Grounding devices for electrical installations with voltages above 1 kV in networks with isolated neutral

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 1 General Rules

Grounding and protective measures for electrical safety. Grounding devices for electrical installations with voltages above 1 kV in networks with isolated neutral

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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1.7.96. In electrical installations with a voltage above 1 kV network with an isolated neutral, the resistance of the grounding device during the passage of the calculated ground fault current at any time of the year, taking into account the resistance of natural grounding conductors, should be

R ≤ 250/I

but not more than 10 Ohm, where I is the rated earth fault current, A.

The following is taken as the rated current:

1) in networks without compensation of capacitive currents - earth fault current;

2) in networks with compensation of capacitive currents:

for grounding devices to which compensating devices are connected - a current equal to 125% of the rated current of the most powerful of these devices;
for grounding devices to which compensating devices are not connected, - the ground fault current passing in a given network when the most powerful of the compensating devices is turned off.

The calculated ground fault current must be determined for that of the network circuits possible in operation for which this current has the greatest value.

1.7.97. When using a grounding device simultaneously for electrical installations with voltages up to 1 kV with an insulated neutral, the conditions of 1.7.104 must be met.

When using a grounding device simultaneously for electrical installations with a voltage of up to 1 kV with a solidly grounded neutral, the resistance of the grounding device must be no more than specified in 1.7.101 or the shells and armor of at least two cables for voltages up to or above 1 kV or both voltages must be connected to the grounding device , with a total length of these cables of at least 1 km.

1.7.98. For substations with a voltage of 6-10/0,4 kV, one common grounding device must be made, to which the following must be connected:

1) transformer neutral on the side with voltage up to 1 kV;

2) transformer housing;

3) metal sheaths and armor of cables with voltage up to 1 kV and above;

4) open conductive parts of electrical installations with voltage up to 1 kV and above;

5) third-party conductive parts.

Around the area occupied by the substation, at a depth of at least 0,5 m and at a distance of no more than 1 m from the edge of the foundation of the substation building or from the edge of the foundations of openly installed equipment, a closed horizontal grounding conductor (circuit) must be laid, connected to the grounding device.

1.7.99. A grounding device for a network with a voltage above 1 kV with an isolated neutral, combined with a grounding device for a network with a voltage above 1 kV with an effectively grounded neutral into one common grounding device, must also meet the requirements of 1.7.89 - 1.7.90.

See other articles Section Rules for the installation of electrical installations (PUE).

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