Video blog#1- neutral open and double phasing protection 


 

In this video we talk about a possible problem caused by two over head wires touching each other because of trees and causing damage and how contemporary solutions like stabilizers and SPD will not be able mitigate the problem.

If you have faced similar issues and want solution for it please give us your details in form below:

Or you could also visit our online store to range of products we offer.

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The need for 400V protection in every premise


Whenever a building is designed all safety factors are taken in consideration. From electrical installations point of view safety factors to be considered are

  1. Short circuit
  2. Lightning
  3. Over voltage.

All of the above considerations are from worst case Scenario basis. All of the above factors, if not taken care of, can lead to #fires and loss of property and assets. there are also chances are of human tragedy.

Shortcircuit is normally taken care in all premises. Lightning protection is generally employed for high rise buildings . Both of these factors are from worst case scenario.

however voltage protection becomes the most neglected part. the worst case scenario in voltage is 440V in single phase and it can be caused by 2 reasons primarily

  1. Neutral open
  2. Double phasing caused by touching of overhead wires.

There is actually no safeguard designed to take care of this situation. We depend on our equipments to handle the overvoltage scenario. many equipment can handle this problem for short period of time only. Most electrical contractors consultants and architects do not offer a robust solution for such issues.

#MSS offers solution focusing on this very aspect of electrical problems. For details get in touch with us on queries@microsystemservices.com

 

The need for double phasing and neutral open protection in Solar power plant design


Solar inv.jpg

Generally any equipment will get damaged due to 3 primary reasons.

  1. Short-circuit
  2. Lightning or surges
  3. Temporary over voltages.

First 2 reasons are taken care of in design and considered as per worst case scenario.

However safeguards for temporary over voltage are generally not taken, certainly not considered as per worst case scenario.

In secondary side of LT transformer , worst case scenario is 440V in single phase.

It happens more often than expected.

Reasons for 440V coming in your supply

  1. Neutral open condition
  2. Double phasing

Causes of neutral open.

  1. Uneven load distribution
  2. Loose wiring.
  3. Accidental breakage
  4. Maintenance work errors

neutral open

Causes of double phasing

  1. Trees falling on overhead wires
  2. Touching of overhead wires running through trees.

double phasing

Majority of projects are located outside of city limits due to roof space constraints and industry requirements. Such scenarios are very common

Not one of the available solar inverter can handle a continuous over voltage of the above nature and will get damaged resulting in down time.

There is strong need of safeguard against such issue in design stage itself so that such issues can be tackled with min losses.

To illustrate, if there is short circuit or lighting strike, the system is designed to handle it. However for continuous over voltage there is not a single solution that can be offered.

There is infact no solution incorporated for 440V in single phase. Most of integrators rely on the inverters capacity of handling voltage fluctuation, and they will definitely get damaged in such a situation.

This is where it is recommended to take cognizance of potential problem that can be taken care in design stage itself.

We specialise in this area i.e. Neutral open and double phasing protection.

You can see our website www.microsystemservices.com for details on how we can add value to solar field.

Did your LED light get damaged?


LED lights damage

Are inverter based equipment sturdy enough for Indian conditions?


Our appliances are getting smarter by the day. Its a good thing that many companies are  energy conscious and are making their appliance even more energy efficient. In India most of home appliance are now made compulsory to have 5 star energy ratings, especially cooling appliances like ACs , refrigerators.

The TV ads are now flooded with ads talking about inverter based ACs, refrigerators. This is great news for energy conservation. However there is rider to all this. These units are susceptible to damages because of power fluctuations.

A traditional circuit consisted of a step down transformer which converted 230V AC to 24V AC which was then fed to bridge rectifier. The rectifier then converted the AC to DC and then it was distributed to the internal circuits with regulator and other component. Even if the voltage increased dramatically the secondary side would experience a relatively low surge on voltage. Prolonged exposure to voltages might have caused damages to internal circuits. In short these circuits were relatively very sturdy in voltage fluctuations.

However transformer has losses. It dissipates a lot of energy in the form of heat. Even in best cases the efficiency possibly didn’t not go beyond 87%, which was problem. Transfomer is bulky.  Higher powered (kVA) machines would require a bigger transformer and as result were heavy too.

What we call inverter technology today , consist of PWM inverters and SMPS based circuits, may be even more advanced.  These units have done away with conventional transformer based circuit and in effect increased the efficiency. They are also light weight , very compact and dissipate less energy as heat. They also come in attractive housings

However the flip side is that these circuits are now directly exposed to raw power. This is where the new problems have come up. These circuits are having 20% tolerance to voltage fluctuations. This would mean 180V on lower side and 280V on higher side. Seems ok doesn’t it? Wrong!!!

In developing and underdeveloped countries the power conditions are not so good and voltage frequently goes beyond 350V. This is a curse for these inverter based appliances, which get damaged more frequently than their predecessors.

These circuits are not inherently designed for such conditions and since units are manufactured considering global markets which include EU and US. Many white goods brands have made their foray in a new market only to have marred their reputation by service issues. We have many brands making their disappearing act after blitzkrieg of sales and ads.

