The power system deals with voltage above 36KV, is regarded as high voltage. Since the voltage level is high, the arcing formed during switching operation is also quite high. Therefore, special care is to be taken during the designing of high voltage switchgear. High voltage circuit breaker is the major component of HV switchgear, thus high voltage circuit breaker ought to have special features for reliable and safe operation. Switching operation and faulty tripping of high voltage circuit are very rear. At time these circuit breakers remain, at ON state, and might be operated after a long period of time. Thus CBs must be dependable enough to make sure of safe operation, as when necessary. High voltage circuit breaker technology has changed drastically in the last 15 years.
SF6 circuit breaker, air blast circuit breaker and minimum oil circuit breaker are mostly used for high voltage switchgear. Vacuum circuit breaker is hardly used for this purpose since till date vacuum technology is not sufficient for interrupting very high voltage short circuit current. There are two kinds of SF6 circuit breaker, that is, single pressure SF6 breaker and two pressures circuit breaker. Single pressure system is the latest and updated high voltage switchgear system, these days. Nowadays SF6 gas as arc quenching medium has become most accepted for high and extra high voltage electrical power system. Though, SF6 gas has strong influence on the greenhouse effect. It has 23 times stronger influence on the greenhouse effect, than that of CO2. Therefore, leakage of SF6 gas in the service life of circuit breaker should be prevented. For minimizing the emission of CF4 – SF6, N2 – SF6 and SF6 gas mixture, might be used in circuit breaker in future, as an alternate of pure SF6. It should always be taken into consideration that, no SF6 gas comes out in atmosphere throughout the maintenance of CB.
Switch boards, comprising the Main LV switch board, also known by the acronym MLVS are vital to the dependability of electrical installation. It must act in accordance with the set guidelines that govern the construction and design of LV switch gear congregations.
A switchboard is the point at which an incoming power supply segregates into separate circuits, each of that is controlled and protected by the switchgear or fuses of the switchboard. Switchboard is partitioned into a couple of functional units, comprising all the mechanical and electrical elements that contribute to the fulfillment of a given purpose. It symbolizes a key link in the constancy chain.
Therefore, the type of switchboard should be perfectly modified to its application. Switchboard Manufacturers must note that the construction and design must comply with working practices and applicable standards.
The switchboard enclosure offers dual protection:
- Security of switchgear, indicating relays, fusegear, instruments, etc. against vibrations, mechanical impacts and various other external influences are prone to interfere with operational integrity (dust, EMI, vermin, moisture, etc.)
- The defense of human life against the possibility of direct and indirect electric shock.
Modern industrial switchboards are sternly fabricated with metal enclosed design construction; no energized parts are easy to get while the panels and covers are closed. Earlier, open switchboards were made with switches and several other devices were mounted on panels fabricated of ebony, granite or slate asbestos board. Metal enclosure of switchboard is linked to earth ground for personnel protection. Large switchboards might be unattached floor mounted enclosures with stipulation for incoming connections at the top or bottom of the enclosure. Switchboard may perhaps have incoming bus duct or bus bars for the source connection and for large circuits fed from the board. Switchboard might include a control or metering compartment estranged from the power distribution conductors.
Electrical Substation, a part of an electrical transmission, distribution and generation system’s main concern is encountering is its cost and reliability. An apt design attempts to strike a balance between the two sub stations, to attain reliability without a high cost. The design must also allow growth of the station, whenever obligatory.
Selection of the location of Electrical Substations must consider a lot of factors. Adequate land area is obligatory for installation of equipment with obligatory clearances for electrical protection, and for access to preserve large electrical machines like transformers. Where the land is expensive, like in urban areas; gas insulated switchgear may perhaps save money. The location or the spot must have room for expansion because of the load growth or premeditated transmission additions. Ecological effects of the substation should be considered, like, road traffic, noise and drainage effects. Earthing or grounding system ought to be designed. The total ground probable rise, and the gradients in probable throughout the fault (known as “touch” and “step” potentials), have got to be calculated to defend passers-by throughout the short-circuit in the transmission system. The substation locations have got to be rationally central to the distribution area to be provided. The location should be secure from intrusion by passers-by, together with protecting people from harm by arcs or electric shock, and to defend the electrical system from disoperation because of vandalism.
The primary step in planning a substation layout is the planning out of one line diagram that shows in simplified form the switching and protection requisite display and the incoming supply lines and transmission lines or outgoing feeders. It is a general practice by several electrical utilities to chart out one-line diagrams with principal elements, such as, switches, lines, transformers, circuit breakers set on the page similarly to the way the apparatus would be laid in the definite station.
Electrical switchgear is a term that comprises of all the switching devices related with mostly the power system protection. Switchgears in substations are situated on both the low voltage and high voltage side of large power transformers. The switchgear on the lower voltage side of the transformers may perhaps be located in the building, with medium voltage circuit breakers for distribution circuits, all along with protection, control and metering equipment.
