Power Transformer Testing Omicron Testrano 600

Omicron Testrano 600, a portable Three Phase Power Transformer Test Kit

The TESTRANO 600 is famously known as the first of its kind, a portable three-phase power transformer test set. It has the capability to support all known and common tests that can be performed on a power transformer. The TESTRANO 600 offers cutting edge technology that sets it above other power transformer testing equipments. Having a 10.6” TouchControl display makes using a laptop PC onsite not necessary but if desired, connection is allowed.

To use the TESTRANO 600, only three cables. These cables have multi-purpose functions and are connected to the transformer’s low and high voltage sides. This way, all tests can be carried out without having to make changes or new connections again.

Benefits of the TESTRANO 600

• True 3-phase power transformer test set
• Fast and reliable de-magnetisation of transformer’s core
• Powerful device with 3 x 33A DC or 400V AC
• Three times faster testing
• Reduced wiring effort as same wiring can be used for different tests
• Automatic tap changer control and measurement, no accessory required

Types of tests/measurements that can be performed/obtained using the TESTRANO 600 are

• Transformer turns ratio
• Frequency response of stray losses
• Exciting current
• Short-circuit impedance/leakage reactance
• DC winding resistance
• Demagnetisation
• Dynamic resistance
• Power/dissipation factor (with CP TD1)

For adequate operation and performance of a transformer, it is important to be aware of the transformer’s condition and health. The reason for this is as a result of many factors which can influence the longevity of the power transformer.  Hence, performing a diagnostic test as well as having the transformer monitored can result in reliable operation and longevity.  Since power transformers can be very expensive, this makes it all the more important to check and monitor its condition.

Factors Affecting Longevity of Transformer

1. Mechanical factors
2. Electrical factors
3. Thermal factors
4. Aging
5. Protection factors

Mechanical Factors

Examples of mechanical factors that can affect a power transformer include:

• Seismic activity
• Stresses due to short-circuitry
• Damage due to transportation

Electrical Factors

Examples of electrical factors that can affect a power transformer include:

• Overvoltages
• Lightning
• Short-circuit currents
• Switching surges

Thermal Factors

Examples of thermal factors that can affect a power transformer include:

• Overheating
• Overloading
• Ambient conditions

Aging

Examples of aging factors that can affect a power transformer include:

• Contamination
• Oxygen
• Moisture
• Acid
• Leakages

Protection Problems

Examples of protection problems that can affect a power transformer include:

• Failure
• Under-function

Considering these factors, performing power transformer testing regularly gives an overview of the overall condition of the transformer and lifespan. This way, conventional/sophisticated testing can be used in the detection of the mechanical and electrical factors and prevented. Thus, catastrophic and high-cost damages are also prevented. Whilst the TESTRANO 600 can be used, conventional methods such as measuring parameters like

• Short circuit impedance
• Transformers ratio
• The tap changer’s dynamic winding resistance
• Magnetising current
• Winding resistance

Some detectable faults to important components of a power transformer

1. Faulty bushings in a power transformer in the form of the occurrence of partial discharges in the insulation. Also, the presence of crack in capacitive graded layers and resin-bonded insulation.
2. Faulty leads can arise due to contact problems between the connectors as well as mechanical deformations of the leads.
3. Faulty insulation is a big issue with transformers and hence one of the main reasons for performing tests on transformers. Faults associated with insulation include the occurrence of partial discharges, moisture in pockets or contamination of the insulation.
4. Faults detected in the cores can be due to residual magnetism or mechanical deformation or shorted core laminates.

The importance of maintenance checks and tests on operating conditions of power systems cannot be overemphasised. Corrective measure to improve power transformer lifespan

1. The auxiliary components of a power transformer and performing maintenance checks on them can improve the lifespan of the transformer. Examples of such components include the tap changer, the breather and the cooling system.
2. The power transformer’s insulation should be monitored as well and if it needs changing or reconditioning. Signs to watch for are drying of the transformer, if oil treatment is required and/or if it needs changing.
3. Faults detected should be addressed immediately and if components are worn out and needs to be replaced. Examples of some important components are the bushings, pumps, fans, surge arresters and gaskets.