METER INSTALLATION

previous ELECTRICAL METERING COMPONENTS

General Information: Before starting any work, the person in charge should assemble the entire crew for a job briefing. The job briefing should include an outline of the following items:

• The work to be done.
• Each crew member’s part in the job.
• The hazards known or anticipated during the task.
• Safety precautions to enforce while working.

If during the course of the work, changes in the plan become necessary, members of the crew who are affected must be called together and the changes explained.

1.1 Prior to Installation: Before installation of any equipment, the person in charge should identify all the circuits present. Conductors should be identified in terms of circuit and voltage, both at the point where work is to be done and at all switching and grounding points involved. Prior to installation of metering equipment, the supervisor of the building, or area of the building receiving its electrical supply from the metering point, should be advised of the installation. Barricades or barriers should be installed to prevent unauthorized entry into the area near the meter installation.

1.2 Portable Meters: To collect reliable data while performing an electrical energy survey, the proper meter for the job must be obtained. The following list of equipment parameters should be considered:

• Maximum voltage rating.
• Maximum load current (in amperes).
• Accuracy.
• Number of simultaneous demand values to be recorded.
• Power factor ranges.
• Full-scale ranges.
• Temperature working limits.
• Input power requirements.
• Type of meter enclosure.
• Weight.
• Overload protection.

1.2.1 Connecting the Meter: The items listed below are supplemental to manufacturers’ instructions and are provided to assist in safer and more accurate meter operation.

• Make only one connection at a time. Work on only one conductor or point at a time.
• Check all selectable meter settings to confirm configurations for monitoring desired parameters.
• Check zero for all parameters.
• Observe polarity of all meter connections.
• Connect additional ground; use #12 copper wire.
• Reset all counters, integrators, and totalizers.
• Some meters require warmup time. Allow meter to acclimate to conditions at the test site.
• Replace all protective covers when setup is complete.

The following items, coupled with the recommended safety equipment (as shown in the safety summary), assist in successful completion of electrical power surveys using a PSR. The required quantities of items listed depend on the number of personnel performing electrical power surveys. Ample quantities of the following items should be kept in good condition and readily available.

• Barriers and warning signs.
• Live-line and switch tags.
• Padlocks and locks.
• One-line diagram of building.
• Insulated flashlight.
• Clamp-on voltammeter and ohmmeter.
• Approved three conductor extension cord with grounding plug.
• Electrical insulating tape.
• Light meter.

1.3 Permanent Meters: The more common types of permanent meters include the S-type mounted with a socket and the A-type which is hard wired in its permanent position. These meter types are designed for original installation in new buildings or as retrofit equipment when conditions warrant monitoring an in-place electrical service. In most cases , electrical service must be interrupted to install or remove a meter.

1.3.1 Socket-Connected S-Type Meters: To install the S-type meter, perform the following procedures:

• Meter should be installed plumb and in a location that is free of heavy vibration.
• Make sure that meter socket is mounted securely in place and in a position that the rotor shaft will be vertical when meter is mounted.
• TO ground meter frame and surge protectors (if present), good contact between ground straps and socket rim must be ensured. To ensure good ground, scrape off any paint between straps and socket rim at points of contact before fastening them together.
• Make connections to socket terminals per manufacturer’s instructions. For connections of pulse initiators, consult manufacturer’s instructions for the particular type of device being operated.
• Plug meter into socket. Make sure meter terminal blades engage with socket jaws. To ensure connection of meter to its load circuit before line voltage is applied, always insert meter load (bottom) terminal blades into socket jaws first; when removing, withdraw them last.
• Push meter into place so that the base fits tightly against socket rim. If sealing rim is used, place it around adjoining meter cover and socket rim. Position rim so that clamp is at bottom.
• Seal or latch rim as required.
• For connections of pulse initiators, refer to manufacturer’s instructions for particular type of end device being operated by the pulse initiator.

1.3.2 Bottom-Connected A-Type Meters: These meters have mounting and terminal chamber dimensions that conform to industry standards. Therefore, mounts for bottom-connected A-type meters are interchangeable with all brands of A-type meters. To install an A-type meter, proceed as follows:

• Locate mounting holes in mounting base of meter.
• Obtain necessary type and size mounting screws suggested by meter manufacturer.
• Mount meter base in desired position.
• Meter base should be grounded. Use number 12 AWG copper wire for grounding purposes. Complete grounding process before external connections are made to meter.
• Make external connections to meter as shown in manufacturer’s instructions. The connections should be made by working from right to left. This ensures complete connection of meter to its LOAD circuit before LINE voltage is applied. Disconnection of meter should be made in reverse order.
• For connections of pulse initiators, refer to manufacturer’s instructions for particular type of end device being operated by the pulse initiator.
  

COMMON ELECTRICITY METERING PROBLEMS: Problems often encountered in the field while metering electricity fall into four categories: wrong meter, meter incorrectly wired, multipliers not calculated correctly, or the meter is not calibrated.

1. Wrong Meter: This problem occurs when the meter is incorrectly specified for the circuit. A common example of this is when a two stator meter is specified for a four wire wye circuit. The meter is often wired as if the circuit is a delta circuit. However, if the phases are even minimally unbalanced, the current flowing through the neutral wire will not be metered and the readings inaccurate. SOLUTION: Consult the manufacturers literature and specify the proper meter for the circuit.

2. Incorrect Wiring: It is estimated that between 5 to 10% of the electricity meters on navy bases are incorrectly wired. There are several ways the wiring can be wrong.

2.1 Current leads, potential leads , or instrument transformers could be reversed or out of rotation or phase. The phase angle between the current and the voltage for each phase to be wrong, resulting in erroneous readings by the meter. SOLUTION: Ensure meter IS wired correctly. Determine the nature of the load being metered and estimate its power factor. Then use a power factor meter on the incoming potential and current wires to determine if the meter is reading the estimated power factor.

2.2 Blown Potential Fuses: If fuses protecting potential transformers (PTs) are blown, the meter could be missing one or more phases of the load and running at 1/3 or 2/3 of normal speed. SOLUTION: Ensure that fuses for PTs are not blown. On most panel mounted meters, each PT circuit has a small light that, when lit, indicates that the circuit is operating properly.

3. Incorrect Multipliers: The multipliers have been incorrectly calculated, resulting in the register readings being multiplied by the wrong numbers. This often occurs when meters have been switched to a new location with different sized CTs or PTs, or when a meter has been repaired and the register changed. SOLUTION: Ensure that the values for the CT and PT ratios, K_h, R_r, and G_r are correct. Recalculate K_r, the register multiplier, to ensure it is correct.

4. Uncalibrated Meter: Meters built by major manufacturers are designed to run several years before calibration. However, depending on their use, navy meters should be calibrated from once per year to once every 5 years. SOLUTION: Field calibration of permanent meters can be performed by installing a portable meter In series with the permanent meter, timing the revolutions of the rotor, and comparing the kW demand of the permanent meter to that of the portable meter. This method should be accurate to within 5-10% . More accurate calibration requires the removal of the meter from the circuit to use a calibration stand.

next ELECTRICAL ENERGY SURVEYS