INTRODUCTION
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This booklet is issued primarily as a convenient
reference for customers, architects, engineers and contractors planning or
constructing buildings or installing, repairing, or renewing apparatus or
equipment to be connected to the Company’s distribution system. Any future reference to the Company will
imply Mississippi Power Company unless otherwise stated.
The practices discussed have been derived from
research, experience and technical consideration. As
such they are supplementary to and do not intentionally conflict with the
National Electrical Code or state and municipal laws and ordinances that may be
in force within the cities, towns, or communities in which the Company
furnishes electric service. If any
conflict exists, the Code, law, or ordinance shall control.
It is always necessary to refer to and comply with
applicable codes, statutes, utility commission rules, and local
ordinances. The information contained
herein is general and does not include every detail or every lawful
requirement.
The Company desires to serve its customers promptly
and satisfactorily. It will endeavor to
cooperate with contractors and customers to the fullest extent in completing
service connections with as little delay and inconvenience as possible and will
gladly give special attention to any particularly difficult situation
confronting a customer.
The Company will be pleased to confer with those
desiring information concerning rates, services, etc., upon request.
General Information
Ampere Rating -
The maximum
allowable current that can safely pass through a device.
Approved - Acceptable to a qualified
Mississippi Power Company employee.
Class of
Service -
The voltage rating and the number of phases for a particular service.
Company - Mississippi Power
Company.
Conduit - A tubing or duct in which
electric wires or cables are enclosed.
Current
Transformer (CT) - A device which reduces the load current by a known ratio for
metering purposes.
CT Enclosure (Instrument Transformer Enclosure) - A metal cabinet which houses
instrument transformers.
CT Socket (Instrument Transformer Rated Source) - A meter socket that is used
only with instrument transformers.
Customer - The corporation,
municipality, governmental agency, association, partnership or individual using
or planning to use electric service supplied by the Company or the architect,
engineer, or electrical contractor acting as the customer’s agent.
Diversified
Demand - A
company calculation to determine the maximum anticipated load (kw) based upon
the customer’s usage patterns and operation.
Electric Service - Electrical energy that is made available to the customer
at the point of delivery.
Energy - The measure of work
done. The electrical unit of energy is
the kilowatt-hour, which is 1,000 watt-hours.
Final Grade - Ground level after all
construction and landscaping procedures have been completed.
Grounded
Conductor -
A system or circuit conductor that is intentionally grounded.
Grounding
Conductor, Equipment - The conductor used to connect non-current carrying metal parts of
equipment, raceways, and other enclosures to the system grounded conductor
and/or the grounding electrode conductor at the service equipment or at the
source of a separately derived system.
Grounding
Electrode Conductor - The conductor used to connect the grounding electrode to the
equipment grounding conductor and/or to the grounding conductor of the circuit
at the service equipment or at the source of a separately derived system.
Instrument
Transformer
- A current transformer or potential transformer used in metering.
Instrument
Transformer Enclosure (CT Enclosure) - A metal cabinet which houses instrument
transformers.
Isolated
Location -
Not readily accessible to persons unless special means for access are used.
Listed Equipment- Equipment or materials included in a list published by
an organization acceptable to the authority having jurisdiction and concerned
with product evaluation. This
organization maintains periodic inspection of material or devices and finds
them suitable for use in a specified manner.
i.e.
Underwriters Laboratory (U.L.)
Maximum
Available Fault Current - The maximum amount of current that can flow when a fault (short
circuit) condition exists between a conductor and ground or between two or more
conductors at a given location.
Meter - A device that measures
the amount of power and/or energy delivered to a customer.
Meter Socket - A weatherproof receptacle
used for mounting a socket type meter.
National
Electric Code (NEC) - The National Electrical Code, ANSI/NFPA 70. The code which governs the installation of
electric conductors and equipment within or on public or private buildings or
other structures. At the time of this
printing, the current revision of the code is the 1993 edition. Future revisions of the National Electrical
Code may change the requirements of the code or the references contained
herein.
National
Electrical Safety Code (NESC) - The National Electrical Safety Code, ANSI
C2-1993. The code which governs the installation,
operation, and maintenance of electric supply and communication lines,
equipment, and associated work practices employed by utilities. Future
revisions of the National Electrical Safety Code may change the requirements of
the code or the references contained herein.
