Air Insulated Switch-gear VS Gas Insulated Switch-gear

Air Insulated Switch-gear VS Gas Insulated Switch-gear

Gas Insulated Switch-Gear

Air Insulated Switch-Gear

Limitations of Air Insulated Switchgears (AISs)

• Large dimensions due to statutory clearances & poor dielectric strength of air
• Insulation deterioration with ambient conditions and susceptibility to pollutants
• Wastage of space above
• Life of steel structures
• Seismic instability
• Large planning and execution time
• Grounding-mat is essential for containing touch and step potentials
• Hot line washing and regular maintenance of the substation is essential, requires more spares inventory and man-power

Advantages of GISs over AISs

• Compact space-saving design
• Minimal operating cost
• Minimal weight by lightweight construction
• Safe encapsulation
• Environmental compatibility
• Economical transport
• Reliability
• Smooth and efficient installation and commissioning

Read More

Every Challenge Is An Opportunity

Edison, one of Europe’s oldest power companies, which was founded in 1884 in Milano, owns the Fontanamora hydroelectric plant that generates three megawatts (MW) of renewable power from turbines and auxiliary machinery. The plant is situated at Lombardy by a fast-flowing river at the bottom of a steep gorge. Lombardy lies in the north of the country, sharing a border with Switzerland.

As the second energy company in Italy, and a European leading operator with operations in the supply, production and sales of electric power and hydrocarbons (natural gas and crude oil), Edison has a strong focus on renewable generation. It has 7.7 giga watts (GW) of installed renewable capacity, comprising hydroelectric, wind, solar, thermometric plants and a biomass system.

The challenge

At the beginning of 2013, Edison decided to undertake a complete revamp of the plant, with the project including also the step-up of the voltage level of connection to the electricity grid, from medium to high voltage. The customer decided to replace the previously installed switch gear with a new product featuring the latest in switching technology: ABB's PASS hybrid switch gear module, rated at 72.5 kilo volts (kV).

The project was challenging both technically and from an installation perspective, as access to the powerhouse is only possible by way of a steep, narrow stairway down the side of the gorge. Entrance to the powerhouse is small, and the room available for installing switch gear is only three square meters wide.

Solution with innovative design

To cope with these difficult space challenges, ABB leveraged its expertise in switch gear design to supply a hybrid module that integrates a circuit breaker and two dis-connectors, plus current and voltage transformers – and the control and protection relay in a single unit. 

Plug-in cable terminals instead of traditional air-insulated bushings were deployed to further reduce the module's size, enabling it to fit it in the reduced space of the Fontanamora powerhouse.

Innovative logistics

To overcome the narrow stairway and minimise transport risks, the installation team secured the PASS hybrid module with special harness straps – and lowered it down into the gorge with a crane. The preassembled unit arrived on site pretested for high-voltage and ready for installation, which took four days. There was no need for the additional equipment typically needed to perform on-site high-voltage tests, so the ABB PASS hybrid module could be put into service without delay, saving time and costs.

Read More

RENEWABLE ENERGY DEMAND IN EUROPE REACHES RECORD LEVELS

RENEWABLE ENERGY DEMAND IN EUROPE REACHES RECORD LEVELS

The demand for renewable electricity in Europe, documented with Guarantees of Origin (GO), continued to grow in 2015. The growth is up more than 8% from 2014 and surpassed 340 TWh. Behind this growth are thousands of businesses and millions of households in numerous European countries – voluntarily purchasing renewable electricity documented with Guarantees of Origin.

The market has seen a steady increase in national participants but is still dominated by a select number of countries. The five countries that consume the most renewable energy are Germany, Sweden, Switzerland, the Netherlands and Italy. Together they demand ¾ of the renewable energy used in Europe. The Netherlands is the fastest growing market. From 2014 to 2015 it has grown by a brisk 12%, and consumed more than 42.5 TWh in 2015. Germany is still the largest market with a total volume of 87 TWh in 2015.

The marketplace for Guarantees of Origin is steadily growing in terms of countries, with more than 20 countries actively working with AIB (Association of Issuing Bodies) and fully using EECS, the common European market standard.

