Owing to existing 11kV switchgear at Leeds City Station reaching the end of its life span, a solution was required for the seamless renewal of the switchgear, whilst maintaining supplies to an operational train station. The former location of the existing 11kV substation was below ground in an area known as the ‘Dark Arches’. The train station was built on a set of vaulted arches with an area occupying distribution substations.

Logistically the location of this existing substation was unsuitable, therefore a purpose built substation was constructed at platform level, containing both Northern Powergrid and Network Rail equipment in separate sides of the building.

Two parallel 11kV feeders were taken directly from Northern Powergrid’s Whitehall Road primary substation. The approximate route length was 0.25 miles. Two parallel circuits then fed the Network Rail FKI Eclipse switchgear.

Each of the six Network Rail 11kV circuits supplied six 11,000/433V ground mounted transformers. These transformers were resupplied via new 11kV cabling. IUS managed all the critical power outages to deliver the works whilst trains continued to operate.

The work involved carrying out a survey at the substation location to ascertain if the site is suitable for automation. The survey considered the existing 11kV switchgear installed on site; network design required by NPg and signal strength tests for connectivity onto the secure communication network. The survey identifies the automation equipment to be installed and if any civils work is required.

Civil works were completed on this site, which allowed cable connections to be installed to the existing switchgear and new RTU telecontrol equipment. The new RTU was installed on a frame with umbilical cables, connecting the new actuators, which are fitted to the 11kV switches. The design incorporates fault path indicators, which are automated and wired into the RTU. These indicate back to control if a fault occurs. A power supply for the RTU is connected to the Low Voltage feeder pillar within the substation compound, which is monitored by the RTU and control centre.

Commissioning of the site is carried out by the IUS Senior Authorised Person (SAP). Final connections were made on site, with all local operational tests carried out. Once satisfied that the installation was operationally ready the SAP contacted the control desk engineer and carried out any network reconfigurations required under a system outage, to allow remote operation. Remote testing was accomplished by the control desk engineer and the automation equipment was transferred into operational use on the NPg network.

The work involves carrying out a detailed survey of a substation to ascertain if the site is suitable for automation. The survey considers the switchgear installed, network design required by NPg and signal strength tests for connectivity to a secure communication network. The survey would identify the automation equipment to be installed by approved remote terminal unit (RTU) installers, and later actuators to be commissioned by an IUS senior authorised person (SAP).

Site installation of the RTU was carried out following a successful site survey to identify where the unit would be wall-mounted and umbilical cables run between RTU and the switchgear already pre-installed. The design incorporates fault path indicators to be automated and wired into the RTU that indicate back to control if a fault occurs.

Commissioning of the site was carried out by an authorised SAP. Final connections were made onsite and local operational tests were carried out. Once satisfied that the installation was operationally ready the SAP would contact the control desk engineer and carry out any network reconfigurations required under a system outage to allow remote operation. Remote testing is accomplished by the control desk engineer and the Automation equipment made operational on the NPg network.

IUS deliver extensive low voltage (LV) OHL rebuild and refurbishment works, replacing NPg’s open wire network with Aerial Bundled Conductor (ABC) and changing rotten and defective poles where required. IUS also delivers LV OHL shrouding works for NPg, where protective shrouding is placed over exposed LV conductors to allow customers to have building and construction works completed in close proximity to the LV network. IUS exclusively deliver these works for NPg, managing the end-to-end process to strict customer service and guaranteed standard guidelines. In addition to these two core overhead line frameworks, IUS also deliver OHL inspection and remedial works for NPg, ensuring that their high-risk sites meet the necessary ESQCR standards required. IUS also deliver OHL earth tests and earth mat replacement works.

