33KV Medium Voltage Isolator Sparking

This videos captures a slight sparking of 33KV medium voltage isolator in a substation when closed. Isolators should always be opened or closed in no-load condition since they lack any kind of arc-quencing mechanism unlike Circuit Breakers. On load, they may embark a dangerous fire due to air breakdown.

CAUTION: Electricity is DANGEROUS. 

Figuring out my Role as NEA Electrical Distribution Engineer

I can say this with confidence if you are electrical engineer in Nepal then you must have at least once thought about getting into Nepal Electricity Authority (NEA), the main electricity regulatory authority of the Nation. After completing my B.E (Electrical) from Institute of Engineering, Tribhuvan University (2008-2012), I had many options in my disposition and getting into NEA by taking part in tough Open Competition was one of it. Not that NEA have frequent vacancy calls, but we (our batch of engineers) have considered ourselves lucky because there was huge seats of vacancy calls and total of 129 electrical engineers were recruited after (quite a long procedure of) open competition in written and interview. I am one of them.

I have been appointed as Electrical Engineer, Officer Level 7 at Baglung Distribution and Customer Services (DCS), NEA. That means I am now beginning my career as Electrical Distribution Engineer and for me this is a huge huge opportunity to apply what I have learnt in field of electrical engineering during past 6 years. Just like me, most of our batch of newly recruited Electrical Engineers have been posted to various DCS across the country. From this we can learn that, there have been huge shortage of electrical engineers in one of the most crucial body of NEA i.e Distribution and Public Relation. So, for newly appointed engineers it is a bigger challenge to uplift the galcous image of NEA among the general public along with their core technical service area. (In the future I will probably someday write about the public response to services of NEA as well).

After appointment (Jan 16, 2015) , NEA conducted 15 Days of “Induction Training” for new recruits starting from Jan 18, 2015 which was concluded yesterday ( February 2, 2015). The main objective of this training was to bridge the gap between academy courses and professional requirements since in the new batch of Engineers some were fresh graduates along with few experienced engineers.

I would like to bullet out some major highlights of this training:

• Establishment and History of NEA
• Orientation about various Sectors, Directorates, Departments and Branches of NEA from respective heads.
• Overview of various service areas, rules, regulations, laws, by-laws, formats and procedures inside NEA
• Overview of national and international laws and regulations guiding the responsibilities, rights and duties of professionals and citizens.
• Overview of past and ongoing projects along with their development and challenges.
• Technical practices and regulations followed in NEA
• Trainings on development of professional etiquette and social human behaviour

( I will be writing different topic about major learnings and how I am applying them in the real field as well as challenges associated with those)

Thus, in  an overall sense, I consider this as a very fruitful fifteen days. And yes, this is the first time NEA has conducted a fifteen days Induction Training by replacing the three days Induction Training.

During the course of training, I paid special attention classes regarding various distribution policies, status, challenges and duties of distribution engineer. In the meantime, I have also started building a basic duty map and guidelines for my new career. This started with making the list of basic roles of electrical distribution engineer. I am quite aware that it won’t just be core technical jobs that I would beed to handle. While working in DCS, we will need to pay extra attention to need of community and consumers and provide them services keeping in mind the high sense of responsibility as an public officer and high quality technical design and implementation as an Electrical Engineer among various legal and socio-economic constraints. After completion of Induction training since yesterday, now we shall be working in our respective offices. Although we already have scattered images of our duties in upcoming days, I wanted to organise the stream of thoughts and hence I am writing this.

Basic Roles of Electrical Distribution Engineer

I have divided the roles under various topics as following:

Social/Professional Roles:

• Coordinate with the upper authorities, same level authorities and assistants (S)
• Coordinate with different departments and offices for smooth operation of plans (S)
• Study related laws and regulations (S)

Essential and Major Roles:

• Prepare Plans, Specifications and Cost Estimates for the installation, maintenance, repair and expansion of electrical distribution system (E and M)
• Develop specifications for material purchases and construction standards (E and M)
• Calculate customer loads for sizing transformer banks and services (E and M)
• Inspect the Installation of electrical equipment and related facilities (E and M)
  Budget coordination, disbursement and Control
  
• Respond to emergency conditions and assist in restoring the electrical distribution system to normal operation (E and M)
• Advice developers and contractors regarding technical requirements (E and M)
• Coordinate electrical distribution system, street and traffic lighting, industrial distribution. (E and M)
• Perform system protection and coordination systems (E and M)
• Coordinate with work of crews engaged in O/M of structures, distribution lines and substation. (E and M)

Essential Roles:

• Perform System Planning and Development Studies (E)
• Recommend Construction practices and procedures (E)
• Respond to consumers/citizens complaints and questions (E)
• Provide highly responsible and technical staff assistance (E)

Related

• Inspection and Monitoring of Electrical System Performance (R)
• Take active participation in developing the Goals, Objectives, Policies and Planning (R)
• Prepare case studies, reports and recommendations pertaining to the overall electric system operation ( R )

I hope this can serve as guidelines to me and other colleagues as well.

