DISTRIBUTION AUTOMATION - A GUEST POST BY DARYLL VALDEZ

Today's post is brought to us by our guest. He is Daryll Valdez, a student from the University of Mindanao, in the Philippines. Darryl is currently finishing his Bachelor's Degree in Electrical Engineering. 

Distribution Automation

Daryll Valdez

A Distribution Automation (DA) System enhances the efficiency and productivity of a utility. It also provides intangible benefits such as improved public image and market advantages. A utility should evaluate the benefits and costs of such a system before committing funds. The expenditure for distribution automation is economical when justified by the deferral of a capacity increase, a decrease in peak power demand, or a reduction in O&M requirements. Distribution Automation Systems have been defined by the Institute of Electrical and Electronic Engineers (IEEE) as systems that enable an electric utility to monitor, coordinate, and operate distribution components in a real-time mode from remote locations. 

The DA System is modular and may be implemented in phases to include remote monitoring and control of substation, feeder and consumer devices, and loads. The overall goals of distribution automation are to reduce costs, improve service, reliability, provide better consumer service, and enhance government relations. The successful implementation of the DA System results in deferred capital expenditures, reduced operations and maintenance expenses, improved outage response and restoration, enhanced system efficiencies, enhanced consumer satisfaction, improved data and information, positive public Image.

Fundamentally, there are three components of a system-wide distribution automation system. These include control centre-based control and monitoring systems, including distribution SCADA or distribution management systems; the data communications infrastructure and methodology required to acquire and transmit operating data to and from various network points in addition to substations; and the various distribution automation field equipment, ranging from remote terminal units to intelligent electronic devices required to measure, monitor, control and meter power flow. Taken together, expenditures for this wide range of electric power grid distribution automation activity exceed $1 billion dollars each year.

  

Distribution Automation functions can provide both benefits and challenges. Often these benefits and the challenges are closely intertwined, with the real and complete benefits not achievable until some of the challenges (including the financial challenges) have been overcome. Yet waiting for these challenges to be overcome or ameliorated often means missing out on some of the benefits – not doing anything can often be worse than doing something. Therefore the key to distribution automation is assessing the balance of benefits versus challenges, including the “lost opportunity” risks of doing nothing. 

The distribution automation functions can in general be divided into two main categories, namely customer level functions and system level functions. The customer level functions are those functions which require installation of some device with communication capability at the customers’ premises. These include load control, remote meter reading, time-of-use rates, and remote connect/disconnect the system level functions are those functions which relate to system operations. The control and communications devices for these functions are installed at different locations in the system, such as substations and feeders. These functions include fault detection and service restoration, feeder reconfiguration, voltage/var control etc. In addition to system operation type functions, digital protection of substations and feeders is considered part of distribution automation in some situations.

Reference:

http://www.scribd.com/doc/36666306/Distribution-Automation-Doc

http://www.energy.siemens.com/hq/en/automation/power-transmission-distribution/eneas/distribution-automation/

http://www.silverspringnet.com/solutions/distribution-automation/#.Ue07dqJHJJs

http://energycentral.fileburst.com/Sourcebooks/gsbk0106.pdf

TRANSMISSION LINE MATERIALS HANDLING AND STORAGE

In the unloading, handling, and storage of structures, care should be exercised so as not to damage the surface or surface coating, or deform the members. Bare wire rope or steel chains should not be used for handling without adequate protection of the surface. Structural members should not be dumped, dragged, rolled, dropped, nor used as loading or unloading skids or blocking.

 

Heavy members should not be stacked on top of lighter members. The maximum weight of material bundles should not exceed a specified weight, typically 1600–1800 kg (3500–4000 lb), to facilitate handling and unloading. Components with dissimilar finishes should not be stored over one another to minimize discoloration of the lower members.

Care should be taken to ensure proper blocking, stacking, and handling of concrete members. Refer to the structure drawings and instructions to verify correct lifting methods, replacement of support blocking, and stacking limitations.

 

It is very common for concrete poles to require a two-point pickup due to the weight and possible long lengths. Identifying the correct blocking locations is important to eliminate the potential of overstressing the member. The constructor should verify correct blocking and number of possible layers for stacking to avoid damage to concrete members lower in the stack.

 

All members should be placed on wood blocking or other suitable material to ensure that the material to be stored is not in contact with the ground. Blocking should also be used to separate layers of stacked material.

It should be noted that oak wood blocking or oil-treated timbers can bleed and stain a structure finish. Members should be supported in such a manner as to prevent bending and distortion as well as to allow water to drain from the material.

Failure to provide for proper drainage of stacked, galvanized steel components could result in the formation of “white rust.” White rust (zinc oxide) forms when two galvanized surfaces are closely nested for an extended time without adequate ventilation. Ingress of water between the surfaces forms an electrolytic cell which may, in time, erode some of the zinc layer.

 

The white rusting action will stop after exposure to air. When extended transport or storage is anticipated, either of the following two methods can be used to prevent oxide formation:

a) Spacers may be placed between the nested pieces to ensure adequate ventilation.
b) Galvanized members may be treated with a solution which will inhibit oxide formation for six months to one year.

Weathering steel fasteners, though rarely used on concrete poles, and other materials subject to deterioration should be protected from the elements during storage.

During the course of the project, the material yard should be kept relatively neat and clean and the growth of vegetation kept to a minimum. Good housekeeping minimizes damage and loss of material in the yard, facilitates material handling and periodic physical inventories, and complies with environmental considerations.

If delivery of material is made initially to the structure site for storage, care should be taken to avoid interference with foundation construction, access roads, or drainage. Truck delivery of complete structures from the manufacturer directly to the structure site can be advantageous since it eliminates at least one unloading and loading cycle.

 

However, security of material stored at a structure site is minimal and the subsequent loss of time due to missing items can result in significant construction cost increases.