ADE7156_15 datasheet(54/152 Pages) AD

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ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/ADE7569

Rev. B | Page 54 of

152

FAULT DETECTION

The ADE7116/ADE7156/ADE7166/ADE7169 incorporate a

fault detection scheme that warns of fault conditions and allows

the part to continue accurate measurement during a fault event.

(This function is not available in the ADE7566/ ADE7569.) The

ADE7116/ADE7156/ADE7166/ADE7169 do this by continu-

ously monitoring both current inputs (IPA and IPB). For ease of

understanding, these currents are referred to as phase and

neutral (return) currents. A fault condition is defined when the

difference between IPA and IPB is greater than 6.25% of the active

channel. If a fault condition is detected and the inactive channel

is larger than the active channel, the ADE7116/ADE7156/

ADE7166/ADE7169 automatically switch current measurement to

the inactive channel. During a fault, the active, reactive, and

apparent power and the Irms are generated using the larger of the

two currents. On power-up, IPA is the current input selected for

active, reactive, and apparent power and Irms calculations.

To prevent a false alarm, averaging is done for the fault

detection, and a fault condition is detected approximately

1 second after the event. Fault detection is automatically

disabled when the voltage signal is less than 0.3% of the full-

scale input range. This eliminates false detection of a fault due

to noise at light loads.

Because the ADE7116/ADE7156/ADE7166/ADE7169 look for

a difference between the voltage signals on IPA and IPB, it is

important that both current transducers be closely matched.

Channel Selection Indication

The current channel selected for measurement is indicated by

Bit 7 (ICHANNEL) in the ACCMODE register (Address 0x0F).

When this bit is cleared, IPA is selected and, when it is set, IPB is

selected. The ADE7166/ADE7169 automatically switch from

one channel to the other and report the channel configuration

in the ACCMODE register (Address 0x0F).

The current channel selected for measurement can also be

forced. Setting the SEL_I_CH[1:0] bits in the CALMODE

both bits are cleared or set, the current channel used for

measurement is selected automatically based on the fault

detection.

Fault Indication

The ADE7116/ADE7156/ADE7166/ADE7169 provide an

indication of the part going in or out of a fault condition. The

new fault condition is indicated by the FAULTSIGN flag (Bit 5)

in the Interrupt Status 1 SFR (MIRQSTL, Address 0xDC).

When the FAULTSIGN bit (Bit 6) of the ACCMODE register

(Address 0x0F) is cleared, the FAULTSIGN flag in the Interrupt

Status 1 SFR (MIRQSTL, Address 0xDC) is set when the part is

entering a fault condition or a normal condition.

When the FAULTSIGN bit (Bit 5) is set in the Interrupt Enable

1 SFR (MIRQENL, Address 0xD9), and the FAULTSIGN flag

(Bit 5) in the Interrupt Status 1 SFR (MIRQSTL, Address 0xDC)

is set, the 8052 core has a pending ADE interrupt.

Fault with Active Input Greater Than Inactive Input

If IPA is the active current input (that is, being used for billing),

and the voltage signal on IPB (the inactive input) falls below

93.75% of IPA, and the FAULTSIGN bit (Bit 6) of the ACCMODE

in the Interrupt Status 1 SFR (MIRQSTL, Address 0xDC) is set.

Both analog inputs are filtered and averaged to prevent false

triggering of this logic output. As a consequence of the filtering,

there is a time delay of approximately 3 seconds on the logic

output after the fault event. The FAULTSIGN flag is indepen-

dent of any activity. Because IPA is the active input and it is still

greater than IPB, billing is maintained on IPA; that is, no swap to

the IPB input occurs. IPA remains the active input.

ADE7156 Datasheet(PDF) 54 Page - Analog Devices

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