Diverted Neutral Current - Description Overview Part 1
TLDRThis video delves into the concept of diverted neutral current, a phenomenon where electrical current intended for the neutral conductor takes an unintended path outside of an electrical installation. The discussion emphasizes the importance of understanding this issue for safety, especially when working with main bonding conductors and earthing conductors. It explains how such currents can arise normally in TNC-S systems due to extraneous conductive parts, but also highlights the potential dangers when supply network issues occur, such as open combined neutral and Earth conductors. The video concludes with a preview of a future demonstration using a test rig to illustrate these concepts safely.
Takeaways
- 🌐 Diversion of neutral current is a phenomenon where current that would normally flow in the neutral conductor is redirected along a different path outside of an electrical installation.
- 🔍 The issue of diverted neutral current is especially relevant to be aware of in the context of safety concerns and potential faults in the supply network, not within individual circuits or buildings.
- 💡 Problems within the supply network, such as issues with the TNCS system (mainly used in the UK), can lead to unsafe situations, including the presence of diverted neutral current.
- 🏠 In TNCS systems, the neutral and earth are combined into a single conductor (CNE), which is separated within the installation but combined externally up to the property boundary.
- 🔗 Extraneous conductive parts like water or gas pipes need to be bonded to the main earthing terminal to maintain equal potential and prevent electric shocks when in contact with them.
- ⚡ Even under normal operation, some current diversion is expected due to the presence of parallel paths for current return in TNCS systems, which is a result of the bonding of extraneous conductive parts.
- 🛠️ When working on electrical installations, it is crucial to first disconnect the supply and use a clamp meter to check for current on bonding conductors before proceeding with any alterations.
- 🚨 If a significant amount of current is detected on a bonding conductor, it may indicate a fault within the supply network, and further investigation is required.
- ⚠️ Disconnecting bonding or earthing conductors can reveal dangerous voltages if there is an issue with the supply network, hence always check for voltage after disconnection as a safety measure.
- 📈 The presence of current on bonding conductors alone does not necessarily indicate a problem; it is the context, the level of current, and the presence of voltage post-disconnection that provides a clearer indication of potential faults.
- 🎥 For a more comprehensive understanding, demonstrations and tests in controlled environments, such as a simulated setup, can be used to safely illustrate the concepts and scenarios related to diverted neutral current.
Q & A
What is diverted neutral current?
-Diverted neutral current, also known as neutral current diversion, refers to the flow of current that would normally be in the neutral conductor but has been redirected to another path outside of an electrical installation.
Why is it important to be aware of diverted neutral current?
-Being aware of diverted neutral current is crucial because it can lead to unsafe situations at the supply point or in other areas. This issue arises from problems within the network itself and not within individual circuits, making it a potential hazard that needs to be addressed.
What is the difference between TNC and TNC-S systems?
-TNC systems have a combined neutral and Earth conductor (CNE) that runs from the supply to the property boundary, where it is separated into individual neutral and Earth conductors. TNC-S systems, on the other hand, maintain the separation of neutral and Earth conductors throughout the supply network and into the property.
What are extraneous conductive parts and why are they bonded?
-Extraneous conductive parts are conductive materials that are not part of the electrical installation but could potentially conduct electricity, such as water pipes, gas supplies, or metal building frames. They are bonded to the main earthing terminal to ensure they are at the same voltage as the electrical system, preventing electric shocks when in contact with them.
How does the normal operation of a TNC system result in diverted neutral current?
-In a TNC system, the presence of parallel paths for current return, such as the bonding conductor to extraneous conductive parts, can result in a分流 of current. This is normal operation and does not indicate a fault.
What should be done before disconnecting earthing and bonding conductors?
-Before disconnecting earthing and bonding conductors, one should turn off the supply to the installation and use a clamp meter to check for any current flowing through the conductors. This is a standard safety procedure to prevent working on live parts.
What are the potential dangers of disconnecting bonding conductors with current flowing through them?
-Disconnecting bonding conductors with current flowing through them can result in dangerous voltages appearing at the disconnected end. This could lead to electric shocks or even ignition of stray gas, posing a significant risk to anyone working on the installation.
How can you determine if the diverted neutral current is due to normal operation or a network problem?
-By measuring the current with a clamp meter before disconnecting and checking for voltage after disconnecting. If there is no voltage after disconnecting, it is likely due to normal operation. However, if there is a significant voltage present, it indicates a network problem that needs to be investigated.
What is the significance of the test facility mentioned in the script?
-The test facility is designed to simulate various scenarios involving diverted neutral current without the risks associated with working with live voltages. It allows for safe demonstration and study of these phenomena, which would otherwise be dangerous or impossible to replicate in a real-world environment.
Why is it important to check all bonding conductors before disconnecting?
-Checking all bonding conductors is important to ensure that no current is present that could indicate a network issue or potential hazard. It helps to identify any abnormal conditions before proceeding with disconnection and any subsequent work.
