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

Controlled Switching (CS) MethodControlled Switching (CS) is a technique used to eliminate harmful transients by precisely timing the switching operations of circuit breakers (CBs). The closing or opening commands to the CB are delayed in such a way that the contacts make or separate at an optimal phase angle, minimizing transient effects.Key Principles: Voltage Zero Crossing for Closing: To avoid switching transients, the moment of contact closure should ideally occur at the voltage zero crossi

SF6 Gas Density Monitoring System Components and Failure ModesThe SF6 gas density monitoring system comprises three main components: Gas Density Monitor Gas Pipes with Manifold (if applicable) Pressure (or Density) GaugeEach of these components can experience different types of failure modes.Gas Density MonitorGas density monitors are susceptible to several failure modes:• Mechanical Disturbances: The operational density values at which the switch operates can change due to mechanical s

What is a Ground Fault Overcurrent Relay in a Substation?A ground fault overcurrent relay is a protective device used to detect and protect against ground faults (also known as earth faults or single-phase ground faults) in power systems. It plays a crucial role in substations, ensuring the safety and reliability of the system.1. Working PrincipleThe primary function of a ground fault overcurrent relay is to monitor current imbalances in the power system, particularly detecting zero-sequence cur

Special Considerations for Shaft and Latch BearingsSpecial attention must be paid to the material specifications and design of shaft and latch bearings to ensure smooth operation, even after prolonged periods of inactivity. The moving contacts should still separate within approximately 25 milliseconds when the protection system issues an opening command.Key Design Features:Trip and Close Latches: These components are designed to be relatively lightly loaded to minimize the burden on trip and clo

Pole Discrepancy in Circuit BreakersPole discrepancy typically refers to differences in operating times between the three phases or poles of a switching device during the same operation. These discrepancies can affect the synchronization of the circuit breaker's poles, which is crucial for reliable operation.Challenges in Continuous MonitoringDetermining pole discrepancy on a continuous basis can be less accurate because it often relies on break time or make time recordings obtained through curr

Sensing PrinciplesSensing principles involve detecting changes in the state of light polarization due to various physical phenomena. These include:• Pockels Effect: Changes in polarization caused by an electric field.• Faraday Effect: Changes in polarization caused by a magnetic field.• Photoelasticity: Changes in polarization due to mechanical stress.• Thermochromic Effects: Changes in light characteristics due to temperature variations.• Mechan

Safety Systems to Prevent Grid-Tied Inverters from Supplying Power During Grid OutagesTo prevent grid-tied inverters from continuing to supply power to the grid during outages, several safety systems and mechanisms are typically employed. These measures not only protect the stability and safety of the grid but also ensure the safety of maintenance personnel and other users. Below are some common safety systems and mechanisms:1. Anti-Islanding ProtectionAnti-islanding protection is a critical tec

Factors Determining When to Start Grid Peaking UnitsThe timing for starting grid peaking units is primarily determined by multiple factors to ensure the stable operation and efficient use of resources in the power system. Below are the main factors that influence when to start peaking units:1. Load Demand Variations Peak Load Periods: During times when grid load reaches or approaches its peak (such as during working hours or summer air conditioning usage peaks), additional generation capacity is

Current Chopping and Reignition in Circuit Breakers Handling Small Inductive CurrentsWhen a circuit breaker (CB) opens or closes shunt reactor banks or unloaded power transformers, it typically switches small inductive currents, usually several tens of amperes, with a 90-degree lag relative to the voltage phase. However, these currents are often prematurely forced to zero by a phenomenon known as current chopping. This can result in chopping overvoltages and subsequent reignition overvoltages, w

Circuit Breakers Circuit breakers (CBs) are designed to switch on and off any type of current up to their rated current. This includes both load currents and short-circuit currents. CBs installed in overhead systems should be capable of performing successful and unsuccessful auto-reclosing operations.Load Break Switches Load break switches (LBS) can handle switching load currents under normal operating conditions but lack the capability to switch short-circuit currents. They are suitable for nor