# Calculations

**Security in switchgear rooms**

For the security of switchgears, stations and rooms it is nowadays mandatory to reduce the effect of pressure of arcing faults or to avoid them. For this purpose we use pressure calculation software based on a pressure network which is successfully established for many years. These calculations show an excellent correlation of pressure profiles and amplitude with measurements performed. The pressure calculation is necessary for buildings, medium voltage substations and industrial distribution systems to ensure maximum safety in case of arcs.For factory assembled stations (IEC62271-202) and factory-built high-voltage switchgear up to 52kV (IEC62271-200) the internal arc calculation is essential during the development in terms of pressure progression and burning of the housing. The pressure calculation is done statically and dynamically, for line surges. It considers the proportion of the energy of the arcing fault in form of a transfer coefficient which depends on gas pressure (density), operating pressure and others causing the mechanical pressure effects.

The diagram shows a pressure network for a switchgear with pressure relief channel.

Arc power for different compartments of a C-GIS

Mittlerer Druckverlauf für Ausleitkanäle unterschiedlicher Querschnitte

Medium pressure distribution for pressure relief channels with different cross-sections.

We perform pressure calculations as a service for you. The documentation regarding the calculation concerns the arc power, the resulting pressure values and time characteristics, including a complete analysis optionally worked out, FEM-Calculation of stressed components, including a constructive evaluation.Optionally, a report in German or English language will created.

B&E develops effective arc fault limiter for control rooms and equipment, which reduce both the thermal and the pressure effects significantly. We advise you on structurally upgrading activities and create you a concept for the protection against arc faults.

**Multiphysical Calculations**

Prototyping and development tests are essential steps in the new development of high-voltage switchgear and components. Timely and target oriented calculations of physical processes help significantly to reduce time and costs. The examination of heating, expansion, mechanical stress and deformation is possible in a calculation.

**Dielectric Optimization**

The calculation of the maximum field strength is an important point for evaluating the dielectric strength of solids and the insulating capacity of fluids (SF6, air, nitrogen, silicon oil e.g.). Also in the medium voltage we prefer to design with a weakly inhomogeneous field, so that a volume reduction for the switchgear can be achieved.Our evaluations of the results of partial discharge problems, frequency withstand voltage and lightning impulse voltage is related to the previously performed calculations.

**Current Density **

The calculation of the current density is used to increase material efficiency of connections and contacts. We take into account physical effects such as the frequency-dependent current suppression.

Mechanical Strength

Yield strength, tensile strength, deformation of components under stress occurs in almost all components of switchgear. Switch poles of circuit breakers are subjected to tensile strain and bending, GIS-housings to pressure (e.g. evacuation, operating pressure and arc).

With the necessary material information, a FEM analysis and our experience, we can determine the limits and the probability of failure.From this results the technological processes are optimized, the volume of used materials minimized and assembly sequences changed.

Typical examples are the optimization of laser-welded assemblies, systems of mechanically moved parts and the APG resin production.

The picture shows the deformation of an internal wall without reinforcements in an metal-cladair-insulated switchgear panel 12kV 50kA 1250A for a circuit breaker compartment in case of an arc fault.