environments, overloading, or poor maintenance. Measuring the winding resistance of the windings assures that the connections are correct and the resistance measurement indicates that there are no severe mismatches or opens.
TANGENT DELTA (TD) / DISSIPATION FACTOR (DF)
Tangent Delta test is used to determine an overall condition of the generator/motor/transformer winding.
For good insulator, resistive component of electric leakage current is quite low. In another way, the healthiness of an electrical insulator can be determined by the ratio of the resistive component to the capacitive component. For good insulator, this ratio would be quite low.
Tangent Delta test is used to determine an overall condition of the generator/motor/transformer winding.
For good insulator, resistive component of electric leakage current is quite low. In another way, the healthiness of an electrical insulator can be determined by the ratio of the resistive component to the capacitive component. For good insulator, this ratio would be quite low.
PARTIAL DISCHARGE (PD)
Partial Discharge test is normally performed to identify and locate the source of the defect. This test is only applicable for Generator, Motor, Bushing & Dry-type (Cast Resin) Transformer, and not for oil type Transformer.
Partial discharge is the main cause of insulation aging and breakthrough. The short discharge time will not cause the dielectric damage of the whole channel, and the electrolytic action of the discharge accelerates the oxidation of insulation, and corrodes insulation, so the life of the transformer is reduced.
Partial Discharge test is normally performed to identify and locate the source of the defect. This test is only applicable for Generator, Motor, Bushing & Dry-type (Cast Resin) Transformer, and not for oil type Transformer.
Partial discharge is the main cause of insulation aging and breakthrough. The short discharge time will not cause the dielectric damage of the whole channel, and the electrolytic action of the discharge accelerates the oxidation of insulation, and corrodes insulation, so the life of the transformer is reduced.
RECURRENT SURGE OCSILLOGRAPH (RSO)
The Recurrent Surge Oscillograph (RSO) test is a non-destructive diagnostic technique employed to detect inter-turn short circuits and ground faults in the rotor windings of large generators, particularly turbine-driven units. By identifying these faults early, the RSO test helps prevent potential failures and ensures the reliable operation of power generation equipment.
The Recurrent Surge Oscillograph (RSO) test is a non-destructive diagnostic technique employed to detect inter-turn short circuits and ground faults in the rotor windings of large generators, particularly turbine-driven units. By identifying these faults early, the RSO test helps prevent potential failures and ensures the reliable operation of power generation equipment.
Electromagnetic Core Imperfection Detection (ELCID)
Electromagnetic Core Imperfection Detection (ELCID) is a non-destructive testing method used to assess the integrity of stator core inter-laminar insulation in generators and large motors. This technique is crucial for identifying potential faults that can lead to overheating and damage during operation.
ELCID testing involves applying a low-level, low-frequency excitation current—typically around 4% of the machine’s normal operating flux—to the stator core. A Chattock coil (a specialized sensor) is then used to detect any fault currents that may indicate short circuits between the core laminations. These imperfections can compromise the insulation, leading to increased core losses and potential machine failure.
Electromagnetic Core Imperfection Detection (ELCID) is a non-destructive testing method used to assess the integrity of stator core inter-laminar insulation in generators and large motors. This technique is crucial for identifying potential faults that can lead to overheating and damage during operation.
ELCID testing involves applying a low-level, low-frequency excitation current—typically around 4% of the machine’s normal operating flux—to the stator core. A Chattock coil (a specialized sensor) is then used to detect any fault currents that may indicate short circuits between the core laminations. These imperfections can compromise the insulation, leading to increased core losses and potential machine failure.