With the help of a Single Line Diagram indicate the switchgear and equipment used in a typical 33/11 KV sub-station. Mention the annual maintenance practices adopted.

Below is a simplified Single Line Diagram (SLD) of a typical 33/11 kV substation, indicating the switchgear and equipment commonly used:

        _______________________________
       |                               |
       |       33/11 kV Transformer    |  
       |_______________________________|
                  |
          ________|__________
         |                    |
         |    33 kV Switchgear  |
         |____________________|
                  |
          ________|__________
         |                    |
         |    11 kV Switchgear  |
         |____________________|
                  |
          ________|__________
         |                    |
         |     11 kV Feeder     |
         |____________________|
                  |
          ________|__________
         |                    |
         |   11/0.415 kV        |
         |   Distribution       |
         |   Transformer        |
         |____________________|
                  |
          ________|__________
         |                    |
         |   415 V Switchgear  |
         |____________________|
                  |
         ________________
        |                |
        |  415 V Load    |
        |________________|

Equipment Used:

1. 33/11 kV Transformer: Step-down transformer to reduce voltage from 33 kV to 11 kV.
2. 33 kV Switchgear: Circuit breakers, isolators, and other protective devices for the 33 kV side.
3. 11 kV Switchgear: Similar equipment for the 11 kV side.
4. 11 kV Feeder: Cable or overhead line supplying power to various distribution transformers.
5. 11/0.415 kV Distribution Transformer: Step-down transformer to supply 415 V power for local distribution.
6. 415 V Switchgear: Switchgear for the 415 V distribution network.
7. 415 V Load: Various loads connected to the 415 V distribution system.

Annual Maintenance Practices:

1. Transformer Maintenance:

   • Insulation resistance tests.
   • Oil testing for dielectric strength and moisture content.
   • Thermography for hot spot detection.
   • Cleaning and tightening of connections.

2. Switchgear Maintenance:

   • Insulation resistance tests.
   • Contact resistance measurements.
   • Visual inspection for signs of damage or corrosion.
   • Lubrication of moving parts.
   • Cleaning of insulators.

3. Feeder Maintenance:

   • Inspection of cables and overhead lines for signs of wear, damage, or vegetation interference.
   • Tightening of connections.
   • Testing of protective relays and devices.

4. Distribution Transformer Maintenance:

   • Oil testing for dielectric strength.
   • Inspection of bushings and connections.
   • Cooling system maintenance.
   • Thermography for hot spot detection.

5. General Maintenance Practices:

   • Grounding system inspection.
   • Inspection of fences and security measures.
   • Training and retraining of personnel on safety procedures.
   • Record keeping and documentation of maintenance activities.