Webinar "Grounding and lightning protection for electrical substations", page 2

The fourth webinar of the "Simply about installing grounding and lightning protection" series

Webinar text. Page 2

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Grounding device outside the substation

— In high-ohmic soils, the basic structure grid may not be sufficient. In order to obtain the resistance of 0.5 Ohm to reduce the resistance to the grounding device, it may be extended within the substation territory as well as beyond the territory. The horizontal grounding devices must be laid beyond the substation fencing at the depth of up to 1 meter. Significant decrease may be obtained by installing the electrolytic grounding sets. 

Internal grounding circuit

— The grounding line is installed inside the shared utility meters and protective distribution device building at the height of 60 cm, or, in another words, it is called the internal circuit. Then, to this internal circuit, we attach the metal structure with cabinets, and equipment racks. 
 

Substation lightning protection

– The substation equipment must be protected against the direct lightning strikes. Usually the lightning protection for all substations is required, but there are some exceptions. 

Молниезащита подстанции	Substation lightning protection
Для защиты от прямых ударов молнии используются:	The following is used for protection against direct lightning strikes:
Молниеприемники на порталах	Lightning arresters on the portals
Молниеприемники совмещенные с прожекторными мачтами.	Lightning arresters combined with the searchlight masts.
Отдельно стоящие молниеприемники для необходимой надежности защиты	Standalone lightning arresters for necessary protection reliability
Также заземляются стойки конструкций подстанции с заведенными тросами воздушных линий	Also the substation structure stands with overhead line wires shall be grounded
Подробные требования приведены СТО 56947007- 29.130.15.114-2012 ПАО "ФСК ЕЭС"	See detailed requirements in STO 56947007- 29.130.15.114-2012 FGC UES, PJSC
Заземление и молниезащита на ZANDZ.com	Grounding and lightning protection on ZANDZ.com

Lightning rods as the protection against lightnings

– The protection against the direct lightning strikes is performed using the lightning rods installed at the structures, portals, as well as on the lighting poles. The installation of standalone lightning rods may also be required for protection. Moreover, they may be required to take the lightning rod from the portals, e.g., when you need to reduce the effect of the pulse current of the lightning in a specific point of the cable directly in the equipment.

Horizontal grounding devices arrangement

– If the lightning rods are attached to the base structure, it is required that the distance to power transformers, reactors, and switchgears would be no less than 15 meters along the grounding trunks. 

 

Молниезащита подстанции	Substation lightning protection
Молниеприемник может присоединяться к ЗУ открытого распределительного устройства, при этом:	The lightning arrester can be connected to the ground terminal of the switchyard, provided that:
От каждого отдельно стоящего молниеприемника выполняется прокладка горизонтальных заземлителей для растекания тока не менее чем в 2 направлениях или в 3-х направлениях если расстояние от молниеотвода до трансформатора менее 15м	From each standalone lightning rod, the installation of the horizontal grounding devices is performed for the current to flow in not less than two directions, or three directions, if the distance from the lightning rod to the transformer is less than 15 meters.
На каждом направлении устанавливается по вертикальному электроду длиной 5 метров	At each direction, 5-meter-long vertical electrode is installed.
Заземление и молниезащита на ZANDZ.com	Grounding and lightning protection on ZANDZ.com

Connecting the lightning rod with the grounding device

– If the lightning rods are attached to the substation grounding grid, we need to meet the following requirements. From each standalone lightning rod, the installation of the horizontal grounding devices is performed for the current to flow in not less than two directions, or three directions, if the distance from the lightning rod to the transformer is less than 15 meters. At each direction, the vertical electrode is installed at the depth of 5 meters. We can see that in this case.

Calculation of the substation lightning protection

– The substation lightning protection is calculated in accordance with the regulatory documents specified in the slide. The reliability of protection against the direct lightning strikes is taken as factors of 0.95–0.99, and this means reliability class 2. The substations may be standard, with the protection reliability factor of 0.95, or may be referred to as the special facilities, with the reliability factor of 0.99. Depending on these accessories and the importance for the energy system, the calculations are usually performed in the software suites. The zone of protection with the required reliability is plotted in the drawing at the protected equipment height. The calculations of the lightning protection are also performed by the ZANDZ Center in the software developed by the Energy Institute named after G. M. Krzhizhanovsky. 

Useful materials for designers:

• Webinars with participation of lead experts of the industry
• All for calculation of the earthing and lightning protection
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