After carefully surveying the market for low voltage electrical switchgear and carrying out a rigorous competitive tendering exercise, Crown House Engineering, the main contractors for the Meadowhall development programme, chose to use products from Square D for all major functions.
In addition to the very competitive pricing and proven quality of the products offered, one other key factor had a big influence on this decision: equipment from Square D and, in some instances, other brands of Schneider Electric would cover all of the projects requirements.
This meant that Crown House Engineering would need only to work with a single supplier, which was seen as a major benefit, as it would simplify contractual and pricing issues as well as ensuring compatibility of equipment throughout the project and, if any technical problems should arise, guaranteeing that there could be no question of divided responsibilities.
The electrical systems required for the project are extensive, and include two new substations fed by the local network operating company at 11kV. For each of these substations, Schneider Electric supplied a cast resin transformer rated at 1.25MVA, accompanied by a Square D Powerstyle 3 LV switchboard. The boards use MCCBs for the incomer and for all outgoing circuits. For the more sensitive loads, the outgoing MCCBs are fitted with versatile electronic trip modules.
A major benefit of the Powerstyle 3 boards is their use of Plug-on MCCB technology, which means that additional circuits can be added easily and quickly. This is an important advantage in retail environments like Meadowhall, where flexibility is essential, but the disruption caused by modifications to the equipment must be kept to a minimum.
To enable the operators of Meadowhall Shopping Centre to accurately monitor the energy used by the new systems, the incoming sections of the switchboards are equipped with Schneider Electric Powerlogic PM800 microprocessor based power meters, while key outgoing circuits are fitted with PM700 power meters from the same range.
The PM700 meters provide comprehensive facilities for monitoring voltage, phase currents, real and reactive power, power factor and energy usage, while the PM800 units add functions for measuring total harmonic distortion of the current and voltage waveforms as well as measurement of the neutral current. The meters incorporate RS485 interfaces for connection to the shopping centres building management system (BMS), and also provide pulse outputs for kWh measurements.
The Powerstyle 3 switchboards used in the project are fault rated and, for maximum safety, they incorporate Form 4 Type 6 separation in line with BS EN 60439-1.
In order to minimise wasteful reactive power consumption by the new systems, Schneider Electric also supplied a Powerstyle automatic power factor correction panel. Built around high-performance long-life detuned capacitors, this has a total capacity of 500kVAr, switched as ten stages each of 50kVAr. This arrangement allows the power factor correction to be accurately matched with the instantaneous load under all operating conditions.
Providing connections between the LV boards and the power factor correction panel presented a second significant challenge, as the headroom above the boards for the connections was insufficient to accommodate conventional 1,250A cables and their associated cable trays. A convenient and cost effective solution was implemented by using Canalis busbar trunking which has compact dimensions, and which requires minimal space around it.
Further distribution facilities were provided by a Standard Plus QBU I Line panel board that offers an economical yet fully customised solution for the project. This board includes metering, contactors, power factor correction and an automatic changeover function for use with the sites standby generator.
For control of the shopping centres extensive lighting installations, Schneider Electric provided 20 Square D Standard Plus contactor panels fitted with a total of 126 impulse relays operated from the site BMS. The use of impulse relays gives a useful reduction in the energy consumption of the installation, as they consume power only when changing state. To make the contactor panels fast and easy to install, they are equipped with quick-release spring-loaded terminals.
Additional services supplied by Schneider Electric included the provision of site services personnel to modify the existing installations within the plant room, to enhance performance and to ensure full compatibility with the new sections of the installation.
For further information about Schneider Electric:
Connie Taylor - External Communication Executive
Schneider Electric Ltd, Stafford Park 5, Telford, Shropshire, TF3 3BL
Tel: (01952) 209 226
The Bright Consultancy Limited, 10 St Catherine's Court, Herbert Road, Solihull, West Midlands B91 3QE
Tel: (0121) 711 5000
Fax: (0121) 711 5001