Neutral - The grounded service which
carries the unbalanced 60 hertz current from other conductors.
Point of
Delivery -
The point at which the customer’s conductors are connected to the Company’s
conductors.
Potential
Transformer (PT) - A device which reduces the service voltage by a known ratio for
metering.
Power (Demand) - The average rate of
energy used over a period of time. A 15
minute interval is used for billing purposes.
The unit of measure for power is the Kilowatt (kW), which is 1000 watts.
Qualified
Employee -
A Mississippi Power Company employee familiar with company safety rules and
regulations and the construction, application, and operation of the equipment
involved.
Raceway - An enclosed channel
designed expressly for holding wires, cables, or bus bars.
Readily
Accessible
- Capable of being reached quickly, for operation, renewal, or inspections
without requiring those to whom ready access is requisite to climb over or
remove obstacles or to resort to portable ladders, chairs, etc.
Service - The conductors and
equipment for delivering energy from the electricity supply system to the
wiring system of the premises served.
Service Drop - The overhead service
conductors that extend from the Company’s last pole or aerial support to and
including the splices, if any, connecting the customer’s service entrance
conductors at the building or other structure.
Service
Entrance -
The customer’s conductors, conduit, and other associated equipment which
extends from the point of delivery to the service equipment.
Service
Entrance Capacity - The maximum rated allowable current passing through the service
equipment.
Service
Entrance Conductors: Overhead System - The service conductors
between the terminals of the service equipment and a point usually outside the
building, clear of building walls, where they are joined by tap or splice to
the service drop.
Service
Entrance Conductors: Underground System - The service conductors
between the terminals of the service equipment and the point of connection to
the service lateral.
Service
Equipment -
The necessary equipment, usually consisting of a circuit breaker or switch and
fuses, and their accessories located near the point of entrance of supply
conductors to a building or other structure, and intended to be the main
electrical supply disconnect.
Service
Lateral -
The underground service conductors between the Company’s distribution system
and the point of delivery including any risers at a pole or transformer.
Special Permission - The written consent of
the Company.
Weatherproof - So constructed or
protected that exposure to weather will not interfere with successful
operation.
When the Company connects a customer’s installations
to its supply lines, arrangements are made for meters, transformers, and other
equipment to fit the installations as it is at that time. For maximum safety
and billing accuracy, it is essential that the customer or contractor give notice
to the Company before making any changes which will significantly increase or
decrease the electrical load, reduce conductor clearances, or enclose or
restrict access to Company facilities.
The Company maintains local offices strategically
placed throughout its service area as well as a company-wide customer service
center. Information concerning original
or added service should be directed to the Customer Service
Center
The customer shall provide, free of expense to the
Company, suitable locations and space for the transformer(s), meters, and other
equipment owned by the Company which are necessary to supply service.
An application for service will be considered
permission to cross the customer’s property and install any equipment which may
be necessary to provide electric service.
To avoid unnecessary delays, applications for
service should be made as far in advance of required service date as
possible. Specific instructions for
locating the service address, will help to assure prompt service.
The customer should consult the Company well in
advance of the date that service is required in order to determine what type of
service is available in a particular location.
A qualified company employee will determine the voltage, phase, etc. of
a particular service since the availability may vary between different
locations.
The information contained in this booklet refers
primarily to service requirements at secondary distribution voltages (under 600
volts) for light and power installations.
Service requirements for installations requiring higher distribution
voltages are subject to special negotiations between the customer and the Company.
The Company is available to advise customers
concerning the use of electrical equipment or situations not covered in this
book.
The Company shall connect only one service drop or
service lateral to a building or structure for each class of service except as
permitted by Section 230-2 of the National Electrical Code.
Only one watt-hour meter shall be installed per
customer per class of service. An
exception will be made if the characteristics of the customer load or billing
rate require the Company to utilize multiple meters. Multiple meters will not be used for the
customer’s benefit.
