Single Earthed Neutral and Multi Earthed Neutral.

SINGLE EARTHED NEUTRAL AND MULTI EARTHED NEUTRAL.

SINGLE EARTHED NEUTRAL AND MULTI EARTHED NEUTRAL:

In Distribution System Three Phase load is unbalance and non linear so The Neutral plays an important role in Distribution system. * Generally, distribution networks are operated in an unbalanced configuration and also service to consumers. This causes current flowing through neutral conductor and voltage dropping on neutral wire. The unbalance load and excessive current in neutral wire is one of the issues in three phase four-wire distribution systems that causes voltage drop through neutral wire and makes tribulations for costumers. The existence of Neutral earth Voltage makes unbalance in three phase voltages for three phase customers and reduction of phase to neutral voltage for single phase customers. * MULTI-GROUNDED three-phase four-wire service is widely adopted in modern power distribution systems due to having lower installation costs and higher sensitivity of fault protection than three-phase three-wire service. The neutrals play an important role in power quality and safety problems. * The multi grounded neutral system is the predominant electrical distribution system used in the United States. * It allow an uncontrolled amount of electric current to flow over the earth unrestrained, posing the potential of harm to the public and to animals causing electric shocks and is presumed responsible for undetected electrocutions. * The protective grounding used in low voltage,600-volt and below, applications will be described and used to explain the hazards involved with the present day multi grounded neutral distribution System, used in the United States. This will allow the reader to see the parallels between the safe low voltage distribution system and the dangerous medium voltage multi grounded neutral distribution system. * The reasons for the development of the three phase, four-wire, multi-grounded systems involve a combination of safety and economic considerations. The three-phase, four-wire multi-grounded design has been successfully used for many years and is well documented in the standards including the National Electrical Code (NEC). * It is Crucial decisions to adopt Multi Grounded Neutral System “save money” by the adoption of the multi grounded neutral electrical distribution system in the cost of the public’s safety.

MULTI GROUNDED NEUTRAL SYSTEM (MEN):

Fig shows the multi-grounded neutral systems commonly used by the electric utilities in North America. The neutral grounding reactor is used by some utilities to reduce the available ground fault current while at the same time still maintaining an effectively grounded system. * The multiple earthed neutral (MEN) system of earthing is one in which the low voltage neutral conductor is used as the low resistance return path for fault currents and where its potential rise is kept low by having it connected to earth at a number of locations along its length. The neutral conductor is connected to earth at the distribution transformer, at each consumer’s installation and at specified poles or underground pillars. The resistance between the neutral conductor of the distribution system and the earth must not exceed 10 ohms at any location. * NEC Article 250 Part X Grounding of Systems and Circuits 1 kV and Over (High Voltage) * (A) Multiple Grounding: The neutral of a solidly grounded neutral system shall be permitted to be grounded at more than one point. * (B) Multi-grounded Neutral Conductor: Ground each transformer, Ground at 400 m intervals or less, Ground shielded cables where exposed to personnel contact.

SINGLE GROUNDED NEUTRAL:

Fig Show Single Grounded Neutral Which is different from Multi Grounded System .Figure shows the neutral also connected to earth, but the neutral conductor is extended along with the phase conductors. The configuration shown in figure allows electrical loads, transformers to be placed between any of the three phase conductors, phase-to-phase and/or phase-to-neutral. * This connection, phase to neutral will force electric current to flow over the neutral back to the transformer. So far, this electrical connection is acceptable, as long as the neutral is insulated or treated as being potentially energized, but modifications will be made in the future that will negate safety for the public and animals. * The ground connection would typically be located in the distribution substation. This may appear insignificant, but the differences are significant

ADVANTAGES OF MULTIPLE GROUNDED NEUTRAL SYSTEMS:

(1) Optimize the Size of Surge Arrestor:

Surge arresters are applied to a power system based on the line-to-ground voltage under normal condition and abnormal…