If you can't explain it simply, then you don't know it well enough. — Albert Einstein

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Information on Solar Photovoltaic Street Lighting System & Working Principle

Solar Photovoltaic street lighting system works on photovoltaic cells or batteries, that convert sunlight or solar energy into electricity. If you come across a solar lighting system, note the dark panel on top of the light. That is the panel of the photovoltaic cells, which will convert sunlight into electricity. This electricity will then be stored in the batteries. This power can be used as and when needed. The batteries being connected to solar cells, charge themselves continuously while the solar panel is being exposed to available Sunlight. These batteries are inbuilt into these lighting systems. Hence the lamps are capable of drawing light from them. This consequently negates the solar lighting systems from any kind of need to be attached to wires, for power transmission. Hence solar street lighting systems are always wireless.

[Also Read: Solar Power System]

Being a lighting system, meant for the outdoors, solar lighting comes in many shapes and styles, which are aesthetically appealing.

solar photovoltaic street lighting system

How does a Solar lighting system work?

The working principle of these lights is fundamentally simple. During daytime, the PV cells absorb light. As the Sun goes down, an automated switch, which is a photoreceptor too, sensitive to the intensity of available light, deciphers the low Sunlight. This triggers the system to switch on the solar street lights. At this point in time, many would wonder about how will this receptor work, when the sky becomes overcast with clouds? This is a tad tricky to answer.
If the days have been cloudy, most of the time, it is unlikely that the solar cells have charged themselves abundantly. This will mean weak electricity production from these batteries, which in turn, will imply that the lights will not sustain through the night. However, if the sky becomes overcast suddenly, the photoreceptors will kick in to switch on the lights.
Here is a list of information on solar street lighting systems, for a better understanding.
  • Reach into difficult terrain: Since these lighting systems are without any hassle of wires, the installation of solar lighting systems is easy. Perhaps this is one of the reasons why these lighting systems make for an ideal system in difficult terrains. Hence it is these lighting systems are the ones reaching the most remote areas of rural India today.
  • Ideal for parks and dark places: Solar lighting systems are efficient and powerful. They are cost efficient also which makes these systems a great choice for lighting parks, playgrounds and other darker areas for security.
  • Resistant to blowouts and power outages: Solar lighting system is not dependent on any kind of external source for electricity production, like thermal electricity production. It is therefore unlikely that a storm or bad weather can get these lights to stop working due to a power outage. This is probably one of the reasons why is Solar lighting systems are preferred in areas which experience storms and power outrage often.
  • Low Maintenance: Solar lighting systems are low on maintenance cost. Most of the systems come to with a warranty of 25 years. With hardly any disturbance or human manipulation needed to get the solar lighting system going, these systems are perfectly capable of running flawlessly for years.
  • Once in a year or six months check up: Solar lighting systems need an unobstructed reception of sunlight. However, these light systems, are exposed to outside world 24*7. Hence collection of dust and grim on the surface of the PV cells surface is not surprising. This said, the outdoor lighting systems should be regularly checked to ensure that the panels are free of any accumulation of dust that may form a film of obstruction on the PV panel. Attention must also be paid to the batteries that need to be changed once in a while.
  • Enhances landscape and aesthetic lighting: Whenever it is about the lighting systems, meant for the outdoors, the stress in the aesthetic appeal is always more. This is because the normal solar lamps have a bluish hue to it, which makes it a perfect aesthetic enhancement. This creates an amazing essence of night lights.
[Also Read: The future of solar energy in India]
Conclusion:
The solar photovoltaic lighting systems are the stepping stones towards making outdoor solar lighting a reality. The pros of these systems are many, yet much is left to be explored.
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Electrical Safety Inspection: Importance and Checklist

No one hesitates to call an electrician whenever a fault is seen. However, most people will take their electrical wiring safety for granted.