Medium Voltage Switchgear Application
An arc furnace is necessary to get switch off and on often. The current to be switched might be from 0 to 8 times of the rated current of the furnace. An arc furnace is be switched on and off at its normal rated current up to 2000A, approximately 100 times per day. A normal, oil, air or SF6 circuit breaker is not at all reasonable for this frequent operation. Typical vacuum circuit breaker is most suitable alternative for this frequent high current circuit breaker operation.
One more application of medium voltage switchgear is single phase railway track system. The major function of the circuit breaker is linked with railway traction system, is to disrupt short circuit, on the overhead catenary system that come about frequently and are transitory in nature. Thus circuit breaker used for this purpose must have, short breaking time for short arcing time, small contact gap, VCB and quick breaking is the best probable solution. In fact arcing energy is much higher in the single phase CB than 3 phases CB. It is much lesser in circuit breaker than that in usual circuit breaker. The number of short circuit takes place in the overhead catenary system much higher than those occurring on electrical transmission system. The medium voltage switchgear possessed with vacuum circuit breaker is most appropriate for traction application.
Indeed depressing, the switchboards market has come of age in terms of patents, designs, safety norms and quality. The archetypal and conventional grey market though, is still playing the role of a spoil-sport. They gloss over the quality and safety guidelines to capture the whole market share and cause a serious threat to the business. The contractor, electrical designer and the end user are equally held accountable both legally and professionally for the design and production of the panel board.
The Electrical Switchboard is only a fraction of the total outlay on a complete panel and most generally given the least care, while it comes to the design resulting in rapid halt of operation causing enormous production losses. Imagine developed production unit halted for some specific hours to service the distribution panel!!! The safety guidelines of the operating board safeguard not only the panel but also the other related assets such as, wires, transformers, electronics, machines, etc. and most prominently the precious lives of operators. Thus it is extremely significant that you select the right criteria while designing the electrical switchboard.
A well known research expert from the field once drew a comparison of a fully built panel to the human body with fuses & switchgears analogous to the bus bars, vital organs and other connectivity to the veins and arteries, intelligent system to the brain and nerves and the switchboard to the muscular and skeletal systems!!! There’s no better way to underline the significance of properly designed switchboard !
We have noticed a nerving disagreement of interest with the Electrical design consultants and end users on one and the contractors on the other end, with safety norms and quality railed against blind cost decline drives. Pointless to say safety or technical guidelines must always be of utmost priority in switchboard manufacture.
Electrical panel boards serve like the control centre for several electrical systems like, residential wiring. If the electrical panel is well-made, it is simple to access and added electrical systems can be additional to the panel with time. If the panel is ill designed, several problems can rise. The electrical contractor can be employed to design the panel however the cost can be great. Use few expert design methods to make an electrical panelboard, thereby reducing the cost of employing the contractor or designer.
- Decide the system’s requirements and individual constituents. In residential arrangements, the electrical requirements of a family alter with time. Room additions might be added to the arrangement for extra family members. Electrical panel board should be designed to house these variations. Prepare a record of the immediate requirements and long term goals. If added electrical components need to be added, the panel should be large enough to lodge those constituents. Record all the constituents that will be measured from the panel.
- Have a look at the necessary electrical codes for the project. Even panel’s casing need to be constructed from constituents accepted by the electrical codes. Electrical codes could be assimilated at the State’s Building Standards Commission’s website. Record all the suitable panel material and any statistics referring to the panel’s wiring like breaker loads.
- Make a sketch of the panel board. Initiate by drawing the panel’s face outline. Decide a logical order of locations for the panel’s constituents. Panel components, like, switches, must be grouped in clusters as per the use and easy to access. If the panel controls devices on any side of it, the switches for the devices ought to be clustered consequently. Design the panel so that any switches or controls are located in logical locations.
The non segregated bus duct is fabricated by using top of the line constituents to assure a firm and dependable powers transmit. Bus ducts can be used in range of applications, that is, from switchgear assemblies to unit substations. Enclosure comes in wide range of choices: NEMA 4X, Stainless Steel, aluminum and NEMA 3R.
Baked on Epoxy, the powder coat offers mechanical durability, scratch resistance and meeting the salt spray needs of ASTM B-117. Detachable enclosure covers are firmly fixed bolt, thereby letting easy access.
Non Segregated Phase Bus joints are protected by bolting the bars by using splice plates on both the sides, thereby offering a solid association. Bus bar is complete conductivity with pure copper. Plastic joints every 50 feet in straight bus runs let bus extension while transferring the rated current.
Fluidized bed epoxy insulation is non-hygroscopic in nature and utmost static. It also defies fungus, mold and tracking. Epoxy resin, dissimilar to other insulations, consistently coats bus configuration. Thermal and electrical performance is improved as the epoxy is straightly tied to the bus conductor, removing the air gap found in other buses. It improves heat transfer and avoids corona discharge and insulation damage.
