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Built to last for a power plant’s lifetime

BENNING contracted to supply UPS systems to one of the UK's largest and most energy-efficient fired coal power stations.

Easy module swap due to hot plug technology and automatic module configuration

Uniper's power station in Ratcliffe-on-Soar is a 2,000MW coal-fired power station, which can meet the electricity needs of approximately two million homes. Commissioned in 1970, the power station has four coal-fired boilers made by Babcock & Wilcox, each of which drives a 500-megawatt (MW) Parsons generator set.

In addition to the plant's enormous capacity, it is also the first power station in the UK to be fitted with Selective Catalytic Reduction technology (SCR), which reduces the emissions of nitrogen oxides through the injection of ammonia directly into the flue gas.

In April 2016, Ratcliffe Power Station's lead electrical engineer contacted BENNING to enquire about a small inverter system. When visiting the site, it became clear that the plant's UPS systems for ‘Critical Supplies’ required an upgrade.
BENNING was identified as the right partner for this project because of its specialisation in providing robust, industrial-scale modular power solutions. 

In contrast to power solutions for the commercial sector, BENNING's industrial grade solutions achieve a prolonged lifetime and higher availability by over-specifying components and developing hardware that is designed to withstand the harsh conditions faced in the environment of industrial-scale applications such as dust, temperature chan­ges or water ingress. Ratcliffe Power Station appointed BENNING for two contracts and some additional systems:

  • The first contract was to replace the old station and coal battery charger systems / rectifiers which support critical power plant systems. The new systems were to include additional capacity and be relocated within the building.
  • The second contract was to replace the existing site instrument, computer, measuring, recording and regulating device UPS / inverter/converter systems with a set of modular UPS systems.
  • In addition, BENNING won orders to replace multiple smaller emergency lighting systems with modular UPS system designs. For both large projects, BENNING proposed new redundant systems, incorporating efficient and digitally controlled solutions, which provide a high level of availability, whilst minimising risk and cost in maintaining the equipment.
UPS subsystem for instrumentation
UPS subsystem for instrumentation

Project one - 'critical supplies' upgrade

It is crucial for power plants to have back up power systems in place that can start and control their operation if the mains supply is interrupted. 

To achieve this most effectively, BENNING designed two rectifier/charger systems for the site’s critical supplies. Accordingly, two 1000A, 240VDC station charger systems (A+B) were supplied and installed in the power station and one 400A, 240VDC charger system is installed in the coal plant. The coal plant charger/rectifier, which feeds batteries within the coal plant area of the power station, has a future capability of 400A at 240VAC, which was de-rated at delivery to 200A to match the incoming AC supply.  All three systems were designed to use an identical voltage so that they can be coupled if needed during maintenance or in emergency situations, increasing the power plant's high availability level. 

The two 1000A, 240VDC station chargers provide the power station with a fully redundant N+N system (A+B), which ensures a high level of availability. The systems, which needed to be positioned in a new location within the building, were not only designed but also manufactured, installed and commissioned by BENNING. One challenge was to correctly position the systems over the cable tunnels, however, the team took all client specifics into consideration, ensuring that the systems were perfectly levelled, aligned and positioned over the cable tunnels in their new location.

Project two - UPS & inverter systems

Following the success of the first "critical supplies" upgrade program contract, BENNING was asked to take part in the bidding process for replacing 13 separate UPS/inverter systems across the entire Ratcliffe-on-Soar site. Most systems were at the end of their life and an appropriate, future-proof replacement needed to be found. During survey visits with Uniper's team, BENNING were able to assess the exact requirements of the site and gain an appreciation of the level of criticality involved. Closely working with the lead engineer throughout, BENNING recommen­ded a modular approach for the new systems. This modular approach is well-established in the commercial sector, when looking at smaller scale data centre UPS systems, for example. However, its advantages have not found their way into industrial environments yet, as these environments require longer UPS lifetimes, greater installed system complexity, and rugged system hardware.
BENNING is the only manufacturer to meet these unique industrial requirements whilst providing a highly functional modular system architecture. Rather than a monobloc system, the UPS is built out of smaller units, or modules, which can simply be added or removed from the larger UPS chassis unit, which has no single point of failure.

ENERTRONIC modular SE 40 kW module, developed for the most demanding requirements

Key benefits of BENNING's suggested modular system are:

  • Increased availability: Units can be easily added or replaced, as none represent a single point of failure
  • Reduced MTTR: It only takes a few minutes to remove or swap modules, all of which can be done whilst the overall system is online and running
  • Simple spare holding: Due to their small size, UPS modules can be easily lifted and carried by one person, while spare modules can be stored to facilitate quick replacements
  • Modules interchangeable with other systems: Modules can be swapped between systems and spare parts can be kept to a minimum due to their interchangeability
  • Expandability and flexibility: The UPS system can grow with power requirements, as modules can simply be added to achieve a higher capacity, giving operators a great deal of flexibility
  • UPS black start function allows station to initiate a recovery procedure following an extensive loss of supply

According to Uniper’s Lead Engineer Christopher Howe, “BENNING were the only industrial supplier of such modular technology, and this coupled with the flexibility of a modular system, led to the decision to employ BENNING as the partner of choice to deliver this project."

According to the loads these supported, these systems were:

  • 1 x Station Instrument UPS 30kVA N+N system with N+1 on each side and dual battery strings
  • 1 x Coal Plant UPS 20kVA N+1 using station battery set 
  • 1 x FDG UPS 7.5kVA n+1 using dual battery strings
  • 1 x Communications UPS 7.5kVA N+1 using three battery strings
  • 1 x IT infrastructure UPS 25kVA N+1 using single battery strings
  • 4 x Instrumentation UPS 20kVA using station battery sets
  • 4 x Computer UPS 20kVA using battery sets

The fully installed and commissioned station UPS system comprises a dual redundant ENERTRONIC modular SE UPS range, which is a modular, transformerless three-phase output UPS system based on IGBT/MOSFET semiconductor and DSP processor technology. It has been designed to provide the highest level of protected power availability for critical loads within the utilities, oil, gas, transport and other high-demand industries. As previously introduced, the truly modular design means that each ENERTRONIC module contains its own rectifier, inverter, controller and static bypass switch, ensuring that there is no single point of failure within the UPS system. This, coupled with a modular, hot-swappable design ensures a high system MTBF and low MTTR. A manual bypass switch is provided for maintenance purposes. The provided system also included 2x100% rated 12-15 Year design life VRLA batteries.

Low input harmonic distortion and high efficiency, even at partial load, significantly reduce running costs and environmental impact, while modular design allows for rapid repair and pay as you grow system scalability through the installation of additional parallel connected modules.

BENNING completed the positioning, installation and SAT/commissioning of all of the remaining UPS systems within the completion target of November 2017.

Further Information

author/contact: Dirk Meyer 
telephone: +49 2871 93 261

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