What is the Tan Delta Test?

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A pure insulator when is connected across line and earth behaves as a capacitor. In an ideal insulator, as the insulating material which acts as dielectric too, is 100 % pure, the electric current passing through the insulator, only have a capacitive component. There is no resistive component of the current, flowing from line to earth through the insulator as in ideal insulating material, there is zero per cent impurity.

In a pure capacitor, the capacitive electric current leads the applied voltage by 90o.

In practice, the insulator cannot be made 100% pure. Also due to the aging of insulators, the impurities like dirt and moisture enter into them. These impurities provide the conductive path to the current. Consequently, an electric leakage current flowing from line to earth through the insulator has a resistive component.

Hence, it is needless to say that, for a good insulator, this resistive component of the 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 a good insulator, this ratio would be quite low. This ratio is commonly known as tanδ or tan delta.

Sometimes it is also referred to as the dissipation factor.

Thus, tan δ = IR/ IC

NB: This δ angle is known as the loss angle.

On which instruments Tan Delta testing can be done?

Tan δ testing can be done on various power types of equipment used in substations like transformers, winding, current transformer, potential transformer, transformer bushing, cables, generators. It is performed to assess the quality of insulation and is performed in combination with various test likeTTR, WRM, etc.

Reasons for doing Tan δ testing?

The main purpose of the tan delta test is to make sure of maintaining a secure and reliable functioning of the transformer. The calculation of dissipation factor and capacitance values provides the result of insulation behavior of bushings and in windings too.

Variation in the capacitance value, for instance, indicates partial kind of breakdowns in bushings and automated movement of windings. Insulation deprivation, aging of the equipment, enhancement in the energy levels is transformed into heat. The amount of losses in these is calculated as the dissipation factor.

With the tan delta testing method, one can easily know the dissipation factor and the capacitance values at the required level of frequencies. So, any kind of aging factor can be identified earlier and the corresponding action can be implemented.

As we know that &#;Transformers&#; plays a very crucial part in power, so, first of all, will discuss Tan Delta Testing in Transformers.

Tan Delta Testing Process

The below process explains the method of tan delta testing in a step-by-step manner

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• The requirements necessary for this test such as cable, potential transformer, bushings, current transformer, and winding on which this testing is conducted has to be initially separated from the system.

• The minimal frequency level of test voltage is applied along with the equipment where the insulation to be analyzed.

• At first, normal voltage levels are applied. When the tan delta values are as expected at this voltage level, then the applied voltage level is increased by 2 times as of applied voltage.

• The values of the tan delta are recorded by the tan delta controller.

• To the tan delta calculating component, a loss angle analyzer is connected which compares tan delta values at higher and general voltage levels and delivers accurate results.

It has to be noted that the testing procedure to be carried out at very minimal frequency levels.

It is more recommended to conduct testing at minimal frequency levels, because when the applied voltage level is more, then the capacitive reactance of the insulator device reaches very minimal, therefore the capacitive element of the current reaches more. As the resistive element is practically constant; it is based on the applied voltage level and the insulator&#;s conductivity value.

Whereas at increased frequency level the capacitive current, is more, and then the amplitude of the vector amount of both the capacitive and resistive elements of the current reaches very high. So, the necessary level of power for the tan delta test would become more that seems to be not acceptable. Because of this, the power constraint for dissipation factor analysis, very minimal frequency test voltage is required.

What are the Different Modes of the Tan Delta Test?

When it comes to the tan delta test, there are essentially three modes of power factor testing. Those are

• GST Guard &#; This calculates the amount of current leakage to the ground. This method eliminates the current leakage through red or blue leads. Whereas in UST, the ground is termed to be guard because grounded edges are not calculated. When the UST method is applied to the device, then the current measurement is only through blue or red leads. The current flow through the ground lead gets automatically bypassed to the AC source and thus excluded from the calculation.

• UST Mode &#; This is employed for the calculation of insulation in between ungrounded leads of the equipment. Here the individual portion of isolation has to be separated and analyze it having no other insulation connected to it.

