The ship power station is the heart of modern ships. Electric generator is the most important equipment in the ship power station and protecting the dynamo from being damaged is the important guarantee for safe trip of the ship. Regarding various abnormal operation and malfunctions of the dynamo of ships, it is necessary to install relevant protective relaying equipment. The abnormal conditions of marine generator mainly include overload, external short circuit, undervoltage, abnormal frequency and reverse power.
1. Overload protection of marine generator
In the running process of power station, if the generator capacity cannot satisfy the laden requirement or the parallel running generator sets have uneven laden distribution, generator overload will happen. Long time of current overload will overheat the generator and cause insulation aging and damage and long time of power overload will shorten the service life of the prime motor and damage the spare parts.
As for overload protection, classification society stipulates that the overload protection when the excess current is in the range of 10%~50% should make the generator disconnector drop out with the delay of within 2min. The overload protection of the generator is mainly undertaken by the overcurrent release of the frame-type automatic air circuit breaker.
2. External short circuit protection of marine generator
The short-circuit current produced in short circuit has huge damage to the equipment and operation of the electric system, for this reason, the protective equipment is required to correctly, reliably, quickly and selectively disconnect the point of failure. The external short circuit protection of marine generator is mainly undertaken by the overcurrent release of the frame-type automatic air circuit breaker.
3. Undervoltage protection of marine generator
When the voltage regulator is out of order or the external short trouble of the generator is not eliminated or there is serious underfrequency, the voltage may decrease. The undervoltage protection of marine generator is also mainly undertaken by the overcurrent release of the frame-type automatic air circuit breaker.
4. Reverse power protection of marine generator
The reverse power operation of the marine generator refers to that the dynamo does not output active power, but absorbs active power from the power grid. The reverse power protection of marine generator is mainly undertaken by the reverse power relay.