PS-E-08-E—Provisional specifications for the installation and use of 2-element electricity meters

Table of contents

1.0 Scope

These specifications apply to 2-element electricity meters used to measure volt-ampere (VA) or volt-ampere hour VA·h on 3-phase 4-wire installations which have been installed using a delta connection at the terminal (test) block.

2.0 Background

Measurement Canada has never allowed the use of a 2-element, rectithermal VA meter in the above configuration, as the resulting registration is too high by approximately 25%. In 1999, at the pre-Canadian Forum on Trade Measurement, Measurement Canada raised concerns that 2-element, electronic meters, programmed to measure arithmetic apparent power (VA) used in a similar configuration, will measure VA with errors comparable to those found with the electro-mechanical equivalent.

3.0 Authority

These specifications are issued under the authority of section 12(2) of the Electricity and Gas Inspection Regulations.

4.0 Terminology

Delta connection

The wiring configuration of a 3-phase 4-wire metering installation which sums the secondaries of the current instrument transformers. The configuration is made in such a way to add the Ib current to the Ia and Ic secondaries of the instrument transformers. The resultant current measured by the meter is Iab in one element and Icb in the other element.

Test Block

The wiring termination point for the secondaries of the voltage and current transformers. It is the connection point where measurement test equipment can be connected for inspection purposes.

5.0 Metering configuration

5.1 General

Standard drawing number 3409 below shows the acceptable configuration for the use of a 2-element meter to measure a 3-phase 4-wire electrical metering installation using voltage and current instrument transformers.

Figure 1: Standard Drawing 3409

This is a diagram of a 3-phase, 2 element transformer-type meter, 4-wire circuit (3409) (the long description is located below the image)
Full description — Figure 1: Standard Drawing 3409

Connection of a transformer-type, 2-element, vertical, A-base, electricity meter in a 3-phase, 4-wire, Wye-connected circuit with two voltage transformers and three current transformers:

  1. The four circuit conductors are referred to as Phase A, Phase B, Phase C and Neutral.
  2. The meter contains two voltage coils, two current coils and an eight position terminal block. Internal meter connections are as follows:
    • the upper voltage coil is connected to terminal block positions three and six
    • the lower voltage coil is connected to terminal block positions one and eight
    • the upper current coil is connected to terminal block positions four and five
    • the lower current coil is connected to terminal block positions two and seven.
  3. A test block is connected in the secondary circuits between the transformers and the meter. The test block positions are referenced from left-to-right as numbers one through nine.
  4. The Phase A to Neutral voltage transformer is connected as follows:
    • the polarity marked primary terminal is connected to the Phase A service conductor on the supply side of the current transformer
    • the unmarked primary terminal is connected to the neutral service conductor
    • a red wire is connected from the polarity marked secondary terminal to the bottom of test block position one and continues from the top of test block position one to position one of the meter terminal block
    • a yellow or white wire is connected from the unmarked secondary terminal to the bottom of test block position two and continues from the top of test block position two to positions six and eight of the meter terminal block.
  5. The Phase C to Neutral voltage transformer is connected as follows:
    • the polarity marked primary terminal is connected to the Phase C service conductor on the supply side of the current transformer
    • the unmarked primary terminal is connected to the neutral service conductor
    • a blue wire is connected from the polarity marked secondary terminal to the bottom of test block position three and continues from the top of test block position three to position three of the meter terminal block
    • a white wire is connected from the unmarked secondary terminal to the bottom of test block position two.
  6. The Phase A current transformer is connected as follows:
    • the polarity marked primary terminal is on the supply side of the Phase A service conductor
    • the unmarked primary terminal is on the load side of the Phase A service conductor
    • a red and white wire is connected from the polarity marked secondary terminal to the bottom of test block position four and continues from the top of test block position four to position two of the meter terminal block
    • a red and black wire is connected from the unmarked secondary terminal to the bottom of test block position five and continues from the top of test block position five to position seven of the meter terminal block.
  7. The Phase B current transformer is connected as follows:
    • the polarity marked primary terminal is on the supply side of the Phase B service conductor
    • the unmarked primary terminal is on the load side of the Phase B service conductor
    • a yellow and white wire is connected from the polarity marked secondary terminal to the bottom of test block position six and continues from the top of test block position six to the bottom of test block position five
    • a yellow and black wire is connected from the unmarked secondary terminal to the bottom of test block position seven and continues from the top of test block position seven to the top of test block position eight.
  8. The Phase C current transformer is connected as follows:
    • the polarity marked primary terminal is on the supply side of the Phase C service conductor
    • the unmarked primary terminal is on the load side of the Phase C service conductor
    • a blue and white wire is connected from the polarity marked secondary terminal to the bottom of test block position six and continues from the top of test block position six to position four of the meter terminal block
    • a blue and black wire is connected from the unmarked secondary terminal to the bottom of test block position seven and continues from the top of test block position seven to position five of the meter terminal block.
  9. A green wire is connected from the bottom of the test block at positions 2, 4 and 9 to a ground point.
  10. The meter phasors for this configuration, under unity power factor conditions and counter-clockwise phase rotation, are as follows:
    • the voltage between Phase C and Neutral leads the voltage between Phase A and Neutral by 120 °
    • the current between phases A and B leads the voltage between Phase A and Neutral by 30 °
    • the current between phases C and B lags the voltage between Phase C and Neutral by 30 °.

6.0 Electrical requirements

For 2-element meters used in the installation configuration shown in section 5 it shall be assured that:

  1. in the case of an electro-mechanical demand meter it does not provide full rectification of the voltage and current inputs,
  2. in the case of an electronic demand meter it is of the type that calculates VA using vectorial VA calculations and not arithmetic VA calculations
  3. the paralleled current flowing in each current circuit never exceeds the maximum current rating of the meter.
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