The highest permissible values of the resistance of the grounding conductors of the supports of overhead power lines

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Annex 3.1. The highest permissible values of the resistance of the grounding conductors of the supports of overhead power lines. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Rules for the technical operation of consumer electrical installations (PTE)

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Table 35

Object characteristic	Soil resistivity, r, Ohm×m	Resistance, Ohm
Lines for voltages above 1000 V
Poles with a lightning protection cable or other lightning protection devices, metal and reinforced concrete poles of 35 kV overhead lines and the same poles of 3 - 20 kV overhead lines in a populated area, equipment earthing switches on poles of 110 kV and above	to 100	10*
	more than 100 to 500	15*
	more than 500 to 1000	20*
	more than 1000 to 5000	30*
	more 5000	0,006r*
Electrical equipment installed on supports VL 3 - 35kV	-	250/Iр**, but not more than 10
Metal and reinforced concrete supports of 3 - 20 kV overhead lines in an uninhabited area	to 100 more 100	30 0,3r
Tubular arresters on line approaches to substations with rotating machines, valve arresters on cable inserts on approaches to substations with rotating machines	-	5
Valve arresters and non-linear surge suppressors on the approaches of lines to substations with rotating machines	-	3
Supports with a cable at the approaches of lines to substations with rotating machines	-	10
Lines for voltage up to 1000 V***
VL support with lightning protection devices	-	30
Supports with repeated grounding of the neutral wire at the voltage of the power source:
660/380 V	-	15
380/220 V		30
220/127 V		60

* For supports with a height of more than 40 m in sections of overhead lines protected by a cable, the resistance of the ground electrodes must be 2 times less than those indicated in the table.
** Ir - rated earth fault current, which is taken as:
in networks without compensation of capacitive earth fault current - earth fault current;
in networks with compensation of capacitive earth fault current:
- for electrical installations to which compensating devices are connected, a current equal to 125% of the rated current of the most powerful of these devices;
- for electrical installations to which compensating devices are not connected, - the earth fault current passing in this network when the most powerful of the compensating devices is turned off.
*** If the specific equivalent soil resistance is more than 100 Ohm×m, it is allowed to increase the given values by 0,01r times, but not more than tenfold.

See other articles Section Rules for the technical operation of consumer electrical installations (PTE).

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