Electric substation with wind turbines in the background

Independent power supplies for substations – stability for critical infrastructure

WT Energiesysteme GmbH and BENNING make substations fit for the challenges of the energy transition, in focus: Maximum safety and availability

The energy transition places new and higher demands on the stability and flexibility of the electricity grids. The increasing volatility in feed-in and consumption must not jeopardise availability. Availability is fundamental. One answer to these challenges is grid expansion – which means, not least, a massive expansion and new construction of transformer substations. These network nodes fulfil important functions for network stability. They are part of the critical infrastructure and must be available at all times. The focus is therefore on maximising safety – in operation and in the supply chain.

There are more than a thousand substations in Germany as of today. The energy transition with its decentralised power generation from solar and wind energy and the necessary grid expansion will cause this figure to rise sharply in future.*¹

WT Energiesysteme GmbH, based in Riesa, Saxony, is one of the few providers that plan and construct turnkey transformer substations on behalf of grid operators. The company has been relying on AC and DC power supplies from BENNING for more than a decade.

Transformer sub-stations are not only numerous, they are also the hubs of the electricity supply in Germany. As such, they are part of the critical infrastructure and must therefore not only be efficient to operate, but above all offer maximum availability. Even in the event of a power failure, they must remain remotely controllable – because this is vital in order to quickly put the affected network areas back into operation.
For this reason, substations are equipped with an auxiliary power supply, also known in technical jargon as a “safe busbar for auxiliary power”.

Availability as a standard

If the transformer substation fails, a connected wind or solar farm can no longer feed electricity into the grid. The electricity producer and grid operator will miss out on their compensation and suffer an economic loss. After all, the latter has to stabilise its grid with balancing energy and buy in the missing energy volumes at the exchange price.

If a substation in the energy supply grid is affected, the consequences are even more serious, as this can lead to a widespread power outage for the population and industry. Further interventions may then be necessary to stabilise the remaining grid.

Regardless of whether modular or monolithic power supply systems are used, the basic functional requirements are the same: The system must supply the high-voltage switchgear, the protection and monitoring technology and the communication technology with auxiliary power for a certain bridging time in order to keep the substation operational. Differences in the AC and DC power supply systems used result primarily from the individual requirements of the different respective applications.

TEBECHOP SE – Rectifier systems and DC converters in modular technology
TEBECHOP SE – Rectifier systems and DC converters in modular technology
Dietmar Tietz

„BENNING is a long-standing and valued partner that is characterised by very high quality, system durability and outstanding flexibility.”

Dietmar Tietz,
Owner and founder of WT Energiesysteme GmbH

Various applications, one objective

For example, substations in the field of renewable energies must ensure that wind energy or photovoltaic systems can feed electricity into the grid without disruption.
Here, WT Energiesysteme GmbH frequently uses battery-supported, modular rectifiers and inverters, which on the one hand are particularly compact and on the other hand, due to their modularity, can be designed to be very easily redundant and power-scalable. In general, these are configurations of TEBECHOP SE rectifiers, DC/DC converters and INVERTRONIC compact inverters. In addition to maximum availability, these systems are also characterised by their excellent energy efficiency. Due to their comparatively small volume and weight, these power supplies can usually be accommodated quite easily in the company building or in the control centre.

For substations in regional and transmission grids, which are considered part of the critical infrastructure, WT Energiesysteme GmbH often favours self-consumption power supplies with a different technical structure.

Rectifier-inverter system cabinet equipped with 3 inverter modules, static bypass switch and manual bypass as well as 5 rectifier modules
Rectifier-inverter system cabinet equipped with 3 inverter modules, static bypass switch and manual bypass as well as 5 rectifier modules
INVERTRONIC compact 19” subrack with electronic switching unit
INVERTRONIC compact 19” subrack with electronic switching unit

Due to the higher power required, thyristor rectifier systems from the THYROTRONIC series and monolithic INVERTRONIC inverters are used. These power supplies are installed in a system-redundant manner, i.e. in duplicate, and are characterised by their particular resilience. They are robust against environmental effects, offer a high level of electromagnetic interference immunity and, due to the nature of the system, a high level of cyber security. The latter is a requirement that has become indispensable for critical infrastructure and energy supply security.

