8+FAQ About The Generator Transformer

A power distribution grid relies on numerous components to deliver power to the population. From power generators to your homes, electricity undergoes a series of “transformations” to enable efficient distribution. This transformation of electricity is the main role of a transformer.

By stepping up the voltage, we allow electricity to travel long distances. 

Meanwhile, by stepping down electricity, the high voltage of power from lines becomes usable by the general public. Such is the importance of transformers in the power grid. 

This article will discuss the transformer at the heart of power generation, the generator transformer.

Now, if you’re looking for generator transformers or similar electric products, you should check out Daelim Belefic. Jiangsu Daelim Electric Co. Ltd is a trusted electrical manufacturer with over 15 years of excellent reputation.

Daelim has a wide selection of electrical products, including generators and power components. 

The company offers high-quality products and ensures compliance with ANSI, IEEE, CSA, and IEC standards.

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What Are Generator Transformers?

The generator transformer is the most important transformer on a power station and connects the generator output to the grid. 

We rate them according to how much power they can carry for that size of the system.

This machine is what directly converts generated electricity to higher voltages which allows easier distribution.

 Thus, for this reason, generator transformers are mostly step-up transformers and oil-filled transformers.

Oil-filled cooling is necessary for the more efficient handling of loads. 

This cooling is necessary as generator transformers can undergo abnormal power levels and operate at near 100% capacity.

You should also place a generator transformer in a high-risk area with a fire protection system like other oil-filled transformers. 

We’ll discuss generator transformer unit protection in the latter part of this article. 

Special design considerations are necessary for this transformer to withstand abnormal conditions from thermal and mechanical stress.

Generator Transformer
Generator Transformer

What Are Generator Transformer Specifications And Requirements?

A generator transformer is a virtual device that can be single or three-phase units depending on the device’s specifications. 

This transformer must endure extreme temperatures without deteriorating as it is subjected to full-time operations at levels of capacity requirements.

Large modern generators are often designed to operate at around 11 to 30 kV. Ideally, the generator designer wants to limit the stator current to meet the desired outputs.

The generation is usually not located near the load centers for economic transmission. 

A transformer steps up the voltage output to that of its distribution lines to reduce the load on the generators. 

Nowadays, power stations are designed on the unit principle, meaning that each generator will have its dedicated step-up transformer

It is an efficient way to produce reliable power for the grid.

For the performance requirement, here are industry standards manufacturers should observe:

  • Generator transformers must have a rating of at least 0.85 power factor lagging or 0.95 power-factor leading. Meanwhile, a 0.7 power-factor lead is necessary for half its maximum output.
  • An HV voltage of 400 kV or higher is required. Similarly, the LV current is also expected to be high. For example, around 20 000 amps current threshold for an 800 MVA, 23.5k volt transformer.
  • For an effective system, the impedance must be lower. Around 16% is usually specified over a wide range of ratings. Furthermore, you should keep variations with tap position to a minimum to simplify the system design and operation.
  • Low loss and low flux density design.
  • Noise generation should be at the most minimal levels.
  • An on-load tap-changer is generally necessary to allow HV system variation in voltage and generator power factor. Generally, LV voltage will stay within +/-5% under the control of the generator autoregulator.

You should also note that there is a different opinion prevailing on some utilities. 

See, on-load tap changers can cause unreliability in areas with the highest priority availability and load factor.

These generator transformer specifications and requirements are just a few you should check before making a deal. 

For best and tested performance results, you can consult your trusted transformer manufacturer like Daelim. 

From them, you shall receive assistance from professionals who are experts in this field.

What Are Generator Transformers’ Unit Protection?

Generator transformers are subjected to high-performance demand that can be taxing on the machine. 

Thus, machine failure is always part of the consideration and is often prepared with safety precautions. 

For this part, enumerated below are the common generator transformers’ unit protection :

Unit Isolation and Control

It is paramount that all generators, transformers, transmission lines, and distribution feeders are protected from short circuits in electrical safety. 

Thus, it is a standard in electrical practice to isolate most vital devices like the generator transformer.

