ADE9078ACPZ datasheet(56/108 Pages) AD

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Data Sheet

ADE9078

Rev. 0 | Page 55 of 107

KEY FEATURES

FLEXIBLE WAVEFORM BUFFER WITH

RESAMPLING

An integrated flexible waveform buffer stores samples at a fixed

data rate or a sampling rate that varies based on the line frequency

to ensure 64 points per line cycle. These two options make it

easy to implement harmonic analysis in an external processor

according to IEC 61000-4-7. There is a choice of data rate for

the fixed data rate samples: 4 kSPS or 16 kSPS (see the

Waveform Buffer section for more details).

MULTIPOINT PHASE/GAIN CALIBRATION

To provide more accurate measurements when using current

transformers, the ADE9078 provides a multipoint gain and

phase calibration option. If selected, the user can enter unique

gain and phase calibrations for up to five regions of CT

operation. Use the current rms (IRMS) value to select the

current region of operation and to determine which gain and

phase calibration to apply (see the Multipoint Gain and Phase

Calibration section for more details).

RMS OF SUM OF INSTANTANEOUS CURRENTS

MEASUREMENT

The ADE9078 offers an rms measurement of the sum of instanta-

neous currents. Use this measurement to estimate the neutral

current rms if a neutral current sensor is not available. If a neutral

current sensor is used, the rms of the sum of instantaneous

currents can include IA + IB + IC ± IN. Ideally, IA + IB + IC ±

IN = 0. The rms of the sum of instantaneous currents is compared

to a user configured threshold. If it is greater than the threshold,

a mismatch interrupt is generated. This mismatch indication

can help detect earth currents or tamper, which is a safety

hazard (see the Neutral Current RMS, RMS of Sum of

Instantaneous Currents section for more details).

TAMPER MODES

Two power modes are provided to enable detection of meter

tampering: PSM2 uses a low power comparator to compare

current channels to a threshold and indicates whether it is

exceeded on the IRQ0 and IRQ1 outputs; and PSM1 enables

fast measurement of current and voltage rms, active power, and

VAR during a tamper. The PM0 and PM1 pins control which

power supply mode is selected: PSM0 (normal mode), PSM1

(tamper measurement mode), PSM2 (tamper detection mode),

or PSM3 (idle). The user application manages the PM0 and

PM1 pins to put the ADE9078 in PSM1 or PSM2 modes for the

required time to perform the measurement or detection. Then,

the user application changes PM0 and PM1 to put the ADE9078

in PSM3, idle mode, until the cycle must begin again—usually

once per minute (see the Power Modes section for more details).

POWER FACTOR

The power factor (PF) is calculated for each phase and is updated at

the user configured power update rate, which can be up to 1 sec.

PF is the total active power divided by the total apparent power. To

determine the quadrant, use the sign in the reactive power register

(see the Power Factor section for more details).

ZERO-CROSSING TIMEOUT DETECTION

Zero-crossing timeout detection is provided on each phase

voltage to indicate if the phase voltage has been low for a user

configured time period. An interrupt is generated if this event

occurs (see the Zero-Crossing Timeout section for more details).

LINE PERIOD MEASUREMENT

The ADE9078 offers a highly accurate line period measurement

that provides 0.001 Hz resolution. It is possible to measure the

line period on all three phases as well as a combined signal that

reflects the line period, regardless of if there is one or many

phases present (see the Line Period Calculation section for

more details).

ANGLE MEASUREMENT

Voltage to voltage, voltage to current, and current to current

angles are measured simultaneously with 0.036° resolution at

50 Hz. These measurements allow fundamental power factor

calculations and checks of the balance of the system (see the Angle

Measurement section for more details).

PHASE SEQUENCE ERROR DETECTION

Voltage channel zero crossings are monitored to indicate if a

phase sequence error occurs in both 3-phase, 4-wire (wye), and

3-wire (delta) connections (see the Phase Sequence Error Detection

section for more details).

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