HANDBOOK REQUIREMENTS - Central Maine Power Company

electrode conductor and is acceptable to the “authority having
jurisdiction.”
For all ungrounded services (3 phase, 3 wire), the bonding
must provide a permanent, low-impedance path (from the service
disconnect) all the way back to the electrical supply
source
(CMP
grounded primary system neutral). The earth shall not be
considered
as an effective fault-current path. Note: the
customer/electrician
must provide the necessary
bonding/equipment
grounding from the service disconnect to the
"point of delivery/service point." This may include metal conduit
with appropriate
"listed" bonding clamps or a fourth
grounding/bonding
wire.
This bonding requirement for ungrounded services not only
provides for an effective ground-fault current path "should a
second fault occur;" it also ensures that a "hazardous potential
difference" will not
exist between the Company's grounding
system and the customer's service entrance grounding. See
paragraph 702 of this handbook for more details on "bonding."
701. GROUNDING ELECTRODE SYSTEM
In accordance with NEC Section 250-III, the service
grounding electrode system shall consist of all items 1 through 7,
that are available, bonded together per NEC Sections 250.64(A),
(B), (E); 250.66 and 250.70. If none of the items 1 through 7 are
available, then one or more of items 4 thru 8 shall be installed and
used.
1. Underground metal water pipe in direct contact with
the earth for at least 10 feet supplemented with at least one
additional item below (2 thru 8). Where the supplemental
electrode is a rod, pipe, or plate; it shall comply
with Note
2, below, i.e., NEC Section 250.56.
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