GE Multilin EPM 6010, Инструкция по эксплуатации

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EPM 6010 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–1
EPM 6010 Multi-function Power
Metering System
Chapter 1: Three-Phase Power
Measurement
Digital Energy
Three-Phase Power Measurement
This introduction to three-phase power and power measurement is intended to provide
only a brief overview of the subject. The professional meter engineer or meter technician
should refer to more advanced documents such as the
EEI Handbook for Electricity
Metering and the application standards for more in-depth and technical coverage of the
subject.
1.1 Three-Phase System Configurations
Three-phase power is most commonly used in situations where large amounts of power
will be used because it is a more effective way to transmit the power and because it
provides a smoother delivery of power to the end load. There are two commonly used
connections for three-phase power, a wye connection or a delta connection. Each
connection has several different manifestations in actual use.
When attempting to determine the type of connection in use, it is a good practice to follow
the circuit back to the transformer that is serving the circuit. It is often not possible to
conclusively determine the correct circuit connection simply by counting the wires in the
service or checking voltages. Checking the transformer connection will provide conclusive
evidence of the circuit connection and the relationships between the phase voltages and
ground.
1.1.1 Wye Connection
The wye connection is so called because when you look at the phase relationships and the
winding relationships between the phases it looks like a wye (Y). Fig. 1.1 depicts the winding
relationships for a wye-connected service. In a wye service the neutral (or center point of
the wye) is typically grounded. This leads to common voltages of 208/120 and 480/277
(where the first number represents the phase-to-phase voltage and the second number
represents the phase-to-ground voltage).