Importance of home electrical safety inspection

All electrical installations/wiring will deteriorate with age and use. However, most home owners often overlook the wiring condition. At the most, an electrical safety inspection will only be called when a breaker has already been tripped or a fuse has already been blown. It is not surprising that an electrical fault is a common cause for house fires.
Having your electrical wiring inspected is one of the most important things to keep your home safe from electrical hazards. You don't want to risk the lives of your loved ones, nor getting your property damaged due to electrical fires. Therefore, electrical safety should be a top priority in your home.

home electrical safety inspection

A proper electrical safety inspection will:
  • Identify electrical wiring and components that may have degraded over time.
  • Reveal if any electrical circuits are overloaded.
  • Reveal if any lack of earthing.
  • Identify any defective wiring or other mistakes made by non-certified electricians or DIY home-owners.
  • Spot oversized fuses or breakers that may cause an electrical fire hazard.
  • Find any potential electric shock risks.

When to do home electrical safety inspection?

  • When purchasing a home. It is better to ensure that your new home is electrically safe before moving in.
  • If your home is more than 25 years old and has not had an electrical inspection.
  • If you have had a major renovation to your home.
  • If you observe an electrical appliance that is operating erratically, especially if it is much older.
Periodic safety checks are also important and should be carried out every 10 years or while adding a new appliance.

[Also Read: Electrical Safety for manufacturers]

Home electrical safety inspection checklist

  • All light fixtures, sockets, switches are in good condition and working.
  • All wires are in good condition without any signs of deterioration, wear and tear.
  • All circuit breakers, RCDs etc. are operating properly and fuse elements are appropriately installed.
  • Suitability of all switchgear (MCBs, RCDs etc).
  • Proper grouping and labeling inside the distribution panel.
  • Earthing/grounding system is proper.
  • Wiring method is up to date to ensure that it is suitable for current use.
  • All wires of a circuit are grouped together.
  • Proper insulation of electrical system near wet and damp locations.
  • Wires or sockets are not being overloaded.
  • Reducing the necessity of extension cords by adding permanent fittings if required.
This is a general checklist while inspecting a home electrical system. However, a certified professional electrician will inspect thoroughly to ensure the safety. It is important to call only a licensed electrician for safety inspection or for any major electrical work. You may be able to easily find a licensed electrician in your local area by searching on the internet. For example, these electricians in Perth provide electrical safety inspection and recommend you what can be done based on their inspection.
Electrical safety inspection is must for every household to ensure safety from electrical hazards. Worrying about electrical inspection costs? Well, you may actually save more by preventing repair costs by calling an electrician after a fault has occurred. And it's not just about costs, it could be about lives.
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What to do when your RCD or Circuit breaker trips

When it comes to electrical safety, it is extremely important to have various safety devices installed, such as RCD and Circuit Breakers. These devices, when properly installed, protect from electrocution and fire hazards caused by electrical faults. An RCD or Residual Current Device is also called as Safety switch.

switchboard, RCD, Safety switch, circuit breaker

Is an RCD same as a Circuit Breaker?

RCD or Safety Switches are often confused with circuit breakers. While both of these devices protect us from electrical hazards, they are not the same thing.
A safety switch constantly monitors the current flowing through the live and neutral wires. Under normal conditions, the current through live and neutral wires is equal, that means the circuit is balanced. However, if returning current through the neutral wire is not equal to the current going through the live wire, it means a part of the current is going somewhere else. This could just be a current leakage or maybe someone is being electrocuted. Whenever an RCD (Safety switch) detects such an imbalance in live and neutral current, it breaks the circuit almost instantly (within 0.03 of a second).
A circuit breaker basically protects circuits from short-circuit and overcurrent conditions. It detects when the current flowing through is greater than the rated value and cuts off of the circuit. A circuit breaker is not designed to protect an individual from electrocution. So it is important to have safety switches installed in addition with circuit breakers.

What causes an RCD or Circuit Breaker to trip?

