Current Transformer (CT) Metering (Single-Phase & Three-Phase)
Services greater than 400 amp (320amps continuous current) require CT metering. This type of metering system requires prior approval from a Skamania County PUD Representative and requires an additional construction charge. This service requires a different meter base and equipment.
Skamania PUD installs the CT’s, meter and associated wiring. The customer provides and installs any additional metering equipment beyond the service entrance. PUD approval is required for the location of the CT metering equipment.
Current Transformer (CT) metering is required in the following scenarios:
Three phase service exceeding 400 amp.
Single Phase service exceeding 400 amps (320 amp continuous).
CT Metering at either a pad-mount transformer or on a pole shall have no more than two (2) services fed from it.
CT Metering equipment shall meet the following requirements:
Securely mounted, plumb and level on the outside of the structure.
Rain tight and NEMA 3R-Rated.
6 feet maximum height to top of CT cabinet or center of meter socket.
Grounding and bonding of both the meter base and CT enclosure in accordance with the NEC and local governing office.
Bottom of CT cabinet is a minimum of 18 inches above final grade.
Side opening, hinged door with sealing provisions.
Factory-installed hinges located on the opposite side of the enclosure from there the meter socket is located.
Will not be used as a junction box or bus gutter.
CT Metering Conduit
CT Metering conduit between the CT enclosure and the meter base shall meet the following requirements:
1-inch minimum electrical conduit for single-phase service and 1 ¼-inch minimum for three-phase services.
Schedule 40 PVC or rigid galvanized conduit.
Grounding bushings at both ends of if galvanized conduit is used.
A continuous run, with no conduit bodies (LB joints, condulets, etc.).
Conduit installed with no more than (3) 90-degree elbows in the total length (270 degrees total).
Conduit entering the meter enclosure adjacent to the test switch.
CT Enclosure mounting base specifications:
401-800amp Single-Phase 30”W x 36”H x 11”D
401-800amp Three-Phase 36”W x 48”H x 11”D
CT Mounting Base
Installation requirement for current transformer mounting bases are as follows:
Mounting base is rated for a minimum of 50k amps fault current.
Line and load side terminations require two bolts per connector and two bolts on the neutral bus.
Customer furnishes all lugs and terminates both load and line side conductors to the bus.
A 4-wire delta service requires orange marking of the high leg.
Switchboard Metering
Switchboard metering is required for three-phase services over 800amps. At the customer’s option, this type of metering may be installed for services sized 201-800amp. The customer-installed equipment must be EUSERC-approved.
All customer-installed switchboards require:
Current Transformer (CT) mounting base.
Service section.
Set of bars/links.
Panel(s).
Meter base with provisions for a test switch.
Means for locking the meter enclosure with independent 24-hour access to utility personnel.
Case ground as required per the NEC.
Note: Customers requiring more than 480 volts of service will have primary metering. Ownership and maintenance agreements for primary metered services will be mutually agreed upon with Skamania PUD.
Grounding & Bonding Requirements
Grounding and bonding is critical for safety and electrical reliability. The customer is responsible to ensure that the electrical wiring and service equipment is grounded and bonded in accordance with the NEC and the local governing office.
Joint use describes a group of utilities that share pole space or trenches in an effort to keep installation and maintenance costs lower for the customer.
Customer may place telephone or cable television facilities in a joint trench with electric service conductors, providing the installation meets the requirements of Skamania County PUD.
Septic/Sewer lines and drainage fields are not allowed in a joint trench.
Whenever an existing Skamania PUD power pole is replaced or an overhead service is converted to underground and the pole has joint users attached, the pole will be abandoned to the remaining joint user on that pole. The PUD has no authority to remove or relocate other utilities on the pole. It is the customer’s responsibility to contact all joint use utilities for conversion of their services and to coordinate the removal of pole(s) prior to the beginning of the project.
Approval — Acceptable to the authority having jurisdiction.
