Skip to main content

IMPLEMENTATION OF DISTRIBUTION AUTOMATION

The implementation of “distribution automation” within the continental U.S. is as diverse and numerous as the utilities themselves. Particular strategies of implementation utilized by various utilities have depended heavily on environmental variables such as size of the utility, urbanization, and available communication paths. The current level of interest in distribution automation is the result of:

• The maturation of technologies within the past 10 years in the areas of communication and RTUs/ PLCs.
• Increased performance in host servers for the same or lower cost; lower cost of memory.
• The threat of deregulation and competition as a catalyst to automate.
• Strategic benefits to be derived (e.g., potential of reduced labor costs, better planning from better information, optimizing of capital expenditures, reduced outage time, increased customer satisfaction).

While not meant to be all-inclusive, this section on distribution automation attempts to provide some dimension to the various alternatives available to the utility engineer. The focus will be on providing insight on the elements of automation that should be included in a scalable and extensible system. The approach will be to describe the elements of a “typical” distribution automation system in a simple manner, offering practical observations as required.

For the electric utility, justification for automating the distribution system, while being highly desirable, was not readily attainable based on a cost/benefit ratio due to the size of the distribution infrastructure and cost of communication circuits. Still there have been tactical applications deployed on parts of distribution systems that were enough to keep the dream alive. The development of the PC (based on the Intel architecture) and VME systems (based on the Motorola architecture) provided the first low cost SCADA master systems that were sized appropriately for the small co-ops and municipality utilities.

New SCADA vendors then entered the market targeting solutions for small to medium-sized utilities. Eventually the SCADA vendors who had been providing transmission SCADA took notice of the distribution market. These vendors provided host architectures based on VAX/VMS (and later Alpha/Open- VMS) platforms and on UNIX platforms from IBM and Hewlett-Packard. These systems were required for the large distribution utility (100,000–250,000 point ranges). These systems often resided on company owned LANs with communication front-end processors and user interface attached either locally on the same LAN or across a WAN.

Comments

Popular posts from this blog

ADVANTAGES AND DISADVANTAGES OF CORONA

Corona has many advantages and disadvantages. In the correct design of a high voltage overhead line, a balance should be struck between the advantages and disadvantages. ADVANTAGES (i) Due to corona formation, the air surrounding the conductor becomes conducting and hence virtual diameter of the conductor is increased. The increased diameter reduces the electrostatic stresses between the conductors. (ii) Corona reduces the effects of transients produced by surges. DIS-ADVANTAGES (i) Corona is accompanied by a loss of energy. This affects the transmission efficiency of the line. (ii) Ozone is produced by corona and may cause corrosion of the conductor due to chemical action. (iii) The current drawn by the line due to corona is non-sinusoidal and hence non-sinusoidal voltage drop occurs in the line. This may cause inductive interference with neighboring communication lines.

ADVANTAGES OF PER UNIT SYSTEM

PER UNIT SYSTEM The per-unit system expressed the voltages, currents, powers, impedances, and other electrical quantities basis by the equation: Quantity per unit (pu) = Actual value/ Base value of quantity ADVANTAGES OF PER UNIT SYSTEM While performing calculations, referring quantities from one side of the transformer to the other side serious errors may be committed. This can be avoided by using per unit system. Voltages, currents and impedances expressed in per unit do not change when they are referred from one side of transformer to the other side. This is a great advantage. Per unit impedances of electrical equipment of similar type usually lie within a narrow range, when the equipment ratings are used as base values. Transformer connections do not affect the per unit values. Manufacturers usually specify the impedances of machines and transformers in per unit or percent of name plate ratings. Transformers can be replaced by their equivalent series impedances. ...

ABSOLUTE AND SECONDARY INSTRUMENTS

The various electrical instruments may, in a very broad sense, be divided into (i) Absolute Instruments (ii) Secondary Instruments. Absolute Instruments are those which give the value of the quantity to be measured, in terms of the constants of the instrument and their deflection only. No previous calibration or comparison is necessary in their case. The example of such an instrument is tangent galvanometer, which gives the value of current, in terms of the tangent of deflection produced by the current, the radius and number of turns of wire used and the horizontal component of earth’s field.  Secondary Instruments  are those, in which the value of electrical quantity to be measured can be determined from the deflection of the instruments, only when they have been pre-calibrated by comparison with an absolute instrument. Without calibration, the deflection of such instruments is meaningless. It is the secondary instruments, which are most generally used in ev...