This standard applies to the protection of radio interference and other effects of overhead power lines on AM broadcast radio stations in the frequency range of 526.5kHz ~ 26.1MHz. GB 7495-1987 Protective distance between overhead power lines and AM broadcast radio stations GB7495-1987 Standard download and decompression password: www.bzxz.net

National Standard of the People's Republic of China
Overhead power line and recelving station of AM broadcasting
The protecting distance between overhead power line and recelving station of AM broadcastingUDC 621. 815.17||tt| |:621.396.669
GB 7495 --87
This standard is applicable to the protection of radio interference and other effects of overhead power lines on AM broadcast radio stations in the frequency range of 526.5kHz ~ 26.1MHz.
1 Explanation of terms
1.1 Protection distance
In order to protect the AM broadcast radio station from the influence of overhead power lines and ensure normal operation and radio quality, the specified distance between the two distance.
The protective distance refers to the distance from the conductor on the side of the overhead power line close to the AM radio station to the antenna of the AM radio station. Overhead power lines of 110kV and below should also include the distance to the entrance of the antenna feeder in the computer room. 1.2 AM broadcast radio station
receives AM signals and transmits the signals to local retransmission transmitting stations or dedicated AM broadcast radio stations used as signal sources by cable broadcast networks.
AM radio stations are divided into three levels according to their administrative affiliation and business nature. 1.2.1 The first-level AM radio station
is an AM radio station set up by the Ministry of Radio, Film and Television outside Beijing to receive programs of the Central People's Broadcasting Station or China International Radio (RadioBeijing) and is an AM radio station for the province. The relay transmitting station directly under the jurisdiction of autonomous regions, municipalities directly under the Central Government receives and transmits the AM broadcast radio station programmed by the Central People's Broadcasting Station.
Level 1.2.2 AM radio station
is an AM radio station directly under the jurisdiction of provinces, autonomous regions, regions, and municipalities directly under the jurisdiction of the province to receive and transmit programs of provincial and autonomous region People's Broadcasting Stations.
is an AM radio station directly under the jurisdiction of regions, provinces and municipalities to receive and transmit programs of the Central People's Broadcasting Station. 1.2.8 Three-level AM radio station
is an AM radio station that receives and transmits programs of the Central People's Broadcasting Station and provincial and autonomous region People's Broadcasting Stations at the city and county level, as well as the AM radio station of the county-level cable broadcast network. Radio station. 1.3 Monitoring station (station)
A dedicated AM radio station that monitors, monitors and analyzes the broadcast quality and various technical data and materials required for broadcasting.
Monitoring stations (stations) are divided into three levels according to different requirements of monitoring scope, monitoring items, monitoring accuracy, working hours and technical equipment.
1.3.1-level monitoring station
The Ministry of Radio and Television monitors and monitors domestic and foreign broadcast quality, technical parameters, broadcast spectrum load, determines the location of broadcast stations, and conducts research on radio wave propagation. Monitoring station. 1.3.2 Secondary monitoring station (station)
National Bureau of Standards approved 1987-03-24
26
1987-11-01 Implementation
GB 7495-87
A monitoring station (station) affiliated to the Ministry of Radio and Television, provinces, autonomous regions, and municipalities to monitor and monitor some broadcast quality, technical parameters, and determine the location of radio stations.
1.3.3 Level 3 monitoring station (station)
is a monitoring station (station) for provinces, autonomous regions, municipalities, regions, and provincial municipalities to monitor and monitor regional broadcast quality, technical parameters, etc. .
Unit, symbol
The operating rated voltage of overhead power lines is expressed in effective value (r·m·s) (kv). 2.1
2.2
Field strength value (dB), (1μV/m is 0dB). Distance value (m).
