Power Fluctuations in our AC Mains Power Generation Facility

Click For Summary

Discussion Overview

The discussion revolves around the voltage fluctuations observed in a 480VAC system at a steam power plant in Texas, specifically addressing the normalcy of these fluctuations when the plant is online versus offline. Participants explore the implications of these voltage swings on equipment operation and potential causes related to transformer characteristics and system connections.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the observed voltage swings from 480VAC to as high as 536VAC when offline are normal, noting they have not encountered such fluctuations at other power plants.
  • Another participant inquires about the type of power plant and its connection to the grid, suggesting that understanding the output specifications could clarify the situation.
  • A participant explains that the plant generates power for the grid and experiences voltage increases when offline, which causes operational issues with equipment like bolt heaters and cranes.
  • One response suggests that the transformers may have relatively high impedance and that the load could be at or over the KVA rating, indicating a need for monitoring the 4160V output.
  • Another participant proposes investigating the reactive neutralization and its connection when the plant goes offline to understand the cause of the voltage change.
  • A different viewpoint suggests that the power plant injects a capacitive current to maintain voltage levels, leading to higher voltage readings when disconnected from the grid.

Areas of Agreement / Disagreement

Participants express differing views on the normalcy of the voltage fluctuations, with some suggesting that the behavior is typical while others raise concerns about the implications for equipment operation. The discussion remains unresolved regarding the underlying causes and whether the observed behavior is acceptable.

Contextual Notes

Participants mention factors such as transformer impedance, load ratings, and reactive power management, but do not reach a consensus on the specific causes of the voltage fluctuations or their implications.

sponeill3031
Messages
2
Reaction score
0
I am currently at a power plant here in Texas and the 480VAC system swings from 480 while equipment is on line and as high as 536VAC when equipment is off line. They tell me that this is prefectly normal but I have never seen swings like this at any power plant. So, is this normal???
 
Engineering news on Phys.org
Welcome to PF.

What kind of power plant? Are you supplying power to the grid somehow, or just to a local facility? What are the output specs for voltage when it is online and supplying power to whatever?
 
Reply
  • Like
Likes   Reactions: russ_watters
It's a steam power plant and we generate power for the grid. Our line voltage is 19K that steps down to 4160 for some of our plant use and then steps down to 480 for plant use. While the plant is on line the voltage is 480 due to plant load but when the plant is off line (No plant load) the voltage goes up to 525 or 535. The issue we are having is when the voltage goes that high it causes significant issues when running things like bolt heaters, cranes and other portable equipment that contractors bring in to work on equipment during outages.
 
Sounds like the 19KV:4160 and/or the 4160:480 Transformer has relativly high impedance and the load is at or over the KVA rating. The Trans is tapped to be correct when the load is on.

Do you have a way to monitor the 4160V

A tapchanger for the 19KV:4160 may work, but tap changers on 4160 to 480 are rare.
 
Reply
  • Like
Likes   Reactions: berkeman
sponeill3031 said:
They tell me that this is prefectly normal but I have never seen swings like this at any power plant.
I would want to identify why such a change occurred. Maybe begin by identifying the reactive neutralisation and checking how it is connected, or partitioned, when the plant goes off-line.
 
In my opinion, the power plant [5-10 MVA at 20kV] injects a "capacitive" current in the System order to maintain 5 kV on System connection point.

So, when the plant works the voltage drop is negative and 4.16 is the voltage on the point of connection 4.16/0.48 kV transformer.

If the plant is disconnected then this transformer is supplied from the System and instead of 4.16, we get here 4.6 kV
Voltage up.jpg
 
Last edited by a moderator:

Similar threads

Is Baseload Power an Outdated Concept in Australia's Evolving Energy Landscape?
  • · Replies 31 ·
2
Replies
31
Views
3K
Is There Still a Market for Mechanical High Power DC/AC Generators?
  • · Replies 7 ·
Replies
7
Views
2K
AC Mains Generator -- RPM changes based on load changes
  • · Replies 5 ·
Replies
5
Views
3K
Power plant generator improvement
  • · Replies 20 ·
Replies
20
Views
3K
Thoughts for a low-power 60Hz 120Vrms signal generator please
  • · Replies 47 ·
2
Replies
47
Views
5K
AC generator output voltage to grid question
  • · Replies 4 ·
Replies
4
Views
3K
The Grim Power Outlook Spreads Beyond Texas
  • · Replies 17 ·
Replies
17
Views
2K
How transmission lines deliver (established?) power from generator
  • · Replies 8 ·
Replies
8
Views
3K
Could you use Solar to power a DC to AC Inverter? (Description below)
  • · Replies 6 ·
Replies
6
Views
4K
AC Power vs. Field Current of a DC Generator: Explained
  • · Replies 1 ·
Replies
1
Views
2K