St Mary’s Hospital QEQM Sub Station


St Mary’s Hospital QEQM Sub Station

St Mary’s Hospital QEQM Sub Station

Playfords were engaged as the Principal Contractor in order to deliver the construction of a new HV/LV Sub-station onto the 11th floor plant room roof of the QEQM building at St Marys Hospital. Being an Acute Trauma Centre within central London the emphasis was on providing all of the required work scope with minimal effect to the day to day operation. All of the equipment to be delivered required careful planning and liaison with all key stakeholders within the hospital to prevent major disruptions to daily services.

The project’s primary objective was to provide resilience and balance to the building load against the two main supply feeders. The new substation comprised of 2no 11kV to 415V transformer units with close coupled Ring Main Units feeding a new Dual fed 2000A bus coupled LV Switchboard. The HV system was completed with remote switching facility for the Transformer Units.

Initial enabling works had to be completed to relocate air handling equipment in order to create space for the new LV Switchboard. One of the site smoke release shafts was utilised to provide a new cabling route from the basement to the 11th floor. In order to place the 2no new High Voltage transformers on to the roof space a steel support frame had to be constructed to provide a structurally sound platform for the 2 units weighing in excess of 8 tonnes. As the size and weight of the steels exceeded the site’s lift capacity a mobile tower crane was utilised in order to lift the equipment in to place.

Following the enabling works the real task of getting equipment to the 11th floor began. The LV switchboard for the new Sub-station had to be delivered in several sections so as to fit within the site’s goods lifts in order to reach the 10th floor. From there temporary boarding and protection was installed to the staircases to winch the sections to the final location on the 11th floor. Each section provided its own difficulties due to the weight and sizes required to house the equipment. The switchboard was then reconstructed to its complete design. A rigorous testing and commissioning process was completed in order to provide complete confidence in the system due to the critical nature of the services being supported. A further new LV Switchboard with generator changeover facility was supplied and installed for the main lifts within the building.

In order for the transformer units to be lifted onto the roof a 300tonne mobile crane was required for the distance of lift. The surrounding area at the base of the QEQM tower is populated with support buildings for the hospital meaning the crane could only be located 70 meters from the base of the building. Getting the crane to the lifting location required co-ordination with Transport for London and also the London Ambulance Service. The road adjacent to the hospital has a maximum weight capacity due to the Underground service being within close proximity to the surface at this location. Road closures were sought in order to allow the crane to lift across the roadway in order to locate the transformer on the new support frame.

A new HV service from the basement HV switchroom was installed. This service was installed through the existing smoke riser on a new containment system out to the roof area where the transformers had been landed. Radiating from the new LV switchboard were resilient supplies for the existing LV Distribution switchboards on the 11th and 5th floors of the building. These were compiled of Single core AWA feeders in parallel connected to a new extension section added on to the existing switchboards. In order to connect the extension cubicles a shutdown of the existing supply onto the switchboard was required. These works had to be closely co-ordinated with the Trust and completed within a strict tight time frame in order to maintain the power to critical services within the hospital. All shutdown works had to be completed out of hours and within the timescales provided within our meetings with all of the key stakeholders of the area.

A further backup supply was required down to the 5th floor Plant Room Switchboard. The current plant room is tightly packed with equipment and the required space for cabling was not available. Therefore a 1600A cast resin bus bar system was installed, again from the new 11th floor switchboard to an extension section to the existing switchboard. The route required was extremely tight and required close surveying and measurement to ensure successful integration of the new system whilst ensuring maintenance of the existing services was not compromised.

To finalise the system a fully integrated BMS system was provided to report on the current position of the newly installed equipment. This system comprised of new outstations located within close proximity to the new LV switchboards. These units have been placed on the site network for BMS and report back to the Facilities Management of the current status of the equipment.

Playfords as the principal contractor was responsible for all of the Health and Safety management, site co-ordination along with management of all the specialist sub-contractors. All modifications and new equipment required seamless integration with the old providing minimal disruption to the day to day services of the hospital. The project was completed with zero injuries/accidents.

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