BASICS OF EARTHING IN SUBSTATION AND TRANSMISSION TOWER

Earthing of Substation Equipment

The points we must earth in an electrical substation include the following steps:

The neutral point contains different voltage levels in the earthing

The metallic enclosure contains all current-carrying equipment for earthing

The framework of all current-carrying equipment in the earthing

All the metallic structure are associated with current-carrying equipment in the metal plate

We connect all the points to be earthed with the earthing grid with corrosion resistance mild still rods in the plate. We bury the connection rods a minimum of 600 mm below the ground level. If these horizontally buried rods have a cable trench, road, underground pipework, or rail track then the rods should cross the barriers at least 300 mm below the bottom of the barriers for the earthing.

we use MS rods for connecting and also earth grid below the ground level when we normally use ms flats for the same above ground level in the earthing. We call the connection between different earthing points and earning grid as the riser of the metal plate. We normally use ms flats in the portion of the risers above ground level in the metallic plate. The rod portion of the risers has the ground level which is identical to the rod conductors and it will use for creating the main earth grid in the metal plate.

We should connect all the steel structures with the earth grid by at least two risers of the metal. In this case, one riser must come from the rod of earthing grid in one x-direction and other from another y-direction in the substation.

We also connect the earthing points of all equipment in the same method for proper earthing

We connect all the isolator mechanism boxes with individual auxiliary earth mat and also it contains each auxiliary earth mat to main earth grid in the substation and we place each auxiliary earth mat just 300 mm below the ground level in the earthing.

We connect all the raiser’s flats to earthing pads of the equipment by the nut bolts and also we should paint the bolted connections by anticorrosive paints in the whole substation. This point of earth can not be welded to facilitate equipment replacement as when required in the earthing point.

The leads come as riser from the earth mat should be welded with earth grid in the connected system. The flats have above-ground sand also be welded to the rod conductors below the ground for proper earthing. We must paint the welded points with red lead and bitumen for the earthing.

The shield wire comes down with the leg of the gantry structure in the system. The shield wire will come down along with a leg of gantry structure is referred to as downcomer in the earthing. The downcomer is clamped with the leg members and the structure at every 2 meters intervals needs to be provided. This downcomer is connected with an earthing lead and coming directly from a pipe earth electrode in the control system. Diagonally opposite leg of the same structure will directly be connected to the main earthing grid via riser for the earthing.

Earthing of Bus Post Insulator

Each bus post insulator or BPI is connected to the main earthing grid through two risers and it contains the measurement of 50 mm × 10 mm ms flat comes down along the BPI support structure with each of the two earthing points of BPI metallic base in the metal rod. These ms flats from the base of the BPI are connected to the risers and it will come from x and y conductor of the main earthing grid in the earthing.

Earthing of Current Transformer

One 50 mm × 10 mm ms flat comes down along with the leg of the current transformer and support structure from the metallic base of the in the metallic plate. This is connected with the main earthing grid via the riser of the method. Diagonally opposite vertical leg members of the structure have to be connected to the main earthing grid via another riser in the metallic plate of the earthing. If the first riser comes from the x conductor of the ground grid and the second riser must come from the rod conductor of another y-direction in the rod.

The CT junction box has to connected to the main earthing grid from two points in the measurement value of  50 mm × 10 mm ms flats in the metal plate.

The structure of each pole of a circuit breaker along with the metallic base poles is connected to the main earthing grid and it has two risers one is preferably from x and other from another y-direction in the earthing. The structure of the poles are connected together with measurement values of 50 mm × 8 mm ms flat and The mechanism box of each pole is also connected with the main earthing grid via 50 mm × 10 mm ms flat in the substation.

Earthing of Isolator

The base of each pole of the isolator should need to be connected together with the help of one 50 mm × 10 mm ms flat in the metal rod. This ms flat will be connected to the main earthing grid through two risers one preferably from x and other from another y-direction earth mat conductors in the earthing. The mechanism box of the isolator should be connected to the auxiliary earth mat and the auxiliary earth mat is connected to the main earthing grid.

Earthing of Lightning Arrestors

The base of the lightning arrestors will be connected to the main earthing grid through one riser and the structure of the lightning arrestors must be connected to the main earthing grid via another riser in the earthing. One extra earthing connection in lightning arrestors which will connect a treated earth pit via surge counter of the arrestors in the metal bit. This earth pit maybe with the test link in earthing.