On installations comprising more than six meters, a
sealable main disconnect or main breaker, of a type acceptable to the Company,
shall be provided as required by the National Electrical Code. The customer will always provide and maintain
any main breakers or disconnects
Compatibility between the Company’s distribution
system and the customer’s wiring system is of utmost importance. Because of this the following operating
procedures are recommended to the customer:
· To safeguard both the
property of the customer and that of the Company, the customer is warned
against overfusing either the main fuse or those on branch circuits by
installing fuses or circuit breakers larger than approved by the National
Electrical Code, or in any way making protective devices of any type
inoperative.
· The customer’s wiring and
equipment should be maintained in the condition required by inspection
authorities having jurisdiction. The
customer should use equipment and service in such a manner as not to disturb
the company’s service to other customers.
· When designing a wiring system, the customer should
balance the load connected across each phase of the system as nearly as
practical.
· The customer’s wiring and equipment is to be
installed and maintained by the customer in the condition required by the NEC
or governmental authorities having jurisdiction.
· Customer equipment must not introduce electric or
magnetic interference on the Company’s system.
· Control devices such as those used for lighting and
motor control shall be of such design as to introduce a minimum of harmonic
distortion or other disturbances into the Company’s system. These are detailed on page 11.
· The customer shall not use electric energy from any
other source while being supplied by the Company without written consent of the
Company.
· Electric service supplied to a customer shall not be
resold or shared with others. An
establishment which supplies electricity purchased from the Company to its
tenants without any specific energy charges will not be considered as sharing
with others.
Application for temporary service should be made
well in advance of the required service date.
To insure prompt service, the location of the temporary service should
be plainly marked with the lot number and/or street address as shown on the
service application.
G. Extensions:
In order to avoid delay, persons desiring service
beyond the existing electric distribution lines of the Company should consult
with the Company for the conditions under which service may be provided, and
make the necessary arrangements before wiring installations are started.
The following requirements and suggestions apply to
motors connected to the secondary distribution systems of the Company:
The National Electrical
Code requires that all motors be equipped with suitable starting switches and
have overload protection.
The use of automatic
time-delay circuit breakers for circuit protection in all cases is strongly
recommended and where fuses are used they should be of the time-delay
type. This time delay will, in many
instances, prevent unnecessary shut-downs due to the tripping of an
instantaneous type circuit breaker or blowing of ordinary short time fuses by
large currents resulting from motor starting, temporary overloads or temporary
low voltage conditions and ordinarily will provide adequate protection. All automatic controls using the time delay
should be coordinated.
In general, 120 volts
single phase motors may be connected to a 2 wire, single phase service,
provided the locked rotor current does not exceed 50 amperes. Motors in excess of 50 amperes may be
connected to a 240 volt, 3 wire service, provided the locked rotor current does
not exceed 150 amperes. Any applications
of single phase motors exceeding these requirements are to be referred to the
Company.
All single phase motors
should be connected for 240 volts whenever it is practical to do so in order to
minimize voltage drop in the customer’s wiring system and the supply system.
Before any polyphase
motors are installed it is advisable that the Company be consulted in order to
determine the type and adequacy of the available service. Where three phase service has been secured,
polyphase motors over 50 horsepower shall not be connected without utility
starting equipment or other suitable technologies that limit starting current.
It is important to maintain the power factor of any
load as near unity as possible. The
maintenance of a high power factor may result in the reduction of conductor
losses and equipment capacity requirements as well as higher overall efficiency.
In general, capacitors must be applied more
carefully than most types of electrical equipment in order that satisfactory
operation and maintenance will result.
The customer should confer with the Company before any installations of
this type of equipment are made.
Improperly installed generation equipment can create
serious hazards to Company personnel working on the distribution system as well
as for other customers connected to the distribution system. The operation of improperly installed
generators can also result in damage to customer’s wiring, electrical equipment
or the generator itself. To safeguard
against these hazards, customer owned generators shall be installed as follows:
· Standby generators shall be installed in compliance
with the National Electrical Code and local codes. Customers
utilizing emergency or standby generators shall provide an adequately sized
double throw switch which will open all ungrounded conductors from the normal
supply before connection is made to the emergency supply, and vice versa. Power from a standby generator must never be
supplied to another premise because of the danger created by back-feeding into
the distribution system.