Assessor’s Parcel Number (APN) — Identifying number assigned by the county assessor’s office to each taxable building lot in the county. Also referred to as the tax ID number.
Backfill — Native soil or soil brought in from another area, free from sharp objects, rocks, scrap building material, and corrosive material.
Call Before You Dig — Call 811 or (800) 424-5555 for the national one call underground utility locating service.
Clearance — A set distance between two objects.
Conduit — A listed or approved wireway with a smooth interior surface. Conduit may vary in size or schedule (wall thickness), depending on its usage, in accordance with codes and Lewis County PUD’ specifications.
Current transformers (CT) — A device used to measure the current flow of larger services (401 amps or greater) in conjunction with a low voltage meter.
Joint use — A group of utilities that share space on a utility pole or trench.
Meter jaw — A spring-loaded receptacle installed inside a meter base, interfacing the terminals of the meter to the source and load conductors of the service.
Meter post — A freestanding structure that supports the metering equipment owned and maintained by the customer.
Meter base — The mounting device consisting of meter jaws, connectors, and enclosure for accommodating socket-type meters.
Metering equipment — Any equipment associated with measuring electrical energy.
Neutral — The grounded conductor in a single-phase, 3-wire, or 3-phase, 4-wire system. The service conductor that is at zero potential to ground.
Secondary voltage — The lower voltage, after transformation, used to supply the customer with electrical energy. Normally less than 600 volts.
Self-contained — In reference to meter bases: a device designed and rated to continuously carry the entire capacity of the service entrance equipment through the meter.
Service entrance equipment — Service conduit, conductors, service mast, meter base, enclosures and service disconnect.
Service mast — The conduit attached to the top of the meter base used to intercept and support the overhead service drop.
Skamania County PUD representative — The designated representative responsible for design and coordination of new or upgraded services to utility customers.
Source — Skamania County PUD’ equipment (transformer, pedestal, pole) that supplies the customer’s electric service.
Subdivision/Short Plat — A residential parcel that has been divided 2 or more building lots.
Temporary service — An electrical service providing power to a customer on a temporary basis.
Transformer — Equipment used to reduce (step down) primary voltage to the secondary voltage required to supply the customer.
Underwriters Laboratories (UL) — A nationally recognized test laboratory that lists materials it has tested and accepted.
Skamania PUD metering equipment standards for single-family residential structures or commercial services (400amp or less) are based upon the single-phase service ratings. All meter bases that are installed shall meet the following general requirements:
Rated for exterior use and rain tight.
Ringed meter base cover (ringless will not be accepted).
Underwriters Laboratories (UL) rated.
Have unused openings in the enclosure tightly sealed from the inside of the base.
Installed level, plumb, and fastened securely to a rigid structure.
Secondary Surge Arrestor Meter Sockets will not be accepted.
Meter Mounted Transfer Switches will not be accepted.
If installing a Combination Service Entrance Device (CSED), the minimum distance between the center of meter socket to edge of meter base socket enclosure must be at least 7 inches, anything less will require customer to install new meter base and have it re-inspected by L&I at customer cost.
Note: Specific metering requirements for 200 amp and 400 amp services are listed below. It is the customer’s responsibility to install the appropriate meter base. The PUD cannot give guidance, any questions about the meter base need to be addressed by an electrician or the Washington Department of Labor & Industries.
200-Amp Service
The 120/240-volt 200-amp service is the most common service installed by Skamania County PUD. Typically, the size of service is installed to home with a living area of less than 2,400 square-feet. Depending upon the type of appliances, heating and cooling system or other equipment (hot tub, jetted tub, car charger, etc.) being installed, a larger service may be necessary. It is the customer’s responsibility to determine and notify Skamania County PUD of the electrical requirements based on connected load.
In addition to the meter base requirements mentioned earlier, meter bases for 200-amp underground services shall:
Be rated for 120/240 volts and 200 amps.
