GB7495-1987

The protecting distance betweenoverhead power line and receiving station of AM broadcasting

架空电力线路与调幅广播收音台的防护间距

GB 7495-1987 — действующий обязательный национальный стандарт Китая: The protecting distance betweenoverhead power line and receiving station of AM broadcasting. Отрасль: Электроника. Тема: Безопасность продукции. Дата вступления в силу: 1 нояб. 1987 г..

Применимость зависит от продукции, схемы сертификации, уведомлений компетентных органов и переходных правил. Закажите перевод или проверьте источник, прежде чем использовать эту запись в решениях по соответствию.

Обзор требований

Этот обзор пока доступен только на английском языке.

Область применения

This standard applies to the protection of AM broadcasting receiving stations from radio interference and other impacts caused by overhead power lines operating within the frequency range of 526.5kHz to 26.1MHz. It is essential for engineers involved in the planning and construction of power transmission infrastructure and broadcasting facilities. It does not apply to underground power cables or non-AM broadcasting frequencies. The standard categorizes receiving stations into three levels based on their administrative hierarchy and operational scope, as well as monitoring stations into three corresponding tiers.

Технические требования

The core of GB 7495-87 defines the protecting distance (minimum separation distance) required between overhead power lines and AM broadcasting receiving stations. It specifies distinct distance requirements based on two main factors: the voltage level of the overhead power line (ranging from 35kV to 500kV) and the classification of the receiving station (Level 1, 2, or 3). Additionally, the standard outlines specific separation requirements for monitoring stations (which monitor broadcast quality and technical parameters), categorized into three levels. For power lines below 35kV, the standard references the 35kV limits but allows for negotiated solutions if strict compliance is difficult. If meeting the standard distance requirements is physically or economically unfeasible, alternative technical measures must be evaluated. These alternative measures include modifying the power line route, improving antenna designs, or changing the program transmission method (e.g., using FM or microwave). The standard also references calculation methods based on CISPR Publication 18-1 for determining acceptable interference levels when deviations from the standard distances are necessary.

Методы испытаний

The standard provides recommended calculation formulas rather than physical testing procedures. It includes a formula to calculate the radio interference level at a distance of 20 meters from the power line, based on the maximum conductor surface potential gradient and conductor diameter. It also offers a frequency correction formula to adjust interference levels for different frequencies. For determining the protecting distance when standard limits cannot be met, the standard details two calculation methods: the direct calculation method (based on minimum usable signal field strength and signal-to-noise ratio) and the control background calculation method (based on pre-construction environmental background field strength and allowable background field strength increments).

Частые вопросы

What products and facilities are regulated under GB 7495-87?

GB 7495-87 regulates the spatial relationship between overhead power lines (35kV and above, with references for lower voltages) and AM broadcasting receiving stations and monitoring stations. It mandates specific minimum separation distances to prevent radio interference.

Can the protecting distance specified in GB 7495-87 be reduced if site conditions are restricted?

Yes. If meeting the standard distance is genuinely difficult, it can be reduced through calculation, measurement, or other technical measures. The standard provides specific formulas (direct calculation and control background calculation) and suggests alternative mitigation strategies like rerouting the power line or relocating the receiving antenna.

How does GB 7495-87 classify AM broadcasting receiving stations?

The standard classifies receiving stations into three levels based on their administrative level and operational purpose. Level 1 stations are typically provincial or central relay stations, Level 2 are regional or municipal stations, and Level 3 are county-level or local cable network stations. The required protecting distance increases with the station's level.

The summary above provides a high-level overview of GB 7495-87. To ensure complete compliance for your power transmission or broadcasting projects in the Chinese market, a precise and professional translation of the full technical specifications is essential. Purchase our high-quality English translation of GB 7495-87 today to access all detailed distance tables, calculation formulas, and mitigation procedures.

Подсказки по применимости

Тип: Безопасность
CCS: L06
ICS: 13.260
Компетентное ведомство: National Radio and Television Administration
Технический комитет: National Technical Committee on Radio, Television and Online Audiovisual of Standardization Administration of China