The Mobile Substation-A Reliability Tool

Designing a subtransmission network based on Reliability Assessment Planning instead of the N-1 criterion enables existing assets to be fully utilized and provides for establishing new substations with only one transformer initially. Both strategies are aimed at optimizing the timing for capital investments to the stage when annual benefits exceed the annualized cost of works. To operate the network under these conditions at an adequate reliability level, distribution company Energex, Brisbane, Australia, developed the concept of supporting a number of single transformer substations, with one mobile substation. The underlying performance specification of the mobile substation is to have it in service within eight hours at any predesignated location to cope with a load-shed emergency. It should also be possible to operate in parallel with the main substation, to enable long duration on-site transformer maintenance. The Energex mobile substation has all the essential features of a single transformer substation and is capable of being connected to a 33-kV line to supply load to new customers, at short notice.

HEW Installs Gravity Flow Drain System Hamburg Electrical Works (HEW), Hamburg, Germany, has installed a gravity-flow drain system fitted with IMBIBER BEADS, which allows rainwater to pass but effectively swells and seals the leak path once contacted by organic liquids, such as gasoline, diesel, jet fuels, PCBs, methylene chloride, MEK and MIBK. These systems do not require electricity, electronic sensors and have no moving parts. HEW installed the system to protect its Altenwerder transformer substation from an accidental release of transformer oil.

Three units each containing 1200 L (317 gal) of oil are situated on a raised platform above a concrete containment pad. The problem HEW had identified was in locating a system that would allow rainwater to drain from the diked area, allowing it to maintain its capacity to contain the total 3600 L (951 gal) of oil. The system also had to be able to seal the drain in the event of a catastrophic release and prevent any of the oil from leaving the site.

Using Optical Fibers For Temperature Sensing The use of optical fibers for distributed temperature sensing is a well-established technology. Significant advances have been made in the reliability and performance of the measuring equipment, the design of cable systems and the method of incorporation of the fiber to ensure reliability and accuracy. York Sensors Ltd. worked with Olex Cables to develop a 110-kV cable with fiber-optic sensors to measure cable temperatures along a 9.2-km (5.7-mile) route as one of the new main transmission distribution feeders in Auckland, New Zealand.

Although every precaution was taken during installation to stabilize the environment, the geophysical aspects of the cable route means that the cable passes through several areas that can effect thermal rating of the cable system. Because of the highly critical nature of this circuit, optical fibers were incorporated within the cable construction, and for some areas, other fibers also are provided externally to the cable. This enables accurate data assessment and provides opportunities for further system enhancements.

In conventional temperature measurements, a sensor such as a thermocouple or platinum resistance probe is needed for each point of interest. For applications involving large areas or long distances, conventional systems become overcomplicated, unreliable and costly to maintain. A distributed sensing system is an effective alternative solution.

The expression "distributed sensing" describes a technique whereby one sensor can give data spatially distributed over thousands of individual measurement points. A single optical fiber has the ability to act as a distributed temperature sensor with potentially many thousands of individual measurement points. Current distributed temperature sensing (DTS) technology allows fiber lengths of up to 30 km (18.6 miles) in length with sampling every 2 m (6.5 ft) to be used this way. Optical-fiber sensors for power asset monitoring have significant advantages because they are totally immune to EMC interference and also can be used in hazardous areas.

A DTS system is essentially a combination of two technologies. Temperature measurements are achieved by analyzing the Raman backscatter signals caused when a laser pulse is traveling in an optical fiber. The position of each measurement point is determined by its time-of-flight from laser emission.

When DTS systems are used to monitor buried and subsea power cables, the resultant temperature profile enables cable owners to determine the size, location and potential impact on rating performance by any hot spots caused by localized environmental conditions.

Wind Turbines to Harvest More Green Power Wind power is set to make an import-ant contribution to the drive in Britain to produce 10% of its electricity from renewable sources by 2010.

Several onshore wind farms in the United Kingdom are growing, and many imaginative proposals are in the pipeline to build turbines offshore around the country's extensive coastline.

Surveys are underway to enable the builders to overcome significant construction and operational problems in deep water, hostile conditions and gale-force waves and winds.

Enormous energy potential exists, and the developers will benefit substantially from procedures and techniques already developed for other U.K. offshore activities, including the North Sea oil fields.

Most of the farms will be at least 5 km (3 miles) from land. Experts say that an area of sea roughly the size of London is all that would be needed to generate 10% of the U.K.'s electricity needs.

VA TECH Completes Contract with NGC VA TECH Reyrolle, part of the VA TECH ELIN Group, has completed its latest contract, worth more than 8 million British Pounds, with the U.K.'s National Grid Company (NGC) with the development of a new mechanically switched capacitor.

The 275-kV, 150-MVAR mechanically switched capacitor with damping network (MSCDN) features a compact, low-loss design using a High 'Q' reactor and two-leg damping resistor for sensitive open-circuit protection. Switching of the VA TECH Reyrolle circuit breaker is controlled by the new point-on-wave relay supplied by VA TECH Reyrolle's automation, control and protection division. The British Short Circuit Testing Station undertook modelling of the MSCDN for insulation coordination, and all major components were type-tested to NGC requirements during the contract program.