Voltage setting - Role, obligations and organization of producers for the needs of the French electrical system

Voltage regulation is essential for safe operation of the power system, minimizing losses and operating equipment within its normal operating range. On the transmission network, voltage regulation is carried out by controlling reactive power, because on this type of network, due to the characteristics of the lines, it is essentially reactive power transits that create voltage drops.

In France, there are three levels of adjustment to achieve the above objectives:

• primary regulation, which maintains the alternator stator voltage at a set value;

• secondary control, which coordinates the action of the generators at regional level and regulates voltage at strategic points on the network known as pilot points;

• tertiary control, which harmonizes control between regions and restores the reactive power margins of controlled units.

Today, these functions are performed by high-power synchronous alternators, which are the main sources of voltage on the grid.

The performance requirements for participation in voltage regulation are governed by regulatory texts, and are then set out in the operating documents of RTE, the French Transmission System Operator. Generators taking part in voltage regulation need to know the load on their generators in order to check that they are operating within their normal operating range, and to monitor wear and tear on this equipment. They also need to check that their installations comply with the performance requirements laid down by RTE in the contract for participation in System Services.

A method for constructing voltage/reactive operating diagrams (UQ diagrams) at the point where generators are connected to the transmission network, and for monitoring the operating points of voltage-controlled generators in real time, has been developed as part of this project. Generators have also developed monitoring and diagnostic tools to control the performance of their voltage regulation installations. Monitoring extends from the power plant control room (level 1) to the engineering centers (levels 2 and 3) through the use of e-monitoring tools. These tools make it possible to monitor the drift of parameters that are important for the safe operation of power plants and the power system as a whole.

Voltage regulation is a common good for all power system users. In this context, new regulating devices in the regulated domain (FACTS, inductors, capacitors) and also in the deregulated domain (wind farms and photovoltaics) can complement the actions of high-power synchronous alternators, which also belong to the latter domain. In the future, these new grid-connected...