Fault Level Calculation Of Eastern Part Of Nigeria 330KV Grid Network Using NEPLAN
Fault in electrical power system can occur as a result of three phase short circuit, single line to ground, two phase to ground short circuit and line to line fault. These very faults, definitely, give rise to fault current.
Fault level calculation studies in power system, is required to know the fault currents in other to provide for necessary information for the selection of switch gears, circuit breakers, setting of relays and stability system operation.
NEPLAN (Network Planning) in power system analysis is software developed by BCP (Bursorello + Cott + Partner) Switzerland used for system modeling and analysis.
Table Of Content
- Title page
- Approval Page
- Table of content
- 1.1 Definition of fault
- 1.2 Classification of faults
- 1.3 Types of fault
- 1.4 Reasons for carrying out fault analysis
2.0 Literature Review
- 2.1 Modeling of Transmission line
- 2.2 Short Transmission line
- 2.3 Long Transmission line
- 2.4 Medium Transmission line
- 2.5 Representation of Transmission line
- 2.6 Per unit system
3.0 Introduction to NEPLAN
- 3.1 Eastern grid network
- 3.2 330KV Transmission line parameters of Double & Single circuit
- 3.3 Transmission line description (Eastern)
- 3.4 Types of conductors used in Transmission line
- 3.5 Types of tower design
- 3.6 Components that make up the project
- 3.7 Eastern Network simulation
- 3.8 Result Analysis
4.0 Nigeria National Grid Network
- 4.1 Generator data for Eastern grid
- 4.2 Power system parameters
- 4.3 Methods of solving unbalancing fault
- 4.4 Sources of fault power
- 4.5 Basic requirements protection system
5.0 Recommendation / Conclusion
An electric power system is made up of generators, transformers, Transmission line and consumer equipment (loads). The system must be protected against the flow of heavy short-circuit currents which can cause permanent damage to the major equipments. And this is achieved by disconnecting the faulty section of the system by means of circuit breakers, switch gears, isolators and protective relays.
The need to know the maximum short-circuit current that can occur at the different points of the system in order that the breakers selected are adequate to withstand the current and operate successfully, to cut the faulty section, and also in order that the protective relays may be selected for correct operation. The design of machines, bus bars, isolators, circuit breakers etc is based on the consideration of normal and short-circuits currents.
It is also important to be able to calculate approximately at least the size of the protective reactors which must be inserted in the system to limit the short circuit current to a value which can be handled by the circuit breakers.
The short-circuit current is an A.C system are determined mainly by the reactance of the alternators, transformers, and lines up to fault in the case of phase-to-phase faults. When the fault is between phase and earth, the resistance of the path plays an important role in limiting the current.
The rupturing capacities of a circuit breakers are based on the symmetrical short-circuit current which is the most simple calculation among all types of short-circuits. However, for determination of setting of relays, it is absolutely necessary to know fault current due to unsymmetrical fault condition for which knowledge of symmetrical components etc is required.
1.1 Definition Of Fault
A fault in an electrical equipment/apparatus is defined as a defect in the electrical circuit to which current is diverted from the intended part.
Also fault is said to have occurred when a system fails to perform the required function at a given time. A fault occurs when two or more conductors that normally operate with a potential difference come in contact with each other or when a conductor that supposed to be continuous losses its continuity.
The nature of a fault simply implies any abnormal condition which causes a reduction to the basic insulation strength between phases conductors or between phases conductors and earth or any earthed screen surrounding the conductors. The reduction of insulation strength is not considered as a fault until it creates some effect on the system i.e, until it results either in excessive current or in between conductor and earth to a value below that of the lowest impedance normal to the circuit.
The possibility of occurrence of abnormal condition or failure is more on the power line.
1.2 Classification Of Faults
Balanced Or Symmetrical Faults
This is a kind of fault that gives rise to symmetrical fault current. In this type of fault, current in three phases are equal and have 120o displacement
Example, when all the three phase of conductors of a three phase line are brought together simultaneously into a short-circuit condition.
Unbalanced Or Unsymmetrical Fault
This is also another type of fault in a power system that gives rise to unsymmetrical fault current. In this case, the line current is unequal and the displacement is unequal.
IY ? IB ? IB
Examples of unbalanced fault.
- A single line to ground
1.3 Types Of Fault
- Three Phase Short-circuit Fault: This type of fault results due to breakdown of insulation between all the three phases or when there is a bridge involving all the three phases at a time. Its occurrence is 2 to 3 percent.
- Single Phase to ground (L-G) short-circuit fault: This is caused as a result of breakdown of insulation between one of the phases and earth. Its occurrence is 70 percent.
- Phase to ground (L-L-G) short-circuit fault: Due to breakdown of insulation between either of the two phases and earth. Its occurrence in power network is 10 percent.
- Phase to Phase (L-L) short-circuit fault: This is a type of short-circuit fault that occur due to the breakdown of insulation between either of the two phases, its occurrence is 15%.
1.4 Reasons For Carrying Out Fault Analysis In The Power System
One of the reasons for carrying out fault analysis in power system is to know the maximum short-circuit current that can occur at different points of a system in order to select a circuit breaker that can adequately withstand the current and operate successfully to cut-off fault section.
The design of machine bus-bars, isolators, circuit breaker etc. is based on the consideration of normal and short-circuit current.
Also to know the size of protective reactor while must be inserted in the system to limit the short-circuit current to a value which can be handled by the circuit breaker or protective devices.
Conclusion And Recommendation
The field of engineering is so complex that both theoretical and practical knowledge should complement each other. Proper scripting of the complexity of this project involving the design, development and construction of the circuit, good knowledge, necessary material, test equipment, accurate component, values and supervision were required in order to arrive at a functioning and successful project. The construction of an under and over voltage tripping circuit ha truly exposed us to some ideas we never thought of before, though it was quite challenging but it has broaden our horizons.
The project serves as a technological development as well as a source of knowledge and skill for the active participation of students sealing in circuit design.
This project plays an important role in protecting our electronic/electrical appliance from under/over voltage conditions which may be useful to the gadgets. Therefore, it is recommended that students in various institutions should embark on this type of project always as it will help to widen their knowledge and increase their skills in the electronic world. For proper protection of appliances/equipment against damages in our various should b used to protect gadget against such damages. In other words, industries that operated on motors should get in touch with this device since it will go a long way to protect their motors from under/over voltage conditions which are unsafe to the motor coils. Under/over voltage conditions in the industries is kept to a tolerable level with the help of the variable resistor that serve as voltage regulators.
Constant seminar/workshops should be carried out in order to enlighten the public on the need to protect electrical/electronics appliances and also, this project is recommended for efficient services (protection).
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