I decided to do this because during the course of training I heard this complaint that a proper Job description has not been yet provided. This is not the official job description but just the realizations of basic roles of Electrical Distribution Engineer. (smile)

Solar Array and Battery Bank Service and Maintenance in Solar PV System

o  SOLAR ARRAY AND MOUNTING

Solar arrays are usually maintenance free. However, a routine service can help to maintain a good energy production efficiency.

Routine Servicing for Solar Array AND MOUNTING:

o    Clean the dirt and dust accumulated in solar modules with water and soft mob/cloth during long dry season

o    Visual inspection of the modules for any kind of cracks, discoloration, damage should be done periodically. Note in case of any such case and contact the service provider for further inspection.

o    Check the solar mounting for any kind of deformation. Note the position of deformation and contact the service provider.

o    Check the nut-bolts on the mounting frame for loosening. Tight them if required. Ensure the mounting and frames are firmly secured.

o  BATTERY BANK

Battery bank may consist of individual 2V cell connected in series/parallel or 12V block battery in series/parallel as per the system requirement and design. Battery bank is the energy storage unit of the  Solar PV system. Even an individual battery has high energy density; improper leakage of this energy may result in heavy damage and cause huge loss to life and property. Please follow the safety precautions around battery bank while routine servicing and maintenance.

Routine Servicing for BATTERY BANK:

o    Cleanliness should be done regularly around the battery bank to ensure good connection at the terminals as well as preventing the contamination of the electrolyte while removing the caps. The frequency of the cleaning should be according to the environment. In places with high dust density, battery bank should be cleaned monthly. (Follow proper steps to clean the battery bank.

Steps to clean the battery bank

§  Isolate the individual cell/block. To do this first turnoff the charging system. Take proper care while handling battery not to do short circuit and spill acids.

§  Disconnect the terminals from the posts/bolts.

§  Clean the outer body with gently wet soft cloths. Be careful not to let water to enter inside cell.

§  Clean the terminals of battery until they are clean and shiny. If there is corrosion due to rusting, clean the terminals with baking soda.

§  Rebolt the connection in right terminals.

§  Apply petroleum jelly to the terminals and cover it with insulating caps.

§  If unable to unbolt the terminals, place a wet cloth over it for 2-3 hours and open it.

o    Checking the Electrolyte level to ensure that individual cells have enough electrolyte for condition. This is very important to prevent stratification of the battery bank.

NOTE: Only wet flooded lead acid battery can be refilled with distilled water.

Steps to check the electrolyte level

§  Visually inspect the level indicator provided in the battery.

§  In case required, refill the individual cell with distilled water.  

Do not refill it with tap water or rainwater collected in metal container.

NEVER REFILL ACID IN THE BATTERY

Follow the given STEPS TO REFILL DISTILLED WATER in the battery:

C  Shut down the load and charging on the system.

C  Open the cell cap which requires refilling.

C  Slowly add distilled water upto the top level as shown in indicator.

C  Do not top up the cell upto the brim. Leave at least 2cm gap between brim and electrolyte level for gassing.

C  Put back the cap.

C  Refill other cells turn by turn

C  Charge the battery bank for at least one day before reconnecting to the load.

o    Equalization charging should be done monthly to prevent hard sulphation inside the cell. This is usually programmed in the charge controller itself.

o    Check the Battery State of Charge by measuring voltage. Voltage at the terminals during various condition like instantly after charging, instantly after low voltage shutdown, etc should be measured and recorded in big systems to study the condition of the battery. Keep a battery voltage log sheet for recording.  DO NOT USE LOWLY DISCHARGED BATTERY without fully recharging. Such practices may hamper the battery life.

SAFETY FIRST (Hazards and Precautions around Solar PV System)

Solar PV system like other other electrical systems is safe when operating correctly. However, they may cause trouble when the system is suffering from malfunction. Such hazard may cause simple electric shock to deadly electrocution. Also there are some potentially dangerous hazards associated with some components.

·         SAFETY AROUND SOLAR PANELS

The owner of the system must not undertake any maintenance of the solar modules except simple cleaning.

Hazards related to solar panels

§  Many numbers of solar panels of lower voltage may be connected in series as per the system design and requirement to get higher voltage. While the lower DC voltage up to 48V does not possess potentially high danger of electric shock, the system above 48Vdc may give electric shock in wet unprotected condition.