Norway, Austria, Finland, Denmark, France and Belgium today make up the next group of countries – each with a steady market demand between 10 and 35 TWh annually. The rest of the national markets are still fairly immature, and together represent only a smaller share of the total market demand.

The AIB statistics include only GOs based on the EECS standard. There are still countries with national certificate markets that have yet to adopt the EECS standard. These markets total more than 100 TWh of additional market demand. This pushes the actual market volume beyond 440 TWh.

United Kingdom and Spain – will they join the European market in 2016?

The development in 2015 follows a record-breaking 2014, during which the market experienced a 27.6 % growth and an all-time high, 314 TWh demand for renewable electricity. Moreover, for the first time since 2011, there was a real balance between supply and demand.

With the UK, Spain and a few smaller countries considering joining AIB, and adopting the EECS standard, there is much discussion and uncertainty concerning how this will affect the market. Both the UK and Spain are countries with a sizable renewable energy generation, as well as a corporate sector that can have strong demand for renewable energy. Wholesale prices have risen significantly the last part of 2015. The question market-players and consumers are voicing is “Will the inclusion of new markets give additional push to the upward price development?”

The European demand for renewable electricity documented by Guarantees of Origin now constitutes more than 13% of all electricity consumption in Europe (ca. 3,200 TWh) and approximately 40% of all electricity generated from renewable sources in Europe (ca. 1,100 TWh).

The above is a commentary based on figures published by AIB (Association of Issuing Bodies).

ECOHZ offers renewable energy solutions to electricity providers, businesses and organizations across Europe, North America and Asia – providing renewable electricity, from a wide range of sources, regions and qualities. Renewable electricity is documented by Guarantees of Origin in Europe, RECs and Green-e in the US, and International RECs (I-REC) in selected Asian markets. ECOHZ also provides a new and innovative solution – GO² – combining renewable energy purchases with the financing and building of new renewable power generation. Companies choosing documented renewable energy can reduce their carbon footprint and improve their sustainability ratings. ECOHZ is among the leading independent suppliers in Europe, and is located in Norway and Switzerland. ECOHZ endeavors to play an active role in the current energy transition through its vision of “changing energy behavior”.

For more information see: http://www.ecohz.com

Read More

Different type of motors...

Different type of motors.....

Squirrel Cage Motor

 

Electric Motor

An Electric motor is a machine which converts electric energy into mechanical energy. Its action is based on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Fleming’s Left-hand Rule and whose magnitude is given by F = BIl Newton.

Types of AC Motors

Classification Based On Principle of Operation:

(a) Synchronous Motors.

1. Plain

2. Super

(b) Asynchronous Motors.

1. Induction Motors:

(a) Squirrel Cage

(b) Slip-Ring (external resistance).

2. Commutator Motors:

(a) Series

(b) Compensated

(c) Shunt

(d) Repulsion

(e) Repulsion-start induction

(f) Repulsion induction

Classification Based On Type of Current:

1. Single Phase

2. Three Phase

Classification Based On Speed of Operation:

1. Constant Speed.

2. Variable Speed.

3. Adjustable Speed.

Classification Based On Structural Features:

1. Open

2. Enclosed

3. Semi-enclosed

4. Ventilated

5. Pipe-ventilated

6. Riveted frame-eye etc. 

Types of DC Motor

Most common DC motor types are-

1. Permanent-magnet motors
2. Brushed DC Motor

a.       DC shunt-wound motor

b.      DC series-wound motor

c.       DC compound motor

                                                              i.      Cumulative compound

                                                            ii.      Differentially compounded

d.      Permanent magnet DC motor

e.       Separately excited

3. Brushless DC Motor
4. Coreless or ironless DC motors
5. Printed armature or pancake DC motors
6. Universal motors

 

 

 

Read More

How to choose transformer rating?

 How to choose transformer rating?

When an installation is to be supplied directly from a MV/LV transformer and the maximum apparent-power loading of the installation has been determined, a suitable rating for the transformer can be decided, taking into account the following considerations:

• The possibility of improving the power factor of the installation
• Anticipated extensions to the installation
• Installation constraints (e.g. temperature)
• Standard transformer ratings.

