From Distribution Transformer to Smart Grid (Part 1)


A distribution transformer is a transformer that provides the final voltage transformation in the electrical power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. Distribution transformers normally have ratings less than 200 kVA, although some national standards can allow for units up to 5000 kVA to be described as distribution transformers.

Since distribution transformers are energized for 24 hours a day (even when they don’t carry any load), reducing iron losses has an important role in their design. As they usually don’t operate at full load, they are designed to have maximum efficiency at lower loads. To have a better efficiency, voltage regulation in these transformers should be kept to a minimum. Hence they are designed to have small leakage reactance.

Distribution Transformers are classified into different categories based on certain factors such as:

• Mounting Location: pole, pad, underground vault
• Type of insulation: Liquid, immersed or dry
• Phase number: Single-phase, Three-phase
• Voltage Class
• Basic impulse insulation level (BIL)

One of the major advantages of distribution transformer is that they have outstanding capability to survive overloads and Tailor-made to suit customer requirements.
But are they any problems that can disturb the transformer’s work? If exist, which are they? And how can the business avoid it?

The Problems that a Distribution Transformer can face:

Although the exact and arbitrative design of the distribution transformer, but it is evident that by the time this equipment faces lots and lots of problems such as:

• De-energized tap changer placement
• Mechanical fault
• Conductor melting
• Short circuits
• Winding fault arc
• Intra-turns fault arc

Also there are many hidden problems that are divided into electrical and non-electrical problems:

• Electrical problems: Earth fault, Over load, Under voltage, Over voltage, Phase over current, Over Frequency, Under Frequency, Outage)

• Non-Electrical problems: Oil level, Oil or gas pressure, Oil temperature, Status of LV/MV circuit breaker
Last but not the least we must don’t forget that devices using a magnetic circuit are sensitive to harmonics which have the effect of increasing the losses in the electrical equipment supplied by the network even though their aptitude is low. These losses in turn cause heating in the electrical appliances which thus co-ordinate their service life to be reduced

The major problems here are that Secondary transformer is a complex object, Visual confirmation of internal defects is not easy and Internal access is not obvious. Which allow to business Risk.

Need of looking in the invisible part of distribution Grid!!!
So what is the main Solution to avoid all that and to protect ones’Business?

Wait for our next article 😉 …

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