Contain 4-meter jaws and a connection point for the neutral conductor.
Accept 3-inch, PVC, conduit.
Have lugs (electrical connectors) that are marked to accept 4/0 aluminum conductors.
Note: Do not route service conductor through the center knockout located on the bottom of the meter base.
400-Amp Service
The meter base required for a 120/240-volt 400-amp service is called a class 320-meter base. It is larger than the 200-amp meter base, but it is still a self-contained metering system. It can be installed on residences where the continuous current rating is 320 amp or less. In addition to the meter base requirements mentioned earlier, meter bases for Class 320 for 400-amp services require:
Rating for 120/240 volts and 320 amps continuous current.
4-meter jaws and 1 connection point for the neutral conductor.
A Class 320 manual block bypass.
Lever bypass devices are not allowed.
Note: Do not route service conductor through the center knockout located on the bottom of the meter base. Any structure needing more than 320 amps of continuous current, a CT metered service will be required.
Self-Contained Commercial Meter Bases
Self-Contained, or direct connect meters, carry full load current and connect directly across full line voltage. A safety socket or bypass meter socket is required for all self-contained commercial meter systems.
A safety socket allows the utility to maintain self-contained metering systems without interrupting service to the commercial customer. The meter terminals are de-energized allowing utility personnel to safely perform routing meter maintenance. A safety socket style meter base is required for the following services:
All commercial three-phase services.
Single-phase 240/480 volt services (municipal lighting only).
Temporary commercial services that are three-phase or 480 volt.
Single-phase services with metering installed inside a meter enclosure.
Manual bypass meter sockets also allow maintenance of self-contained metering equipment while maintaining service to the customer. Meter terminals are not de-energized when by-passed. This style of meter base is acceptable for lower voltage, single-phase commercial services only. A manual bypass meter socket is required for:
All single-phase commercial services 240 volts or less.
120/208 volt single-phase commercial network meters.
The following commercial metering exceptions do not require a manual bypass or safety socket style meter base:
Single-phase commercial temporary services (120/240 or 120/208 voltages).
House meter sockets included in a factory-built multifamily residential meter pack.
Grounding & Bonding Requirements
Grounding and bonding is critical for safety and electrical reliability. The customer is responsible to ensure that the electrical wiring and service equipment is grounded and bonded in accordance with the NEC and the local governing office.
To ensure power reliability, all new underground service entrances must be within 200 feet of a transformer. If service entrance equipment is greater than 200 feet, the PUD will have to install a transformer at customer’s expense. The most common service entrance equipment are surface mounted and stand alone.
Surface Mounted Equipment
Service entrance equipment can only be surface-mounted, flush mounted equipment (where the conduit is in the foundation) is not acceptable.
Service equipment maintenance remains the customer’s responsibility.
Meter base, Schedule 40 electrical conduit and 36” Schedule 40 PVC 90-degree continual sweep must be secured to a structure prior to service being energized, any other sweeps or types of conduit (18-deg, 22-deg, ABS, DWV, etc.) will not be accepted.
Stand Alone Meter Post
Services to homes where the meter is on a post are customer-owned and maintained from the service disconnect to the structure. When installing an underground service not attached to a structure, refer to the following general specification and contact the local governing body for additional NEC requirements.
Meter base and PVC conduit shall be securely attached and mounted on a unistrut with steel structure that is encased in concrete, wooden meter post will not be accepted.
Have a 4-wire feed behind the meter that supplies the structure.
The service main must be located within 30 feet of the manufactured home but not attached to the structure (only factory-installed meter bases can be attached to manufactured homes).
See table below for size of conduit required for the PVC and 90º sweep on the Line Side of the service entrance.
Service Size
Minimum Service Entrance Conduit Requirement
100 amps or less
2 ½ inch, gray, schedule 40, PVC
101 to 200 amps
3 inch, gray, schedule 40, PVC
201 to 400 amps
3 inch, gray, schedule 40, PVC
Over 400 amps
PUD personnel will give guidance about conduit size for service entrance
Note: Exposed conduit from final grade to the bottom of the meter base is referred to as the service entrance conduit.
