ZANDZ Technical Center offers an example of lightning protection for one of the important ground-based components of the GLONASS satellite navigation system.
In its work, the GLONASS navigation system relies not only on the orbital constellation of 24 satellites. An important role in the accuracy of navigation is played by the GLONASS ground infrastructure, including the laser ranging distance measurement. The coordinate-time support and calibration of the navigation system depends on them. Highly sensitive devices of the stations must be protected from lightning. ZANDZ engineers got a task to calculate lightning protection in the framework of the project “Creation of a laser distance measurement for artificial Earth satellites with submillimeter measurement error, as means of fundamental support for the GLONASS system”.
We proposed a comprehensive solution for the station's lightning protection: external protection with lightning rods and internal protection against impulse overvoltages using SPDs. Read below for details.
Task
To calculate lightning protection of the laser station of the complex of means of fundamental support (LS CMFS). The building under protection is an ordinary structure in terms of lightning protection in accordance with the IS and is in Category 3 according to the AD.
Solution
Calculations of lightning protection and grounding of a historical object are made in accordance with the following documents:
- Electrical Installation Code" EIC 7th ed (hereinafter - EIC).
- Instructions for organization of lightning protection of buildings, structures and industrial communications" IS 153-34.21.122-2003 (hereinafter IS).
- Instructions for lightning protection of buildings and structures" AD 34.21.122-87 (hereinafter - AD).
Protection of buildings from lightning strikes is carried out with the help of lightning rods. A lightning rod is a device rising above a facility that diverts lightning current into the ground without entering the facility. It consists of a lightning rod which directly takes the lightning discharge upon itself, a down conductor and a ground electrode.
GLONASS lightning protection system description
The set of measures to provide the required lightning protection is offered by the following solutions:
- Installation of the 1st rod lightning rod with a height of 8 m on the gable. It is taken into account that 1 m of the lightning rod height is used for the fixation.
- Lightning rods are interconnected to arrange two down conductors, using copper-bonded wire D=8 mm from each lightning rod. Down conductors are connected to the artificial ground electrode. Fastening of down conductors with an installation step of 0.6-1 m is performed:
- on the roof – with GL-11747A clamps;
- to drainpipes – with GL-11514 clamps.
- GL-11551A clamps are used to connect and branch the down conductors.
The set of measures to ensure provision of the necessary requirements to the grounding device is offered by the following solutions:
- Installation of the grounding device consisting of a horizontal electrode (copper bonded tape 4x30 mm), distance to the walls of the building 1 m, depth 0.5 meters and 3 vertical electrodes (copper coated steel pins with a diameter of 14 mm) 3 m long.
- Interconnection of horizontal electrodes is carried out by using clamp ZZ-005-064.
- The down conductor is connected to the copper-bonded tape protruding from the ground with the help of GL-11562A clamp.
The layout of elements in the lightning protection system and the grounding device is shown in Figure 1.
Protection zone corresponding to zone B of the AD, is shown in Figure 2.
Figure 1 - A sketch with the location of the elements of lightning protection and grounding device
Стержневой молниеприемник – rod lightning rod
Горизонтальный заземлитель – horizontal ground electrode
Вертикальный заземлитель длиной 3 м – vertical ground electrode 3 m long
Зажим для подклбючения проводника – clamp for conductor connection
Зажим контрольный (проволока + полоса) – control clamp (wire + tape)
Зажим на водосточную трубу для токоотвода – clamp on a water pipe for a down conductor
Зажим на крышу, покрытую металлическим профилем для токоотвода – clamp on the roof covered with metal profile for a down conductor
Токоотвод- down conductor
Figure 2 - Protection Zone
Accessories for the GLONASS laser distance measurement system for external lightning protection
Table 1 - Materials requirement list
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Internal lightning protection (SPD)
To protect equipment and electric communications inside a building, we recommend to provide a set of measures that rule out the impact of hazardous overvoltages.
Protection in the main distribution panel
A surge protection device (SPD) of class I+II+III PP BCВ TT 25/100 is installed in the distribution panel; the device was chosen due to the three-phase input into the house and TT or TN-S power system.
The connection is made in series (V-connection). We recommend using standard F1 fuses (see the diagram) without skewing at the nominal rating of up to 125A.
If a local switch (or protective fuses instead of it) designed to withstand mains power is installed and its nominal rating is less than 125 A, then additional F1 fuses are not required.
Figure 3. Diagram of SPD of class 1+2+3 connection
Table 2 - List of demand in materials for internal lightning protection
|
№ |
Image |
Product item |
Name |
Quantity, pcs |
|
1.
|
 |
LE-373-930 |
1 |
Lightning protection of the facility is considered incomplete without the stated measures, because only the use of protective devices makes it possible to reduce overvoltages in the mains to a level safe for equipment.
The calculation example of lightning protection includes equipment that protects both against primary and secondary effects of lightning. Thus, the complex of measures provides complete protection.
Do you have questions about lightning protection of objects with sensitive equipment? Please contact our ZANDZ Technical center!
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