· Subject to special requirements the Company will
allow customer operation of parallel generating facilities. Generators designed
to run parallel with the Company’s system require special protective devices
and operation coordination. Cogeneration
is not allowed unless the Company is consulted prior to the installation and
operation of parallel generators. Please consult the Company for specific
requirements. A written agreement must
be executed before interconnection.
The customer may
install an uninterruptible power supply on his system. An automatic transfer switch must be provided
by the customer to disconnect the normal supply in the event of a power outage.
The integrity of electric service is of utmost
concern to the Company. Normal system
operations and unavoidable system disturbance may, however, cause customers to
experience problems with certain types of equipment, most notably computers. If the customer should experience equipment
malfunctions caused by system disturbances, the Company stands ready to advise
and assist the customer in resolving these problems. Please contact a qualified employee.
The Company will, at all times, exert itself toward
the goal of supplying as nearly constant service as is reasonably
practicable. However the Company does
not and cannot not guarantee the supply of electric energy will be free from
temporary interruptions. Temporary
interruptions of the Company’s service shall not constitute a breach of the
Company’s service obligations.
The Company is not liable for any damage which the
customer may sustain by reason of the failure or partial failure of the
service, or failure or reversal of phases, or variation in service
characteristics, whether caused by accident, variation in service
characteristics, repairs or other causes; nor is the Company liable for damage
that may be incurred by the use of any service wiring, connections,
instruments, services or electrical appliances, installed by or for the
customer; nor is the Company liable for damage that may be incurred due to the
presence of the Company’s property on customer’s premises.
In the event of interruptions of service, the
Company will restore the service as soon as reasonably practical. In the event conditions on the customer’s
premises cause an interruption, the Company will allow a reasonable time for
those conditions to be corrected, but reserves the right to disconnect the
service until the conditions are corrected to preserve the safety and
reliability of the Company’s system.
If the customer requires three phase service, the
installation and maintenance of adequate relays with circuit breakers to
protect against single phase conditions and phase reversal are advisable. Their installation and maintenance is the
responsibility of the customer.
To avoid unnecessary delays, the availability of
types of service should be confirmed with the Company before construction
begins.
The point of connection between the Company’s
service drop and the customer’s wiring system should be located at a point
convenient to both the Company and the customer. Normally, the point of
connection for an overhead secondary service is at the drip loop where the
service is attached to the customer’s structure. To comply with the appropriate safety codes,
the point of connection must provide service drop clearances from
windows, doors, awning or other parts of the building not less than those
required in the current NEC. However,
the service drop point of attachment shall not exceed 30 feet above final
ground level.
The service drop will be attached to the customer’s
building at the point of connection only.
Multiple points of attachments such as the service drop being attached
to a corner of the building and then running to the point of connection will
not be allowed.
If the type of building will not permit these
minimum clearances, some satisfactory form of service mast must be provided to
obtain them. The recommended structure
for this purpose is a galvanized service mast through the roof. This mast shall have minimum strength equal
to that of 2 inch inside diameter rigid steel conduit and shall extend above
the roof the distance required by the National Electrical Code to give adequate
clearance for overhead service conductors.
Where long service drops are required, a larger size conduit may be
necessary. The service mast shall be
sufficiently braced to support the service conductors and shall be located at a
point on the building where the service conductors from the pole will not overhang the roof, except for the
overhanging eaves. The service mast must
be secured by retaining straps placed no further apart than 24 inches. A minimum of two straps is required. There are to be no joints in the conduit
above the straps. The portion of the
service drop passing over the roof, including overhanging eaves, shall not
exceed four feet. The clearance between
the service drop and roof shall not be less than 18 inches at any point.
Safe and adequate anchorage structures for the
Company’s service drop and/or connections are required of the customer and in
no case will the Company be responsible for the conditions of any customer’s
buildings or structures to which service wires are attached or have been
attached.
Where service wires are to be installed on the side
of buildings which have stucco, hollow tile, stone, brick, brick veneer,
plaster, or sheet metal walls, and where there is available no surface suitable
for the attachment of service supports having a screw fastening (house knob),
the customer will install a suitable anchorage bolt or spool rack. Where the load to be served is sufficiently
large to require the use of overhead service conductors of No. 4/0 aluminum and
larger, 5/8” galvanized bolts for spoolracks or 5/8” eye bolts are
required. Where the service conductors
are smaller than No. 4/0 aluminum, the bolts may be smaller than 5/8 inch but
in no case smaller than 3/8 inch diameter.
