1. Basics of Protection, EE 50031 notes in English,

 These are short notes for revision purpose. please refer you Reference book & College study materials for complete study.

For Further Notes Join 📍

• WhatsApp Group - https://chat.whatsapp.com/DWpN7vYqSutBNXY9R5Q2Te
• Telegram Channel - https://t.me/BTER_Electrical_Branch

1. Basics of Protection

Electrical protection systems are crucial for the safe and reliable operation of electrical power systems. These systems are designed to detect faults or abnormal conditions and disconnect faulty parts of the system, ensuring that the rest of the system operates without interruptions. Let's look at the key concepts related to the basics of protection.

1.1 Necessity and Functions of Protective System

Necessity of Protective System:

• Safety of Equipment: Protective systems are necessary to protect electrical equipment (like transformers, generators, and motors) from faults such as short circuits, overloads, or ground faults. Without protection, these faults could damage or destroy costly electrical equipment.

• Safety of Personnel: These systems help ensure the safety of people working with or around electrical equipment. By isolating faulty circuits quickly, they prevent electrical shocks or fires.

• Continuity of Service: Protection systems minimize downtime by isolating faulty sections of the network and allowing unaffected sections to continue operating normally. This is crucial for maintaining the continuity of power supply.

Functions of Protective System:

• Fault Detection: The primary function of a protective system is to detect faults (abnormal conditions such as short circuits, overloading, or equipment failures).

• Fault Isolation: Once a fault is detected, the protective system disconnects the faulty part of the system (via circuit breakers or relays) to prevent further damage to the network and equipment.

• Minimization of Damage: By isolating the faulted portion quickly, the system helps prevent the spread of the fault to healthy sections of the network, thereby minimizing overall damage.

• Restoration of Service: After a fault is cleared, the protective system helps in the safe restoration of normal operation.

---

1.2 Normal and Abnormal Conditions

Normal Conditions:

• In a properly functioning electrical system, all components (such as generators, transformers, and transmission lines) are working within their designed operating limits.
• Voltage, current, frequency, and other operational parameters are within the specified limits.
• The electrical system is stable and reliable, with no signs of faults.

Abnormal Conditions:

• These refer to situations where electrical parameters deviate from their normal operating range, which could indicate a fault or potential failure. Examples include:
  • Overload: When a system component or circuit carries more current than it is designed to handle.
  • Short Circuit: When two conductors (e.g., live and neutral) come into direct contact, causing a surge in current.
  • Ground Fault: When the current takes an unintended path through the earth, causing a potential danger to both equipment and personnel.
  • Voltage Fluctuations: Voltage variations beyond the safe operating limits can damage electrical devices and affect system performance.

Protective systems detect these abnormal conditions and act quickly to prevent further damage.

---

1.3 Types of Faults and Their Causes

Electrical systems can experience a variety of faults that can disrupt power supply and damage equipment. Below are the types of faults and their causes:

1. Short Circuit Fault (S.C.):

   • Cause: This occurs when two conductors of different potentials (such as the live and neutral wire) come into direct contact, creating a low resistance path for current to flow.
   • Effect: It results in a large current flow, which can damage conductors and equipment.

2. Overload Fault:

   • Cause: An overload occurs when the current flowing through a circuit exceeds the rated capacity of the system. It can happen due to excessive load demand or a faulty load.
   • Effect: Overloading can cause overheating of conductors and equipment, leading to insulation failure or fire.

3. Ground Fault:

   • Cause: A ground fault occurs when a live wire comes into contact with the earth (ground), creating a path for current to flow to the ground.
   • Effect: Ground faults pose a serious risk of electric shock to personnel and can damage electrical equipment.

4. Phase-to-Phase Fault:

   • Cause: This fault occurs when two conductors of different phases come into contact with each other, creating a short circuit.
   • Effect: Similar to a short circuit, this causes an excessive flow of current, damaging equipment and disrupting service.

5. Open Circuit Fault:

   • Cause: This occurs when a conductor becomes disconnected or broken in the circuit, creating an open path.
   • Effect: It results in a loss of power supply to the affected section of the system.

6. Insulation Failure:

   • Cause: Insulation failure occurs when the insulation around conductors breaks down due to aging, moisture, or physical damage.
   • Effect: This can lead to short circuits, grounding faults, or leakage currents.

---

1.4 Protection Zones and Backup Protection

Protection Zones:

• Protection zones refer to sections of an electrical network or system that are protected by specific protective devices (such as relays and circuit breakers). These zones help to identify where faults occur and ensure that the fault is isolated without affecting other parts of the network.

  Examples of Protection Zones:

  • Generator Zone: Protects the generator from faults like short circuits, overloads, and overheating.
  • Transformer Zone: Protects transformers from faults such as short circuits and overloads.
  • Transmission Line Zone: Protects transmission lines from faults like short circuits or line breaks.

In a properly designed protection system, each zone is equipped with its own protection devices to detect and isolate faults in that specific zone. This approach ensures that faults do not propagate throughout the entire system.

Backup Protection:

• Backup protection refers to the additional protective devices that provide protection when the primary protective system fails or does not operate as expected. It ensures that if the primary protection fails to isolate the fault, the backup protection will step in and isolate the faulty section.

  Types of Backup Protection:

  • Time-graded Backup Protection: This type of backup protection operates after a predefined delay if the primary protection fails.
  • High-speed Backup Protection: This operates instantly if the primary protection system does not clear the fault within the required time.

Backup protection is essential to maintain the reliability of the system and prevent extensive damage to the electrical network.