Nuclear safety systems

Safety Diesel Generators

The safety diesel generators are responsible for the electric supply of the critical auxiliary consumers (e.g.: reactor cooling circulating pumps) of the power plant in case of failure at the internal mains.

The original diesel generator regulation-control systems installed between 1982-1987 were obsolete and aged.
The hydraulic governor’s poor static speed accuracy and slow dynamic response didn’t meet the latest requirement for the electric supply.
The reliability of the original control was strongly decreasing and the spare part resupply became difficult.

The replacement of the original governor-control system was realized with elements from Woodward Governor (USA):

Uninterrupted Power Supplies (UPS)

In Paks Nuclear Power Plant the originally installed rotating uninterrupted power supplies (DC motor – AC alternator) had became used up and obsolete for the end of the 80’s.

Due to this the power plant made a decision to replace them. Our company as the official representative of AVK/SEG Group of Companies offered the application of the so called STARO-ETA UPS system for this purpose.

The STAtic – ROtational UPS with high efficiency (ETA) were able to alloy the most favorable features of the two traditional UPS systems: the high short-circuit capacity and nice voltage waveform of the rotational UPS and the short reaction time as well as the fast switch over to battery operation of the static semiconductor UPS.


ETA operation
Stabilizes voltage at suitable mains supply
STARO operation
Voltage and frequency stabilization at local island operation
BATT operation
Stable supply based on battery power in case of mains failure
BYPASS operation
Bypass line on internal failure

Considering the technical advantages and impressive references the power plant decided the replacement of a unit for one year trial operation.

During the design of the prototype equipment AVK/SEG completely adapted the special local features of the NPP (e.g. 220 Vdc battery voltage), so that the installation and the commissioning of the new UPS proved to be very simple.
The reference unit was installed in 1992. After the trial period the NPP decided the replacement of all old units that was managed during the next three years. 18 UPS were supplied in total with power output of 100 kVA of each.

In Bohunice Nuclear Power Plant, Slovakia the preparation and design work had started parallel. Higher rated units (150 kVA) were supplied there according to their specific requirements.