These bolts are to be spaced to conform to the conductor spacing as
specified by the Company and should extend through the wall and each be
anchored on the inside surface with a substantial washer not less than 1/8 inch
thick and two inches square.
To prevent moisture from entering the raceways of
conduit for service entrance conductors or service entrance cable, it is
advisable to terminate them on the outside building wall at a point
approximately 6 inches above the point of attachment of the highest service
drop wire. The individual service
entrance conductors are to extend downward to the points where connections are
made to the service drop wires to form a drip loop. Each conductor of the service entrance must
extend not less than TWO FEET beyond
the service head to allow adequate wire for the drip loop and connection.
The availability of underground service should be
confirmed with the Company before construction begins.
Point of
Service/ Location
The point of connection between the Company’s
service lateral and the customer’s service entrance conductors shall be
determined by a qualified employee after consultation with the customer
Padmounted transformers shall normally be located a
minimum of 10 feet from a building. Clearance
can be reduced (consistent with the applicable Code) if approved by the Company
and the local inspection authority.
Padmounted transformer locations are to be readily accessible and free
from obstructions. They shall also be
located where adequate natural airflow occurs preventing excessive transformer
heating. The Company will make a final
determination of the locations adequacy.
Locations are to be approved by the Company prior to construction.
In certain prescribed districts or streets in downtown
areas where the Company maintains an underground distribution system,
underground services are installed by the customer at the customer’s expense
from an underground connection point generally in a company-provided hand hole,
man hole, or vault at or near the property line of the customer. The Company will extend its service
conductors not more than five feet inside the property line to these junction
points.
When an instrument transformer enclosure is used,
the point of connection (demarcation) shall be in this enclosure.
Service laterals, conduits, and accessories shall be
furnished and installed by the customer and shall remain the property of the
customer. The final connection of customer service
entrance conductors will be made at the transformer by the Company. Company metering shall be located at one
level only, preferably at the ground floor or basement level.
Generally, if the commercial/industrial customer is
served from a padmounted transformer which is dedicated to that customer only,
the point of connection will be at the secondary terminals of the padmounted
transformer. MPC will furnish secondary
connectors and install conductors at the padmount provided the provisions
concerning maximum number of conductors per phase on page 13 are made. Consult the Company for specific details.
Special company policies cover residential
underground services. Please consult the
Company for specific requirements. The
Company will install, own, and maintain service lateral conductors to the service
location on the outside wall of the residence.
This point should be the closest point to the Company’s distribution
facilities.
Each socket and service equipment in a group must be
plainly and permanently marked to designate the particular suites, offices, or
apartments served.
Conduit/Conductors/Raceways
All conduit and direct buried conductors shall be
buried at a depth of not less than 30 inches below final grade.
Service voltage supplied from single phase
pad-mounted transformers will be 120/240 volts.
Services from three phase padmounted transformers
shall be either 120/208 volts or 277/480 volts as determined by the Company.
Metering equipment shall not be mounted in or on
single phase, padmount transformers.
· Conduit must be securely fastened to the wall within
12 inches of the meter socket and 6 inches of final grade level. Conduit straps shall be fastened to walls
with the same type fasteners as meter sockets.
· Inhibitor of the non-grit type must be applied to
conductors when aluminum conductors are used.
· Safety dictates all meter
positions shall be properly covered before the meter socket is energized.
· The service entrance
conductors must be run in sealable metal raceways or the equivalent.
Where the customer desires a particular meter socket
alignment not provided by the Company, it becomes necessary for the customer to
furnish these devices. If a customer
chooses to use meter sockets not furnished by the Company, he shall notify the
company well in advance of required service date and shall comply with the
following specifications. The Company
will make the final determination of a device’s suitability
· Customer purchased equipment shall be Underwriter
Laboratory (UL) listed. The label,
symbol, or the identifying mark used by the testing laboratory shall be affixed
to the unit.
