Everyone is inconvenienced when power plant equipment fails, and most importantly it affects the company’s revenues through productivity shortfalls. Steam turbines, gas turbines, axial/radial flow compressors, hydro-generators and boilers are extremely dynamic systems which need to be simulated and analyzed rigorously to avoid catastrophic failures. The NISA product line has been helping the power industry for the last two decades in analyzing a wide array of dynamic power equipment, including nuclear power.

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Hydro-generator cooling analysis


Depending upon rating and design, a hydro-generator stator core and windings may be cooled by air, oil, hydrogen or water. For direct-cooled generators, the coolant is in direct contact with the heat producing members such as the stator winding. For any generator, a failure of the cooling system can result in rapid deterioration of the stator core lamination insulation and/or stator winding conductors and insulation. A manufacturer needed to optimize the gap between fan blade-baffle and fan blade-air guide and parameterize the ventilation system of hydro generator for different blade configurations.


3.6° segment was considered for the analysis. A parametric 3-dimensional CFD analysis was carried out for different gaps and flow rates. Flow was considered steady and incompressible. It was observed that an 8-millimeter gap between fan blades and the air guide was optimum at all flow rates. Flow reversal was observed at larger gaps. This optimum cooling increased the efficiency of the generator.

Thermal analysis of buried power cables


Underground power cables carrying high-ampere current generate large amounts of heat. The metallic wires are bunched in various geometries and are enclosed inside a polymer cladding which protects them from the elements such as water, heat, corrosive materials and fire. Cable manufacturers need to determine the heat flow inside the cable so as to prevent meltdown of the cladding. Cladding meltdown results in obvious risks such as electrocution and disadvantages such as power transmission loss. When these cables are placed together in groups, the problem of cladding meltdown is compounded.


Conduction is the accepted mode of heat transfer below ground level. Two-Dimensional Thermal analysis was carried out. For this evaluation of thermal capacitance for the model was done under steady-state equilibrium conditions. The analysis was carried out for single cables and a group of cables laid together. Different conductor shapes like round and oval were considered. Temperatures at steady-state were found to be well within limits for the cases discussed.

Structural analysis of 36-inch condenser unit for nuclear application


This project was undertaken to understand the structural, thermal and seismic responses of a horizontally mounted condenser unit used for a nuclear waste treatment facility. The condenser unit was built in the northwest United States for the Department of Energy.


A finite element model of all the major components of the condenser unit was constructed using shell elements. The model consisted of the main vessel, channel shell, plenum shell and closures, heads, saddles, nozzles, tube sheet and internal baffles that support the tubes.

The assembly was subjected to nozzle loading, internal pressure due to various chambers being full or under vacuum, thermal loads and piping thermal loads as specified by the client in accordance with the ASME section VIII Division 1 guidelines.

The seismic response due to acceleration in all three directions was calculated and compared to the allowable stresses used as generally accepted practice in the nuclear industry. Fundamental frequency of vibration was calculated to meet the design requirements.

The unit conformed to the ASME Section VIII Div 1 guidelines.

Dynamic stress analysis of a control panel

During seismic activity, it is important that the control panels of a power plant do not lose their structural integrity. Dynamic stress and seismic analysis were conducted on one such control panel. The panel was qualified for installation thereafter.

Electromagnetic analysis of a DC generator

Determining magnetic vector potential and flux density distribution in a DC generator is crucial if the generator is to perform according to design and with minimum power loss. Electromagnetic analysis was conducted for a major generator manufacturer to qualify its design.

Dynamic analysis of 220-MW power plant rotor

Structural integrity of generator rotor shafts under any service condition is paramount. A major electric generator manufacturer needed a 220-MW rotor shaft qualified. Dynamic rotor analysis was conducted to determine if the shaft will survive most service conditions.