Bus joints are shielded with flame retardant element that is detachable for joint inspections.
- Flexible shunts
- Conductive stub ends
- Fire stops
- Space leads
As per ANSI standards, corona extinction levels are not precise; however they are considered apt for the production type test. Transitory ratings are not specified in the usual; however the duct is predictable to be apt and go with the transitory rating of the equipment to which it is connected. The segregated DC bus duct supposed voltage rating varies from 300 to 3200 volt DC with constant ratings up to 6000A.
Isolated phase duct is moderately special as compared to the other duct systems termed and needs much more space. It is also considerably more costly to buy and install, but considered a unique system for particular applications and, in specific, as a generator duct feed. Generally, rigid conductor type Segregated Phase Bus Duct length is computed from centre line to centre line, and the tools to which it is attached, to form overall duct-length footage. Bar extensions within a termination cubicle are regarded as part of the termination tool. For cable duct, the same measures are used for establishing the length.
The only exemption is 60 inches of duct length should be added for creating overall length dimensions, because of the cable extension leads vital at every end. Such cable lead extensions are measured part of the duct length, somewhat than part of the termination equipment.
Segregated duct that comprises of cable duct basically has the same constant current ratings, from 600A to 6000A. Duct of higher ratings is delivered up to 12000A; nevertheless this is for special applications needing special design, fabricating and installation considerations. Capacities are usually based on 40°C ambient where conductors have silver plated joints, and the permissible temperature rise of the conductor is 65°C. Noncurrent carrying parts that can be voluntarily touched are allowed a 40°C rise. Ambient temperature range limits are -30°C to +40°C, and height is up to 1000 metres (3300 feet). Other ambient situations require special consideration and may perhaps contribute to de-rating.
Voltage range for these kinds of duct is chiefly from above 600V to 34.5kV to ANSI but to 46kV to CSA. In everyday terminologies, the maximum rating is 38kV with a BIL rating of 150kV. It comprises of cable duct, even though cable at supposedly 38kV can have a higher BIL rating and can undoubtedly have higher insulating voltage class, up to 33 per cent insulation on higher voltage ratings.
All the electrical proceedings, electrical wires tend to pass through a component or unit which makes it feasible and practical to go to other units, easily. It is these electrical components that make work easy for the electricity house to easily distribute electricity to every house or single unit. It is the job and task of the electrical components that they effectively make use of the distribution station. The function of these distribution substations is major. The actual and prime usage of these units is to transfer power from the transmission system to the specific area’s distribution system. Hence, the task of Distribution substation could not be easily neglected.
They being the major and important units of the electrical system, they are given the highest authority to perform every single task, efficiently. It is quite extravagant or waste to straight away connect electricity users to the main transmission network, until and unless they make use of large amounts of power. It is because of this reason; the distribution station lessens the voltage to the most appropriate level for the local distribution.
The key functionality behind the use of these substations is not clearly understood. Hence, the function and service rendered by these units should be verified and tested by the electrical houses. The more intricate the functionality, the more complex would be the electrical wire mess. The function being obscure and complex, it is necessary that the personnel engaged in handling these substation is a proficient and competent one. Experts and only skilled professionals should be surcharged of handling the substations. If they are not that experienced, the service rendered by them would not be of that standard and competence. So, if you are factory owner going through this post, ensure that only experienced and skilled personnel are being employed in your unit.
Electric panel board, also known by the name of breaker panel and distribution board is a constituent of an electricity supply system that divides an electrical power feed into its subsidiary circuits, though providing circuit breaker for each circuit or a protective fuse in a common enclosure. Usually, a main switch, and in recent boards, one or more residual current devices (RCD) or residual current breakers with over current protection (RCBO), are also integrated. Depending upon the application, Electric Panel Board is of varied types:
- Factory Assembled Panel Boards
Factory assembled panel boards are available in all common configurations. They are available directly through distributor stock to help cut down the lead times while providing a dependable solution for the light commercial projects.
Panel boards are ideal for lighting and appliance branch circuit protection. Products are designed for sequence phase connection that permits complete flexibility of circuit arrangement (1-, 2- or 3-poles) to allow balance of the electrical load on each phase. The types and kinds of lighting panel boards are Fusible Lighting Panel boards, Pow-R-Line 1a and 2a, Pow-R-Line 3a, Pow-R-Line BCM panel board, Pow-R-Line 1R and 2R and Pow-R-Line 3E.
Column Panels offer a proven design for warehouse, commercial and industrial applications. They measure a compact 8-5/8″ wide by 6″ deep and are easily mounted inside an I-beam for industrial applications. The main breaker lugs could be mounted for top or bottom feed. They are ideal for confined areas or renovation projects.
- Elevator Control Panel board
Control panel boards are designed to meet the stringent requirements commanded by the multiple building codes. These codes are designed to offer fire protection and safety within elevator shafts. The elevator control panel board takes the speculation out of code compliance with respect to the electrical communications and electrical components systems.