Major topics
- what is the grounding system
- why is it important for electricity to be grounded
- components related to grounding
- ungrounded system
- types of grounding
What is a grounding system
In an electrical network, the circuitry which provides a path between the parts of the circuit and the ground is known as the grounding system. The ground is essential for the reliable operation of the electrical equipment such as generator, transformer, power system tower… Electrical equipment must be grounded they are grounded in such a way that the equipment voltage will be the same as the ground and it is called as equipment grounding. In case of power transmission and distribution grounding is inevitable, the towers in the transmission system are grounded by an earth electrode.
Why is it important for Electricity to be grounded
- Personal safety can be improved
- Protection of Electrical equipment
- Location of ground fault can be detected easily
- Frequency of faults can be reduced
- Lightning protection
- Electrostatic accidents can be eliminated – static electric currents could create interference of electronic devices and it can generate fire near any flammable object but by using grounding method the static current can be released to the earth.
- It can reduce electromagnetic interference
- Reduction in maintenance cost and time
Components related to grounding
Grounded conductor
A system or circuit conductor which will be intentionally grounded, it is also known as the grounded conductor on a neutral wye system.
Grounding conductor
It is a conductor which is used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes
Grounding electrode
It is a device which is used to establish an electrical connection to the earth
Grounding electrode conductor
It is a conductor which is used to connect the grounding electrode to the equipment grounding conductor, to the grounded conductor, or to both at the service
Grounding conductor equipment
It is the conductor which is used to connect the non-current carrying metal parts of the equipment
What is an ungrounded system
It is a system of conductors in which there is no intentional connection to the ground, ungrounded systems are grounded through distributed capacitance. In this system, the ground fault is very low and it can provide better reliability in faulty conditions. Ungrounded systems are used where service continuity is an important factor and the tripping the power distribution system off-line during the ground fault will be a problem. In this system, there is no grounding only the capacitive coupling from the power system conductors and equipment to the earth.
Advantages of ungrounded power system
Low fault current for a line to ground faults, no arc flash hazard for ground faults, there won’t be any interruption to power distribution during a first ground fault.
Disadvantages of ungrounded power system
It is difficult to locate ground faults and severe transient over-voltages is possible during ground faults. Maintenance coast will be high due to the labor and downtime locating ground faults. Second ground fault on another phase will result in phase to phase fault.
Types of grounding
Solidly grounded system
It is usually used in wye systems and this method is mostly used in the industrial, commercial and institutional power distribution system. in this method, the neutral is connected to the ground and thus it could ensure the neutral voltage is equal to the ground, by doing this method properly there won’t be any phase to ground over-voltages.
The neutral points of high voltage equipment like the transformer and generator are solidly grounded to reduce the insulation voltage level, it has a high value of current ranging from 10-20KA. This method can reduce the line to ground fault transients and it can locate faults easily
Resistance grounding
The resistance grounding is divided into two types high and low resistance grounding, the high resistance grounding system is done by connecting a high resistance in between the neutral point of a low voltage transformer and the ground. The high grounding system is used for small and medium industry applications where continuous operation is needed during the fault condition
Low resistance grounding is done by connecting a small value of resistance to the grounding conductor or the rod it is mostly used for the load which is connected below to 220v supply
Reactance grounding
In this method, a reactor is connected between the neutral point and the ground and the magnitude of the ground fault current can be reduced by changing the reactance. But this method is not used now because of the high transient voltage that appears during the ground fault condition
Resonant grounding
This method is also known as Peterson grounding because Peterson developed a coil which can limit the earth fault current in the undergrounded three-phase system. The coil will be in series with the line to the ground capacitance of each phase conductor and it is tuned to produce an impedance based on the series LC circuit and the coil will be adjusted according to what it is connected.