When something is seriously wrong with electrical wiring or circuit, the RCD and/or circuit breaker trips disconnecting the circuit from power supply. There are various reasons that can trip a safety switch or circuit breaker.
  • Circuit overload: Overloading of a circuit is the most common reason for tripping your circuit breaker. When a circuit is overloaded it consumes more current. When this increased current reaches beyond the rated limit, the circuit breaker "trips". A safety switch may not trip in case of overload as the circuit still might be balanced.
  • Short circuit: This occurs when the live wire touches neutral wire directly. In this case, a large amount of current flows producing a large amount of heat and may cause a fire hazard. A circuit breaker trips almost instantly in case of short circuits.
  • Ground fault: Similar to short circuit, a ground fault occurs when a hot wire or live wire touches the ground. In this case also, current increases rapidly causing the circuit breaker to trip.
  • Faulty appliance Damaged or faulty appliances can leak excess current. When this leakage current is detected by an RCD or safety switch, it trips and disconnects the circuit.
  • Damaged wiring: Damaged wiring may cause current leakage, ground fault or even short-circuits.
  • Moisture: Current leakage can also occur due to moisture present in electrical switchboards, sockets etc. Wet appliances also produce electrical faults when switched on.
Along with these, there are various other reasons that can produce electrical faults and trip your RCD or circuit breaker.

What to do when your RCD or Circuit Breaker trips?

Resetting a tripped RCD or Circuit Breaker is pretty easy. You just need to flip back the toggle switch to "ON" position. However, it is not a good idea to directly reset the tripped RCD or Circuit breaker without knowing what may have caused it to trip. Following are the steps to figure out the cause of tripping of an RCD or Circuit breaker.
  1. Turn off all the lights and unplug as many appliances as you can. The circuit breaker may have tripped due to overloading of the circuit. So if you directly reset it without disconnecting appliances, there is a good chance of causing the same problem again. Also, if you have recently added and switched on an appliance, make sure to disconnect it before resetting the breaker.
  2. CAUTION! Working with electricity can be dangerous. Never try to touch an electrical panel or any electrical equipment with wet hands. Also, make sure to stand on dry surface with rubber shoes at all times while working with an electrical panel.
  3. Go to your electrical panel and find out which RCD or Circuit Breaker has tripped. This may be easy as you just need to find out which toggle switch has flipped from ON position to OFF position. Once you figure our the tripped device, follow the below steps.
    • First, move the toggle switch to full OFF position (Tripped position is half-way between ON an OFF position).
    • Then move the toggle switch to full ON position. This will restore the power to the circuit.
  4. If the device does not trip again immediately and the power is restored, you can skip to the next step. But if the device trips immediately again, it may be a sign of a fault in wiring or a serious electrical problem. In this case, you need to call a certified electrician to get it checked properly.
  5. After restoring the power, plug in the required appliances one by one and check if the RCD or Circuit breaker trips again. If you plug in a faulty appliance, the device will trip again. Make sure not to overload with too many appliances.


This article is sponsored by:
Westline Electrical Services is a proudly WA owned and operated family business. Their professional Electricians serve residential, commercial, and industrial customers.

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Methods of voltage control in power system

Before learning the methods of voltage control in power system, we must first understand why do we need to control voltage. In power systems, voltage is supposed to be constant which is obviously not. So we have to control it in such a way that it remains constant. But why does the voltage need to be constant at all? Because, most of the devices, apparatus, electrical machines, consumer appliances etc. are all designed to work at a specified voltage. Wide variations of voltage may cause errors in operation, malfunctioning or performance deterioration. It is desirable that the consumers receive power at substantially constant voltage. In many countries, including India, the statutory limit of voltage variation is ±6% of the declared voltage at consumers' end.
Therefore, it is important to apply certain techniques, certain methods to control the power system voltage to keep it constant. Following are the methods of voltage control in power system.

voltage control in power system

Methods of voltage control in power system

  1. Using excitation control or voltage regulators at generating stations
  2. By using tap changing transformers
  3. Using induction regulators
  4. By using shunt reactors
  5. By using shunt capacitors
  6. Using synchronous condensers

