service entrance equipment

SERVICE ENTRANCE EQUIPMENT

INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

INTRODUCTION



INTRODUCTION

SERVICE ENTRANCE EQUIPMENT:TRANSFORMERSMETERSMAIN DISCONNECT SWITCHPANELBOARDS & OVERCURRENT PROTECTION


TRANSFORMERSELECTRICAL SUPPLYDESCRIPTIONTYPESSIZE & RATINGLOCATIONCUSTOMER-OWNED

METERSSERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDS

TRANSFORMERS




TRANSFORMERS

DESCRIPTION:

DEVICE WHICH CHANGES THE VOLTAGE OF AN A-C CIRCUIT TO A HIGHER OR LOWER VALUE.




TRANSFORMERS

CONSTRUCTION:AN IRON CORE ON WHICH TWO SEPARATE COILS ARE WOUND. THE COIL (WINDING) WITH THE GREATER NUMBER OF TURNS HAVING THE HIGHER VOLTAGE AND THE ONE WITH THE FEWER TURNS THE LOWER VOLTAGE.




TRANSFORMERS

CONSTRUCTION:TYPES:

STEP-UP: INCREASES VOLTAGE.

STEP-DOWN: DECREASES VOLTAGE

WINDINGS:

PRIMARY: THE WINDING WHICH IS USED FOR INPUT TO A TRANSFORMER.

SECONDARY: USED FOR OUTPUT. THE SECONDARY MAY BE DIVIDED INTO SEGMENTS, SO THAT THE OUTPUT VOLTAGE DEPENDS ON WHICH SEGMENTS ARE USED.




TRANSFORMERS

SINGLE-PHASE:TWO-WIRE SECONDARY: HAS ONE WIRE GROUNDED, WHICH THEN BECOMES THE NEUTRAL.

THREE-WIRE SECONDARY: DIVIDED INTO TWO SEGMENTS. ONE LEAD IS AT THE END OF THE SECONDARY, A SECOND LEAD IS CONNECTED TO THE MIDPOINT OF THE SECONDARY & GROUNDED, & THE THIRD LEAD IS CONNECTED TO THE OTHER END OF THE SECONDARY.




THREE-PHASE TRANSFORMERS




TRANSFORMERS




TRANSFORMERS

OUTDOORS:ADVANTAGES:NO BUILDING SPACE REQUIRED.REDUCED NOISE PROBLEMS WITHIN THE BUILDING.LOWER COST.EASE OF MAINTENANCE & REPLACEMENT.NO INTERIOR HEAT GAIN PROBLEM.OPPORTUNITY TO USE LOW-COST, LONG-LIFE OIL FILLED UNITS.

DISADVANTAGES:VANDALISM.DIRECT SUNLIGHT DECREASES OUTPUT BY INCREASING OPERATING TEMPERATURES.OBJECTIONABLE APPEARANCE.




TRANSFORMERS

INDOORS:ADVANTAGES:GREATER SECURITY.EASIER TO CONCEAL (BASEMENT).

DISADVANTAGES:HEAT GAIN (REQUIRING A FREE OPENING OF 3 SQ. IN. / KVA OR A LOUVER OF 8 SQ. IN / KVA)MAY REQUIRE A FIRE RATED ENCLOSURE (VAULT)




TRANSFORMERS

CUSTOMER-OWNED TRANSFORMERS:LARGE USERS: COST SAVINGS IN BUYING LARGER QUANTITIES OF POWER AT THE DISTRIBUTION VOLTAGE FOR REDUCED RATES MORE THAN COMPENSATES FOR THE COST OF MAINTAINING THEIR OWN TRANSFORMERS.

SMALL USERS: SMALL SAVINGS WHICH NORMALLY DO NOT JUSTIFY HIGH INITIAL EXPENSE OF INSTALLING A TRANSFORMER.




TRANSFORMERS

CUT-OFF POINT FOR COST-EFFECTIVENESS:UTILITY RATES.

TRANSFORMER COSTS.

AMOUNT OF ELECTRICITY USED.


INTRODUCTIONTRANSFORMERSMETERSDESCRIPTIONLOCATION

SERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

METERS

DESCRIPTION:A DEVICE WHICH IS NORMALLY PROVIDED AT THE SERVICE ENTRANCE BY THE UTILITY COMPANY TO MEASURE HOW MUCH ELECTRICITY A FACILITY USES.

THE METER IS THE PROPERTY OF THE UTILITY.


INTRODUCTIONTRANSFORMERSMETERSDESCRIPTIONLOCATION

SERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

METERS

LOCATION:ALWAYS INSERTED AHEAD OF THE MAIN SWITCH TO PREVENT THEM FROM BEING DISCONNECTED.

CAN BE INSIDE OR OUTSIDE, BUT THE UTILITY PERSONNEL MUST HAVE ACCESS TO AN INSIDE METER.


INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTDESCRIPTIONFUNCTIONLOCATION

OVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

SERVICE DISCONNECT

DESCRIPTION:MEANS OF DISCONNECTING AN ENTIRE BUILDING FROM THE ELECTRICAL SERVICE.

