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Transformer Testing & Analysis

Transformer testing is done for maintaining the specifications and performance of an electrical power transformer. The transformer is the main part of an electrical generation/distribution system so if it is not working properly then it will affect the whole generation/distribution system. Hence it is very important to make sure its perfectly fine for which periodical testing and maintenance is required. The need for transformer testing is to check the functioning of the transformer and to decrease the chance of failure. All electrical equipment needs to be maintained safely from some of the failures. Transformer failure can happen because of electrical, thermal, or mechanical factors. Insulation breakdown will also cause transformer failure. Power Electronical offers various transformer routine and special testing services with precise and reliable assessment for Power transformers, Distribution transformers, and Instrument transformers.

Routine Tests

Power & Distribution Transformer

A routine test in the transformer is done to confirm the operational performance of it. In this test the HV and LV winding resistance is measured. It also measures the insulation resistance of HV and LV windings with respect to the earth and between LV and HV windings. It also does the separate source voltage withstand test and this test checks the insulation property between primary to earth, secondary to earth, and between primary and secondary. It also does the overvoltage withstand the test. The voltage ratio will be measured in this test the voltage ratio is equal to the turns ratio in a transformer. Measurement of load loss and impedance in this test measures the power consumed by the transformer when the LV winding is short-circuited and the rated current is passed through the HV winding. It also does the dielectric and polarity test. Following are the Routine Tests performed by Power Electronical for Power and Distribution Transformers:

• Static Winding Resistance Measurement
• Insulation Resistance / Polarization Index
• Turns Ratio
• Voltage Ratio
• Open and Short Circuit
• Impedance Measurement
• Magnetic Balance
• Vector Group
• Functional Checking of Protection Devices
• Thermography

Special Tests

A special test is done as per the customer requirement to obtain information useful to the user during the operation or maintenance of the transformer. In this test, it does tests like dielectric and short circuit test, measurement of zero sequence impedance of three-phase transformers, measurement of acoustic noise level, measurement of harmonics of no-load current, and it also measures the power taken by the fans and oil pumps. Following are the Special tests of Power and Distribution transformers performed by Power Electronical:

• Sweep Frequency Response Analysis
• Partial Discharge Analysis
• Dielectric Frequency Response Analysis
• Frequency Response of Stray Losses
• Capacitance & Dissipation Factor measurement
• 10KV Excitation Current Measurement
• 10KV Turn Ratio Measurement
• Dynamic Winding Resistance Measurement
• On Line Water Content Measurement
• Transformer Oil Test – Screening Tests, DGA, FURAN and Corrosive Sulphur

Instrument Transformers

Instrument Transformers are used in AC system for measurement of electrical quantities i.e. voltage, current, power, energy, power factor, frequency. Instrument transformers are also used with protective relays for protection of power system. Thus they have a very important role in protection and monitoring of the system. Power Electronical offers testing and analysis of instrument transformers as well and performs following tests:

• Capacitance & Dissipation Factor measurement
• Partial Discharge Analysis
• Insulation Resistance / Polarization Index
• Polarity
• Ratio
• Primary Current Injection
• Knee Point Voltage Measurement
• Thermography