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In 10 kV and 35 kV ungrounded systems, single - phase grounding faults cause minimal current, so protection rarely trips. Per regulations, operation is limited to 2 hours; prolonged undetected faults may worsen, even damaging switches. While the State Grid promotes small - current grounding line selection devices in 110 kV and 220 kV substations, their accuracy remains low, requiring monitoring/operation staff to analyze remote measurements. For ungrounded systems with three - phase 4PT voltage

Hey everyone! I’m Felix, a 10-year veteran in the power system industry. Today, we’re going to dive into an important topic — what are the common failures of Air Insulated Switchgear (AIS) voltage transformers? How do you identify these issues, and how can they be resolved? Let’s get started!1. Insulation DamageThe Problem You Might Encounter：One of the most frequent issues is insulation damage. This typically happens due to aging insulation materials, ove

Current transformers are numerous in substations and are key equipment to ensure the normal operation of the system. If a current transformer fails, it will cause the circuit breaker to trip and may even evolve into a power outage event, which will have an adverse impact on the safe and stable operation of the power grid. Taking an event of the main transformer differential protection operation caused by the failure of the current transformer on the low-voltage side of the main transformer in a

Fault Prevention and Handling of Current Transformers1 Handling of Oil Leakage in Current TransformersOil - immersed current transformers are most prone to oil leakage. Common oil - leakage parts mainly include the secondary outlet box, the upper and lower sealing surfaces of the porcelain sleeve, the oil tank, the base, the oil conservator, and the metal expander.Methods for handling oil leakage: For oil leakage at the secondary outlet box, if the small porcelain sleeve or terminal board is cra

1 Basic Operation RequirementsThe technical parameters of current transformers shall meet the actual operation needs. Carefully check the nameplate of the current transformer to confirm whether its technical parameters meet the requirements. Current transformers for metering must be selected with rated loads and accuracy classes that meet the requirements in accordance with relevant metering standards. The actual load connected to the secondary winding of the current transformer shall be within

Hey everyone, I'm Felix, and I've been working in the power system field for 10 years. From following senior engineers on-site to leading teams handling various substation equipment failures, I’ve worked with many types of current transformers (CTs), especially those used in air insulated switchgear (AIS).Although this type of equipment is relatively simple in structure and easy to maintain, it still experiences frequent issues during actual operation. Today, I’ll share my ha

1. IntroductionFrequent occurrences of PT burnout and primary - side fuse melting in combined transformers lead to inaccurate energy meter measurement and seriously threaten the safe operation of the power grid. This paper focuses on the repeated PT damage and fuse melting issues of a 35 kV combined transformer, investigates the fault causes, proposes solutions, and recovers the incorrect electricity quantity through correction coefficients. This effectively reduces grid losses and mitigates ser

Voltage transformers (PTs) consist of iron cores and winding coils, working similarly to transformers but with small capacity. They convert high voltage to low voltage for protection, measurement and metering devices, widely used in plants/stations. Classified by insulation: dry - type (≤6 kV), cast - type (indoor 3 - 35 kV), oil - immersed (outdoor ≥35 kV), and SF₆ gas - filled (for combined appliances).During substation operation, accidents from PT electromagnetic resonance or in

Hey everyone, I’m Oliver, and I’ve been working in current transformer (CT) testing for 8 years.From running around with test equipment on site to now leading full inspection teams, I’ve seen how thousands of outdoor CTs go through a whole series of tests — like going through a military training camp — before they can finally be put into service.A few days ago, a friend asked me: “Oliver, our factory just produced a new batch of outdoor

1. Research Reasons and Background1.1 Importance of Current TransformersCurrent transformers play the role of current transformation and electrical isolation. They convert the large current of the primary system into a proportional small secondary current, which is supplied to measuring instruments, relay protection, and automatic devices. In the power system, the role of current transformers is irreplaceable and directly plays a key role in the safe and stable operation of the power grid.1.2 Ha