DefinitionInstruments that utilize a permanent magnet to generate a stationary magnetic field within which a coil moves are known as Permanent Magnet Moving Coil (PMMC) instruments. They operate on the principle that torque is exerted on a moving coil situated in the magnetic field of a permanent magnet. PMMC instruments provide accurate results for direct current (DC) measurements.Construction of PMMC InstrumentThe moving coil and the permanent magnet are the key components of a PMMC instrument

Key Differences Between Glass and Porcelain InsulatorsBoth porcelain and glass insulators are widely applied in power transmission and distribution to insulate overhead line conductors from supporting towers and poles. With extended service lives and suitability for high voltage ratings, their unique characteristics and properties define their distinct application scenarios.Porcelain InsulatorsPorcelain, a ceramic material, is valued for its absence of internal defects such as voids, cracks, or

Key Differences and Comparison Between Underground and Overhead Power Transmission & DistributionPublic SafetyIn terms of public safety, underground systems outperform overhead transmission systems. With all transmission and distribution components buried, underground setups minimize risks from obstacles and external interference. Additionally, they are less susceptible to environmental factors like wind, storms, and heavy rain, making them inherently more secure.Initial CostUnderground syst

In an electrical power system, various devices are utilized to enhance power factor and operational efficiency. Shunt capacitors and shunt reactors represent two distinct components designed to optimize the performance of electrical grids. This article explores their key differences, beginning with an overview of their fundamental principles.Shunt CapacitorsA shunt capacitor refers to a single capacitor or a group of capacitors (termed a capacitor bank) connected in parallel to the power system.

Insulation Performance：Air - insulated Circuit Breakers: They use air as the insulating medium. The insulation performance of air is relatively limited. In harsh environments such as high humidity and high pollution, the insulation performance is easily affected. They are suitable for medium - and low - voltage applications.Gas - insulated Circuit Breakers: Commonly, gases such as sulfur hexafluoride (SF6) are used. They have excellent insulation performance and can withstand higher voltages, ma

A stationary generator must never be connected to live busbars, as the induced electromotive force (EMF) is zero at standstill, which would cause a short circuit. The synchronization procedure and the equipment used for checking it are identical whether one alternator is to be connected in parallel with another alternator or an alternator is to be connected to an infinite bus.Synchronisation via Synchronising LampsA set of three synchronizing lamps can be employed to verify the conditions for pa

Prevention of incorrect opening/closing of circuit breakers:Mechanical interlock: The operating handle must be inserted into a specific position and operated in sequence, directly restricting incorrect opening/closing.Electrical interlock: The closing circuit of the circuit breaker is connected in series with the auxiliary contact of the disconnector. Closing is prohibited if the disconnector is not fully closed.Prevention of load-breaking operation of disconnectors:Mechanical interlock: The ope

TypesElectromagneticElectro-pneumaticPneumaticInterrupting MediumAirOilSF6 gasVacuumRated values of voltagesRated voltage (Operational voltage)：For a three phase contactors, the voltage between phases is called rated voltage or operational voltage.Rated Insulation Voltage：The voltage, on which performs the dielectric test.Rated Values of CurrentRated Thermal Current: The maximum current, on which a Contactor operates continuously for eight (8) hours without increasing the temperature (increased

Charging Current in Transmission LinesIn a transmission line, air serves as the dielectric medium between conductors. When voltage is applied to the sending end, current begins to flow between conductors due to the imperfect insulating properties of the dielectric. This current is known as the charging current of the transmission line.In other words, the current associated with the line capacitance is defined as the charging current. The magnitude of charging current depends on the line voltage,

What is an Electric Busbar?An electric busbar is a conductor or set of conductors designed to collect electrical power from incoming feeders and distribute it to outgoing feeders. Functionally, it serves as a junction where inflowing and outflowing currents converge, acting as a central hub for power aggregation and distribution.Outdoor Busbar InstallationsIn high-voltage (HV), extra-high-voltage (EHV), and outdoor medium-voltage (MV) systems, bare busbars and connectors are typically used, with