I'm trying to understand exactly how an electrical grid works, and I'm having one simple question that is challenging me. What happens when a new load appears on the grid? I know in practice that any single small load doesn't matter, so let's say it is either a small grid or a huge load. I'm assuming whatever is done it is enough to affect the grid in a measurable way.
My thought is that the new load will attract more current on the power lines, going all the way back to the electricity generator. In order to provide the same power out, the voltage will effectively drop slightly. Measuring the current level of the voltage along several lines is a good way to determine the load, which will let the grid know if power plants need to operate at higher levels, or turn on additional power plants. When a new plant comes on, it will come on slowly, which will allow for more current to pass through the devices, and increase the voltage on the system somewhat. If the same load turns off then later, then less current is running through, which will increase the voltage. Is this understanding even remotely close?