Current transformers (C.T.s) shall be furnished, installed, and owned by the District. Contractor installed 1 inch diameter rigid galvanized or 1 inch SCD 40 rigid PVC conduit shall extend from the meter base to the approved instrument transformer enclosure located at a distance not to exceed 50 feet. For distances greater than 50 feet, contact the District. No conduit outlet bodies or other non-sealable fixture shall be allowed between the C.T. enclosure and meter base. Metering connectionsshall be made by the District. The Contractor shall identify and tag all conductors indicating common phase and whether they are source and load.
Section 4.1 Ampacity up to 800 Amps
Section 4.1.1 General
District C.T.s shall be mounted in Customer provided, owned, installed and maintained enclosure, compartment, box, or as part of panel boards as specified herein. The C.T. enclosure, compartment, box, etc., is dedicated for metering purposes only. Unauthorized access is not permitted. No Customer equipment or other wiring shall be allowed in or to pass through the dedicated space. C.T.s shall normally be installed on the source-side of the service disconnect - unless otherwise authorized by variance process.
Section 4.1.2 Outdoor Installation
All C.T. installations rated at 800 amps or less shall be mounted outdoors and shall be installed in weather tight approved cabinets, except C.T.'s mounted on poles(See Section 4.1.11). In some areas the exposed portions of CT enclosures must be fabricated using 300 series stainless steel. Contact a District representative for any service location within ½ mile of a coastline.
Section 4.1.3 C.T. Enclosure and Conduit by Customer
Customer provides the C.T. enclosure with landing pads rated for the service ampacity, installs line and load-side wiring, and provides necessary “meter conduit.” The Customer shall terminate all service conductors to the current transformer landing pad. All connectors shall be bolted to the landing pads with stainless steel bolts, flat washers, Belleville washers and silicone bronze nuts or installed into lugsthat are provided with the C.T. enclosure as per detail on Drawing #33. The high leg conductor of a delta service shall be marked with orange tape and connected on the right-hand side in the C.T. enclosure. The Contractor shall identify and tag all conductors indicating common phase and whether they are source or load.
Section 4.1.4 District Instrument Transformers
The District provides and installs bar-type C.T.s. The District attaches the C.T.s to the landing pads mounted to the back of the current transformer enclosure and installs the metering conductors and test switches and installs the meter.
Section 4.1.5 the C.T. Enclosure Sizes Required
The C.T. enclosure sizes required shall be as listed below:
| Service Size | Minimum Enclosure size (Height x Width x Depth) |
|---|---|
| 400 Amperes Single Phase | 36 inches x 36 inches x 11 inches with Hinged Door |
| 600 Amperes Single Phase | 36 inches x 36 inches x 11 inches with Hinged Door |
| 800 Amperes Single Phase | 36 inches x 36 inches x 11 inches with Hinged Door |
| 400 Amperes Three-Phase | 36 inches x 36 inches x 11 inches with Hinged Door |
| 600 Amperes Three-Phase | 48 inches x 36 inches x 11 inches with Hinged Door |
| 800 Amperes Three-Phase | 48 inches x 36 inches x 11 inches with Hinged Door |
In some instances, larger enclosures may be required to accommodate conductor bending radius requirements.
Section 4.1.6 Cabinet Cover Size
Cabinet covers, pull box covers, C.T. cabinet covers, and any miscellaneous service equipment covers shall be limited to 36 inches by 48 inches. All covers shall be hinged. All doors shall be equipped with provisions for locking.
Section 4.1.7 Cabinet Mounting Height
Current transformer enclosures shall be mounted such that the bottom of the enclosure is no higher than 3 feet above grade or the bottom lower than 6 inches above grade. (See Drawing #26).
Section 4.1.8 No Meters on C.T. Enclosure Cover
The cover of an instrument transformer enclosure shall be free of meters or equipment.
Section 4.1.9 C.T. Enclosure Not a Conductor
The current transformer enclosure shall not be used as a current carrying conductor.
Section 4.1.10 Enclosures Shall Be Grounded
All outdoor current transformer enclosures shall be grounded with a #6 copper ground wire to a ground rod at the meter location. (See Drawings #25, 26, 27, and 28).