Excitation control or voltage regulators at generating stations

Induced emf (E) of a synchronous generator (alternator) depends on the excitation current (field current). The terminal voltage of an alternator can be given as V = E - IZ. As the load current, and hence the armature current, increases, voltage drop in the armature also increases. The field current must be increased to compensate this voltage drop, such that the terminal voltage is at the target value. For this purpose, alternators are provided with excitation control or automatic voltage regulator systems. There are two main types of automatic voltage regulators (AVR):
  1. Tirril regulator
  2. Brown-Boveri regulator
An automatic voltage regulator detects the terminal voltage and compares it with the reference voltage. The difference between detected voltage and given reference voltage is called as the error voltage. The regulator then controls the excitation voltage of the alternator to cancel out the error voltage. Thus, an automatic voltage regulator controls the voltage by controlling the excitation.
Excitation control method is satisfactory only for short lines. For longer lines, the terminal voltage of alternator has to be varied widely for the voltage at far ends to remain constant. Obviously, this method is not feasible for longer lines.

By using tap changing transformers

The voltage control in transmission and distribution systems is usually obtained by using tap changing transformers. In this method, the voltage in the line is adjusted by changing the secondary EMF of the transformer by varying the number of secondary turns. Secondary voltage of a transformer is directly proportional to the number of secondary turns. Thus, the secondary voltage can be adjusted by changing the turns ratio of the transformer. Secondary number of turns can be varied with the help of tappings provided on the winding. Basically, there are two types of tap changing transformers.
  1. off-load tap changing transformers
  2. on-load tap changing transformers

Voltage control using off-load tap changing transformers

In this method, the transformer is disconnected from the supply before changing the tap. Off load tap changing transformers are relatively cheaper. But the main drawback with them is that the power supply is interrupted while changing the tap.

Voltage control using on-load tap changing transformers

In modern power system, continuity of the supply is important. Therefore, on-load tap changing transformers are preferred to control the voltage.

By using induction voltage regulators

An induction regulator is basically an electrical machine somewhat similar to an induction motor, except that the rotor is not allowed to rotate continuously. The rotor of induction regulator holds primary (excitation) winding which is connected across (parallel) the supply voltage. The stationary secondary winding is connected in series with the line which is to be regulated. From electrical point of view, it is immaterial whether primary winding is rotating or secondary winding is rotating. The magnitude of voltage in the secondary winding depends upon its position with respect to the primary winding. Thus, the secondary voltage can be adjusted by rotating the primary winding. Induction voltage regulators were used to control voltage of electrical network in earlier days, but they are now replaced by tap changing transformers.

Voltage control by using shunt reactors

Shunt reactors are basically inductive elements that are provided at sending end and receiving end of long EHV and UHV transmission lines. When a transmission line is not loaded or lightly loaded, the line capacitance predominates and receiving end voltage becomes greater than the sending end voltage. This effect is known as Ferranti effect. In such situation, shunt reactors are switched in the line. Shunt reactors compensate the line capacitance and, hence, control the voltage.

Voltage control by using shunt capacitors

Shunt capacitors are usually installed at the receiving end substations or near industrial loads. Most of the industrial loads draw inductive current and therefore the power factor is lagging (usually 0.3 to 0.6 lag). The line experiences IXL drop due to this lagging current. Switching in shunt capacitors compensate this inductive reactance, thereby, decreasing the IXL drop. Thus, shunt capacitors can be used to control the line voltage when the load is highly inductive.

Voltage control by using synchronous condenser

A synchronous condenser is basically an over-excited synchronous motor running on no-load. Synchronous condensers are also called as synchronous phase modifiers. A synchronous condenser is located near the load end and can inject or absorb reactive power. And, thus, a synchronous phase modifier improves the voltage profile.
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What is a terminal block? | Significance and Types

How do we connect two wires? By stripping the insulation at the ends and twisting them together? Yes, it works. But, is it safe? We can apply insulation tape over the joint or use a wire connector. But what if there are a number wires that need to be joint/connected near each other? Or, what if multiple outgoing wires are to be connected to a single incoming wire? Then this method will neither be safe nor be convenient anymore. Here we use terminal blocks.

What is a terminal block?

