Thursday 18 June 2015

Distance Relays

Reactance relays cant be made directional. A directional element cant be added to them since these relays operate under normal load condition and U.PF.

Reactance relays are used for ground faults because a ground fault relay should be independent of ground fault resisntance. ( which is variable).

Used for < 10 miles ( Short T.L.).

Mho relay or admittance relays ( for 50 miles +) is used for phase fault condition.

Arc resistance affects an impedance relay more than a reactance relay but less than Mho relay.

Bundled conductors

Advantages:-

  • Reduced reactance.( L is reduced)
  • Reduced voltage gradient. 
  • Reduced corona losses.
  • Reduced Radio intrerference.
  • Reduced surge impedance.
  • Oncreased capacity of transission.

Thursday 14 May 2015

Buildings Fire safety

IS 1646- 1982:

This IS covers following points: 

General Requirements

Power Equipment

Switchboards

Power Distribution and Motor Control Gear

Transformer Substation, Excluding Bell and Drawing Frame, Transformer and Transformers of Small Capacity

Earth Conections

Wiring Methods

Permitted Types of Wiring Methods

Lighting, Fittings and Accesories

Special Electrical Equipment and Appliances

Requirements For special Occupancies

General Godowns

Testing

Inspection


Symbols and connection diagrams of circuits