32.5
송전선: 과도 동작
절연 조정은 전기 장비의 절연 강도를 보호 장치 특성과 일치시켜 장비를 예상되는 과전압으로부터 보호하는 프로세스입니다. 이 선택은 엔지니어링 판단과 비용에 따라 이루어집니다. 장비는 일반적으로 단시간 고과도 과전압을 견딜 수 있지만 동일한 파형으로 반복 테스트하면 일관…
가정용 배선에서 볼 수 있는 전기 절연은 안전을 위해 매우 중요하며, 전도성 물질을 플라스틱이나 고무와 같은 절연 물질로 덮어 감전 및 단락을 방지합니다.
장비 절연의 강도는 시간에 따라 다르지만 수명이 짧은 경우 높은 과도 과전압을 견딜 수 있습니다.
절연 강도를 테스트하기 위해 표준 임펄스 전압파가 사용됩니다. 이 파형은 전압이 피크에 도달하고 피크 값의 절반으로 감소하는 데 걸리는 시간으로 정의됩니다.
이것의 피크 값은 기본 절연 수준(Basic Insulation Level, BIL)을 정의합니다. 표준 BIL을 충족하는 장비는 절연 불량 없이 표준 파형의 반복적인 적용을 견딜 수 있습니다.
가공 송전선로 절연과 같은 일부 장비는 단락 후 자체 복원되는 반면 내부 변압기 절연은 고장 시 수리 또는 교체가 필요합니다.
각 위상에서 접지까지 장비와 병렬로 연결된 보호 장치는 BIL을 초과하는 과전압으로부터 장비를 보호하여 보호 마진을 제공합니다.
보호 장치의 간단한 예는 지정된 과전압에서 스파크가 발생하도록 설계된 로드 갭입니다.
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Q1: What is the Basic Insulation Level and how is it determined?
The Basic Insulation Level, or BIL, is the peak value of a standard impulse voltage waveform used for testing equipment insulation strength. This waveform is defined by specific times for voltage to reach its peak and decay to half that peak value. Equipment meeting standard IEEE-defined BILs can withstand repeated applications of this waveform without insulation failure.
Q2: Why do protective devices need to limit voltage during overvoltages?
Protective devices limit voltage to protect equipment from overvoltages exceeding its insulation capacity. Connected in parallel between each phase and ground, these devices must provide high impedance during normal operation and low impedance during surges. This voltage limiting prevents insulation breakdown and equipment damage while maintaining system stability.
Q3: What is the protection margin in insulation coordination?
The protection margin is the difference between the equipment's breakdown voltage and the protective device's ceiling voltage. This margin ensures the protective device operates before equipment insulation fails. A proper protection margin is essential for reliable equipment operation and is determined through engineering judgment and cost considerations during insulation coordination design.
Q4: How do rod gaps function as protective devices?
Rod gaps are simple protective devices designed to spark over at specified overvoltages, creating a conduction path that diverts excess voltage to ground. They operate by providing high impedance during normal conditions and transitioning to low impedance when overvoltage thresholds are exceeded, protecting connected equipment from voltage surges.
Q5: What is the difference between self-restoring and non-restoring insulation?
Overhead transmission line insulation is self-restoring after a short circuit, automatically recovering its insulating properties. In contrast, internal transformer insulation requires repair or replacement upon failure. This distinction affects maintenance strategies and equipment design choices in power system protection planning.
Q6: How does insulation coordination protect power systems from overvoltage damage?
Insulation coordination matches equipment insulation strength with protective device characteristics to prevent overvoltage damage. By ensuring protective devices limit voltage below equipment withstand capacity, coordination maintains system stability and equipment longevity. This process involves analyzing lossy lines and overvoltages to select appropriate protective measures.
Q7: What characteristics must surge arresters have to be effective?
Effective surge arresters must provide high impedance during normal operation to minimize losses, low impedance during surges to limit voltage, and effectively dissipate or store surge energy. After the surge passes, they must return to open-circuit conditions. Common types include air-gap designs with resistors and gapless surge arresters.