Kerala Electrical Inspectorate’s Technical Diary

All fresh electrical engineers attending job interviews, or experienced engineers faced with a requirement of planning a new electrical installation, are faced with a challenge to be aware of and follow the existing rules and regulations put in place by statutory authorities. Designers will be familiar with these rules, but who are in maintenance, service, or marketing may be totally oblivious even to the existence of them. I have seen people who are otherwise very good maintenance engineers stumble when asked to design a new system as an addition or augmentation of their existing facilities. The issue becomes formidable as the company is required to obtain license from a competent authority for the addition. What is to be done in this case? If you work for a big corporation that has multiple wings and design departments and/or consultants to do this work, you may be free from this burden, but still, you are expected to review their design and comment on it. Designers will be somewhat comfortable with a little overrating of the equipments, but as the man to pay for the additional capacity, it is your job to ask them to cut down on their liberal design in order to reduce the amount you actually end up paying. In order to do this, awareness of the rules and regulations is mandatory.

The technical diary brought out by the Kerala Electrical Inspectorate Engineers’ Welfare Society is an excellent document. It brings out a slew of tables, check lists, rules of thumb and extracts from relevant rules pertaining to most of the installations we can think of. Unfortunately, this diary is not for sale and is normally issued only to its members and complimentary copies released to its patrons. Recently, I got hold of a copy of 2012 diary and I think it will be really nice to share it here for all. Since the data runs into many tens of pages, it will take some time for me to come out with a searchable soft copy of the entire content. So, the tables will be published one by one. The rules and regulations stipulated here will be applicable everywhere in India with minor changes enforced by various states.

This post contains an index and update of the tables issued so far.

Serial Number	Subject	Release date
1	Basic Electrical Laws	2016 Sep 29
2	The Electricity Act, 2003	2016 Sep 30
3	Important Provisionsin the Electricity Act 2003 & CEA Regulations 2010	2016 Oct 01

Basic Electrical Laws

Joule's Law

The heat produced by a current I flowing through a resistance R for a time t, is proportional to l²Rt  or,  Heat = (I² R t) / J   where J = 4.2 Joules / cal

Ampere's Rule

This rule gives the direction in which a magnetic needle deflect when placed near a current carrying conductor. Imagine a person swimming in the direction of the current, facing the magnetic needle. Then the direction of deflection of the north pole of the needle will be towards his left side.

Coulomb's Law

The force between two electric charges is directly proportional to the product of the magnitude of the charges and inversely proportional to the square of the distance between them.

Ampere's right hand rule

This gives the direction of magnetic field around a current carrying conductor. Imagine that the wire is gripped in the right hand with thumb pointing along the wire in the direction of current. Then the direction of the fingers will give the direction of the magnetic field.

Maxwell's cork-screw rule

This also gives the direction of the magnetic field around a current carrying conductor. Imagine that a right-handed corkscrew is driven in the direction of the current flow. Then the direction of magnetic field due to the current will be the direction of rotation of the head of the screw.

Laws of Parallel Currents

1.    Two parallel conductors attract each other if the currents through them flow in the same direction and repel each other if the currents through them flow in the opposite direction.

2.    The force between two such parallel conductors is proportional to the product of the current strengths and to the length of the conductors considered and varies inversely as the distance between them

Faraday's Laws of Electromagnetic Induction

1.    Whenever the magnetic flux linked with a circuit changes, an EMF is always induced in it.

2.    The magnitude of the induced EMF is proportional to the rate of change of flux-linkage

Lenz's Law

The electromagnetically induced current always flows in such a direction as to oppose the very cause which produces it.

Fleming's Left-hand Rule (for motor action)

This gives the direction of force on a current carrying conductor placed in a magnetic field. Hold the left hand with forefinger, middle finger and thumb at right angles to one another. If the forefinger represents the direction of the field and the middle finger that of the current, then the thumb gives the direction of motion of the conductor.

Fleming's Right-hand Rule (for generator action)

This gives the direction of induced current in a conductor, which is moved in a magnetic field. Hold the right hand with forefinger, middle finger and thumb at right angles to one another. If the forefinger represents the direction of the field and the thumb that of the conductor motion, then the middle finger gives the direction of induced current.

Kirchhoff's Laws

1.    In an electrical network, the sum of the currents entering a junction is equal to the sum of the currents leaving the junction.

2.    The algebraic sum of the potential differences around a closed circuit is zero.

Maxwell's Law

1.    Any two circuits carrying current tend so to dispose themselves as to include the largest possible number of lines of force common to the two.

2.    Every electromagnetic system tends to change its configuration so that the exciting circuit embraces the largest number of lines of force in a positive direction

Hall Effect

It states that if a magnetic field is applied perpendicular to a metal plate, which carries a current, then a transverse voltage is set up in the plate perpendicular to both the current and the magnetic field. This transverse voltage is known as Hall Voltage.

Seebeck Effect

When two dissimilar metal wires are joined at the ends to form two junctions (thermocouple) and when these junctions are kept at different temperatures, an EMF is produced in the circuit. This is called Seebeck Effect.

Peltier Effect

When an electric current is passed through a thermocouple, then heating is produced at one junction and cooling at the other junction.

Colour coding of resistors

Colour	Number	Colour	Number	Tolerance
Black	0	Green	5	Gold: ± 5% Silver: ± 10% No colour: ± 20%
Brown	1	Blue	6
Red	2	Violet	7
Orange	3	Grey	8
Yellow	4	White	9

Assessment of the value of resistance

First two bands from the end indicate the first two significant figures of resistance in ohm.

The 3rd band indicates the decimal multiplier.

The last band stands for the tolerance in percentage.

Example

First band - Yellow                 = 4

Second band - Violet             = 7

Third band - Brown                = 1       i.e. 10¹

Fourth band - Gold                = ±5% tolerance

Therefore the value of resistance   = 47 x 10¹ ± 5% = 470 ohm ± 5% tolerance