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A DRUPS goal for rugby fans

Fans at Cardiff’s Principality Stadium will not have their match day enjoyment spoilt by a power cut, since we helped to install a ground breaking ‘uninterruptible’ power supply. 

The Dynamic Rotary Uninterruptible Power Supply (DRUPS) which combines a motor, giant flywheel and generator, kicks in immediately in the event of a dip or total loss of supply to make sure power is never lost at the stadium.

WPD engineers standing near energy equipmentCardiff stadium 1 (left to right): Matthew Davies, of Evans Electrical, Steve Merrick, HITEC Engineer, WPD Planner Chris Ryan, Simon Marshall, HITEC Engineer, WPD Planner Warren Fryer, Prag Mistry, HITEC Engineer, and Darren Crossman, Facilities and Safety Manager at the Principality Stadium.

How does it work?

DRUPS uses an 11kV motor connected to the WPD network to rotate an enormous flywheel, storing masses of kinetic energy. The flywheel, in turn, is connected to a large generator which produces the electricity supply for the stadium. In the event of a dip or total loss of supply, the motor is disconnected from the flywheel in milliseconds.

The flywheel then keeps the generator spinning until a diesel engine kicks in and picks up the freewheeling flywheel/ generator, thereby maintaining the stadium’s supply. All this happens within five seconds and means no power disruption is experienced at the stadium.

Restoration back to WPD’s network is carried out in reverse.

The installation came about when Chris Ryan, an 11kV Planner at Cardiff, attended a WPD stakeholders’ meeting at Cardiff City where he met Darren Crossman, Facilities Manager for the stadium.

Darren was looking for a way to secure the power supply and at the time, the venue used its own diesel generators when hosting events but had concerns about the cost of fuel and the age of the generators.

When Chris told him about an earlier project when we helped to install DRUPS for another customer, the seed was sown. 

Chris explained: “I told Darren how WPD had designed the network to allow the equipment to be connected and he went away and made enquiries about similar equipment for the stadium.

“WPD worked with the stadium to provide sufficient capacity and a connection point and analysed and issued the fault contribution.

“The stadium took the decision to invest in DRUPS because of the need to guarantee the power supply to the building. In 2011, the day before a sell-out concert, one of the two HV cables supplying the building failed, reducing the resilience and elevating the risk level. 

“By installing DRUPS, the stadium will continue to draw power from the network, but will have functionality through the machines to smooth the supply, and provide a full Uninterruptable Power Supply option for the stadium, with a seamless transfer in the unlikely event that power does fail. This will enable us to effectively guarantee event holders that we have enough resilience to protect the events that they hold at the stadium. 

The project cost £3.5 million and was completed in November 2019, allowing the equipment to be used for the first time at the Winter International rugby match. 

The installation of DRUPS means the stadium will never see a voltage ‘dip’ and that there is no risk of a power failure while hosting events.

Electrical equipmentCardiff stadium 2: The DRUPS: Powering Welsh Rugby.

Keeping the Lights on for Welsh Rugby

Darren also said: 

“As the project and environment was managed and designed by engineers, the space, building envelope and delivery schedules all ran smoothly, with WPD, installers Evans Electrical and HITEC cooperating in a seamless operation. The final delivery is a robust system that allows the stadium to reduce the risk of a power failure and generate confidence in the internal infrastructure.”

WPD engineers and electrical equipmentCardiff stadium 3: WPD Planners Chris Ryan (left) and Warren Fryer with the DRUPS.

What’s different about DRUPS?

Dynamic Rotary Uninterruptible Power Supply systems – or DRUPS – have been designed and manufactured by HITEC Power Protection for more than 50 years.  

HITEC’s uninterruptible power supply differs from most in that it is a single item to provide both the initial and long term support for the downstream load following a failure to the utility electricity supply.  

The installation at the Principality Stadium was designed following consultation of the stadium’s load, the stadium’s future aspirations and its electrical topology.  The result was to offer a parallel group of two 2100kVA rated dynamic UPS units that connect into the stadium’s electrical infrastructure immediately after the WPD intake switchboard.  This means that the entire 11kV ring at the stadium is supported from this secure power source. At the opposite end of the site ring, there is an open point to disconnect from the alternative WPD network intake; this was retained so it can be used as an alternative backup utility feed during times of maintenance.

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