The Challenge

Connecting a generator to a live electrical network requires precise matching of voltage magnitude, frequency, and phase angle between the incoming machine and the running system. An out-of-phase or out-of-frequency synchronisation event applies a sudden mechanical shock to the generator shaft and turbine equivalent in effect to a severe electrical fault, and can cause serious damage to rotor windings, coupling elements, and connected mechanical equipment. Manual synchronisation by operators is slow, requires high concentration and experience, and introduces the risk of human error at a critical moment in the starting sequence. As plant power generation systems become more complex — with multiple generators operating in parallel and faster loading demands — reliable and fast automatic synchronisation is essential for plant availability and equipment protection.

The ANDRITZ Solution

ANDRITZ supplies and commissions automatic synchronisation systems for industrial generators, ensuring each generator is safely and reliably connected to the plant electrical network or external grid. The ANDRITZ synchronisation system continuously measures the electrical conditions on both sides of the generator circuit breaker and controls the turbine governor and excitation system to bring the incoming machine into synchronism. The close command is issued automatically when all synchronism conditions are within the configured acceptance window, and is blocked if any condition falls outside safe limits.

How It Works

The synchronisation system monitors terminal voltage, system voltage, frequency difference, and phase angle difference between the generator and the live network. When a synchronisation sequence is initiated, the system adjusts governor setpoints to match frequency and adjusts AVR setpoints to match voltage between the incoming generator and the running network. The phase angle difference is continuously tracked, and when it falls within the configured closing window — with frequency difference and voltage difference also within tolerance — the close pulse is issued to the generator circuit breaker.

An out-of-step blocking function prevents the close command from being issued if the phase angle difference is changing too rapidly, ensuring closure occurs only when slip frequency is within safe limits. Configurable acceptance windows allow the synchronisation criteria to be set to match the mechanical sensitivity of the specific generator and turbine combination.

Key Benefits

Automatic synchronisation reduces the duration of each synchronisation event compared to manual methods, improving generator loading response times and plant availability. Consistent application of acceptance window limits prevents out-of-phase closure events, protecting the generator, turbine, and connected equipment from synchronisation-induced mechanical stress. Removal of manual synchronisation steps reduces the risk of operator error at a critical stage of the starting sequence. Integration with the excitation and governor systems provides coordinated control of all parameters required for synchronisation, rather than relying on independent manual adjustments.

Integration & Compatibility

ANDRITZ synchronisation systems interface directly with the generator excitation system and turbine governor to coordinate voltage and frequency matching prior to closure. Communication interfaces support integration with plant SCADA, energy management systems, and generator protection schemes for sequence interlocking and event logging. The synchronisation system is designed for compatibility with both ANDRITZ-supplied and third-party generator protection and control architectures.