Brief portrait of WT Energiesysteme GmbH

Energy conversion is the main focus of WT Energiesysteme GmbH, a medium-sized company based in Riesa and Dresden. According to the company, its core competence lies in the construction, maintenance and modernisation of transformer substations or grid feeds – in the 10 to 380 kV range.

The turnkey services for the realisation of a substation range from the feasibility study to the preparation of building application documents, planning, construction and commissioning.
As a market leader in the renewable energy sector, environmental conservation is always a top priority at WT Energiesysteme GmbH.

Founded in 2002, the owner-managed company’s customers include energy suppliers, operators of wind energy and solar plants, operators of electrolysers and industrial companies.

Source: https://wt-energiesysteme.de

Consistently safe

A consistently safety-optimised solution from BENNING was used for the substation that WT Energiesysteme GmbH planned and implemented for a distribution network operator in 2021/22. The system supplies the auxiliary power required to maintain operation and, along with a lead-acid battery for bridging times of two to eight hours, forms the “safe busbar” of the substation. Specifically, the following systems are involved:

  • 220 V DC auxiliary power system as a safe busbar for the high-voltage switchgear as well as the protection and monitoring technology, consisting of
    • THYROTRONIC thyristor rectifiers
    • Low-maintenance lead batteries
    • DC distribution
  • INVERTRONIC 230 V AC inverters with
    • AC distribution
  • 48 V DC self-consumption system as a safe busbar for communication and telecontrol technology, consisting of
    • THYROTRONIC thyristor rectifiers
    • Low-maintenance lead batteries
    • DC distribution

Lithium batteries could also be used instead of lead acid batteries – they have already been successfully used in BENNING solutions for several years and enable significantly longer backup times due to their higher energy density with the same space requirement.

INVERTRONIC inverter in a cabinet with open door
INVERTRONIC inverters, robust and reliable for industrial applications

Mastering challenges and growing together

“The energy transition and grid expansion will also trigger major investments in the coming years. Re-powering wind farms alone requires more and more powerful substations. The same applies to the electrification of heating systems and road transport. This opens up a growth market with the best conditions for a successful, joint future for WT Energiesysteme and BENNING. At the same time, the increasing requirements for critical infrastructure systems will have a lasting impact on the market for self-consumption systems. System suppliers will have to guarantee network operators even higher availability in the future – enabled or supported by local production resources and secure supply chains. A long product service life must go hand in hand with reliable life cycle support. BENNING is ready and able to do this – which is underpinned by the many years of experience of WT Energiesysteme.”

Michael Biesold,
Head of BENNING Branch Office East, Germany

Network operators value stability

For decades now, BENNING has been one of the leading suppliers of power supply systems for power technology. During this time, the company has installed many units in the field, which impress with their quality and durability. As a result, the products can now be found on the vendor lists of the most important power companies.

Grid operators own numerous substations and therefore have a great interest in efficient operation and a standardised technical structure. Thus, technology that is as uniform as possible, a long product life cycle and stable relationships with system suppliers are beneficial here. This is the only way to achieve comparable operating, maintenance and testing procedures, standardised documentation and simplified spare parts stocking. Thanks to its partnership with BENNING, WT Energiesysteme GmbH can also fulfil this key requirement of its customers.

THYROTRONIC rectifier with MCU 3000 built into the cabinet door
THYROTRONIC rectifier with MCU 3000 built into the cabinet door
THYROTRONIC 10” touch display
THYROTRONIC 10” touch display with intuitive user guidance, thanks to BENNING’s optimised user interface

Long-term partnership

The co-operation between BENNING and WT Energiesysteme GmbH has been stable and financially beneficial for more than ten years. During this time, the Saxon company has used BENNING solutions in more than 30 substations. They all run very reliably and also impress the network operators with their quality. Network operators have had excellent experiences with the continuous availability of BENNING Service, its short response times and the excellent, long-term stocking of spare parts – laying a first-class foundation for the successful continuation of the co-operation.

Further Information

contact: Michael Biesold
telephone: +49 172 2859286
e-mail:

*1 Source: https://netztransparenz.tennet.eu/fileadmin/user_upload/Our_Grid/Onshore_Germany/Allgemein/18-090_Broschüre_UW-V4-rgb.pdf

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