Electricity is very helpful and very dangerous also. So when generating, transmitting, and using electricity safety must be required. There are different types of electrical protective devices such as MCB, RCCB, MCCB, ELCB, etc. RCCB or Residual Current Circuit Breaker is a very well-known and useful electrical protective device. RCCB works on the principle of leakage current and current unbalancing. There are different types of possible electrical faults that may happen in an electrical circuit, some of them can be prevented by using an RCCB but not all of them. So here the list of electrical faults an RCCB can protect and can't protect is given below.

## The list of Electrical Fault RCCB can Protect

### 1. Phase to Earth Fault

Phase to Earth fault is very dangerous it causes to flow of a very high current and makes fire also. RCCB can protect Phase to earth fault. Generally, RCCB is connected with Phase and neutral wire and it monitors if there is equal current in phase and neutral or not. If there is an imbalance in phase and neutral, the RCCB will Trip. So when the phase-to-earth fault occurs means the phase wire comes in contact with the earth wire current will start to flow from phase to earth but no current flow through the neutral wire. So as an imbalance occurs in phase and neutral RCCB will trip during the phase to earth fault.

### 2. Neutral to Earth Fault

When a neutral wire touched the Earth wire and causes a flow leakage current then it is called Neutral to Earth Fault. Neutral wire always comes from the power source. So if the distance between the source and load is more then there will be a voltage drop in the neutral wire. But earthing is always done near to the load so the length of the earth wire is small compared to neutral wire and has low resistance and low voltage drop. On the power source side, neutral and earth are connected together so their potential difference is zero. But near to the load, there is always a potential difference between neutral and earth. So when the neutral wire which already connected to a load touched the earth wire current will be start to flow from the phase to the earth through the load and neutral wire. I mean to say that when the neutral wire touched the earth on the load side current imbalance will occur in phase and neutral so the RCCB will trip.

### 3. Phase-to-Phase Fault

Three-phase RCCB can protect phase-to-phase fault. Three-phase RCCB is connected with all the three phases, so when among those three phases any two accidentally come in contact a huge current will flow between those two phases and another phase carrying low current, so in this case, the RCCB will trip to disconnect the main power supply.

### 4. Earth Leakage

An RCCB is most suitable for earth leakage protection. Earth leakage fault produces heat, loss, and creates more energy consumption. So it is must require to prevent earth leakage faults in an electrical circuit. When the unwanted current flows from the phase or any higher potential conductor to the ground through the earthing conductor then it is called earth leakage and the current is called leakage current. So when the earth leakage fault occurs, the current imbalance occurs in the phase and neutral so the RCCB will trip and it cannot be turned on again until the problem is solved.

### 5. Electrical Shock

RCCB is the only one best device to protect humans from electric shock. A 30mA RCCB is most suitable for the protection against electrical shock. When any person accidentally touches the phase wire current will start flowing from the phase to the ground through the body of that person which makes the current imbalance between the phase and the neutral. As a result, the RCCB will be got a trip and disconnect the main power supply, so the person will be safe.

### 6. Surge and Voltage Imbalance

Yes, RCCB can give protection against Surge and voltage imbalance up to a certain limit. When surge voltage imbalance occurs then the current imbalance also happens so RCCB got trip and protect the circuit. Remember that RCCB not designed for surge protection, so it cannot give protection a hundred percent against the surge in fact the surge voltage is more than the RCCB also be damaged.

## The list of Electrical Fault RCCB Can't Protect

RCCB cannot give protection against Overload faults. When an electrical load draws excess current then it is called overload. In the overload fault, the current is always equal in both phase and neutral even if the amount of current is high. So the RCCB cannot detect the fault.

### 2. Short Circuit Fault

RCCB cannot give protection against short circuit faults. Same as the overload fault, in the short circuit fault also current is equal in both phase and neutral. So RCCB cannot detect it. In fact, RCCB may damage during short circuit faults. So, always an MCB is connected before RCCB for overload and short circuit protection.

### 3. Single Phasing

Single phasing means when one phase is broken or disconnected among the three phases of a three-phase power supply. RCCB cannot give protection against single phasing. Three-phase RCCB works on the principle of balancing and unbalancing all three phases. So when one phase is broken, then also resultant flux is zero because equal current flows in the other two phases.

### 4. Voltage Fluctuation

RCCB cannot protect the equipment or appliances from voltage fluctuation until it makes an imbalance in current. Actually, RCCBs are not designed to protect against voltage fluctuations. Voltage fluctuations refer to rapid and temporary changes in the voltage level supplied to electrical appliances or equipment. These fluctuations can be caused by various factors, such as changes in the power grid, load variations, or disturbances in the electrical system.

The RCCB's primary function is to detect imbalances in the current, not fluctuations in voltage. It does not monitor the voltage level in the circuit, and therefore it cannot provide protection against voltage fluctuations.