LV generator protection - engineering site - Schneider Electric

In shortReplacement Set or Safety Set.The same functions are required:ensure continuity of the electricalsupply should the main source fail.However, a Safety Set must satisfyfar more exacting operatingrequirements in order to guaranteesafety of the electrical installation atall costs.The Generator Set andElectrical Distribution1.2.Quality EnergyTo supply sensitive loads (computer, etc.), a quality energy must be implementedthat is free from breaking and with a perfectly regulated voltage.A number of systems can be used to ensure break-free switching. Thesesystems are implemented in the LV system:b reversible synchronous machinethe Set generator is permanently connected to the mains supply:v when operating in the Main function, it operates as a synchronous motor drivingits inertia flywheelv when operating in the Replacement function. When the Mains supply fails, thesynchronous machine, driven by its flywheel, starts to operate as a generator.The Set’s thermal motor starts (off-load) and automatically connects as soon as itreaches its speed at the generator.When the Main source is restored, the Set is then synchronised on the Mainsource, the Main source circuit-breaker closes and the thermal motor isdisengaged and stopped.E79357EElectrical utility networkSNmainsourceSynchronousmachine(compensatoror generator)MagneticcouplingFlywheelThermalmotorNCNCNon-backed upfeedersBacked upfeedersNC: normally closed.NO: normally open.Figure 5: Block diagram of a reversible synchronous machine.This type of solution is not very common as it is relatively expensive toimplement.b generator Set associated with a UPSthe generator set ensures continuity of the electrical supply. Electrical supplyinvolves breaking (from a few minutes to a few seconds). Energy Quality(elimination of outages/brownouts and waveform) is obtained by anUninterruptible Power Supply (UPS) - equipped with a battery- which continuallysupplies sensitive loads in LV.This type of solution is advantageous as it provides sensitive loads with qualityenergy during use on a Main or Replacement source.8