Tower Bridge – High Voltage Electrical Infrastructure upgrade

The project works comprise upgrading the High Voltage (HV) and Low Voltage (LV) electrical
infrastructure and increasing its power resilience (i.e. the secondary source of power in the event of a power failure). The existing secondary supply can only power bridge lifts at half speed, subject to complex adjustments to driving machinery, and essential functions.

In addition, the secondary power supply is used for river signal and navigation lights, public and safety lighting, and more critically, the security CCTV camera provision across the bridge.
This effects the ability to complete bridge lifts as covered under the Corporation of London (Tower Bridge) Act 1885. Therefore, it is imperative that the backup power supply provides secure power resilience to these functions.

The Bridge is currently at risk of power failure due to the existing electrical network and
switchgear being over 40 years old. There is currently no reliable source of back up supply due to the age and condition of the infrastructure and parts to carry out repairs to the switchgear are difficult to source as they are no longer readily available.

The project works therefore comprise of replacing the HV & LV switchgear and transformers,
segregating HV & LV services (via switch room on new mezzanine floor), replacement of existing HV cables, removing existing generator, provision of a new secondary HV supply North Shore and provide generator plug in connection point, together with existing South Shore HV supply replacement.

The basis of the design is to provide a solution that meets the needs outlined above whilst
ensuring minimal disruption to bridge operations and visitor attraction. It also caters for replacing existing equipment that is obsolete or nearing its end of life.

Summary of requirements:

– Replace HV & LV switchgear and transformers.
– Segregate HV & LV services (via switch room on new mezzanine floor).
– Replacement of existing HV cables.
– Removal of existing generator on North Shore, facilitating new UKPN Plant Area.
– Provision of new secondary HV supply.
– Provision of new generator plug in connection point.
– Migration of existing supplies onto new essential and non-essential LV panels.
– Removal and reinstatement of Ship stairs and associated services to facilitate an adequate access route for new plant installation.
– New gas suppression and extract systems.
– Switch Room Ventilation & Cooling.
– SCADA controls.
– Construction of a new mezzanine floor.
– Extensive structural and construction works to support the electrical infrastructure works – Circa. 30% of contract value.

Furthermore, the successful contractor will be responsible for:
– Managing works on public highway.
– Managing applications to Transport for London.
– Management of and liaising with UKPN for the coordination of works.
– Managing Bridge closures.
– The discharge of planning and heritage conditions.
– Phasing of the works.
– Out of hours working.