“equipment bonding jumpers: are they always necessary?” massimo mitolo, senior member, ieee

““Equipment bonding jumpers: are Equipment bonding jumpers: are they always necessary?”they always necessary?”

Massimo Mitolo, Massimo Mitolo, Senior Member, IEEESenior Member, IEEE

““Equipment bonding jumpers: are Equipment bonding jumpers: are they always necessary?”they always necessary?”

““Equipment Bonding Jumpers” areEquipment Bonding Jumpers” are equivalent to:equivalent to:

““Protective Bonding Conductors”Protective Bonding Conductors” ((PEPE) as per ) as per IEC 60364IEC 60364::

MaintainMaintain continuity continuity of the of the equipment grounding pathequipment grounding path..

ProvideProvide Protective Equipotential Protective Equipotential Bonding.Bonding.

Exposed-conductive-part (ECP)Exposed-conductive-part (ECP)

ConductiveConductive part part

forming partforming part of electrical of electrical equipmentequipment

which can which can bebe touchedtouched (even if out of (even if out of reach)reach)

which is which is not livenot live

which may which may become livebecome live when when basicbasic insulation fails.insulation fails.

ECPECPs shall be bonded to s shall be bonded to groundground

so that fault current is allowed to flow to so that fault current is allowed to flow to ground, permitting the protective device ground, permitting the protective device

to promptly disconnect the supply.to promptly disconnect the supply.

Grounding is the Grounding is the 22ndnd level of protection, level of protection, the the basic insulationbasic insulation beingbeing the 1the 1stst..

Exposed-conductive-part (ECP)Exposed-conductive-part (ECP)

Exposed-conductive-part (ECP)Exposed-conductive-part (ECP)

Piece of equipment with “Piece of equipment with “doubledouble” (or ” (or reinforcedreinforced) ) insulation (insulation (Class IIClass II equipment), is not considered an equipment), is not considered an

ECP ECP andand shall not be connected to a PEshall not be connected to a PE..

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

Additional insulation Additional insulation is the is the 22ndnd level level of protection of protection

Symbol:

Exposed-conductive-part (ECP)Exposed-conductive-part (ECP)

A conductive part which can be A conductive part which can be energized just because in contact energized just because in contact

with an with an ECP, ECP, is is notnot an an ECP.ECP.

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

Extraneous-conductive-part (EXCP)Extraneous-conductive-part (EXCP)

ConductiveConductive part part

notnot forming part of the electrical forming part of the electrical system (e.g. piece of metalwork)system (e.g. piece of metalwork)

liable to introduce a “liable to introduce a “zerozero” ” potentialpotential

or an or an arbitrary potentialarbitrary potential into the into the premises.premises.

Extraneous-conductive-part (EXCP)Extraneous-conductive-part (EXCP)

EXCPs shall be bonded to groundEXCPs shall be bonded to ground

Equipotential connections between Equipotential connections between ECPECPs s and and EXCPEXCPs will significantly reduce the s will significantly reduce the magnitude of their potential difference magnitude of their potential difference

under fault conditionsunder fault conditions..

(Necessary but not sufficient condition!)(Necessary but not sufficient condition!)

Extraneous-conductive-part (EXCP)Extraneous-conductive-part (EXCP)

Extraneous-conductive-part (EXCP)Extraneous-conductive-part (EXCP)

It’s an It’s an EXCP EXCP if less than:if less than:

10001000 Ohms Ohms((200200 Ohms) Ohms)

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

““standardstandard” person” person

As per IEC 60479-1)As per IEC 60479-1)

Where do you find PEs?Where do you find PEs?

6 possible cases:6 possible cases:

1.1. PE in equipmentsPE in equipments

2.2. PE among ECPsPE among ECPs

3.3. PE among electrostaticly chargedPE among electrostaticly charged objectsobjects

4.4. PE for Lightning Protection PurposesPE for Lightning Protection Purposes

5.5. PE among ECPs and metal partsPE among ECPs and metal parts

6.6. PE among ECPs and EXCPsPE among ECPs and EXCPs

1. PE in equipments1. PE in equipments

Clear path to ground = Low Clear path to ground = Low resistance PEresistance PE

1. PE in equipments1. PE in equipments

Zi Zph

ZRN

Vph

Vt

A

B

ECP

PE

PEphi

PEpht ZZZ

ZVV

2. PE among ECPs2. PE among ECPs

2. PE among ECPs2. PE among ECPs

3. PE among electrostaticly charged 3. PE among electrostaticly charged objectsobjects

• The metal object is The metal object is isolatedisolated from from ground (resistance to ground greater ground (resistance to ground greater than than 1 MOhm1 MOhm))

++• Any mechanism for Any mechanism for generatinggenerating

electric charges existselectric charges exists

++• An An explosive atmosphereexplosive atmosphere is is

presentpresent

4. PE for Lightning Protection Purposes4. PE for Lightning Protection Purposes

Overvoltages are induced in any closed loop with Overvoltages are induced in any closed loop with

possible electric discharge through the gapspossible electric discharge through the gaps

5. PE among ECPs and metal objects5. PE among ECPs and metal objects

5. PE among ECPs and metal parts5. PE among ECPs and metal parts

5. PE among ECPs and Metal 5. PE among ECPs and Metal objects?objects?

6. Among ECPs and EXCPs6. Among ECPs and EXCPs

Equipotential connectionsEquipotential connections between between ECPECPs and s and EXCPEXCPs will s will

significantly significantly reducereduce the the magnitude of their potential magnitude of their potential

difference under fault difference under fault conditions.conditions.

CONCLUSIONSCONCLUSIONSBasic investigationBasic investigation on the nature on the nature of conductive parts is necessary, in of conductive parts is necessary, in order to assess in which category order to assess in which category they fall (they fall (ECPECPs or s or EXCPEXCPs).s).

Only ECPs and EXCPs shall be Only ECPs and EXCPs shall be considered for grounding.considered for grounding.

““Equipment bonding jumpers: are they Equipment bonding jumpers: are they always necessary?”always necessary?”

Any questions?Any questions?