Other Types of Service Configurations
The following meter base configurations are no longer acceptable, no new customer equipment (i.e. meter base, riser, etc.) can be attached to a PUD pole. Any service requests that include modifying/altering customer equipment will result in customers requiring to install a stand alone meter base.
Skamania County PUD has two temporary services available, overhead and underground. During the site visit the Skamania PUD Representative will advise which route to take.
Overhead Temporary Service
Provide the meter base, PVC conduit, support, conductor (up to the weather head/service mast) and paneling based on the size of service needed.
Install temporary service pole within 30 feet of the transformer pole and no closer than 10 feet.
Have meter base inspected and approved by the Washington State Department of Labor and Industries. Permit and inspection sticker must be displayed.
Service drop conductor must maintain a minimum height of 12 feet over open space and 18 feet over driveways.
Consult and electrician or Washington State Department of Labor and Industries Electrical Inspector for current NEC guidelines for service entrance, meter base and grounding codes.
Once permanent service has been inspected, the PUD will de-energize the temporary service and remove the meter.
Underground Temporary Service
Provide the meter base, PVC conduit, support, conductor and paneling based on the size of service needed (if temporary service is not located near a transformer, the PUD will provide and install the conductor at customer’s expense).
Locate temporary service adjacent to but no closer than 3 feet from a Skamania County PUD pedestal or transformer with a minimum of at least 8 feet of extra conductor (measured at the transformer) for termination.
Have meter base inspected and approved by the Washington State Department of Labor and Industries. Permit and inspection sticker must be displayed.
Consult and electrician or Washington State Department of Labor and Industries Electrical Inspector for current NEC guidelines for service entrance, meter base and grounding codes.
Once permanent service has been inspected, the PUD will de-energize the temporary service, abandon the underground conductor and remove the meter.
If there is an existing service where the power must be removed, relocated or upgraded, the customer has to call in for a Service Request and pay the necessary application fee and schedule a site visit. Customer is responsible for the same items outlined in this handbook.
The customer shall remove all trees and brush from the power line easement, which will be maintained by the District in the future (for overhead facilities only).
District personnel will approve the clearing before the job is released for construction.
When clearing is needed in a public right-of-way, the District’s tree clearing personnel will do the clearing at the customer’s expense.
Prior to energizing service, the installed customer equipment requires an electrical inspection from the Washington Department of Labor and Industries (L&I). It is the customer’s responsibility to request the inspection and pay the appropriate fees.
Electrical installations must be inspected by L&I Electrical Inspector.
Meeting all the requirements for temporary and permanent service equipment in compliance with the NEC (National Electric Code), WAC (Washington Administrative Code) and any other federal, state and local codes and ordinances that apply to the project.
After customer equipment has an approved electrical inspection, it is the customer’s responsibility to notify Skamania PUD when the trench will be open for Skamania PUD to inspect the trench.
If electric service has been approved but not connected within sixty (60) days of inspection, PUD will require service be re-inspected by L&I at customer cost.
Skamania PUD will determine if an easement or right-of-way permit is required to install the line extension. The following is required prior to energizing service:
All required easements and road permits must be executed and on file with Skamania PUD prior to construction.
Customer is responsible to obtain the appropriate building permits and if applicable National Scenic Area land use permits.
Customer must obtain the necessary signatures on easement forms prepared by the District and will return the easement documents back to the District (original documents only, no copies).
Easements may be required from owner(s) of all properties that District facilities will cross, in addition to the property being served.
Customer shall secure all necessary easements at the customer’s expense.
The District will apply for the right-of-way permit on the customer’s behalf and the customer is responsible for all fees associated with this permit.
No work in the right-of-way shall be performed until this permit has been secured.
