Benefits and applications of medium voltage

August 28th, 2014 | Make a comment | Posted in Electrical distribution
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Benefits and applications of medium voltage according to Marvin M, one of the member of the community.

Introduction

Traditionally, any voltage over 600 V would evoke thoughts of high danger from the perceived high voltage. Engineers and technicians alike would abandon any systems operating over that limit and instead focus on the low voltage components, citing relative low risk levels.

Today, however, high skill levels, standards and installation requirements ensure that working with medium voltage is safe. It accords the following benefits.




Primary Metering

Primary metering is metering on the positive sides of the transformer. This saves a significant amount of kWh charges (about 5%). Rather than at the point of delivery, the meters are installed at the transformer, that is, the source.

In addition, the installation of the transformer has secondary benefits. Power distribution transformers with taps in the primary windings offer the primary benefit of allowing the user to regulate the secondary voltage as per the equipment ratings. This provides a closer fit with the equipment tolerances, as well as reduces chances of short circuits and arc flash incidents.

However, the engineers must first evaluate the potential energy rate savings against the cost of acquiring, installing and maintain the transformers for the primary metering application.


Fig 1: Primary metering with riser poles at a substation

Fig 1: Primary metering with riser poles at a substation




Minimize Voltage Drop

Ohm’s law (V=IR) clearly stipulates the basic relationship between the voltage drop and the current. The larger the load current and conductor impedance, the larger the voltage drop. In such cases, in case the source power is low voltage with long feeder lines, the feeders tend to be oversized to cover the losses due to conductor impedance.

MV feeder lines have lower load current, thus less voltage drop. This eliminates the need for oversize conductors, thus making the system more efficient.



Cost

The cost of copper has steadily risen in the recent years. Contractors, engineers and technicians seek to reduce the amount of copper in the feeder lines and line cables in the distribution system.

A workable solution is to invest in medium voltage distribution systems. The higher voltage results to lower current, which in turn means fewer conductors to distribute the power. The lower the number of conductors, the less the amount of copper used, thereby reducing on the conduit and installation costs.

Although MV drives are more practical in most of the industrial applications, various studies seek to determine better economic solutions. Do note that, due to the higher voltages, the current is lower. This reduces on the cost of copper cables required. The cost factor is more substantial especially in cases where long feeder lines are required, and the cable size, cost and the voltage drop become significant and substantial.



Applications of Medium Voltage

Any facility or plant that demands large amounts of power utilizes medium voltage. Other than the small, medium to large plants, other typical application areas are the data centers. A typical distribution system in data centers consists of a number of transformers and generators to prevent data loss due to power outage and redundancies.

However, such systems tend to be double or triple in size with the installation of these preventive measures. Rather than accrue the high cost, most data centers relocate the transformation as close as possible to the substations, maximizing on efficiency and reducing cost. Secondly, MV voltage usage in data centers ensures scalability, adaptability and modularity.

Data centers grow with technology: the power system should be set up, in a way that allows for easy and cheap expansion with minimal power interruption. With MV power trains consisting of the substation, UPS, Power Distribution Units (PDU), automatic transfer switches (ATS) and the backup generators; expansion is then easy as the only thing required is the connection of more power trains.


Fig 2: Data center power distribution system

Fig 2: Data center power distribution system


Other applications of MV include campus type facilities with centralized chilling or generating plants. Inclusion of an MV system eliminates the need for transformation equipment in such cases. In the same vein, large footprint warehouses, and high-rise structures are good candidates for MV distribution systems, due to the potential for long feeder lines.

For the high-rise buildings, the medium voltage, due to the reduced cable size and length, consequently reduces shaft size throughout the building, thereby increasing the usable footage area.



This was Marvin M's vision of medium voltage and the advantages of it. Now what is your opinion?

Low Voltage AC drives – their characteristics & their applications

August 25th, 2014 | Make a comment | Posted in Electrical distribution
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Hello, it’s Steven Mill! What do you know about LV AC drives? Let me tell a few words about it…

What are AC Drives?

There are adjustable speed drives that control the speed of DC and AC motors. The speed of an AC motor is determined mostly by two factors i.e. the frequency applied and the number of poles. So the formula goes as:

Low Voltage AC drives 1

Where:

  • N = RPM
  • F = frequency
  • P = no. of poles

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Step Up and Step Down Transformers

August 21st, 2014 | Make a comment | Posted in Electrical distribution
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One of our fellow member of the EEC sent us this article few days ago. Remember you can do the same and talk about whatever you want, even yourself!

What is a transformer?

Transformers are devices that change (transform) the voltage of power supplied to meet the individuals needs of power consumers. It uses the principle of electromagnetic induction to change the voltage (alternating difference) from one value to another whether smaller or greater.

A transformer is made of a soft iron coil with two other coils wound around it, but not connected with one another. The iron coils can either be arranged on top of another or be wound on separate limps of the iron core.

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Ground and test devices for engineers and technicians

August 18th, 2014 | Make a comment | Posted in Electrical distribution
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Marvin M. from the community had the great idea to give advices regarding grounding and test devices. Enjoy and don’t forget to post your own advices if you have few.

Introduction

A ground and test device primarily applies personal protective grounds to the MV components and conductors in the assemblies. It is a primary necessity as it creates a safe working condition for the engineers and technicians.

In essence, it offers prime protection for the personnel, equipment and facilities. According to the set standards, achieving a prime electrically safe environment encompasses the following:

  • Identify all energy sources in the working environment
  • Isolate the sources
  • Verify electrical source isolation
  • Lockout the devices to the sources
  • Test for voltage absence using the appropriate test device
  • Apply temporary personal protective grounds

The above steps must be fulfilled before the actual grounding. Do note that negligence of any of the steps leads to disruption of the production process and injury to personnel. Luckily, for engineers and technicians, various standards have been set up governing ground and test devices.

Ground and test devices for engineers and technicians

Fig.1 Ground and test device working principle

The standard divides the test devices into two categories:

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Miniaturization of electrical machines

August 14th, 2014 | Make a comment | Posted in Others
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Hi everybody, today I want to tell you about the miniaturization of electrical machines, a growing phenomenon. Hope you’ll like it.

Introduction

Being a 21st century homo sapiens, we may deny the significance of oxygen while suffocating but we can never deny the utility of science in life. The word has penetrated deep into our blood. No matter what we are suffering the resolution is “Science”.

Whatever is the issue, if you can’t make proper round chapatti ask science to do it for you through bread maker, or if you don’t want your hands to be abrasive while evacuating the oil spots from used dishes turn to science and get yourself relished with the dishwasher. Science can’t be restricted to mere kitchen but to every part of our daily life.

You are concerned about your growing tummy but still you feel lethargic enough to visit any park, get yourself acquainted with a scientific creature named “treadmill” or when one morning you’re given 7 minutes to reach your office against your suspension, seek help from Lamborghini Aventador whose 690 Nm (507 lbft) @ 5,500 RPM Displacement can only be your savior there.

Miniaturization of electrical machines 1
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