Earthing of Capacitive Voltage Transformer

The base of the CVT or capacitive voltage transformer is connected with the main earthing grid through a  riser in the controller. The special earthing point on the base of the CVT is connected with the pipe earth electrode with the measurement of 50 mm × 8 mm ms flat in the earthing grid. The bottom portion of the support structure can be connected to the main earthing grid through the riser in the method. The two opposite earthing points of the  CVT junction box and also be connected to the main earthing grid in the cable sealing.

The supporting structure of a cable sealing system should need to be connected with the main earthing grid via two risers in the earthing strip. The earthing strip has a measurement size of 50 mm × 10 mm ms flat must come down from the top of the supporting structure in the substation.

Earthing of Bay Marshalling Kiosk

There are two protected leads provided on two opposite sides of the bay marshaling kiosk in the earthing. These two points must need to be connected with the main earthing grid through two risers and These links are provided on the lower portion of the marshaling kiosk or box in the earthing plate.

Earthing of Earthing Transformer

The base of the earthing transformer must be connected to the main earthing grid via two risers in the base. The neutral point of the earthing transformer must be connected to the pipe earth electrode with a test link in the earthing. The neutral to ground connection should go through a neutral current transformer for earth fault protection purpose of the transformer link.

Electrical Earthing

The process of transferring the immediate discharge of the electrical energy which is direct to the earth with the help of the low resistance wire and is known as the electrical earthing of the method. The electrical earthing is done by connecting with the non-current carrying part of the equipment or neutral of the supply system to the ground in the method.

The galvanized iron is used for the earthing in the substation. The earthing provides a simple path of the leakage current in the equipment. The shortcircuit current of the equipment passes through the earth which has zero potential in the earthing substation. To protects the system and equipment from the damage to the system.

Types of Electrical Earthing

The electrical equipment mainly consists of two non-current carrying parts in the earthing. These parts are neutral for the system or the frame of the electrical equipment in the system. From the earthing, there are two non-current carrying parts of the electrical system earthing and can be classified into two types.

Neutral Earthing

Equipment Earthing.

Neutral Earthing

In neutral earthing, the neutral of the system is directly connected to earth with the help of the GI wire in the electrical system. The neutral earthing is also called the system earthing in the base system. Such type of earthing is mostly provided to the system which has star winding in the contoller., The neutral earthing is provided in the generator, transformer, motor, etc for proper earthing.

Equipment  Earthing

The earthing is provided to the electrical equipment in the non-current carrying part of the equipment like their metallic frame and is connected to the earth by the help of the conducting wire in the earthing. The apparatus, such as short-circuit current to pass the earth with the help of wire in the base metal. 

Importance of Earthing

The earthing is essential because of the following reasons

The earthing protects the personnel form of shortcircuit current in the earthing.

The earthing provides the easiest path to the flow and the shortcircuit of current even the failure of the insulation in the metallic parts.

The earthing protects the apparatus and personnel from the high voltage surges and lightning discharge of the system.

The earthing mat or electrode under the ground level and has a flat iron riser through which the non-current-carrying metallic parts of the equipment are connected in the control system.

Then the fault occurs the fault current from the equipment flows through the earthing system and the earth which protects the equipment from the fault current in the system. At the time of the fault, there is an earth mat conductors that rise to the voltage which is equal to the resistance of the earth mat multiplied by a ground fault in the network.

The contacting assembly is called earthing in the metallic plate. The metallic conductors connecting to the parts of the installation with which the earthing are known as the electrical connections the metal plates. The earthing and the earthing connection together called the earthing system in the metal plate.

It will connect to the metallic (conductive) Parts of an Electric appliance or installations to the earth (ground) is known as the Earthing or Grounding.

The earth or earthing means to connect the part of the electrical apparatus which is used for the metallic covering of metals, and the earth terminal of socket cables, and the stay wires that do not carry current to the earth in the electrical energy. Earthing can be said as the connection of the neutral point of a power supply system and to the earth so as to avoid or minimize danger during the discharge of electrical energy in the control system.

A metallic electrode or plate which is buried in the earth (underground)in the metal and it is the last part of the electrical earthing system in the earth electrode. The final underground metallic (plate) part of the earthing system which has to be connected with earthing lead and is known as the earth plate or earth electrode.

A metallic plate, pipe, or rode can be used as an earth electrode that has very low resistance and carries the fault current safely towards the ground (earth)in the metallic plate. the stay wires that do not carry current to the earth in the electrical energy.

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