ßob Terence

08/01/2026

Earthing System.

Earthing is a safety system that connects non-current-carrying metal parts of electrical equipment to the earth. Its main purpose is to protect people and equipment from electric shock, fire, and damage due to fault currents.

Good Earthing Resistance Value
Domestic: ≤ 5 Ohms
Industrial: ≤ 1 Ohm
Substation: ≤ 0.5 Ohm

20/12/2025

18/12/2025

Every Design Engineer Should Know This: Busbar Sizing Guide (IEC + NEC)

Just found this extremely valuable guide on How to Select & Calculate Busbar Size (IEC & NEC)— perfect for anyone in solar, electrical, or power system design. ⚡📐

It includes:
👉 Accurate design current calculation
👉 Correct derating methods
👉 Cross-section selection tips
👉 IEC & NEC references
👉 Real working examples for practical use

If you're working on LV panels, SLDs, HT/LT design, or simply upgrading your engineering knowledge, this is a must-read. 🚀

30/11/2025

Les condensateurs,
Pourquoi on les utilise dans une installation triphasée ? ⚡

1. Amélioration du facteur de puissance (cos φ)

Dans une installation triphasée, beaucoup de charges (moteurs, compresseurs, etc.) absorbent de la puissance réactive inductive.

Cette puissance réactive ne produit pas de travail utile, mais surcharge le réseau.

Les condensateurs apportent une puissance réactive capacitive qui compense celle absorbée par les inductances → le cos φ se rapproche de 1.

2. Réduction des pertes Joule

Quand le facteur de puissance est faible, le courant augmente pour la même puissance active.

Cela entraîne des pertes .

En améliorant le cos φ, le courant baisse, donc les câbles chauffent moins.

3. Diminution de la section des câbles et du coût de l’installation

Moins de courant = possibilité d’utiliser des câbles, transformateurs et protections de taille plus réduite.

4. Stabilisation de la tension

En réduisant la chute de tension dans les lignes, la tension aux bornes des récepteurs devient plus stable.

5. Éviter les pénalités de l’opérateur électrique

Les distributeurs d’électricité facturent ou pénalisent les clients qui ont un mauvais facteur de puissance (cos φ bas).

La compensation permet donc de réduire la facture.

🛠️ Exemple pratique :

Supposons un moteur triphasé de 30 kW avec cos φ = 0,7.

Il va tirer beaucoup de puissance réactive du réseau.

En installant une batterie de condensateurs, on corrige le cos φ vers 0,95 →

Courant réduit,

Pertes moindres,

Économie d’énergie,

Meilleure efficacité globale.

✅ En résumé :
Les batteries de compensation dans une installation triphasée servent à corriger le facteur de puissance, réduire les pertes, stabiliser la tension et éviter des coûts supplémentaires.

31/08/2025

🔋 Generator Calculations – kVA, Current, Fuel & Efficiency

Generators are the backbone of backup power systems in plants, hospitals, and data centers.
Sizing them correctly ensures you avoid overload, blackouts, and wasted fuel.

1️⃣ Generator Rating (kVA & kW)
S (kVA) = (√3 × V × I) ÷ 1000 (3-phase)
P (kW) = S × PF
🔹 V = Line voltage
🔹 I = Line current
🔹 PF = Power factor (usually 0.8–0.9 for industrial loads)

Example:
1000 kVA generator, PF = 0.8 →
P = 1000 × 0.8 = 800 kW

2️⃣ Generator Current Calculation
Current (A) = (kVA × 1000) ÷ (√3 × V)

Example:
1000 kVA, 415 V →
I = (1000 × 1000) ÷ (1.732 × 415) = 1391 A

3️⃣ Fuel Consumption
Approximate diesel consumption:
🔹 0.24–0.28 liters/kWh at full load

Example:
500 kW load, generator efficiency 0.25 L/kWh →
Fuel = 500 × 0.25 = 125 L/hr

Note: At partial load, fuel consumption per kWh increases (less efficient).

4️⃣ Generator Efficiency
η (%) = (Output Power ÷ Input Power) × 100
🔹 Input Power = (Fuel energy × efficiency factor)
🔹 Typical diesel gen sets: 35–40% efficiency

5️⃣ Sizing Guidelines
🔹 Continuous load should not exceed 70–80% of rated kVA.
🔹 For motor starting, consider inrush → size genset 2–3 × largest motor rating.
🔹 Parallel generators for redundancy and load sharing in data centers & hospitals.

6️⃣ Short Circuit Contribution
Generators contribute limited short-circuit current (typically 3–5 × rated current for a few cycles).
🔹 Important for breaker selection & protection coordination.

🧠 Field Tips from Experience

🔹 Always size based on site load study, not just connected load.
🔹 Never run generators for long time at

10/08/2025

A = kW + kVAR

> ⚡ Understand Power Triangle once and for all
Apparent Power (kVA) = Real Power (kW) + Reactive Power (kVAR)
Crucial for motors, transformers, and load calculations.