2.3
The protective distance between overhead power lines and AM broadcast radio stations. The protective distance between overhead power lines of different voltage levels and AM broadcast radio stations at all levels should comply with the requirements in Table 1. 3.1
Table 1
Protection distance (m)
Radio station level
Voltage level (kV)
35
Grade station| |tt||Level platform
Three-level platform
600
300
100
63~110
800||tt| |500
300
220~330
1000
700
400
3.2 Overhead power lines of different voltage levels and all levels The protective distance between monitoring stations (stations) should comply with the requirements in Table 2. Table 2
Protection distance
(m)
Monitoring station level
Level 1 monitoring station
Level 2 monitoring station
Level 3 Monitoring station
Voltage levelbZxz.net
(kv)
35
1000
600
100
Overhead below 3.335kV Distribution lines and first-level AM broadcast radio stations, 63~110
1400
600
300
-level monitoring stations,
according to Table 1 , 35kV regulations in Table 2, and the second and third level AM broadcast radio stations, 220~330
1600
800
400
500
1200
900
500
500
2000
1000
500
Protection of secondary monitoring station (station) Spacing
The protection spacing of the third-level monitoring station (station) refers to the 35kV regulations in Table 1 and Table 2. If there are any difficulties in meeting the above provisions, they can be resolved through negotiation. $.4 When it is really difficult to meet the protection spacing in Table 1, calculation (see Appendix B), measurement or other technical measures (see Appendix A) can be carried out, and the spacing smaller than Table 1 can be jointly determined based on the results. 27
GB 7495 --87
Appendix A
Radio interference protection measures between overhead power lines and AM broadcast radio stations
(reference)
When it is really difficult to meet the protective distance specified in Table 1 of this standard, the following protective measures can be taken. And based on the comparison of various factors such as technical and economic factors, a reasonable selection will be made through consultation. A.1 Protective measures available to the power department A.1.1 Control and reduce the radio interference level of overhead power lines through reasonable design. A.1.2 Adopt good construction methods to protect wires, fittings and insulators from damage, and at the same time strengthen operation and maintenance to control and reduce radio interference levels.
A.1.3 Change the path of overhead power lines. A.2 Protective measures available to the broadcasting department A.2.1 Improve the radio station antenna, or relocate the radio station antenna site within a local area. A.2,2 Change the AM radio station program transmission method, for example, use FM, micro quilt and other transmission methods. A.2.3 AM radio station relocation.
28
GB 7495 --87
Appendix B
Recommended calculation formulas for radio interference levels of overhead power lines and protective distances for AM broadcast radio stations (reference parts)
B.1 Overhead power line radio interference field strength calculation formula The radio interference level (dB) of 1MHz frequency at a distance of 20m from the ground projection of the side phase conductor of the overhead power line can be calculated by the following formula:
E26= 41 +4 (8mx-15.3) + 401g-d
2.72
where: gmax—overhead power line, maximum potential gradient on the conductor surface (kVrm/cm), (B1)||tt ||The diameter of a single wire, (cm). || tt | If you need to get the radio interference field strength at other frequencies, you can make corrections as follows. 1.5
AEf=201g-
0.5+fi.
where: f-
-actual calculated frequency, (
(MHz)|| tt||AEf
-interference field strength correction value at this frequency
B.2. Calculation method of electromagnetic radio interference protection distance (B2)
The corona interference protection distance of overhead power lines is calculated based on the calculation formula of the corona interference lateral propagation attenuation characteristics of overhead power lines recommended by CISPR. In actual engineering calculations , can be divided into two calculation methods according to different parameters: B.2.1 Direct calculation method
The direct calculation method directly calculates the protection based on the lowest available signal field strength and signal-to-noise ratio when the AM broadcast radio station is working normally. spacing. The calculation formula is as follows:
Where: Dp—
Sp-
rEia-Se+Rp
Dp= 10t
20
The calculated protective distance required by the AM broadcast radio station, (m) The lowest available signal field strength received by the AM broadcast radio station, (dB) - The signal noise ratio when the AM broadcast radio station is working normally, (dB), Rp||tt ||Ei.
Radio interference field strength at 20m away from the overhead power line side phase conductor, (dB), (h-2)'",
Ei. =Ez0+16.51g［ 1 +
20
h——The average height of overhead power line conductors to the ground, (m), 6
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