HV Test Solutions
Different tests and measurements are performed during the maintenance and/or commissioning stages in transformers, motors, generators, and other electrical devices; a HV (High Voltage) test is typically used to determine the effectiveness of the insulation that allows them to operate with reliability and safety, and also as the way to get some important parameters for diagnostic and condition assessment purposes.
The requirements of HV test systems used on site depends on the nature of the device under test and the type and range of parameter that is being sought, so that the related HV test equipment differs much according to this; a HV test can be destructive or non destructive, it can be performed with AC or DC, and it can be searching for insulation resistance values, breakdown voltages, dielectric conditions, voltage ratios, etc; the following SMC equipment are products which use a HV test in search of some of those parameters with different HV test and measurement techniques.
HV test applications included in SMC products
We can differentiate between a HV test for transformers and a HV test for motors/generators, although sometimes the same test technique can be applied for both, since the analysis of the winding characteristics and performance is a common target.
The following SMC equipment are designed for HV test applications in transformers, among other applications:
The CV-05 configuration is the minimum required to perform a HV test with the Raptor System, and it is formed by the Raptor Master unit and the Raptor HV. The Raptor is an innovative and advanced substation test system that replaces the need for multiple test sets, with outstanding portability, modularity and adaptability for the main primary test applications in substations and switchgear.
The Raptor HV is an optional HV test slave that complements the Raptor System, extending the Raptor applications for testing transformers, among others. The main HV test applications of the Raptor CV-05 are the following:
- CT, VT and PT withstand voltage tests
- CT and VT excitation curve /knee point.
- VT and PT ratio measurement.
- Polarity test in VT’s secondary winding.
- Step & touch voltage measurements.
- Testing voltage sensors and converters.
This HV test unit is specifically designed as insulation resistance and recovery voltage meter; through a fully guided and automatic software controlled HV test, the ETP-2 detects problems such as contaminated insulation, paper and oil dielectric degradation or anomalous aging in the transformer with oil/paper insulation; it is a HV test with DC voltage injection in several cycles that gets the following parameters which are important for diagnostic purposes:
- Insulation Resistance (temperature normalized)
- Recovery Voltage
- Time Constant
- Polarization index
This HV test equipment is part of the ETP system for predictive power transformer maintenance, crossing results with the other units thanks to the expert software ETP Trends and ETP Diaghelp, for trending and diagnosis analysis of the successive tests stored in a common and organized database. The ETP-2 provides also an immediate report of the results.
The following SMC equipment is designed for HV test applications in motors, generators and electrical rotary machines.
This system use a HV test for the evaluation and diagnosis of the insulation condition in motors and generators; it is a HV test up to 6000 Vdc with two cycles, a charging cycle of 30 minutes and a discharge cycle of 2 min; two levels of HV test signals are used in the test, and the currents are measured during all cycles, both the charge and reabsorption currents.
For analyzing the condition of the stator winding insulation, the EDA system gets the following main parameters, which are displayed numerically and graphically:
- Insulation resistance (temperature normalized)
- Polarization index
- Capacitance ratio
- Absorption ratio
- Time constant
- Reabsorption current
- Leakage current ratio
The correlation of these parameters through expert software allows the detection of problems such as internal or superficial contamination, humidity, anomalous ageing, dielectric degradation, etc.
The EDA III integrates many measurements into a single system, together with an automated test which guides the operator during the process, and also combines the diagnostic and trending analysis; all this integration in a unique system is not provided by other kind of HV test sets, and made the EDA III a first level HV test system in the predictive maintenance of motors and generators.
For more information, please check the related SMC products or contact us.