IUS is the sole deliverer of GM Automation works. On this framework, IUS instals actuators and Remote Telecontrol Units (RTU’s) in to existing NPg secondary substations. Once commissioned, these sites become automated, meaning that NPg’s Network Control Center can operate their switchgear remotely, improving restoration and response times for their customers in the event of network faults or damages. In addition, IUS also delivers GM HV substation maintenance and Fault Path Indicator (FPI) replacement works for NPg. Delivering this service, ensures that their HV network is kept up to standard and will operate as necessary when worked-upon or in the event of a fault or damage.

To deliver the above frameworks, IUS has an extensive direct team of Project Managers, Project Coordinators, Planners, Supervisors, SAP’s, AP’s, Fitters, Linesmen and Jointers. All of these staff are fully authorised to work and operate on NPg’s LV and HV overhead and underground electrical networks. They are all centrally managed, which assists with a consistent approach including efficient programming.

IUS provided expert support for the scheme, by designing the HV network, P28/G99 studies and reports, G99 protection study, earthing report, ground surveys & borehole analysis, heat gain calculations, construction designs and all other relevant design requirements. IUS constructed two substations inclusive of HV compounds, LV plant rooms and inverter rooms. The cable/duct installation carried out by IUS, involved excavation by conventional open cut trench, as well as horizontal directional drilling method.

IUS supplied and installed:
1x 2MVA transformer, 1x 3MVA transformer, 2x 11kV ring main units, 2x battery tripping units and relay panels. The IUS scope of service included an in depth and technical G99 protection scheme, installed in compliance with the local Distribution Network Operator, Northern Powergrid specification.

IUS provided a dedicated project team to ensure the day-to-day running of the project was carried out safely, efficiently and to a high quality standard, to the client’s satisfaction. IUS also provided our ‘in-house’ senior authorised person and technical service support throughout the project to ensure safe systems of work were implemented and maintained and equipment/protection was pre-commissioned to the highest of standards.

Initial design works were completed by IUS, which included a high voltage fault level and load flow study along with a protection and grading study. An earthing study was also completed for the new substation.

Two Schneider 11000/433V air-cooled transformers c/w close coupled HV ring main unit and LV cable box were supplied and installed within the new substation. An HV/LV earth nest was installed adjacent to the substation as per the design. An Intertrip relay control unit and associated cabling were supplied and installed within the new substation for each transformer for the electrical protection of the transformers.

Two 11kV cable circuits were supplied and installed from an existing substation integral to the main hospital building to the new substation. This consisted of cable fixed to containment within the hospital and external cable laid within an open cable trench excavated by others, at a length of 300m. LV cables were supplied and installed internally within the new substation from the two transformers to the two LV switchboards, with cable terminations at each end.

11kV cables were terminated at the new substation via the 11kV ring main units. The configuration resulted in the new substation being looped into the existing 11kV ring. The system was tested and energised by the IUS SAP.

IUS conducted detailed surveys of these secondary 11kV substations on NPg’s behalf to ascertain the requirements for the delivery of the works. The survey encompasses asbestos removal, street work notices, if generation is applicable, network transfer at low voltage, any civil adaptions, as well as liaison with the local community via letter drops for planned outages. This all takes place to ensure a problem free switchgear replacement.

Following the implementation of Safe Systems of Work by the IUS Senior Authorised Person (SAP), oil filled Yorkshire Switchgear and Circuit Breakers are removed by our electrical fitters in conjunction with the IUS HIAB driver. A new Schneider Electric RN2C Ring Main Unit (RMU) is then installed in its place. The original switchgear is returned to NPg for recycling. The IUS electrical fitters secure the new RMU in place and make the necessary connections to the existing earthing system within the substation. The transformer 11kV compound filled box is replaced with a new ‘dry box’ unit, allowing for the installation and termination of 300mm triplex cable. This cable is installed from the jointing position, outside the substation, where it is straight jointed to the existing NPg 11kV network by the IUS cable jointers.

The IUS SAP completes the work via continuity, insulation resistance and pressure testing prior to the substation equipment being energised. All subsequent test results and hand back documentation is collated and returned to NPg for their records.