Emergency Diesel Generators: Modernization of Excitation and Control Systems

While the generator is mechanically driven by the diesel engine to transform mechanical electricity into electrical energy, a generator excitation system is required. This system builds up the required electromagnetic field to generate and regulate the necessary generator voltage for the emergency busbar. Such excitation is controlled by the Automatic Voltage Regulator (AVR). The functional interaction between the generator set and the associated mechanical auxiliary systems will be controlled by the safety and operational control supported by electrical protection.

In the case of modernization, qualification certificates and the fit-form function are of utmost importance. Essentially the spatial conditions, cabinet layout, cabling and the functional interrelationships must also be taken into account. This means that a functional upgraded EDG system can be developed from an existing system by individual solutions, in which forward-looking improvements are taken into account. It is feasible to reconcile the explicit requirements and challenges on the part of the power plant operator, e.g. the use of existing cabinets, interconnection cables and the responsible authorities for example in regard to seismic requirements.

Another key element of a successful modernization is the functional reproduction of the existing system or subsystem to be modernized. For this purpose, it is beneficial to rely, among other things, on the simulator platforms such as the ELVEES (Early Launch of Validation via an Evolving Engineering Simulator) in order to validate the design in an early project phase before commissioning.

With this simulation the functional equivalence of the revised EDG control system can be verified even before the start of the production phase. This gives the customer the certainty that there is a high degree of functional reliability with regard to commissioning, even if the EDG controls were originally supplied by another manufacturer. In addition, this system simulation can be extended as a training simulator for plant personnel for regular training.

MAEX® Cabinet

Customer involvement in all phases of a modernization project is of central importance for the joint effective handling of the projects. Safety relevant components and systems have been successfully implemented in some modernization projects, in this article we will take the following products as an examples: ADCON (Advanced Diesel CONtrol) and TXS® (TELEPERM XS) for diesel control systems and MAEX® (Modular Analogous EXcitation) for excitation systems.

Generally, the modifications briefly described in this abstract and in more detail in the following paper are only examples of the possible upgrades to a EDG System, which include:

  • Excitation Systems / Automatic Voltage Regulator
  • Instrumentation and Control
  • Electrical Protection and Synchronization
  • Monitoring, Surveillance and Reporting
  • Refurbishment (incl. Service and Life-Time Management) and studies of the complete Generator Set and its auxiliaries.

As highlighted, emergency diesel generators sets are important for any nuclear facility and can be described, due to the various different systems as a “plant in the plant”. Accordingly, all modernization design, installation and commissioning activities are based on high safety and quality standards in order to ensure the highest possible reliability of the emergency power system for the customer. The following article will explain the possibilities to exchange, respectively to implement, new excitation- and control-systems in existing configurations.

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