Section 4.1.11 C.TS Mounted on Service Poles
C.T.s may be mounted on service poles when the Customer wiring extends directly from the service pole to multiple load centers. The District shall supply a suitable mounting bracket for the C.T. (See Drawing #8).
Section 4.1.12 Mast-Mounted Current Transformers Shall Not Be Allowed
Section 4.1.13 Outdoor Installation Locations
The meter device shall normally be mounted on an outdoor building wall, a remote pedestal, or a service pole. The meter enclosure or socket, subject to meter location policy, should be located as close as practical to the C.T.s. Enclosures shall not be located in carports, breezeways, porches, or such locations where subsequent addition, rewiring, or remodeling could enclose the enclosure. An enclosure installed in an alley or driveway must be recessed in the wall or protected adequately to prevent damage from vehicular traffic.
Section 4.1.14 Metering Not on District Equipment
Metering, except current transformers, shall not be mounted on or in District equipment except on service poles if approved in advance. All pole-mounted meter equipment shall be grounded with a #6 copper ground wire to a ground at the meter location. (See Drawings #7 and 8).
Section 4.2 Service Ampacity Larger Than 800 Amperes
Section 4.2.1 Switchgear C.T.
For services with ampacity greater than 800 A, the C.T. enclosures shall be part of the Customer service panels or switchgear. The District should be consulted for review of compartment size and service prior to purchasing and installing equipment. The C.T. space shall have bus bars through the C.T.s that are removable from within the C.T. compartment space. The C.T.s shall be furnished and installed by the District. Cables must be landed on hardware independently supported from the bus link through C.T. window. Cables shall not be brought through the C.T. window. Customer or Contractor shall terminate all conductors with 2-hole connectors and bolt to the current transformer landing pad bus bars. (See Drawing #29A and 29B).
Section 4.2.2 Enclosures To Be Accessible
Enclosures shall not be installed on ceilings. If the enclosure is installed on a balcony or platform, it must be available by a permanent stairway and be surrounded by a railing, both of which conform to OSHA requirement.
Section 4.2.3 C.TS Readily Accessible
On switchboards, the instrument transformers shall be installed in such a manner as to be readily accessible after all bussing is in place. Installation plans regarding size of cubicle and placement of equipment shall be approved by the District before switchboard manufacturing. Neutral connections for metering shall be readily accessible and sealable. If CT’s are in enclosed area including, buildings, fenced areas etc. The customer shall be responsible for purchasing a lock box labeled for the District use only. The lock box will contain a key for entry to enclosed area. The District must pre-approve any substitutions for the lock box.
Section 4.2.4 Unmetered Conductor Compartments Sealed
All sections of the switchgear that contain unmetered conductors shall have provisions for sealing compartment doors or covers.
Section 4.2.5 Meter Base & Test Switches
Meter base and bypass switches cannot be integral to switchgear equipment. Preference is for mounting on side of CT cabinet (See Drawing 29B). The district provides meter CT wiring and test switches. Contractor provides and installs meter base, and conduit
Section 4.3 Primary Voltage Meter Installations – Over 600 V
Section 4.3.1 Metering Location Approval
Primary service is metered with the instrument transformer(s) located outdoors and will be either pole-mounted or pad-mounted. The location of all instrument transformer metering installations must be approved by the District in advance of any work by the Customer or Customer’s contractor. The primary metering shall be located at the interface between District facilities and the Customer's facilities.
Section 4.3.2 District Provides, Installs, Maintains, & Owns Metering and Associated Equipment
At customer expense, the District will provide, install, maintain, and own all equipment associated with primary metering up to the load side of the current transformer(s) on all pole or pad-mounted installations
Section 4.3.3 Customer Provides Switches, etc.
Customer provides all necessary– primary wiring, switches, fusing or other overcurrent protection, lightning arresters, grounding and etc., from the load side of the current transformer to the Customer’s service equipment.
Section 4.3.4 Customer’s Wiring Connected by District
The District will connect Customer’s wiring to District primary voltage supply conductors and instrument transformers.
Section 4.3.5 Pole Mounted Primary Metering
Pole mounted primary metering will be mounted on a District owned pole.
Section 4.3.6 Pad Mounted Metering Enclosure
At Customer expense, the District will provide, install, own and maintain padmounted metering enclosures for underground installations.