Our activity switchgear comprises low voltage gear, low voltage and medium voltage cabinets as well as the range of high voltage.

 

Low voltage switchgear and cabinets

  As basic modules we employ equipment of the following lines:

• LTSIST fuse isolators

• LS 4 up to LS 307 contactors

• MBS motor protective switches

• ME breakers

• Gerapid CC ultrarapid breakers

• Low voltage transformers for measuring

• ESS electronic controls

Other switchgear e. g. for railways can be found under rail equipment.

Low voltage switch cabinets

We supply standard factory assembled switch cabinets and type tested motor cabinets. The following sketch shows the standard modular cabinet of a motor protective cabinet SEV 32.

Particularly for breakers there is a preference for plug-in technique. It allows a maintenance and inspection of the breaker in service with short intervals. The plug-in breaker will be pushed into the plug holder (firm portion) across sliding rails. After plugging in the breaker the electrical connection of the main conductors is obtained through contact bridges, which are mounted on a mobile frame of isolating material elastically.

This is an example of a special application for a client:

Medium voltage switch cabinets

We supply our clients of the power generation industry equipment of maximum economy for power distribution and conversion. A key element within the networks of power suppliers is the switch equipment. With our partners in the factories we plan, design, manufacture and supply switch equipment for high, medium and low voltage. Special requirements can be met, e. g. for electric arc furnaces or ladle furnaces.

Example of an executed, triple comparted, air insulated medium voltage station with draw out breakers.

AEG vacuum switch gear 

The AEG energy block is a distribution station for inner-factory supply lines. For decentralized supplies in industries our stations can be fitted to the requirements of our clients. Such stations can be designed of various combinable cabinets:

• Medium voltage switch cabinets

• Transformer

• Low voltage switch cabinets, if required with a compensation plant  

 

AEG Energy block

Factory assembled switch unit consisting of breakers (72 kV up to 145 kV) complete with isolator and protection.

Compensation equipment for large drives, arc furnaces for the steel industry or electrolysis rectifiers

We analyse the condition of your grid regarding line perturbances by large loads, serve as consultant for ultimate consumers and supply complete compensation plants. For equipment already in operation, we offer concepts for optimization and furnish modern, digital TCR controls. Our services include planning, design, commissioning and maintenance. For the steel industry we make use of mathematical models for the electric arc furnace (AC or DC) and we are in a position to inform about the disturbances to be expected. With the help of computer-based simulations, the layout of the components of a compensation system can be determined 

During the operation of arc furnaces, outputs of up to 100 MW are being drawn from the grid. The right hand graph shows the operation cycle of approx. one hour. In order to fathom the line disturbances, the dynamic current requirement within the range of milliseconds has to be analysed. A schematic graph of the active power is shown in the left picture:

Active power	Typical effect of the reactive power

The dynamic alterations of the reactive power will produce large alterations (fluctuations) of the voltage and subsequent flicker on the grid.

This graph shows, how according to the operation of the furnace even small changes in the active power may produce large changes in the reactive power. Flickers lead to mayor disturbances in the grid. A compensation plant must control the reactive power.

Due to non-sinusoidal furnace currents, the line is disturbed by higher harmonic currents, which have to be reduced by filter circuits. Here we show the higher harmonic currents of AC - EAF - plants in relation to the basic waves:  

Grid disturbances by EAF can be summarized as follows:

An executed SVC plant for an AC EAF which compensates all three of the described disturbances:

The left part of the circuit diagram shows the EAF switch gears. We project and deliver these solution including RC damping circuits. The next picture shows an outdoor arrangement of the filter circuits consisting of reactors and capacitor banks.

 

Complete turnkey plants of arc furnaces for the production of steel together with a bar mill for rolling steel for armouring concrete will be offered together with our cooperation partners..

TCR  Products

We can offer thyristor controlled reactors (TCR) for reactive power control with digital controls in order to optimize the reactive power flow into the feeder. The according AEG products are called Semivar and Megasemi. For TCR equipment in operation we can supply new digital controls, consisting of an electronic card within the high voltage power rack and a control cubicle. The connection between the power rack of the TCR and the control cubicle is effected by light transmissions which fully insulate the control. 

Thyristor Power Rack for 33 kV	TCR cubicle

Line compensation

AEG has delivered several plants for dynamic power factor compensation in high voltage grids, e. g. eleven units for the South African Republic and another one to Nampower, formerly SWAWEK, in Namibia. A technical description of this plant is available here.

Line measurements

In connection with new installations or in case of grid disturbances of existing plants, we can execute line measurements. Our report will include the causes of the disturbance and suggest changes and compensation measures. Typical points of measurement of an EAF plant are shown in the following graph:

One of our references was the feasibility study of a large DC - EAF of 150 MVA within the west German grid system. Objective of the study was to determine wether in a specific position of the line a further EAF may be installed. After gathering the line data by ample measuring operations and use of the PC simulation, all expected grid conditions could be anticipated in a qualified way and taken care of.

 

Further information about EAF compensation:

• Dynamic reactive power compensation for an EAF at MEGASA steel plant, Spain (pdf)

• Essay on a reference project. (pdf)

• Static VAR-Compensators for stabilizing traction and transmission systems in South Africa (pdf)

 

Transformers

Within an energy supply line transformers are a center piece. We supply large transformers, line transformers and special transformers for step down and distribution stations and can offer the full range of transformers with additional components. The power range goes from e.g. 1000 kVA 20 / 0,4 kV up to 1100 MVA 525 /330 / 110 / 6,3 kV.

Cast resin transformer	Cast resin transformers in cubicles. The higher cost of a cast resin transformer is compensated by easier maintenance.

Oil cooled transformers of larger output
Transformer in a high voltage laboratory

Special Transformers

AEG Industrial Engineering projects and delivers rectifiers for electrolysis and EAF transformers. For arc furnaces, we also deliver EAF reactors. We mediate 2nd hand transformers at good prices and those out of the spare inventory of German steel producers for urgent need.

42 MVA transformer combination for rectifier plant with transducers		20 MVAr reactor with tap changer
75 / 90 MVA transformer for arc furnace		13,5 MVA LF transformer

We can supply converters for 50 cycle grids, which can create a new grid of 60 cycles, 3-phase or 16 2/3 cycle simple phase. The device with two synchronous machines shown below has an output of 100 kVA. It is used by a German machine supplier to adapt and test their products to suit the local conditions of 60 cycle grids. The frequency tolerance is +/- 1%.