Case Study - How to design an Islanded Power Station to Supply Construction Power, Which Can Be Integrated into the Permanent Power System at a Later Date.
During the construction phase of a remote project, there is a need for construction power. Often this is supplied by distributed, single unit generators connected directly to the load. The generators are usually on hire for the duration of the construction
phase. The number of generators will vary from time to time as the construction progresses. The cost of the generators includes the hiring the generators plus the operating costs for fuel, connection and transport,
After construction and hand-over to operations, there is a need for permanent power. This may be an islanded power station. The island power station may have been part of the construction activity.
Sometimes it is more cost effective to build a power station which may firstly be used to provide construction power and later to provide permanent power.
The implementation of such a scheme requires the design of the power station to be fully integrated with the needs of both construction and permanent plant. It may require scheduling changes, which could impact the whole project.
There can be significant challenges in the design of the electrical power system. The power system for construction and permanent plant may need to be separated on completion of the project. Similarly, generation units may have to be either added or deleted for permanent power. The operating philosophy for permanent power may be different to that for construction power. The station control system for construction may be local and that for permanent power may be remote SCADA. The hand-over to permanent power may be required before construction is completed. The operator for construction may not be the same for permanent power. The fuel system for
construction power may be different to that for permanent power.
There are many factors which need to be carefully considered for a successful outcome with a single power station, used for both construction and permanent power. BESST have the experience and expertise to provide electrical engineering and design services for construction power stations and permanent plant, off-grid power stations.
A hazardous area is an area in which an explosive atmosphere may be present, or is normally present. Hazardous areas commonly occur in mines, process plants, oil facilities and gas facilities.
The hazard may be caused by liquids, vapours, mists, gases and dusts. These could occur as a raw material, or as part of a manufacturing process, or during the transport, handling and storage of the material. Hazards can occur in many situations. For example, the photograph shown was taken in a local supermarket, showing the
flammable warning on a spray can of olive oil.
Unfortunately, there are many examples of what can happen when if there is an explosion, such as a massive explosion at Pemex oil refinery in Mexico.
Another example is the video of the fertilizer plant explosion in Waco, Texas, on 17 April 2013. The bodies of 12 people were recovered. The enormous explosion demolished surrounding neighbourhoods for blocks and left more about 200 other people injured.
In order to minimise the risk of an explosion, special precautions are required for the design and installation of electrical systems in hazardous areas. The Australian Wiring Rules (AS/NZS 3000:2007 with amendments) has a section for hazardous areas (explosive gas or combustible dusts). The standard defines a hazardous area and the particular requirements to the selection of electrical equipment and its installation to ensure safe use in areas with an explosive atmosphere. There are additional standards that are referenced as applicable to hazardous areas.
BESST provides EEHA (Electrical Equipment in Hazardous Areas) hazardous area classification and design to national units of competency for the following:
· Classify Hazardous Area – Gas Atmospheres
· Classify Hazardous Area – Dust Atmospheres
· Plan Electrical Installations for Hazardous Areas – Gas Atmospheres
· Plan Electrical Installations for Hazardous Areas – Dust Atmospheres
· Design Explosion-Protected Electrical Systems and Installations – Gas Atmospheres
· Design Explosion-Protected Electrical Systems and Installations – Dust Atmospheres
Arc flash is the exposure of the skin to incident energy from an electrical arc. The severity of the exposure can be quantified in terms of thermal energy per unit area of exposure.
In the USA, the NFPA 70E-12, Electrical Safety in the Workplace, the focus is on a burn injury from arc flash being reduced and to be survivable. The energy threshold used in most standards to determine survivable is the energy which would result in a second-degree burn - 1.2 Cal/cm2.
A second-degree burn is identified as:
· Deep partial thickness
· Extends into deep (reticular) dermis
· Appears yellow or white, less blanching, may be blistering
· Being a fairly dry texture
· Causing pressure or discomfort
· Having a healing time of 3-8 weeks
· Prognosis of scarring and contractures (may require excision and skin grafting
[Refer Wikipedia – Burn]
The risk associated with an electrical arc flash can be managed through a variety of methods of risk assessment and risk control. Ideally, the risk should be as low as reasonably practicable (ALARP). For a person suffering an arc flash at work, there is a cost associated with a second-degree burn, to the person, to the employer and to the facility
The level of possible arc flash exposure can be identified during the design phase of a project and action taken to minimise the incident energy of a potential arc flash. For an existing installation, an audit of the electrical system can expose areas of excessive arc flash incident energy and remedial action can be proposed. Arc flash labels are fitted to electrical equipment to clearly identify the arc-flash boundary, working distance, incident energy and the required protective clothing (PPE).
