AC Supply Insulated, isolated or ungrounded neutral system

Summary

This video script delves into the concepts of earthed and insulated neutral systems in AC supply. It explains the fundamental differences between the two, highlighting that an earthed neutral system connects the neutral to the earth at the substation, while an insulated neutral system keeps the neutral isolated. The script further discusses the implications of faults in these systems, emphasizing that an insulated neutral system allows continuous operation of equipment during a fault between line and earth, which is crucial for applications like ships and chemical industries where uninterrupted function is vital. It also touches on the use of isolating transformers and safety measures like enclosures to prevent electrical hazards.

Takeaways

• 🔌 The Earth Neutral System: In this system, the neutral is connected to the earth at the substation, providing a path for fault current to flow, causing the MCB to trip and interrupting the AC supply.
• 🛡️ The Insulated Neutral System: Here, the neutral is not connected to the earth, preventing fault currents from flowing in the event of a line-to-earth fault, thus maintaining the AC supply and avoiding MCB tripping.
• 🚫 Fault Handling: In an Earth Neutral System, a fault between the line and earth will cause a short circuit, leading to an MCB trip, whereas in an Insulated Neutral System, such a fault will not result in a short circuit or MCB trip due to the lack of a return path.
• ⚠️ Single Fault Protection: The Insulated Neutral System offers protection against the first fault between the line and earth but not subsequent faults, which can cause the system to trip.
• 🔄 Isolating Transformer: An isolating transformer can be used in an Earth Neutral System to create an Insulated Neutral System, preventing short circuit currents from flowing and keeping the equipment operational.
• 🏭 Industrial Applications: Insulated Neutral Systems are particularly useful in industries where continuous operation of equipment is critical, such as in ships, train engine VFDs, chemical industries, and telecommunication.
• 🔍 Selective Use: Insulated Neutral Systems are not universally applied but are used selectively in areas where their benefits in maintaining continuous operation are most needed.
• 🌐 Utility Connections: Even if an Insulated Neutral System is desired, the neutral-to-earth connection made by the electricity board at the substation cannot be avoided without using an isolating transformer.
• 💡 RCD as an Alternative: Connecting a resistor-capacitor (RC) network between the neutral and earth can provide high impedance, allowing minimal fault current to flow and preventing the MCB from tripping.
• 🛡️ Safety Precautions: For safety, enclosures are used in Insulated Neutral Systems, with the enclosure body connected to the earth to prevent unauthorized access and potential hazards.
• 🔄 Comparison of Systems: The Earth Neutral System is more prone to MCB tripping after a fault, while the Insulated Neutral System maintains operation unless a second fault occurs, emphasizing the importance of timely repairs.

Q & A

What is an earth neutral system?

An earth neutral system is an electrical system where the neutral wire is connected to the earth at the substation. This connection allows for a return path for electrical current in case of a fault, such as a short circuit.

What is an insulated neutral system?

An insulated neutral system is one where the neutral wire is not connected to the earth. This system is used to maintain continuous operation of equipment in certain applications where a fault between the line and earth does not cause a short circuit current to flow, preventing the MCB from tripping.

What is the primary difference between an earthed neutral system and an insulated neutral system?

The main difference lies in the connection of the neutral wire to the earth. In an earthed neutral system, the neutral is connected to the earth at the substation, while in an insulated neutral system, the neutral is insulated and not connected to the earth.

Why would an MCB trip in an earth neutral system during a fault?

An MCB trips in an earth neutral system during a fault because the fault creates a complete path for the short circuit current to flow, causing a high current that the MCB detects and interrupts to prevent damage.

Why does an MCB not trip in an insulated neutral system during a fault between line and earth?

In an insulated neutral system, a fault between line and earth does not provide a return path for the current, so no significant short circuit current flows, and the MCB does not trip, allowing the equipment to continue operating.

What is the purpose of using an insulated neutral system in certain applications?

The insulated neutral system is used in applications where high function continuity is required, and it prevents the MCB from tripping during a fault between line and earth, ensuring the equipment continues to operate.

What happens if a fault occurs between line and neutral in an insulated neutral system?

