ELECTRICAL DISTRIBUTION CIRCUITS | TYPES OF CIRCUITS | LCETED

ELECTRICAL DISTRIBUTION CIRCUITS

For the distribution of electricity from the consumer control unit to other points in an ordinary building, the supply is divided into the following three separate Types of Circuits:

 

1. Lighting circuit of low capacity – 6 amp

 

2. Power circuit through ring circuit

 

3. Fixed appliance (or individual) circuits (Each appliance is Separately wired to the consumer control unit.)

 

Generally, red wires are used for the live wire. The neutral is black or blue and earth wires are green or striped green and yellow. Brief descriptions of each of these circuits are given below. A phase changer may also be incorporated into the circuit

 

Lighting Circuit

What is Lighting Circuit?

A separate circuit is usually provided for the general lighting of the building. One of the following two systems is commonly used for this purpose:

• Loop-in system

• Joint-box system

 

Loop-in system.

What is Loop-in system?

In a loop-in system, each loop is rated as 6 amp. A live phase cable runs from a 6 amp fuse (or miniature circuit breaker) from the control board to the live terminals of the first lighting point or ceiling rose. From this lighting point, the cable loops out to the next rose and so on till all the lighting points are linked together.

 

Similarly, the neutral and the earth lines are also run. Another length of the same cable runs from each rose to the corresponding switch controlling the light. This is shown in Fig. below In important places (such as living rooms), more than one lighting circuit (from different phases) should be used so that in the event of a phase failure, some lighting will be in working condition, without the use of a phase danger.

 

Joint-box system.

What is a Joint-box system?

In a joint-box system for a lighting circuit, the wires run to a series of joint boxes instead of direct to the roses, with separate joint boxes for each light switch. The joint box is circular in shape and has four terminals—live L, neutral N, earth E and switch return wire to the switch (SW).

Lighting circuit wiring diagram of Loop in method (N = Neutral, L = Live, E = Earth): 1. The consumer control unit, 2. Ceiling rose, 3. One-way switch, 4. Lamp, 5. Two-way switch.

 

Power Circuit or Ring Circuit

What is Power Circuit or Ring Circuit?

For small appliances such as refrigerators, mixers, etc., we use a ring circuit. The ring circuit consists of a 30 amp fuse or MCB, protected looped live line as well as neutral and earth lines. These are looped from one socket to the other as shown in Fig. below. Usually, a separate outlet is provided for every 100 m2 area of the floor space. No more than two outlets are taken for a single spur as shown in Fig. below.

 

The current is drawn by a three-pin plug from the socket. We should note that as 30 amp fuse or MCB of this system is of a high rating, it is advisable to give high protection to each individual appliance. This can be done by supplying current through a 13 amp fused plug or fused spur box (i.e. through a fuse of lower rating).

Power circuit wiring diagram (ring main wiring): 1. Consumer control unit, 2. 15 amp socket outlets in ring men, 3. 15 amp spur socket outlet.

 

Fixed Appliance Circuits

What is Fixed Appliance Circuits?

Appliances such as air-conditioners, electric cookers, etc. consume heavy currents for their work. For these appliances, we have to provide separate circuits from the control unit to the appliance. These circuits are called fixed appliance circuits. Usually, separate switch-off devices are also provided near the equipment to isolate them from the circuit for safety and repairs. Live, neutral and earth lines are connected to the outlet.

 

FAQ

What is an electrical distribution system?

The part of the power system that distributes electricity for local use is called the distribution system. Typically, a distribution system is a power system between a transmission system and a substation supplied by a consumer meter.