Safer energy management for larger hospitals
04 May 2014
With the size and complexity of modern hospitals on the rise, it is now common practice to run 10kV supplies deeper into the building in order to reduce power distribution losses. Eaton was recently involved in an installation of this kind in The Netherlands, serving a new hospital in Zwolle.
With a floor area of 108,000 square metres, the new Isala Klinieken hospital complex in Zwolle is the largest non-academic hospital in The Netherlands. Clearly, electrical energy is critical to a number of activities in healthcare, and as hospitals continue to increase in size it is important to minimise low-voltage distribution losses. As a consequence it is now becoming commonplace to run the 10kV supply deeper into the building.
In collaboration with Eaton, the Dutch installation consortium, Installatie Combinatie Isala (ICI) is using Eaton MV switchgear in combination with a Power System Automation (PSA) scheme to help ensure a secure electrical energy supply for the complex. Key priorities for the installation team were to ensure a consistent supply voltage level and total reliability of power distribution to all the wings of the building.
ICI's scheme uses two 10kV ring circuits that allows the supply to come from either the mains incomer or emergency power generators, according to prevailing conditions. One ring circuit supplies the 'preferential' power supply system and the other the 'non-preferential' supply, with any power outages in the preferential system being absorbed by emergency power generators.
The advantage of using open ring circuits is that faulty sections can be isolated, allowing other sections to remain functional and bottlenecks or Single Points of Failure (SPOF) to be eliminated. The two incoming 10kV cables are also set a distance apart to avoid potential problems from excavation work.
At the heart of the installation is Eaton’s Power Xpert FMX switchgear panel, an IEC single busbar, and solid- and air-insulated (SF6-free) MV switchgear for voltages up to 24kV. The FMX units are set up to provide a non-preferential and a preferential part for each room and are connected using a specially made wall bushing with a coupling at the centre.
“We chose the FMX because of its innovative vacuum technology which allows for frequent and high levels of switching”, says ICI engineer, Gert Jan van Tolij. “The reasonable price and environmentally friendly aspect of the technology were also significant benefits. Even more important was the high power level it offers and the extremely compact design with slim panels.”
In the event of a power outage, four emergency power generators are available to supply 1MVA each to the preferential busbar of the Power Xpert FMX. These generators are connected with a step-up dry transformer monitored by positive temperature coefficient (PTC) elements with a PTC relay.
The installation distinguishes between three levels: the operation of two, three or all four emergency power generators. If a power failure lasts longer than 0.5 seconds, the emergency power generators kick in and emergency power is supplied within 15 seconds. Brief dips of less than 0.5 seconds are picked up at a local level by Uninterruptible Power Supplies.
The Central Control Panel acts as the brain of the electrical installation. This was also supplied by Eaton on ICI’s instruction, as the latter deemed it a logical step to choose Eaton technology for the control tasks, as Gert Jan explains:
“The central control goes with the 10kV input, so it has to work in perfect harmony with all the hardware. We would prefer not to have this managed by a third party. Eaton is familiar with the installation and knows best how to control it.”
Redundancy has also been implemented within the control unit, which is equipped with two PLCs that communicate directly with each other and monitor each other’s functions. The PSA comprises a Central Control Unit (CCU) that manages all necessary steps should a power failure occur anywhere in the system.
There are double feeds for the CCU that come from two 110Vdc Eaton units in each of the rooms in the power building. These units ensure that all the control, protection and switching actions are, and remain, available.
The power distribution system also includes equipment installed on the roof of the building, with eight Magnefix Ring Main Units (RMU) and transformers supplied by Eaton fitted in a dedicated 10kV room. Magnefix was the system of choice as the switchgear does not require a raised floor. It also allows for a reversal of the cable panels and enables the supply to be fed from the top.
The RMUs are set up in pairs in each wing of the building, one unit for the preferential and one for the non-preferential system. The power that is supplied from either the mains or the emergency power system via the Power Xpert FMX to the Magnefix is then transformed from 10kV to 400V.
All the equipment used by Isala Klinieken meets international IEC standards and is available in the UK and Ireland for electrical power management applications at 11kV and 20kV.
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