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

DefinitionConducting a full - load test on a small transformer is quite convenient. However, when it comes to large transformers, this task becomes extremely challenging. The maximum temperature rise in a large transformer is typically determined through a full - load test. This particular test is also known as the back - to - back test, regenerative test, or Sumpner’s test.Finding a suitable load that can absorb the full - load power of a large transformer is not an easy feat. As a result, a si

For intelligent switchgear, the opening time is defined as the duration starting from the moment when the first message carrying the trip command (a GOOSE message in accordance with the IEC61850 series) is received through the interface, with the circuit - breaker initially in the closed position, and ending at the instant when the arcing contacts of all poles are separated.Regarding the closing time of intelligent switchgear, it refers to the time span from the reception of the first message co

Open circuit tests and short circuit tests are two fundamental methods used in transformer testing to separately determine core losses and copper losses.Open Circuit Test (No-Load Test)In an open circuit test, a rated voltage is typically applied to one winding while the other winding is left open. This setup is primarily used to measure core losses for the following reasons:Core losses mainly consist of hysteresis losses and eddy current losses, which occur in the transformer's core. When an AC

Over - voltage and Over - current Aspects Ferroresonant over - voltage: In a non - effectively earthed neutral system, the magnetic circuits of equipment such as transformers, voltage transformers, and arc suppression coils may saturate, potentially triggering ferroresonance. The resulting over - voltage can increase the excitation current of the voltage transformer by dozens of times. Operating under high voltage and large current for an extended period causes the temperature of the transformer

I. Definitions of Losses in IEC 6007IEC 60076-1 (General Requirements) and IEC 60076-7 (Loading Guidelines) specify two core types of losses:No-load Loss (P0)Definition: Losses measured when the primary winding is energized at rated voltage and the secondary winding is open-circuited (dominated by core losses).Test Conditions Measured at rated frequency and voltage (typically sinusoidal power frequency). Corrected to reference temperature (75°C for oil-immersed transformers, 115°

Life Cycle Cost Analysis of Power Transformers Based on IEC StandardsCore Framework Under IEC StandardsAccording to IEC 60300-3-3, the life cycle cost (LCC) of power transformers includes five stages: Initial Investment Costs: Procurement, installation, and commissioning (e.g., 20% of total LCC for a 220kV transformer). Operational Costs: Energy losses (60%-80% of LCC), maintenance, and inspections (e.g., annual savings of 2,600 kWh for a 1250kVA dry-type transformer). Decommissioning Costs: Res

Relationship Between Rated Capacity and DimensionsDefinition of Rated Capacity: According to IEC 60076-1, the rated capacity is the maximum apparent power (kVA or MVA) allowed under continuous load, ensuring compliance with steady-state temperature rise and voltage regulation requirements.Key Parameters Affecting Dimensions: No-load loss （P0）and load loss (Pk)directly influence the physical size of the core and windings. Short-circuit impedance (%) correlates with winding turns and insulation di

Insulating medium Oil - filled type: It uses insulating oil (such as mineral oil, silicone oil) as the main insulating medium. The iron core and coils are immersed in the oil. The insulating property of the oil is utilized to isolate conductors with different potentials, preventing short - circuits and discharges. Dry - type: It adopts air or solid insulating materials, such as epoxy resin, as the insulating medium. Materials like epoxy resin are wrapped around the coils, serving as insulation a

Controlled Switching Devices in the Medium Voltage RangeOver three decades ago, Controlled Switching Devices (CSDs) were first introduced to mitigate switching transients caused by high voltage circuit breakers connected to shunt reactors and capacitor banks. Subsequent research expanded their application to transmission lines and power transformers. Initially, these devices optimized switching moments on a per-phase basis using independently pole-operated circuit breakers (IPO).Recently, the su

Differences in the Impact of AC and DC on Conductors, Capacitors, and TransformersThe effects of alternating current (AC) and direct current (DC) on conductors, capacitors, and transformers differ significantly, primarily in the following aspects:Impact on Conductors Skin Effect: In AC circuits, due to electromagnetic induction, the current tends to flow near the surface of the conductor, a phenomenon known as the skin effect. This results in a reduced effective cross-sectional area of the condu