Street Light Wiring Diagram with Timer (Auto/Manual Operation)

Hi, in this article, we are going to see the Street Light Wiring Diagram. We will learn how to make the connection of a street lighting system with a timer so we can operate it manually as well as automatically whatever we want. Streetlights are important for keeping roads, neighborhoods, and public spaces safe and visible at night. The automatic street lighting system allows street lights to turn on and off automatically at specific times using a timer. It also includes a manual switch so that the lights can be controlled by hand if needed. The old street lighting systems used mechanical and analog timers but in modern days most street lighting systems are designed with digital timers. So, here also we have used a digital timer.

Wiring Diagram

Here, you can see the wiring diagram of street light.

Components Used

• Street Lights
• Single Pole MCBs for each Street Light
• A Three Phase Contactor
• A Digital Timer
• An Auto/Manual Selector Switch
• A single pole MCB for the control circuit
• A Four Pole MCB as a main breaker

Connection Description

1. First of all, the main three-phase power supply is connected to the input of the Four Pole MCB.
2. The output of the Four Pole MCB is connected to the input of the Three Phase Contactor.
3. The output of the Three Phase Contactor goes to street lights. Each street light is connected to any one phase and is neutral through a single pole MCB.
4. All the streetlights are connected in such a way that each phase has the same number of streetlights. For example purpose, in the above wiring diagram, we have connected two street lights with each of the phases.
5. Now, the input of the control MCB is connected to the 'R' Phase. The output of the control MCB is connected to the input of the selector switch.
6. The power input neutral terminal(S2) of the Timer is directly connected to the neutral terminal of the four-pole MCB output. The power input phase terminal(S1) of the timer is connected to the "Automatic Output Terminal" of the selector switch.
7. The power input phase terminal(S1) of the timer is also connected to the Load Input(L1) terminal of the Timer. The load output terminal(L2) of the timer is connected to the phase terminal(A1) of the contactor coil.
8. The "Manual Output Terminal" of the selector switch is directly connected to the phase terminal(A1) of the contactor coil.
9. The neutral terminal(A2) of the contactor coil is directly connected to the neutral terminal of the four-pole MCB output.

Operation Principle

1. Power Supply and Main Protection (Four Pole MCB)

The Four Pole MCB acts as the main circuit breaker. It controls the power supply to the entire system. It protects the system from overloads and short circuits on the incoming three-phase supply.

2. Individual Light Protection (Single Pole MCBs)

Each street light is connected to an individual Single Pole MCB. These MCBs protect each light separately which ensures that a fault in one light does not affect the others.

3. Control Circuit Protection (Single Pole MCB)

The control circuit is powered through a separate single-pole MCB. This ensures that the control system is isolated from faults in the power circuit.

4. Control and Automation (Digital Timer)

The Digital Timer automates the switching of the street lights. It is programmed to turn the lights ON and OFF at specific times such as dusk and dawn. It reduces the need for manual intervention.

5. Manual and Automatic Control (Auto/Manual Selector Switch)

The Auto/Manual Selector Switch provides two modes of operation,

Auto Mode: In this mode, it connects the circuit to the Digital Timer which automatically controls the street lights.

Manual Mode: In this mode, it bypasses the Timer so the operator can manually turn the lights ON or OFF.

6. Load Switching (Three Phase Contactor)

The Three Phase Contactor acts as the switching mechanism. When the timer or manual switch provides a signal, the contactor closes, connecting the street lights to the power supply. It is designed to handle the high current required by the street lights while ensuring safe and reliable operation.

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