3-phase transformer

The nominal full-load current In on the LV side of a 3-phase transformer is given by:



where:

• P_a = kVA rating of the transformer
• U = phase-to-phase voltage at no-load in volts (237 V or 410 V)
• I_n is in amperes

Single-phase transformer

For a single-phase transformer:



where

• V = voltage between LV terminals at no-load (in volts)

Simplified equation for 400 V (3-phase load)

• I_n = kVA x 1.4

The IEC standard for power transformers is IEC 60076.

Read More

Degradation of Insulation in Switchgear (What’s Really Happening)

Partial Discharge

Partial Discharge (PD)

Electrical insulation is subjected to electrical and mechanical stress, elevated temperature and temperature variations, and environmental conditions especially for outdoor applications. In addition to normal operating conditions, there are a host of other factors that may trigger accelerated aging or deterioration of insulation.

Switching and lightning surges can start ionization in an already stressed area. Mechanical strikes during breaker operation can cause micro cracks and voids. Excessive moisture or chemical contamination of the surface can cause tracking. Any defects in design and manufacturing are also worth mentioning.

Partial Descharge

PD is a localized electrical discharge that does not completely bridge the electrodes. PD is a leading indicator of an insulation problem. Quickly accelerating PD activity can result in a complete insulation failure.

PD mechanism can be different depending on how and where the sparking occurs:

• Voids and cavities are filled with air in poorly cast current transformers, voltage transformers and epoxy spacers. Since air has lower permittivity than insulation material, an enhanced electric field forces the voids to flash-over, causing PD. Energy dissipated during repetitive PD will carbonize and weaken the insulation.
• Contaminants or moisture on the insulation induce the electrical tracking or surface PD. Continuous tracking will grow into a complete surface flash-over.
• Corona discharge from sharp edge of a HV conductor is another type of PD. It produces ozone that aggressively attacks insulation and also facilitates flashover during periods of overvoltage.

Features of partial discharge activity, such as intensity, maximum magnitude, pulse rate, long-term trend, are important indications of the insulation’s condition.

Healthy switchgear has very little or no PD activity. If PD activity is significant, it will eventually deteriorate insulation to a complete failure. Higher voltages produce higher intensity partial discharges, thus PD detection in gear with higher voltages (13.8 kV and up) is more critical.

Possible locations of partial discharge in switchgear:

1. Main bus insulation
2. Circuit breaker insulation
3. Current transformers
4. Voltage transformers
5. Cable terminations
6. Support insulators
7. Non-shielded cables in contact with other phases or ground

 

Read More

Electrical Switchgear Protection

Definition of Switchgear

A switchgear or electrical switchgear is a generic term which includes all the switching devices associated with mainly power system protection. It also includes all devices associated with control, metering and regulating of electrical power system. Assembly of such devices in a logical manner forms a switchgear. This is very basic definition of switchgear.

Switchgear and Protection

Switchgear

 We all familiar with low voltage switches and re-wirable fuses in our home. The switch is used to manually open and close the electrical circuit in our home and electrical fuse is used to protect our household electrical circuit from over  current  and short circuit faults. In same way every electrical circuit including high voltage electrical power system needs switching and protective devices. But in high voltage and extra high voltage system, these switching and protective scheme becomes complicated one for high fault  current  interruption in safe and secure way. In addition to that from commercial point of view every electrical power system needs measuring, control and regulating arrangement. Collectively the whole system is called switchgear and protection of power system. The electrical switchgear have been developing in various forms.

Switchgear protection plays a vital role in modern power system network, right from generation through transmission to distribution end. The  current  interruption device or switching device is called circuit breaker in switchgear protection system. The circuit breaker can be operated manually as when required and it is also operated during over  current  and short circuit or any other faults in the system by sensing the abnormality of system. The circuit breaker senses the faulty condition of system through protection relay and this relay is again actuated by faulty signal normally comes from current transformer or voltage transformer.

A switchgear has to perform the function of carrying, making and breaking the normal load current  like a switch and it has to perform the function of clearing the fault  in addition to that it also has provision of metering and regulating the various parameters of electrical power system. Thus the switchgear includes circuit breaker, current transformer, voltage transformer, protection relay, measuring instrument, electrical switch,electrical fuse, miniature circuit breaker, lightening arrestor or surge arrestor, electrical isolator and other associated equipment.

