Tn C System
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TN-C-S Earthing System
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Kannan Under Secretary to Government. Anandaraj Under Secretary to Government. Ashok Kumar System Manager. Send us a message. Name: Email: Telephone: Message: Submit. Find us here. Contact Us. In TN mode power supply system, it is divided into TN-C and TN-S according to whether the protection zero line is separated from the working zero line. In the TN system, the exposed conductive parts of all electrical equipment are connected to the protective line and connected to the ground point of the power supply. This ground point is usually the neutral point of the power distribution system.
The power system of the TN system has one point that is directly grounded. The exposed electrically conductive part of the electrical device is connected to this point through a protective conductor. The TN system is usually a neutral-grounded three-phase grid system. Its characteristic is that the exposed conductive part of the electrical equipment is directly connected to the grounding point of the system. When a short circuit occurs, the short-circuit current is a closed loop formed by the metal wire. A metallic single-phase short circuit is formed, resulting in a sufficiently large short-circuit current to enable the protective device to act reliably to remove the fault.
If the working neutral line N is repeatedly grounded, when the case is short-circuited, part of the current may be diverted to the repeated grounding point, which may cause the protection device to fail to operate reliably or to avoid the failure, thereby expanding the fault. In the TN system, that is, the three-phase five-wire system, the N-line and the PE-line are separately laid and insulated from each other, and the PE line is connected to the housing of the electrical device instead of the N-line. Therefore, the most important thing we care about is the potential of the PE wire, not the potential of the N wire, so repeated grounding in a TN-S system is not a repeated grounding of the N wire. If the PE line and N line are grounded together, because the PE line and N line are connected at the repeated grounding point, the line between the repeated grounding point and the working ground point of the distribution transformer has no difference between the PE line and the N line.
The original line is the N line. The neutral current that is assumed is shared by the N line and the PE line, and part of the current is shunted through the repeated grounding point. Because it can be considered that there is no PE line on the front side of the repeated grounding point, only the PEN line consisting of the original PE line and N line in parallel, the advantages of the original TN-S system will be lost, so the PE line and N line cannot be Common grounding.
Due to the above reasons, it is clearly stated in the relevant regulations that the neutral line ie N line should not be grounded repeatedly except for the neutral point of the power supply. IT mode power supply system I indicates that the power supply side has no working ground, or is grounded at high impedance. The second letter T indicates that the load side electrical equipment is grounded. The IT mode power supply system has high reliability and good security when the power supply distance is not long.
It is generally used in places where no blackouts are permitted, or places where strict continuous power supply is required, such as electric power steelmaking, operating rooms in large hospitals, and underground mines. The power supply conditions in underground mines are relatively poor and the cables are susceptible to moisture. Using the IT-powered system, even if the neutral point of the power supply is not grounded, once the device is leaking, the relative ground leakage current is still small and will not damage the balance of the power supply voltage.
Therefore, it is safer than the neutral grounding system of the power supply. However, if the power supply is used for a long distance, the distributed capacitance of the power supply line to the earth cannot be ignored. When a short-circuit fault or leakage of the load causes the device case to become live, the leakage current will form a path through the earth and the protection device will not necessarily act.
This is dangerous. Only when the power supply distance is not too long is it safer. This type of power supply is rare on the construction site. For example, T means that the device shell is grounded. It has no direct relation with any other grounding point in the system. N means that the load is protected by zero. For example, C indicates that the working neutral line and the protection line are one, such as TN-C; S indicates that the working neutral line and the protection line are strictly separated, so the PE line is called a dedicated protection line, such as TN-S. In an electrical network, an earthing system is a safety measure that protects human life and electrical equipment.
As earthing systems differ from country to country, it is important to have a good understanding of the different types of earthing systems as the global PV installed capacity continues to increase. This article aims at exploring the different earthing systems as per the International Electrotechnical Commission IEC standard and their impact on the earthing system design for Grid-Connected PV systems. Purpose of Earthing Earthing systems provide safety functions by supplying the electrical installation with a low impedance path for any faults in the electrical network. Earthing also acts as a reference point for the electrical source and safety devices to correctly work. Earthing of electrical equipment is typically achieved by inserting an electrode into a solid mass of earth and connecting this electrode to the equipment using a conductor.
There are two assumptions that can be made about any earthing system:. Earth potentials act as a static reference i. Herbert H. Robert C. Pelt, Et Al. Richard E. Benjamin Et Al. Emergency Medical Care Facilities, P. Division Of Tenncare, Et Al. Millard Ellis Spurgeon v. In Re Elijah H. Jabari Reynolds v. Prentis S. Lee v. State of Tennessee v. Rufus Stevens. Ralph Junior Lowe v. Roy Province et al. Earlesa McClellan. Mario Bowles v. Jacobe Lamone Snipes. Myron Lorenzo Johnson v. Shaughn Walker. Shaughn Walker - Dissent. Thomas S. Zachary Smith. Proposed Rules Proposed Rules The Supreme Court proposes changes to court system rules and solicits feedback from the bench, bar and public.