§  Falling off roof while working

SAFETY PRECAUTIONS

§  Always wear insulated boots before working with connection of solar panels.

If the system is above 120V dc then, compulsorily wear insulated boots before working with the connection of solar panels.

The outer body of solar panels is well insulated and grounded in case of any leakage.

§  Do not leave any part of the wire connection outside junction/connection box without insulation.

§  Support yourself correctly while working with solar panels in case of narrow/difficult place.

·         Safety Around Battery Bank

The owner of the system must not undertake any maintenance to battery bank of 120V Dc or above.

Hazards related to Lead acid battery bank

§  explosion due to Hydrogen gas

§  Burning caused by dil. sulphuric acid in cells of battery

§  Shorting of positive and negative terminals leading to fire hazards

§  Electrocution caused by battery bank of 120V or above

SAFETY PRECAUTIONS

§  Do not wear any metallic objects like bracelets, chains, watches, etc while working near the battery. It may accidently short circuit the battery terminal and cause unrecoverable damages.

§  Be careful while using metallic objects and tools not to cause short circuit between the terminals of battery. Battery has very high energy density and may cause huge loss with fire hazards and explosion

§  Do not work in vicinity of battery bank if there is strong smell of Sulphuric Acid

§  Do not smoke near the battery bank

§  Do not cause any flame near the battery bank. Hydrogen is highly combustible gas.

§  Protect your clothes from spilling acids like acid resistant aprons while working near battery bank

§  Wear safety goggles to protect your eyes. In case your eyes get contaminated with acid, rinse it with clean water and seek the medical attention immediately.

§  Use baking (bicarbonate) soda to neutralize the spilled acid or cure the acid burn.

§  Seek the immediate medical attention along with first aid in case of electrocution.

§  Keep the room well ventilated

Safety Around balance of system (Bos) components

Balance of System(BOS) components includes the power conditioning and control unit of the system. The main BOS components in Solar PV System are Solar Charge Controller and DC to AC Inverter.

Hazards related to bos components

§  Electrocution due to leakage current

§  Electrocution due to insulation failure

SAFETY PRECAUTIONS

§  Follow the recommendations provided in manual of BOS components

§  Always keep the area clean and dry

Typical AC Mains Solar Hybrid System in Nepal

One of the most common household applications of Solar power system here in Nepal has been AC Mains-Solar Hybrid System. These systems are generally the choice of customers suffering from load shedding in areas with electricity supply through national grid. Although there is some connection with grid in such kind of system, this is totally off-grid system. The Grid current is only used for charging the battery bank along with solar charging unlike supplying the load.

We are trying to design a charging unit with two inputs with intelligent charging control that can be used in AC Mains Solar hybrid system installed as backup to continue the electrical interruption due to regular and routine power outage (loadshedding) in Nepal with utility grid supply.

The topology of currently found solar hybrid system is as shown:

Fig 1

As we can see that there is no control over amount of grid charging or solar charging in the current system. Hybrid Solar system are designed to charge the battery bank with only half energy supply from solar but the current system doesn’t guarantee this idea of 50% charging from solar as there is no control mechanism from grid charging. If both sun and grid charging are available then the battery will be automatically charged from both the inputs with their full potential without any regards to what and how the system is supposed to work.

The topology of most used commercial solar hybrid system is given below (Fig 2):

Fig 2

We can also find some power conditioning equipment with solar charge controller incorporated inside the same casing along with AC-DC Charger and Inverter. They are generally marketed as Solar Hybrid Inverter. Its general topology is as shown in Fig 3.

Fig 3

Solar Minigrid Topology

Cluster micro hydro power plants has been a success story in Nepal, and various researches for stable and reliable mini grid for micro hydro is going on. But not all places of Nepal has favorable environments for micro hydro and are too far from national grid. In that case, solar mini grid can be economical and viable option in rural village far from national grid and where other alternatives like micro hydro, diesel generator are not possible or economical. Community based solar mini grid can be a a good idea to power household loads and few micro small mini enterprises. In today's society where communication devices like mobile phones has been inseparable part , rural telecommunication towers can also be benefited by such mini grids.

A simple topology for such system is presented here.

A manual on Solar PV Home System Design

Suryodaya Urja, A leading PV Company and also a place where I currently work, was called upon to mentor "A workshop on Solar PV System Design" organised by Locus 2013 on June 2013. Hence, I got this opportunity as an Engineer of the Company to be part of the event as Trainer/mentor along with Er. Santosh Shrestha, also an engineer currently working in Suryodaya Urja. For the workshop I had prepared a short manual as a handout to all the participants. The same manual is being shared here.

Download

This manual is for the beginners and useful for Standalone Home System for a Home.