Is it compulsory to provide arc flash studies and arc flash warning labels? In the USA the arc flash standard was introduced as NFPT 70 and it is mandatory because of occupational health and safety (OHS) regulations. NFPT 70 covers both low voltage and medium voltage installations.
In Australia, there is the standard AS/NZS 4836:2011, safe working on or near low-voltage electrical installations and equipment. The standard covers the principles of safe working practices and the recommended procedures for safe working practices. It includes recommendations to manage many hazards associated with electricity, including
arc flash. This standard is referenced in legislation. It applies to all persons carrying out work on or near low-voltage electrical installations and equipment.
BESST provides arc flash services both for the design phase of a project and for audits of existing installations.
The most cost effective method of reducing arc flash energy can be identified and the measures required for implementation can be advised. BESST provide arc flash labels for each item of electrical equipment. The arc flash study is based on IEEE 1584 2002-2004 and is in compliance with NFPA 70E 2000, 2004, & 2009.
An Electrical Utility Industry in Transition - Centralised, Large Scale, Grid Generation to Micro-Grids?
A webinar was held on 11 December 2013 – Electricity Market Mechanisms for Rewarding Flexibility. The webinar was conducted by the Business Review and sponsored by
The rapid expansion of intermittent renewables are depressing wholesale prices across Europe. Due to this and other reasons, running hours for gas-fired generation are at a historic low. Gas turbines are being mothballed in Europe almost weekly, and utilities are shifting their strategy away from gas. Decision makers seem to agree that more as well as new flexible capacity is needed for integrating renewables, while at the same time utilities are finding it hard to justify keeping even their existing flexible units operational in current electricity markets. Thankfully, there are several potential ways of modifying the market structures to tackle this issue.
With the penetration of wind and PV energy reaching 30-40% in Germany, there is a drop in the demand from centralised grid generation of the same order. This is causing financial pressure for generators to remain viable and technical issues for the continuity of supply of electricity to users.
Regarding financial pressures, a similar pattern is emerging in Queensland. The electricity generation capacity is around 14,000 MW but the most recent peak demand in January 2014 was 8,280 MW.
This is causing financial pressure for generating companies. For example, Stanwell Power Corporation is closing the low-emission, gas-fired Swanbank E power station west of Brisbane for 3 years because it is cheaper to produce electricity from the coal-fired Tarong power station. Brisbane Times, 5 February 2014, Swanbank power station to close for three years.
This is in addition to job cuts that were announced last year due to “unsustainable losses”. Courier Mail, 10 July 2014, Stanwell Corporation to cut around 58 jobs in Queensland as power glut leads to "unsustainable losses”.
It follows huge losses by the Queensland State Government’s electricity-generating companies of almost $ 1.1 billion in the 2010-11 financial year and write-downs of hundreds of millions of dollars.
Courier Mail, 1 October 2011, CS Energy, Stanwell Power and Tarong Energy write down value by combined $ 1.1 billion due to proposed carbon tax.
The effect on consumers has been a seemingly never-ending spiral of price rises for electricity.
Regarding the technical issue of the continuity of supply, the PV and wind energy sources are not controllable sources, sometimes producing too much electricity and sometimes producing too little, causing intermittency.
The issue of intermittency may be addressed using a number of options. One option is using new generation models such as micro grids and distributed generation.
For example, a suburban area network may comprise 3,000 houses. If the average off-peak demand for each house is 1 kW and the peak demand is 1.5 kW, the total average electrical demand is 3 MW (off-peak) and 4.5 MW (peak).
Assuming the penetration of PV is 30%, the PV nominal capacity is 1 MW. Therefore, if the area was operating as a “micro grid” it would import a nominal power from the grid as follows:
- Day time, off peak, nominal PV generation: - 2 MW
- Day time, peak, no PV generation: - 4.5 MW
- Night time, off-peak: - 2 MW
A number of solutions can be identified on how to support the grid and maintain operation of the micro grid. For example, one solution may be to provide generation capacity within the micro grid. A nominal capacity of 2.5 MW would limit the load on the grid to 2 MW and eliminate peak loading.
BESST is able to provide scalable, benchmark solutions for the design and development of the electrical power and control systems required for the micro-grid. This includes concept design, FEED studies, detailed design and commissioning.