Special Testing

SFRA TEST

Sweep Frequency Response Analysis (SFRA) is a powerful and sensitive method to evaluate the mechanical integrity of core, windings and clamping structures within power transformers by measuring their electrical transfer functions over a wide frequency range.

SFRA is a proven method for frequency measurements. SFRA analysis can detect problems in transformers such as:

• winding deformation – axial & radial, like hoop buckling, tilting, spiraling
• displacements between high and low voltage windings
• partial winding collapse
• shorted or open turns
• faulty grounding of core or screens
• core movement
• broken clamping structures
• problematic internal connections

DCRM TEST

• Saves down time & number of operations of CB by testing all the critical performance parameters of all the poles / breaks in a single shot.
• Healthiness of Auxiliary contact by measurement of Auxiliary contacts timings.
• Healthiness of Close / Trip coils of all three poles monitored simultaneously.
• Laptop operated.
• Results are immediately displayed on the screen.
• Contact Resistance of main contacts.
• Useful to shift maintenance schedule form Time based to Condition based.
• Work reliably under live EHV switchyard conditions ensuring operator's safety and repeatability of results.

HV TAN DELTA

Tan Delta is a diagnostic test conducted on the insulation of cables and windings, Bushing, Oil. It is used to measure the deterioration in equipments. It also gives an idea of the aging process in the cable/windings and enables us to predict the remaining life of the cable / windings.

Numerical Relay Test

Some basic aspects of numerical protections generally address this:

• The data acquisition and processing is totally different from older techniques. It is not only characterised by components but also by software algorithms. Moreover, non-analytical processing systems could be used that are based on Artificial Intelligence techniques (Neural networks, Expert systems, etc.).
• Input/output logic is often programmable. This introduces a new degree of flexibility with the consequence that additional, specific tests need to be performed on the protection scheme as a whole.
• The capacity of the microprocessor-based systems is rapidly increasing and generally precludes the need for single function relays. Protection is evolving to a multifunction box that affects the adequacy of the test programme. The function complexity of numerical relays has reached a level where it is impossible to test every performance possibility. Consequently, the difference between the function performance and scheme performance is increasing.

CURRENT, VOLTAGE AND POWER TRANSFORMERS

The following table lists the tests that can be performed on Current transformers (CT), Voltage Transformers (VT) and Power Transformers (PT):

CPC 100 OMICRON

Universal testing device for electrical diagnostics

Electrical tests on transformers, current transformers, voltage transformers, grounding systems, lines and cables, and circuit breakers can be performed with the CPC 100.

The CPC 100 is the base for multiple accessories. These facilitate further applications, such as tan delta measurements, as well as line and ground impedance measurements. The patented test system replaces several individual testing devices and offers new, innovative testing methods.

Applications:

• Current transformers (CT): Ratio, burden and polarity; Phase and magnitude error; Excitation curve; Winding resistance; Secondary burden; Dielectric withstand voltage (2kV AC); CT circuit continuity.
• Voltage transformers (VT): Ratio, burden and polarity; Phase and magnitude error; Excitation curve; Winding resistance; Secondary burden; Dielectric withstand voltage (2kV AC); VT circuit continuity.
• Transformers: Tap changer test; Excitation current; Short circuit impedance; Transformer coupling.
• Lines and cables: Impedance (k-factor).
• Grounding systems: Earth resistance and soil resistivity.
• Circuit breakers: Contact resistance measurement.