The aim was to compare the effect of different geometries in the time required to achieve the extinction of the electric arc. The aim is to propose a new geometry that will improve the operation of the propagation and extinction of the electric arc.
INTRODUCTION 2
More specifically, the costs of technologies such as solar cells and wind power are expected to decrease by 18% and 16% respectively per year. doubling the capacity. Figure 1.3 shows the percentage of renewable energy sources used as primary energy by country in the year 2021.
INTRODUCTION 4
Electricity distribution networks
In the 19th century, Edison's developments built electrical networks to distribute direct current electricity. The AC power supply model shown above is the standard in most countries, with minor differences in voltage and frequency ranging from 100-240 V and 50 or 60 Hz.
INTRODUCTION 6
DC to AC interconnection
If the energy revolution towards renewable sources is to be considered successful, the implementation of direct energy networks or the adaptation of DC-to-AC inverter systems is inevitable. Bidirectional systems supply power to CFE's electrical network with the surplus generated by renewable sources.
INTRODUCTION 8 is divided into six subsystems
For example, the difference in the amount of energy produced by a solar farm and that produced by an individual user installation of solar panels is staggering. The largest solar PV plant today is the Gonghe Photovoltaic Project located in Qinghai, China, with a capacity of 3.1 GW [11].
INTRODUCTION 10 also produce energy in the range of hundreds of megawatts
DC circuit breakers
The International Electrotechnical Commission (IEC) defines low power system voltage as a voltage in the range of 120 to 1500 V for DC systems. Specifically, if the CB is required to operate with DC power in the low voltage range, these circuit breakers are known as DC Low Voltage Circuit Breakers, DC LVCBs or simply LVCBs.
INTRODUCTION 12 The problem of disconnecting the DC electricity flow is more complex than
Research in DC LVCBs
Simulations of an electric arc include the plasma fluid dynamics and electromagnetic interactions of the materials. 4] studied the effects of the number of splitter plates in a simplified LVCB for a 3D magnetohydrodynamic model and validated the methodology with experimental data.
INTRODUCTION 14 was affected by eddy-current effects in the splitter and the electrodes. For
Scope of this work
The main goal of this work is to develop a model capable of replicating the bow behavior. The model will be used to analyze the thermal effects of the arc within the LVCB.
Types of LVCBs
- Molded Circuit Breaker
As current flows through the solenoid coil, it produces magnetic fields that induce Lorentz forces in contact with the ferromagnetic piston. The current tries to continue its path, so an electric arc forms in the gap.
THE DC LOW VOLTAGE CIRCUIT BREAKER 20 with very low conductivity, Joule heating increases the air temperature to
Molded Case Circuit Breaker
The main difference is that the arc runners are drawn, generating the electric arc directly in the extinction chamber and extending the arc in the same process. This method increases the resistance, makes a faster extinction of the arc, but increases the Joule heating and makes the opening velocity the main advantage for this configuration.
THE DC LOW VOLTAGE CIRCUIT BREAKER 22
Other Types
THE DC LOW VOLTAGE CIRCUIT BREAKER 24
An incorrect connection could potentially cause the electric arc to travel completely in the wrong direction, away from the extinguishing chamber. The electromagnet (coil with a ferromagnetic core) uses energy from the arc by passing the current from the fault through the coil.
THE DC LOW VOLTAGE CIRCUIT BREAKER 26
There are many possibilities for modifications in the splitter plates of an extinguishing chamber, such as arrangement, materials and splitter plate shape. They all have a geometry that forms a magnetic field that promotes the arc's motion in the annihilation chamber.
THE DC LOW VOLTAGE CIRCUIT BREAKER 28 An example of this is the patent by Fasano [27], which implements a series of
THE DC LOW VOLTAGE BREAKER 28 An example of this is the patent by Fasano [27], which a series of. THE DC LOW VOLTAGE BREAKER 30This objective of this work is to propose a new geometry based in simulation.
THE DC LOW VOLTAGE CIRCUIT BREAKER 30 This objective of this work is proposing a new geometry based in simulation
Governing Equations
Maxwell's equations are used to solve the magnetic field: Gauss's law, Gauss's law for magnetism, Faraday's law, and Ampere's law.
Fluid Dynamics
❼ The second term is the variation of energy in the domain due to incoming and outgoing flows in the control volume. ❼ The fifth term is a source term used to add energy interactions from other phenomena in the system, such as radiation.
METHODOLOGY 34 Some considerations are taken to add the arc effects, like the Joule heating
Maxwell’s equations of electromagnetism
This states that⃗ the magnetic field B⃗ has divergence equal to zero, which means that it is a solenoidal vector field. This implies that, unlike the electric field, it is impossible to store a magnetic fluxB⃗ in any space.
METHODOLOGY 36 versa
Electric arc formation
This plasma state can be achieved by an intense potential applied to the molecules or by heating a liquid to high temperatures. The structure of the electric arc is divided into three parts; the arc column and the two arc roots (anode and cathode regions) [55].
Arc Behavior
METHODOLOGY 38 an electrical fault, the current increases up to many times the nominal value
METHODOLOGY 40 a low-intensity arc
Arc roots
This behavior is due to the plasma's microscale process and should be described as a non-equilibrium plasma. After the NTE layer, the ionization layer (IL) is formed, this layer exhibits an electron density that is different from the normal plasma.
METHODOLOGY 42 charge sheath (SH). A powerful magnetic field characterizes the SH layer
Magnetohydrodynamics
The arc involves a series of complex processes, therefore several theoretical approaches have been developed to describe the plasma process. Microscopic approaches describe every particle of the plasma; these approaches can explain the many processes in arc plasma propagation phenomena, such as arc roots.
