II . Контроль за усвоением изученного материала.
1. Проверка знаний грамматического материала.
Ответить на вопросы по содержанию грамматического материала, стр.91-95, учебное пособие «Английский язык», Луговая А.Л., раздаточный материал.
1) Что включает в себя словообразование?
2) Что такое словопроизводство?
3) Что называется словосложением?
4) Дайте определение конверсии.
5) Какие вы знаете сокращения?
6) Приведите примеры аббревиатуры.
2. Ответить на вопросы по содержанию грамматического материала, стр. 93-96, учебник «Английский язык для технических специальностей», Голубев А.П.
1) Как образуются количественные и порядковые числительные?
2) Какие знаки употребляются при написании числительных?
3) Как обозначаются и читаются проценты?
4) Когда употребляется союз and с числительными?
5) Как произносятся номера телефонов?
6) Какие математические действия вам известны?
7) Как образуются простые и десятичные дроби?
8) Как читаются даты?
III . Изучение нового материала.
1. Прочитайте и переведите текст .
Types of damage in the power system.
Most of the damage in the EES leads to a short circuit of the phases between themselves or to the ground.
Damage to the electrical system most often occurs on the lines of networks.
In case of multi-phase short circuits, large currents flow in the damaged lines, which must be switched off by relay protection.
Single-phase faults are also a serious type of damage for the system as a whole, although not as dangerous in terms of stability and load preservation than multi-phase faults. Therefore, the installation of sufficiently fast protection against this type of damage is also necessary. Protection can act to disable three phases or only one damaged and then automatically restart it.
Single-phase faults are characterized by the appearance of symmetrical components of all sequences. Especially effective is the use for protection against short circuits on the ground components of the zero sequence (independence from operating currents, voltages, etc.)
In the case of single-phase short-circuit to earth in networks with low current to ground, only phase voltages are distorted. The triangle of phase to phase voltages remains unchanged. Therefore, normal voltages continue to be supplied to the load phases and the uninterrupted operation of consumers is not disturbed. The currents at the point of breakdown have small values and cannot quickly produce large violations.
Thus, single-phase circuits with a correctly maintained neutral earthing mode do not pose a direct danger to consumers and the network as a whole. Therefore, protection against earth fault in the considered networks is usually performed only acting on the signal.
The mode is not a dangerous type of damage and is allowed to work for two hours.
In networks with an isolated neutral, a dangerous type of damage is a double short circuit to earth. Requires immediate disconnection. It is advisable to automatically disable only one breakdown place.
Double earth faults usually occur in places with weakened insulation, mainly due to over voltages appearing in the system during single-phase earth faults.
In case of failure of a part of the phases of the circuit breakers, a phase break may occur.
The line phase gap, in contrast to short-circuit faults, may not represent an immediate danger to the system and does not require immediate elimination, however, the resulting components of currents and voltages of reverse and zero sequence may cause a number of undesirable consequences. Therefore, the phase gap in some cases would be desirable to automatically selectively eliminate.
2. Ответить на вопросы к тексту.
1. What types of power system damage do you know?
2. Are single-phase short circuits dangerous?
3. What is the line phase gap?
3. Выполнить задания для проведения дифференцированного зачета 5(7) семестра Вариант - 1