If a fault occurs between line and neutral in an insulated neutral system, a short circuit current will flow, causing the MCB to trip and the equipment to stop working, as there is now a direct path for the current.

How can an isolating transformer be used to prevent an MCB from tripping in an earth neutral system?

An isolating transformer can be used to create an insulated neutral system within an earth neutral infrastructure. It electrically isolates the load from the earth, preventing short circuit current from flowing in case of a fault between line and earth, thus preventing the MCB from tripping.

What is the role of an RC connection between neutral and earth in an insulated neutral system?

The RC connection, consisting of a resistor (R) and capacitor (C), provides a high impedance path to the earth. In case of a short circuit, the high impedance limits the current flow, preventing the MCB from tripping and allowing the load to continue working.

Why is an enclosure provided in an insulated neutral system, and how is it connected?

An enclosure is provided in an insulated neutral system for safety reasons to prevent unauthorized access to the electrical components. The enclosure body is connected to the earth to ensure that any fault current is safely directed to the earth, protecting personnel from electric shock.

In which industries or applications is the insulated neutral system commonly used?

The insulated neutral system is commonly used in industries and applications where continuous operation of equipment is critical, such as in ships, train engine VFDs, chemical industries, and telecommunication systems.

Outlines

00:00

🔌 Understanding Earth and Insulated Neutral Systems

This paragraph introduces the concepts of earth neutral and insulated neutral systems in AC supply. It explains that in an earth neutral system, the neutral is connected to the earth at the substation, while in an insulated neutral system, the neutral is not connected to the earth. The paragraph also discusses the implications of a fault between the line and earth in both systems. In an earth neutral system, a fault would cause a short circuit, triggering the MCB to trip and cutting off the AC supply. Conversely, in an insulated neutral system, a fault between the line and earth would not result in a short circuit, allowing the AC supply to continue uninterrupted. This system is beneficial in applications where continuous operation of equipment is crucial.

05:02

🛠️ Fault Handling in Insulated Neutral Systems

This paragraph delves deeper into the insulated neutral system, highlighting its advantages in handling faults. It explains that if a fault occurs between the line and earth, the insulated neutral system can continue to operate without interruption because there is no return path for the short circuit current. However, if a second fault occurs, the system will not be protected, and the equipment will stop working. The paragraph also discusses the use of an RC connection between the neutral and earth to further protect the system from short circuits. Additionally, it mentions the use of an isolating transformer to ensure that even if a short circuit occurs, the MCB will not trip, and the equipment will continue to operate. The paragraph concludes by emphasizing the importance of safety measures, such as enclosing the system and connecting the enclosure to the earth.

10:12

🚢 Applications of Insulated Neutral Systems

The final paragraph focuses on the applications of insulated neutral systems, emphasizing their use in environments where high function continuity is required. Examples include ships, train engine VFDs, chemical industries, and telecommunication systems. It is noted that these systems are not used universally but are implemented only when necessary. The paragraph also mentions the use of insulated neutral systems in CRO or DSO supply, referencing a previous video on DSO oscilloscope use. The discussion concludes with a brief mention of the importance of understanding these systems for their effective application in various industries.

Keywords

💡AC Supply

AC Supply refers to the alternating current electrical power that is commonly used in homes and businesses. In the video, AC supply is described as coming from a substation and being connected to a load. It is the primary source of power discussed in the context of earth neutral and insulated neutral systems.

💡Earth Neutral System

An Earth Neutral System is a type of electrical system where the neutral point of the supply is connected to the earth at the substation. This connection helps in stabilizing the voltage and provides a return path for fault currents. The video explains that in such a system, if a fault occurs between the line and earth, the current will flow, causing the circuit breaker (MCB) to trip and interrupt the supply.

💡Insulated Neutral System

An Insulated Neutral System is a variation where the neutral point is not connected to the earth. This system is designed to prevent the flow of fault currents in the event of a fault between the line and earth, thereby maintaining continuous operation of the equipment. The video script highlights that in this system, the neutral is insulated, preventing the MCB from tripping and allowing the load to continue receiving power.