06/08/2025

What is an Auto Transfer Switch (ATS)? Important Note:

An Auto Transfer Switch is an electrical device that automatically switches the power supply from the main source (like utility power/WAPDA) to a backup source (like a generator or inverter) when it detects a power failure. Once the main power is restored, it automatically switches back.
Working Principle of ATS:

When utility power is available and within safe voltage limits, the ATS connects the load (your house, building, etc.) to the utility.

2. Power Failure (Utility Power Fails):

When the main power goes off or voltage drops below safe levels, the ATS detects the failure.

The ATS then sends a signal to start the generator (if it's an automatic type).

After the generator starts and stabilizes, the ATS transfers the load from the utility to the generator.

3. Restoration (Utility Power Returns):

The ATS keeps monitoring the utility supply.
When the utility power comes back and becomes stable, the ATS switches the load back to the utility.
Then, it stops the generator automatically.
Components Used in ATS:
Component Function
Voltage sensing relay Detects voltage presence or failure
Contactor / Power Relay Switches the load between sources
Timer Relay Delays switching to avoid false detection
Auto Start Controller Sends start/stop signals to the generator
Control Circuit Executes the logic of switching automatical...

16/07/2025

MCCB, ELCB, and RCCB – Understanding the Differences ⚡

In electrical systems, safety and protection are paramount. Here's a quick comparison of three essential protective devices:

🟨 MCCB (Molded Case Circuit Breaker)

Protects Against: Overload & Short Circuit

Sensitivity: High Current

Used In: Industrial applications with large loads

Tripping Mechanism: Thermal & Magnetic

🟨 ELCB (Earth Leakage Circuit Breaker)

Protects Against: Earth Leakage

Sensitivity: Leakage Current

Used In: Residential & Industrial setups

Tripping Mechanism: Voltage/Current Sensing

🟦 RCCB (Residual Current Circuit Breaker)

Protects Against: Residual Current (Earth Faults)

Sensitivity: Very small leakage currents

Used In: Homes, Offices, and Industrial units

Tripping Mechanism: Detects Current Imbalance

💡 Choosing the right device ensures optimal protection for people and equipment.
🔧 MCCB for overload & short circuits,
🔌 ELCB for basic earth leakage,
🛡 RCCB for precise leakage protection.

14/07/2025

Understanding VMR – Voltage Monitoring Relay 🔍

A Voltage Monitoring Relay (VMR) is an essential protective device used in electrical systems to continuously monitor voltage levels and protect equipment from overvoltage, undervoltage, phase loss, or phase imbalance.

✅ Key Functions:
• Monitors supply voltage in real-time
• Trips the circuit during abnormal voltage conditions
• Helps in preventing damage to motors, compressors, and sensitive electronic devices

📍 Widely used in:
• Industrial automation
• Control panels
• HVAC systems
• Motor protection

Ensuring voltage stability means ensuring safety, reliability, and longer equipment life.

16/06/2025

Types of Circuit Breakers:

🔹 1. MCB – Miniature Circuit Breaker
• Current range: Typically up to 100A.
• Application: Residential and small commercial installations.
• Function: Protects against overload and short circuit conditions.
• Note: Fixed trip settings, not adjustable.

🔹 2. MCCB – Molded Case Circuit Breaker
• Current range: Up to 2500A.
• Application: Industrial and large commercial systems.
• Function: Protects against overloads, short circuits, and can have adjustable trip settings.
• Versatile: Suitable for higher power loads.

🔹 3. ACB – Air Circuit Breaker
• Current range: 800A to 6300A.
• Insulating medium: Air.
• Application: Low voltage switchgear (typically

04/06/2025

👷🏾

18/05/2025

TODAY WE WIll CONTINUE THE MOTOR CONTROL FUNDAMENTAL
1_ branch circuit molded case circuit breaker

(MCCBs) it's thermal magnetic or electronic trip mccb provide disconnect means short circuit protection and over load protection the magnet protection rapidly to large currents to provide short circuit protection while thermal protector react slowly to slightly increased current providing over load protection hom ever motors contain large amount of metal and heat and cool much more slowly than the conductors that are connected to it for this reason a thermal magnetic mccb does not provide suitable over load protection for amotor as result over load relays must be used for motor over load protection .
electronic trip mccb used a microprocessor to emulated the thermal magnetic tripping function and functions such as monitoring and metering and communication
1_branch circuit protection molded circuit breaker or mcb without the thermal over load protection .
branch circuit protection _fuses
fuses contain a metal or strip that is designed to melt at specific current values.
single element fuses provide short circuit protection and are only used for motor protection in conjunction with over load relay
fuses require a fuse block for mounting and disconnect switch for disconnect and control once a fuse melt it has to be replaced fuses have high rated and are easier than cbs it different rating required.
1_ branch circuit protection additional protection mini circuit breakers according to ul489 can be used as branch circuit protection in branches inside distribution boards control panel and controlsin.
PROTECTION



control protection
CIRCUIT