Overhead system vs Underground system

The question is comparing an underground system to an overhead system, likely in the context of electrical or communication cabling (as depicted by the cables in the image). The question lists three statements about the underground system, and we need to determine which are true:

1. Has less chances of faults

2. Has more useful life

3. Is more costly

Let's analyze each statement based on general knowledge about underground vs. overhead systems:

1. Has less chances of faults:

Underground systems are generally less prone to faults because they are protected from environmental factors like weather (storms, lightning, wind), falling trees, or accidental damage from vehicles. Overhead systems, on the other hand, are exposed and more susceptible to such issues. This statement is true.

2. Has more useful life:

Underground cables are typically more durable over time since they are shielded from weather-related wear and tear, UV radiation, and physical damage. While maintenance can be more challenging, their lifespan is often longer than overhead systems, which degrade faster due to exposure.

This statement is also true.

3. Is more costly:

Installing an underground system is generally more expensive than an overhead system. It involves digging trenches, laying cables, and ensuring proper insulation and protection, which increases labor and material costs. Overhead systems are cheaper to install since they use poles and simpler infrastructure.

This statement is true as well.

Answer:

All three statements are correct:

- The underground system has less chances of faults.

- The underground system has more useful life.

- The underground system is more costly.

If this were a multiple-choice question where you need to pick one, the most emphasized difference in many contexts is often the cost (statement 3), but since the question doesn't specify, all three are accurate based on the comparison.

The FM transmitter circuit

The FM transmitter circuit depicted in the diagram below : 

is a simple design that converts audio signals from a microphone into FM radio waves for wireless transmission.

FM transmitter is a low power transmitter and it uses FM waves for transmitting the sound.

FM transmitter circuit can produce the radio frequency waves which are transmitted through the antenna. a microphone is used as a source of an audio signal.

The circuit is powered by a 3 to 6V battery, specifically a 3.7V 150mAh EH 302030 lithium-ion battery.

The audio input is captured by a microphone, which feeds into a 1nF capacitor and a 4.7kΩ resistor, forming part of the input stage to condition the audio signal.

The core of the transmitter is the 2N2222A transistor, which amplifies the audio signal and modulates it onto a carrier frequency determined by the 0.1µH inductor and the 6.8pF and 47pF capacitors, creating the FM signal.

This signal is then transmitted via an antenna. The 100Ω resistor helps stabilize the circuit, while the capacitors manage the frequency tuning and signal coupling.

This type of FM transmitter is commonly used for short-range applications, such as broadcasting audio to nearby FM radios, wireless microphone systems, or DIY audio projects, making it a popular choice for hobbyists and educational purposes due to its simplicity and low cost.

How to determine a branch circuit?

A branch circuit is a portion of an electrical wiring system that extends from the final overcurrent protection device, such as a circuit breaker in a main panel, to the outlets, switches, or devices it powers.

To determine a branch circuit, you start by identifying its origin at the main panel, where the circuit breaker connects to the hot bus bars (L1 and L2 in the diagram) and the neutral bus (N), along with a ground (G) for safety.

The diagram illustrates a 240V, single-phase supply from the utility, feeding into the main panel, where the branch circuit begins.

From the breaker, the circuit extends through wiring—typically consisting of a hot wire (black or red), a neutral wire (white), and a ground wire (green or bare)—to various loads like a light fixture controlled by a switch and an outlet.

The path from the breaker to the first device is the branch circuit's starting point, and it ends where the load is connected, such as the light or outlet. In the image, the branch circuit is shown powering a light fixture through a switch and an outlet, demonstrating how the circuit branches out to serve multiple devices while being protected by a single breaker, ensuring safe distribution of electricity within a building.

Calculating the Maximum Short-Circuit Current (SCA) for the Transformer

We previously published in a post how to calculate the Percentage Impedance of a transformer.

As requested by some friends, from Z%, the maximum short-circuit current (SCA) is calculated.

Calculating the Maximum Short-Circuit Current (SCA) for the Transformer

Transformer data is as follows:  

25 MVA & 66/11 kV  

Z = 10% (Impedance)

SCA: Short Circuit Current  

FLA: Full Load Current  

1. First, calculate the maximum load current of the transformer (secondary winding):

• P = 1.73 × V × I  

• 25,000 = 1.73 × 11 × I  

Maximum Full Load Current:  

   I = 25,000 / (1.73 × 11)  

   I = 1313 A (1313 Amperes)  

2. Second, calculate the short-circuit current using the following equation:

   Full Load Current = Short Circuit Current × Impedance (Z%)  

   I (Full Load) = I (Short Circuit) × Z%  

   I (Short Circuit) = I (Full Load) / Z%  

   I (Short Circuit) = 1313 / 10%  

   I (Short Circuit) = 13130 A  

   = 13 kA

How to Select the Proper Wire Cable for House Wiring

How to Select the Proper Wire Cable for House Wiring

1/ Selecting the right wire for house wiring is crucial for safety and efficiency.