💡Fault

A fault in the context of the video refers to an unintended electrical connection between two points that should not be connected. The video discusses how different types of faults (e.g., between line and earth, or between line and neutral) affect the operation of the electrical system. For instance, a fault between line and earth in an earth neutral system would cause the MCB to trip, while in an insulated neutral system, it would not.

💡MCB (Miniature Circuit Breaker)

An MCB is a safety device designed to protect electrical circuits from damage caused by excess current. In the video, it is mentioned that an MCB will trip in response to a short circuit or overload, thereby cutting off the power supply. The behavior of the MCB is crucial in determining how an earth neutral or insulated neutral system responds to faults.

💡Short Circuit

A short circuit is a fault condition where a low-resistance path is created between two points in an electrical circuit that should not be connected. The video script explains that in an earth neutral system, a short circuit between the line and earth would result in a high current flow, causing the MCB to trip. In contrast, in an insulated neutral system, a short circuit would not allow the current to flow, preventing the MCB from tripping.

💡Isolating Transformer

An isolating transformer is used to electrically isolate one part of a circuit from another, typically to prevent the flow of fault currents. The video mentions that in cases where the neutral is connected to the earth at the substation, an isolating transformer can be used to create an insulated neutral system, preventing the MCB from tripping in the event of a fault.

💡RC (Resistor-Capacitor) Circuit

An RC circuit is a simple electronic circuit composed of a resistor and a capacitor connected in series. In the video, it is suggested that connecting an RC circuit between the neutral and earth can help in maintaining high impedance, thus limiting the current flow in case of a short circuit and preventing the MCB from tripping.

💡Function Continuity

Function continuity refers to the uninterrupted operation of a system or device. The video emphasizes that the insulated neutral system is particularly useful in applications where continuous operation is critical, such as in ships, train engine VFDs, chemical industries, and telecommunication systems.

💡Enclosure

An enclosure in the context of the video refers to a protective casing that is used to house electrical equipment. The video mentions that in an insulated neutral system, the enclosure body is connected to the earth for safety reasons, ensuring that no one can touch the internal components, which could be hazardous.

Highlights

Introduction to the topic of AC supply and the explanation of earth neutral and insulated neutral systems.

Diagrammatic representation of an earth neutral system where the neutral is connected to the earth at the substation.

Definition of an insulated neutral system where the neutral is not connected to the earth.

Explanation of the difference between earthed and insulated neutral systems in terms of fault handling.

Description of how a fault between line and earth in an earth neutral system leads to a high current flow and MCB tripping.

Insulated neutral system's behavior during a fault, where no short circuit current flows and the MCB does not trip.

Practical application of insulated neutral systems in scenarios requiring continuous operation of equipment.

Discussion on the limitations of insulated neutral systems when a second fault occurs.

Explanation of how a fault between line and neutral results in a short circuit current flow in both systems.

The role of a long wire in industrial settings and the potential for insulation failure leading to faults.

Use of an isolating transformer to create an insulated neutral system despite an existing neutral earth connection.

Safety measures in insulated neutral systems, including the use of enclosures and earth connection for safety.

Comparison between earth and insulated neutral systems regarding the impact of not repairing faults promptly.

Applications of insulated neutral systems in industries such as ships, train engine VFDs, chemical industries, and telecommunication where high function continuity is crucial.

The selective use of insulated neutral systems in specific areas when necessary, such as in CRO or DSO supply.

Mention of a related video on DSO oscilloscope use, indicating a broader educational resource.

Conclusion of the discussion on AC supply systems, summarizing the importance of understanding different neutral systems.

Transcripts

Namaste,

Today topic is about AC supply,

I will explain,

what is earth neutral,

and insulated neutral system,

what is the difference between them

and also,

application of an insulated neutral system

An earth neutral system is shown in this diagram,

this is AC supply coming from a substation,

this is a load,

here, neutral is connected to the earth,

at the substation,

here we get the line, neutral and earth,

as neutral is connected to earth here,

at the substation,

not at the home,

so we call it earthed neutral system,

or grounded neutral system,

the insulated neutral system,

is shown in this diagram,

difference between them is,

that in the insulated neutral system,

neutral is not connected to the earth,

here it was connected to the earth,

neutral is insulated from the earth here,

so it is called insulated neutral system,

here we get the line,

neutral and earth

now suppose,

there is a fault between line & earth,

so I will make a fault here,

now line and earth are shorted,

as there is a fault,

so high current will flow,

current will flow like this,

so current path is complete,

so this short circuit current is flowing,

in this MCB also,

so this MCB will trip,

so because of the short circuit,

this MCB will trip,

and we will not have any AC supply,

across the load,

and load supply becomes off,

what happens in an insulated neutral system?

