How to Connect a Genset to the Grid

Technician connecting a generator in an industrial setting
Connecting a generator set to the power grid of an industrial or commercial facility is a key process to ensure a continuous supply during grid failures.

In sectors such as industry, hospitals or data centres, where energy is vital, it is essential to know the correct steps and methods to make a safe and efficient connection.

Basic concepts for the connection of a generating set

Before proceeding with the installation of a generating set, it is essential to carry out an exhaustive analysis of the electrical demand of the installation. This involves calculating the power required for critical equipment, verifying current safety regulations and correctly sizing the system components.

Each installation has specific needs, so it is essential to design a system that guarantees a reliable supply and complies with protection standards.

Key requirements include

Critical load assessment: Identify which areas and equipment need continuous supply in the event of mains failure.
System planning: Determine the type of generator set, switchgear capacity, and the voltage and frequency to be supplied.
Regulatory compliance: Ensure that the design of the installation complies with low voltage regulations and that all relevant safety measures are in place.

General view of a shopping center where energy is essential

Methods of connection of a generating set to the mains

Direct connection of the generating set to the grid

To ensure efficient switching between the mains and the generating set, it is essential to use a switchboard. This device automatically detects any mains failure and switches over to the genset without manual intervention (in case of an automatic system). The ATS (automatic switchboard) is the key element in installations where the continuity of the power supply is critical, as it ensures that the change of the power supply is carried out without cuts or with a minimum cut-off.

Learn more about the mains/generator switching process here.

The installation process of an ATS includes the configuration of its parameters so that, in the event of any mains failure, the system can start the generator and transfer the load instantaneously. This type of automation is essential in sectors such as hospitals, data centres or telecommunications infrastructures, where any interruption may be unacceptable.

Connecting a three-phase genset

In high-demand industrial environments, three-phase gensets are often used to ensure a balanced power distribution. These generators operate using three phases of alternating current and can be connected in two main configurations: star or delta.

Star connection: In this scheme, all phases are connected to a single neutral point, which facilitates the balancing of distributed loads.
Delta connection: In this type of connection, the end of one phase is connected to the beginning of the next phase, creating a closed loop between the phases.

The choice between these two schemes will depend on the type of load, the power required and the infrastructure available in the installation.

Connection to critical systems

In critical facilities such as hospitals, telecommunications centres or industrial plants, it is crucial that certain equipment is always kept operational. For this purpose, secure lines are implemented that directly connect critical systems to the generator set.

These lines are designed to receive power immediately in the event of a grid failure. In addition, many of these systems include redundancies and continuous monitoring, ensuring that the generator set is always ready to start when needed. In these cases, it is common to use several generators connected in parallel to improve security and supply capacity.
Doctors in a hospital reviewing an X-ray

Steps to connect a generator set safely

1. Assessment of the installation’s power and requirements

The first step to a proper connection is to make a detailed assessment of the power required by the installation during a power outage. This includes identifying the equipment requiring continuous supply and determining the rated and starting powers to be provided by the genset.

It is crucial to correctly calculate the critical load to ensure that the selected generator is able to cover all the needs of the facility without overloading.

2. Configuration of the Automatic Transfer Switchboard (ATS)

The ATS is responsible for the automatic switchover between the mains and the genset. Its correct configuration is key to ensuring that the system reacts quickly and efficiently to failures in the mains supply. This includes adjusting the delay times, the sensitivity of the system to detect fluctuations in voltage and frequency, as well as the generator start and stop settings.

A well-configured ATS not only ensures efficient switching, but also protects both the generator set and the connected equipment from possible fluctuations or failures in the grid.

3. Installation of conductors and protections

To ensure the safety of the installation, it is essential to correctly select the conductors and protective devices, such as fuses, differential and thermal relays. In three-phase installations, it is particularly important to ensure that the three phases are balanced to avoid problems of overload in one phase and underutilization in the others.

The dimensioning of the conductors must be done according to the capacity of the generating set and the distance between the generator and the switchboards. In addition, independent earthing systems must be installed to protect both personnel and equipment against possible insulation faults.

4. Connection and synchronisation tests

Once the installation is complete, it is crucial to perform extensive tests to ensure that the genset can transfer the load correctly without interruption. These tests include:

Verifying that the ATS responds appropriately to a simulated mains failure.
Checking that the genset can take the full load of the installation without sudden variations in frequency or voltage.
Perform synchronisation tests for installations where several generators operate in parallel, ensuring that all generators work in a balanced way and without interference.

In addition, the quality of the power supplied by the generator set should be verified, ensuring that it meets the requirements of the critical equipment of the installation.

A detailed analysis of the power requirements, the proper configuration of the automatic transfer switch (ATS) and the implementation of protective measures are essential to ensure a reliable and continuous power supply.

The key to success in these installations lies in designing a system that allows critical equipment to continue operating without interruption, ensuring the safety and efficiency of the entire electrical infrastructure.