A terminal block (also called as connection terminal or terminal connector) is a modular block with an insulated frame that secures two or more wires together. It consists of a clamping component and a conducting strip. A typical simplest terminal block is as shown in the image below.
screw clamp terminal block
Image Credit: Wikimedia Commons

The insulating body of a terminal block houses a current carrying element (a metal strip or terminal bar). It also provides a base for clamping element. The body has a mounting arrangement so that the block can be easily mounted on or unmounted from a PCB or a mounting rail. Most terminal blocks are usually modular and mounted on DIN rail. That allows us to increase the number of terminals according to the requirements. Terminal blocks keep connections much more secure and wires well organized.

Types of terminal blocks

Electrical terminal blocks can be classified on the basis of structure, device type, termination options etc.
single level pass through or feed through terminal block
Single level pass through terminal block

Structure type

  • Single level pass-through terminal blocks: These are simply used to connect two wires together, i.e. wire-to-wire connection. These are also called as single feed terminal blocks. Single level terminal blocks are of the most simple type having one input contact and one output contact.
  • Dual level terminal blocks: These blocks have another level of connection terminal stacked on the first one. This arrangement is generally used to save space.
  • Three level terminal blocks: Just like dual level blocks, these have an extra level at the top. An advantage of using multilevel blocks is that multiple connections can be made in the same block.
dual level (duble decker) and three level terminal block
Image credits: Connectwell.com

Device type

ground terminal block and fuse terminal block
Image credits: Connectwell.com

- Ground terminal blocks

These blocks often look like a single level feed through terminals. The exception is that these blocks and the metal connection where the wire is terminated are grounded to the panel or DIN rail on which the block is mounted.

- Fused connection terminals

These are similar to the pass-through blocks with an exception of the metal connection strip is replaced with a fuse. Therefore, the wires will be connected through a fuse providing an added protection.

- Thermocouple terminal blocks

These are designed to accept thermocouple lead connections. Some thermocouple connectors essentially clamp the thermocouple leads together on both sides of the block, eliminating the metal connection strip inside the block. However, in some thermocouple blocks, the metal connection strip of the same metal as that of the wire may be present.

- I/O blocks and sensor blocks

I/O blocks are used to make a connection between a device and a controller. Whereas, sensor blocks handle three or four wire devices such as proximity sensors.

- Disconnect terminal blocks

These blocks allow wires to be easily disconnected just by lifting a lever or knife switch. They can be used for convenient disconnection and connection without removing the wires. They are also known as switch blocks.

- Power Distribution blocks

These blocks are used in electrical power distribution. An electric power distribution terminal block is a convenient, economical and safer way to distribute power from a single input source to multiple outputs. One large wire is connected to the input terminal of the block and multiple output terminals are provided at the output. This way, wires are well arranged in a control panel giving it a neat, clean and professional look.
electric power distribution terminal block
Image source: ABB e-library

Clamping options in terminal blocks

  • Screw terminal: Screw clamp terminals are the most common type of connection method. The wire or conductor is simply pressed against the conductor strip in the block by tightening the screw. Screw terminals accommodate a very wide range of wire or conductor sizes.
  • Spring clamp: These type of terminals use spring pressure to retain the wire clamped. Spring clamps are a newer alternative to screw clamps and are generally used for relatively small wires.
    spring clamp terminal block
    Image credit:C J Cowie | Altech Corp.
  • Push-in terminal blocks: Push-in terminals allow you to connect a wire simply by inserting it. Most push-in terminals require the use of a ferrule. A ferrule strengthens the end of the wire/conductor. However, some push-in terminal blocks allow to insert a solid conductor directly or a stranded conductor by inserting a screwdriver into the release hole.
  • Insulation Displacement Connector (IDC): These connectors do not require us to strip the insulation for contact. We simply need to insert the wire without stripping the insulation, and the two sharp metal blades inside the terminal will cut through it to the conductor making proper contact.
  • Barrier terminal block: These are used where vibration is an issue. A spade or ring terminal is attached to the wire and then inserted into a bolt and tightened with a nut on the terminal block. This prevents loosening of the wire due to vibrations.
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