How we change voltage on a transformer

Former transformer designer here; just to nitpick a tiny bit – there are 3 types of tap changers:

OLTC – On load tap changer (Also called LTC): Can change taps on load

NLTC – No load tap changer: Can only change taps while there is no load but still energized

DETC – Deenergized tap changer: Must be dead before changing load

When hurricane Wilma struck Florida there were at least 10 lines poles down at a particular road by rim canal. Linemen as far as Canada came to the rescue. I was at a Marathon gas station in South Bay buying some snacks and dreams. There was also a Canadian man in full gear and looked tired. I thanked him for his labor and showed appreciation. You should have seen how his spirit was uplifted at that moment. He was very grateful for what I said. We should never take anything for granted specially when first responders and volunteers come to help those comunities in need.

Some pole tubs are duals like 4.8 and 7.2 or 7.6KV for delta or Y primary. Changing the voltage requires moving the NLT (NO LOAD TAP Changer). It has to be de-energized to move the tap switch. Easy – peasy. The delta capable tubs have two HV bushings. At First Energy we had 19.9 / 12.47 KV Duals (Y – Y). Some step banks have a NLT to adjust voltage, but most distribution tubs are not really adjustable at the tub. Check the tap changer at the sub and the SATAC reading. Also, if a cap bank is energized, try opening the bank. Even though they’re there for VAR correction a cap bank can bump up the voltage as much as 3 volts. Maybe change a fixed cap bank to one with a controller. to open when it hits 123.5 volts and cut-in at 117..

https://www.youtube.com/watch?v=Zg_EPmtbI58

CGPT

Transformers mounted on telephone poles, commonly known as pole-mounted transformers, play a crucial role in electrical distribution systems. Their primary function is to step down the high voltage from the distribution lines to a lower voltage suitable for residential or commercial use. The standard high voltage in distribution lines can range from 13,200 volts to as high as 25,000 volts or more, which is then typically stepped down to 120/240 volts for residential use in the United States, or to a similar low voltage level suitable for the region where the system is implemented.

### Adjusting Line Voltage

The process of adjusting line voltage through a pole-mounted transformer is not something that is done dynamically in the field; instead, transformers are designed and installed to provide a specific voltage transformation ratio based on the requirements of the electrical distribution network and the needs of the end users. However, there are a few key concepts and components related to how transformers can accommodate or be part of systems that manage or adjust voltages:

1. **Tap Changer**: Some transformers are equipped with a tap changer mechanism that allows utility personnel to adjust the transformer’s voltage ratio. By changing the connection point along the transformer’s coil (tapping), the output voltage can be slightly increased or decreased to accommodate variations in the distribution system’s load or to manage voltage levels within a desired range. Tap changers can be manual, requiring a utility worker to physically make the change, or automatic, responding to system conditions.

2. **Voltage Regulators**: While not part of the transformer itself, voltage regulators are often used in conjunction with transformers in the distribution system to maintain a stable voltage level to the customers, despite fluctuations in load or supply voltage. Voltage regulators can adjust the voltage in more finely tuned increments than is possible with transformer tap changers alone.

3. **Load Balancing and Phase Shifting**: In more complex distribution networks, special transformers, including phase-shifting transformers, can be used to manage power flow and balance loads across different phases of the system. While not directly related to adjusting the voltage for end-user consumption, these transformers help ensure the stability and efficiency of the power distribution system, indirectly affecting the quality of the voltage received by the end users.

### Safety and Professional Handling

It’s important to note that adjusting the voltage output of a transformer or working with any component of the electrical distribution system is highly dangerous and should only be performed by trained utility professionals. Unauthorized individuals should never attempt to access or modify transformers, voltage regulators, or any other part of the electrical distribution infrastructure due to the risk of severe injury or death from electric shock.

### Conclusion

Pole-mounted transformers are set to provide a specific voltage transformation based on predetermined needs, and adjustments to line voltage are generally managed through designed features like tap changers or through additional system components like voltage regulators. These tasks are carefully managed by electrical utilities to ensure safe, reliable power delivery to all users.

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