АвтомобилиАстрономияБиологияГеографияДом и садДругие языкиДругоеИнформатикаИсторияКультураЛитератураЛогикаМатематикаМедицинаМеталлургияМеханикаОбразованиеОхрана трудаПедагогикаПолитикаПравоПсихологияРелигияРиторикаСоциологияСпортСтроительствоТехнологияТуризмФизикаФилософияФинансыХимияЧерчениеЭкологияЭкономикаЭлектроника
Read the text. As a measure to conserve fuel, while at the same time helping to reduce the utility’s financial investment in generating facilities (also sometimes difficult
As a measure to conserve fuel, while at the same time helping to reduce the utility’s financial investment in generating facilities (also sometimes difficult to locate because of environmental problems), generating facilities owned and operated by large consumers, may be connected directly to the utility’s transmission and distribution lines, usually as a substation-type installation. Not only must necessary protective devices be installed, but they are generally under the supervision of the utility’s coordinator or system operator. The cogenerating consumers sell their excess energy availability in the form of electricity to the utility; in some states, this sale is mandated by law.
Strict control of such installations is necessary as they may present a hazard to people working on the associated transmission and distribution lines. Necessary protective devices must be installed and the unit coordinated and controlled by the utility. Cogeneration may present a hazard to workers performing work on the line they may believe de-energized. Multiple grounds should be placed on the line before work is begun.
PARALLELING THE SYSTEMS
Paralleling the consumer’s generation facilities with those of the utility requires that additional protection equipment be installed at the cogenerator’s facilities. The principal features of this additional protection include:
1. Automatic synchronizing of the generator output with the utility;
2. Relaying to prevent the closing of the circuit breaker to the utility system until the cogenerator’s generator is opened, for protection of that generator;
3. Relaying to open the circuit breaker to the utility system on loss of power in the utility system;
4. Relaying to open the circuit breaker to the utility system on a ground fault on the utility system;
5. Relaying to control the cogenerator’s generator circuit breaker to provide generator overcurrent protection, phase current balance protection, reverse power protection, under and over-frequency protection, and under and overvoltage protection;
6. Control of engine governor equipment for speed, generator phase match, and generator load.
A smaller version of cogeneration, known as distributed generation, was developed to be connected to the distribution systems at strategic points. These mainly consisted of small units, generally driven by small gas turbines, but may include wind, solar, fuel cell, and other experimental units; these may be both utility and consumer owned. These units, and some cogeneration units, are not usually competitive with utility owned larger units that have the advantage of scale.
Some cogeneration and distributed generation units may impact negatively on the safety of operations. Although standards for the selection, installation, and maintenance of equipment to connect and disconnect these units from the system to which they supply electric energy are furnished the consumer by the utility, these standards are not always followed, particularly those related to maintenance. This constitutes a hazard to persons who may be working on the systems; believing them to be deenergized, they may be the victims of an improper, unannounced, connection, energizing the systems to which they are connected.
Electronic developments that have made e-mail (and the internet) inexpensive and universal means of communication have also made practical the remote reading of consumer’s meters. Periodic inquiry automatically sent to each consumer identifies their meter and records the dial consumption and other data, transmitting it to the computer center where it may be automatically processed, producing the bill sent to the consumer.
In some cases, usually commercial and industrial consumers, where it is desired to hold down their demands by arranging their loads not to coincide, and where practical to be scheduled for off peak hours (usually evening and early morning hours), the same means of communication is used to operate relays and switches to accomplish this purpose, often employing the same meter reading facilities.
Дата добавления: 2014-11-13; просмотров: 13; Нарушение авторских прав