1. Ответьте на вопросы

1. What kind of Electric power supply system in a country comprises?

2. Power supplies are necessary to the operation of just about every electrical device, including desktop and laptop computers, aren't they?

3. What require certain types of current, frequency and voltage?

4. How many types of electrical current that are regulated, controlled and altered by power supplies-alternating current and direct current?

5. What include some of the unit designs?

6. Why electrical power for computers one of the most common applications for power supply manufacturers?

7. How used the voltages commonly supplied are 3.3 and 5 volts?

8. What kind of types of uninterruptible power supplies (UPS) you know?

9. For what UPS systems are perfect?

10. When UPS actually boosts the main power supply using a regulator?

2. Найдите синонимы

Attach, specific, distinct, separate, particular, exact, fix, different, every, direct, include, each, individual, involve.

Найдите антонимы

Connect, separate, exclude, nonspecific, identical, nonmetal, indirect, specific, disconnect, include, direct, different, metal, attach.

3. Переведите следующие слова и выражения на английский язык

1. Электрическая система питания.

2. Энергоблоки.

3. Линии электропередачи.

4. Электропитание.

5. Портативные модули.

6. Настольные и портативные компьютеры.

7. Телекоммуникаций.

8. Источник питания переменного тока.

9. Постоянный ток.

10. Выходное напряжение.

11. Резервный аккумулятор.

4. Переведите следующие слова и выражения на русский язык

1. Uninterruptible power supplies.

2. Electric charge.

3. Direct current.

4. Protective casing.

5. Digital numerical displays.

6. Analog visual indicators.

7. Adjustable frequency.

8. Integral heatsink.

9. Back up battery.

10. Water cooling.

11. Metal box.

12. Switching power supplies.

What is relay? Definition of protective relay

A relay is automatic device which senses an abnormal condition of electrical circuit and closes its contacts. These contacts in turns close and complete the circuit breaker trip coil circuit hence make the circuit breaker tripped for disconnecting the faulty portion of the electrical circuit from rest of the healthy circuit.

Now let’s have a discussion on some terms related to protective relay.

Pickup level of actuating signal: The value of actuating quantity (voltage or current) which is on threshold above which the relay initiates to be operated. If the value of actuating quantity is increased, the electromagnetic effect of the relay coil is increased and above a certain level of actuating quantity the moving mechanism of the relay just starts to move.

Reset level: The value of current or voltage below which a relay opens its contacts and comes in original position.

Operating Time of Relay – Just after exceeding pickup level of actuating quantity the moving mechanism (for example rotating disc) of relay starts moving and it ultimately close the relay contacts at the end of its journey. The time which elapses between the instant when actuating quantity exceeds the pickup value to the instant when the relay contacts close.

Reset time of Relay – The time which elapses between the instant when the actuating quantity becomes less than the reset value to the instant when the relay contacts returns to its normal position.

Reach of relay – A distance relay operates whenever the distance seen by the relay is less than the pre-specified impedance. The actuating impedance in the relay is the function of distance in a distance protection relay. This impedance or corresponding distance is called reach of the relay.

Power system protection relays can be categorized into different Types of relays.

Types of Relays

Types of protection relays are mainly based on their characteristic, logic, on actuating parameter and operation mechanism.

Based on operation mechanism protection relay can be categorized as Electro Magnetic relay, Static relay and Mechanical relay. Actually relay is nothing but a combination of one or more open or closed contacts. These all or some specific contacts the relay change their state when actuating parameters are applied to the relay. That means open contacts become closed and closed contacts become open. In electromagnetic relay these closing and opening of relay contacts are done by electromagnetic action of a solenoid.

In mechanical relay these closing and opening of relay contacts are done by mechanical displacement of different gear level system.

In static relay it is mainly done by semiconductor switches like thyristor. In digital relay on and off state can be referred as 1 and 0 state.

Based on Characteristic the protection relay can be categorized as

- Definite time Relays;

- Inverse time Relays with definite minimum time (IDMT);

- Instantaneous Relays;

- IDMT with inst;

- Stepped Characteristic;

- Programmed Switches;

- Voltage restraint over current relay.