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Hour Of Power

High-tech controls increase demands on power supply.

As textile machinery has become more sophisticated over the past two decades, power supply companies are under pressure to deliver more constant and clean power. Due to integrated electronics and microprocessors, which regulate and control individual processes and machine functions, textile machinery is quite sensitive to power fluctuations. Sensors, step-motors, variable speed drives, and high-tech electronic controls have replaced simple mechanical contact switches, electric motors and circuit breakers. In the past, it was practically impossible to adjust and regulate production lines manually for optimum settings, but today that is easily done with the highest precision using sophisticated microprocessors and linked machine controls. However, each electronic device needs to be fed with constant and correct voltage and plenty of reserve power for simultaneous machinery startup.Challenges For SuppliersTo explore the challenges that power supply companies are facing, ATI spoke with various suppliers for the textile industry in the Southeast. In general, the power supply companies have to deal with three different situations:

  • a textile mill that replaces older machinery with new machinery;
  • a textile mill that extends its capacity with new machinery; and
  • a new greenfield plant.
The following information, while somewhat general in scope, represents approximately 90 percent of all requirements for textile mills.Timing Is EverythingAccording to the power companies, coordination of timing with the customer is a top priority. This begins with the planning phase, when power suppliers request to be involved in order to get the lead time required to order the hardware. During the construction phase of an expansion, especially a greenfield plant, additional power will be required, which may exceed the spare capacity of existing hardware for power supply. However, most crucial is the timing and coordination of delivering the hardware in time during the startup phase of new machinery. Therefore, for the power supplier, it is very important to understand as early as possible what the customer requirements will be in reference to the type of load for each individual machine, the total number of machines to be installed and the specific power quality demanded by the original machine manufacturer. The requirements extend into further questions such as what provisions will be needed for the infrastructure of the new production facility in reference to chilling, air compression, lighting and any other electrical requirement influenced by changes in the mill.
The ideal case for the power company would be for the textile manufacturer to have an early list ready that shows the total kilowatts or power consumption rating for the plant. At the same time, it is important that the customer provide an estimated utilization schedule of the newly installed equipment so that the power supply company may calculate the most cost-effective use of the hardware.If, for example, the overall efficiency of the installed equipment will be 75 percent, based on the mills average production schedule, then the power company will adjust the specification of its hardware cost for the power consumption expected during everyday operation. The goal for the power company is to provide the customer with sufficient power without installing expensive, oversized hardware.Practical ApplicationOnce the understanding with the customer of the load characteristics of the new equipment is established, then the power company can make the physical changes for power delivery to the plant. In practical terms, this may entail transformer change-outs. If the mill makes a switchgear change, this may even involve different connection points. No change mentioned above should present a problem as long as the customer has sufficient space for the new electrical power supply hardware. However, power suppliers are sometimes faced with the problem of equipment installed 20 to 30 years ago, where the surrounding space of a transformer has been taken up by parking space, a gas tank or other obstruction that does not allow expansion. The mills need to be aware that any expansion of textile equipment may also require larger power supply equipment. Also, new safety rules and regulations may require more space around the equipment than before. Even if the same-sized transformer is installed, the actual space required for fencing and safety distance between it and other objects may be greater. Whenever changes are made, the customer must understand that, for safety reasons, the clearance between transformer and fences must be reevaluated. In addition, it is very important that any clearance between ground activity and conductors must be sufficient to avoid any contact points. The evaluation is based on the peak load to be expected for the power company. The mill has some responsibility to calculate what an expansion of production capacity will mean with respect to power requirements. It is vital for the power company to understand the details of the requirements for the new installation to coordinate with the timeline of its customer. Inventory management is key to success for the power company. A staggered startup of new machinery can be helpful in gaining the time required to order specific transformers, station breakers, etc. The lead times for receiving transformation equipment after ordering has been pushed out over the past years; it now takes about 1 1/2 years (for some custom-built equipment) from the date of placing the order to delivery. Therefore, the power company tries to coordinate the project schedule as closely as possible to facilitate the needs of inventory management with the production requirements of the textile mill.Power To GoTo explain power conveying in simplest terms, the power is produced at the power plant or generating station. The voltage is stepped up to a transmission level that allows power to be carried over greater distances. For example, Duke Powers transmission system covers an area of 20,000 square miles, which is reflected in approximately 13,000 miles of transmission lines in the central and western portions of North and South Carolina. From the transmission system, the power can be delivered directly to the substations of the customer, from which the plant receives the required power. For residential and city power supply, there is a distribution system that serves the populated areas. The general design layout should always satisfy the peak requirements of all customers. Increased power demand caused by newly installed machinery usually reflects changes in power supply hardware closer to the individual mill, and mainly at the customer-substation. This is the step-down point of the transmission voltage to the customer delivery voltage. Todays modern power supply systems are designed to meet the requirements of high-tech textile machinery and deliver consistent voltage and the highest-grade power. Most major power suppliers have taken measures to minimize any negative side effects that relate to long-distance, high-voltage power transmission, and to the step-down transformation of delivery power. Also, several technologies have been developed for very sensitive types of power requirements that allow customers to install equipment directly in the plant. However, each individual application will dictate which specific technology will be required. Achievement of the highest grade of power for the particular application is a cooperative effort between the power supplier and the textile plant. During the planning phase, it is critical to evaluate the individual responsibility of both parties and to prepare together for successful startup and operation.When Power FailsA typical power outage is often related to adverse weather, a fallen tree on a power line, etc., and does not usually last much longer than a few minutes. These outages, however, can cause hours of outage time. When restarting machinery after such a power failure, the power suppliers recommend operators check all equipment for any possible damage and required resets and then start each individual machine in a staggered startup. In general, the restart should first focus on the air-conditioning system, or the ventilation system, to establish production-friendly conditions again. It is strongly recommended that the start of automated machinery be staggered because, theoretically, it could automatically restart at the moment power is restored. Power suppliers suggest a 30-45-60-minutes restart phase if at all possible. Otherwise, the in-rush, or instantaneous peak power demand after a power outage, can overload the power suppliers circuits and lead once again to a power failure.Visit Power Suppliers On The InternetCarolina PowerandLight Co. www.cplc.comDuke Power www.dukepower.com/inyourbusiness/commercialGeorgia Power www.southernco.com/site/gapowerPiedmont Power www.pmpa.comTennessee Municipal Electric Power Association (TMEPA) www.tmepa.org

August 2000