Always choose the best quality wires—avoid cheap options. Most short circuits and fires are caused by low-quality wires. Don’t compromise on safety!

2/ There are two main types of wires: copper and aluminum. Copper wires are generally preferred for house wiring due to their superior conductivity and durability. Aluminum wires are cheaper but less efficient and more prone to issues.

3/ Always opt for high-quality copper wires.

They have less heat loss, higher conductivity, and are more reliable for long-term use. This ensures your electrical system runs efficiently and safely.

4/ Pay attention to insulation! Choose wires with proper insulation like FR (Flame Retardant), FRLW (Fire Resistant Low Smoke), or HRFR (Heat Resistant Flame Retardant). These types reduce fire risks and are safer for home use. 

5/ Select the wire size based on the appliance’s power requirements:  

- Use 1 to 1.5 mm² wires for low-power appliances (lights, fans, etc.).  

- Use 2.5 to 4 mm² wires for high-power appliances (ACs, heaters, etc.).  

Matching wire size to load prevents overheating. 

6/ For the main power supply, use thicker cables like 6-10 mm² copper wires. These can handle higher loads and ensure safe distribution of electricity throughout your home. Don’t cut corners here—safety first! 

7/ Bonus Tip: Always consult a licensed electrician before finalizing your wiring plan. They can help you choose the right wires, calculate load requirements, and ensure your home’s electrical system is safe and up to code.

8/ Remember, proper wiring isn’t just about functionality—it’s about safety, efficiency, and peace of mind. Invest in quality materials and professional guidance to protect your home and loved ones.

Team SparkED 

Understanding Fault Duration, Protection Relay Operation, and Total Fault Clearing Time in Electrical Systems

Some colleagues asked me about the difference between fault duration and the operating time of a protection relay.

Initially, we discussed in a previous post that a fault is divided into three parts: Pre-fault, Fault, and Post-fault.

The Pre-fault phase is the beginning of the fault. Let's assume the protection relay operating time is 1.5 seconds. 

If a fault occurs but does not last for 1.5 seconds, it is called a Transient Fault, such as an Inrush Current fault in transformers.

If the fault persists for 1.5 seconds, the protection relay sends a Trip signal to the circuit breaker (C.B).

The Tripping Time of the circuit breaker is the time measured during the circuit breaker tests, along with the Closing Time.

There is another time called the C.B Arcing Time, which is the time required to extinguish the arc generated during the tripping process, typically ranging between 5 and 10 milliseconds.

The sum of these three times is called the Total Fault Clearing Time, which is the total time required to isolate the fault.

Automatic Water Level Controller: Efficient Management of Water Supply Systems

This is an Automatic Water Level Controller system, commonly used to manage water levels in overhead and underground water tanks. 

Components:

1. Automatic Water Level Controller:

   - This device monitors and controls the water levels in tanks automatically. It typically includes controls for setting water levels and indicators for operational status.

2. Power Supply (220 Volt):

   - Provides the necessary electrical power to operate the controller and the water pump.

3. Water Tank (Overhead):

   - The upper tank where water is stored for distribution. It is monitored by the controller to prevent overflow.

4. Water Tank (Underground):

   - A lower tank that stores water, typically filled by the pump when the overhead tank needs to be replenished.

5. Water Pump:

   - This device is responsible for moving water from the underground tank to the overhead tank when needed.

6. Water Level Sensors:

   - These sensors are placed in both the overhead and underground tanks. They detect the water level and send signals to the controller.

   - Types of Sensors:

     - Low-Level Sensor: Activates the pump when the water level in the overhead tank drops below a certain point.

     - High-Level Sensor: Stops the pump when the overhead tank reaches its maximum level.

Working Operation:

1. Monitoring Water Levels:

   - The sensors continuously monitor the water levels in both tanks. When the overhead tank's water level falls below the low-level sensor, it sends a signal to the controller.

2. Activating the Pump:

   - Upon receiving the signal from the low-level sensor, the controller activates the water pump, which begins to draw water from the underground tank.

3. Filling the Overhead Tank:

   - The pump fills the overhead tank with water. As the water level rises, the high-level sensor will eventually be triggered.

4. Stopping the Pump:

   - Once the high-level sensor is activated, the controller stops the pump to prevent overflow in the overhead tank.

5. Manual Override:

   - The controller may also have manual controls (like the ON/OFF button) to allow for manual operation if required.

Summary:

This automatic water level controller system efficiently manages the water levels in overhead and underground tanks, ensuring a constant supply of water while preventing overflow and dry running of the pump. It automates the process, reducing the need for manual intervention and conserving water.