RESIDUAL CURRENT DEVICES: WHAT IS RCD AND WHAT DOES IT DO?

Fig-Residual Current Device Connection Procedure

What are the Residual Current Devices?

By definition, a residual current device is a current-activated circuit breaker used as a safety device for mains-operated electrical tools and appliances.

Electrical Substation Equipment: Circuit Breaker and Its Functions

A circuit breaker is an electrical switching device that automatically interrupts the flow of electric current in a circuit when it detects an overcurrent or a fault condition. It is designed to protect electrical circuits and connected devices from damage due to excessive current or short circuits.

The primary purpose of a circuit breaker is to prevent electrical fires and equipment damage that could occur if an excessive current flows through a circuit for an extended period. By interrupting the current flow, the circuit breaker stops the current from reaching dangerous levels and thereby protects the circuit and connected appliances or devices.

Fuse Rating Selection Chart

Fig- A Fuse

When selecting a fuse rating, it's important to consider the current rating of the circuit and the maximum current that the circuit can safely handle. The fuse rating should be chosen to protect the circuit by blowing when the current exceeds safe limits. Here is a general fuse rating selection chart that can serve as a guideline:

Types of Circuit Breakers: How to Classify Circuit Breaker?

Circuit Breakers are mechanical switching devices that can make, break, or carry a circuit manually or automatically under normal and abnormal conditions. 

The Circuit Breaker is described in short as CB; The characteristics of a Circuit Breaker are as follows:

A Circuit Breaker can make or break ae electrical circuit under normal operating conditions either manually or using a remote control.

Under abnormal or fault conditions, a Circuit Breaker can break the circuit automatically.

The Circuit Breaker can make the circuit under fault conditions either manually or using a remote control.

Under normal conditions, a circuit breaker can make, carry, or break currents, and under abnormal conditions, it can make or carry for a specific time and break the winds.

Common Types of Circuit Breakers

A Circuit Breaker contains two elements - 

• a thermal part that reacts to moderate overloads;
• a magnetic part that reacts to short circuits.

Basic types of the circuit breaker or MCB or Miniature Circuit Breaker you may find as below:

Type B

Trips between 3x and 5x the rated current.

For example - a 10A circuit breaker would need between 30A and 50A before it trips.

Type C

Trips between 5x and 10x the rated current. For example - a 10A circuit breaker would need between 50A and 100A before it trips.

Type D

Trips between 10x and 20x the rated current. For example - a 10A circuit breaker would need between 100A and 200A before it trips.

Type K

Less common, this type of trip is between 10x and 14x the rated current. This is within the trip range of the D type.

Type Z

Another uncommon option is type Z trips between 2x and 3x rated current. This puts it below the trip range of type B.

You may read the details of Air Circuit Breaker and Oil Circuit Breaker.

ABB, MCB (Miniature Circuit Breaker) Types and section conditions:

Electrical Substation Equipment: Circuit Breaker and Its Functions