• GST Mode &#; In this final mode of operation, both the leakage pathways are calculated by the test apparatus. The current, capacitance values, UST, and GST guards, loss in watts need to be equal to the GST test parameters. This provides the entire behavior of the test.

When the summing value of GST Guard and UST is not equal to the GST parameters, then it can be known that there is some crashing in the test set, or might the test terminal are not correctly designed.

On the whole, this is a detailed explanation of the Tan Delta Test. Here, in this article, we are completely aware of what is a tan delta test, its principle, its purpose, its methods, and its testing technique.

Also, know about what are LV to earth test, HV to earth test, and LV-HV tan delta testing methodologies and keep reading KPM Technologies &#;TECH BLOG&#; and subscribe for different technological development in the field of power sector/ testing sector/ etc

How is the tan delta analysis configured for testing different voltage ranges?

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Tan delta analysis, also known as dissipation factor or power factor testing, is configured based on the voltage range of the equipment being tested. The configuration involves setting up the testing equipment to apply specific test voltages and measure the corresponding tan delta values accurately.

Here are the key steps involved in configuring tan delta analysis for testing different voltage ranges:

1. Selecting the Test Equipment:

• Choose tan delta test equipment suitable for the voltage range of the insulation being tested.
• Different equipment may be required for low, medium, and high-voltage applications.

1. Voltage Source Configuration:

• Configure the tan delta test equipment to generate test voltages within the desired range.
• Ensure that the voltage source is stable, accurate, and capable of producing the required voltage levels.

1. Calibration:

• Calibrate the tan delta test equipment against known standards to ensure accurate measurements.
• Perform regular calibrations to maintain the accuracy of the equipment over time.

1. Measurement Setup:

• Set up the tan delta analysis system to measure tan delta values accurately.
• Configure the system to capture data points at the specified test voltage levels.

1. Test Voltage Adjustment:

• Adjust the test voltage settings based on the specific voltage range required for the insulation being tested.
• Ensure that the test voltages align with industry standards or specific testing requirements.

1. Electrode Configuration:

• Configure the electrodes or test probes based on the type of insulation and the geometry of the test object.
• Ensure proper contact and alignment for accurate tan delta measurements.

1. Guarding and Shielding:

• Implement guarding and shielding techniques to minimize the impact of external factors on the measurements.
• Shield the test object and surrounding components to reduce interference.

1. Temperature Compensation:

• Implement temperature compensation mechanisms to account for variations in temperature during testing.
• Adjust tan delta measurements based on the temperature conditions to maintain accuracy.

1. Analysis Software Settings:

• Configure the tan delta analysis software to process and analyze data collected at different voltage levels.
• Set up the software to display and store tan delta values for each test voltage.

1. Frequency Settings:

• If applicable, tan delta analysis configure the analysis system to test at the desired frequency.
• Some tan delta tests may involve multiple frequencies, and the system should be set accordingly.

1. Data Averaging:

• Consider implementing data averaging to improve the reliability of measurements, especially in noisy environments.
• Set the averaging parameters based on the characteristics of the insulation material.

1. Safety Precautions:

• Adhere to safety protocols and precautions, especially when testing at higher voltage levels.
• Implement safety interlocks and emergency shutdown features to protect both the equipment and the operator.

1. Documentation:

• Document the configuration settings, including test voltages, electrode configurations, and any adjustments made during testing.
• Maintain a comprehensive record of each test session for future reference.

1. Verification and Validation:

• Verify the configuration settings by conducting preliminary tests with known samples.
• Validate the accuracy and consistency of tan delta measurements across the specified voltage range.

1. Adaptability for Variable Voltages:

• Ensure that the tan delta analysis system is adaptable to variable voltage ranges.
• Consider the flexibility to test a wide range of equipment with different voltage requirements.

By carefully configuring tan delta analysis for testing different voltage ranges and following these steps, engineers can conduct accurate and reliable assessments of insulation properties across a variety of electrical equipment. Regular calibration, adherence to standards, and attention to safety measures are crucial aspects of the configuration process.

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