IT MAY BE MORE THAN ONE SWITCH, BUT NO MORE THAN SIX.

MAIN SWITCHES CONTROL ALL THE CIRCUITS IN THE BUILDING


INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTDESCRIPTIONFUNCTIONLOCATION

OVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

SERVICE DISCONNECT

FUNCTION:DE-ENERGIZES ALL ELECTRICAL EQUIPMENT & CIRCUITS DURING MAJOR REPAIRS.ALLOWS THE FIRE DEPARTMENT TO MAKE CERTAIN THAT THERE ARE NO LIVE WIRES INSIDE THE BUILDING.

LOCATION:NEAR THE POINT OF SERVICE ENTRY INTO THE BUILDING.


INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTOVERCURRENT PROTECTIONDESCRIPTIONFUNCTION TYPES

PANELBOARDSSWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

OVERCURRENT PROTECTION

DESCRIPTION:DEVICES DESIGNED TO DISCONNECT A CIRCUIT AUTOMATICALLY WHENEVER THE CURRENT REACHES A PREDETERMINED VALUE THAT WOULD CAUSE A DANGEROUSLY HIGH TEMPERATURE IN THE CONDUCTOR.HIGH TEMPERATURES CAN BE CAUSED BY SHORT CIRCUITS, EXCESSIVE DRAW OR A SURGE FROM THE UTILITY COMPANY.





FUNCTION:PREVENTS ELECTRICAL FIRES.PREVENTS POSSIBLE EXPLOSION.PREVENTS DAMAGE TO EXPENSIVE EQUIPMENT.





FUSES:CONTAIN A SHORT STRIP OF METAL WITH A LOW MELTING POINT. WHEN INSTALLED IN ITS FUSE-HOLDER, IT BECOMES A LINK IN THE CIRCUIT.FUSES ARE ONE-TIME DEVICES.MORE RELIABLE THAN CIRCUIT BREAKERS.





CIRCUIT BREAKERS:CONTAIN A SIMPLE MECHANISM THAT TRIPS OPEN A CIRCUIT IN RESPONSE TO AN OVERLOAD CONDITION.CONVENIENT: CAN BE RESET BY A MANUAL SWITCH TO RESTORE POWER.CAN SERVICE AS A SWITCH TO TURN A CIRCUIT ON OR OFF.MORE EXPENSIVE THAN FUSES TO INSTALL.


INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSDESCRIPTION & FUNCTIONLABELING

SWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

PANELBOARDS

DESCRIPTION:THE BOX IN WHICH THE CIRCUIT PROTECTIVE DEVICES ARE GROUPED & FEED, ALONG WITH THE SERVICE DISCONNECT SWITCHES & SWITCHES TO MAJOR BRANCH LINES.

FUNCTION:PANELBOARDS ACCEPT A RELATIVELY LARGE BLOCK OF POWER & DISTRIBUTE IT IN SMALLER BLOCKS.


INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSDESCRIPTION & FUNCTIONLABELING

SWITCHGEAR & SWITCHBOARDSUNIT SUBSTATIONS

PANELBOARDS

LABELING:LP: LIGHTING PANEL

KP: KITCHEN PANEL

AHU: AIR HANDLING UNIT.

AC: AIR CONDITIONING


INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDSDESCRIPTIONLOCATION & SPACE REQUIREMENTS

UNIT SUBSTATIONS

SWITCHGEAR & SWITCHBOARDS

SWITCHBOARDS:LARGE BUILDING OFTEN HAVE THEIR MAIN (PRIMARY) SWITCHES TOGETHER WITH THEIR SECONDARY (FEEDER) SWITCHES, & CIRCUIT PROTECTION DEVICES ALL ENCASED IN A FREESTANDING ASSEMBLY CALLED A SWITCHBOARD.

SWITCHGEAR:SUCH A PACKAGE DESIGNED FOR HIGH-VOLTAGE (ABOVE 600-V)SWITCHING EQUIPMENT IN MULTIPLE UNITS, NOT CONSOLIDATED IN A SINGLE UNIT.


INTRODUCTIONTRANSFORMERSMETERSSERVICE DISCONNECTOVERCURRENT PROTECTIONPANELBOARDSSWITCHGEAR & SWITCHBOARDSDESCRIPTIONLOCATION & SPACE REQUIREMENTS

UNIT SUBSTATIONS

SWITCHGEAR & SWITCHBOARDS

LOCATION:GENERALLY IN THE BASEMENT WITHIN A SEPARATE, WELL-VENTILATED ROOM DESIGNED FOR THAT PURPOSE.

SPACE REQUIREMENTS:EXACT SPACE REQUIREMENTS ARE OBTAINED FROM THE ELECTRICAL CONSULTANT.



UNIT SUBSTATION

DESCRIPTION:A SINGLE PACKAGE COMBINING A STEP-DOWN TRANSFORMER WITH A COMPLETE SWITCHBOARD AND METERS.ALSO CALLED A LOAD-CENTER SUBSTATION.

service entrance equipment

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