Shakeel Ahmed,B.E(EEE),M.Tech (EPS)’s Post

For interrupting main circuit current Id, the operating mechanism open contact S2 and closes contact S1. This indicates discharge of capacitor C through inductance L, main contact M and auxiliary contact S1 setting up an oscillatory current shown in the figure below. Thus, artificial current zeros are created, and the circuit breaker main contact M is opened at a current zero. After that, contact S1 is opened, and contact S2 is closed. Another way of interrupting the main direct current is by its diversion to the capacitor so that the magnitude of current to be interrupted by the circuit breakers becomes smaller. This is shown in the figure below. The capacitor C is initially uncharged. When the main contact M opens, the main circuit current is diverted to the capacitor C. Thus, the current to be interrupted by the main contacts M becomes smaller. The nonlinear resistor R absorbs energy without greatly adding to the voltage across the main contact M.   The rate of rising of the recovery voltage across M is expressed as  The problem of prevention of restrikes is very intense in oscillating current DC circuit breakers where the time in which the current is chopped is very small. Thus, the steep surge of the restriking voltage across breaker terminals is produced, and the circuit breaker must be capable of withstanding this voltage.

50Hz Transformer at 60Hz: 1. 20% increase in impedance 2. Greater voltage drop 3. Increased reactive power losses 4. Transformer may run hotter, potentially reducing lifespan 60Hz Transformer at 50Hz: 1. Not advisable without adjustments 2. Voltage reduction required to maintain V/F ratio 3. Risk of overloading and damage if operated without adjustments General Principles: 1. Transformers are designed to operate within specific frequency ranges. 2. Operating at off-frequency conditions can lead to efficiency losses, overheating, and reduced lifespan. 3. Voltage and frequency adjustments may be necessary to ensure safe and efficient operation. Additional Considerations: 1. Consult manufacturer guidelines for specific transformer models. 2. Assess potential impact on overall system performance and safety. 3. Consider rewinding or replacing transformers if frequency conversion is necessary.

✨ Ongoing sharing of expertise, click to follow if you are interested. ⭐ DC Fuse vs. AC Fuse: Key Differences and Applications Fuses are crucial for protecting electrical systems, but did you know there's a significant difference between DC and AC fuses? Here’s a detailed look to help you understand and choose the right one. 🌟 System Differences DC System: Continuous current, no zero-crossing point. When a fuse blows, a plasma arc can form and sustain. AC System: Goes to zero volts each cycle, extinguishing plasma arcs naturally. 🌟 Voltage Ratings AC Fuses: Rated at 65V, 125V, 250V, 500V, 690V, 12KV, up to 40.5KV. Current ratings from 250mA to 20000A. DC Fuses: Rated at 12V, 32V, 500VDC, 1000VDC, 1500VDC, or customized voltages. 🌟 Characteristics of DC Fuses Time Delay: Longer melting time for small overloads; short for large overloads. Purpose: Protects against equipment damage due to unstable currents by breaking the circuit during overcurrent situations. 🌟 Why Use DC Fuses? Protection: Essential for preventing damage from continuous rising currents, which can lead to fires or equipment failure. 🌟 Applying Overcurrent Protection Devices (OCPD) AC vs. DC: AC systems have zero-crossing points aiding in arc suppression. DC systems need larger gaps to handle continuous arcs. Considerations: Voltage must match the fuse's rating to avoid bursting and ensure safety. 🌟 Key Differences Arcing: AC Fuses: Handle frequent zero-crossing points, extinguishing arcs easily. DC Fuses: Designed with arc-extinguishing features due to sustained arcs. Voltage Rating: AC fuses are rated for specific AC voltages. DC fuses are voltage-specific, handling continuous current. Polarity: AC circuits have no polarity. DC circuits have specific polarity and require correct orientation. Interrupting Capacity: AC fuses have lower interrupting capacities. DC fuses have higher capacities to manage sustained arcing. Using the right fuse for your AC or DC circuit is crucial for safety and functionality. #DCFuses #ACFuses #CircuitProtection #ElectricalSafety #BussmannFuses #ElectricalEngineering #SystemProtection #Littelfuse #Mersen #SIBA #Cooper #ABB

Here are five common faults that can occur on a voltage regulator and their remedies: 1. **Overheating**: This can be caused by excessive current flow or poor ventilation. The remedy is to ensure proper airflow around the regulator and to check for any excessive current draw in the system. 2. **Voltage Instability**: Fluctuations in the output voltage can occur due to internal component failure or external factors. The remedy involves checking and replacing faulty internal components, as well as ensuring a stable input voltage from the power source. 3. **Short Circuits**: These can occur due to damaged wiring or internal component failure. The remedy is to carefully inspect the regulator for any signs of damage and replace any faulty components or wiring. Components like the relay especially. 4. **Under Voltage**: This may occur due to an inadequate input voltage or regulator failure. The remedy involves checking the input voltage to ensure it meets the regulator's requirements. 5. **Overvoltage**: This can occur due to regulator malfunction or sudden spikes in input voltage. The remedy is to install protection circuits to prevent voltage spikes.

#100daysamplifierdesign Day 87 Power Failure Alarm Circuit Power Failure Alarm Circuit is designed to notify users when there is an interruption in the power supply. Detailed aspects include: Detection Mechanism: The circuit monitors the voltage level of the power supply. It uses voltage detectors or comparators that trigger an alert when the voltage drops below a predefined threshold. This ensures timely notification of power loss. Alarm Triggering: When a power failure is detected, the circuit activates an alarm system. This could be a visual indicator like an LED, an audible alarm like a buzzer, or both. The alarm remains active until the power is restored or the user acknowledges the alert. Backup Power: To ensure the alarm operates during a power outage, the circuit often includes a backup power source such as a battery or capacitor. This allows the alarm to function independently of the main power supply during an outage. Testing and Calibration: Regular testing and calibration ensure the circuit responds accurately to power failures and avoids false alarms. This involves setting the correct voltage thresholds and testing under various conditions.