One can attribute a serious contribution of such factors on making and breaking of brand in Indian conditions. There is probably two options here, either improve the tolerance of the internal circuits or protect the units externally by use of some protection equipment.

Do let us know what you think.

Author: Amit Manjrekar

(Click the image to learn more about him.)

amit

Lightning and surge protection


Surge protection

Surge Protection – a topic that has become increasingly important in recent years as got wide presence across industries. Costly electronic equipment, which is sensitive to voltage peaks on the supply, is no longer found only in offices and factories, but in our homes as well.

Nowadays, highly- sensitive data processing, telecommunication and computer networks form the back-bone of worldwide communications structures without which, no company can survive. Machines and production lines are monitored and controlled by electronic equipments programmed for specific purpose. Even many creative services are no longer conceivable without the aid of computers.
Common to all of them is their dependence on clean electrical energy, within tight tolerance limits and on a continuous supply of power around the clock.

Internal Lightning Protection according to IEC
Lightning current consists of a First stroke followed by a number of subsequent strokes. According to IEC 61024 and IEC 61312, wave shape of the first stroke is calculated to be 10/350 μSeconds.

lightning pulse

Approximately 25 to 30 % of failures in electrical/electronic equipments are because of surges created either by a Lightning or because of switching surges as per the data released by leading insurance companies

power survey

Lightning Peak Current and Frequency of strike:

The maximum value of Lightning current can go up to 200 KA as per IEC 61312 which is in the shape of 10/350 μ Seconds.

Lightning Current Distribution:

According to the standards IEC61024 and IEC 61312, during a lightning strike in a building having an external lightning protection, the lightning current reaches the earth termination. A part of Lightning current goes to earth and remaining part gets coupled into the building through conductive media like Steel reinforcement in Concrete, Earth Conductor Metal Parts connected to earth etc.

lightning distribution

The 100% of lightning energy breaks down as follows according to IEC61312:
–  50% of the lightning current will flow through the ground
–  50% of the lightning current will flow over the connected metal parts of the building (gets coupled into the building)
To protect electrical & electronic equipments inside the building, this 50 % of Lightning current which is entering into the building has to be diverted to the metal parts which is connected from outside. (Metal Water pipe, Metal Sewage pipe, Power lines, data lines etc)

Class B: (Class 1 according to IEC 61643 as well as Class C according to VDE0675)

is an arrester which is designed to carry a lightning current of 10/350 μ Sec duration. Important parameters to be taken care are Lightning Impulse current carrying capacity and Voltage Protection Level (Let through or limiting or clamp voltage)
Class C: (Class II according to IEC 61643 as well as Class C according to VDE0675)

is an arrester which is designed to carry a Surge current in the shape of 8/20 μ Sec. Important parameters to be taken care are Maximum or Nominal Discharge Current carrying capacity and Voltage Protection Level
Class D: (Class III according to IEC 61643 as well as Class D according to VDE0675)

is an arrester which is designed to carry a Surge current in the shape of 8/20 μ Sec as well as tested with a voltage impulse in the shape of 1.2/50 μ Sec. Important parameters to be taken care is Voltage Protection Level

connection diagram SPD

SPD’s are made with Spark Gaps, Metal Oxide Varistors(MOV) Silicon Avalanche Diodes(SAD), Gas Discharge Tubes(GDT) or a combination of these devices
Spark Gaps and GDT’s:

These are called as ‘voltage switching type’ SPD’s. The operating voltage can be determined by the distance between the electrodes. Spark gaps are arresters in which two or more electrodes in series are opposed to each other. The electrodes consist of incombustible material (e.g. carbon or tungsten-copper). Spark gap based arresters used in power line between Line and Neutral should be capable of interrupting the Short Circuit Current (also called as follow current)

GDT

Advantages – It can carry Very Large amount of Surge Current for a long Duration
Disadvantage – Need more time to react (about 100 nano sec), high follow Currents
MOV:

(Metal Oxide Varistors) Varistors are ‘Voltage-dependent resistors’ with a highly non-linear V/I characteristic. Their electrical properties arise from a large number of micro-varistors connected in parallel and in series. The transitions between the micro-varistors can age under the influence of over voltages. Varistors are called as voltage clamping type SPD’s

MOV

Advantages – Faster than Spark Gap (approximately 25 nano sec). Limited current carrying Capacity
Disadvantage – Detoriation after every surge. Can create short circuit after a Maximum discharge current flow

Avalanche Diode:

Transzorb diodes (also known as suppressor diodes) are diodes that limit both positive and negative over voltages. Because of their very fast switching performance (in the picosecond’s region) they are well suited for use in precision and data line protection devices. These are also called as voltage clamping type surge arresters

Avalanche diode

Advantages – Very fast response to surges

Disadvantage – Very low surge current carrying capacity

By using Surge arresters at various zone boundaries, Transient over Voltages created due to a Lightning strike or switching surges can be limited below the Voltage Impulse with standing capacities of the equipments in respective zones.

SPD example

Write to us for more queries on queries@microsystemservices.

Also see

1. Does an AVR or surge (spike) suppressor really protect from voltage fluctuations???

2. How  does Servo Stabilizer work?

3. OVCD

About the Author (Click on the image to visit his LinkedIn profile

amit

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