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Equipment bonding jumpers: are they always necessary?

Massimo Mitolo,  Senior Member, IEEE

Equipment bonding jumpers: are they always necessary?

Equipment Bonding Jumpers are equivalent to:

Protective Bonding Conductors (PE) as per IEC 60364:

Maintain continuity of the equipment grounding path.
Provide Protective Equipotential Bonding.

Exposed-conductive-part (ECP)

Conductive part

forming part of electrical equipment

which can be touched (even if out of reach)

which is not live

which may become live when basic insulation fails.

ECP</span><span style=" font-family: 'Verdana', 'Arial';
font-size: 36pt; font-weight: bold; font-style: normal; text-decoration: none;
color: #FF3300;">s shall be bonded to ground

so that fault current is allowed to flow to ground,
permitting the protective device to promptly disconnect the supply.

Grounding is the 2<sup>nd level of protection, the
basic
insulation
being
the
1st.

Exposed-conductive-part (ECP)

Exposed-conductive-part (ECP)

Piece of equipment with double (or reinforced) insulation (Class II equipment), is not considered an ECP and

shall not be connected to a PE.

(!! NEC art. 250-110 Exception n. 3 !!)

Additional insulation is the 2<sup>nd level of protection

Symbol:

Exposed-conductive-part (ECP)

A conductive part which can be energized just because
in contact with an ECP, is not an ECP.

(it is not required to be grounded, then!)

Extraneous-conductive-part (EXCP)

Conductive part

not forming part of the electrical system (e.g. piece
of metalwork)

liable to introduce a zero potential

or an arbitrary potential into the premises.

Extraneous-conductive-part (EXCP)

EXCPs shall be bonded to ground

Equipotential connections between ECP</span><span style=" font-family: 'Verdana', 'Arial';
font-size: 28pt; font-weight: normal; font-style: normal; text-decoration: none;
color: #FFFFFF;">s and EXCP</span><span style=" font-family: 'Verdana', 'Arial';
font-size: 28pt; font-weight: normal; font-style: normal; text-decoration: none;
color: #FFFFFF;">s will significantly reduce the magnitude of their
potential difference under fault conditions.

(Necessary but not sufficient condition!)

Extraneous-conductive-part (EXCP)

Extraneous-conductive-part (EXCP)

Its an EXCP if less than:

1000 Ohms

(200 Ohms)

(based on the definition of permissible body current
and body resistance of a standard person

As per IEC 60479-1)

Where do you find PEs?

6 possible cases:

PE in equipments