In the most straightforward concept, a fuse detects the fault by burning out and thus isolating the line. 

This principle also applies to more complex systems as well. 

Such wherein professionals use micro-processing relays to detect the fault and determine which breakers need to activate.

One type of this sophisticated design is the Supervisory Control and Data Acquisition or SCADA.

This system configuration allows for remote or automatic control over components involved in the system.

Earth Fault Protection

Devices like the Restricted Earth Fault Protection (REFP) system protects against earth faults. 

By breaking the circuit when the fault current reaches the threshold, prevents damage to downstream equipment.

Experts use certain devices to restrict the electrical current in case of an earth fault. Earth fault relay, ground fault circuit interrupter, and earth leakage circuit breaker are among these.

Overcurrent Relaying

Another method is to apply overcurrent relays to ensure that a short circuit won’t affect your transformer. 

Experts place instantaneous relays, and it prevents current from operating when a secondary short circuit occurs.

Differential Protection

Differential protection is a type of unit protection that monitors the differential current for faults. It is because the input and output currents are never equal. 

As the current in the windings becomes unequal, it energizes the operating coil. 

Afterward, it sends a voltage to the load to balance it back out.

As the technology improves, experts get to develop more and more safety features for transformers. 

These unit protection designs are vital to keeping your transformers reliability and safety at peak. 

Always ask which are the best options for your case when consulting with a manufacturer.

Generator Transformer Design

It is important to note that transformer designs and station layout can be varying. 

Electrical designers have a set of different considerations that affect the configuration. 

Thus, it is imperative to consult an expert for your setup.

Nonetheless, although a variation is commonplace, tried and tested configurations are still prevalent in the industry.

For example, a registered design for the 660 MW generators rated at 800 MVA and bunked with 3 single-phase units.

There are also cases where switchgear is designed to disconnect from the grid and reconnect to the generator automatically. 

This design prevents a power overload caused by an electric company’s response to a generator trip.

What Is Step-Up Vs. Step-Down In Power Generation and Distribution?

Generator transformers are usually step-up transformers as they need to ramp up voltage for efficiency considerations. 

However, stations also occasionally use step-down transformers to power generator components. 

In concept, step-down transformers can be involved in the generator’s output flow. 

Meanwhile, step-up transformers are necessary for output regulation.

Technically, we classify generator transformers as power transformers. 

These types are expected to perform at higher loading capacities, an estimated 0.85 to 0.95 power factor. 

Furthermore, they are undergoing constant load and can face occasional overloads, which they should be designed to withstand.

Power transformers are transformers usually involved in power generation in substations and similar facilities.

Meanwhile, the step-down variant is more prominent as distribution transformers convert high voltage currents to usable rates. 

They are the end gateway of electricity before common households can benefit from power. 

Unlike power transformers, they can be below 0.75 power factor and handle significantly lower loads.

What Is The Difference Between Generator And Transformer?

Although both devices follow the principle of electromagnetic induction, their function is distinct from one another. 

A generator is mechanical, while a transformer is static. 

A generator converts mechanical power to electricity, while a transformer simply converts the electrical voltage.

A generator consists of a rotating conductor in a magnetic field, inducing an EMF. 

Meanwhile, the transformer involves an alternating current in one wire, which changes the magnetic field and induces an EMF in another wire.

Generator Transformers
Generator Transformers

Does A Generator Need A Transformer?

Generators use different voltage ratings in producing electricity. 

With a transformer, you can use the maximum voltage capability of the generator and get more out of that power.

Can Transformers Generate Power?

No. Transformers cannot generate power. They simply convert voltage to the desired rating. 

Power “generation” is the job of transformers.

For generator transformers and related services, be sure to consult with Daelim. 

Daelim has everything when it comes to electrical products and solutions. 

Daelim is your partner in cutting-edge electrical innovations and technology.

About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.

Custom Generator Transformer

When you need to find more than just existing transformers, Daelim’s Transformer Service Center can help you design and produce distribution transformers that meet your unique needs.

We have our own factory and a professional team of engineers, which can design and modify application requirements that meet all your conditions.

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