what is SLD ?

Single-line diagram (SLD), also sometimes called one-line diagram, is a simplified notation for representing a three-phase power system

The one-line diagram has its largest application in power flow studies. Electrical elements such as circuit breakers, transformers, capacitors, bus bars, and conductors are shown by standardized schematic symbols. Instead of representing each of three phases with a separate line or terminal, only one conductor is represented.

It is a form of block diagram graphically depicting the paths for power flow between entities of the system. Elements on the diagram do not represent the physical size or location of the electrical equipment, but it is a common convention to organize the diagram with the same left-to-right, top-to-bottom sequence as the switchgear or other apparatus represented. A one-line diagram can also be used to show a high-level view of conduit runs for a PLC control system.

Types of Earth-leakage circuit breaker

There are two types of Earth-leakage circuit breaker:

voltage-operated (as ELCB ) 

current operated ( as RCCB )

What is ELCB ?

 Earth leakage circuit breaker (ELCB) is a safety device used in electrical installations with high earth impedance to prevent shock. It detects small stray voltages on the metal enclosures of electrical equipment and interrupts the circuit if a dangerous voltage is detected. Once widely used, more recent installations instead use residual-current devices (RCDs, RCCBs, or GFCIs) which instead detect leakage current directly.