Application of Safety Distance of Arc and Waveform Distortion Resistance Test Bench for MCCB

In recent years, with the in-depth construction of new infrastructure in China, the comprehensive transformation of 5G base stations, the wide use of power electronic equipment and the rapid development of photovoltaic power generation, the requirements for traditional low-voltage appliances are getting higher and higher. For industry enterprises in the development and application of pain points, molded case circuit breaker arcing safe distance and waveform distortion resistance testing project, Delta, Delta instrument on the joint to the senior expert teachers to develop two areas in conformity with the requirements of special testing equipment, designed to help enterprises solve the bottleneck of product application, meet user demand, improve the quality of product performance.

Molded case circuit breaker arcing safe distance test stand is mainly for plastic shell type circuit breaker in the process of installation and use, considering safety distance is not enough and can cause harm, such as arcing fault need to study the plastic shell type circuit breaker on the key point in the process of flashover safe distance detection, including the new test connection circuit, the additional requirements and test methods, etc., The arc influence range of plastic enclosure circuit breaker is simulated, and the grade area is divided according to the degree of arc influence, and the corresponding product safety distance reference and installation suggestions are proposed for each are

The hazards of flying arcs

Arc temperature as high as thousands of degrees Celsius, arc itself also has electrical conductivity, the harm is very serious. , switch in the electric power industry electrical jet of arc, may directly spray to the switchgear, distribution panel, such as grounding on metal frame, will cause the metal conductor damage, lines appear abnormal surge voltage, burns operator, fire equipment, make the insulation aging condition, or short-circuit faults, explosion, fire, threatening the safety of lives and property, In petroleum, chemical, mining and other industries, more attention should be paid to the harm of arc.

MCCB produces an arc when its moving contacts and static contacts are separated, and part of the arc or ionized gas kicks out the arc gap from the breaker’s power supply. The arc itself is a huge current. It is easy to cause short circuit and grounding short circuit accidents between C exposed conductor and ground. To ensure safety, the user should keep a distance from the data provided by the manufacturer’s product samples or specifications.

Molded case circuit breaker when breaking large short-circuit current, the dynamic and static contact arc apart, part of the arc or ionized gas arc spraying mouth spews from the circuit breaker power end, itself is a kind of huge current arc, it is easy to cause between the exposed conductive and bare charged body and the “ground” (complete sets of equipment of the metal shell is grounding) of the interphase short circuit and grounding short circuit accident. To ensure safety, the user should leave a certain distance according to the data provided by the manufacturer’s product sample or instruction manual. If the height distance of the distribution box and cabinet is not enough, the products with small arc distance or zero arc can be selected to ensure the safety of electricity use.

Molded case circuit breaker in low voltage distribution system consumption is large, but in the breaking process will produce arc, arc out of the shape of the product into arc, arc is harmful, its detection should meet the relevant standards and provisions, The main methods to reduce the arc distance include improving the structure of contact and arc extinguishing system to improve the performance of arc extinguishing, adopting the arc absorbing device, adopting the current limiting structure, adopting the fourth generation double break point structure, and adopting the vacuum arc extinguishing chamber.

Molded case circuit breaker waveform distortion resistance test stand is mainly in the light of the special application condition of the plastic shell type circuit breaker, according to different classification of typical nonlinear load and harmonic rate distribution, and the test process of simulation experiment, systematic analysis on the test data can simulate various nonlinear harmonic load, impact load, malignant load; Its load curve and power working condition can be programmed in advance according to the test demand, and can be loaded automatically according to the preset running time. The operation of the equipment is simple and flexible, and it has been widely used in electrical laboratory test system and all kinds of power electronic product development test platform.

Harmonic generation device in power system is the harmonic source, is a non – linear electrical equipment. With the wide application of large capacity power electronic devices and various nonlinear loads in the system, the harmonic pollution generated by them has been more and more recognized and paid attention to. In order to suppress the harmonics of the system, we must understand the characteristics of each harmonic source.

Different harmonic sources are divided into:

(1) Current type harmonic source.

The system harmonic source has the characteristics of current source, and its harmonic content depends on its own characteristics and has nothing to do with the system parameters. The rectifier of DC side inductance filter belongs to current type harmonic source.

(2) voltage type harmonic source

MCCB waveform distortion resistance test bench is equivalent to a high-performance power harmonic generator, three-phase independent operation, can work in three-phase, single-phase mode, harmonic times up to 41 times. The phase and amplitude of each harmonic can be programmed independently, which can simulate conventional resistance and inductive load as well as complex nonlinear load. The harmonic caused by different loads in the power network can be simulated and reproduced.

Programming parameters include fundamental wave and harmonic voltage, current, power, phase, amplitude, etc.

The amplitude of impact load is continuously adjustable.

It can realize a simulation of a variety of operating states, such as the duration of the state, voltage, current, power parameters, etc., which can be automatically operated according to the set time.

The current output accuracy is high, the accuracy is up to ±1%, 10A below not less than plus or minus 0.1A;

THD low harmonic (3-5) precision is not more than ±2%, single harmonic deviation is ±8%, single waveform distortion rate content ≥40%, total harmonic distortion rate ≥100%;

At the same time, the equipment has the function of AC energy regenerative load, which can feed back 100% AC energy output of the tested product to the power grid, without generating heat, energy saving and environmental protection.

Waveform repetition function: the load device can be automatically set according to the load waveform file recorded or compiled on the spot, so as to realize the function that only the load waveform can be reproduced on the spot or the required load characteristics.

Load simulation conditions can be configured according to requirements:

1) Can simulate both three-phase load and single-phase load;

2) The voltage, current and power of load fundamental wave and harmonic wave can be configured separately;

3) The fundamental wave and harmonic voltage, current and power can be set respectively amplitude, phase, power factor and other parameters;

4) The amplitude and phase parameters of each harmonic can be set separately, independent of each other, and do not affect each other;

5) The amplitude of impact load can be adjusted continuously;

6) Can realize a variety of operating state simulation, the duration of various states, voltage, current, power parameters;

7) It can be set independently.