suppose there is short circuit is here,

between line and earth,

but here,

short circuit current will not flow,

see, like this,

there is no return path here,

so current will not flow due to short circuit,

and MCB will not trip,

and we continue to get,

AC supply across the load,

and this equipment will continue to work,

in certain applications,

continuous working of this equipment,

is very much required,

in such applications,

we use insulated neutral system,

because

MCB will not trip during the fault,

and AC supply will remain there for load,

and this equipment will continue to work,

as there is no return path,

for short circuit current to flow,

now I will tell,

the insulated neutral system in detail,

it is shown again here,

here, no-fault,

so we are getting AC supply here,

now suppose there is a fault,

this fault is between line and earth,

in this case also,

as the current can not flow,

as it is open here,

so AC supply will remain there,

MCB will not trip,

this load will continue to work,

I am telling fault between line and earth,

not between line and neutral,

if there is a fault between line and neutral,

then,

short circuit current will flow like this,

and MCB will trip,

and this equipment will not work,

so insulated neutral system is helpful,

if the fault is there between line and earth,

what happens?

there may be very long wire,

in the industry,

od line and neutral,

insulation of these wires may get cut,

or rats will cut the insulation,

so line,

and earth will get connected,

because of the insulation failure,

so fault will be there,

this is a major problem,

in such cases,

the insulated neutral system helps,

now, this was one fault or 1st fault,

now suppose,

another fault or 2nd fault comes.

like this,

now what will happen,

the current flows like this,

so short circuit current will flow,

MCB will trip,

and equipment will stop working,

so this will help,

only for 1st fault,

but for 2nd fault,

this will not help,

and the system will trip,

neutral is floating in this system,

I have shown fault here,

permanently just for explanation,

this fault will not be permanent,

If we connect RC,

between neutral and earth,

like this,

now neutral is not floating,

the values of R and C are such that,

the impedance of this is very high,

so in case of a short circuit,

current will flow like this,

but very less current will flow,

because of high impedance,

so still MCB will not trip,

and load will continue to work,

now, what happens?

this neutral is connected to the earth,

at the substation,

so we have no choice,

even if we don't want,

this neutral earth connection,

but the electricity board will not remove,

this neutral earth connection,

then what to do?

how?

then we connect an isolating transformer,

then we get the line and neutral again,

here,

this neutral is not connected to the earth,

this is load,

in case of a fault,

suppose,

the fault comes here,

but short circuit current can not flow,

see here,

the load current will flow like this,

and like this,

but

short circuit current has to flow like this,

there is no return path,

here the path is there,

but the circuit is not complete,

for fault current,

see

it is open here,

there is no electrical conductor,

so,

if we pit an isolating transformer,

then even there is a short circuit is there,

between line and earth,

short circuit current will not flow,

and the MCB will not trip,

and equipment will continue to work,

so this side is earth neutral system,

this side, insulated neutral system,

now neutral is not connected to the earth,

in the insulated neutral system,

so for the safety reason,

what do we do?

we provide an enclosure,

and enclosure body is connected,

to the earth for safety reason,

and nobody is allowed to touch inside,

now comparison between,

earth and insulated neutral system,

if repairing is not done just after 1st fault,

then 2nd fault will come,

see what happens?

if we do not repair after 1st fault, then

and 2nd earth fault comes,

then,

applications of the insulated neutral system,

the insulated neutral system is used,

where high function continuity is required,

like ships,

train engine VFD,

chemical industries,

telecommunication,

In all these cases,

we do not use,

the insulated system everywhere,

we use it, whenever necessary,

the insulated system also sued in the,

CRO or DSO supply,

we have used it in DSO AC supply,

I made one video also,

on DSO oscilloscope use,

you can watch that,

today, we will close now,