Глаголы-связки

1. Глаголы-связки не имеют смыслового значения, они несут на себе грамматическую нагрузку (являются показателями времени, лица, числа) и служат для соединения подлежащего со смысловой частью сказуемого, которая может быть выражена существительным, прилагательным, причастием, инфинитивом, герундием и числительным. Приведем примеры только с одним, самым распространенным в научном тексте глаголом-связкой to be, который перед инфинитивом переводится как «заключаться в том, чтобы», в остальных случаях - «быть», «являться», «составлять»:

The computer language is also a means of communication.

Компьютерный язык также является средством общения.

He was liberal in his views.

Он был либеральным в своих взглядах.

This demonstration of power systems is more convincing.

Этот показ энергосистем является более убедительным.

The number of Power engineering conference participants is twenty-five.

Число участников конференции по электротехнике составляет двадцать пять человек.

2. К глаголам-связкам также относятся такие глаголы, как to become становиться, to remain оставаться, например:

The problem of reliable power transmission became unsoluble.

Проблема надежной электропередачи стала неразрешимой.

3. Ряд глаголов может выступать как в роли смысловых, так и в роли глаголов-связок.

Не is a student. Он — студент.

Но:

Не is in the electrical laboratory.

Он находится в лаборатории электротехники.

The problem got complicated. Задача усложнилась.

Ho:

He got continuous current. Он получил постоянный ток.

The solution grew red. Раствор стал красным.

Ho:

I turned the page. Я перевернул страницу.

The problem looks easy. Задача выглядит (кажется) простой.

Ho:

We looked at the problem of power transmission from another point of view.

Мы посмотрели на эту проблему передачи электроэнергии с другой точки зрения.

Запомните разницу в значении глаголов, которые способны выступать в роли как смысловых, так и связочных:

Смысловое значение глагола-связки:

to be - находиться, быть, являться

to get - получать, становиться

to grow - расти, становиться

to turn - поворачивать становиться

to look - смотреть (at — на), выглядеть

Задание 1. Переведите текст, обращая особое внимание на глагольные формы. Выделите сказуемое.

Safety

In TN, an insulation fault is very likely to lead to a high short-circuit current that will trigger an overcurrent circuit-breaker or fuse and disconnect the L conductors. With TT systems, the earth fault loop impedance can be too high to do this, or too high to do it quickly, so an RCD (or formerly ELCB) is usually employed. The provision of a Residual-current device (RCD) or ELCB to ensure safe disconnection makes these installations EEBAD (Earthed Equipotential Bonding and Automatic Disconnection). Earlier TT installations may lack this important safety feature, allowing the CPC (Circuit Protective Conductor) to become energized for extended periods under fault conditions, which is a real danger.

In TN-S and TT systems (and in TN-C-S beyond the point of the split), a residual-current device can be used as an additional protection. In the absence of any insulation fault in the consumer device, the equation I _L1+ I _L2+ I _L3+ I _N = 0 holds, and an RCD can disconnect the supply as soon as this sum reaches a threshold (typically 10-500 mA). An insulation fault between either L or N and PE will trigger an RCD with high probability.

In IT and TN-C networks, residual current devices are far less likely to detect an insulation fault. In a TN-C system, they would also be very vulnerable to unwanted triggering from contact between earth conductors of circuits on different RCDs or with real ground, thus making their use impracticable. Also, RCDs usually isolate the neutral core. Since it is unsafe to do this in a TN-C system, RCDs on TN-C should be wired to only interrupt the live conductor.

In single-ended single-phase systems where the Earth and neutral are combined (TN-C, and the part of TN-C-S systems which uses a combined neutral and earth core), if there is a contact problem in the PEN conductor, then all parts of the earthing system beyond the break will rise to the potential of the L conductor. In an unbalanced multi-phase system, the potential of the earthing system will move towards that of the most loaded live conductor. Such a rise in the potential of the neutral beyond the break is known as a neutral inversion. Therefore, TN-C connections must not go across plug/socket connections or flexible cables, where there is a higher probability of contact problems than with fixed wiring. There is also a risk if a cable is damaged, which can be mitigated by the use of concentric cable construction and multiple earth electrodes. Due to the (small) risks of the lost neutral raising 'earthed' metal work to a dangerous potential, coupled with the increased shock risk from proximity to good contact with true earth, the use of TN-C-S supplies is banned in the UK for caravan sites and shore supply to boats, and strongly discouraged for use on farms and outdoor building sites, and in such cases it is recommended to make all outdoor wiring TT with RCD and a separate earth electrode.

In IT systems, a single insulation fault is unlikely to cause dangerous currents to flow through a human body in contact with earth, because no low-impedance circuit exists for such a current to flow. However, a first insulation fault can effectively turn an IT system into a TN system, and then a second insulation fault can lead to dangerous body currents. Worse, in a multi-phase system, if one of the live conductors made contact with earth, it would cause the other phase cores to rise to the phase-phase voltage relative to earth rather than the phase-neutral voltage. IT systems also experience larger transient overvoltage than other systems.

In TN-C and TN-C-S systems, any connection between the combined neutral-and-earth core and the body of the earth could end up carrying significant current under normal conditions, and could carry even more under a broken neutral situation. Therefore, main equipotential bonding conductors must be sized with this in mind; use of TN-C-S is inadvisable in situations such as petrol stations, where there is a combination of lots of buried metalwork and explosive gases.