Steps to buy a generator set

Buying a generator set requires proper electrical sizing to find the right fit. Considering factors such as current and future power needs, the elements the equipment must incorporate, legal regulations to comply with, or the location where it will be installed are crucial for the correct choice.

Each energy project poses a different challenge and different requirements to meet, electrical sizing is becoming increasingly complex.

In the past, sizing calculations were based on the arithmetic sum of powers and with power factor correction factors depending on the number of motors in the installation, the type of consumption was simpler, it was closer to pure resistive or there were consumptions that could be so in themselves. Today this is unthinkable, the electrical devices connected to an installation have a very high load of electronic components, which facilitates the use of these devices, makes energy generation more complex with the appearance of harmonics and inductive and capacitive consumptions.

That is why the sales team at GENESAL ENERGY receives continuous technical training and close support from the engineering department to offer the client an optimal solution.

If an undersized generator set is acquired, from the end user's point of view, there will be a lack of power at certain times.

The generator set would be asked for power for which it is not designed, which can cause unacceptable voltage/frequency drops and overheating that could affect the equipment's insulators. The increase in the working temperature of the engine will cause greater wear on internal components.

If an oversized generator set is acquired, the end user will have higher fuel consumption for the loads. If the set continuously works at low load, mechanical problems arise because the generator set never reaches the optimal operating temperature, affecting combustion and, therefore, also the intake and anti-pollution systems, causing smoke in the exhaust and expelling suspended particles and unburned substances that, in the long run, can cause a loss of power and carbonization of components in the engine's intake and exhaust system.

To avoid both cases, the engine should work on average around 70% of its nominal power, avoiding working long periods below 30% of its capacity.

Calculation of the dimension of generator sets

The initial and most basic step is to define which equipment will be connected to the generator set and know the power delivery required for the project. In other words, knowing what the sum of the power of all the electrical devices that will need to be powered is, applying simultaneity rates where possible and always attending to the client's requirements and needs.

But a simple mathematical operation will not give us enough information. There are other factors that we must consider, as they affect the result of that calculation. These relate to both technical aspects and usage and environmental factors.

It is necessary to have very meticulous control of the large loads existing in the installation, electric motors, lighting by discharge lamps or LED, are complex electrical consumptions to supply since they have transients that can cause peak consumptions of fractions of a second that poorly designed equipment may not be able to supply.

Sizing the generator set

To size the generator set and decide its configuration, the engineering team will base it on the electrical, mechanical, or civil engineering project. This defines:

• Power: the necessary power and types of existing and/or future loads, simultaneities, load steps, etc.
• Functionalities: the elements that the equipment must incorporate (manual or automatic start, operation in parallel with other equipment or with the public grid, soundproofing, auxiliary fuel tanks, heaters, etc.).
• Regulations: the legal regulations to comply with (electrical, noise, gas and particle emissions, traffic regulations in case of mobile groups).
• Location: the place where the equipment will be installed (under roof, outdoors, elevation above sea level, dusty environments, etc.).

Once the GENESAL ENERGY engineering team has this information, they will begin developing their project to meet your needs, thus adapting it not only to the technical requirements but also to the use the generator set will receive.

• Constant load 24h/365 days: A generator sized for a COP (Continuous Power) application according to ISO8528 should be selected. These generators can operate an unlimited number of hours at 100% of their nominal power. These generators are suitable for systems in permanent parallel with the grid, such as in cogeneration equipment or plants that require continuous power supply to heating resistors for long periods.
• Continuous loads for a maximum of 500h/year: A generator sized for an LTP (Long Term Power) application should be selected. These generators can operate up to 500h per year at 100% of their nominal power. These units are suitable when it is necessary to cover a specific power peak in parallel with the grid.
• Variable loads 24h/365 days: For this application, a generator with a PRP (Prime Power) application should be selected. The generator can operate an unlimited number of hours per year with the possibility of overloading it by up to 10% for 1 hour out of every 12h of operation. The average load over a 24h period will not exceed 70% of the PRP power declared by the generator. This is the most common type of generator for practically any industrial or commercial application, as most of the loads applied to the generator are variable, meaning they connect and disconnect based on the needs of the installation.
• Variable loads a maximum of 200h/year: A generator sized for an STP (Standby Power) application should be selected. These generators can operate with variable loads a maximum of 200h/year, and should not exceed an average load over 24h of 70% of the declared STP power. This type of generator is common for emergency generators for any industrial or commercial application.
• Data center loads: A generator sized for a DCC (DataCenter Continuous) power should be selected. In data centers that comply with Tier III or Tier IV according to Uptime Institute, it is only possible to install generators that have no operating limits. According to ISO8528, this would only be possible with COP generators, but for a data center, where there are variable loads, it means installing an oversized generator. To avoid this, generators designed according to DCC rating allow for unlimited hours of operation with variable loads like those found in data centers.

GENESAL ENERGY generator sets always indicate in the data sheets the declared power for PRP application and for STP application, as these are the two most common applications.