What are the differences between the fixed type and withdrawable type of LV switchgear?

Difference Between Withdrawable And Fixed Circuit Breaker

BOKR ELEC is a manufacturer specializing in MV&LV voltage switchgear assemblies. Customers always feel confused about the difference between withdrawable and fixed circuit breaker. How to choose the right switchgear, fixed vs drawout circuit breaker?

Now let's talk about the difference between fixed vs drawout circuit breaker. Welcome to browse our Product List to choose the suitable circuit breaker.

Withdrawable circuit breaker

Withdrawable or draw out circuit breaker is composed of fixed cabinet body and movable device with switch and other main electrical components. The movable part should be portable when it is transferred, and the positioning after it is moved should be reliable. The drawers of the same type and specification can be interchanged reliably. The processing method of the cabinet body part in the draw-out type is basically similar to that of the fixed cabinet body in the fixed type. However, due to the interchange requirement, the accuracy of cabinet body must be improved, and the relevant parts of the structure should have enough adjustment. As for the movable parts, they should be able to be replaced and the main components should be loaded reliably. Therefore, they should have higher mechanical strength and accuracy, and the relevant parts should have enough adjustment.

Advantage of Withdrawable Circuit Breaker

when a outgoing load is failure and do not need to be like fixed type that must be disconnected from the power supply of the entire cabinet to repair, as long as the withdrawable switchgear pull out the faulted drawer unit for maintenance only, and it does not affect the normal operation for other loads.

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Fixed Circuit Switchgear

fixed circuit switchgear is a non drawout circuit breaker. The utility model can satisfy the fixed position of each electrical component in the cabinet body reliably. The cabinet is usually cubic in shape, such as screen, box, etc. There are also prism, such as desktop, etc. This kind of cabinet is arranged in a single row.

In order to ensure the size and shape of cabinet, it is often adopted that each component is combined step by step. Generally, two pieces or left and right sides are formed first, then the cabinet body is formed, or the cabinet body is first satisfied with the shape requirements, and then the internal parts of the cabinet are connected sequentially. The lengths of the components that make up the edges of the cabinet must be correct (the tolerance is negative), so as to ensure the geometric dimensions of all aspects and the overall shape requirements. For both sides of the cabinet, there should be no uplift in the middle because of the need of arrangement.

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In addition, from the installation point of view, there should be no subsidence at the bottom. In the arrangement and installation, the foundation leveling is a prerequisite, but there are some errors in the dryness and cabinet itself. In the arrangement, the lateral difference should be offset as far as possible, rather than the accumulation of the difference, because the accumulation of the difference will cause cabinet deformation, affect bus connection and assembly installation, stress concentration, and even affect the life of electrical appliances. Therefore, when arranging, it is appropriate to use the highest point of the foundation as the reference point for installation, and then gradually pad the positive expansion. Under the condition of ideal and predictable bottom dryness, it is also possible to adopt the expansion mode from the middle to both sides to make the accumulated difference evenly distributed.

In order to adjust easily and offset the accumulation of tolerances, the width tolerances of cabinets are negative. After each component combination of the cabinet is completed, it should be shaped as necessary to meet the requirements of the shape, position and size of each part. The fixture should be used to ensure the correct unification of the structure, the base plane of the fixture should be taken as the proper bottom surface, and the locating blocks in the fixture should be arranged according to the convenience of taking out the work. The external doors of the cabinet are easily affected by transportation and installation. Generally, the fixture should be adjusted uniformly during installation.

The Technological Characteristics Of Drawer-type Low-pressure Cabinet 

? Unified reference standard is needed for both fixed and movable parts;

? Relevant parts must be adjusted to the best position, and special standard tooling should be applied when adjusting, including standard cabinet body and standard drawer;

? Error of key dimensions should not exceed tolerance;

? Interchangeability of drawers of the same type and specification should be reliable.

10KV AC Drawout Type Switchgear

Fixed Or Withdrawable Circuit Breaker

These aspects are less easy to pin point as they are not simply yes or no decisions. How to make the right choice between fixed or withdrawable medium voltage switchgear when selecting a new equipment for power substation? These important aspects can influence the finial decision:

? Operational friendliness

Medium voltage switchgear should have a user-friendly interface. It should be clear, simple, fluid and aesthetically pleasing. While operators won't directly mention this as an important factor, it will certainly be evaluated on a less conscientious level.

Most importantly, the operation of the switchgear allows to switch the protocol used on the site where it will be installed. For example - some sites only allow cable voltage testing with the doors closed.

? Risk reduction

Safety is reducing risk to an acceptable level. The switchgear needs to accommodate any further safety requirements that are needed to  enable to reduce the risks to an acceptable level. These additional requirements can be different per situation.

? Visual separation to reduce risk

Some users will require visual separation to reduce risk. The main advantage of the withdrawable system is the clear visual separation of the switchgear.

? Skilled operators

Modern switchgear designs are no longer "operator sensitive" and require less skill to operate safely. The increased number of operations performed by less skilled operators necessitates an assessment of "ease of operation" taking into account available operators.

? Site culture

Site culture varies from each company or plant. Often a bundling of knowledge, experience and best-practice for there particular use. Although this site culture varies from site to site there are some similarities with in petrochemical industry sites: low voltage motor control centers have withdrawable motor startes and high voltage installations are based on fixed breakers.

? Maintenance

To perform maintenance the breaker involved need to be disconnected from the supply. The increasing demand on the availability of the supply makes it hard to organize a planed outage. With a withdrawable system it is possible to perform the maintenance on a breaker with a minimized effect on the total switchgear.

? Process control

Petroleum and Chemical Industry systems are controlled by a centralized process control. The centralized process control is connected to all devices within the process and in many cases the medium voltage switchgear needs to be connected to it as well. Centralized process control primary task is to control the process and requires only basic information from the medium voltage switchgear. Information like statuses: on, off, isolated, earthed, test, withdrawn and fault.

? Environment

Increasingly users have to consider the environmental impact of equipment, both during manufacture and service, as well as after its life time. In respect to the design, of a medium voltage switchgear, the vision "the least number of components, the better" applies, since every part must be manufactured and therefore it has an impact on the environment. They need to be safe for personnel and the environment – not just during use, but at the end of service life too! So that they can be completely recycled at the end of it's life without any problem.

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BOKR ELEC focus on manufacturer LV switchgear for many years. With strong R&D competence and technology development, we can provide you high quality and updated fixed circuit breaker and withdrawable circuit breaker with good price. Welcome to contact us for further information you need, and we also would like to help you out for your business with best solution. Choose us and we will satisfy you with our products and services.