Substation Earthing System

Substation Earthing System

Substation earthing system is needed for providing the protection to peoples living and working in the nearby facilities and the equipment's to maintain proper working of electrical system.

The main aim of sub-station earthing is to provide the uniform potential around substation in actual case near to zero.

1. All parts of equipment connected to the earthing system should be at the ground potential. 
2. Operators and attendants should be at ground potential at all the times.

✓The earthing system gives a needed less resistance return path for earth fault currents which protects both personnel and equipment.

✓It indirectly avoids the presence of dangerous high level voltage across equipment's and working personnel.

✓Earthing prevents dangerous rise in ground potentials i.e. touch and step voltages.

✓Earthing system also provides a low resistance path for voltage transients due to lightning and surges /overvoltages.

✓Earthing system provides a ground or reference potential for electronic circuits which is necessary to reduce electrical noise for electronic, instrumentation and communication systems.

It involves three main systems as follows 

1. Earth mat 
2. Earthing spikes 
3. Earthing risers

An earth mat is used for connecting neutral points, equipment body and support structures to earth.

Due to this safety of working personnel is guaranteed also it is beneficial for enabling earth fault protection, even it provides path for discharging the earth currents from neutrals, faults, surge arrestors, overhead shielding wires etc. With safe step potential and touch potential.

Fire Fighting System

It involves four main system as follows:

1. Sensors and detection system
2. Water spray system
3. Fire port, panels, alarm system 
4. Water tank and spray system

It senses the occurance of fire by sensors and initiates water spray. It also disconnects power supply to affected region to pinpoint location of fire by indication in control system.

Miscellaneous Equipment

In addition to above, there may be following equipment in a Sub-Station.

1. Carrier-current equipment. 
2. Sub-Station auxiliary supplies.
3. Fire fighting system.
4. Diesel Generator (D.G.) Set
5. Oil purification system

Shunt reactors:

It is connected to distribution lines. During low load period it controls the voltage.

Shunt-capacitors :

They are placed at receiving stations and distribution sub-stations. They improve power factor by compensating reactive power(Iagging).

Series capacitors :

They are placed at sending end and or receiving end of line. They improves power transfer capacity of distribution system in case of long line.

Series reactors:

It is placed at suitable locations to reduce fault levels. They limit the short circuit current to limit current surges linked with variable or fluctuating loads.

Air Break switch :

This is an air break switch for isolation.

Drop-out fuse:

It is connected to the primary of distribution transformer in the incoming line. In case of fault the drop-out fuse melts and the line is tripped while drop-out fuse remain hagging.

Cross arms:

These are required for supports to the strain insulator to keep spacing between distribution conductors.

Anti-climbing device :

For pole mounted substation, this arrangement is for safety.