PUE 7, Section 1.7 Earthing and safety measures — clause by clause

Clause-by-clause review of PUE chapter 1.7 (7th ed.): TN-C/TN-S/TN-C-S/TT/IT earthing, direct and indirect contact protection, 30 mA RCDs, protective conductors, bonding. Clause numbers included.

Document

Document	PUE 7, Section 1.7 Earthing and safety measures
Edition	2002 (ПУЭ-7, гл. 1.7)
Status	Current
Issued by	Ministry of Energy of Russia (2002–2003)
Applies to	All installations up to and above 1 kV: earthing and electrical safety measures

Document structure

№	Chapter / section
1.7.1–1.7.15	Scope, terms, earthing systems
1.7.16–1.7.31	Protection against direct contact
1.7.32–1.7.49	Protection against indirect contact
1.7.50–1.7.67	Earthing arrangements
1.7.68–1.7.87	Protective conductors, RCDs
1.7.88–1.7.105	Equipotential bonding
1.7.106–1.7.118	Inspection and maintenance
1.7.119–1.7.176	Requirements for residential, public buildings and outdoor installations

Earthing systems (1.7.3–1.7.15)

1.7.3 TN-C: combined neutral and protective conductor (PEN) throughout.

1.7.4 TN-S: separate N and PE throughout.

1.7.5 TN-C-S: PEN combined up to the intake, then split into PE and N — standard for new Russian buildings.

1.7.6 TT: neutral earthed, exposed parts earthed separately.

1.7.7 IT: neutral isolated (or earthed via high impedance), exposed parts earthed separately.

Direct contact protection (1.7.16–1.7.31)

1.7.31 Additional protection: RCD ≤ 30 mA.

Indirect contact protection (1.7.32–1.7.49)

1.7.36 Disconnection times (table 1.7.1): 0.4 s at 380/220 V, 0.2 s at 660/380 V.

1.7.45 TT: RCD-based protection, RA×Ia ≤ 50 V.

Earthing arrangements (1.7.50–1.7.67)

1.7.51 Earth resistance ≤ 4 Ω in TN systems (10 Ω below 100 kVA).

1.7.63 Underground earthing conductors: copper ≥ 10 mm², aluminium 16 mm², steel 75 mm².

Protective conductors and RCDs (1.7.68–1.7.87)

1.7.76/79 Exposed parts to PE; PE separate from N after the PEN split.

1.7.87 Residential group circuits: RCD ≤ 30 mA.

Equipotential bonding (1.7.88–1.7.105)

1.7.91 Main bonding in every building: pipes, steelwork, PE, lightning.

1.7.92 Supplementary bonding in bathrooms, saunas, wet rooms.

1.7.99–1.7.101 Bonding conductor sizes: main — ≥ half of the largest PE (6–25 mm² copper); supplementary per table 1.7.5.

Residential and public buildings (1.7.119–1.7.135)

1.7.120 No water/gas pipes, cable sheaths or rebar as PE.

1.7.123 Socket earthing contact must connect to PE.

1.7.132 Bathroom sockets: 30 mA RCD line or isolating transformer.

1.7.135 Combining N and PE in final circuits is prohibited.

Practical takeaways

Section 1.7 is the most cited part of PUE: TN-C-S choice, 30 mA RCDs, main and supplementary bonding, the N–PE prohibition (1.7.135). Harmonized with IEC 60364-4-41 and 5-54.

Data is for reference. Final design decisions must follow current regulations and a qualified engineer.
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