The Transient Recovery Voltage (TRV) is directly related to the rated short-circuit breaking capacity of a circuit breaker. This is because TRV behavior is most critical during the interruption of fault currents. Here's how it connects: 1️⃣ Rated Short-Circuit Breaking Current Definition: The maximum fault current the circuit breaker can safely interrupt without restrikes or failure. Relevance to TRV: When a fault is interrupted, the rapid extinction of the arc generates a steep voltage transient. A higher short-circuit current results in a more severe TRV waveform, particularly in terms of its amplitude and rate of rise. 2️⃣ Rated Voltage The TRV waveform is proportional to the system voltage. For higher-rated voltage systems (e.g., 132 kV, 220 kV, 500 kV), the TRV amplitude and steepness are more pronounced. 3️⃣ TRV Performance Parameters Defined by Standards Standards such as IEC 62271-100 and IEEE C37.04 define TRV parameters for various CB ratings. These include: Peak TRV Amplitude: The maximum voltage the CB must withstand after interruption. Rate of Rise of Recovery Voltage (RRRV): The speed at which the TRV rises immediately after arc extinction, expressed in kV/µs. 4️⃣ Rated Interrupting Time The shorter the interrupting time, the steeper the TRV and RRRV the breaker will experience. Modern EHV circuit breakers often have fast interrupting times, necessitating high TRV withstand capabilities. Summary Table: CB Ratings & TRV CB RatingImpact on TRVRated VoltageHigher voltage → Higher TRV amplitude.Rated Short-Circuit CurrentHigher fault current → Steeper TRV waveform.Interrupting TimeShorter time → Higher RRRV. Conclusion: When selecting a circuit breaker, ensure that its TRV withstand capability (as defined in its test certificates and standards) matches or exceeds the TRV requirements of your system. This ensures safe and reliable fault interruption.

Transient Recovery Voltage (TRV) is a critical parameter for high-voltage circuit breakers, representing the voltage across the terminals after a current interruption. It significantly influences the circuit breaker's ability to interrupt fault currents and maintain system stability. Key factors affecting TRV include system voltage, short-circuit current, source impedance, and fault type. The TRV waveform can vary based on the circuit configuration, with common shapes being cosine, exponential cosine, and triangular waveforms. To mitigate TRV effects, methods such as shunt reactors, shunt capacitors, and controlled switching techniques are employed. These approaches help manage the rate of rise and peak values of TRV, enhancing circuit breaker performance and overall power system reliability. As power systems evolve with increased interconnections and renewable energy integration, advanced circuit breaker technologies and real-time monitoring are essential for effective TRV management. Understanding these dynamics is crucial for selecting appropriate circuit breakers that can withstand transient conditions without failure.

What is Surge Protective Device? A surge protective device, also known as a surge protector or SPD, is designed to safeguard electrical components against surges in voltage that might happen in the electrical circuit. Whenever a sudden increase in current or voltage is produced in the electrical circuit or communication circuit as a consequence of outside interference, the surge protection device may conduct and shunt in a very short period of time, preventing the surge from damaging other devices in the circuit. Surge protective devices (SPDs) are essential in protecting electronic equipment from the harmful effects of transient overvoltage that can cause damage, system downtime, and data loss. In many cases, the cost of equipment replacement or repair can be significant, particularly in mission-critical applications such as hospitals, data centers, and industrial plants. Circuit breakers and fuses are not designed to handle these high-energy events, making additional surge protection necessary. While SPDs are specifically designed to divert transient overvoltage away from the equipment, protecting it from damage and prolonging its lifespan. In conclusion, SPDs are essential in the modern technological environment.

There are several ways to perform a transformer stability test, however, I will explain one of the ways we choose to perform this test. Inject from the LV busbar and measure the results in the transformer protection and transformer LCP panel. But before injecting make sure to prevent false tripping and unnecessary availability of voltage in HV bus bar, we must take into consideration. Calculate the required LV and HV currents of the power transformer for differential and restricted earth faults and also calculate the required CT secondary results for verification of these parameters during injection. LV Side: Since we are going to inject into the LV busbar from the outgoing panel, the corresponding CT link must be shorted. Closed both CB of outgoing and incomer feeder so that power reaches LV terminal of transformer and make sure to rack out VT. Make MCB off the trip circuit and connect the cable from the generator to any outgoing feeder from the LV busbar. HV side: On HV side voltage should reach to CT of transformer bay, therefore,open high speed earth switch & close circuit breaker to provide path for current, but we don’t need current up to HV busbar, so make sure to close earth switch after circuit breaker so that small HV current after passing through CB direct toward earth.

#100daysamplifierdesign Day 87 Power Failure Alarm Circuit Power Failure Alarm Circuit is designed to notify users when there is an interruption in the power supply. Detailed aspects include: Detection Mechanism: The circuit monitors the voltage level of the power supply. It uses voltage detectors or comparators that trigger an alert when the voltage drops below a predefined threshold. This ensures timely notification of power loss. Alarm Triggering: When a power failure is detected, the circuit activates an alarm system. This could be a visual indicator like an LED, an audible alarm like a buzzer, or both. The alarm remains active until the power is restored or the user acknowledges the alert. Backup Power: To ensure the alarm operates during a power outage, the circuit often includes a backup power source such as a battery or capacitor. This allows the alarm to function independently of the main power supply during an outage. Testing and Calibration: Regular testing and calibration ensure the circuit responds accurately to power failures and avoids false alarms. This involves setting the correct voltage thresholds and testing under various conditions.