Free Expert Guides on Power Systems, Circuit Design & Electrical Troubleshooting

What is Protective Relay ?Protective Relay DefinitionA protective relay is an automatic device that senses abnormal conditions in electrical circuits and triggers actions to isolate faults.Types of Protective Relays Definite time relays Inverse time relays with definite minimum time(IDMT) Instantaneous relays IDMT with inst Stepped characteristic Programmed switches Voltage restraint over current relayOperating PrinciplesProtective relays operate by detecting abnormal signals, with specific pick

What is Differential Relay?Differential Relay DefinitionA differential relay is defined as a device that responds to the difference between two or more similar electrical quantities, such as currents or voltages, to detect faults.Principle of OperationThese relays activate based on discrepancies in electrical quantities within the protected zone, ensuring accurate fault detection.Types and ConfigurationsDifferential relays vary mainly into current and voltage balance types, each tailored for spe

What is an Instantaneous Relay ?Instantaneous Relay DefinitionAn instantaneous relay is defined as a relay that operates with no intentional delay when the current exceeds a set threshold.No Intentional DelayInstantaneous relays activate without any added delay, making them very fast in operation.Inherent DelaysThese relays still have minor delays due to electrical and mechanical factors, but they are not intentionally introduced.Types of Instantaneous RelaysExamples include attracted armature r

What is a Thermal Relay?Thermal relay definitionA thermal relay is defined as a device that uses unequal expansion rates of metals in a bimetallic strip to detect overcurrent conditions.Working principleThermal relays work by heating a bimetallic strip, causing it to bend and close the normally open contact, which triggers the circuit breaker.Construction of thermal relayIt consists of a bimetallic strip, metal with different expansion coefficients, a heating coil and contacts.Technical paramete

What is a Dry Contact ?Dry Contact DefinitionA dry contact is defined as a switch that controls electrical circuits without supplying the power itself, relying on an external source.FunctionalityDry contacts operate by opening and closing circuits, providing essential isolation and safety in electrical systems.Dry vs. Wet ContactsDry contacts are used for isolation, while wet contacts use the same power source for control and power supply, lacking isolation features.Applications of Dry ContactsT

What is a Latching Relay ?Latching Relay DefinitionA latching relay is a type of relay that maintains its contact position without continuous power application, allowing for efficient control of circuits.Circuit DiagramThe latching relay circuit diagram shows how Button-1 and Button-2 control the energizing and de-energizing of the relay, respectively.Operation MechanismBy pressing Button-1, the relay is energized and remains so even after the button is released, until Button-2 is pressed.Effici

What is Transformer Protection ?Transformer DefinitionA transformer is an electrical device that transfers electrical energy between circuits through electromagnetic induction.Nature of Transformer Faults Over current due to overloads and external short circuits Terminal faults Winding fault Incipient faultsTransformer ProtectionTransformer protection schemes are essential to prevent damages from faults and include devices like Buchholz relays and differential protection systems.Common FaultsTra

What is Generator Protection?Generator Protection DefinitionGenerator protection is the process of safeguarding generators from various electrical, mechanical, and thermal stresses.Types of ProtectionProtective relays are used to detect both internal and external faults, ensuring comprehensive generator protection.Insulation Failure ProtectionLongitudinal differential protection and inter-turn fault protection are crucial for preventing phase-to-phase and phase-to-earth faults.Rotor Fault Detect

What is Differential Protection?Differential Protection DefinitionDifferential protection is a method used to clear internal faults in the stator winding of a generator or alternator.Current TransformersTwo sets of current transformers (CTs) are used, one on the line side and one on the neutral side, and their characteristics must match to avoid relay malfunctions.Stabilizing ResistorA stabilizing resistor in series with the relay prevents operation due to external faults or CT saturation.Percen

What is Overvoltage Protection ?Overvoltage Protection DefinitionOvervoltage protection is defined as measures taken to prevent electrical systems from damage due to excessive voltage levels.Causes of OvervoltageOvervoltages can be caused by lightning, switching operations, insulation failure, arcing ground, and resonance.Switching ImpulseWhen a no-load transmission line is suddenly switched on or off, it can create a transient overvoltage in the system.Lightning ImpulseLightning can cause very