Switchgear Panels

 

 

Electric switchgear is necessary at every switching point in the electrical power system. There are various voltage levels and hence various fault levels between the generating stations and load centers. Therefore various types of switchgear assembly are required depending upon different voltage levels of the system.
 

Besides the power system network, electrical switchgear is  also required in industrial works, industrial projects, domestic and commercial buildings.

 

Read More

The Best Applications For VFDs

VFD with induction motor

Advances

The most commonly used motor in building HVAC applications is the three-phase, induction motor, although some smaller applications may use a single-phase induction motor.

VFDs can be applied to both. 

While VFD controllers can be used with a range of applications, the ones that will produce the most significant benefits are those that require variable speed operation. 

For example, the flow rate produced by pumps serving building HVAC systems can be matched to the building load by using a VFD to vary the flow rate. 

Similarly, in systems that require a constant pressure be maintained regardless of the flow rate, such as in domestic hot and cold water systems, a VFD controlled by a pressure setpoint can maintain the pressure over most demand levels.

The majority of commercial and institutional HVAC systems use variable volume fan systems to distribute conditioned air. Most are controlled by a system of variable inlet vanes in the fan system and variable air volume boxes. As the load on the system decreases, the variable air volume boxes close down, increasing the static pressure in the system. The fan's controller senses this increase and closes down its inlet vanes. While using this type of control system will reduce system fan energy requirements, it is not as efficient or as accurate as a VFD-based system.

Another candidate for VFD use is a variable refrigerant flow systems. Variable refrigerant flow systems connect one or more compressors to a common refrigerant supply system that feeds multiple evaporators. By piping refrigerant instead of using air ducts, the distribution energy requirements are greatly reduced. Because the load on the compressor is constantly changing based on the demand from the evaporators, a VFD can be used to control the operating speed of the compressor to match the load, reducing energy requirements under part-load conditions.

Additional VFD Applications

While the primary benefit of both of these VFD applications is energy savings, VFDs are well suited for use in other applications where energy conservation is of secondary importance. For example, VFDs can provide precise speed or torque control in some commercial applications.

Some specialized applications use dual fans or pumps. VFDs, with their precise speed control, can ensure that the two units are operated at the desired speed and do not end up fighting each other or having one unit carry more than its design load level.

Advances in technology have increased the number of loads that can be driven by the units. Today, units are available with voltage and current ratings that can match the majority of three-phase induction motors found in buildings. With 500 horsepower units or higher available, facility executives have installed them on large capacity centrifugal chillers where very large energy savings can be achieved.

One of the most significant changes that has taken place recently is that with the widespread acceptance of the units and the recognition of the energy and maintenance benefits, manufacturers are including VFD controls as part of their system in a number of applications. For example, manufacturers of centrifugal chillers offer VFD controls as an option on a number of their units. Similarly, manufacturers of domestic water booster pump systems also offer the controls as part of their system, providing users with better control strategies while reducing energy and maintenance costs.

A Few Cautions

When evaluating the installation of a VFD, facility executives should take into consideration a number of factors related to the specifics of the application. For example, most VFDs emit a series of pulses that are rapidly switched. 

These pulses can be reflected back from the motor terminals into the cable that connects the VFD to the motor. 

In applications where there is a long run between the motor and the VFD, these reflected pulses can produce voltages that exceed the line voltage, causing stresses in the cable and motor windings that could lead to insulation failure. 

While this effect is not very significant in motors that operate at 230 volts or less, it is a concern for those that operate at 480 volts or higher. 

For those applications, minimize the distance between the VFD and the motor, use cabling specifically designed for use with VFDs, and consider installing a filter specifically designed to reduce the impact of the reflected pulses.

Another factor to consider is the impact the VFD may have on the motor's bearings. The pulses produced by the VFD can generate a voltage differential between the motor shaft and its casing. If this voltage is high enough, it can generate sparks in the bearings that erode their surfaces. 

 

This condition can also be avoided by using a cable designed specifically for use with VFDs.

Read More