Investigation Concerning the Excitation Loss of Synchronous Generators in a Stand-Alone Ship Power Plant

Abstract

The protection systems of ship generators enable them to eliminate potential failures that pose a significant threat to the safety of the crew and the use of the ship. However, due to the fact that marine classification societies do not require the protection of generators against the loss of excitation, such protection is only used sporadically. This article presents an LOE (loss of excitation) analysis of ship generators that operate in parallel. This analysis is supported by simulations and experimental research. The test results show that the positions of the operating points of each generator are interrelated, and changes in the excitation of one (damaged) generator cause automatic changes in the excitation, as well as changes in electromagnetic and energy processes, in the second (efficient) generator. An LOE in one generator causes a dangerous increase in armature currents in both generators. The results of this study prove that the lack of LOE protection at lower levels of excitement in one of the generators causes (by activating the required protection) the efficient generator to be switched off first. The main conclusion of this article is that the introduction of the use of security measures against LOE should be obligatory and legally required.

A reliable and straightforward index to avoid nuisance trip of the conventional Z‐based loss‐of‐field relay in synchronous generators

“…Hence, to protect during the faulty conditions, it is equipped with a comprehensive set of protective relays as given in Table 2. One of the major faults that may jeopardize both PPSG and power system is LOF fault [10,25]. The Z-relay is conventionally utilized to protect the PPSG during the LOF event.…”

“…The proposed LOF protection schemes in [23] and [24] exploit the load angle variation of parallel synchronous generators which are connected to a point of connection, and derivative of the both terminal voltage and power angle of the synchronous generators, respectively. On the other hand, dynamic behaviour and possible damages for the parallel synchronous generators at a point of connection during the happening of LOF failure in one generator have been completely discussed in [25].…”