METHODOLOGY 44 Equation (3.13) shows the relation between the mass of the particle m p , the
Another approach is to use a two-fluid model, making one global value for electrons and another for heavy particles, including each species in the system as one. Finally, the simplest plasma model is the one-fluid model, also called the Magnetohydrodynamic (MHD) model.
METHODOLOGY 46
Plasma properties
In the MHD approach, the plasma is treated as a single fluid, making the properties of the air plasma a critical point in the analysis. Although air is composed of many gases, as shown in Table 3.1, calculations of plasma properties only use nitrogen, oxygen, and argon, neglecting all other species.
METHODOLOGY 48
It is possible to calculate a specific heat Cp over temperature differences from a reference state. Equation (3.17) shows this relationship, where the enthalpy H is determined by the enthalpy in the reference state HO with T = 300 K.
METHODOLOGY 50
So, as the air becomes ionized with temperature, the conductivity of the air can be neglected below K. This can be seen in Figure 3.9, where the electrical conductivity is almost zero until it begins to increase the temperature above 5,000 K.
METHODOLOGY 52
The NEC model corresponds to the difference between the radiation emitted on an isothermal sphere and the radiation emitted by other points on the sphere [46][47].
METHODOLOGY 54
Base Design
This work used as a basic design a geometry based on a real circuit breaker used in renewable energy interconnection systems, such as solar panel grid systems and high current DC batteries. Henceforth, in the analysis, the Al electrode will be considered as the cathode and the FE electrode as the anode.
PROBLEM STATEMENT 58
PROBLEM STATEMENT 60 well as the plasma column that will be considered
Simulation Procedure
- Boundary Conditions
CAD drawings for each component can be found in the Appendix section, as well as their dimensions. The exterior walls in the model are considered adiabatic and with a no-slip boundary condition.
PROBLEM STATEMENT 62 The fluid domain is static at the beginning of the simulation
Considerations
PROBLEM STATEMENT 64
Proposed designs
In this case, the splitter plates of the lower part (closest to the anode) were moved by a successive value of mm, relative to the plate in front. This proposal, like the rest of the other proposed new geometries, was based on a simple redesign that does not require any modification of the extinguishing chamber, nor does it increase the mass of materials required, by only changing the arrangement of the splitter plates.
PROBLEM STATEMENT 66
The final geometry proposed in this work (Figure 4.10) is also based on a modification of the original geometry, now with a mm displacement of each splice plate with respect to the plate before it, starting with the 5th and 8th splice plates. respectively. That is, the two splice plates in the middle, the 6th and 7th splice plates, are left in their original positions and used as a reference for the movement of the other splice plates.
PROBLEM STATEMENT 68
Results
Mesh sensibility
The change in error after each increase in the number of mesh elements is shown in Table 5.1. Based on the results of Table 5.1, a mesh of approximately 13 × 106 elements is a good enough mesh that offers a good balance between accuracy and computational costs, given that, beyond this point, the accuracy of the results does not increase by a margin with the number of elements, but the time required to reach convergence at each time step does.
Steady state analysis: Attraction forces in the plasma column
RESULTS 72 Properties for the electrodes and splitter plates are taken at atmospheric
None of the splitter plates are closer than the original, and the resulting magnetic field is the most valuable change that can be observed for each case. The results of the steady-state analysis allow us to calculate the force felt by the plasma in two ways: the force felt by the plasma column in its surface, and the volume force density felt in a line along the center of the plasma.
RESULTS 74 plasma
The results for the surface force felt by the plasma column in the top-displaced and side-displaced geometries are shown in the two figures below. We can note that for these cases, a greater maximum force was not achieved in the general direction of the spacer plates.
RESULTS 76
As a way of condensing the results of the surface forces sensed by the arc, Figure 5.8 shows the bulk force density that can be sensed by a line running along the center of the plasma column, from the cathode to the anode side.
RESULTS 78
Transient Analysis: Arc propagation simulation
The arc propagation process is numerically simulated in ANSYS FLUENT ➤ software, coupled with ANSYS MAXWELL ➤ software, using a User Defined Function (UDF) as the connecting point between them. The propagation of the arc can be better analyzed if we look at the transient behavior of the magnitude of the electric current in the extinguishing chamber.
RESULTS 80
As it is, physically breaking the arc connection will be treated as a successful arc split. Figure 5.10 for the Bottom Displaced geometry shows how the arc propagation process was performed.
RESULTS 82
As a way to better compare the transient behavior of the arc propagation process, the hottest temperature in the plasma column was tracked. ❼ Up to the 120µ mark, the position of the hottest spot is approximately the same for both cases.
RESULTS 84 point of the cathode. The arc in the Original geometry is split at
We can also observe that the original geometry has a sudden drop in mean temperature around the 135 µs mark. This reduced the peak mean temperature at the original geometry (1650 K) and the arc split shortly thereafter.
RESULTS 86 Displaced geometries
RESULTS 88 and Bottom Displaced geometries, respectively
The implementation of a steady state analysis of the electromagnetic forces produced in a plasma column near the splitter plates was proposed as a starting point to choose which geometries have a greater chance of shortening the arc extinction time. A more complete analysis can be performed by performing the transient simulation of the arc propagation process in the rest of the geometries proposed in this work and repeating the simulations for different input current values.
CONCLUSIONS AND FUTURE WORK 90 for the arc extinction of 13.65 %
Magnetic Field
Temperature Distribution
- Original geometry
- Bottom Displaced geometry
Numerical analysis of heat dissipation in DC low voltage circuit breakers (Master's thesis, University of Guanajuato), Mexico. Modeling and analysis of the electric arc in low voltage circuit breakers (Doctoral thesis, Universidad del Pa´ıs Vasco- Euskal Herriko Unibertsitatea).
