A generator converts mechanical energy into electrical energy. Whether in a hydropower plant, a wind turbine, an emergency power unit, or a conventional power plant – without generators, there is no electricity generation. Closely linked to this are unit and step-up transformers, which raise the generated voltage to grid level. Generator technology is continuously evolving – modern permanent-magnet synchronous generators and doubly-fed induction generators are shaping new wind and hydropower plants.
How does a generator work?
A generator uses the principle of electromagnetic induction: a rotating winding moves relative to a magnetic field, thereby inducing a voltage. Depending on the design, a distinction is made between synchronous generators – common in large power plants – and induction (asynchronous) generators, which are frequently used in wind turbines. The generated voltage is raised to grid level via a unit transformer.
Key Characteristics at a Glance
- Synchronous or induction design depending on the application
- Ratings from a few kW to over 1 GW per unit
- Voltage levels typically ranging from 400 V to 27 kV
- Connection to unit transformers for voltage step-up
- Protection via generator relays and differential protection
- Permanent-magnet synchronous generators without slip rings
- Doubly-fed induction generators used in many wind turbines
Frequently Asked Questions
What role do unit transformers play?
Unit (step-up) transformers convert the comparatively low generator voltage to the high voltage levels of the transmission grid. They must continuously transmit particularly high power levels with high efficiency.
What is the difference between an emergency generator and a power plant generator?
Emergency generators are usually much smaller, diesel-powered, and designed for short-term load balancing or island operation. Power plant generators, on the other hand, operate permanently in parallel with the grid and deliver large amounts of both active and reactive power.
How is a generator protected against internal faults?
Protection is provided by differential protection, stator earth-fault protection, rotor earth-fault protection, under-excitation protection, and thermal protection. In modern protection devices, these functions are usually combined, enabling fast, selective tripping in the event of a fault – before major damage can occur.
What requirements apply to generators operating in parallel?
Before connecting, voltage, frequency, phase position, and rotation direction must match. Synchronizing devices automate this process. When several generators operate in parallel, active and reactive power must be deliberately shared between them – modern controllers handle this task automatically according to predefined strategies.
Are you planning a generation plant and looking for suitable unit transformers? We develop solutions precisely tailored to your requirements – get in touch with us.