What should be done if a significant voltage is found after disconnecting a bonding conductor?
-If a significant voltage is found after disconnecting a bonding conductor, the conductor should be reconnected immediately and a professional should be called to investigate the network. This is a clear indication of a problem that needs to be addressed to ensure safety.
Outlines
🔌 Introduction to Diverted Neutral Current
The video begins with an introduction to the concept of diverted neutral current, explaining that it refers to current which would normally flow in the neutral conductor but is instead directed elsewhere. The speaker, JW, clarifies that this phenomenon occurs outside of individual electrical installations, such as buildings, and is due to issues within the supply network itself. The potential dangers of such diverted current are highlighted, emphasizing the importance of understanding how these situations arise and what to look for to ensure safety. JW also previews the content of the next video, which will include a demonstration using a test rig to simulate various scenarios involving diverted neutral current.
🏠 Understanding TNCS and Diverted Neutral Current
This paragraph delves into the specifics of TNCS (Terra Neutral Combined with Earth and Screen) systems, which are common in the UK and many other places. The speaker explains the setup of TNCS, where a single conductor serves as both the neutral and Earth conductor. The paragraph discusses how in normal operation, current may naturally be diverted through extraneous conductive parts like water or gas pipes, which are bonded to the main earthing terminal to maintain equal potential. The speaker also addresses the potential for current to flow through bonding conductors even when an installation is isolated, due to parallel paths created by adjacent properties sharing metallic parts.
💡 Current Distribution in TNCS Systems
The speaker further explores the behavior of current in TNCS systems, particularly when there are multiple paths for current to return. He explains that the presence of a bonding conductor to a shared metallic part like a pipe can result in a分流 of current, with some of it traveling through the pipe and into the ground. This is a normal occurrence in TNCS systems and does not indicate a fault. The speaker also discusses the implications of a broken or disconnected neutral and Earth conductor, which could lead to current being diverted through other paths and potentially causing issues in adjacent properties.
🛠️ Working Safely with Diverted Neutral Current
In this paragraph, the speaker advises on safe practices when working with electrical installations that may have diverted neutral current. He emphasizes the importance of first disconnecting the supply and using a clamp meter to check for current on bonding conductors before making any alterations. The presence of current could indicate a problem within the supply network, and the speaker warns that disconnecting a bonding conductor could result in a dangerous voltage if there is an open combined neutral and Earth conductor elsewhere in the network. The speaker stresses the need to check for voltage after disconnecting any bonding or earthing conductors to ensure safety.
🚨 Dealing with Open CNA Conductors and Safety Precautions
The speaker discusses the rare but serious issue of open CNA (Combined Neutral and Earth) conductors, which can pose significant safety risks. He explains that while such occurrences are not common, they do happen and must be taken seriously. The speaker advises using a clamp meter to measure any current on bonding or earthing conductors and a single pole voltage indicator to check for voltage after disconnecting these conductors. He warns that any significant voltage detected could indicate a major problem and the need to call in professionals to investigate the network. The speaker concludes by reiterating the importance of safety measures and the potential dangers of diverted neutral current.
Mindmap
Keywords
💡Diverted Neutral Current
💡TNCS (Terrestrial and Neutral Conductor System)
💡Bonding Conductor
💡Earthing Conductor
💡Extraneous Conductive Parts
💡Clamp Meter
💡Voltage Indicator
💡Combined Neutral and Earth (CNE) Conductor
💡Open Combined Neutral and Earth Conductor
💡Safety Procedures
💡Normal Operation
Highlights
Introduction to the concept of diverted neutral current and its implications for electrical safety.
Explaining that diverted neutral current occurs outside of an electrical installation, in the supply network itself.
The importance of understanding diverted neutral current for safety reasons, as it may lead to unsafe situations.
Overview of the different terminologies used for diverted neutral current in various regions.
Explanation of TNCS (Three Phase, Neutral and Earth Combined, Separated) as the most common type of supply network.
Description of how the structure of TNCS systems can lead to diverted neutral current through extraneous conductive parts.
The concept of equipotential bonding to maintain the same voltage level between conductive parts and the main earthing terminal.
Discussion of normal operation current flow and how it differs from diverted neutral current due to supply network problems.
The potential dangers of working on electrical installations with undetected diverted neutral current.
The use of clamp meters to detect current on bonding conductors as a safety measure before disconnecting.
The significance of measuring the voltage at the end of a disconnected bonding conductor to identify potential issues.
Explanation of how an open combined neutral and Earth conductor can lead to significant safety hazards.
The rarity of open CNA conductors despite the potential risks they pose when present.
The importance of checking all bonding conductors for current flow before disconnecting for safety.
The potential for significant voltage to appear on disconnected conductors and the need for caution.
The role of testing devices in safely demonstrating the effects of diverted neutral current without the risks of high voltage.
A preview of the next video, which will feature a practical demonstration of diverted neutral current in a simulated environment.
Transcripts
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