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

Transformer Testing Procedures and Requirements1. Non-Porcelain Bushing Tests1.1 Insulation ResistanceSuspend the bushing vertically using a crane or support frame. Measure the insulation resistance between the terminal and the tap/french using a 2500V megohmmeter. The measured values should not significantly deviate from factory values under similar environmental conditions. For capacitive-type bushings rated 66kV and above with tap bushings, measure the insulation resistance between the "small

The grounding disconnect switch of a pad-mounted transformer is a switching device used to isolate the pad-mounted transformer from the grounding cable. It is an essential component of pad-mounted transformer equipment and plays a critical role in protecting the safety of the transformer equipment. The grounding disconnect switch of a pad-mounted transformer serves important functions in grounding down leads, grounding switching, auxiliary grounding, and lightning protection.Its functions includ

In China's power system, the 6 kV, 10 kV, and 35 kV grids generally adopt a neutral-point ungrounded operation mode. The distribution voltage side of main transformers in the grid is usually connected in delta configuration, which provides no neutral point for connecting grounding resistors. When a single-phase ground fault occurs in a neutral-point ungrounded system, the line-to-line voltage triangle remains symmetrical, causing minimal disruption to user operations. Moreover, when the capaciti

In China's power system, the 6 kV, 10 kV, and 35 kV grids generally adopt a neutral-point ungrounded operation mode. The distribution voltage side of the main transformer in the grid is usually connected in delta configuration, which provides no neutral point for connecting a grounding resistor.When a single-phase ground fault occurs in a neutral-point ungrounded system, the line-to-line voltage triangle remains symmetrical, causing minimal impact on user operations. Moreover, when the capacitiv

On-load tap changing is a voltage regulation method that allows a transformer to adjust its output voltage by switching tap positions while operating under load. Power electronic switching components offer advantages such as frequent on/off capability, spark-free operation, and long service life, making them suitable for use as on-load tap changers in distribution transformers. This article first introduces the operational regulations for on-load tap-changing transformers, then explains their vo

Dry-type transformers refer to power transformers in which the core and windings are not immersed in oil. Instead, the coils and core are cast together (typically with epoxy resin) and cooled by either natural air convection or forced-air cooling. As a relatively newer type of power distribution equipment, dry-type transformers have been widely used in power transmission and distribution systems in factory workshops, high-rise buildings, commercial centers, airports, ports, subways, and offshore

1.IntroductionIn a double-busbar system, line energizing/de-energizing and bus transfer are fundamental switching operations. Under the double-busbar configuration, line protection voltage is derived from busbar potential transformers (PTs). The PTs are connected to the busbar via primary disconnect switches, with their secondary windings routed to the PT secondary terminal box. Each PT has three secondary windings: one for protection and measurement, one for metering, and one open-delta winding

Common Faults of High-Voltage Circuit Breakers and Mechanism Pressure LossCommon faults of high-voltage circuit breakers themselves include: failure to close, failure to trip, false closing, false tripping, three-phase asynchronism (contacts not closing or opening simultaneously), damage to the operating mechanism or pressure drop, oil spraying or explosion due to insufficient interrupting capacity, and phase-selective circuit breakers failing to operate according to the commanded phase."Circuit

Basic Composition and Function of Circuit Breaker Failure ProtectionCircuit breaker failure protection refers to a protective scheme that operates when the relay protection of a faulty electrical device issues a trip command but the circuit breaker fails to operate. It uses the protection trip signal from the faulty equipment and the current measurement from the failed breaker to determine breaker failure. The protection can then isolate other relevant breakers within the same substation in a sh

Power Supply Procedure for Low-Voltage Electrical RoomsI. Pre-Power-On Preparations Clean the electrical room thoroughly; remove all debris from switchgear and transformers, and secure all covers. Inspect busbars and cable connections inside transformers and switchgear; ensure all screws are tightened. Live parts must maintain adequate safety clearance from cabinet enclosures and between phases. Test all safety equipment before energizing; use only calibrated measuring instruments. Prepare fire-