Primary network

Where higher reliability is desired than from radial or loop circuits the radial primary circuits are tied together into a network. The network is supplied from a number of transformers or substations supplied in turn by subtransmission and transmission lines. Circuit breakers between the transformers and grid act as network protectors to protect the network from faults on the incoming high voltage lines. The high cost of operating such a system in providing for load growth and the high potential hazard involved with the enormous fault currents handled by the circuit breakers have led to their replacement by low voltage secondary ‘spot’ networks, though some primary networks may still be in operation.

8. Match the item in column A with the item in column B

   Column A	Column B
   Circuit breakers between transformers and grid …	the radial primary circuits are tied together.
   Where higher reliability is desired …	have led to the replacement radial loop circuits to secondary networks.
   The high cost of operating such a system …	act as a network protectors.

9. Make up the plan to the text.

10. Explain what the primary circuits count on?

Unit 12 (part 2). Secondary circuits

1. Words to remember.

be affected – находиться под влиянием

associated supply – совместное снабжение

be justified – быть подтвержденным

be programmed – быть запрограммированным

to reverse – возвращаться

2. Read the text.

Secondary circuits

The secondary circuits supplied through transformers from the primary systems are also affected by faults on their associated primary supply, whether from a radial, closed or open loop circuit.

Where additional expense may be justified to achieve a higher degree of reliability, the secondary circuits of the several primary circuits may be connected together to form a network, so that service to any consumer will not be affected when a primary circuit, or any part of it, may become deenergized for whatever reason. The secondary network is connected through switches, called network protectors, through transformers connected to their primary group supply circuits. These switches, or protectors, are programmed to open when the current flowing through them reverses direction. This, so that current flow from the network may not supply fault current to a fault on any of the primary supply circuits.

The low voltage secondary network is also employed in serving large individual loads requiring a high degree of reliability; these are known as spot networks.

3. Find English equivalents of the following sentences in the text.

1. На вторичные цепи влияют поломки на соответствующих первичных цепях.

2. Если по какой-либо причине будет обесточена первичная цепь, то обслуживание любого потребителя не будет прервано.

3. Для обслуживания большого числа индивидуальных нагрузок, требующих высокой степени надежности, используются вторичные сети низкого напряжения.

4. Speak about secondary circuits using the following words.

Are affected by, weather, reliability, deenergized, protectors, individual loads.