· Each meter socket shall be rated not less than the
rating of the service equipment when used on single family dwellings. Each meter socket position shall be rated not
less than the ampacity of the service or feeder conductors connected to the
load side of the socket where multi-position metering assemblies are used.
· Line side connectors of meter socket assemblies to
be connected to Company Service laterals shall be of a type satisfactory to the
Company and comparable to company specifications for similar equipment. The main bus of assemblies connected shall be
rated not less than 100 amperes multiplied by the number of meter positions but
not more than 1000 amperes.
· Line side connectors shall be designed and listed
(UL486B) for the conductors (size and number) utilized in the assembly. Recommended torque values for all connectors
shall be clearly marked in the connector compartment. All conductor strands shall be contained
beneath the connector pressure device (set screw, pad, etc.)
· All meter spade jaws shall be spring reinforced.
· Ring type sockets must be equipped with Company
approved screw-type sealing rings.
· Connectors for more than one conductor and
connectors used to connect aluminum conductors must be approved for the
purpose. Inhibitor of the non-grit type
must be used on all aluminum conductors.
The Company will not accept more
than one conductor under one pressure device (set screw, pad, etc.)
· Conductors carrying unmetered energy shall not be
contained in the same compartment, conduit, or raceway with conductors carrying
metered energy.
· Meter sockets installed outdoors must be
weatherproof (NEMA Type 3R). They shall
also be of galvanized steel or aluminum construction. A unit is considered to be outdoors unless it
is installed within the confines of the main structure of the building and
totally protected from the weather.
Units installed in metering room attached to a building will be considered
outside unless the metering room is connected to the main structure of the
building and has the same roofing as the building and roof flashing is
installed.
· Multi-position, customer owned, meter sockets shall
be constructed so the line side wiring compartment is separate from
compartments housing service equipment or meter sockets and is accessible
without having to remove any meter(s).
Each meter position’s cover shall be removable without having to remove
any other cover(s).
· The customer shall be responsible for all
maintenance of meter sockets not furnished by the Company. The Company shall affix a disclaimer
statement to each customer owned meter socket in a place conspicuous to both
Company personnel and customer which reads as follows:
NOTICE: This meter mounting
device was not furnished by Mississippi Power Company and is not the property
of Mississippi Power Company.
Mississippi Power Company shall not be liable for any damage or injury
caused by failure of this device or for repair or replacement of this device or
any parts contained therein.
The sole purpose of this disclaimer statement is to
inform the customer and electrical contractor that Mississippi Power Company
does not own this device and does not assume any liability for damages that
might be caused by the device or any responsibility for maintenance for the
unit. It does not in any way imply that
the meter socket assembly is inferior or unsafe.
When the customer desires to be served from transformers
in a customer owned transformer vault or room the customer shall consult the
Company for requirements and specifications.
Meters should be readily accessible as defined on
pages 6, 14 and 15.
R. Grounding:
Grounding electrodes and conductors are to be sized
in accordance with the National Electrical Code with the following
exceptions. The minimum grounding
electrode size shall be an 8 foot 5/8 inch galvanized ground rod. The minimum grounding conductor size shall be
No. 4 copper. The grounding conductor
shall be terminated on the neutral bus in the meter socket.
Temporary service poles shall be grounded using an 8
foot ground rod as per pages 31 & 33.
(Butt wrapped grounds are not
permissible.)
Transformer rated installations must have a separate
grounding provision as shown on pages 55, 67, 77, & 79.
Unauthorized attempts to divert energy, tamper with
metering equipment, or gain unauthorized access to Company electric facilities
can be dangerous. Persons attempting
these activities expose themselves to the risk of serious or fatal injury. These activities can also lead to fires or
other property damage.
Unauthorized removal, tampering or damaging a meter
or meter enclosure, breaking the seal, or the use of any method or device which
permits the flow of unmetered or unauthorized electricity into a premise is a
criminal act. Violators are subject to
prosecution under state and local laws.
Any damage caused by tampering with company property
will be paid for by those tampering with the metering equipment.
When a customer needs a seal removed in order to
inspect his system, make repairs or make modifications, he must call the
Company so that company personnel can be dispatched to remove the seal. When the work is complete and the Company has
received notice from the inspecting authority, if needed, the Company will
again dispatch personnel to resecure the installation.
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