Grounding, Earthing and Protection Against Lightning Procedure as Bangladesh Electricity Distribution Code

If you do not follow the electricity safety code it's may danger anytime

Why is Earthing Necessary in Electrical Systems?

The main purpose of the earthing of any electrical appliance is to protect it from carrying current due to accidental contact with the live wire or what is called the phase wire of the power supply system. It is a good practice to provide two parallel connections of the earth conductor to any electrical installation whether it is for domestic or industrial use. Normally Copper wire or strip is used as an earthing conductor but nowadays it is replaced by Galvanized Iron or Aluminum conductor is also used since Copper is costly and chances of theft or pilferage are high.

There are three wires which run through the domestic electrical circuits.

• Live wire
• Return or Neutral wire
• Ground or Earth wire.

In a normal situation when an appliance is switched on the circuit completes its path from live wire to return wire.

But in case a splice of live wire comes in contact with the metal part of the appliance, then the user has a chance of getting shocked because he completes the circuit with the ground as the return conductor.

In order to ensure the safety of the users, a simple concept of current is followed I.e. current flows through the lowest resistance path. An Earth wire of the domestic household is connected to all the power appliances connected to the earthing pit and Earth point at the METER.

With the Earth wire now the circuit from appliance metallic Parth to Earth wire is the lowest return path so the users are saved from electrical shock.

The resistance of the Earth wire circuit is in the order of tens of ohms whereas ad the resistance of the Human body is between 500 k ohms to Mega ohms.

What says about Grounding, Earthing, and Protection against Lightning in Bangladesh Electricity Code?

As per Annex G-04 Section 6 ERQ Distribution Code, the ELECTRICITY DISTRIBUTION CODE (UPDATED DRAFT) on November 2012, Chapter 14 OVERHEAD LINES, UNDERGROUND CABLES AND GENERATING STATIONS, Clouse 15, 17 & 19 described Grounding, Earthing, and Protection against Lightning respectively.

Let's see the detailed step by step:

Guarding as per Bangladesh Electricity Distribution Code

1. Where guarding is required under these clauses the provisions of 15(2) to (4) shall apply. 
2. Every guard wire shall be connected with earth at each point at which its electrical continuity is broken. 
3. Every guard wire shall have an actual breaking strength of not less than 635 kg and if made of iron or steel, shall be galvanized. 
4. Every guard-wire or cross-connected system of guard wires shall have sufficient current-carrying capacity to ensure the rendering is dead, without risk of fusing of the guard wire or wires till the contact of any live wire has been removed. 

You may read details about the earthing system in a separate full article on 

Equipment Grounding for De-energized Construction and Maintenance.

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Earthing as per Bangladesh Electricity Distribution Code

1. All metal supports and all reinforced and pre-stressed cement concrete supports of overhead lines and metallic fittings attached thereto shall be permanently and efficiently earthed. For this purpose, a continuous earth wire shall be provided and securely fastened to each pole and connected with earth ordinarily at three points in every km, the spacing between the points being as nearly equidistant as possible. Alternatively, each support and the metallic fitting attached thereto shall be efficiently earthed. 
2. Metallic bearer wire used for supporting insulated wire of low voltage overhead service lines shall be efficiently earthed or insulated. (3 Each stay-wire shall be similarly earthed unless an insulator has been placed in it at a height not less than 3.0 meters from the ground. 

 You may read details about the earthing system in a separate full article on 

HOW TO ENSURE PERFECT EARTHING OR GROUNDING SYSTEM - IEC

Protection against lightning as per Bangladesh Electricity Distribution Code

1. The owner of every overhead line, substation, or generating station which is so exposed as to be liable to injury from lightning shall adopt efficient means for diverting to earth any electrical surges due to lightning. 
2. The earthing lead for any lightning arrestor shall not pass through any iron or steel pipe, but shall be taken as directly as possible from the lightning arrestor to a separate earth electrode and/or junction of the earth mat already provided for the high and extra-high voltage substation subject to the avoidance of bends wherever practicable.  Note-A vertical ground electrode shall be connected to this junction of the earth mat. 

You may read details about the earthing system in a separate full article on 

How Does A Simple Lightning Conductor Protect A Building?

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One of the things you eventually realize about electricity is that everything you do is different in potentials, or voltages. A circuit with a high of 10V to a low of 5V is really the same as a circuit with a high of 5V and a low of 0V. Earth is our ultimate zero reference. Think about the electric lineman in a helicopter fixing voltage transmission lines in the 10,000’s volts. They are ok because the reference frame they are in is 10,000V relative to the earth, but relative to the lineman it's zero. Because the lineman is not referenced to earth, he/she is not tied to the ground. And they live. Is “earth” important yes it is, especially when dealing with electrical systems at different potentials, or with systems that are physically a distance from each other?

EARTHING or GROUNDING Objective Questions:

1. The size of the earth or ground wire is based on the
a) maximum fault current carrying through the ground wire
b) rated current carrying capacity of the service line
c) depends on the soil resistance
d) both (a) and (c)

Ans: d

2. Earth wire or ground wire is made of
a) copper
b) aluminum
c) iron
d) galvanized steel

Ans: d

3. Average resistance of the human body is
a) 500 ohms
b) 1000 ohms
c) 1500 ohms
d) 2000 ohms

Ans: b

4. Generally grounding is provided for
a) only for the safety of the equipment
b) only for the safety of the operating personnel
c) both (a) and (b)
d) none of the above

Ans: c

5. Ground resistance should be designed such that
a) grounding resistance should be as low as possible
b) grounding resistance should be as high as possible
c) grounding resistance should be always zero
d) none of the above

Ans: a

6. For EHV equipment for maintenance first it should be isolated and connected to the ground because
a) to provide a low impedance
b) to discharge the charging capacitance to ground
c) protection for operating personnel
d) both (b) and (c)

Ans: d

7. When earth fault occurs
a) voltage potential at the earth mat increases due to grounding
b) voltage potential at the earth mat decreases due to grounding

c) voltage potential at the earth mat remains zero irrespective of fault
d) none of the above

Ans: a

8. The objective of earthing or grounding is
a) to provide as low resistance possible to the ground
b) to provide as high resistance possible to the ground
c) to provide flow of positive, negative and zero sequence currents
d) none of the above

Ans: a

9. Moisture content in the soil __ the earth soil resistance
a) increase
b) decrease
c) does not affect
d) none of the above

Ans: b

10. Factors on which soil resistance depends
a) depth of the electrode
b) moisture
c) Nacl
d) all the above

Ans: d

11. When the 3-phase system is not grounded and if Single Line to Ground fault occurs, the voltage of the other two healthy phases will
a) Increases
b) Decreases
c) Remains unaffected

Ans: a